全文获取类型
收费全文 | 23146篇 |
免费 | 3746篇 |
国内免费 | 3521篇 |
专业分类
化学 | 16926篇 |
晶体学 | 386篇 |
力学 | 1317篇 |
综合类 | 318篇 |
数学 | 2692篇 |
物理学 | 8774篇 |
出版年
2024年 | 52篇 |
2023年 | 378篇 |
2022年 | 737篇 |
2021年 | 776篇 |
2020年 | 840篇 |
2019年 | 902篇 |
2018年 | 780篇 |
2017年 | 815篇 |
2016年 | 1092篇 |
2015年 | 1153篇 |
2014年 | 1353篇 |
2013年 | 1702篇 |
2012年 | 2060篇 |
2011年 | 2038篇 |
2010年 | 1454篇 |
2009年 | 1468篇 |
2008年 | 1666篇 |
2007年 | 1564篇 |
2006年 | 1432篇 |
2005年 | 1182篇 |
2004年 | 976篇 |
2003年 | 823篇 |
2002年 | 921篇 |
2001年 | 805篇 |
2000年 | 626篇 |
1999年 | 503篇 |
1998年 | 381篇 |
1997年 | 277篇 |
1996年 | 286篇 |
1995年 | 250篇 |
1994年 | 192篇 |
1993年 | 185篇 |
1992年 | 129篇 |
1991年 | 108篇 |
1990年 | 104篇 |
1989年 | 80篇 |
1988年 | 62篇 |
1987年 | 54篇 |
1986年 | 44篇 |
1985年 | 53篇 |
1984年 | 21篇 |
1983年 | 18篇 |
1982年 | 17篇 |
1981年 | 10篇 |
1980年 | 10篇 |
1979年 | 9篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1936年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
51.
Thin films of polystyrene (PS), poly(methyl methacrylate) (PMMA) and polystyrene-polyacrylonitrile copolymer (PS-AN), containing various embedded transition-metal complexes, have been studied by FTIR microscopy. The spatial distributions of the transition-metal carbonyl complexes throughout the thin organic polymer films have been determined by a two-dimensional IR mapping procedure. The spectral variations observed in the distribution of the metal carbonyls throughout the different polymer films are discussed. The IR data show that the technique used to prepare the organometallic-embedded thin films (viz. freeze-drying of solutions followed by hot mechanical pressing of the residues) does in general lead to homogeneous films which may eventually find industrial application, e.g. as membrane sensors for small molecules. 相似文献
52.
A PICARD TYPE THEOREM AND BLOCH LAW 总被引:9,自引:0,他引:9
Ye Yasheng 《数学年刊B辑(英文版)》1994,15(1):75-80
A PICARD TYPE THEOREM AND BLOCH LAW ¥YEYASHENGAbstract:Apicardtypetheoremisproved,andacounterexampleisgiventoshowthattheBolch... 相似文献
53.
Guo Qing LI Zhong Jiao JIA 《中国化学快报》2003,14(1):62-65
Two new ionone derivatives,named rhododendrone and rhododendronside,were isolated from the alcohoilc extract of the aerial parts of Rhododendron przwalskii Maxim.Their structures were elucidated on the basis of spectroscopic analysis. 相似文献
54.
Bai-suo JIN~ 《中国科学A辑(英文版)》2007,50(9):1303-1315
In the factor analysis model with large cross-section and time-series dimensions,we pro- pose a new method to estimate the number of factors.Specially if the idiosyncratic terms satisfy a linear time series model,the estimators of the parameters can be obtained in the time series model. The theoretical properties of the estimators are also explored.A simulation study and an empirical analysis are conducted. 相似文献
55.
56.
This article focuses on discontinuous Galerkin method for the two‐ or three‐dimensional stationary incompressible Navier‐Stokes equations. The velocity field is approximated by discontinuous locally solenoidal finite element, and the pressure is approximated by the standard conforming finite element. Then, superconvergence of nonconforming finite element approximations is applied by using least‐squares surface fitting for the stationary Navier‐Stokes equations. The method ameliorates the two noticeable disadvantages about the given finite element pair. Finally, the superconvergence result is provided under some regular assumptions. © 2006 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 23: 421–436, 2007 相似文献
57.
58.
We prove some basic properties of Donaldson’s flow of surfaces in a hyperkähler 4-manifold. When the initial submanifold is symplectic with respect to one Kähler form and Lagrangian with respect to another, we show that certain kinds of singularities cannot form, and we prove a convergence result under a condition related to one considered by M.-T. Wang for the mean curvature flow. 相似文献
59.
不确定市场条件下的稳健最优投资组合 总被引:1,自引:0,他引:1
本文假设风险资产和无风险资产收益的相关参数属于某个已知的凸多面体,分别讨论了在市场不存在无风险资产和存在无风险资产的情况下稳健最优投资组合问题,给出了问题的解析解,从而推广了Markowitz均值-方差模型的结果. 相似文献
60.
Z.J. Liu H.H. Long W.C. Ye X.X. Zou Z.L. Qin E.P. Li J.S. Chen 《Journal of magnetism and magnetic materials》2006
In this paper, specific issues related to high-density perpendicular magnetic recording processes, such as transition noise properties and cross-track correlation lengths, were investigated with the help of micromagnetic analysis. The effects of media parameters were taken into consideration, including intergranular exchange coupling, and exchange distribution, irregular grain shapes, magnetization saturation distribution, and anisotropy distribution. The micromagnetic simulation results showed that the effect of anisotropy distribution on transition noise is more significant than magnetization saturation distribution, and it is crucial to reduce this effect to achieve a high signal-to-noise ratio. Additionally, a new method to further estimate the partial erasure threshold was proposed to approximate the partial erasure effects, and the relation between the microtrack jitter and total track jitter was investigated. 相似文献