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   155779篇
  免费   28403篇
  国内免费   13884篇
化学   120339篇
晶体学   1774篇
力学   8501篇
综合类   753篇
数学   16968篇
物理学   49731篇
  2024年   273篇
  2023年   2387篇
  2022年   3470篇
  2021年   4359篇
  2020年   5762篇
  2019年   6683篇
  2018年   4832篇
  2017年   4342篇
  2016年   8648篇
  2015年   8521篇
  2014年   9667篇
  2013年   12472篇
  2012年   13461篇
  2011年   13519篇
  2010年   10254篇
  2009年   9986篇
  2008年   10123篇
  2007年   8949篇
  2006年   7977篇
  2005年   7099篇
  2004年   5471篇
  2003年   4518篇
  2002年   4922篇
  2001年   3814篇
  2000年   3420篇
  1999年   2897篇
  1998年   2322篇
  1997年   2148篇
  1996年   2322篇
  1995年   1865篇
  1994年   1794篇
  1993年   1484篇
  1992年   1357篇
  1991年   1245篇
  1990年   1022篇
  1989年   745篇
  1988年   624篇
  1987年   501篇
  1986年   501篇
  1985年   461篇
  1984年   335篇
  1983年   214篇
  1982年   209篇
  1981年   162篇
  1980年   126篇
  1979年   101篇
  1978年   72篇
  1976年   72篇
  1974年   86篇
  1973年   75篇
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
101.
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   
102.
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   
103.
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   
104.
105.
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   
106.
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   
107.
Zhang  Jia-Rui  Zhang  Jia-Qi  Zheng  Zhao-Lin  Lin  Da  Shen  Yu-Jia 《Nonlinear dynamics》2022,108(2):1005-1026
Nonlinear Dynamics - Parametrically excited oscillators are used in several domains, in particular to improve the dynamical behaviour of systems like in the case of the parametric amplification or...  相似文献   
108.
109.
110.
Triazines are widely used in agriculture around the world as selective pre‐ and post‐emergence herbicides for the control of broad leaf and grassy weeds. With high toxicity and persistence, triazines can contaminate the environment and crops, so the development of rapid and sensitive methods for the determination of different triazines is necessary. Capillary electrophoresis comprises a group of techniques used to separate chemical mixtures. Analytical separation is based on different electrophoretic mobilities. This review focuses on the analysis of triazine herbicides with different modes of capillary electrophoresis, including capillary zone electrophoresis, micellar electrokinetic capillary electrophoresis, capillary electrochromatography and nonaqueous capillary electrophoresis. Determinations of triazines in various matrices such as surface water, groundwater, vegetables, soil and grains are emphasized. Copyright © 2014 John Wiley & Sons, Ltd.  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