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   87541篇
  免费   1697篇
  国内免费   1052篇
化学   30640篇
晶体学   876篇
力学   7201篇
综合类   41篇
数学   33200篇
物理学   18332篇
  2023年   181篇
  2022年   350篇
  2021年   369篇
  2020年   433篇
  2019年   355篇
  2018年   10664篇
  2017年   10459篇
  2016年   6497篇
  2015年   1329篇
  2014年   830篇
  2013年   1062篇
  2012年   4628篇
  2011年   11258篇
  2010年   6173篇
  2009年   6562篇
  2008年   7185篇
  2007年   9190篇
  2006年   715篇
  2005年   1659篇
  2004年   1834篇
  2003年   2218篇
  2002年   1220篇
  2001年   401篇
  2000年   452篇
  1999年   337篇
  1998年   354篇
  1997年   285篇
  1996年   342篇
  1995年   233篇
  1994年   180篇
  1993年   174篇
  1992年   141篇
  1991年   144篇
  1990年   100篇
  1989年   110篇
  1988年   100篇
  1987年   96篇
  1986年   93篇
  1985年   83篇
  1984年   68篇
  1983年   61篇
  1982年   60篇
  1981年   66篇
  1980年   62篇
  1979年   62篇
  1978年   41篇
  1914年   45篇
  1912年   40篇
  1909年   43篇
  1908年   40篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Properties and some applications of strongly orthogonal geminals (APSG) are reviewed emphasizing the motivations for their use and their shortcomings. An overview presents some techniques capable of improving the APSG function.  相似文献   
102.
Solubility of methane in octane + ethanol was measured at temperatures ranging from 303.15 K to 333.15 K and pressures ranging from 2.60 MPa to 12.01 MPa. Experimental data were analyzed using the Soave-Redlich-Kwong equation of state with three types of mixing rules, and the estimated average deviation from the experimental solubility data was less than 3.5 %.  相似文献   
103.
The paper presents a short review on the synthesis, characterisation and selected medical applications of poly(styrene/α-tert-butoxy-ω-vinylbenzyl-polyglycidol) (P(S/PGL)) microspheres. The soap-free emulsion-polymerisation of styrene and α-tert-butoxy-ω-vinylbenzyl-polyglycidol macromonomer (PGL) in water yielded core-shell microspheres with a low particle-diameter dispersity (ratio of the weight average particle diameter and the number average particle diameter). The interfacial fraction of PGL units, estimated by XPS, was in the range of 0–42 mole % depending on the concentration of the macromonomer in the polymerisation feed. The studies of adsorption of model proteins showed that the surface fraction of adsorbed protein was significantly reduced when the PGL interfacial fraction was higher than 40 mole %. The P(S/PGL) particles with covalently immobilised proteins were used for the preparation of photonic crystal assemblies suitable for applications in optical biosensors and the medical diagnostic test for the detection of Helicobacter pylori antibodies in the blood serum.  相似文献   
104.
The synthesis of a new halogenide containing hexyltriethylene glycol chain functionalized with biotin is reported. The general possibility of this linker to use as the building block for biotinylated compounds syntheses is demonstrated. Two biotinylated esters with different properties for useful surface modification and as fluorescence probes for proteins marking were synthesized. The properties of mentioned compounds were investigated by using surface plazmon resonance ellypsometry and fluorescence spectroscopy.  相似文献   
105.
A method for characterizing and identifying firing patterns of neural spike trains is presented. Three characteristic variables defined at sequential moments, including two formal derivatives and the integration of the counting process, are introduced to reflect the temporal patterns of a spike train. This paper also examines how noise interacts with encoding mechanisms of neuronal stimulus in a cold receptor. From ISI series and bifurcation diagrams it is shown that there are considerable differences in interval distributions and impulse patterns caused by purely deterministic simulations and noisy simulations. The ISI-distance can be used as an effective and powerful way to measure the noise effects on spike trains quantitatively. It is found that spike trains observed in cold receptors can be more strongly affected by noise for low temperatures than for high temperatures in some aspects; meanwhile, spike train has greater variability with the noise intensity increasing.  相似文献   
106.
107.
This work studies the Soret and Dufour effects on the double-diffusive free convection over a downward-pointing vertical truncated cone with variable wall heat and mass fluxes in fluid-saturated porous media. A coordinate transformation is used to derive the nondimensional boundary-layer governing equations, and the obtained nonsimilar equations are then solved by the cubic spline collocation method. Results for local surface temperature and the local surface concentration are presented as functions of Soret parameters, Dufour parameters, power-law exponents, buoyancy ratios, and Lewis numbers. Results show that increasing the Dufour parameter tends to increase the local surface temperature, while it tends to decrease the local surface concentration. An increase in the Soret number leads to a decrease in the local surface temperature for buoyancy assisting flows, while it leads to an increase in the local surface temperature for buoyancy opposing flows. Increasing the Soret number tends to increase the local surface concentration. Moreover, the local surface temperature and the local surface concentration of the truncated cones with higher power-law exponents are lower than those with lower exponents.  相似文献   
108.
The effects of temperature-dependent viscosity, gravity modulation and thermo-mechanical anisotropies on heat transport in a low-porosity medium are studied using the Ginzburg–Landau model. The effect of gravity modulation is to decrease the Nusselt number, Nu and variable viscosity leads to increase in Nu. The thermo-mechanical anisotropies have opposite effect on Nu with thermal anisotropy decreasing the heat transport.  相似文献   
109.
The solution of cylindrical problems is addressed. A series solution is considered of the biharmonic equation, in which the series terms of the stress function Φ are expressions based upon Legendre polynomials and logarithmically singular functions. An explicit form of a polynomial supplementing each logarithmically singular part of the series solution is obtained.  相似文献   
110.
We consider the flow of a viscous incompressible fluid in a pipe when the boundary is a deformable shell of Naghdi type. We prove that the corresponding system of partial differential equations has a solution when the deformation of the shell is smooth and small enough. We propose an algorithm that uncouples the unknowns and prove its convergence.  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