首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1782篇
  免费   18篇
  国内免费   11篇
教育   1107篇
科学研究   124篇
各国文化   8篇
体育   414篇
综合类   1篇
文化理论   29篇
信息传播   128篇
  2023年   13篇
  2022年   34篇
  2021年   45篇
  2020年   46篇
  2019年   68篇
  2018年   101篇
  2017年   91篇
  2016年   94篇
  2015年   46篇
  2014年   64篇
  2013年   216篇
  2012年   83篇
  2011年   75篇
  2010年   77篇
  2009年   64篇
  2008年   62篇
  2007年   59篇
  2006年   71篇
  2005年   55篇
  2004年   45篇
  2003年   44篇
  2002年   39篇
  2001年   35篇
  2000年   21篇
  1999年   22篇
  1998年   24篇
  1997年   17篇
  1996年   10篇
  1995年   10篇
  1994年   8篇
  1993年   8篇
  1992年   12篇
  1991年   8篇
  1990年   14篇
  1989年   7篇
  1988年   7篇
  1987年   5篇
  1986年   8篇
  1985年   5篇
  1984年   11篇
  1983年   6篇
  1982年   4篇
  1981年   5篇
  1980年   5篇
  1979年   9篇
  1978年   5篇
  1977年   4篇
  1975年   11篇
  1974年   6篇
  1968年   3篇
排序方式: 共有1811条查询结果,搜索用时 15 毫秒
101.
The young field of neuroeconomics converges around behavioral deviations from the model of the human being as Homo economicus, a rational actor who calculates his choices to maximize his individual satisfaction. In a historical moment characterized by economic, health, and environmental crises, policymakers have become increasingly concerned about a particular deviation for which neuroeconomics offers a biological explanation: Why do humans value the present at the expense of the future? There is contentious debate within the field over how to model this tendency at the neural level. Should the brain be conceptualized as a unified decision-making apparatus, or as the site of conflict between an impetuous limbic system at perpetual odds with its deliberate and provident overseer in the prefrontal cortex? Scientific debates over choice-making in the brain, we argue, are also debates over how to define the constraints on human reason with which regulative strategies must contend. Drawing on ethnographic and archival research, we explore how the brain and its treatment of the future become the contested terrain for distinct visions of governmental intervention into problems of human choice-making.  相似文献   
102.
To prepare a biosynthetic module in an infochemical communication project, we designed a silicon/glass microreactor with anti-adsorption polyelectrolyte multilayer coating and immobilized alcohol acetyl transferase (atf), one of the key biosynthetic enzymes of the pheromone of Spodoptera littoralis, on agarose beads inside. The system reproduces the last step of the biosynthesis in which the precursor diene alcohol (Z,E)-9,11-tetradecadienol is transformed into the major component (Z,E)-9,11-tetradecadienyl acetate. The scope of this study was to analyze and implement a multilayer, anti-adsorption coating based on layer-by-layer deposition of polyethylenimine/dextransulfate sodium salt (PEI/DSS). The multilayers were composed of two PEI with molecular weights 750 and 1.2 kDa at pH 9.2 or 6.0. Growth, morphology, and stability of the layers were analyzed by ellipsometry and atomic force microscopy (AFM). The anti-adsorption functionality of the multilayer inside the microreactor was validated. The activity of His(6)-(atf) was measured by gas chromatography coupled to mass spectrometer (GC-MS).  相似文献   
103.
In this work a disposable, parallel microbioreactor (MBR) suitable for screening in batch or continuous mode is presented. The reactor consists of five parallel microchambers made of poly(dimethylsiloxane) bonded to a glass substrate. A grid structure is engraved on each chamber, allowing subsequent morphology imaging. Measurements are recorded over the entire cultivation period with constant parameters, namely, position and focus in the z-axis. The microdevice may be used for either parallel, uni- or multiparametric screening, and overcomes the drawback of gridless microwell plates which require expensive equipment such as an inverted microscope with an automatic stage. To validate the scalability from laboratory scale to microscale, and thus the cultivation protocol in the MBR, the germination of fungal spores (A. ochraceus) is evaluated for two different key magnitudes (pH and temperature) and compared to the results obtained from conventional laboratory scale systems (flasks and agar plates). Information on germination capacity with regard to interspecies' variability allows for optimization of industrial processes as optimal pH and temperature matched to the mesoscopic cultivation systems. The germination conditions therefore remain unaffected inside the MBR, while providing the following advantages: (i) dramatic reduction of medium consumption, (ii) submerged cultivation with constant oxygen supply, (iii) assured low cost and disposability, and (iv) possibility of a continuous cultivation mode.  相似文献   
104.
We examined differences in anthropometry and training between 64 Triple Iron ultra-triathletes competing over 11.4 km swimming, 540 km cycling, and 126.6 km running, and 71 Ironman triathletes competing over 3.8 km swimming, 180 km cycling, and 42.2 km running. The association of anthropometry and training with race time was investigated using multiple linear regression analysis. The Triple Iron ultra-triathletes were smaller (P < 0.05), had shorter limbs (P < 0.05), a higher body mass index (P < 0.05), and larger limb circumferences (P < 0.01) than the Ironman triathletes. The Triple Iron ultra-triathletes trained for more hours (P < 0.01) and covered more kilometres (P < 0.01), but speed in running during training was slower compared with the Ironman triathletes (P < 0.01). For Triple Iron ultra-triathletes, percent body fat (P = 0.022), training volume per week (P < 0.0001), and weekly kilometres in both cycling (P < 0.0001) and running (P < 0.0001) were related to race time. For Ironman triathletes, percent body fat (P < 0.0001), circumference of upper arm (P = 0.006), and speed in cycling training (P = 0.012) were associated with total race time. We conclude that both Triple Iron ultra-triathletes and Ironman triathletes appeared to profit from low body fat. Triple Iron ultra-triathletes relied more on training volume in cycling and running, whereas speed in cycling training was related to race time in Ironman triathletes.  相似文献   
105.

