全文获取类型
收费全文 | 55676篇 |
免费 | 2184篇 |
国内免费 | 34篇 |
专业分类
化学 | 36008篇 |
晶体学 | 297篇 |
力学 | 1765篇 |
综合类 | 5篇 |
数学 | 8343篇 |
物理学 | 11476篇 |
出版年
2023年 | 422篇 |
2022年 | 432篇 |
2021年 | 718篇 |
2020年 | 838篇 |
2019年 | 824篇 |
2018年 | 1176篇 |
2017年 | 935篇 |
2016年 | 1796篇 |
2015年 | 1623篇 |
2014年 | 1671篇 |
2013年 | 3334篇 |
2012年 | 3857篇 |
2011年 | 3980篇 |
2010年 | 2445篇 |
2009年 | 2071篇 |
2008年 | 3410篇 |
2007年 | 3383篇 |
2006年 | 2963篇 |
2005年 | 2826篇 |
2004年 | 2432篇 |
2003年 | 1957篇 |
2002年 | 1711篇 |
2001年 | 1041篇 |
2000年 | 872篇 |
1999年 | 618篇 |
1998年 | 476篇 |
1997年 | 431篇 |
1996年 | 524篇 |
1995年 | 342篇 |
1994年 | 416篇 |
1993年 | 415篇 |
1992年 | 441篇 |
1991年 | 358篇 |
1990年 | 344篇 |
1989年 | 332篇 |
1988年 | 276篇 |
1987年 | 268篇 |
1986年 | 238篇 |
1985年 | 402篇 |
1984年 | 371篇 |
1983年 | 267篇 |
1982年 | 344篇 |
1981年 | 341篇 |
1980年 | 293篇 |
1979年 | 292篇 |
1978年 | 274篇 |
1976年 | 275篇 |
1975年 | 250篇 |
1974年 | 257篇 |
1973年 | 249篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
A tomographic reconstruction method based on Monte Carlo random searching guided by the information contained in the projections
of radiographed objects is presented. In order to solve the optimization problem, a multiscale algorithm is proposed to reduce
computation. The reconstruction is performed in a coarse-to-fine multigrid scale that initializes each resolution level with
the reconstruction of the previous coarser level, which substantially improves the performance. The method was applied to
a real case reconstructing the internal structure of a small metallic object with internal components, showing excellent results. 相似文献
93.
E. Rodriguez E. Jimenez G.J. Jacob A.A.R. Neves C.L. Cesar L.C. Barbosa 《Physica E: Low-dimensional Systems and Nanostructures》2005,26(1-4):361
Multilayer PbTe quantum dots (QDs) and SiO2 were grown by pulsed laser deposition (PLD) and Plasma enhanced chemical vapor deposition (PECVD) techniques. The crystalline structure, QD size and size dispersion were observed by high-resolution transmission electron microscopy (HRTEM) measurements. This technique allows one to grow PbTe QDs as small as 1.8 nm diameter and 0.6 nm size dispersion. The whole structure can be used in a Fabry–Perot cavity for an optical device operating at the mid-infrared region. 相似文献
94.
Mrio J. Edmundo 《Mathematical Logic Quarterly》2005,51(6):639-641
We show that if G is a definably compact, definably connected definable group defined in an arbitrary o‐minimal structure, then G is divisible. Furthermore, if G is defined in an o‐minimal expansion of a field, k ∈ ? and pk : G → G is the definable map given by pk (x ) = xk for all x ∈ G , then we have |(pk )–1(x )| ≥ kr for all x ∈ G , where r > 0 is the maximal dimension of abelian definable subgroups of G . (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
95.
Ana Luísa Daniel‐da‐Silva João Carlos Moura Bordado José Miguel Martín‐Martínez 《Journal of Polymer Science.Polymer Physics》2007,45(22):3034-3045
The degree of phase separation in several moisture‐cured poly(urethane urea)s (PUUs) was studied by FTIR spectroscopy, wide angle X‐ray diffraction (WAXD), and temperature‐modulated differential scanning calorimetry (TMDSC). This latter technique was shown to be particularly useful in analysing the degree of phase separation in PUU polymers. Both phase mixing and phase segregation coexisted in the PUUs and the degree of phase separation increased as the urea hard segment (HS) content in the PUU increased. The maximum solubility of urea HSs into the polyol soft segments (SSs) was achieved for 50 wt % urea HS content in diol‐based PUUs, whereas for triol‐based PUUs the highest solubility between HS and SS was reached for lower urea HS amount. Finally, the higher the urea HS content the higher the extent of phase separation in the PUU. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 3034–3045, 2007 相似文献
96.
97.
Artur Erdélyi 《Monatshefte für Mathematik》1939,47(1):87-103
Ohne Zusammenfassung 相似文献
98.
99.
We introduce here some Itô calculus for non-continuous Dirichlet processes. Such calculus extends what was known for continuous Dirichlet processes or for semimartingales. In particular we prove that non-continuous Dirichlet processes are stable under C
1 transformation. 相似文献
100.
Régine Barthelmé 《Comptes Rendus Mathematique》2005,341(11):689-694
This Note introduces a new integral form of the charge and current deposition scheme given in 1992 by Villasenor and Buneman, which permits the conservation of charge in PIC codes. This integral form extends directly to higher order spline shape factors, whose use produces less numerical noise. We thus get a discrete charge conserving method for high order shape factors. This method extends easily to nonuniform Cartesian grids for first order shape factors. To cite this article: R. Barthelmé, C. R. Acad. Sci. Paris, Ser. I 341 (2005). 相似文献