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   329643篇
  免费   3024篇
  国内免费   574篇
化学   153635篇
晶体学   4562篇
力学   17944篇
综合类   14篇
数学   52150篇
物理学   104936篇
  2021年   2320篇
  2020年   2556篇
  2019年   2979篇
  2018年   11591篇
  2017年   12246篇
  2016年   9498篇
  2015年   3920篇
  2014年   5411篇
  2013年   10812篇
  2012年   12579篇
  2011年   20935篇
  2010年   13968篇
  2009年   14063篇
  2008年   18745篇
  2007年   21755篇
  2006年   8609篇
  2005年   12981篇
  2004年   9789篇
  2003年   9283篇
  2002年   7452篇
  2001年   6607篇
  2000年   5160篇
  1999年   3687篇
  1998年   3194篇
  1997年   3218篇
  1996年   3224篇
  1995年   2818篇
  1994年   2923篇
  1993年   2836篇
  1992年   3179篇
  1991年   3130篇
  1990年   3046篇
  1989年   3073篇
  1988年   2985篇
  1987年   3033篇
  1986年   2830篇
  1985年   3654篇
  1984年   3702篇
  1983年   3119篇
  1982年   3118篇
  1981年   3081篇
  1980年   2883篇
  1979年   3229篇
  1978年   3203篇
  1977年   3317篇
  1976年   3309篇
  1975年   3079篇
  1974年   3009篇
  1973年   3096篇
  1972年   2291篇
排序方式: 共有10000条查询结果,搜索用时 390 毫秒
991.
Efficient quenching of eosin phosphorescence by amino-acid derivatives of fullerene (AADFs) such as C60-alanine and C60-glycine in aqueous solutions indicates the possibility of transferring electrons from eosin to fullerene upon collisions or in the exciplex state. To investigate electron transfer in the protein structure, we studied the process of incorporation of C60-alanine and C60-glycine into the heme pocket of myoglobin by controlling Förster quenching. The dissociation constant for the protein-AADF complex was estimated.  相似文献   
992.
A model of silane decomposition in a radio-frequency argon plasma is constructed. The concentrations of SiH4 decomposition products, as well as products of synthesis (higher silanes), are calculated. The role of metastable argon atoms in the formation of SiH3 radicals and the higher silanes is analyzed.  相似文献   
993.
994.
Several variations of two-dimensional (workers x jobs) and three-dimensional (workers x jobs x machines) time- as well as cost-minimizing assignment problems, which arise owing to (i) precedence relations of some form among the jobs or (ii) capacity restrictions on workers/machines imposed by the requirement that the surplus resources have to be fully employed, have been considered in the literature. In this paper, an algorithm is presented for time-cost trade-off analysis which is applicable to any general pair of such constrained problems. The algorithm is also illustrated by a numerical example.  相似文献   
995.
This note discusses the need to use various data-compaction schemes in the implementation of sophisticated large-scale linear programming codes on modest personal computers. It demonstrates a method whereby the overhead of using these schemes is significantly reduced on Intel 80 x 86 processors.  相似文献   
996.
997.
We study convergence properties of a modified subgradient algorithm, applied to the dual problem defined by the sharp augmented Lagrangian. The primal problem we consider is nonconvex and nondifferentiable, with equality constraints. We obtain primal and dual convergence results, as well as a condition for existence of a dual solution. Using a practical selection of the step-size parameters, we demonstrate the algorithm and its advantages on test problems, including an integer programming and an optimal control problem. *Partially Supported by 2003 UniSA ITEE Small Research Grant Ero2. Supported by CAPES, Brazil, Grant No. 0664-02/2, during her visit to the School of Mathematics and Statistics, UniSA.  相似文献   
998.
999.
In the article, it is proved that any nonnegative solution of an elliptic quasilinear inequality that vanishes on a subset of positive measure is trivial. __________ Translated from Trudy Seminara imeni I. G. Petrovskogo, No. 25, pp. 112–118, 2005.  相似文献   
1000.
Utilization of carbohydrates by radiation processing   总被引:2,自引:0,他引:2  
Upgrading and utilization of carbohydrates such as chitosan, sodium alginate, carrageenan, cellulose, pectin have been investigated for recycling these bio-resources and reducing the environmental pollution. These carbohydrates were easily degraded by irradiation and various kinds of biological activities such as anti-microbial activity, promotion of plant growth, suppression of heavy metal stress, phytoalexins induction, etc. were induced. On the other hand, some carbohydrate derivatives, carboxymethylcellulose and carboxymethylstarch, could be crosslinked under certain radiation condition and produce the biodegradable hydrogel for medical and agricultural use.  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