全文获取类型
收费全文 | 40526篇 |
免费 | 5473篇 |
国内免费 | 4268篇 |
专业分类
化学 | 14556篇 |
晶体学 | 626篇 |
力学 | 2722篇 |
综合类 | 288篇 |
数学 | 1607篇 |
物理学 | 12192篇 |
综合类 | 18276篇 |
出版年
2024年 | 130篇 |
2023年 | 428篇 |
2022年 | 977篇 |
2021年 | 993篇 |
2020年 | 1124篇 |
2019年 | 978篇 |
2018年 | 1045篇 |
2017年 | 1342篇 |
2016年 | 1565篇 |
2015年 | 1568篇 |
2014年 | 2122篇 |
2013年 | 2953篇 |
2012年 | 2636篇 |
2011年 | 2514篇 |
2010年 | 2031篇 |
2009年 | 2199篇 |
2008年 | 2191篇 |
2007年 | 2670篇 |
2006年 | 2367篇 |
2005年 | 2123篇 |
2004年 | 1925篇 |
2003年 | 1736篇 |
2002年 | 1524篇 |
2001年 | 1376篇 |
2000年 | 1342篇 |
1999年 | 1122篇 |
1998年 | 981篇 |
1997年 | 899篇 |
1996年 | 827篇 |
1995年 | 704篇 |
1994年 | 661篇 |
1993年 | 564篇 |
1992年 | 516篇 |
1991年 | 430篇 |
1990年 | 345篇 |
1989年 | 328篇 |
1988年 | 338篇 |
1987年 | 188篇 |
1986年 | 132篇 |
1985年 | 72篇 |
1984年 | 50篇 |
1983年 | 19篇 |
1982年 | 53篇 |
1981年 | 31篇 |
1980年 | 28篇 |
1979年 | 34篇 |
1978年 | 23篇 |
1977年 | 13篇 |
1976年 | 10篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
21.
从点电荷的电势计算公式出发推导出了瓣形均匀带电面在其直径处的电势分布.进一步讨论了均匀带电半球面在其底面以及均匀带电球面内部和外部的电势分布. 相似文献
22.
23.
Huafei Sun 《Geometriae Dedicata》2002,90(1):63-75
We study minimal submanifolds in the locally symmetric and conformally flat Riemannian manifold and generalize Yau's result obtained in J. Amer. Math. 97 (1975), 76–100. 相似文献
24.
果胶的提取率和质量与水解的环境关系密切 .本文重点在蚕沙中提取果胶从产率和颜色方面对水解的环境进行一些定性和定量的研究 ,获知各水解介质采用 0 3 %的稀硫酸液、温度 70— 80℃ ,时间 1h、pH1 5 ,提取的果胶从质量和产率上较理想 相似文献
25.
The paper proposes a rational method to derive fairness measures for surfaces. It works in cases where isophotes, reflection lines, planar intersection curves, or other curves are used to judge the fairness of the surface. The surface fairness measure is derived by demanding that all the given curves should be fair with respect to an appropriate curve fairness measure. The method is applied to the field of ship hull design where the curves are plane intersections. The method is extended to the case where one considers, not the fairness of one curve, but the fairness of a one parameter family of curves. Six basic third order invariants by which the fairing measures can be expressed are defined. Furthermore, the geometry of a plane intersection curve is studied, and the variation of the total, the normal, and the geodesic curvature and the geodesic torsion is determined. 相似文献
26.
Deborah M. Greaves 《国际流体数值方法杂志》2006,50(6):693-711
An adaptive hierarchical grid‐based method for predicting complex free surface flows is used to simulate collapse of a water column. Adapting quadtree grids are combined with a high‐resolution interface‐capturing approach and pressure‐based coupling of the Navier–Stokes equations. The Navier–Stokes flow solution scheme is verified for simulation of flow in a lid‐driven cavity at Re=1000. Two approaches to the coupling of the Navier–Stokes equations are investigated as are alternative face velocity and hanging node interpolations. Collapse of a water column as well as collapse of a water column and its subsequent interaction with an obstacle are simulated. The calculations are made on uniform and adapting quadtree grids, and the accuracy of the quadtree calculations is shown to be the same as those made on the equivalent uniform grids. Results are in excellent agreement with experimental and other numerical data. A sharp interface is maintained at the free surface. The new adapting quadtree‐based method achieves a considerable saving in the size of the computational grid and CPU time in comparison with calculations made on equivalent uniform grids. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
27.
We obtain expressions for the energy spectrum widths of Rayleigh waves corresponding to their deformational coupling to Fermi and Boltzmann electrons in a two-dimensional layer near the surface of a semibounded solid. We evaluate the nonequilibrium energy of Rayleigh waves that depends on these widths and is caused by the same coupling to the corresponding hot electrons. We show that this energy is independent of the degeneracy degree of the electrons and is given by the mean energy of free Rayleigh waves heated up to temperature of the electrons. We find conditions under which the thermodynamics is determined by this nonequilibrium energy of Rayleigh waves in films of a certain thickness with Fermi electrons near the surface and by the equilibrium energy of bulk phonons in thicker samples. All the results are obtained using the Keldysh diagram technique applied to the case of semibounded media. 相似文献
28.
We predict ultraslow collapse of “tubular image states” (TIS) on material surfaces. TIS are bound Rydberg-like electronic states formed at large distances (∼30 nm) from the surfaces of suspended circularly-symmetric nanowires, such as metallic C nanotubes. The states are formed in potential wells, resulting from a combination of the TIS-electron attraction to image charges in the nanotube and its centrifugal repulsion, caused by spinning around the tube. We demonstrate that TIS can collapse on the tube surface by passing their angular momentum l to circularly polarized flexural phonons excited in the tube. Our analysis shows that for highly detached TIS with l ? 6 the relaxation lifetimes are of the order of 10 ns-1 μs, while for l < 6 these lifetimes are reduced by several orders of magnitude. 相似文献
29.
用三维TRS(totalrouthiansurface)自洽理论对奇奇核164Lu的位能面进行了计算,计算结果与实验上得到的ε2=0.38基本一致,从而从理论上确认了164Lu是三轴超形变核,并且指出了存在三轴超形变带的两个组态. Total routhian surface in~(164)Lu nuclei is calculated according to the three dimensional Total Routhian Surface (TRS) theory. The result of the calculation is in agreement with the experiment. At the same time, two TSD bands could be assigned to the configuration(π\(1/2), α=1/2)(ν\(5/2), α=1/2), (π\(1/2), α=1/2)(ν\(3/2), α=-1/2). 相似文献
30.
使用Monte Carlo模拟的方法得出了随机粗糙表面,在Kirchhoff近似的基础上,利用数值分析的方法分析了一维随机粗糙表面的散射特征,得出了一维随机粗糙表面散射分布曲线,我们还考虑了遮蔽效应的影响,并且讨论了Kirchhoff近似的有效性。 相似文献