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   171387篇
  免费   1808篇
  国内免费   507篇
化学   88373篇
晶体学   3023篇
力学   7164篇
综合类   3篇
数学   19570篇
物理学   55569篇
  2020年   1402篇
  2019年   1555篇
  2018年   1985篇
  2017年   2069篇
  2016年   3194篇
  2015年   1893篇
  2014年   3124篇
  2013年   7680篇
  2012年   5775篇
  2011年   6908篇
  2010年   5030篇
  2009年   5009篇
  2008年   6559篇
  2007年   6459篇
  2006年   6109篇
  2005年   5536篇
  2004年   5115篇
  2003年   4615篇
  2002年   4467篇
  2001年   5231篇
  2000年   3869篇
  1999年   2976篇
  1998年   2485篇
  1997年   2388篇
  1996年   2249篇
  1995年   2122篇
  1994年   2100篇
  1993年   2011篇
  1992年   2318篇
  1991年   2257篇
  1990年   2201篇
  1989年   2128篇
  1988年   2128篇
  1987年   2132篇
  1986年   2020篇
  1985年   2640篇
  1984年   2689篇
  1983年   2387篇
  1982年   2493篇
  1981年   2311篇
  1980年   2287篇
  1979年   2433篇
  1978年   2468篇
  1977年   2395篇
  1976年   2441篇
  1975年   2364篇
  1974年   2331篇
  1973年   2505篇
  1972年   1606篇
  1971年   1326篇
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
51.
Galkina  E. G.  Zaspel  C. E.  Ivanov  B. A.  Kulagin  N. E.  Lerman  L. M. 《JETP Letters》2019,110(7):481-486
JETP Letters - The motion of domain walls in GdFeCo-type ferrimagnets near the point of compensation of sublattice spins s1 and s2, when the effects of the exchange increase in the limiting wall...  相似文献   
52.
53.
A uniform dispersion of reactants is necessary to achieve a complete reaction involving multicomponents. In this study, we have examined the role of plasticizer in the reaction of two seemingly unlikely reactants: a highly crystalline hexamethylenetetramine (HMTA) and a strongly hydrogen bonded phenol formaldehyde resin. By combining information from NMR, infrared spectroscopy and differential scanning calorimetry, we were able to determine the role of specific intermolecular interactions necessary for the plasticizer to dissolve the highly crystalline HMTA and to plasticize the phenol formaldehyde resin in this crosslinking reaction. The presence of the plasticizer increased the segmental mobility, disrupted the hydrogen bonded matrix, and freed the hydroxyl units, which further increased the solubility of the HMTA. Both the endothermic and exothermic transitions are accounted for in the calorimetric data obtained. For the first time, it is possible to obtain the effective molar ratio of each component needed to complete the crosslinking reaction efficiently. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 1519–1526  相似文献   
54.
The structure and properties of 12Cr1MoV steel irradiated with a zirconium ion beam were studied by optical microscopy, scanning electron microscopy, and micro- and nanoindentation. It is shown that the modification covers the entire cross-section of the irradiated specimens to a depth of 1 mm. The data on irradiation-induced structural changes are used to interpret the changes in mechanical properties of the irradiated specimens under static and cyclic loading. Particular attention is given to analysis of strain estimation by the digital image correlation method.  相似文献   
55.
56.
57.
58.
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   
59.
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   
60.
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