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   337639篇
  免费   3627篇
  国内免费   1233篇
化学   176087篇
晶体学   5699篇
力学   15119篇
综合类   6篇
数学   36761篇
物理学   108827篇
  2019年   2594篇
  2018年   3258篇
  2017年   3149篇
  2016年   5010篇
  2015年   3265篇
  2014年   5118篇
  2013年   14244篇
  2012年   10420篇
  2011年   13081篇
  2010年   8991篇
  2009年   8771篇
  2008年   11973篇
  2007年   12023篇
  2006年   11574篇
  2005年   10684篇
  2004年   9709篇
  2003年   8684篇
  2002年   8540篇
  2001年   9830篇
  2000年   7537篇
  1999年   6040篇
  1998年   5140篇
  1997年   5025篇
  1996年   4797篇
  1995年   4527篇
  1994年   4251篇
  1993年   4323篇
  1992年   4612篇
  1991年   4715篇
  1990年   4457篇
  1989年   4450篇
  1988年   4463篇
  1987年   4365篇
  1986年   4111篇
  1985年   5582篇
  1984年   5913篇
  1983年   4813篇
  1982年   5261篇
  1981年   5028篇
  1980年   4994篇
  1979年   5098篇
  1978年   5280篇
  1977年   5133篇
  1976年   5243篇
  1975年   4898篇
  1974年   4770篇
  1973年   5027篇
  1972年   3357篇
  1971年   2701篇
  1968年   2522篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Computational Optimization and Applications - We consider a continuous-time optimization method based on a dynamical system, where a massive particle starting at rest moves in the conservative...  相似文献   
22.
Herein, we report a Mott-Schottky catalyst by entrapping cobalt nanoparticles inside the N-doped graphene shell (Co@NC). The Co@NC delivered excellent oxygen evolution activity with an overpotential of merely 248 mV at a current density of 10 mA cm–2 with promising long-term stability. The importance of Co encapsulated in NC has further been demonstrated by synthesizing Co nanoparticles without NC shell. The synergy between the hexagonal close-packed (hcp) and face-centered cubic (fcc) Co plays a major role to improve the OER activity, whereas the NC shell optimizes the electronic structure, improves the electron conductivity, and offers a large number of active sites in Co@NC. The density functional theory calculations have revealed that the hcp Co has a dominant role in the surface reaction of electrocatalytic oxygen evolution, whereas the fcc phase induces the built-in electric field at the interfaces with N-doped graphene to accelerate the H+ ion transport.  相似文献   
23.
Crystallography Reports - Two LiInSe2 single crystals, grown under different conditions, have been studied. Characteristics of these crystals for neutron detection have been compared using...  相似文献   
24.
25.
26.
Chen  R. J.  Chen  W.  Kong  F. L. 《Analysis Mathematica》2022,48(1):19-28

Restricted testing conditions were considered recently. For the maximal operator, Hytönen, Li and Sawyer [8] first obtained parental testing condition. Later, they [9] showed that it suffices to restrict testing to doubling cubes. Chen and Lacey [3] gave a similar restricted testing condition. In our paper, we discuss a version of the latter in the multilinear setting.

  相似文献   
27.
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   
28.
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   
29.
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   
30.
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   
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