BISp-Informationen

BISp Informationen  相似文献   
106.

BISp-Informationen

Informationen des Bundesinstituts für Sportwissenschaft (BISp)  相似文献   
107.
108.
The vapor-liquid equilibrium(VLE) properties for the binary and ternary mixtures of CH4,C2H4 and isoC4H10 are of great importance in the recovery of ethylene from mixture containing CH4 and C2H4 with iso-C4H10 as solvent.Hence,Gibbs ensemble Monte Carlo(GEMC) simulations were used to estimate vapor-liquid equilibrium for the binary and ternary mixtures of CH4,C2H4 and iso-C4H10 with the united atom potential NERD model.The selected simulation conditions are based on the experiment in the literature.The results of this work were shown to be in satisfactory agreement with available experimental data and predictions of Peng-Robinson equation of state.The structure of simulated liquid phase is also characterized by radial distribution function(RDF),which contributes to further understanding of the VLE curve of these systems.RDF is not sensitive to the pressure and temperature range.With the increase of pressure or the decrease of temperature,the molecules tend to gather together.  相似文献   
109.
[目的/意义] 基于专利数据开展技术融合研究是技术融合研究的主要方式和热点方向,面向为技术融合后续研究工作开展提供参考和启发的目标,对国内外基于专利数据的技术融合研究现状进行较为全面的综述。[方法/过程] 将已有研究按研究内容划分为技术融合测度及预测方法研究、特定领域/多领域间/全领域的技术融合态势测度及趋势预测、技术融合的测度指标研究、影响技术融合的特征因素研究、基于技术融合视角进行技术机会发现以及技术融合与创新的关系研究六类,并对各类别取得的研究成果进行评述。[结果/结论] 基于专利数据开展技术融合研究已经取得一定的成果,但是仍旧存在测度依据不合理、预测方法缺乏验证、全领域研究关注度低的问题,这些问题可通过引入语义关系优化技术融合网络、采用图神经网络技术改进技术融合预测方法、完善全领域技术融合测度和预测方法来解决。  相似文献   
110.
Educational technology research and development - This study aims to evaluate the level of Turkish higher education graduates’ problem-solving skills (PSSs) in technology-rich environments...  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号