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   276468篇
  免费   4020篇
  国内免费   858篇
化学   145293篇
晶体学   4205篇
力学   12225篇
综合类   1篇
数学   32953篇
物理学   86669篇
  2021年   2093篇
  2020年   2438篇
  2019年   2686篇
  2018年   3659篇
  2017年   3418篇
  2016年   5306篇
  2015年   3662篇
  2014年   5227篇
  2013年   12720篇
  2012年   10641篇
  2011年   12599篇
  2010年   8596篇
  2009年   8194篇
  2008年   11411篇
  2007年   11418篇
  2006年   10641篇
  2005年   9802篇
  2004年   8891篇
  2003年   7679篇
  2002年   7432篇
  2001年   7724篇
  2000年   5915篇
  1999年   4659篇
  1998年   3904篇
  1997年   3760篇
  1996年   3734篇
  1995年   3268篇
  1994年   3254篇
  1993年   3350篇
  1992年   3482篇
  1991年   3614篇
  1990年   3334篇
  1989年   3288篇
  1988年   3279篇
  1987年   3167篇
  1986年   2976篇
  1985年   4116篇
  1984年   4291篇
  1983年   3383篇
  1982年   3689篇
  1981年   3594篇
  1980年   3449篇
  1979年   3558篇
  1978年   3652篇
  1977年   3532篇
  1976年   3682篇
  1975年   3321篇
  1974年   3356篇
  1973年   3387篇
  1972年   2328篇
排序方式: 共有10000条查询结果,搜索用时 765 毫秒
21.
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   
22.
23.
24.
A temperature control unit was implemented to vary the temperature of samples studied on a commercial Mobile Universal Surface Explorer nuclear magnetic resonance (MOUSE-NMR) apparatus. The device was miniaturized to fit the maximum MOUSE sampling depth (25 mm). It was constituted by a sample holder sandwiched between two heat exchangers placed below and above the sample. Air was chosen as the fluid to control the temperature at the bottom of the sample, at the interface between the NMR probe and the sample holder, in order to gain space. The upper surface of the sample was regulated by the circulation of water inside a second heat exchanger placed above the sample holder. The feasibility of using such a device was demonstrated first on pure water and then on several samples of bread dough with different water contents. For this, T1 relaxation times were measured at various temperatures and depths and were then compared with those acquired with a conventional compact closed-magnet spectrometer. Discussion of results was based on biochemical transformations in bread dough (starch gelatinization and gluten heat denaturation). It was demonstrated that, within a certain water level range, and because of the low magnetic field strength of the MOUSE, a linear relationship could be established between T1 relaxation times and the local temperature in the dough sample.  相似文献   
25.
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   
26.
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   
27.
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   
28.
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   
29.
30.
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