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   359112篇
  免费   2359篇
  国内免费   752篇
化学   175274篇
晶体学   5255篇
力学   17666篇
综合类   7篇
数学   52696篇
物理学   111325篇
  2021年   2426篇
  2020年   2685篇
  2019年   3094篇
  2018年   11394篇
  2017年   12034篇
  2016年   9274篇
  2015年   3818篇
  2014年   5303篇
  2013年   12027篇
  2012年   12857篇
  2011年   21506篇
  2010年   14007篇
  2009年   14022篇
  2008年   19456篇
  2007年   22483篇
  2006年   10067篇
  2005年   14187篇
  2004年   10745篇
  2003年   10319篇
  2002年   8482篇
  2001年   7899篇
  2000年   6314篇
  1999年   4540篇
  1998年   3983篇
  1997年   3895篇
  1996年   3720篇
  1995年   3133篇
  1994年   3194篇
  1993年   3218篇
  1992年   3400篇
  1991年   3502篇
  1990年   3333篇
  1989年   3362篇
  1988年   3229篇
  1987年   3148篇
  1986年   3014篇
  1985年   3859篇
  1984年   4096篇
  1983年   3335篇
  1982年   3638篇
  1981年   3416篇
  1980年   3178篇
  1979年   3456篇
  1978年   3708篇
  1977年   3658篇
  1976年   3582篇
  1975年   3398篇
  1974年   3384篇
  1973年   3534篇
  1972年   2393篇
排序方式: 共有10000条查询结果,搜索用时 375 毫秒
41.
42.
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   
43.
44.
45.
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   
46.
We summarize the results of our recent work on Bäcklund transformations (BTs), particularly focusing on the relation between BTs and infinitesimal symmetries. We present a BT for an associated Degasperis–Procesi (aDP) equation and its superposition principle and investigate the solutions generated by applying this BT. Following our general methodology, we use the superposition principle of the BT to generate the infinitesimal symmetries of the aDP equation.  相似文献   
47.
Mesoscopic modeling at the pore scale offers great promise in exploring the underlying structure transport performance of flow through porous media. The present work studies the fluid flow subjected to capillarity-induced resonance in porous media characterized by different porous structure and wettability. The effects of porosity and wettability on the displacement behavior of the fluid flow through porous media are discussed. The results are presented in the form of temporal evolution of percentage saturation and displacement of the fluid front through porous media. The present study reveals that the vibration in the form of acoustic excitation could be significant in the mobilization of fluid through the porous media. The dependence of displacement of the fluid on physicochemical parameters like wettability of the surface, frequency along with the porosity is analyzed. It was observed that the mean displacement of the fluid is more in the case of invading fluid with wetting phase where the driving force strength is not so dominant.  相似文献   
48.
49.
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   
50.
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