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   28067篇
  免费   3721篇
  国内免费   3143篇
化学   20384篇
晶体学   366篇
力学   1392篇
综合类   241篇
数学   3525篇
物理学   9023篇
  2023年   440篇
  2022年   486篇
  2021年   697篇
  2020年   915篇
  2019年   932篇
  2018年   797篇
  2017年   763篇
  2016年   1126篇
  2015年   1147篇
  2014年   1361篇
  2013年   1914篇
  2012年   2279篇
  2011年   2517篇
  2010年   1764篇
  2009年   1738篇
  2008年   1938篇
  2007年   1763篇
  2006年   1580篇
  2005年   1393篇
  2004年   1107篇
  2003年   883篇
  2002年   809篇
  2001年   701篇
  2000年   568篇
  1999年   529篇
  1998年   478篇
  1997年   419篇
  1996年   452篇
  1995年   384篇
  1994年   367篇
  1993年   341篇
  1992年   319篇
  1991年   276篇
  1990年   232篇
  1989年   191篇
  1988年   167篇
  1987年   128篇
  1986年   141篇
  1985年   154篇
  1984年   101篇
  1983年   64篇
  1982年   71篇
  1981年   53篇
  1980年   52篇
  1979年   58篇
  1978年   40篇
  1976年   37篇
  1975年   32篇
  1974年   40篇
  1973年   45篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
72.
Over the past few decades, the realm of inorganic medicinal chemistry has been dominated by the study of the anti-cancer properties of transition metal complexes, particularly those based on platinum or ruthenium. However, comparatively less attention has been focused on the development of metal complexes for the treatment of inflammatory or autoimmune diseases. Metal complexes possess a number of advantages that render them as attractive alternatives to organic small molecules for the development of therapeutic agents. In this perspective, we highlight recent examples in the development of transition metal complexes as modulators of inflammatory and autoimmune responses. The studies presented here serve to highlight the potential of transition metal complexes in modulating inflammatory or immune pathways in cells.  相似文献   
73.
74.
A new amino‐functionalized strontium–carboxylate‐based metal–organic framework (MOF) has been synthesized that undergoes single crystal to single crystal (SC‐to‐SC) transformation upon desolvation. Both structures have been characterized by single‐crystal X‐ray analysis. The desolvated structure shows an interesting 3D porous structure with pendent ?NH2 groups inside the pore wall, whereas the solvated compound possesses a nonporous structure with DMF molecules on the metal centers. The amino group was postmodified through Schiff base condensation by pyridine‐2‐carboxaldehyde and palladium was anchored on that site. The modified framework has been utilized for the Suzuki cross‐coupling reaction. The compound shows high activity towards the C?C cross‐coupling reaction with good yields and turnover frequencies. Gas adsorption studies showed that the desolvated compound had permanent porosity and was microporous in nature with a BET surface area of 2052 m2 g?1. The material also possesses good CO2 (8 wt %) and H2 (1.87 wt %) adsorption capabilities.  相似文献   
75.
76.
77.
In conventional research on beam gas coulomb scattering(BGCS), only the related beam lifetime using the analytical method is studied. In this paper, using the particle-in-cell Monte Carlo collisions(PIC-MCC) method,we not only simulated the beam lifetime but also explored the effect of BGCS on the beam distribution. In order to better estimate the effect on particle distribution, we study the ultra-low emittance electron beam. Here we choose the He Fei Advanced Light Source. By counting the lost particles in a certain time, the corresponding beam lifetime we simulated is 4.8482 h/13.8492 h in x/y, which is very close to the theoretic value(5.0555 h /13.7024 h in x/y).By counting the lost particles relative to the collided particles, the simulated value of the loss probability of collided particles is 1.3431e-04, which is also very close to the theoretical value(1.3824e-04). Besides, the simulation shows there is a tail in the transverse distribution due to the BGCS. The close match of the simulation with the theoretic value in beam lifetime and loss probability indicates our simulation is reliable.  相似文献   
78.
79.
80.
Herein, the modified Lagrangian vortex method (LVM), a hybrid analytical‐numerical algorithm per se, is devised to simulate the process of vortex formation and shedding from the sharp edge of a zero‐thickness vertical plate under linear water‐wave attack. Application of the Helmholtz decomposition facilitates a convenient switch between the inviscid‐ and viscous‐flow models, thereby enabling easy incorporation of vorticity effects into the potential‐flow calculations for the viscous‐dominated region. In evaluating the potential‐flow component, making good use of the quickly convergent technique with singular basis functions, correctly capturing the singular behavior in velocity fields near the tip of the plate, leads to a considerable reduction of computational burdens and to 12‐decimal‐place accuracy. The viscous correction is carried out via the meshless LVM with improved boundary conditions. Comparisons with previously published results show good agreement. Simulations of vortex generation and evolution illuminate the ability of the present method, and provide a supplement to pertinent experimental works. The hybrid scheme proposed herein allows flexibility for the former LVM and convenience in the code development. Such a compromise fits particularly well for the high‐resolution modeling of sharp‐edged vortex shedding without heavy numerical developments. Copyright © 2014 John Wiley & Sons, Ltd.  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