全文获取类型
收费全文 | 6004篇 |
免费 | 272篇 |
国内免费 | 28篇 |
专业分类
化学 | 4762篇 |
晶体学 | 20篇 |
力学 | 114篇 |
数学 | 578篇 |
物理学 | 830篇 |
出版年
2024年 | 6篇 |
2023年 | 62篇 |
2022年 | 94篇 |
2021年 | 110篇 |
2020年 | 135篇 |
2019年 | 155篇 |
2018年 | 124篇 |
2017年 | 106篇 |
2016年 | 242篇 |
2015年 | 186篇 |
2014年 | 196篇 |
2013年 | 306篇 |
2012年 | 526篇 |
2011年 | 597篇 |
2010年 | 270篇 |
2009年 | 205篇 |
2008年 | 445篇 |
2007年 | 440篇 |
2006年 | 448篇 |
2005年 | 413篇 |
2004年 | 293篇 |
2003年 | 253篇 |
2002年 | 209篇 |
2001年 | 63篇 |
2000年 | 33篇 |
1999年 | 27篇 |
1998年 | 31篇 |
1997年 | 32篇 |
1996年 | 28篇 |
1995年 | 23篇 |
1994年 | 16篇 |
1993年 | 22篇 |
1992年 | 15篇 |
1991年 | 16篇 |
1990年 | 11篇 |
1989年 | 9篇 |
1988年 | 8篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 18篇 |
1984年 | 13篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1981年 | 10篇 |
1980年 | 6篇 |
1979年 | 10篇 |
1977年 | 13篇 |
1976年 | 7篇 |
1971年 | 4篇 |
1967年 | 5篇 |
排序方式: 共有6304条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Matthew H Ervin 《Microscopy and microanalysis》2003,9(1):18-28
The environmental cell device discussed in this paper provides a modest low-vacuum scanning electron microscopy (SEM) capability to a standard SEM without requiring additional pumping. This environmental cell confines a volume of low vacuum in contact with the sample surface using a container that has an aperture for admitting the primary electron beam. The aperture is large enough to permit a limited field of view of the sample, and small enough to limit the outflow of gas into the SEM chamber to that which can be accommodated by the standard SEM pumping system. This environmental cell also functions as a gaseous detector device. 相似文献
5.
Matthew Foreman Stevo Todorcevic 《Transactions of the American Mathematical Society》2005,357(5):1693-1715
This paper establishes a refinement of the classical Löwenheim-Skolem theorem. The main result shows that any first order structure has a countable elementary substructure with strong second order properties. Several consequences for Singular Cardinals Combinatorics are deduced from this.
6.
The XYZ model describes the interaction between nuclear probes and an electric field gradient that fluctuates among three orthogonal
directions. The model presents a means to calculate the perturbation function that represents spectra obtained using perturbed
angular correlation spectroscopy. Three analytic approximations of the perturbation function have been developed previously,
and they are evaluated in the present paper in the context of Cd jumping among In-lattice sites in In3La. 相似文献
7.
Matthew D. Horton 《Linear algebra and its applications》2007,425(1):130-142
After defining and exploring some of the properties of Ihara zeta functions of digraphs, we improve upon Kotani and Sunada’s bounds on the poles of Ihara zeta functions of undirected graphs by considering digraphs whose adjacency matrices are directed edge matrices. 相似文献
8.
9.
We demonstrate that the 3-power torsion points of the Jacobians of the principal modular curves X(3n) are fixed by the kernel of the canonical outer Galois representation of the pro-3 fundamental group of the projective line
minus three points. The proof proceeds by demonstrating the curves in question satisfy a two-part criterion given by Anderson
and Ihara. Two proofs of the second part of the criterion are provided; the first relies on a theorem of Shimura, while the
second uses the moduli interpretation.
Received: 30 September 2005 相似文献
10.
Radical reaction of a series of N-(2-bromoallyl)arylcarboxamides led to the production of 4-arylpyrrolidin-2-ones and directly reduced materials in comparable yields. A cascade process, involving sequential 5-exo-trig spirocyclisation, β-scission, and 5-endo-trig cyclisation of the resulting acyl radical, is proposed to explain the pyrrolidinone products. 相似文献