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   312494篇
  免费   4353篇
  国内免费   2078篇
化学   173041篇
晶体学   3356篇
力学   12800篇
综合类   18篇
数学   37572篇
物理学   92138篇
  2020年   2842篇
  2019年   3128篇
  2018年   4103篇
  2017年   4050篇
  2016年   6322篇
  2015年   4106篇
  2014年   5837篇
  2013年   14063篇
  2012年   11569篇
  2011年   13576篇
  2010年   9293篇
  2009年   9109篇
  2008年   12307篇
  2007年   12426篇
  2006年   11442篇
  2005年   10520篇
  2004年   9923篇
  2003年   8441篇
  2002年   7740篇
  2001年   8055篇
  2000年   6235篇
  1999年   4714篇
  1998年   4127篇
  1997年   4066篇
  1996年   3911篇
  1995年   3665篇
  1994年   3823篇
  1993年   3535篇
  1992年   3965篇
  1991年   3892篇
  1990年   3820篇
  1989年   3642篇
  1988年   3700篇
  1987年   3640篇
  1986年   3427篇
  1985年   4635篇
  1984年   4894篇
  1983年   4047篇
  1982年   4152篇
  1981年   4097篇
  1980年   4042篇
  1979年   4006篇
  1978年   4309篇
  1977年   4224篇
  1976年   4267篇
  1975年   3943篇
  1974年   3973篇
  1973年   4142篇
  1972年   2894篇
  1971年   2425篇
排序方式: 共有10000条查询结果,搜索用时 109 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.
Physics of the Solid State - Using the X-ray diffraction and electron microscopy methods, the structure and the elemental and phase compositions of hypereutectic alloy Al86Ni2Co6Gd6 (hereinafter,...  相似文献   
6.
Russian Physics Journal - Aiming at problems of low probability of interception and poor anti-jamming performance of the multi-output radar, the numerical simulation based on a chaos optimization...  相似文献   
7.
Physics of the Solid State - The phase transitions in the two-dimensional diluted Potts model with the number of spin states q = 3 are studied by computer simulation method. The systems...  相似文献   
8.
Journal of Analytical Chemistry - The work is dedicated to the determination of polyaromatic hydrocarbons (PAHs) in soils and bottom sediments by gas chromatography–mass spectrometry using...  相似文献   
9.
Statistical Inference for Stochastic Processes - The class of autoregressive (AR) processes is extensively used to model temporal dependence in observed time series. Such models are easily...  相似文献   
10.
Journal of Applied Spectroscopy - IR reflectance spectroscopy at 50–450 cm–1 was used to study homogeneous monocrystals of (FeIn2S3)x?(In2S3)1–x grown by the method 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