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   89616篇
  免费   1421篇
  国内免费   1109篇
化学   32095篇
晶体学   898篇
力学   7214篇
综合类   52篇
数学   33268篇
物理学   18619篇
  2023年   156篇
  2022年   161篇
  2021年   261篇
  2020年   318篇
  2019年   335篇
  2018年   10637篇
  2017年   10463篇
  2016年   6418篇
  2015年   1252篇
  2014年   774篇
  2013年   1011篇
  2012年   4633篇
  2011年   11434篇
  2010年   6234篇
  2009年   6673篇
  2008年   7305篇
  2007年   9422篇
  2006年   853篇
  2005年   1843篇
  2004年   2035篇
  2003年   2405篇
  2002年   1400篇
  2001年   571篇
  2000年   559篇
  1999年   356篇
  1998年   354篇
  1997年   278篇
  1996年   341篇
  1995年   247篇
  1994年   223篇
  1993年   221篇
  1992年   169篇
  1991年   161篇
  1990年   159篇
  1989年   141篇
  1988年   147篇
  1987年   120篇
  1986年   126篇
  1985年   142篇
  1984年   113篇
  1983年   104篇
  1982年   90篇
  1981年   83篇
  1980年   93篇
  1979年   78篇
  1978年   66篇
  1977年   55篇
  1976年   53篇
  1974年   59篇
  1973年   69篇
排序方式: 共有10000条查询结果,搜索用时 686 毫秒
1.
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   
2.
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   
3.
4.
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   
5.
6.
7.
Journal of Thermal Analysis and Calorimetry - Coal O2/CO2 combustion is a promising carbon capture and storage technology for coal-fired power plant. Char consumption rate prediction is essential...  相似文献   
8.
9.
10.
The Insight-Hard X-ray Modulation Telescope(Insight-HXMT) is a broadband X-ray and γ-ray(1-3000 ke V) astronomy satellite. One of its three main telescopes is the High Energy X-ray telescope(HE). The main detector plane of HE comprises 18 Na I(Tl)/Cs I(Na) phoswich detectors, where Na I(Tl) is used as the primary detector to measure ~ 20-250 ke V photons incident from the field of view(FOV) defined by collimators, and Cs I(Na) is used as the active shielding detector to Na I(Tl) by pulse shape discrimination. Additionally, Cs I(Na) is used as an omnidirectional γ-ray monitor. The HE collimators have a diverse FOV,i.e. 1.1°×5.7°(15 units), 5.7°×5.7°(2 units), and blocked(1 unit). Therefore, the combined FOV of HE is approximately5.7°×5.7°. Each HE detector has a diameter of 190 mm resulting in a total geometrical area of approximately 5100 cm2, and the energy resolution is ~15% at 60 ke V. For each recorded X-ray event by HE, the timing accuracy is less than 10 μs and the deadtime is less than 10 μs. HE is used for observing spectra and temporal variability of X-ray sources in the 20-250 ke V band either by pointing observations for known sources or scanning observations to unveil new sources. Additionally, HE is used for monitoring the γ-ray burst in 0.2-3 Me V band. This paper not only presents the design and performance of HE instruments but also reports results of the on-ground calibration experiments.  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