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   340661篇
  免费   12612篇
  国内免费   3464篇
化学   207051篇
晶体学   3623篇
力学   13113篇
综合类   18篇
数学   39126篇
物理学   93806篇
  2021年   2480篇
  2020年   3980篇
  2019年   5516篇
  2018年   5006篇
  2017年   4619篇
  2016年   9216篇
  2015年   7087篇
  2014年   8761篇
  2013年   17539篇
  2012年   14006篇
  2011年   15384篇
  2010年   11683篇
  2009年   11479篇
  2008年   14327篇
  2007年   13857篇
  2006年   12647篇
  2005年   11870篇
  2004年   11116篇
  2003年   9691篇
  2002年   9982篇
  2001年   8642篇
  2000年   6597篇
  1999年   4722篇
  1998年   4138篇
  1997年   4055篇
  1996年   3885篇
  1995年   3650篇
  1994年   3813篇
  1993年   3520篇
  1992年   3954篇
  1991年   3874篇
  1990年   3804篇
  1989年   3633篇
  1988年   3689篇
  1987年   3630篇
  1986年   3424篇
  1985年   4621篇
  1984年   4879篇
  1983年   4037篇
  1982年   4151篇
  1981年   4093篇
  1980年   4033篇
  1979年   3999篇
  1978年   4302篇
  1977年   4223篇
  1976年   4263篇
  1975年   3939篇
  1974年   3969篇
  1973年   4138篇
  1972年   2890篇
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
1.
Doklady Mathematics - New properties of convex infinitely differentiable functions related to extremal problems are established. It is shown that, in a neighborhood of the solution, even if the...  相似文献   
2.
In this article, a way to employ the diffusion approximation to model interplay between TCP and UDP flows is presented. In order to control traffic congestion, an environment of IP routers applying AQM (Active Queue Management) algorithms has been introduced. Furthermore, the impact of the fractional controller PIγ and its parameters on the transport protocols is investigated. The controller has been elaborated in accordance with the control theory. The TCP and UDP flows are transmitted simultaneously and are mutually independent. Only the TCP is controlled by the AQM algorithm. Our diffusion model allows a single TCP or UDP flow to start or end at any time, which distinguishes it from those previously described in the literature.  相似文献   
3.
JETP Letters - The effect of static mechanical strain on the splitting of spin sublevels of color centers based on spin 3/2 silicon vacancies in silicon carbide at room temperature has been shown....  相似文献   
4.
During metal welding and cutting, large amounts of particulate matter (PM) are produced that might represent a significant health risk for the exposed workers. In the present pilot study, we performed an elemental analysis of fine PM collected in a metal workshop. Also, elemental analysis of the hair and nail samples collected from workers exposed to the workshop dust and control group was done. Concentrations of 15 elements in PM were measured with X‐Ray Fluorescence (XRF) and Particle Induced X‐ray Emission (PIXE), whereas inductively coupled plasma mass spectrometry (ICP‐MS) was used to determine 12 elements in hair and nail samples. Mean 8‐hr concentrations of PM2.5, Fe, and Mn in the vicinity of welders were up to 1803, 860, and 30 μg/m3, respectively, whereas in the nearby city, daily PM2.5 concentrations are on average 11 μg/m3. We found that several elements, especially Fe and Mn, had substantially higher concentrations in hair and nail samples of exposed workers than in the control group, which indicates the accumulation of metals in workers' tissues, although limit values were not exceeded.  相似文献   
5.
Crystallography Reports - The orientation of grains and the special boundaries formed by them in multicrystalline silicon has been studied by electron backscattered diffraction. It is found that...  相似文献   
6.
Applications of Mathematics - Proper traffic simulation of electric vehicles, which draw energy from overhead wires, requires adequate modeling of traction infrastructure. Such vehicles include...  相似文献   
7.
Doklady Physics - The dependence of Raman spectra of the molecules containing polyene chains on the conjugation length, structure of side and end groups, and isomer type is analyzed theoretically.  相似文献   
8.
JETP Letters - Photonically controlled metastructures containing resonant conducting dipole and chiral elements with CdS and CdSe in gaps have been proposed, implemented, and studied in a waveguide...  相似文献   
9.
Set-Valued and Variational Analysis - In a Hilbert framework ℌ, we study the convergence properties of a Newton-like inertial dynamical system governed by a general maximally monotone...  相似文献   
10.
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