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   1430853篇
  免费   43745篇
  国内免费   19205篇
化学   732567篇
晶体学   21217篇
力学   80007篇
综合类   764篇
数学   253335篇
物理学   405913篇
  2021年   16457篇
  2020年   19016篇
  2019年   19394篇
  2018年   15305篇
  2017年   13390篇
  2016年   31686篇
  2015年   24539篇
  2014年   35320篇
  2013年   80838篇
  2012年   46204篇
  2011年   43463篇
  2010年   42689篇
  2009年   44801篇
  2008年   40452篇
  2007年   35404篇
  2006年   41430篇
  2005年   32769篇
  2004年   33296篇
  2003年   30950篇
  2002年   31804篇
  2001年   31363篇
  2000年   27018篇
  1999年   24586篇
  1998年   22680篇
  1997年   22459篇
  1996年   22553篇
  1995年   20433篇
  1994年   19787篇
  1993年   19100篇
  1992年   19201篇
  1991年   19319篇
  1990年   18500篇
  1989年   18341篇
  1988年   17775篇
  1987年   17746篇
  1986年   16655篇
  1985年   23013篇
  1984年   24093篇
  1983年   20238篇
  1982年   21802篇
  1981年   21014篇
  1980年   20318篇
  1979年   20614篇
  1978年   21830篇
  1977年   21472篇
  1976年   21171篇
  1975年   19915篇
  1974年   19577篇
  1973年   20032篇
  1972年   14501篇
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
191.
Crystallography Reports - Some questions related to the establishment, development, and prospects of physical studies using inelastic thermal-neutron scattering are briefly reviewed. The directions...  相似文献   
192.
Theoretical and Mathematical Physics - The fractional derivative method is used to take wave dispersion into account in the wave equation when describing the propagation of gravitational soliton...  相似文献   
193.
Crystallography Reports - The specific features of the formation of crystallites in gallium arsenide crystals grown by the Czochralski method have been investigated. The crystallites are found to...  相似文献   
194.
Journal of Experimental and Theoretical Physics - This article presents a survey of many nontrivial effects connected with the coupling of electric and magnetic degrees of freedom in...  相似文献   
195.
Herein, we successfully construct the 3D biocompatible graphene through crosslinking 2D graphene nanosheet onto carbon fiber paper with poly(diallyldimethylammonium chloride) (PDDA) as anode of the alcohol biofuel cell. Compared with the bioanode without 3D graphene, the current density and output power of PDDA-graphene-ADH bioanode is increased by 23 % and 41 % at a high concentration of ethanol at pH 8.9, suggesting the stabilization role of graphene in enzyme loading. The study provides us a deep analysis on structures and performances of the bioanode incl. electrochemistry, X-ray photoelectron spectra, and atomic force microscopy images, which is significant to develop the new methods to construct 3D porous electrodes in energy conversion device.  相似文献   
196.
A facile biosynthesis route was followed to prepare zinc oxide nanoparticles (ZnO NPs) using Euphorbia milii (E. milii) leaf constituents. The SEM images exhibited presence of spherical ZnO NPs and the corresponding TEM images disclosed monodisperse nature of the ZnO NPs with diameter ranges between 12 and 20 nm. The Brunauer–Emmett–Teller (BET) analysis revealed that the ZnO NPs have specific surface area of 20.46 m2/g with pore diameter of 2 nm–10 nm and pore volume of 0.908 cm3/g. The EDAX spectrum exemplified the existence of Zn and O elements and non-appearance of impurities that confirmed pristine nature of the ZnO NPs. The XRD pattern indicated crystalline peaks corresponding to hexagonal wurtzite structured ZnO with an average crystallite size of 16.11 nm. The FTIR spectrum displayed strong absorption bands at 512 and 534 cm?1 related to ZnO. The photocatalytic action of ZnO NPs exhibited noteworthy degradation of methylene blue dye under natural sunlight illumination. The maximum degradation efficiency achieved was 98.17% at an illumination period of 50 min. The reusability study proved considerable photostability of the ZnO NPs during photocatalytic experiments. These findings suggest that the E. milii leaf constituents can be utilized as suitable biological source to synthesis ZnO NPs for photocatalytic applications.  相似文献   
197.
Crystallography Reports - Methods of coherent X-ray diffraction imaging of the spatial structure of noncrystalline objects and nanocrystals (nanostructures) are considered. Particular attention is...  相似文献   
198.
Aequationes mathematicae - For $$p\in (1,\infty )$$ , we establish several criteria of one-sided invertibility on spaces $$l^p=l^p(\mathbb {Z})$$ for discrete band-dominated operators being either...  相似文献   
199.
200.
Journal of Mathematical Chemistry - The analytical solutions of an asymmetric double well potential $$V(x)=a\, x^2-b\, x^3+c\, x^4$$ are found to be a triconfluent Heun function $$H_{T}(\alpha ,...  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