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   481664篇
  免费   4106篇
  国内免费   1756篇
化学   236688篇
晶体学   7251篇
力学   24328篇
综合类   7篇
数学   77217篇
物理学   142035篇
  2020年   3418篇
  2019年   3913篇
  2018年   15184篇
  2017年   14903篇
  2016年   13114篇
  2015年   5164篇
  2014年   7383篇
  2013年   18064篇
  2012年   16657篇
  2011年   26024篇
  2010年   16873篇
  2009年   17163篇
  2008年   21368篇
  2007年   23503篇
  2006年   14545篇
  2005年   14208篇
  2004年   13241篇
  2003年   12474篇
  2002年   11467篇
  2001年   11852篇
  2000年   9301篇
  1999年   7094篇
  1998年   6136篇
  1997年   6057篇
  1996年   5773篇
  1995年   4990篇
  1994年   5003篇
  1993年   5063篇
  1992年   5317篇
  1991年   5525篇
  1990年   5203篇
  1989年   5190篇
  1988年   5137篇
  1987年   5004篇
  1986年   4746篇
  1985年   6373篇
  1984年   6657篇
  1983年   5366篇
  1982年   5796篇
  1981年   5626篇
  1980年   5338篇
  1979年   5616篇
  1978年   5795篇
  1977年   5742篇
  1976年   5794篇
  1975年   5346篇
  1974年   5393篇
  1973年   5509篇
  1972年   3836篇
  1971年   3284篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
62.
Ni–Co alloys have a wide range of applications in various fields owning to their excellent physical, chemical, and mechanical properties. In this paper, we prepare Ni–Co alloy coatings on 316L stain steel surfaces by electroplating. We present a novel approach utilizing a nanosecond laser to induce microtextures on Ni–Co alloy coatings. We study experimentally the effects of laser power and scanning rate on the surface morphologies of Ni–Co alloy coatings. The results indicate that the shape and size of induced microtextures can be controlled by the laser power and scanning rate. The size of grains increases with increase in the work current of the laser (WCL) at a certain scanning rate. With the WCL constant, the size of grains decreases with increase in scanning rate while their average height increases. It is a simple and easily-controlled method for the fabrication of microstructures on Ni–Co alloy coatings, which has promising applications in investigations of the properties of microtextured surfaces, such as friction, adhesion, and wetting.  相似文献   
63.
64.
65.
66.
67.
Influence of the nuclear energy structure, the conditions of fuel burnup, and accumulation of new fissile isotopes from the raw isotopes on the main parameters of a closed fuel cycle is considered. The effects of the breeding ratio, the cooling time of the spent fuel in the external fuel cycle, and the separation of the breeding area and the fissile isotope burning area on the parameters of the fuel cycle are analyzed.  相似文献   
68.
69.
Kinetics and Catalysis - Boron and barium were employed as dopants for the VMgO system. The catalysts were characterized by ICP-OES, BET, IR, powder XRD, EDX, TPR-H2, TPD-NH3, XPS, and 51V MAS NMR....  相似文献   
70.
Homogenous amphiphilic crosslinked polymer films comprising of poly(ethylene oxide) and polysiloxane were synthesized utilizing thiol‐ene “ click ” photochemistry. A systematic variation in polymer composition was Carried out to obtain high quality films with varied amount of siloxane and poly(ethylene oxide). These films showed improved gas separation performance with high gas permeabilities with good CO2/N2 selectivity. Furthermore, the resulting films were also tested for its biocompatibility, as a carrier media which allow human adult mesenchymal stem cells to retain their capacity for osteoblastic differentiation after transplantation. The obtained crosslinked films were characterized using differential scanning calorimetry, dynamic mechanical analysis, thermogravimetric analysis, FTIR, Raman‐IR , and small angle X‐ray scattering. The synthesis ease and commercial availability of the starting materials suggests that these new crosslinked polymer networks could find applications in wide range of applications. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1548–1557  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