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   324688篇
  免费   2263篇
  国内免费   821篇
化学   147112篇
晶体学   5149篇
力学   17279篇
综合类   1篇
数学   49126篇
物理学   109105篇
  2020年   1787篇
  2019年   2045篇
  2018年   10959篇
  2017年   11718篇
  2016年   7695篇
  2015年   3200篇
  2014年   4081篇
  2013年   10184篇
  2012年   11638篇
  2011年   21191篇
  2010年   13454篇
  2009年   13478篇
  2008年   18640篇
  2007年   22025篇
  2006年   8439篇
  2005年   13799篇
  2004年   10067篇
  2003年   9356篇
  2002年   7414篇
  2001年   7240篇
  2000年   5668篇
  1999年   4274篇
  1998年   3609篇
  1997年   3493篇
  1996年   3465篇
  1995年   3109篇
  1994年   3038篇
  1993年   3123篇
  1992年   3225篇
  1991年   3409篇
  1990年   3155篇
  1989年   3103篇
  1988年   3159篇
  1987年   3043篇
  1986年   2875篇
  1985年   3897篇
  1984年   4108篇
  1983年   3291篇
  1982年   3497篇
  1981年   3420篇
  1980年   3315篇
  1979年   3440篇
  1978年   3495篇
  1977年   3355篇
  1976年   3490篇
  1975年   3159篇
  1974年   3168篇
  1973年   3253篇
  1972年   2254篇
  1971年   1859篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
Suetin  S. P. 《Mathematical Notes》2019,106(5-6):970-979
Mathematical Notes - We prove the equivalence of a vector and a scalar equilibrium problem that naturally arise when studying the limit distribution of zeros of type I Hermite–Padé...  相似文献   
112.
Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques - A method for studying the magnetic dynamics of endofullerenes M@C2n (2n = 60, 70, …) and their derivatives,...  相似文献   
113.
114.
115.
Siberian Mathematical Journal - Under study are the right-symmetric algebras over a field  $ F $ which possess a “unital” matrix subalgebra  $...  相似文献   
116.
Journal of Applied Spectroscopy - The temperature dependence of the refractive indices of K2SO4 with copper impurity was investigated. It was found that introduction of the copper impurity leads to...  相似文献   
117.
The natural product lupeol 1 was isolated from aerial parts of Vernonia scorpioides with satisfactory yield, which made it viable to be used as starting material in semisynthetic approach. Ten lupeol derivatives 2–11 were prepared by classical procedures. Including, five new esters derivatives 7–11, which were obtained by structural modifications in the isopropylidene fragment. All semisynthetic compounds and lupeol 1–11 were confirmed by 1H NMR, 13C NMR and HRMS. Their antiprotozoal activity was evaluated in vitro against L. amazonensis and T. cruzi. Derivative 6 showed the best antitrypanosomal activity (IC50 = 12.48 μg/mL) and the lowest cytotoxic derivative (CC50 = 161.50 μg/mL). The mechanism of action of the most active derivatives (4, 6 and 11) is not dependent from the enzyme trypanothione reductase.  相似文献   
118.
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   
119.
Methods for phase stabilization of ammonium nitrate were sought for in order to considerably expand the application area of this oxidizing agent in various-purpose self-combustible formulations, including that in a new generation of gas-generating formulations for automobile air bags. New methods for stabilization of ammonium nitrate were studied and, in particular, a search was made for organic compounds that can stabilize ammonium nitrate even at their low content. The mechanism of phase state stabilization of ammonium nitrate by compounds of this kind was examined.  相似文献   
120.
Kinetic, sorption and selectivity properties of commercial adsorbents are improved by adding petroleum residues (tar asphaltene concentrates) 13% of whole mass. Obtained adsorbents can be used for selective extraction of nobel metals from multicomponent polymetallic solutions of heavy metals and fro sewages purification for removing arsenic.  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