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   662521篇
  免费   7137篇
  国内免费   2504篇
化学   342439篇
晶体学   9473篇
力学   32099篇
综合类   78篇
数学   86994篇
物理学   201079篇
  2021年   5826篇
  2020年   6463篇
  2019年   7179篇
  2018年   9567篇
  2017年   9701篇
  2016年   13561篇
  2015年   7686篇
  2014年   12452篇
  2013年   29128篇
  2012年   23069篇
  2011年   27651篇
  2010年   20419篇
  2009年   20164篇
  2008年   26067篇
  2007年   25932篇
  2006年   23830篇
  2005年   21400篇
  2004年   19631篇
  2003年   17549篇
  2002年   17462篇
  2001年   18585篇
  2000年   14373篇
  1999年   11034篇
  1998年   9487篇
  1997年   9325篇
  1996年   8837篇
  1995年   7941篇
  1994年   7996篇
  1993年   7667篇
  1992年   8213篇
  1991年   8612篇
  1990年   8176篇
  1989年   8064篇
  1988年   7841篇
  1987年   7556篇
  1986年   7326篇
  1985年   9500篇
  1984年   9857篇
  1983年   8286篇
  1982年   8699篇
  1981年   8130篇
  1980年   7703篇
  1979年   8240篇
  1978年   8620篇
  1977年   8518篇
  1976年   8516篇
  1975年   8065篇
  1974年   7984篇
  1973年   8307篇
  1972年   6157篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
211.
Popel  S. I.  Golub’  A. P. 《JETP Letters》2022,115(10):596-601
JETP Letters - One of the main features of the dusty plasma compared to the conventional plasma (without charged dust particles is anomalous dissipation that is caused by the charging of dust...  相似文献   
212.
Russian Journal of General Chemistry - Highly dispersed CaO has been synthesized by heating an aqueous solution of calcium nitrate and D-glucose up to 800°C. Calcium oxide is formed with an...  相似文献   
213.
Differential Equations - We consider an initial–boundary value problem for the heat equation in which the heat conduction coefficient and one of the functions occurring in the source depend...  相似文献   
214.
Russian Journal of Organic Chemistry - Methyl (Z)-3-[(2R,3R,4S,5S)-5-(2-methoxy-2-oxoethyl)-3,4-(isopropylidenedioxy)tetrahydrofuran-2-yl]-prop-2-enoate was synthesized, and its intramolecular...  相似文献   
215.
Tetrahydrotetrazoles are five‐membered‐ring heterocycles containing four contiguous saturated nitrogen atoms. Very few examples of such compounds have been reported in the literature. Our previous attempt at the synthesis of a member of this class of compound suggested that the N—N bonds may be more labile than expected. This finding raised the question as to whether the structures of any of the previously reported tetrahydrotetrazoles had been properly assigned. We have reproduced the synthesis of a reported tetrahydrotetrazole, namely 1,2‐di‐tert‐butyl 3‐phenyl‐1H,2H,3H,10bH‐[1,2,3,4]tetrazolo[5,1‐a]isoquinoline‐1,2‐dicarboxylate, C25H30N4O4, and have now confidently confirmed its structure via X‐ray crystallography. However, while sufficiently stable in the crystal phase, we discovered that it remains very labile in solution (having a half‐life of only 15 min at 20 °C in CDCl3). A tentative reaction pathway for its dissociation based on 1H NMR spectral evidence is provided.  相似文献   
216.
217.
Syrovatka  R. A.  Lipaev  A. M.  Naumkin  V. N.  Klumov  B. A. 《JETP Letters》2022,116(12):869-874
JETP Letters - A quasi-two-dimensional plasma crystal in (3 + 1) dimensions has been experimentally observed for the first time; i.e., three spatial coordinates of each microparticles of the...  相似文献   
218.
Journal of Analytical Chemistry - A review of works in developing optical multisensor systems, a new class of specialized spectroscopic analyzers, is presented. The development and use of such...  相似文献   
219.
Crystallography Reports - The formation of Zn-based nanotubes by electrochemical synthesis in pores of template polymer matrices is considered. It is established that the number of defects in the...  相似文献   
220.

A procedure was suggested for preparing brominated polyols of reduced viscosity for the synthesis of foamed polyurethanes of reduced flammability. The flame-retarding action of the synthesized polyol tetrabromophthalate in polyurethane was studied in comparison with that of other widely used flame retardants. Evaluation of the effect exerted on the flammability of the polurethane compound by the polyol tetrabromophthalate synthesized, melamine, and aluminum hydroxide shows that all the samples containing flame retardants are self-extinguishing. The shortest combustion time was observed for the sample containing 6% polyol tetrabromophthalate synthesized. The sample containing as a flame retardant additive solely the synthesized polyole tetrabromophthalate also exhibits the highest performance as a heat-insulating material from the viewpoint of thermal conductivity.

  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