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   32285篇
  免费   710篇
  国内免费   823篇
化学   13154篇
晶体学   299篇
力学   1575篇
综合类   55篇
数学   9405篇
物理学   9330篇
  2023年   71篇
  2022年   122篇
  2021年   145篇
  2020年   176篇
  2019年   165篇
  2018年   1327篇
  2017年   1550篇
  2016年   857篇
  2015年   717篇
  2014年   640篇
  2013年   879篇
  2012年   3392篇
  2011年   2606篇
  2010年   2015篇
  2009年   1728篇
  2008年   808篇
  2007年   768篇
  2006年   768篇
  2005年   4590篇
  2004年   4049篇
  2003年   2432篇
  2002年   657篇
  2001年   439篇
  2000年   197篇
  1999年   264篇
  1998年   186篇
  1997年   120篇
  1996年   143篇
  1995年   117篇
  1994年   97篇
  1993年   55篇
  1992年   203篇
  1991年   182篇
  1990年   163篇
  1989年   122篇
  1988年   112篇
  1987年   72篇
  1986年   51篇
  1985年   52篇
  1984年   32篇
  1979年   31篇
  1976年   79篇
  1975年   37篇
  1974年   41篇
  1973年   48篇
  1972年   39篇
  1970年   34篇
  1969年   37篇
  1968年   35篇
  1966年   37篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Embedding endohdedral metallofullerenes (EMFs) into electron donor–acceptor systems is still a challenging task owing to their limited quantities and their still largely unexplored chemical properties. In this study, we have performed a 1,3‐dipolar cycloaddition reaction of a corrole‐based precursor with Sc3N@C80 to regioselectively form a [5,6]‐adduct ( 1 ). The successful attachment of the corrole moiety was confirmed by mass spectrometry. In the electronic ground state, absorption spectra suggest sizeable electronic communications between the electron acceptor and the electron donor. Moreover, the addition pattern occurring at a [5,6]‐bond junction is firmly proven by NMR spectroscopy and electrochemical investigations performed with 1 . In the electronically excited state, which is probed in photophysical assays with 1 , a fast electron‐transfer yields the radical ion pair state consisting of the one‐electron‐reduced Sc3N@C80 and of the one‐electron‐oxidized corrole upon its exclusive photoexcitation. As such, our results shed new light on the practical work utilizing EMFs as building blocks in photovoltaics.  相似文献   
2.
Set-Valued and Variational Analysis - We aim to establish Karush-Kuhn-Tucker multiplier rules involving higher-order complementarity slackness under Hölder metric subregularity. These rules...  相似文献   
3.
4.
5.
A new solvent-free sample preparation method using silver trifluoroacetate (AgTFA) was developed for the analysis of low molecular weight paraffins and microcrystalline waxes by laser desorption/ionization time-of-flight mass spectrometry (LDI-TOFMS). Experiments show that spectral quality can be enhanced by dispersing AgTFA directly in liquid paraffins without the use of additional solvents. This preparation mixture is applied directly to the MALDI probe. Solid waxes could be examined by melting prior to analysis. The method also provides sufficiently reproducible spectra that peak area ratios between mono- and bicyclic alkane peaks indicated variations in the cycloalkane content of paraffin samples. Dehydrogenation of hydrocarbons observed during the desorption/ionization process was studied by analysis of alkane standards.  相似文献   
6.
This paper reports that the growth of RuOx(110) thin layer growth on Ru(0001) has been investigated by means of scanning tunnelling microscope (STM). The STM images showed a domain structure with three rotational domains of RuOx(110) rotated by an angle of 120℃. The as-grown RuOx(110) thin layer is expanded from the bulk-truncated RuOx(110) due to the large mismatch between RuOx(110) and the Ru(0001) substrate. The results also indicate that growth of RuOx(110) thin layer on the Ru(0001) substrate by oxidation tends first to formation of the Ru-O (oxygen) chains in the [001] direction of RuOx(110).  相似文献   
7.
The versatile behavior of a trihydrazidophosphoradamantane allowing the synthesis of a variety of neutral, mono- or di-cationic water-soluble molecules of potential interest for biphasic catalysis is reported.  相似文献   
8.
In this paper we construct an example of a word metric on an infinite cyclic subgroup. This example shows that subexponential distortion does not obstruct non-trivial growth of connected radii. This answers a question of Gromov [6]. The constructed metric has other pathological properies. Specifically, its asymptotic cone depends on the choice of ultrafilter and scaling sequence. The work has been partially supported by the Swiss National Science Foundation.  相似文献   
9.
We build a metric space which is homeomorphic to a Cantor set but cannot be realized as the attractor of an iterated function system. We give also an example of a Cantor set K in R3 such that every homeomorphism f of R3 which preserves K coincides with the identity on K.  相似文献   
10.
A criterion for the nonexplosion of solutions to semilinear evolution equations on Banach spaces is proved. The result is obtained by applying a modification of the Bihari type inequality to the case of a weakly singular nonlinear integral inequality.  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