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   390494篇
  免费   8034篇
  国内免费   5741篇
化学   188303篇
晶体学   5793篇
力学   22122篇
综合类   323篇
数学   67347篇
物理学   120381篇
  2021年   3375篇
  2020年   3889篇
  2019年   4296篇
  2018年   15075篇
  2017年   14733篇
  2016年   12700篇
  2015年   5345篇
  2014年   7340篇
  2013年   14720篇
  2012年   15599篇
  2011年   24034篇
  2010年   15808篇
  2009年   16099篇
  2008年   18845篇
  2007年   20683篇
  2006年   11763篇
  2005年   11611篇
  2004年   10919篇
  2003年   10324篇
  2002年   9483篇
  2001年   9521篇
  2000年   7371篇
  1999年   5783篇
  1998年   5080篇
  1997年   4749篇
  1996年   4606篇
  1995年   4085篇
  1994年   4043篇
  1993年   4077篇
  1992年   4135篇
  1991年   4346篇
  1990年   4070篇
  1989年   3961篇
  1988年   3849篇
  1987年   3773篇
  1986年   3579篇
  1985年   4611篇
  1984年   4788篇
  1983年   3885篇
  1982年   4104篇
  1981年   3942篇
  1980年   3817篇
  1979年   4023篇
  1978年   4118篇
  1977年   4007篇
  1976年   4197篇
  1975年   3800篇
  1974年   3821篇
  1973年   3894篇
  1972年   2867篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
61.
We prove that the group of diffeomorphisms of the interval [0, 1] contains surface groups whose action on (0, 1) has no global fix point and such that only countably many points of the interval (0, 1) have non-trivial stabiliser.  相似文献   
62.
Theoretical and Computational Fluid Dynamics - The present study aims to simulate a collision of two droplets containing immiscible liquids by employing a three- dimensional incompressible smoothed...  相似文献   
63.
A new strategy for the synthesis of tetrahydroisoquinolines based on the Pd0‐catalyzed intramolecular α‐arylation of sulfones is reported. The combination of this Pd‐catalyzed reaction with intermolecular Michael and aza‐Michael reactions allows the development of two‐ and three‐step domino processes to synthesize diversely functionalized scaffolds from readily available starting materials.  相似文献   
64.
65.
This study was aimed at the development of a conductometric biosensor based on acetylcholinesterase considering the feasibility of its application for the inhibitory analysis of various toxicants. In this paper, the optimum conditions for enzyme immobilization on the transducer surface are selected as well as the optimum concentration of substrate for inhibitory analysis. Sensitivity of the developed biosensor to different classes of toxic compounds (organophosphorus pesticides, heavy metal ions, surfactants, aflatoxin, glycoalkaloids) was tested. It is shown that the developed biosensor can be successfully used for the analysis of pesticides and mycotoxins, as well as for determination of total toxicity of the samples. A new method of biosensor analysis of toxic substances of different classes in complex multicomponent aqueous samples is proposed.  相似文献   
66.
67.
68.
Hierarchically porous metal–organic frameworks (HP-MOFs) are promising in various applications. Most reported HP-MOFs are prepared based on the generation of mesopores in microporous frameworks, and the formed mesopores are connected by microporous channels, limiting the accessibility of mesopores for bulky molecules. A hierarchical structure is formed by constructing microporous MOFs in uninterrupted mesoporous tunnels. Using the confined space in as-prepared mesoporous silica, highly dispersed metal precursors for MOFs are coated on the internal surface of mesoporous tunnels. Ligand vapor-induced crystallization is employed to enable quantitative formation of MOFs in situ, in which sublimated ligands diffuse into mesoporous tunnels and react with metal precursors. The obtained hierarchically porous composites exhibit record-high adsorption capacity for the bulky molecule trypsin. The thermal and storage stability of trypsin is improved upon immobilization on the composites.  相似文献   
69.
Russian Journal of General Chemistry - 8-Phenyltetrazolo[5,1-b][1,3,4]thiadiazepine was obtained as a result of intermolecular cyclization of 1-amino-1H-tetrazole-5-thiol and 3-phenyl-2-propynal....  相似文献   
70.
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   
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