全文获取类型
收费全文 | 32977篇 |
免费 | 2374篇 |
国内免费 | 3456篇 |
专业分类
化学 | 19868篇 |
晶体学 | 526篇 |
力学 | 1329篇 |
综合类 | 466篇 |
数学 | 4815篇 |
物理学 | 11803篇 |
出版年
2023年 | 174篇 |
2022年 | 522篇 |
2021年 | 690篇 |
2020年 | 612篇 |
2019年 | 582篇 |
2018年 | 688篇 |
2017年 | 796篇 |
2016年 | 902篇 |
2015年 | 963篇 |
2014年 | 1107篇 |
2013年 | 1643篇 |
2012年 | 1894篇 |
2011年 | 2095篇 |
2010年 | 1541篇 |
2009年 | 1504篇 |
2008年 | 2087篇 |
2007年 | 1986篇 |
2006年 | 1866篇 |
2005年 | 2071篇 |
2004年 | 2023篇 |
2003年 | 1474篇 |
2002年 | 1113篇 |
2001年 | 1036篇 |
2000年 | 1030篇 |
1999年 | 610篇 |
1998年 | 424篇 |
1997年 | 398篇 |
1996年 | 457篇 |
1995年 | 380篇 |
1994年 | 398篇 |
1993年 | 437篇 |
1992年 | 406篇 |
1991年 | 323篇 |
1990年 | 280篇 |
1989年 | 261篇 |
1988年 | 224篇 |
1987年 | 234篇 |
1986年 | 214篇 |
1985年 | 259篇 |
1984年 | 235篇 |
1983年 | 209篇 |
1982年 | 206篇 |
1981年 | 201篇 |
1980年 | 183篇 |
1979年 | 171篇 |
1978年 | 185篇 |
1977年 | 146篇 |
1976年 | 138篇 |
1974年 | 138篇 |
1973年 | 122篇 |
排序方式: 共有10000条查询结果,搜索用时 522 毫秒
91.
92.
93.
A. Ferreira da Silva I. Pepe S.A. Tomás W.M. de Azevedo R. Ahuja 《Applied Surface Science》2006,252(15):5365-5367
In this paper we present spectroscopic properties of doped and undoped titanium dioxide (TiO2) as nanofilms prepared by the sol-gel process with rhodamine 6G doping and studied by photoacoustic absorption, excitation and emission spectroscopy. The absorption spectra of TiO2 thin films doped with rhodamine 6G at very low concentration during their preparation show two absorption bands, one at 2.3 eV attributed to molecular dimmer formation, which is responsible for the fluorescence quenching of the sample and the other at 3.0 eV attributed to TiO2 absorption, which subsequently yields a strong emission band at 600 nm. The electronic band structure and optical properties of the rutile phase of TiO2 are calculated employing a fully relativistic, full-potential, linearized, augmented plane-wave (FPLAPW) method within the local density approximation (LDA). Comparison of this calculation with experimental data for TiO2 films prepared for undoped sol-gels and by sputtering is performed. 相似文献
94.
We have studied the interracial reactions between amorphous LaAlO3 thin films and Si substrates, using high- resolution transmission electron microscopy and x-ray photoelectron spectroscopy. It has been shown that the interracial layer between LaAlO3 film and Si substrate chemical states show that the ratio of La 4d3/2 to Al 2p is SiLaxAlyOz. The depth distributions of La, Si and Al of the interfacial layer remains unchanged with the depth compared to that of the LaAlO3 film. Moreover, the Si content, in the interracial layer gradually decreases with increasing thickness of the interracial layer. These results strongly suggest that the Al element is not deficient in the interracial layer, as previously believed, and the formation of a SiLaxAlyOz interracial layer is mainly due to the diffusion of Si from the substrate during the LaAlO3 film deposition. With the understanding of the interracial layer formation, ones can control the interface characteristics to ensure the desired performances of devices using high-k oxides as gate dielectrics. 相似文献
95.
Yong LU Hong WANG Ye LIU Ming Yuan HE 《中国化学快报》2006,17(10):1397-1400
Recently, miniature H2 generator to power fuel cells for portable/micro electronic devices and passenger propulsion has been the focus of intense research activities1-3. One of the strategies is to find simple CO-free H2 production with novel microreactor… 相似文献
96.
本文具体刻画有界Lipschitz域上的反射Brown运动跨过某给定时刻t的离开Martin边界的游程.在此基础上,给出Lipschitz域上的反射Brown运动的边界过程的Levy系统. 相似文献
97.
98.
Eliza P. de Jager 《Topology and its Applications》2007,154(10):2117-2126
We show that the infimum of any family of proximally symmetric quasi-uniformities is proximally symmetric, while the supremum of two proximally symmetric quasi-uniformities need not be proximally symmetric. On the other hand, the supremum of any family of transitive quasi-uniformities is transitive, while there are transitive quasi-uniformities whose infimum with their conjugate quasi-uniformity is not transitive. Moreover we present two examples that show that neither the supremum topology nor the infimum topology of two transitive topologies need be transitive. Finally, we prove that several operations one can perform on and between quasi-uniformities preserve the property of having a complement. 相似文献
99.
G.M. Ingo P. Plescia E. Angelini C. Riccucci T. de Caro 《Applied Physics A: Materials Science & Processing》2006,83(4):611-615
The surface microchemical structure of high tin leaded bronze Roman mirrors has been studied by means of scanning electron microscopy combined with energy dispersive spectrometry (SEM-EDS), X-ray diffraction (XRD) and optical microscopy (OM) techniques. The results allowed understanding of the origin of their high chemical stability and silvery-lustrous appearance. Indeed, some areas of the selected Roman mirrors are still characterised by a highly reflective and silver coloured surface even though they have been buried in the soil for about 2000 years. The micro-chemical results obtained from these areas have revealed that the mirror surface was tin enriched via inverse-segregation phenomenon by tailoring the cooling parameters. Furthermore, the presence of tin could be likely enhanced via cycles of oxidation and selective copper corrosion processes, thus resulting in a tin surface enrichment as a semi-transparent amorphous-like tin oxide (SnO2) film, as well as a copper depletion at the outer surfaces. 相似文献
100.
A. Craig W. H. Jacobson A. Meyer N. Welwart A. Seuthe H. N. Marr B. S. Evans G. E. F. Lundell J. A. Scherrer E. Stelling F. J. Mück A. Kling A. Lassieur L. Bertiaux C. C. Bissett P. de Pauw J. Heslinga A. Bartsch R. E. Lee W. H. Fegeley F. H. Reichel und E. Saz 《Fresenius' Journal of Analytical Chemistry》1927,71(1-2):83-90
Ohne Zusammenfassung 相似文献