全文获取类型
收费全文 | 2326篇 |
免费 | 53篇 |
国内免费 | 9篇 |
专业分类
化学 | 1414篇 |
晶体学 | 10篇 |
力学 | 37篇 |
数学 | 391篇 |
物理学 | 336篇 |
无线电 | 200篇 |
出版年
2022年 | 17篇 |
2021年 | 31篇 |
2020年 | 23篇 |
2019年 | 24篇 |
2018年 | 21篇 |
2017年 | 21篇 |
2016年 | 39篇 |
2015年 | 31篇 |
2014年 | 35篇 |
2013年 | 123篇 |
2012年 | 96篇 |
2011年 | 117篇 |
2010年 | 71篇 |
2009年 | 51篇 |
2008年 | 100篇 |
2007年 | 101篇 |
2006年 | 112篇 |
2005年 | 123篇 |
2004年 | 93篇 |
2003年 | 79篇 |
2002年 | 68篇 |
2001年 | 32篇 |
2000年 | 32篇 |
1999年 | 24篇 |
1998年 | 26篇 |
1997年 | 27篇 |
1996年 | 33篇 |
1995年 | 31篇 |
1994年 | 27篇 |
1993年 | 24篇 |
1992年 | 35篇 |
1991年 | 28篇 |
1990年 | 19篇 |
1989年 | 19篇 |
1988年 | 29篇 |
1986年 | 20篇 |
1985年 | 48篇 |
1984年 | 46篇 |
1983年 | 38篇 |
1982年 | 45篇 |
1981年 | 43篇 |
1980年 | 50篇 |
1979年 | 31篇 |
1978年 | 41篇 |
1977年 | 39篇 |
1976年 | 28篇 |
1975年 | 30篇 |
1974年 | 28篇 |
1973年 | 22篇 |
1969年 | 16篇 |
排序方式: 共有2388条查询结果,搜索用时 15 毫秒
211.
Jack Murray 《中国电子商情》2010,(8):25-25
在全球最火热的电子设备增长领域当属医疗电子。世界卫生组织估计,目前卫生保健消费达到了5.3万亿美元,而这个数字将在下一个5年到10年的时间内快速增长。 相似文献
212.
Abstract In the present study, the two compressibility moduli of a zinc single crystal were measured at room temperature up to 18 GPa. The results are compared with those obtained by Bridgman from a different experimental method. This study required a gaseous hydrostatic confining pressure, and then it has been necessary to develop an original diamond anvil cell with a large optical aperture allowing the use of sophisticated video imaging and image analysis techniques. A model is proposed for the zinc volume-pressure relation. 相似文献
213.
214.
Jeevan Jaisingh Jack Barron Shailendra Mehta Alok Chaturvedi 《European Journal of Operational Research》2008
The issues we address here are – How should a firm (e.g. Internet service provider (ISP)) that is capable of collecting personal information (browsing information, purchase history, etc.) about consumers, price its service, given that consumers vary in their valuation for privacy, and also vary in terms of the value of their personal information to a third party (firms that need consumer information)? Should the firm have a blanket policy of never collecting, or a policy of always collecting and revealing information? Surprisingly we find that in some cases the collector of information may be no worse off in the asymmetric information case than in the full information case. The paper provides a justification for the strategy of some firms such as ISP’s which never collect information and also for the strategy of other firms, like grocery stores that do. We also find that it is non-optimal for the firm to design contracts where the consumer can choose an intermediate level of privacy. 相似文献
215.
Jack Grahl 《Journal of Mathematical Analysis and Applications》2008,340(1):358-365
We construct an integral of a measurable real function using randomly chosen Riemann sums and show that it converges in probability to the Lebesgue integral where this exists. We then prove some conditions for the almost sure convergence of this integral. 相似文献
216.
217.
Jack M. Shapiro 《代数通讯》2013,41(6):1879-1898
For a field F with trivial involution we have the Karoubi L-groups ±1Ln(F). For 0≤n≤2 these groups are intimately related to subgroups of the classical Witt ring of quadratic forms. -1L 2(F) also has a presentation by symbols due to Matsumoto. In terms of this data we make explicit calculations for two cup product maps that appear in the L-theory of fields. 相似文献
218.
In hyperconvex metric spaces we consider best approximation, invariant approximation and best proximity pair problems for multivalued mappings that are condensing or nonexpansive. 相似文献
219.
220.
High-level ab initio calculations have been made for fluoromethylamine to study structural and energetic effects of the relative orientation of the N lone pair to the C? F bond. The anti-conformer (N lone pair anti-planar to the C? F bond) corresponds to the global energy minimum. It has the longest C? F distance, the shortest C? N distance, and is 7.5 kcal·mol?1 more stable than the related perpendicular conformation (lone pair perpendicular to the C? F bond). The syn-conformation also shows hallmarks of the anomeric effect: long C? F bond, short C? N bond, and energetic stability when allowance is made for the two pairs of eclipsed hydrogens. The transition state for N inversion is close to the syn-structure; rotation about the C? N bond is strongly coupled with this inversion process. Small bond distance changes of ca. 0.02 Å between parallel and perpendicular conformations are associated with dissociation energy differences of ca. 30 kcal·mol?1. Various criteria for assessing the strength of the anomeric effect are discussed. 相似文献