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   116764篇
  免费   6123篇
  国内免费   5959篇
化学   54023篇
晶体学   1431篇
力学   8556篇
综合类   465篇
数学   36420篇
物理学   27951篇
  2024年   83篇
  2023年   632篇
  2022年   1055篇
  2021年   1214篇
  2020年   1392篇
  2019年   1427篇
  2018年   11418篇
  2017年   11241篇
  2016年   7585篇
  2015年   2608篇
  2014年   2398篇
  2013年   3194篇
  2012年   7028篇
  2011年   13955篇
  2010年   8243篇
  2009年   8531篇
  2008年   9376篇
  2007年   11263篇
  2006年   2535篇
  2005年   3310篇
  2004年   3105篇
  2003年   3251篇
  2002年   2344篇
  2001年   1388篇
  2000年   1211篇
  1999年   950篇
  1998年   836篇
  1997年   681篇
  1996年   788篇
  1995年   587篇
  1994年   526篇
  1993年   481篇
  1992年   417篇
  1991年   380篇
  1990年   306篇
  1989年   270篇
  1988年   243篇
  1987年   210篇
  1986年   212篇
  1985年   218篇
  1984年   152篇
  1983年   110篇
  1982年   121篇
  1981年   94篇
  1980年   101篇
  1979年   109篇
  1978年   79篇
  1976年   58篇
  1974年   53篇
  1973年   72篇
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
41.
The preparation of new ring opening metathesis polymerization (ROMP) monomers using a 1,3‐dipolar cycloaddition between aryl azides and norbornadiene is described. Various norbornenetriazolines, obtained through a solvent‐and catalyst‐free reaction, can subsequently be incorporated into polymer backbones through ROMP reactions. Furthermore, thermal decomposition of the triazoline moiety can allow for further polymer functionalization. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2357–2362  相似文献   
42.
43.
44.
Dong  Liangwei  Qi  Wei  Peng  Ping  Wang  Linxue  Zhou  Hui  Huang  Changming 《Nonlinear dynamics》2020,102(1):303-310
Nonlinear Dynamics - We address the nonlinear dynamics of binary Bose-Einstein condensates with mutually symmetric spinor components trapped in an optical lattice. The interaction between the...  相似文献   
45.
Eucommia ulmoides Oliv. (E. ulmoides) is a valuable and nourishing medicinal herb in China that has been used in the treatment of hypertension. Given the fact that most traditional Chinese medicine is mainly used to treat disease, investigating the pharmacokinetics of traditional Chinese medicines in the pathological state is more useful than that in the normal state. However, the differences in the absorption kinetics of active ingredients of E. ulmoides extract between pathological and physiological conditions have not been reported. Therefore, in this study, the rat intestinal in situ circulatory perfusion model was used to investigate the differences in absorption kinetics of seven active ingredients of E. ulmoides extract in normal and spontaneously hypertensive rats, namely, genipinic acid, protocatechuic acid, neochlorogenic acid, chlorogenic acid, cryptochlorogenic acid, (+)-pinoresinol di-O-β-D -glucopyranoside and (+)-pinoresinol 4′-O-β-D -glucopyranoside. Our results indicate that the pathological state of spontaneous hypertension may change the absorption of active components of E. ulmoides extracts, and these findings may provide a reference for improving the rational use of E. ulmoides in the clinic.  相似文献   
46.
47.
48.
Organic polymers and inorganic clusters belong to two different disciplines and have completely different properties and structures. When a cluster is attached to the backbone of a polymer as a pendant, the resultant hybrid polymers (polyclusters) exhibit unique behaviours totally different from those of conventional polymers owing to the nanoscale size of the cluster and its particular interactions. Herein, the aggregation of a poly(polyoxometalate)—a polynorbornene backbone with inorganic polyoxometalate cluster pendants—upon addition of a non-solvent to its dilute solution is reported. A three-dimensional network of tangled and snake-like nanothreads was observed. Direct visualisation of individual nanoscale clusters enabled identification of single chains within the nanothreads. These observations suggest that during the process of aggregation, the hybrid polymer forms curved or extended chains as a consequence of an armouring effect in which the collapsed cluster pendants wrap around the backbone. The collapse occurs because they become less soluble in the solvent/non-solvent mixture. The extended chains then become entwined and form nanoropes consisting of multiple chains wound around each other. This study provides a deeper understanding of the nature of polyclusters and should also prove useful for their future development and application.  相似文献   
49.
50.
The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films were investigated using a number of techniques. A high saturation magnetic induction up to B s = 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed, which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of the composition. The text was submitted by the authors in English.  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