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   344167篇
  免费   3254篇
  国内免费   1002篇
化学   187735篇
晶体学   4950篇
力学   14389篇
综合类   12篇
数学   37679篇
物理学   103658篇
  2020年   2900篇
  2019年   3236篇
  2018年   4388篇
  2017年   4291篇
  2016年   6335篇
  2015年   3695篇
  2014年   5835篇
  2013年   14714篇
  2012年   11123篇
  2011年   13735篇
  2010年   9663篇
  2009年   9557篇
  2008年   12928篇
  2007年   13083篇
  2006年   12198篇
  2005年   11140篇
  2004年   9863篇
  2003年   8903篇
  2002年   8846篇
  2001年   9492篇
  2000年   7454篇
  1999年   5614篇
  1998年   4897篇
  1997年   4903篇
  1996年   4546篇
  1995年   3965篇
  1994年   4021篇
  1993年   3940篇
  1992年   4277篇
  1991年   4485篇
  1990年   4197篇
  1989年   4189篇
  1988年   4051篇
  1987年   3937篇
  1986年   3758篇
  1985年   4990篇
  1984年   5184篇
  1983年   4194篇
  1982年   4639篇
  1981年   4386篇
  1980年   4141篇
  1979年   4479篇
  1978年   4740篇
  1977年   4650篇
  1976年   4668篇
  1975年   4432篇
  1974年   4465篇
  1973年   4590篇
  1972年   3071篇
  1967年   2776篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Russian Journal of Physical Chemistry A - Rapidly quenched alloys of aluminum with cobalt and zirconium are investigated using a combination of means of physicochemical analysis to study the...  相似文献   
32.
33.
34.
The development of high‐surface‐area carbon electrodes with a defined pore size distribution and the incorporation of pseudo‐active materials to optimize the overall capacitance and conductivity without destroying the stability are at present important research areas. Composite electrodes of carbon nano‐onions (CNOs) and polypyrrole (Ppy) were fabricated to improve the specific capacitance of a supercapacitor. The carbon nanostructures were uniformly coated with Ppy by chemical polymerization or by electrochemical potentiostatic deposition to form homogenous composites or bilayers. The materials were characterized by transmission‐ and scanning electron microscopy, differential thermogravimetric analyses, FTIR spectroscopy, piezoelectric microgravimetry, and cyclic voltammetry. The composites show higher mechanical and electrochemical stabilities, with high specific capacitances of up to about 800 F g?1 for the CNOs/SDS/Ppy composites (chemical synthesis) and about 1300 F g?1 for the CNOs/Ppy bilayer (electrochemical deposition).  相似文献   
35.
Russian Journal of General Chemistry - Hybrid liquid crystal systems with different ratios of the components have been prepared on the basis of 5,5′-di(heptadecyl)-2,2′-bipyridine...  相似文献   
36.
37.
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   
38.
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   
39.
40.
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