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   59918篇
  免费   10638篇
  国内免费   13047篇
化学   43442篇
晶体学   1431篇
力学   3851篇
综合类   1215篇
数学   7959篇
物理学   25705篇
  2024年   173篇
  2023年   985篇
  2022年   2149篇
  2021年   2212篇
  2020年   2318篇
  2019年   2258篇
  2018年   1981篇
  2017年   2209篇
  2016年   2527篇
  2015年   2877篇
  2014年   3469篇
  2013年   4517篇
  2012年   5060篇
  2011年   5296篇
  2010年   4261篇
  2009年   4315篇
  2008年   4638篇
  2007年   4280篇
  2006年   4093篇
  2005年   3454篇
  2004年   2750篇
  2003年   2067篇
  2002年   2086篇
  2001年   1911篇
  2000年   1887篇
  1999年   1484篇
  1998年   1053篇
  1997年   918篇
  1996年   906篇
  1995年   787篇
  1994年   762篇
  1993年   693篇
  1992年   568篇
  1991年   438篇
  1990年   428篇
  1989年   368篇
  1988年   270篇
  1987年   203篇
  1986年   201篇
  1985年   156篇
  1984年   123篇
  1983年   96篇
  1982年   101篇
  1981年   71篇
  1980年   33篇
  1979年   43篇
  1978年   20篇
  1976年   10篇
  1974年   13篇
  1965年   12篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
Let p ∈ [1, ∞), q ∈ [1, ∞), α∈ R, and s be a non-negative integer. Inspired by the space JNp introduced by John and Nirenberg(1961) and the space B introduced by Bourgain et al.(2015), we introduce a special John-Nirenberg-Campanato space JNcon(p,q,s) over Rn or a given cube of R;with finite side length via congruent subcubes, which are of some amalgam features. The limit space of such spaces as p →∞ is just the Campanato space which coincides with the space BMO(the space of functions with bounded mean oscillations)when α = 0. Moreover, a vanishing subspace of this new space is introduced, and its equivalent characterization is established as well, which is a counterpart of the known characterization for the classical space VMO(the space of functions with vanishing mean oscillations) over Rn or a given cube of Rn with finite side length.Furthermore, some VMO-H1-BMO-type results for this new space are also obtained, which are based on the aforementioned vanishing subspaces and the Hardy-type space defined via congruent cubes in this article. The geometrical properties of both the Euclidean space via its dyadic system and congruent cubes play a key role in the proofs of all these results.  相似文献   
2.
3.
4.
在中国科学技术大学夏季学期的研究型实验课程"化学科研基础训练"中开设"壳聚糖的制备与表征"综合实验,以龙虾壳为原料,通过除蛋白、脱盐、脱色、脱乙酰等一系列反应,制备得到目标产物壳聚糖。运用红外光谱、核磁共振仪、黏度法、滴定等对产品的结构及性能进行表征。  相似文献   
5.
6.
This study is concerned with a new,explicit approach by means of which forms of the large strain elastic potential for multiaxial rubberlike elasticity may be obtained based on data for a single deformation mode.As a departure from usual studies,here for the first time errors may be estimated and rendered minimal for all possible deformation modes and,furthermore,failure behavior may be incorporated.Numerical examples presented are in accurate agreement with Treloar's well-known data.  相似文献   
7.
8.
Bulleyaconitine A (BLA) from Aconitum bulleyanum plants is usually used as anti‐inflammatory drug in some Asian countries. It has a variety of bioactivities, and at the same time some toxicities. Since the bioactivities and toxicities of BLA are closely related to its metabolism, the metabolites and the metabolic pathways of BLA in rat liver microsomes were investigated by HPLC–MSn. In this research, the 12 metabolites of BLA were identified according to the results of HPLC‐MSn data and the relevant literature. The results showed that there are multiple metabolites of BLA in rat liver microsomes, including demethylation, deacetylation, dehydrogenation deacetylation and hydroxylation. The major metabolic pathways of BLA in rat liver microsomes were clarified by HPLC‐MS combined with specific inhibitors of CYP450 isoforms. As a result, CYP3A and 2C were found to be the principal CYP isoforms contributing to the metabolism of BLA. Moreover, CYP2D6 and 2E1 are also more important CYP isoforms for the metabolism of BLA. While CYP1A2 only affected the formation rate of M11, its effect on the metabolism of BLA is very small. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
9.
A new A, D-seco limonoid, named 12-acetyloxyperforatin (1), along with three known ones, were isolated from the leaves of Harrisonia perforata. Their structures were elucidated on the basis of spectroscopic analysis, including extensive NMR techniques and computational modelling. These compounds showed no inhibitory activity against the 11β-HSD1 enzyme.  相似文献   
10.
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   
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