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   8310篇
  免费   876篇
  国内免费   655篇
化学   5663篇
晶体学   74篇
力学   379篇
综合类   49篇
数学   1128篇
物理学   2548篇
  2024年   19篇
  2023年   142篇
  2022年   233篇
  2021年   262篇
  2020年   275篇
  2019年   252篇
  2018年   248篇
  2017年   221篇
  2016年   342篇
  2015年   337篇
  2014年   444篇
  2013年   535篇
  2012年   662篇
  2011年   678篇
  2010年   444篇
  2009年   450篇
  2008年   508篇
  2007年   450篇
  2006年   415篇
  2005年   363篇
  2004年   266篇
  2003年   240篇
  2002年   233篇
  2001年   216篇
  2000年   161篇
  1999年   133篇
  1998年   112篇
  1997年   90篇
  1996年   108篇
  1995年   108篇
  1994年   97篇
  1993年   90篇
  1992年   86篇
  1991年   98篇
  1990年   70篇
  1989年   53篇
  1988年   53篇
  1987年   38篇
  1986年   28篇
  1985年   39篇
  1984年   29篇
  1983年   23篇
  1982年   22篇
  1981年   24篇
  1980年   16篇
  1979年   16篇
  1978年   16篇
  1975年   15篇
  1974年   13篇
  1973年   12篇
排序方式: 共有9841条查询结果,搜索用时 15 毫秒
31.
32.
33.
Let g is a positive increasing function with 1?g(0). The existence of a unique solution of the Navier-Stokes flow associated with Kε,γ and the convergence of the solution to that of the Euler equations as the viscosity goes to zero are established.  相似文献   
34.
Excitation functions for the55Mn(p, p )55Mn,55Mn(p, n )55Fe and55Mn(p, )56Fe reactions are studied for proton beam energyE p=1·3–2 MeV. The excitation functions are established from yield functions for -rays emitted from the first excited states of final nuclei. Many resonances are observed and competition of their decay into all three output channels is analysed. Spin-parity assignment for some resonant states in the56Fe compound nucleus is deduced.Participated partly in the course of his work on a Thesis.The authors wish to thank the staff of the Van de Graaff accelerator at Charles University in Prague for the efficient operation of the machine and dr. I. Wilhelm for the valuable technical help in the early period of the experimental work. One of us (N. A. N.) acknowledges the staff of the Dept. of Nuclear Physics of Charles University in Prague for the excellent working conditions.  相似文献   
35.
36.
37.
The concentration polarization phenomena in ion exchange membrane electrodialysis have been studied with single exchange membrane cell. The limiting current densities of Asahi ion-permselective membranes CK-1 and CK-2, Selemion ion-exchange membranes CMV, AMV, DMV and ASV have been measured with Ag-AgCl reversible electrode in various electrolyte solutions under 25°C and constant flow rate. In sodium chloride solution, the cation exchange membrane is easier to occur concentration polarization than the anion exchange membrane. The limiting current density increases as the concentration of solution increases for the same kind of ion exchange membrane. The experimental limiting current densities of Selemion CMV and AMV in NaCl, KCl, MgCl2, CaCl2, BaCl2, Na2SO4, NaOH and HCl aqueous solutions are measured. The results show that the limiting current density increases as the ion mobility and diffusivity increase, and is affected by the transference number of ion. For the mixture of electrolyte solution, there are linear relationship between limiting current density and equivalent fraction of electrolytes.  相似文献   
38.
A sensitive microbore liquid chromatographic method combined with the minimally invasive technique of microdialysis was devised for simultaneously and continuously monitoring the levels of unbound blood and brain cefazolin in rats. Microdialysis probes were inserted into the jugular vein and brain striatum for blood and brain sampling, respectively. Chromatographic conditions consisted of a mobile phase of methanol-acetonitrile-100 mM monosodium phosphoric acid (20:10:70, v/v, pH 4.5) pumped through a microbore reversed-phase column at a flow rate of 0.05 mL/min. The ultraviolet detection wavelength was set at 270 nm. An on-line design allowed direct and continuous analysis of protein-free samples in the dialysate. Microdialysis probes, being home-made, were screened for acceptable in vivo recovery. Chromatographic resolution and detection were validated for response linearity as well as intra-day and inter-day variabilities. This method was then applied to pharmacokinetic profiling of protein unbound cefazolin in both the blood and brain following intravenous administration (10 mg/kg, i.v., n = 6). Rapid appearance of cefazolin in the rat brain striatal dialysate following drug injection suggested good blood-brain barrier penetration. According to a non-compartmental pharmacokinetics model, the area under the concentration (AUC) vs time ratio of cefazolin in rat brain and blood was 6%.  相似文献   
39.
本文研究带有五次项的非线性Schrödinger方程初边值问题的有限差分法,其中方程中二阶偏导数项的系数、五次项的系数及初值满足下面的条件(1.6).针对此问题,我们研究了一个守恒差分格式,在条件(1.6)下,差分解的$L^{\infty}$模先验估计被得到.在此基础上,我们得到了差分解最优$L^2$模的误差估计.  相似文献   
40.
Pang  Sabrina X. M.  Lv  Lun  Wang  Jiaxue 《Mathematical Notes》2022,111(1-2):115-123
Mathematical Notes - The Boros–Moll polynomials $$P_m(a)$$ arise in the evaluation of a quartic integral. In the past few years, there has been some remarkable research on the properties of...  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