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   131464篇
  免费   2165篇
  国内免费   494篇
化学   57314篇
晶体学   1056篇
力学   7635篇
综合类   3篇
数学   41746篇
物理学   26369篇
  2023年   388篇
  2022年   340篇
  2021年   695篇
  2020年   863篇
  2019年   813篇
  2018年   11454篇
  2017年   11078篇
  2016年   7816篇
  2015年   2397篇
  2014年   1925篇
  2013年   3868篇
  2012年   7005篇
  2011年   13395篇
  2010年   7587篇
  2009年   7694篇
  2008年   9266篇
  2007年   11177篇
  2006年   2710篇
  2005年   3705篇
  2004年   3543篇
  2003年   3648篇
  2002年   2460篇
  2001年   1373篇
  2000年   1423篇
  1999年   957篇
  1998年   785篇
  1997年   680篇
  1996年   889篇
  1995年   615篇
  1994年   672篇
  1993年   616篇
  1992年   604篇
  1991年   526篇
  1990年   569篇
  1989年   486篇
  1988年   481篇
  1987年   433篇
  1986年   431篇
  1985年   571篇
  1984年   537篇
  1983年   417篇
  1982年   440篇
  1981年   449篇
  1980年   376篇
  1979年   358篇
  1978年   367篇
  1977年   328篇
  1976年   344篇
  1975年   295篇
  1973年   318篇
排序方式: 共有10000条查询结果,搜索用时 46 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.
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