共查询到20条相似文献，搜索用时 265 毫秒
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选择 1 5只性成熟健康雄性小白鼠 ,本交后第二天随机分为 3组 ,每组 5只。每Ⅰ、Ⅱ组腹腔注射GnRH类似物 4ug/只 ,Ⅱ组连续 4天肌注丙酸睾丸酮 0 .0 5mg/只日 ,Ⅲ组不用药作对照组 ,以研究GnRH类似物对附睾精子成熟的影响。结果表明 :睾丸重各组间差异不显著 ( p >0 .0 5 )。Ⅰ组畸形率高于Ⅱ、Ⅲ组 1 2 .4% ,顶体完整率明显下降 ,均呈极显著差异(p <0 .0 1 ) ,精子活率出现低于两组的趋势。三组间的顶体破损率以Ⅰ组最高为 2 2 .32 % ( p <0 .0 1 )。Ⅱ组的顶体完整率显著高于Ⅲ组 ( p <0 .0 1 )。综合分析认为 ,高剂量GnRH类似物破坏精子在附睾中的成熟过程 ,外源雄激素对其有颉抗作用 相似文献
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陈晓春 《河北北方学院学报(医学版)》2003,20(3):3-6
目的 :细胞内钙超载与氧自由基生成增多是脑缺血再灌注损伤中的两个重要因素。本实验通过检测正常大鼠脑组织和脑缺血再灌后脑区的超氧化物歧化酶活性、丙二醛含量、脑含水量、脑组织钙离子含量和光、电镜的观察 ,观察黄芪对大鼠脑缺血再灌注脑组织的保护作用。方法 :本实验利用Wistar大鼠 36只 ,随机分为正常对照组、模型组和黄芪组 ,每组 12只大鼠。模型组和黄芪组均用动脉栓线法自右侧颈总动脉插入阻塞栓线 ,伸入大脑前动脉起始部制成局灶性脑缺血再灌注模型。黄芪组梗塞和再灌注前 5min均经左侧颈外静脉给药两次 ,而模型组代之以生理盐水。梗塞 1.5h后拔线再灌注 ,再灌注 1.5h后断头取脑。分别测量各生化指标和制作光、电镜切片。结果 :模型组丙二醛含量、脑钙含量、脑水分含量明显高于正常对照组 (P <0 .0 1) ,而超氧化物歧化酶活性却低于正常对照组 (P <0 .0 1)。黄芪组脑钙含量、脑水分含水量与模型组无显著性差异 (P <0 .0 5 ) ,超氧化物歧化酶活性明显高于模型组 (P <0 .0 1) ,丙二醛含量明显低于模型组 (P <0 .0 1)。光镜观察 :模型组神经元细胞周围狭窄状亮区较正常对照组明显增宽 (P <0 .0 1) ,黄芪组与模型组相比无显著性差异 (P <0 .0 5 )。电镜观察 :模型组与正常对照组相比核膜双层结构 相似文献
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程艳莉 《连云港职业技术学院学报》2004,17(4):24-26
引进有孔的单位圆盘E0=z∈C:0<｜z｜<1内的解析函数类∑p.利用线性算子Dn+p,考察了亚纯p叶函数的新子类Tn+p-1(α)的一些性质,分别研究了其包含关系及类中函数的积分变换性质. 相似文献
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基于脉冲耦合神经网络,提出了一种有效的脉冲噪声图像滤波算法。利用PCNN相似群神经元同步发放脉冲的特性检测噪声点,并利用中值滤波对噪声点进行滤波。仿真表明,该方法对不同强度的噪声图像均体现了较好的滤波性能,在去噪效果和运行效率上同其它方法相比具有明显优势。 相似文献
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<正>以下是2011年辽宁的一道高考题.已知函数f(x)=lnx-ax2+(2-a)x.(1)(2)略;(3)若函数y=f(x)的图象与x轴交于A、B两点,线段AB中点的横坐标为x0,证明:f'(x0)<0.本题考察了形如f(x)=plnx+mx2+nx+c(p,m,n,c∈R)的导数题型.对导数问题,高考重点考查两方面内容:(1)函数的单调 相似文献
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为了研究碘对正常人外周血淋巴细胞微核率的影响 ,我们用不同浓度的碘化钾溶液处理培养中的淋巴细胞 ,观察其微核率的变化 ,并用x2 检验方法作显著性检验。结果显示 ,培养液中碘含量在 1 0ug时 ,微核率显著低于对照组 (p <0 .0 5) ,说明适量的碘可以降低微核率 ;培养液中碘含量在 1 0 0ug以上时 ,微核率显著高于对照组 (p <0 .0 5) ,说明过量的碘对染色体有程度不同的损伤作用 相似文献
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第 1章 函数1 填空题1)函数 y=4 -xln(x- 2 ) 的定义域是 .2 )设f(x) =x2 +2ex x ≤ 00 相似文献
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第1章 函数1 填空题1)函数y=4 -xln(x - 2 ) 的定义域是.2 )设f(x) =x2 +2ex x ≤00 相似文献
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提出一种结合几何谱减法的基于人耳听觉掩蔽效应的算法．通过仿真证明,该算法与一般的基于人耳听觉掩蔽效应的算法相比,能更好地减少音乐噪声,提高信噪比．在去噪的同时,减小了纯净语音的畸变,达到良好的效果． 相似文献
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Continuous noise facilitates acoustic startle reflexes in the rat. Rats were exposed to noise for 23 h (Experiment 1) or to 23 h of startle eliciting stimuli at the rate of 1/min (Experiment 2). Facilitation was reduced following habituation in Experiment 2, but was unaffected by prolonged noise exposure in Experiment 1. Reflex inhibition produced by a brief noise was not altered by habituation. Prior experiments show that increases in intensity of continuous noise engage two disparate processes which affect the acoustic startle reflex, one facilitatory (arousal) and one inhibitory (masking). The present data reveal that arousal is not diminished by prolonged noise exposure. The loss of facilitation following reflex habituation may be attributed to its increased susceptibility to masking, or to a direct effect of stimulus repetition on the arousal process normally associated with the noise background. 相似文献
