全文获取类型
收费全文 | 30847篇 |
免费 | 3046篇 |
国内免费 | 1926篇 |
专业分类
化学 | 3056篇 |
晶体学 | 52篇 |
力学 | 3204篇 |
综合类 | 359篇 |
数学 | 23207篇 |
物理学 | 5941篇 |
出版年
2024年 | 34篇 |
2023年 | 285篇 |
2022年 | 270篇 |
2021年 | 472篇 |
2020年 | 759篇 |
2019年 | 816篇 |
2018年 | 781篇 |
2017年 | 857篇 |
2016年 | 948篇 |
2015年 | 740篇 |
2014年 | 1356篇 |
2013年 | 2945篇 |
2012年 | 1414篇 |
2011年 | 1686篇 |
2010年 | 1460篇 |
2009年 | 1941篇 |
2008年 | 1922篇 |
2007年 | 1967篇 |
2006年 | 1791篇 |
2005年 | 1507篇 |
2004年 | 1366篇 |
2003年 | 1271篇 |
2002年 | 1279篇 |
2001年 | 1021篇 |
2000年 | 961篇 |
1999年 | 876篇 |
1998年 | 733篇 |
1997年 | 660篇 |
1996年 | 510篇 |
1995年 | 418篇 |
1994年 | 372篇 |
1993年 | 274篇 |
1992年 | 270篇 |
1991年 | 203篇 |
1990年 | 177篇 |
1989年 | 136篇 |
1988年 | 113篇 |
1987年 | 104篇 |
1986年 | 98篇 |
1985年 | 135篇 |
1984年 | 166篇 |
1983年 | 72篇 |
1982年 | 120篇 |
1981年 | 103篇 |
1980年 | 94篇 |
1979年 | 92篇 |
1978年 | 71篇 |
1977年 | 55篇 |
1976年 | 44篇 |
1974年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
51.
52.
Bifurcation analysis of visual angle model with anticipated time and stabilizing driving behavior 下载免费PDF全文
Xueyi Guan 《中国物理 B》2022,31(7):70507-070507
In the light of the visual angle model (VAM), an improved car-following model considering driver's visual angle, anticipated time and stabilizing driving behavior is proposed so as to investigate how the driver's behavior factors affect the stability of the traffic flow. Based on the model, linear stability analysis is performed together with bifurcation analysis, whose corresponding stability condition is highly fit to the results of the linear analysis. Furthermore, the time-dependent Ginzburg-Landau (TDGL) equation and the modified Korteweg-de Vries (mKdV) equation are derived by nonlinear analysis, and we obtain the relationship of the two equations through the comparison. Finally, parameter calibration and numerical simulation are conducted to verify the validity of the theoretical analysis, whose results are highly consistent with the theoretical analysis. 相似文献
53.
A new third‐order WENO scheme is proposed to achieve the desired order of convergence at the critical points for scalar hyperbolic equations. A new reference smoothness indicator is introduced, which satisfies the sufficient condition on the weights for the third‐order convergence. Following the truncation error analysis, we have shown that the proposed scheme achieves the desired order accurate for smooth solutions with arbitrary number of vanishing derivatives if the parameter ε satisfies certain conditions. We have made a comparative study of the proposed scheme with the existing schemes such as WENO‐JS, WENO‐Z, and WENO‐N3 through different numerical examples. The result shows that the proposed scheme (WENO‐MN3) achieves better performance than these schemes. 相似文献
54.
《Mathematische Nachrichten》2018,291(10):1470-1485
In this paper we study a class of second order coefficient operators differential equation with general (possibly non local) boundary conditions. We obtain new results extending those given in a previous paper 1 . Existence, uniqueness and optimal regularity of the strict solution are proved in UMD spaces, using the well‐known Dore–Venni theorem. 相似文献
55.
近来有些文章断言,在一个惯性参考系里能量守恒的物理系统,在别的参考系看来能量也一定守恒.实际上这些作者混淆了物理方程式的协变性和相对性原理.本文将澄清这一误解. 相似文献
56.
57.
P. A. Martin 《Mathematical Methods in the Applied Sciences》2020,43(15):8906-8929
In some circumstances, sound waves in a rarefied gas can be studied using a linearised form of the regularised 13-moment equations of Struchtrup and Torrilhon. We build solutions of those equations in spherical polar coordinates using vector spherical harmonics. We first solve a reduced system of equations (with 11 unknowns) after introduction of a force vector (divergence of the stress). We then show that the stresses themselves can be recovered by solving five additional equations. The results obtained are expected to be useful for problems such as acoustic scattering of a plane wave by a sphere in a rarefied gas. 相似文献
58.
59.
Lennon Ó Náraigh 《The Journal of mathematical sociology》2020,44(1):42-64
ABSTRACTWe introduce a model based on Ordinary Differential Equations to describe how two mutually exclusive groups progress through a career hierarchy, whether in a single organization, or in an entire economic sector. The intended application is to gender imbalance at the top of the academic hierarchy in European Universities; however, the model is entirely generic and may be applied in other contexts also. Previous research on gender imbalance in European universities has focused on large-scale statistical studies. Our model represents a point of departure, as it is deterministic (i.e., based on Ordinary Differential Equations). The model requires a precise definition of the progression rates for the different groups through the hierarchy; these are key parameters governing the dynamics of career progression. The progression rate for each group can be decomposed into a product: the proportion of group members at a low level in the hierarchy who compete for promotion to the next level a given year, multiplied by the in-competition success rate for the group in question. Either of these two parameters can differ across the groups under consideration; this introduces a group asymmetry into the organization’s composition. We introduce a glass-ceiling index to summarize this asymmetry succinctly. Using case studies from the literature, we demonstrate how the mathematical framework can pinpoint the proximate cause of the glass ceiling in European academia. 相似文献
60.