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   362526篇
  免费   2167篇
  国内免费   1024篇
化学   162780篇
晶体学   4480篇
力学   20061篇
综合类   6篇
数学   72745篇
物理学   105645篇
  2020年   2022篇
  2019年   2370篇
  2018年   18941篇
  2017年   19347篇
  2016年   12657篇
  2015年   3847篇
  2014年   4268篇
  2013年   9769篇
  2012年   13620篇
  2011年   27370篇
  2010年   16678篇
  2009年   17071篇
  2008年   22581篇
  2007年   27417篇
  2006年   8098篇
  2005年   13983篇
  2004年   10507篇
  2003年   10454篇
  2002年   7714篇
  2001年   6333篇
  2000年   5250篇
  1999年   3644篇
  1998年   3235篇
  1997年   3201篇
  1996年   3134篇
  1995年   2531篇
  1994年   2565篇
  1993年   2612篇
  1992年   2710篇
  1991年   2784篇
  1990年   2670篇
  1989年   2657篇
  1988年   2545篇
  1987年   2527篇
  1986年   2423篇
  1985年   3109篇
  1984年   3280篇
  1983年   2633篇
  1982年   2904篇
  1981年   2787篇
  1980年   2598篇
  1979年   2824篇
  1978年   2947篇
  1977年   2883篇
  1976年   2874篇
  1975年   2724篇
  1974年   2692篇
  1973年   2890篇
  1972年   1902篇
  1967年   1876篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
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   
42.
43.
Russian Chemical Bulletin - Quantum chemical calculations and a comparative analysis of Raman spectra of 3,4,5-triphenyl-1-propyl-1,2-diphosphole (1),...  相似文献   
44.
45.
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   
46.
Development of biocompatible porous supports is a promising strategy in the field of tissue engineering for the repair and regeneration of bone tissues with severe damage. Graphene oxide aerogels (GOAs) are excellent candidates for the manufacture of these systems due to their porosity, ability to imitate bone structure, and mechanical resistance, and according to their surface chemical reactivity, they can facilitate osseointegration, osteogenesis, osteoinduction and osteoconduction. In this review, synthesis of GOAs from the most primary source is described, and recent studies on the use of these functionalized carbonaceous foams as scaffolding for bone tissue regeneration are presented.  相似文献   
47.
Russian Journal of General Chemistry - Some new fluoro-heterocyclic compounds containing thiazole and pyridine moities have been synthesized and studied for their antiproliferative activity....  相似文献   
48.
49.
Applied Magnetic Resonance - The suggested approach allowed us to derive analytical expressions for modeling the shape of solid-echo signal and its time evolution for a system of three-spin groups...  相似文献   
50.
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