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   281822篇
  免费   4343篇
  国内免费   1089篇
化学   152432篇
晶体学   3896篇
力学   11131篇
综合类   13篇
数学   34202篇
物理学   85580篇
  2020年   2331篇
  2019年   2488篇
  2018年   3087篇
  2017年   2983篇
  2016年   5022篇
  2015年   3542篇
  2014年   4950篇
  2013年   13333篇
  2012年   10072篇
  2011年   12112篇
  2010年   7943篇
  2009年   7632篇
  2008年   10906篇
  2007年   11004篇
  2006年   10122篇
  2005年   9411篇
  2004年   8333篇
  2003年   7318篇
  2002年   7127篇
  2001年   7931篇
  2000年   5983篇
  1999年   4691篇
  1998年   3926篇
  1997年   3939篇
  1996年   3765篇
  1995年   3546篇
  1994年   3399篇
  1993年   3474篇
  1992年   3788篇
  1991年   3637篇
  1990年   3468篇
  1989年   3412篇
  1988年   3434篇
  1987年   3323篇
  1986年   3177篇
  1985年   4441篇
  1984年   4561篇
  1983年   3749篇
  1982年   4122篇
  1981年   4022篇
  1980年   3897篇
  1979年   3909篇
  1978年   4107篇
  1977年   3942篇
  1976年   4142篇
  1975年   3706篇
  1974年   3833篇
  1973年   4077篇
  1972年   2461篇
  1971年   1936篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
31.
32.
A generic strategy based on the use of CdSe/ZnS Quantum Dots (QDs) as elemental labels for protein quantification, using immunoassays with elemental mass spectrometry (ICP-MS), detection is presented. In this strategy, streptavidin modified QDs (QDs-SA) are bioconjugated to a biotinylated secondary antibody (b-Ab2). After a multi-technique characterization of the synthesized generic platform (QDs-SA-b-Ab2) it was applied to the sequential quantification of five proteins (transferrin, complement C3, apolipoprotein A1, transthyretin and apolipoprotein A4) at different concentration levels in human serum samples. It is shown how this generic strategy does only require the appropriate unlabeled primary antibody for each protein to be detected. Therefore, it introduces a way out to the need for the cumbersome and specific bioconjugation of the QDs to the corresponding specific recognition antibody for every target analyte (protein). Results obtained were validated with those obtained using UV–vis spectrophotometry and commercial ELISA Kits.  相似文献   
33.
34.
35.
The results of investigation of optical image detectors designed for the largest problem, near-VUV, range of the spectrum are presented. The possibility of using a dual-stage image detection system to appreciably lower the sensitivity threshold and make computer data processing feasible is considered. The integration of a UV module into a wideband image detector is studied.  相似文献   
36.
37.
Two new compounds of fluorine: (C2H5)4N[I2F] and (C2H5)4N[Br2F], have been easily synthesized in a nearly quantitative by a direct reaction of (C2H5)4NF, I2 and Br2. The products were isolated and characterized by elemental analysis and spectroscopic methods such as: Fourier transform infrared spectroscopy (FTIR) and ultraviolet-visible spectroscopy (UV-Vis). These compounds have been studied computationally with the Scalar ZORA relativistic level of theory using the ADF program package. The molecular parameters, and vibrational spectra were calculated. The excitation energies were found by timedependent perturbation density functional theory (TD-DFT). Molecule optimization, frequencies and excitation energies were calculated with standard Slatertype-orbital (STO) basis sets with triple-zeta quality double plus polarization functions (TZ2P) for all atoms. The FTIR, UV-Vis spectra and assignment of principal transitions and total density of state (TDOS) were extracted using the GaussSum 2.2 program. The comparison between experimental and calculated values showes that the experimental results correlate well with the predicted data.  相似文献   
38.
Journal of Sol-Gel Science and Technology - Multifunctional magnetic mesoporous nanocomposites are promising materials to remove the various pollutants from water due to the remarkable properties...  相似文献   
39.
Russian Journal of Organic Chemistry - Binder-free iron- and nickel-containing micro-, meso-, and macroporous zeolites FeHY and NiHY were found to effectively catalyze Knoevenagel condensation of...  相似文献   
40.
Russian Journal of Organic Chemistry - Herein, we report the sulfonamide-functionalized covalent organic framework (COF-SO3H), prepared by condensation of melamine and terephthalaldehyde and...  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