全文获取类型
收费全文 | 16000篇 |
免费 | 384篇 |
国内免费 | 82篇 |
专业分类
化学 | 9131篇 |
晶体学 | 108篇 |
力学 | 548篇 |
数学 | 2394篇 |
物理学 | 4285篇 |
出版年
2022年 | 118篇 |
2021年 | 145篇 |
2020年 | 210篇 |
2019年 | 157篇 |
2018年 | 149篇 |
2017年 | 116篇 |
2016年 | 273篇 |
2015年 | 283篇 |
2014年 | 316篇 |
2013年 | 639篇 |
2012年 | 685篇 |
2011年 | 875篇 |
2010年 | 493篇 |
2009年 | 409篇 |
2008年 | 710篇 |
2007年 | 760篇 |
2006年 | 754篇 |
2005年 | 768篇 |
2004年 | 633篇 |
2003年 | 501篇 |
2002年 | 458篇 |
2001年 | 426篇 |
2000年 | 390篇 |
1999年 | 231篇 |
1998年 | 208篇 |
1997年 | 204篇 |
1996年 | 266篇 |
1995年 | 250篇 |
1994年 | 222篇 |
1993年 | 257篇 |
1992年 | 246篇 |
1991年 | 221篇 |
1990年 | 183篇 |
1989年 | 183篇 |
1988年 | 210篇 |
1987年 | 190篇 |
1986年 | 148篇 |
1985年 | 201篇 |
1984年 | 189篇 |
1983年 | 138篇 |
1982年 | 181篇 |
1981年 | 156篇 |
1980年 | 154篇 |
1979年 | 155篇 |
1978年 | 158篇 |
1977年 | 120篇 |
1976年 | 136篇 |
1975年 | 102篇 |
1974年 | 119篇 |
1973年 | 97篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Hans van den Berg Michel Mandjes Rudesindo Núñez-Queija 《Operations Research Letters》2007,35(3):297-307
We study a processor-sharing model in which users choose between a high- and a low-priority service, based on their utility functions and prices charged by the service provider. The latter aims at revenue maximization. The model is motivated by file transmissions in data networks with distributed congestion control. 相似文献
102.
103.
104.
E. Maria Claesson Nilesh C. Mehendale Robertus J.M. Klein Gebbink Gerard van Koten Albert P. Philipse 《Journal of magnetism and magnetic materials》2007
Monodisperse magnetizable colloidal silica particles in a stable dispersion have been functionalized with a homogeneous catalyst: a PCP–pincer Pd-complex. In a proof-of-principle experiment we demonstrate the catalytic activity of the colloids in a C–C bond formation reaction. Advantages of the magnetic silica carriers are the large surface-to-volume ratio and the easy recovery by magnetic separation. After magnetic separation, the catalyst-loaded particles are readily redispersed for further use. 相似文献
105.
Long-Mei Zeng Xiong Fu Jing-Yu Su Florecita De Guzman J. Francis Schmitz M. Bilayet Hossain Dick van Der Helm 《中国化学》1991,9(2):136-143
Three pyrrololactam alkaloids have been isolated from the marine sponge Phacellia fusca Schmidt collected from the South China Sea, and their structures were determined as 1–3 , on the grounds of spectral data. This is the first report of these compounds from this sponge. The structure of 1 was confirmed by X-ray analysis. 相似文献
106.
Martin van Gemmeren 《Transactions of the American Mathematical Society》1996,348(6):2413-2426
In the first part we prove an extension of the Chern-Lashof inequality for noncompact immersed manifolds with finitely many ends. For this we give a lower bound of the total absolute curvature in terms of topological invariants of the manifold. In the second part we discuss tightness properties for such immersions. Finally, we give an upper bound for the substantial codimension.
107.
108.
109.
110.
Tim R. Dargaville Julie M. Elliott Mathew Celina 《Journal of Polymer Science.Polymer Physics》2006,44(22):3253-3264
Films of piezoelectric PVDF and P(VDF‐TrFE) were exposed to vacuum UV (115–300 nm VUV) and γ‐radiation to investigate how these two forms of radiation affect the chemical, morphological, and piezoelectric properties of the polymers. The extent of crosslinking was almost identical in both polymers after γ‐irradiation, but surprisingly, was significantly higher for the TrFE copolymer after VUV‐irradiation. Changes in the melting behavior were also more significant in the TrFE copolymer after VUV‐irradiation due to both surface and bulk crosslinking, compared with only surface crosslinking for the PVDF films. The piezoelectric properties (measured using d33 piezoelectric coefficients and D‐E hysteresis loops) were unchanged in the PVDF homopolymer, while the TrFE copolymer exhibited more narrow D‐E loops after exposure to either γ‐ or VUV‐radiation. The more severe damage to the TrFE copolymer in comparison with the PVDF homopolymer after VUV‐irradiation is explained by different energy deposition characteristics. The short wavelength, highly energetic photons are undoubtedly absorbed in the surface layers of both polymers, and we propose that while the longer wavelength components of the VUV‐radiation are absorbed by the bulk of the TrFE copolymer causing crosslinking, they are transmitted harmlessly in the PVDF homopolymer. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3253–3264, 2006 相似文献