全文获取类型
收费全文 | 6430篇 |
免费 | 698篇 |
国内免费 | 611篇 |
专业分类
化学 | 949篇 |
晶体学 | 91篇 |
力学 | 615篇 |
综合类 | 125篇 |
数学 | 4546篇 |
物理学 | 1413篇 |
出版年
2024年 | 7篇 |
2023年 | 62篇 |
2022年 | 87篇 |
2021年 | 101篇 |
2020年 | 163篇 |
2019年 | 200篇 |
2018年 | 179篇 |
2017年 | 211篇 |
2016年 | 242篇 |
2015年 | 188篇 |
2014年 | 325篇 |
2013年 | 563篇 |
2012年 | 306篇 |
2011年 | 393篇 |
2010年 | 333篇 |
2009年 | 372篇 |
2008年 | 412篇 |
2007年 | 407篇 |
2006年 | 346篇 |
2005年 | 319篇 |
2004年 | 270篇 |
2003年 | 253篇 |
2002年 | 295篇 |
2001年 | 249篇 |
2000年 | 243篇 |
1999年 | 214篇 |
1998年 | 176篇 |
1997年 | 168篇 |
1996年 | 113篇 |
1995年 | 75篇 |
1994年 | 62篇 |
1993年 | 45篇 |
1992年 | 34篇 |
1991年 | 43篇 |
1990年 | 22篇 |
1989年 | 30篇 |
1988年 | 27篇 |
1987年 | 21篇 |
1986年 | 14篇 |
1985年 | 29篇 |
1984年 | 28篇 |
1983年 | 15篇 |
1982年 | 18篇 |
1981年 | 14篇 |
1980年 | 12篇 |
1979年 | 15篇 |
1978年 | 12篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1973年 | 3篇 |
排序方式: 共有7739条查询结果,搜索用时 46 毫秒
21.
袁文俊 《数学物理学报(A辑)》2003,23(2):224-230
该文考虑具有控制系数 A\-0 和系数仅有有限个极点的高阶线性齐次微分方程(1.1)。得到了一个复振荡结果,该结果是J. K. Langley[11]等作者在整系数下相应结果的推广。 相似文献
22.
We obtain exponential upper bounds for tails of distributions of generalized L-statistics based on a sample from an exponential distribution. We prove the asymptotic normality of generalized L-statistics based on a sample from the uniform distribution on [0,1] and of L-statistics with decomposed kernels (without any restrictions on the sample distribution type). 相似文献
23.
24.
Some new oscillation criteria are established for a second order neutral delay differential equations. These results improve oscillation results of Y.V. Rogo-vchenko for the retarded delay differential equations. The relevance of our theorems is illustrated with two carefully selected examples. 相似文献
25.
Naus Joseph I. Wallenstein Sylvan 《Methodology and Computing in Applied Probability》2004,6(4):389-400
Researchers apply scan statistics to test for unusually large clusters of events within a time window of specified length w, or alternatively an unusually small window w that contains a specified number of events. In some cases, the researcher is interested in testing for a range of specified window lengths, or a set of several specified number of events k (cluster sizes). In this paper, we derive accurate approximations for the joint distributions of scan statistics for a range of values of w, or of k, that can be used to set an experiment-wide level of significance that takes into account the multiple comparisons involved. We use these methods to compare different ways of choosing the window sizes for the different cluster sizes. One special case is a multiple comparison procedure based on a generalized likelihood ratio test (GLRT) for a range of window sizes. We compare the power of the GLRT with another method for allocating the window sizes. We find that the GLRT is sensitive for very small window sizes at the expense of moderate and larger window sizes. We illustrate these results on two examples, one involving clustering of translocation breakpoints in DNA, and the other involving disease clusters. 相似文献
26.
John A. Ekaterinaris 《国际流体数值方法杂志》2004,45(11):1187-1207
A high‐order accurate, finite‐difference method for the numerical solution of incompressible flows is presented. This method is based on the artificial compressibility formulation of the incompressible Navier–Stokes equations. Fourth‐ or sixth‐order accurate discretizations of the metric terms and the convective fluxes are obtained using compact, centred schemes. The viscous terms are also discretized using fourth‐order accurate, centred finite differences. Implicit time marching is performed for both steady‐state and time‐accurate numerical solutions. High‐order, spectral‐type, low‐pass, compact filters are used to regularize the numerical solution and remove spurious modes arising from unresolved scales, non‐linearities, and inaccuracies in the application of boundary conditions. The accuracy and efficiency of the proposed method is demonstrated for test problems. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
27.
Yuh-Shan Ho 《Adsorption》2004,10(2):151-158
The kinetics of four sorption systems, Cu/tree fern, Pb/tree fern, AB9/activated clay and BR18/activated clay have been studied based on the assumption of a pseudo-second order rate law. Pseudo-isotherms using the pseudo-second order kinetic expression constant have been developed to describe the four liquid-solid sorption systems. The experimental results have been analyzed using a pseudo-Langmuir and a pseudo-Redlich-Peterson isotherm. Both isotherms were found to represent the measured sorption data well. According to the evaluation using the pseudo-Langmuir equation, the monolayer sorption capacities were obtained to be 13.9, 46.6, 124 and 105 mg g–1 for copper, lead, AB9 and BR18 respectively. 相似文献
28.
29.
The rotating flow in the presence of a magnetic field is a problem belonging to hydromagnetics and deserves to be more widely studied than it has been to date. In the non‐linear regime the literature is scarce. We develop the governing equations for the unsteady hydromagnetic rotating flow of a fourth‐order fluid past a porous plate. The steady flow is governed by a boundary value problem in which the order of differential equations is more than the number of available boundary conditions. It is shown that by augmenting the boundary conditions based on asymptotic structures at infinity it is possible to obtain numerical solutions of the nonlinear hydromagnetic equations. Effects of uniform suction or blowing past the porous plate, exerted magnetic field and rotation on the flow phenomena, especially on the boundary layer structure near the plate, are numerically analysed and discussed. The flow behaviours of the Newtonian fluid and second‐, third‐ and fourth‐order non‐Newtonian fluids are compared for the special flow problem, respectively. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
30.
Toshihiro Kobayashi 《Mathematical Methods in the Applied Sciences》2004,27(18):2171-2184
In this paper low‐gain adaptive stabilization of undamped semilinear second‐order hyperbolic systems is considered in the case where the input and output operators are collocated. The linearized systems have an infinite number of poles and zeros on the imaginary axis. The adaptive stabilizer is constructed by a low‐gain adaptive velocity feedback. The closed‐loop system is governed by a non‐linear evolution equation. First, the well‐posedness of the closed‐loop system is shown. Next, an energy‐like function and a multiplier function are introduced and the exponential stability of the closed‐loop system is analysed. Some examples are given to illustrate the theory. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献