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应用HRP进行追踪法在光镜水平研究了猫丘脑中央外侧核向前乙状回、前上薛氏回和中上薛氏回前端投射的神经元的形态与分布。结果表明:中央外侧核向大脑皮质的投射为同侧投射;中央外侧核向前乙状回投射的神经元集中于核的尾段,少部分位于中段,偏内侧分布,大、中、小型投射神经元均有,以中、小型为主;中央外侧核向前上薛氏回和中上薛氏回前端投射的神经元集中干中段,略向前后延伸,分布于嘴段和部分尾段。整个投射细胞群偏外侧分布,以中小型为主,少部分大型投射神经元位于最外侧。大型标记的投射神经元主要为圆形,卵圆形和多边型,中、小型标记的投射神经元呈各种形态。 相似文献
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在声学中,前掩蔽是指前一个声音作用时对后一个声音的辨别和感受造成的妨碍.它对人类和动物的声音感知和定位具有重要意义.前掩蔽效应受多种刺激参数的影响和调节.目前人们认为前掩蔽是外周的非线性和中枢水平线性整合的结果,其中神经抑制在前掩蔽的产生中起着重要作用,这种作用主要是γ-氨基丁酸能介导的.此外,非神经性原因等也起着一定的作用. 相似文献
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D. Papadopoulou P. Malliou N. Kofotolis S.P. Vlachopoulos E. Kellis 《International Journal of Disability, Development & Education》2017,64(1):76-87
The purpose of this study was to examine parental perceptions about Health Related Quality of Life (HRQoL) of typical education and special education students in Greece. The Pediatric Quality of Life Inventory (PedsQL) was administered to the parents of 251 children from typical schools, 46 students attending integration classes (IC) within a typical school and 97 students attending special education (segregated) schools. A two-way analysis of covariance indicated that, compared to their typically developing peers, children attending special education schools and IC were reported by their parents to have lower PedsQL scores. Compared to children attending special education schools, children attending IC showed no differences in all PedsQL domains but the emotional domain score (p < .05). Based on parents’ responses, further improvements in special education settings and environments in the Greek educational system might be necessary to improve the HRQOL of students with disabilities. 相似文献
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传统机器翻译系统的研究正在经历雪线困境(就是指机器翻译系统很难超越的译准率极限———70%).HNC理论针对传统机器翻译方法的弊端进行了深刻的反思,为突破雪线困境提出了一种全新的思路.语义块主辅变换是HNC机器翻译引擎中六个"过渡处理模块"的一部分.语义块主辅变换研究对于提高机器翻译系统的性能具有重要意义.本文简要介绍了HNC的机器翻译观,重点阐述语义块主辅变换的原理,并通过一个示例说明了语义块主辅变换研究如何来提高机器翻译系统的性能. 相似文献
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Wai S. Tse Lai Y. A. Choi Wing S. Tang 《British journal of educational technology : journal of the Council for Educational Technology》2019,50(1):385-398
Video-based flipped class instruction can strengthen the learning motivation of students. The effectiveness of flipped class instruction on teaching effectiveness and subject satisfaction has been evaluated previously. The present study aims to examine the impact of two aspects of subject reading motivation. A total of 100 secondary school students were recruited from 4 classes of 25 students (ie, video-based flipped Mathematics class, traditional Mathematics class, video-based