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   320698篇
  免费   3150篇
  国内免费   1063篇
化学   175819篇
晶体学   5032篇
力学   12854篇
综合类   11篇
数学   34553篇
物理学   96642篇
  2020年   2543篇
  2019年   2799篇
  2018年   3759篇
  2017年   3603篇
  2016年   5372篇
  2015年   3246篇
  2014年   5009篇
  2013年   13492篇
  2012年   9825篇
  2011年   12263篇
  2010年   8484篇
  2009年   8116篇
  2008年   11463篇
  2007年   11589篇
  2006年   10986篇
  2005年   10213篇
  2004年   9077篇
  2003年   8312篇
  2002年   8062篇
  2001年   8871篇
  2000年   6926篇
  1999年   5339篇
  1998年   4634篇
  1997年   4635篇
  1996年   4392篇
  1995年   3843篇
  1994年   3738篇
  1993年   3761篇
  1992年   4064篇
  1991年   4142篇
  1990年   3970篇
  1989年   3951篇
  1988年   3882篇
  1987年   3873篇
  1986年   3650篇
  1985年   4863篇
  1984年   5093篇
  1983年   4176篇
  1982年   4740篇
  1981年   4441篇
  1980年   4244篇
  1979年   4474篇
  1978年   4707篇
  1977年   4631篇
  1976年   4627篇
  1975年   4397篇
  1974年   4281篇
  1973年   4607篇
  1972年   2998篇
  1967年   2814篇
排序方式: 共有10000条查询结果,搜索用时 921 毫秒
31.
32.
Journal of Sol-Gel Science and Technology - In this paper, a simple method is presented for making a conductive and hydrophobic cotton fabric using a multi-walled carbon nanotube (MWCNT). The...  相似文献   
33.
The reaction mechanism for the hydrolysis of trimethyl phosphate and of the obtained phosphodiester by the di‐CoII derivative of organophosphate degrading enzyme from Agrobacterium radiobacter P230(OpdA), have been investigated at density functional level of theory in the framework of the cluster model approach. Both mechanisms proceed by a multistep sequence and each catalytic cycle begins with the nucleophilic attack by a metal‐bound hydroxide on the phosphorus atom of the substrate, leading to the cleavage of the phosphate‐ester bond. Four exchange‐correlation functionals were used to derive the potential energy profiles in protein environments. Although the enzyme is confirmed to work better as triesterase, as revealed by the barrier heights in the rate‐limiting steps of the catalytic processes, its promiscuous ability to hydrolyze also the product of the reaction has been confirmed. The important role played by water molecules and some residues in the outer coordination sphere has been elucidated, while the binuclear CoII center accomplishes both structural and catalytic functions. To correctly describe the electronic configuration of the d shell of the metal ions, high‐ and low‐spin arrangement jointly with the occurrence of antiferromagnetic coupling, have been herein considered.  相似文献   
34.
35.
Su  X. F.  Zhang  Y. L.  Maximov  A. L.  Zhang  K.  Xin  Q.  Feng  C. Q.  Bai  X. F.  Wu  W. 《Russian Journal of Applied Chemistry》2020,93(1):127-136
Russian Journal of Applied Chemistry - Nanoscale ZSM-5 (AlZ5-D) and Ga-substituted ZSM-5 zeolites ((Al,Ga)Z5-D and GaZ5-D) were synthesized by a green dry-gel conversion strategy. For comparison,...  相似文献   
36.
The results of investigation of optical image detectors designed for the largest problem, near-VUV, range of the spectrum are presented. The possibility of using a dual-stage image detection system to appreciably lower the sensitivity threshold and make computer data processing feasible is considered. The integration of a UV module into a wideband image detector is studied.  相似文献   
37.
Russian Chemical Bulletin - Quantum chemical calculations and a comparative analysis of Raman spectra of 3,4,5-triphenyl-1-propyl-1,2-diphosphole (1),...  相似文献   
38.
39.
Development of biocompatible porous supports is a promising strategy in the field of tissue engineering for the repair and regeneration of bone tissues with severe damage. Graphene oxide aerogels (GOAs) are excellent candidates for the manufacture of these systems due to their porosity, ability to imitate bone structure, and mechanical resistance, and according to their surface chemical reactivity, they can facilitate osseointegration, osteogenesis, osteoinduction and osteoconduction. In this review, synthesis of GOAs from the most primary source is described, and recent studies on the use of these functionalized carbonaceous foams as scaffolding for bone tissue regeneration are presented.  相似文献   
40.
Russian Journal of General Chemistry - Some new fluoro-heterocyclic compounds containing thiazole and pyridine moities have been synthesized and studied for their antiproliferative activity....  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