全文获取类型
收费全文 | 5628篇 |
免费 | 527篇 |
国内免费 | 554篇 |
专业分类
化学 | 1239篇 |
晶体学 | 22篇 |
力学 | 2117篇 |
综合类 | 124篇 |
数学 | 1455篇 |
物理学 | 1752篇 |
出版年
2024年 | 13篇 |
2023年 | 48篇 |
2022年 | 94篇 |
2021年 | 176篇 |
2020年 | 164篇 |
2019年 | 129篇 |
2018年 | 145篇 |
2017年 | 219篇 |
2016年 | 339篇 |
2015年 | 236篇 |
2014年 | 287篇 |
2013年 | 365篇 |
2012年 | 307篇 |
2011年 | 326篇 |
2010年 | 280篇 |
2009年 | 330篇 |
2008年 | 336篇 |
2007年 | 318篇 |
2006年 | 302篇 |
2005年 | 275篇 |
2004年 | 263篇 |
2003年 | 222篇 |
2002年 | 181篇 |
2001年 | 175篇 |
2000年 | 151篇 |
1999年 | 137篇 |
1998年 | 119篇 |
1997年 | 120篇 |
1996年 | 92篇 |
1995年 | 94篇 |
1994年 | 77篇 |
1993年 | 46篇 |
1992年 | 46篇 |
1991年 | 39篇 |
1990年 | 42篇 |
1989年 | 29篇 |
1988年 | 29篇 |
1987年 | 24篇 |
1986年 | 19篇 |
1985年 | 21篇 |
1984年 | 18篇 |
1982年 | 15篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 11篇 |
1978年 | 10篇 |
1977年 | 5篇 |
1974年 | 4篇 |
1973年 | 4篇 |
1957年 | 4篇 |
排序方式: 共有6709条查询结果,搜索用时 15 毫秒
31.
遥感器CCD驱动器热设计及其在摄像过程中的温度变化 总被引:3,自引:3,他引:0
CCD驱动器是航天成像遥感器摄像过程中的主要热源之一。防止CCD驱动器过热是保证其正常工作的重要方面。介绍了遥感器的工作模式和对CCD驱动器采取的热控制措施。通过热平衡试验,利用回归的方法,对CCD驱动器在摄像过程中的温度变化规律进行了分析,同时对热控制效果进行了评估。CCD驱动器工作时升温速率在0.85℃/min左右,整个摄像过程中最高温度约为26℃,所实施的热控制措施效果理想。 相似文献
32.
Arnold Neumaier 《Journal of Global Optimization》2003,25(2):175-181
A family of multivariate rational functions is constructed. It has strong local minimizers with prescribed function values at prescribed positions. While there might be additional local minima, such minima cannot be global. A second family of multivariate rational functions is given, having prescribed global minimizers and prescribed interpolating data. 相似文献
33.
异方差回归中的广义方差比检验 总被引:1,自引:0,他引:1
在同方差假设之下,线性模型在回归分析的理论与应用方面起着突出的作用,很受许多研究工作者的青睐.然而,回归模型中同方差性这一标准假设不一定总是成立的.因此我们考虑了用一类基于似残差的方法来检验异方差情形下线性模型拟合观测数据的情况.本文既给出了大量的模拟,又给出了实际数据作为应用的例子.效果都很好. 相似文献
34.
35.
The load-carrying capacity of circular plates made of a fiber-reinforced composite and loaded with axisymmetric transverse forces under axisymmetric boundary conditions is investigated. The plates can be freely supported or clamped along their contour. To the known yield condition used, in the plane of main bending moments, there correspond irregular hexagons, which depend on the mechanical properties of composite constituents and some characteristic geometrical parameters. It is shown that, depending on the ratio of ultimate radial and circumferential bending moments, in the plastic state, the circular plates (the central part of the clamped plates) take the form of a cone or a frustum of cone. For each of the cases, the limit load is found, which is a function of the above-mentioned mechanical parameters. The statically allowable fields of bending moments and the corresponding allowable fields of deflection rates are determined. The solutions found are exact. Special cases for the freely supported plates are analyzed, and the results obtained are presented in the form of graphs.__________Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 2, pp. 177–192, March–April, 2005. 相似文献
36.
Effect of a Shock Pulse on a Floating Ice Sheet 总被引:1,自引:0,他引:1
The vibrations of a viscoelastic plate lying on an elastic liquid base subjected to pulse loading have been studied theoretically and experimentally. The effect of the variable depth of the reservoir, plate thickness, and strain relaxation time on the value of the plate vibration amplitude and the length and curvature of the flexural gravity wave profile are analyzed. Good agreement of theoretical and experimental results is obtained. 相似文献
37.
Peter Amrhein 《Annals of the Institute of Statistical Mathematics》1995,47(1):167-170
Although the theory of rank tests is rather complete in the one-sided case, it was not even known in 1959, whether the Wilcoxon two-sample test and other similar tests are unbiased against the two-sided alternatives (Lehmann (1959,Testing Statistical Hypotheses, p. 240, Wiley, New York)). A partial answer to this question was given by Sugiura in 1965, who found, that the test named above may be biased (Sugiura (1965,Ann. Inst. Statist. Math.,17, 261–263)). According to Lehmann (1986,Testing Statistical Hypotheses, 2nd ed., pp. 322–324, Wiley, New York) it seems to be still open, whether the same is true for the WILCOXON one-sample test, which is also known as WILCOXON signed rank test. This will be shown in the present paper. 相似文献
38.
Testing for additivity with B-splines 总被引:1,自引:0,他引:1
Regression splines are often used for fitting nonparametric functions, and they work especially well for additivity models. In this paper, we consider two simple tests of additivity: an adaptation of Tukey's one degree of freedom test and a nonparametric version of Rao's score test. While the Tukey-type test can detect most forms of the local non-additivity at the parametric rate of O(n-1/2), the score test is consistent for all alternative at a nonparametric rate. The asymptotic distribution of these test statistics is derived under both the null and local alternative hypotheses. A simulation study is conducted to compare their finite-sample performances with some existing kernel-based tests. The score test is found to have a good overall performance. 相似文献
39.
李辉 《宁波大学学报(理工版)》1995,(1)
本文对低叠合面钢筋破简支在合梁二阶段受力的斜截面抗剪性能进行了试验研究,并运用非线性有限元分析和试验实测数据,得出了一个适合于集中荷载下高低叠合面叠合梁的抗剪强度计算公式. 相似文献
40.