全文获取类型
收费全文 | 25323篇 |
免费 | 195篇 |
国内免费 | 11篇 |
专业分类
教育 | 18376篇 |
科学研究 | 2873篇 |
各国文化 | 117篇 |
体育 | 1349篇 |
综合类 | 17篇 |
文化理论 | 537篇 |
信息传播 | 2260篇 |
出版年
2022年 | 98篇 |
2021年 | 141篇 |
2020年 | 212篇 |
2019年 | 294篇 |
2018年 | 2563篇 |
2017年 | 2506篇 |
2016年 | 1972篇 |
2015年 | 394篇 |
2014年 | 501篇 |
2013年 | 2307篇 |
2012年 | 561篇 |
2011年 | 1057篇 |
2010年 | 1154篇 |
2009年 | 706篇 |
2008年 | 930篇 |
2007年 | 1456篇 |
2006年 | 342篇 |
2005年 | 622篇 |
2004年 | 712篇 |
2003年 | 587篇 |
2002年 | 367篇 |
2001年 | 319篇 |
2000年 | 361篇 |
1999年 | 260篇 |
1998年 | 141篇 |
1997年 | 196篇 |
1996年 | 178篇 |
1995年 | 121篇 |
1994年 | 133篇 |
1993年 | 117篇 |
1992年 | 198篇 |
1991年 | 191篇 |
1990年 | 213篇 |
1989年 | 213篇 |
1988年 | 184篇 |
1987年 | 195篇 |
1986年 | 177篇 |
1985年 | 213篇 |
1984年 | 154篇 |
1983年 | 138篇 |
1982年 | 129篇 |
1981年 | 112篇 |
1980年 | 114篇 |
1979年 | 178篇 |
1978年 | 132篇 |
1977年 | 116篇 |
1976年 | 91篇 |
1975年 | 95篇 |
1974年 | 95篇 |
1973年 | 92篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Quantum chemistry is based on the solution of the Schrödinger equation for a molecule. From starting data on the positions and nature of constituent atoms information is provided about the energy of the molecule and its electronic properties. The former can indicate what shapes drugs can adopt in binding to pharmacological receptors whilst electronic details, when compared using computer graphics, may highlight the factors responsible for biological activity. These techniques are beginning to show real successes in the design of drug molecules. 相似文献
92.
The paper combines a comprehensive account of the probabilistic model of retrieval with new systematic experiments on TREC Programme material. It presents the model from its foundations through its logical development to cover more aspects of retrieval data and a wider range of system functions. Each step in the argument is matched by comparative retrieval tests, to provide a single coherent account of a major line of research. The experiments demonstrate, for a large test collection, that the probabilistic model is effective and robust, and that it responds appropriately, with major improvements in performance, to key features of retrieval situations.Part 1 covers the foundations and the model development for document collection and relevance data, along with the test apparatus. Part 2 covers the further development and elaboration of the model, with extensive testing, and briefly considers other environment conditions and tasks, model training, concluding with comparisons with other approaches and an overall assessment.Data and results tables for both parts are given in Part 1. Key results are summarised in Part 2. 相似文献
93.
Jansen S 《Endeavour》2000,24(1):28-33
During World War I, chemical-warfare practices were introduced into economic entomology in Germany. Fritz Haber, 'the father of chemical warfare', realized that Germany could not win the war and thus looked for 'civilian' uses for his chemical arsenal. Before the war, there was a rhetoric of dangerous 'masses' of insects but the large-scale techniques needed to deal with them had not been developed. The gap between rhetoric and practices enabled entomology to integrate chemical weapons into its working methods. This article traces transformations in the ways of seeing insects and their control from the mid-nineteenth century to after World War I. 相似文献
94.
95.
P. Sharma M. Bose Isa Mohd S. Bagdi H. G. Raj 《Indian journal of clinical biochemistry : IJCB》2000,15(2):83-87
Genomic DNA from a clinical isolate ofMycobacterium avium-intracellulare complex was purified and cloned in PBR 322 at the tetracycline resistance site using Bam HI restriction enzyme. A 16 kb cloned
fragment was purified, radiolabeled and used as a probe. Genomic DNA isolated from nineteen MAC strains, threeM. tuberculosis strains and oneM. kansasii strain were digested with Eco RI restriction enzyme, Southern blotted and hybridized with the 16 kb cloned and labeled fragment.
Twelve MAC strains showed positive hybridization although five strains gave faint signals. Positive hybridization was noted
in two out of the threeM. tuberculosis strains, possibly due to shared DNA homology. No signal was received from the singleM. kansasii strain used in this study. 相似文献
96.
Sutter PS 《Isis; an international review devoted to the history of science and its cultural influences》2007,98(4):724-754
This essay examines the role that entomological workers played in U.S. public health efforts during the construction of the Panama Canal (1904-1914). Entomological workers were critical to mosquito control efforts aimed at the reduction of tropical fevers such as malaria. But in the process of studying vector mosquitoes, they discovered that many of the conditions that produced mosquitoes were not intrinsic to tropical nature per se but resulted from the human-caused environmental disturbances that accompanied canal building. This realization did not mesh well with an American ideology of tropical triumphalism premised on the notion that the Americans had conquered unalloyed tropical nature in Panama. The result, however, was not a coherent counternarrative but a set of intra-administrative tensions over what controlling nature meant in Panama. Ultimately, entomological workers were loyal not just to the U.S. imperial mission in Panama but also to a modernist culture of science and to the workings of mosquito ecology as they understood them. 相似文献
97.
98.
Anders Albrechtslund 《Ethics and Information Technology》2007,9(1):63-72
This article offers a discussion of the connection between technology and values and, specifically, I take a closer look at
ethically sound design. In order to bring the discussion into a concrete context, the theory of Value Sensitive Design (VSD)
will be the focus point. To illustrate my argument concerning design ethics, the discussion involves a case study of an augmented
window, designed by the VSD Research Lab, which has turned out to be a potentially surveillance-enabling technology. I call
attention to a “positivist problem” that has to do with the connection between the design context and the use context, which
VSD seems to presuppose, and I argue that it is necessary to clearly distinguish between the two, since the designers’ intentions
do not always correspond with the users’ practice; in fact, the relation between design and use is very complex and principally
unpredictable. Thus, a design theory must accept that foresight is limited to anticipation rather than prediction. To overcome
the positivist problem, I suggest a phenomenological approach to technology inspired by Don Ihde’s concept of multistability.
This argument, which is general in nature and thus applies to any theory of design ethics, is intended as a constructive criticism,
which can hopefully contribute to the further development of design ethics. 相似文献
99.
100.