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   84014篇
  免费   475篇
  国内免费   401篇
化学   27976篇
晶体学   861篇
力学   6955篇
数学   32563篇
物理学   16535篇
  2020年   55篇
  2019年   61篇
  2018年   10465篇
  2017年   10285篇
  2016年   6147篇
  2015年   952篇
  2014年   364篇
  2013年   614篇
  2012年   4018篇
  2011年   10762篇
  2010年   5786篇
  2009年   6176篇
  2008年   6822篇
  2007年   8991篇
  2006年   507篇
  2005年   1546篇
  2004年   1745篇
  2003年   2174篇
  2002年   1218篇
  2001年   375篇
  2000年   415篇
  1999年   239篇
  1998年   283篇
  1997年   278篇
  1996年   327篇
  1995年   214篇
  1994年   190篇
  1993年   231篇
  1992年   183篇
  1991年   136篇
  1990年   117篇
  1989年   158篇
  1988年   147篇
  1987年   140篇
  1986年   135篇
  1985年   142篇
  1984年   149篇
  1983年   117篇
  1982年   123篇
  1981年   121篇
  1980年   117篇
  1979年   117篇
  1978年   105篇
  1977年   88篇
  1976年   73篇
  1975年   95篇
  1974年   83篇
  1973年   84篇
  1972年   48篇
  1914年   48篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
1.
Low-flow chromatography has a rich history of innovation but has yet to reach widespread implementation in bioanalytical applications. Improvements in pump technology, microfluidic connections, and nano-electrospray sources for MS have laid the groundwork for broader application, and innovation in this space has accelerated in recent years. This article reviews the instrumentation used for nano-flow LC, the types of columns employed, and strategies for multidimensionality of separations, which are key to the future state of the technique to the high-throughput needs of modern bioanalysis. An update of the current applications where nano-LC is widely used, such as proteomics and metabolomics, is discussed. But the trend toward biopharmaceutical development of increasingly complex, targeted, and potent therapeutics for the safe treatment of disease drives the need for ultimate selectivity and sensitivity of our analytical platforms for targeted quantitation in a regulated space. The selectivity needs are best addressed by mass spectrometric detection, especially at high resolutions, and exquisite sensitivity is provided by nano-electrospray ionization as the technology continues to evolve into an accessible, robust, and easy-to-use platform.  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.
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