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   408742篇
  免费   4324篇
  国内免费   1098篇
化学   202643篇
晶体学   5089篇
力学   19402篇
综合类   7篇
数学   59493篇
物理学   127530篇
  2020年   1991篇
  2019年   1965篇
  2018年   10979篇
  2017年   11861篇
  2016年   7920篇
  2015年   4163篇
  2014年   4558篇
  2013年   14122篇
  2012年   15040篇
  2011年   25645篇
  2010年   15539篇
  2009年   15455篇
  2008年   22737篇
  2007年   26304篇
  2006年   12400篇
  2005年   18277篇
  2004年   13585篇
  2003年   12182篇
  2002年   10052篇
  2001年   10265篇
  2000年   7983篇
  1999年   6160篇
  1998年   4939篇
  1997年   4761篇
  1996年   4438篇
  1995年   4325篇
  1994年   4074篇
  1993年   3895篇
  1992年   4370篇
  1991年   4250篇
  1990年   3944篇
  1989年   3787篇
  1988年   4102篇
  1987年   3754篇
  1986年   3656篇
  1985年   5330篇
  1984年   5419篇
  1983年   4372篇
  1982年   4745篇
  1981年   4802篇
  1980年   4544篇
  1979年   4698篇
  1978年   4712篇
  1977年   4614篇
  1976年   4614篇
  1975年   4498篇
  1974年   4360篇
  1973年   4565篇
  1972年   2561篇
  1971年   1856篇
排序方式: 共有10000条查询结果,搜索用时 572 毫秒
21.
22.
23.
We study the full counting statistics of transport electrons through a semiconductor two-level quantum dot with Rashba spin–orbit (SO) coupling, which acts as a nonabelian gauge field and thus induces the electron transition between two levels along with the spin flip. By means of the quantum master equation approach, shot noise and skewness are obtained at finite temperature with two-body Coulomb interaction. We particularly demonstrate the crucial effect of SO coupling on the super-Poissonian fluctuation of transport electrons, in terms of which the SO coupling can be probed by the zero-frequency cumulants. While the charge currents are not sensitive to the SO coupling.  相似文献   
24.
25.
26.
27.
We summarize the results of our recent work on Bäcklund transformations (BTs), particularly focusing on the relation between BTs and infinitesimal symmetries. We present a BT for an associated Degasperis–Procesi (aDP) equation and its superposition principle and investigate the solutions generated by applying this BT. Following our general methodology, we use the superposition principle of the BT to generate the infinitesimal symmetries of the aDP equation.  相似文献   
28.
Nanocomposites based on poly-N-vinylcaprolactam (PVC), characterized by different drying temperatures of aqueous PVC solution at 25°С (PVC25) and 40°С (PVC40), with titanium(IV) oxide nanoparticles (TONs) (η-phase (TP: TiO2 – x · mH2O) with a superstructure to the anatase structure and ordered solid solution with partial replacement of oxygen atoms in the η-phase with peroxo group O 2 2– (PP: TiO x (O2)2 – x · nH2O)) have been obtained for the first time and characterized by X-ray diffraction and IR spectroscopy. It is found that a common feature of TP/PVC and PP/PVC obtained by dry mixing and grinding is the decrease in the number of water molecules for TP and PP in the interlayer space of the structure and their attachment to the PVC amide groups; the differences are related to the specificity of PVC behavior in these systems: mechanodestruction of PVC in PP/PVC40 and different numbers of water molecules in PVC25 and PVC40.  相似文献   
29.
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   
30.
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