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   81882篇
  免费   423篇
  国内免费   387篇
化学   26937篇
晶体学   841篇
力学   6794篇
数学   32124篇
物理学   15996篇
  2020年   54篇
  2019年   61篇
  2018年   10474篇
  2017年   10284篇
  2016年   6107篇
  2015年   901篇
  2014年   362篇
  2013年   485篇
  2012年   3921篇
  2011年   10669篇
  2010年   5748篇
  2009年   6159篇
  2008年   6783篇
  2007年   8976篇
  2006年   442篇
  2005年   1467篇
  2004年   1681篇
  2003年   2132篇
  2002年   1160篇
  2001年   359篇
  2000年   424篇
  1999年   235篇
  1998年   251篇
  1997年   194篇
  1996年   239篇
  1995年   159篇
  1994年   120篇
  1993年   150篇
  1992年   103篇
  1991年   112篇
  1990年   90篇
  1989年   112篇
  1988年   116篇
  1987年   100篇
  1986年   97篇
  1985年   109篇
  1984年   110篇
  1983年   86篇
  1982年   96篇
  1981年   80篇
  1980年   83篇
  1979年   99篇
  1978年   88篇
  1977年   79篇
  1976年   41篇
  1975年   46篇
  1974年   46篇
  1973年   43篇
  1914年   45篇
  1909年   41篇
排序方式: 共有10000条查询结果,搜索用时 287 毫秒
1.
The three-dimensional structure of nanocomposite microgels was precisely determined by cryo-electron micrography. Several nanocomposite microgels that differ with respect to their nanocomposite structure, which were obtained from seeded emulsion polymerization in the presence of microgels, were used as model nanocomposite materials for cryo-electron micrography. The obtained three-dimensional segmentation images of these nanocomposite microgels provide important insights into the interactions between the hydrophobic monomers and the microgels, that is, hydrophobic styrene monomers recognize molecular-scale differences in polarity within the microgels during the emulsion polymerization. This result led to the formation of unprecedented multi-layered nanocomposite microgels, which promise substantial potential in colloidal applications.  相似文献   
2.
In the paper, the authors establish several integral representations for the generating functions of the large and little Schröder numbers and for the large and little Schröder numbers.  相似文献   
3.
Mesoscopic modeling at the pore scale offers great promise in exploring the underlying structure transport performance of flow through porous media. The present work studies the fluid flow subjected to capillarity-induced resonance in porous media characterized by different porous structure and wettability. The effects of porosity and wettability on the displacement behavior of the fluid flow through porous media are discussed. The results are presented in the form of temporal evolution of percentage saturation and displacement of the fluid front through porous media. The present study reveals that the vibration in the form of acoustic excitation could be significant in the mobilization of fluid through the porous media. The dependence of displacement of the fluid on physicochemical parameters like wettability of the surface, frequency along with the porosity is analyzed. It was observed that the mean displacement of the fluid is more in the case of invading fluid with wetting phase where the driving force strength is not so dominant.  相似文献   
4.
5.
We prove that the group of diffeomorphisms of the interval [0, 1] contains surface groups whose action on (0, 1) has no global fix point and such that only countably many points of the interval (0, 1) have non-trivial stabiliser.  相似文献   
6.
7.
8.
9.
Journal of Radioanalytical and Nuclear Chemistry - Extraction chromatography flow-sheet employing octyl(phenyl)-N,N-diisobutylcarbonoylmethylphosphine oxide and bis(2-ethylhexyl) hydrogen phosphate...  相似文献   
10.
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   
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