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   329590篇
  免费   4660篇
  国内免费   2464篇
化学   151595篇
晶体学   5073篇
力学   18713篇
综合类   81篇
数学   58771篇
物理学   102481篇
  2021年   2073篇
  2020年   2332篇
  2019年   2540篇
  2018年   13236篇
  2017年   12935篇
  2016年   10457篇
  2015年   3779篇
  2014年   5031篇
  2013年   11683篇
  2012年   12714篇
  2011年   21210篇
  2010年   13334篇
  2009年   13696篇
  2008年   16377篇
  2007年   18384篇
  2006年   9707篇
  2005年   9720篇
  2004年   9215篇
  2003年   8715篇
  2002年   7645篇
  2001年   8226篇
  2000年   6349篇
  1999年   5023篇
  1998年   4209篇
  1997年   4071篇
  1996年   3902篇
  1995年   3477篇
  1994年   3345篇
  1993年   3381篇
  1992年   3451篇
  1991年   3599篇
  1990年   3335篇
  1989年   3241篇
  1988年   3256篇
  1987年   3128篇
  1986年   2940篇
  1985年   3949篇
  1984年   4109篇
  1983年   3275篇
  1982年   3485篇
  1981年   3404篇
  1980年   3293篇
  1979年   3392篇
  1978年   3470篇
  1977年   3385篇
  1976年   3483篇
  1975年   3177篇
  1974年   3179篇
  1973年   3234篇
  1972年   2261篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
113.
We give the form of the output function in Ginsburg’s machine in which the input and output dictionaries are abelian groups and the transition function is of a special form.  相似文献   
114.
Shi  D.  Feng  J.  Wang  J.  Zhao  W.  Li  X. 《Kinetics and Catalysis》2020,61(5):750-757
Kinetics and Catalysis - A series of Cu-SSZ-13@CeO2 catalysts with surface modification with CeO2 was prepared by the modified self-resemble method based on the one-pot synthesized Cu-SSZ-13...  相似文献   
115.
116.
Radiophysics and Quantum Electronics - We propose and experimentally test a numerical method for correction of the influence of fluctuations in the distance to objects during noncontact probing in...  相似文献   
117.
The aim of the study presented in this paper was to characterize quantitatively the erosion of aluminum cathodes in high-current vacuum arcs. The experimental setup comprised two current generators. The first one, capable of generating a current of amplitude up to 350 kA, was used to produce a plasma jet, that is, the object to be investigated. The second generator was used to produce a source of probe radiation for imaging the object under investigation in soft x rays of energy ?ν ≈ 0.5–3 keV. The findings of the study are based on experimental data obtained by electrophysical and radiographic methods. It has been shown that the cathode erosion rate in a high-current vacuum arc is a function of the charge passed through the cathode.  相似文献   
118.
119.
New aromatic (co)polyesters containing pendant propargyloxy groups were synthesized by phase transfer‐catalyzed interfacial polycondensation of 5‐(propargyloxy)isophthaloyl chloride (P‐IPC) and various compositions of P‐IPC and isophthaloyl chloride with bisphenol A. FTIR and NMR spectroscopic data, respectively, revealed successful incorporation of pendant propargyloxy groups into (co)polyesters and formation of (co)polyesters with desired compositions. (Co)polyesters exhibited good solubility in common organic solvents such as chloroform, dichloromethane, and tetrahydrofuran and could be cast into transparent, flexible, and tough films from chloroform solution. Inherent viscosities and number average molecular weights of (co)polyesters were in the range 0.77–1.33 dL/g and 43,600–118,000 g/mol, respectively, indicating the achievement of reasonably high‐molecular weights. The 10% weight loss temperatures of (co)polyesters were in the range 390–420 °C, demonstrating their good thermal stability. (Co)polyesters exhibited Tg in the range 146–170 °C and Tg values decreased with increase in mol % incorporation of P‐IPC. The study of non‐isothermal curing by DSC indicated thermal crosslinking of (co)polyesters via propargyloxy groups. The utility of pendant propargyloxy group was demonstrated by post‐modification of the selected copolyester with 1‐(4‐azidobutyl)pyrene, 9‐(azidomethyl)anthracene, and azido‐terminated poly(ethyleneglycol) monomethyl ether via copper(I)‐catalyzed Huisgen 1,3‐dipolar cycloaddition reaction. FTIR and 1H NMR spectra confirmed that click reaction was quantitative. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 588–597  相似文献   
120.
Physics of Particles and Nuclei Letters - The Silicon Photomultiplier (SiPM) is a novel semiconducting photodetector which can detect single photons. It consists of many microcells (pixels)...  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