全文获取类型
| 收费全文 | 98篇 |
| 免费 | 2篇 |
| 国内免费 | 1篇 |
专业分类
| 教育 | 58篇 |
| 科学研究 | 24篇 |
| 各国文化 | 5篇 |
| 体育 | 4篇 |
| 文化理论 | 3篇 |
| 信息传播 | 7篇 |
出版年
| 2023年 | 2篇 |
| 2022年 | 2篇 |
| 2021年 | 10篇 |
| 2020年 | 1篇 |
| 2019年 | 6篇 |
| 2018年 | 5篇 |
| 2017年 | 9篇 |
| 2016年 | 5篇 |
| 2015年 | 5篇 |
| 2013年 | 13篇 |
| 2012年 | 1篇 |
| 2011年 | 2篇 |
| 2010年 | 3篇 |
| 2009年 | 3篇 |
| 2008年 | 5篇 |
| 2007年 | 3篇 |
| 2006年 | 5篇 |
| 2004年 | 3篇 |
| 2003年 | 3篇 |
| 2002年 | 1篇 |
| 2000年 | 1篇 |
| 1996年 | 1篇 |
| 1992年 | 1篇 |
| 1990年 | 1篇 |
| 1987年 | 2篇 |
| 1986年 | 1篇 |
| 1982年 | 1篇 |
| 1981年 | 1篇 |
| 1980年 | 1篇 |
| 1979年 | 1篇 |
| 1977年 | 2篇 |
| 1974年 | 1篇 |
排序方式： 共有101条查询结果，搜索用时 640 毫秒
21.
22.
Dehghani MH Mahvi AH Jahed GR Sheikhi R 《Journal of Zhejiang University. Science. B》2007,8(7):493-497
The objective of the investigation was to study the application of ultrasound reactor technology （USRT） as a disinfectant for reduction of fungi from sewage effluent. Fungi are carbon heterotrophs that require preformed organic compounds as carbon sources. USRT is an attractive means to improve water quality because of the system simplicity and no production of toxic by-products. An ultrasound reactor produces strong cavitation in aqueous solution causing shock waves and reactive free radicals by the violent collapse of the cavitation bubble. These effects should contribute to the physical disruption of microbial structures and inactivation of organisms. There was significant reduction in fungal growth, with decreased fungal growth with increasing USRT. In this study, ultrasound irradiation at a frequency of 42 kHz was used to expose suspensions of fungi to evaluate the disinfection efficacy of the ultrasound reactor. Also, this study showed that in this system more than 99% reduction of sewage fungi was achieved after 60 min. 相似文献
23.
E-Government and E-Government development project studies have been conducted in most industrialized societies, as well as in Iran. Due to their nature and structure, E-Government development projects have numerous political, social, and economic impacts on society. Given the incorporation of significant capital, human resources, information, and political commitments, these projects are considered quite vital to society. Following the systematic pre-implementation activities of E-Government development projects is critical for the success of such projects; ignoring such issues leads to various problems during E-Government project implementation. This research aims to explore and detect the success indicators for pre-implementation activities of E-Government development projects, evaluate the validity of these indicators, and investigate the indicators' status in the Fuel Smart Card Project. The researcher has also provided some suggestions on the successful implementation of E-Government development projects. 相似文献
24.
25.
Amir D. Aczel 《Science & Education》2004,13(7-8):675-687
26.
We consider text retrieval applications that assign query-specific relevance scores to documents drawn from particular collections.
Such applications represent a primary focus of the annual Text Retrieval Conference (TREC), where the participants compare
the empirical performance of different approaches. P(K), the proportion of the top K documents that are relevant, is a popular measure of retrieval effectiveness.
Participants in the TREC Very Large Corpus track have observed that when the target is a random sample from a collection,
P(K) is substantially smaller than when the target is the entire collection. Hawking and Robertson (2003) confirmed this finding
in a number of experimental settings. Hawking et al. (1999) posed as an open research question the cause of this phenomenon
and proposed five possible explanatory hypotheses. In this paper, we present a mathematical analysis that sheds some light
on these hypotheses and complements the experimental work of Hawking and Robertson (2003). We will also introduce C(L), contamination at L, the number of irrelevant documents amongst the top L relevant documents, and describe its properties.
Our analysis shows that while P(K) typically will increase with collection size, the phenomenon is not universal. That is, the asymptotic behavior of P(K) and C(L) depends on the score distributions and relative proportions of relevant and irrelevant documents in the collection.
While this article went to press, Yehuda Vardi passed away. We dedicate the paper to his memory. 相似文献
27.
28.
Implantable drug delivery devices are becoming attractive due to their abilities of targeted and controlled dose release. Currently, two important issues are functional lifetime and non-controlled drug diffusion. In this work, we present a drug delivery device combining an electrolytic pump and a thermo-responsive valve, which are both remotely controlled by an electromagnetic field (40.5 mT and 450 kHz). Our proposed device exhibits a novel operation mechanism for long-term therapeutic treatments using a solid drug in reservoir approach. Our device also prevents undesired drug liquid diffusions. When the electromagnetic field is on, the electrolysis-induced bubble drives the drug liquid towards the Poly (N-Isopropylacrylamide) (PNIPAM) valve that consists of PNIPAM and iron micro-particles. The heat generated by the iron micro-particles causes the PNIPAM to shrink, resulting in an open valve. When the electromagnetic field is turned off, the PNIPAM starts to swell. In the meantime, the bubbles are catalytically recombined into water, reducing the pressure inside the pumping chamber, which leads to the refilling of the fresh liquid from outside the device. A catalytic reformer is included, allowing more liquid refilling during the limited valve''s closing time. The amount of body liquid that refills the drug reservoir can further dissolve the solid drug, forming a reproducible drug solution for the next dose. By repeatedly turning on and off the electromagnetic field, the drug dose can be cyclically released, and the exit port of the device is effectively controlled. 相似文献
29.
Alexander A 《Isis; an international review devoted to the history of science and its cultural influences》2011,102(3):475-480
Up until the 1950s, the history of mathematics was an integral part of the history of science. To George Sarton and his contemporaries, mathematics was the rational skeleton that organized science and held it together, and its history was a fundamental component of the broader history of science. But when historians began focusing on the cultural roots of science rather than its rational structure, the study of mathematics was marginalized and ultimately excluded from the history of science. The alienation between the two fields is detrimental to both, and in recent years there has been a sustained effort to reestablish meaningful communication between the two. This time, however, mathematics is seen not as the static skeleton of science but, instead, as a dynamic and historically evolving field in its own right-just like science itself. The new approach allows for a culturally sensitive study of mathematics, as well as a new and fruitful relationship between the history of science and the history of mathematics. The essays in this Focus section offer a sampling of the new approaches, opening the way to a rapprochement between fields that have gone their separate ways but should by rights be closely interconnected. 相似文献
30.