全文获取类型
收费全文 | 4849篇 |
免费 | 1119篇 |
国内免费 | 394篇 |
专业分类
化学 | 120篇 |
晶体学 | 1篇 |
力学 | 588篇 |
综合类 | 114篇 |
数学 | 3486篇 |
物理学 | 2053篇 |
出版年
2024年 | 3篇 |
2023年 | 58篇 |
2022年 | 84篇 |
2021年 | 115篇 |
2020年 | 132篇 |
2019年 | 108篇 |
2018年 | 122篇 |
2017年 | 134篇 |
2016年 | 154篇 |
2015年 | 95篇 |
2014年 | 211篇 |
2013年 | 405篇 |
2012年 | 248篇 |
2011年 | 284篇 |
2010年 | 287篇 |
2009年 | 318篇 |
2008年 | 356篇 |
2007年 | 367篇 |
2006年 | 383篇 |
2005年 | 327篇 |
2004年 | 224篇 |
2003年 | 260篇 |
2002年 | 253篇 |
2001年 | 233篇 |
2000年 | 183篇 |
1999年 | 169篇 |
1998年 | 152篇 |
1997年 | 134篇 |
1996年 | 90篇 |
1995年 | 83篇 |
1994年 | 67篇 |
1993年 | 48篇 |
1992年 | 50篇 |
1991年 | 32篇 |
1990年 | 30篇 |
1989年 | 17篇 |
1988年 | 14篇 |
1987年 | 20篇 |
1986年 | 26篇 |
1985年 | 26篇 |
1984年 | 10篇 |
1983年 | 13篇 |
1982年 | 9篇 |
1981年 | 10篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 5篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1957年 | 4篇 |
排序方式: 共有6362条查询结果,搜索用时 15 毫秒
121.
We extend the concept of the difference dimension polynomial of a difference field extension to difference local algebras. The main theorem of the paper establishes the existence and form of the dimension polynomial associated with the localization of a finitely generated well-mixed difference algebra at a prime reflexive difference ideal. 相似文献
122.
123.
Sheldon P. Gordon 《International Journal of Mathematical Education in Science & Technology》2017,48(3):455-473
This article takes a closer look at the problem of approximating the exponential and logarithmic functions using polynomials. Either as an alternative to or a precursor to Taylor polynomial approximations at the precalculus level, interpolating polynomials are considered. A measure of error is given and the behaviour of the error function is analysed. The results of interpolating polynomials are compared with those of Taylor polynomials. 相似文献
124.
LAO HUI-XUE 《东北数学》2012,28(2)
Under the assumption of sixth power large sieve mean-value of Dirichlet L-function,we improve Bombieri's theorem in short intervals by virtue of the large sieve method and Heath-Brown's identity. 相似文献
125.
Experiments were carried out to observe the effect of a magnetic field and grid biasing voltage in presence of a plasma bubble in a magnetized, filamentary discharge plasma system. A spherical mesh grid of 80% optical transparency was negatively biased and introduced into the plasma for creating a plasma bubble. Diagnostics via an electrical Langmuir probe and a hot emissive probe were extensively used for scanning the plasma bubble. Plasma floating potential fluctuations were measured at three different positions of the plasma bubble. The instability in the pattern showed the dynamic transition from periodic to chaotic for increasing magnetic fields. Time scale analysis using continuous wavelet transform was carried out to identify the presence of non‐linearity from the contour plots. The mechanisms of the low‐frequency instabilities along with the transition to chaos could be qualitatively explained. Non‐linear techniques such as fast Fourier transform, phase space plot, and recurrence plot were used to explore the dynamics of the system appearing during plasma fluctuations. In order to demonstrate the observed chaotic phenomena in this study, characteristics of chaos such as the Lyapunov exponent were obtained from experimental time series data. The experimentally observed potential structure is confirmed with numerical analysis based on fluid hydrodynamics. 相似文献
126.
Hai Q. Dinh Xiaoqiang Wang Hongwei Liu Songsak Sriboonchitta 《Discrete Mathematics》2019,342(5):1456-1470
Let be an odd prime, , be positive integers, be nonzero elements of the finite field such that . In this paper, we show that, for any positive integer , the Hamming distances of all repeated-root -constacyclic codes of length can be determined by those of certain simple-root -constacyclic codes of length . Using this result, Hamming distances of all constacyclic codes of length are obtained. As an application, we identify all MDS -constacyclic codes of length . 相似文献
127.
After our article, Physica A 391 (2012) 107–112, had been published online, T. Hillen told us about a theorem by Osaki, relevant for our numerical simulations. 相似文献
129.
Jianglin Zhao Yong Yan Lizhuang Huang Run Yang 《Mathematical Methods in the Applied Sciences》2019,42(11):3831-3847
This paper deals with a diffusive toxin producing phytoplankton‐zooplankton model with maturation delay. By analyzing eigenvalues of the characteristic equation associated with delay parameter, the stability of the positive equilibrium and the existence of Hopf bifurcation are studied. Explicit results are derived for the properties of bifurcating periodic solutions by means of the normal form theory and the center manifold reduction for partial functional differential equations. Numerical simulations not only agree with the theoretical analysis but also exhibit the complex behaviors such as the period‐3, 5, 6, 7, 8, 11, and 12 solutions, cascade of period‐doubling bifurcation in period‐2, 4, quasi‐periodic solutions, and chaos. The key observation is that time delay may control harmful algae blooms (HABs). Moreover, numerical simulations show that the chaotic states induced by the period‐doubling bifurcation are purely temporal, which is stationary in space and oscillatory in time. The investigations may provide some new insights on harmful phytoplankton blooms. 相似文献
130.