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   224942篇
  免费   2257篇
  国内免费   753篇
化学   124721篇
晶体学   3358篇
力学   8843篇
综合类   9篇
数学   24560篇
物理学   66461篇
  2021年   2155篇
  2020年   2327篇
  2019年   2694篇
  2018年   3649篇
  2017年   3478篇
  2016年   4857篇
  2015年   2778篇
  2014年   4370篇
  2013年   10292篇
  2012年   7680篇
  2011年   9177篇
  2010年   6620篇
  2009年   6365篇
  2008年   8622篇
  2007年   8627篇
  2006年   7929篇
  2005年   7241篇
  2004年   6352篇
  2003年   5821篇
  2002年   5651篇
  2001年   6020篇
  2000年   4732篇
  1999年   3530篇
  1998年   3048篇
  1997年   3084篇
  1996年   2866篇
  1995年   2351篇
  1994年   2454篇
  1993年   2469篇
  1992年   2628篇
  1991年   2688篇
  1990年   2587篇
  1989年   2565篇
  1988年   2489篇
  1987年   2465篇
  1986年   2384篇
  1985年   3068篇
  1984年   3228篇
  1983年   2580篇
  1982年   2855篇
  1981年   2720篇
  1980年   2521篇
  1979年   2735篇
  1978年   2849篇
  1977年   2863篇
  1976年   2845篇
  1975年   2699篇
  1974年   2680篇
  1973年   2821篇
  1972年   1885篇
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
21.
Physics of the Solid State - The external factors which influence the ferromagnetic resonance (FMR) line width in bilayer (ferromagnet/antiferromagnet) exchange-biased systems are studied. The...  相似文献   
22.
Journal of Algebraic Combinatorics - The symbolic powers, in general, are not equal to the ordinary powers. Therefore, one interesting question here is for what classes of ideals ordinary and...  相似文献   
23.
Crystallography Reports - Methods of coherent X-ray diffraction imaging of the spatial structure of noncrystalline objects and nanocrystals (nanostructures) are considered. Particular attention is...  相似文献   
24.
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   
25.
26.
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   
27.
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   
28.
29.
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   
30.
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   
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