flipped Liberal Studies (LS) class and traditional LS class) in two local secondary schools. The same teachers taught both the traditional and video-based flipped classes in their subject. The students filled in questionnaires which measured: motivation for general reading; motivation for subject reading; academic subject satisfaction and perceived teaching effectiveness of the teachers. Analysis of covariance controlling for motivation for general reading revealed that students in the flipped classes reported significantly lower motivation for subject reading including reading curiosity, reading importance and reading compliance (t (1,98) = 10.52, p < 0.001; t (1,98) = 7.68, p < 0.001; t (1,98) = 20.39, p < 0.001, respectively). However, students in the flipped classes reported significantly higher satisfaction and teaching effectiveness than those in the traditional classes (t (1,98) = −15.61. p < 0.001; t (1,98) = −11.98, p <0.001, respectively). A partial correlation controlling for motivation for general reading indicated that motivation for subject reading was negatively associated with academic subject satisfaction and perceived teaching effectiveness of teachers (rs ranged from −0.51 to −0.62, p < 0.001). Video-based flipped class instruction was not only related to increased academic subject satisfaction and teaching effectiveness but also associated with lower motivation for subject reading. These findings suggest that video-based flipped class instruction had limited capability to strengthen the learning motivation of students. 相似文献
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OFDM电力线通信系统抗噪性能分析 总被引：1，自引：0，他引：1
基于电力线通信（ PLC ）系统的实测噪声,分析OFDM系统的电力线通信系统性能。通过Matlab和嵌入数字信号处理（ DSP ）系统进行虚拟发送和接收,在传输信道中加入噪声（加性白高斯噪声、电力线有色背景噪声等）仿真操作来干扰发送信号,以达到系统性能分析的目的。同时,在OFDM系统中分析卷积编码的前向纠错（ FEC ）的应用。结果表明,低阶调制可使系统性能改善,前向纠错技术通过解码可以自动纠正传输误码,降低接收信号的误码率（ BER）。 相似文献
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In three experiments, groups of albino rats received one strictly simultaneous pairing of a 4-sec auditory conditioned stimulus (CS) and a 4-sec 1-mA shock unconditioned stimulus (US). Other groups received a backward pairing, in which the US began before the CS, or a forward pairing, in which the CS began before the US. Control groups received only the US or received both the CS and the US but widely separated in time. Later, the CS was presented while the rats licked a drinking tube for water, and CS-elicited suppression of licking was taken as an index of the Pavlovian conditioned response (CR). It was found that groups receiving a single forward or a single simultaneous pairing suppressed more than groups that had received a backward pairing; and the backward groups, in turn, suppressed more than the control groups. It appears, then, that excitatory fear conditioning, as reflected in conditioned suppression of licking in rats, can be produced in a single trial by both backward and simultaneous conditioning procedures. 相似文献
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