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   47645篇
  免费   1567篇
  国内免费   40篇
化学   29050篇
晶体学   251篇
力学   785篇
数学   8961篇
物理学   10205篇
  2023年   336篇
  2022年   286篇
  2021年   512篇
  2020年   713篇
  2019年   665篇
  2018年   958篇
  2017年   879篇
  2016年   1720篇
  2015年   1420篇
  2014年   1397篇
  2013年   3096篇
  2012年   2955篇
  2011年   2809篇
  2010年   1869篇
  2009年   1622篇
  2008年   2416篇
  2007年   2217篇
  2006年   1986篇
  2005年   2029篇
  2004年   1752篇
  2003年   1456篇
  2002年   1264篇
  2001年   994篇
  2000年   976篇
  1999年   689篇
  1998年   528篇
  1997年   445篇
  1996年   607篇
  1995年   432篇
  1994年   507篇
  1993年   452篇
  1992年   482篇
  1991年   415篇
  1990年   466篇
  1989年   374篇
  1988年   380篇
  1987年   340篇
  1986年   327篇
  1985年   456篇
  1984年   420篇
  1983年   336篇
  1982年   333篇
  1981年   354篇
  1980年   280篇
  1979年   275篇
  1978年   272篇
  1977年   264篇
  1976年   278篇
  1974年   254篇
  1973年   264篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
This work demonstrates the analytical applicability of single ion-selective membranes (ISMs) and potentiometric sensor array to distinguish and detect cathinone derivatives. Potentiometric data from ISMs based on cation exchanger and varying content of calix[4]arene derivative were processed by principal component analysis (PCA). Such a combination of methods allowed discriminating various individual synthetic cathinones and their recognition from the mixture comprising primary amines (substituted amphetamines+aminoindane). Analytical parameters of ISM containing 1wt % of calix[4]arene derivative were sufficient to detect 1.0×10−4 mol.l−1 1-(4-fluorophenyl)-2-(ethylamino)butan-1-one and 2-(methylamino)-1-phenylbutan-1-one (buphedrone) in both model and saliva samples.  相似文献   
3.
This work describes the basic principles of Total-reflection X-Ray Fluorescence (TXRF) spectrometry and some of its most outstanding applications for investigating metal traces, mainly in biological and biomedical samples. TXRF is an analytical technique that combines the versatility of elemental analysis by X-ray energy dispersion with a low detection limit in the order of picograms of absolute mass or a few ppb (μg L−1) as concentration. The microanalytical capacity of TXRF allows the study of small sample quantities. The TXRF can perform qualitative and mass ratio analyses of the elements present in a sample of only a few hundred nanograms. These properties are of great importance in the research of metal traces in biological systems, as they allow fast, precise, and accurate characterisation of the elemental fingerprint at trace level. Its successful application in studies of the coordination kinetics of new platinum-based antitumor drugs with DNA, its application in the study profile of the metal in healthy and cancerous human tissues, or even its application in the study of the processes of metal diffusion through cell membranes are just a few examples of TXRF capabilities in the biomedical sciences. This brief review's main objective is to provide an overview of the physical principles and possibilities of TXRF spectrometry. It also highlights some of the most outstanding applications that have been developed so far, mainly in the biological field, so that the reader can evaluate their potential applications.  相似文献   
4.
Journal of Solid State Electrochemistry - The addition of nanocrystalline titanium dioxide (P90) to a cathode of Li/S cell enhances its voltammetric charge capacity by 19%, from which only a small...  相似文献   
5.
Fuzzy Optimization and Decision Making - Cost-allocation problems in a fixed network are concerned with distributing the costs for use by a group of clients who cooperate in order to reduce such...  相似文献   
6.
7.
This review summarizes recent progress in understanding the oxygen reduction and evolution reactions at the lanthanum strontium manganite electrode of a high-temperature solid oxide cell. Information provided here is put into the perspective of the defect chemistry of lanthanum strontium manganite and its impact on the electrode reaction mechanisms itself. After summarizing recent views on the oxygen reduction reaction mechanism, the focus turns to the oxygen evolution reaction, which is significantly less treated in the literature. A combination of the information in the literature on both reactions was the basis for modified reaction mechanism of the oxygen evolution reaction to be proposed under consideration of recent experimental observations and theoretical findings.  相似文献   
8.
9.
10.
Geometriae Dedicata - We prove a criterion for Benjamini-Schramm convergence of periodic orbits of Lie groups. This general observation is then applied to homogeneous spaces and the space 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