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   649905篇
  免费   7260篇
  国内免费   1914篇
化学   326196篇
晶体学   7965篇
力学   31606篇
综合类   14篇
数学   89705篇
物理学   203593篇
  2021年   4566篇
  2020年   5409篇
  2019年   5955篇
  2018年   13247篇
  2017年   13628篇
  2016年   14068篇
  2015年   7742篇
  2014年   11320篇
  2013年   27342篇
  2012年   23515篇
  2011年   33635篇
  2010年   22817篇
  2009年   22691篇
  2008年   30394篇
  2007年   32507篇
  2006年   21828篇
  2005年   23863篇
  2004年   20289篇
  2003年   18208篇
  2002年   15767篇
  2001年   17234篇
  2000年   12906篇
  1999年   9842篇
  1998年   8168篇
  1997年   8103篇
  1996年   7776篇
  1995年   7383篇
  1994年   7322篇
  1993年   7201篇
  1992年   7877篇
  1991年   7987篇
  1990年   7625篇
  1989年   7485篇
  1988年   7535篇
  1987年   7380篇
  1986年   6915篇
  1985年   9163篇
  1984年   9503篇
  1983年   7537篇
  1982年   7779篇
  1981年   7730篇
  1980年   7248篇
  1979年   7786篇
  1978年   8029篇
  1977年   7857篇
  1976年   7882篇
  1975年   7230篇
  1974年   7225篇
  1973年   7282篇
  1972年   5158篇
排序方式: 共有10000条查询结果,搜索用时 21 毫秒
91.
Journal of Radioanalytical and Nuclear Chemistry - In this paper a study for the selection of an NPE (nonylphenol ethoxylates)—free cocktail is discussed in order to be used for our routine...  相似文献   
92.
Journal of Structural Chemistry - The crystal structures and biological properties of [N′-(2-oxidobenzylidene)-N-(prop-2-en-1-yl)-carbamohydrazonothioato(2-)](1,10-phenanthroline)copper...  相似文献   
93.
Kinetics and Catalysis - A new ruthenium(II) cage complex with polar terminal groups in the apical substituents has been synthesized; the molecular design of the complex contributes to the...  相似文献   
94.
Diene rhodium complexes are important catalysts in modern organic synthesis. Herein, we report a new approach to such complexes with the uncommon planar chirality. The synthesis is achieved by face-selective coordination of the prochiral 2,5-disubstituted-1,4-benzoquinones (R2-Q) with rhodium precursors containing the chiral auxiliary ligand S-salicyl-oxazoline (S-Salox). Such coordination leads to the formation of (R,R-R2-Q)Rh(S-Salox) complexes in high yields and with exceptional diastereoselectivity (d. r.>20 : 1). Subsequent replacement of the auxiliary ligand provides various benzoquinone rhodium complexes with retention of the planar chirality. Combined theoretical and experimental studies show that due to their electron-withdrawing nature benzoquinones bind metals stronger than the related 1,4-cyclohexadiene, but weaker than other common diene ligands, such as cyclooctadiene.  相似文献   
95.
Ultrasound has been recognized as an exciting tool to enhance the therapeutic efficacy in tumor chemotherapy owing to the triggered drug release, facilitated intracellular drug delivery, and improved spatial precision. Aiming for a precise localized drug delivery, novel dendritic polyurethane-based prodrug (DOX-DPU-PEG) was fabricated with a drug content of 18.9% here by conjugating DOX onto the end groups of the functionalized dendritic polyurethane via acid-labile imine bonds. It could easily form unimolecular micelles around 38 nm. Compared with the non-covalently drug-loaded unimolecular micelles (DOX@Ph-DPU-PEG), they showed excellent pH/ultrasound dual-triggered drug release performance, with drug leakage of only 4% at pH 7.4, but cumulative release of 14% and 88% at pH 5.0 without and with ultrasound, respectively. The ultrasound responsiveness was attributed to the unique strawberry-shaped topological structure of the DOX-DPU-PEG, in which DOX was embedded in the skin layer of the hydrophobic DPU cores. With ultrasound, the DOX-DPU-PEG unimolecular micelles possessed enhanced tumor growth inhibition than free DOX but showed no obvious cytotoxicity on the tumor cells without ultrasound. Such feature makes them promising potential for precise localized drug delivery.  相似文献   
96.
Shamolin  M. V. 《Doklady Mathematics》2022,106(3):479-484
Doklady Mathematics - Tensor invariants (differential forms) for homogeneous dynamical systems on tangent bundles of smooth three-dimensional manifolds are presented. The connection between the...  相似文献   
97.
Theoretical and Experimental Chemistry - The electronic and spatial structure of 3,4-ethylenedioxythiophene oligomer containing 12 units (E12) in 0, +1, +2, +3, and +4 charge states has been...  相似文献   
98.
99.
Journal of Structural Chemistry - The structures of Ni(II), Cu(II), and Zn(II) complexes with anions of 2,5-pyrrolyl-disubstituted nitronyl nitroxide (L1) and iminonitroxide (L2) diradicals (HL1 is...  相似文献   
100.
Journal of Analytical Chemistry - The present study reports the development of a magnetic polyethylene glycol nanocomposite based on graphite reinforcement carbon paste electrode for the sensitive...  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