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   144532篇
  免费   27742篇
  国内免费   12912篇
化学   112990篇
晶体学   1608篇
力学   7964篇
综合类   697篇
数学   15533篇
物理学   46394篇
  2024年   259篇
  2023年   2282篇
  2022年   2642篇
  2021年   4020篇
  2020年   5560篇
  2019年   6500篇
  2018年   4615篇
  2017年   4020篇
  2016年   8391篇
  2015年   8214篇
  2014年   9364篇
  2013年   11828篇
  2012年   12753篇
  2011年   12617篇
  2010年   9665篇
  2009年   9299篇
  2008年   9366篇
  2007年   8207篇
  2006年   7355篇
  2005年   6579篇
  2004年   5092篇
  2003年   4241篇
  2002年   4719篇
  2001年   3678篇
  2000年   3268篇
  1999年   2713篇
  1998年   2161篇
  1997年   1980篇
  1996年   2165篇
  1995年   1744篇
  1994年   1666篇
  1993年   1336篇
  1992年   1210篇
  1991年   1113篇
  1990年   895篇
  1989年   649篇
  1988年   535篇
  1987年   432篇
  1986年   404篇
  1985年   372篇
  1984年   281篇
  1983年   175篇
  1982年   160篇
  1981年   121篇
  1980年   88篇
  1979年   47篇
  1978年   37篇
  1976年   38篇
  1975年   33篇
  1974年   46篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Ding  Hao  Wang  Jin-Ting  Lu  Li-Qiao  Pan  Jian-Wen 《Nonlinear dynamics》2021,104(4):3365-3384
Nonlinear Dynamics - Conventional tuned liquid column dampers (TLCDs) are deficient in multidirectionality. In contrast, toroidal TLCDs are designed to extend the application to multidirectional...  相似文献   
102.
Acta Mathematica Sinica, English Series - We are interested in the existence and asymptotic behavior for the least energy solutions of the following fractional eigenvalue problem $$\left({\rm{P}}...  相似文献   
103.
Let L be an additive map between (real or complex) matrix algebras sending n×n Hermitian idempotent matrices to m×m Hermitian idempotent matrices. We show that there are nonnegative integers p,q with n(p+q)=rm and an m×m unitary matrix U such thatL(A)=U[(Ip?A)(Iq?At)0m?r]U?,for any n×n Hermitian A with rational trace. We also extend this result to the (complex) von Neumann algebra setting, and provide a supplement to the Dye-Bunce-Wright Theorem asserting that every additive map of Hermitian idempotents extends to a Jordan ?-homomorphism.  相似文献   
104.
Journal of Radioanalytical and Nuclear Chemistry - In the present work the final products of coumarin radiation chemical transformation are investigated by chromatography. During radiolysis of...  相似文献   
105.
106.
Exosomes are nanovesicles secreted by most cellular types that carry important biochemical compounds throughout the body with different purposes, playing a preponderant role in cellular communication. Because of their structure, physicochemical properties and stability, recent studies are focusing in their use as nanocarriers for different therapeutic compounds for the treatment of different diseases ranging from cancer to Parkinson's disease. However, current bioseparation protocols and methodologies are selected based on the final exosome application or intended use and present both advantages and disadvantages when compared among them. In this context, this review aims to present the most important technologies available for exosome isolation while discussing their advantages and disadvantages and the possibilities of being combined with other strategies. This is critical since the development of novel exosome‐based therapeutic strategies will be constrained to the effectiveness and yield of the selected downstream purification methodologies for which a thorough understanding of the available technological resources is needed.  相似文献   
107.
108.
We report theoretical studies of electron impact triple differential cross sections of two bio-molecules,pyrimidine and tetrahydrofurfuryl alcohol,in the coplanar asymmetric kinematic conditions with the impact energy of 250 eV and ejected electron energy of 20 eV at three scattering angles of-5°,-10°,and-15°.Present multi-center distorted-wave method well describes the experimental data,which was obtained by performing(e,2e)experiment.The calculations show that the secondary electron produced by the primary impact electron is strongly influenced by the molecular ionic multi-center potential,which must be considered when the low energy electron interacts with DNA analogues.  相似文献   
109.
Journal of Thermal Analysis and Calorimetry - The fire behavior of one flame-retardant PVC cable used as building wire is investigated in this work. Bench scale tests were performed using a cone...  相似文献   
110.
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