全文获取类型
收费全文 | 20143篇 |
免费 | 538篇 |
国内免费 | 145篇 |
专业分类
化学 | 13905篇 |
晶体学 | 161篇 |
力学 | 653篇 |
数学 | 2867篇 |
物理学 | 3240篇 |
出版年
2022年 | 104篇 |
2021年 | 173篇 |
2020年 | 266篇 |
2019年 | 230篇 |
2018年 | 209篇 |
2017年 | 167篇 |
2016年 | 355篇 |
2015年 | 326篇 |
2014年 | 377篇 |
2013年 | 945篇 |
2012年 | 914篇 |
2011年 | 1265篇 |
2010年 | 574篇 |
2009年 | 518篇 |
2008年 | 1075篇 |
2007年 | 1120篇 |
2006年 | 1134篇 |
2005年 | 1066篇 |
2004年 | 988篇 |
2003年 | 861篇 |
2002年 | 821篇 |
2001年 | 317篇 |
2000年 | 265篇 |
1999年 | 216篇 |
1998年 | 241篇 |
1997年 | 237篇 |
1996年 | 287篇 |
1995年 | 219篇 |
1994年 | 226篇 |
1993年 | 192篇 |
1992年 | 202篇 |
1991年 | 203篇 |
1990年 | 166篇 |
1989年 | 143篇 |
1988年 | 172篇 |
1987年 | 174篇 |
1986年 | 145篇 |
1985年 | 282篇 |
1984年 | 278篇 |
1983年 | 222篇 |
1982年 | 296篇 |
1981年 | 271篇 |
1980年 | 273篇 |
1979年 | 247篇 |
1978年 | 244篇 |
1977年 | 225篇 |
1976年 | 206篇 |
1975年 | 184篇 |
1974年 | 202篇 |
1973年 | 183篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
James E. Keesling Yuli B. Rudyak 《Proceedings of the American Mathematical Society》2007,135(8):2629-2631
We discuss which groups can be realized as the fundamental groups of compact Hausdorff spaces. In particular, we prove that the claim ``every group can be realized as the fundamental group of a compact Hausdorff space' is consistent with the Zermelo-Fraenkel-Choice set theory.
122.
Kelly A. Burke Sona Sivakova Blayne M. McKenzie Patrick T. Mather Stuart J. Rowan 《Journal of polymer science. Part A, Polymer chemistry》2006,44(17):5049-5059
We report herein studies on the liquid crystalline behavior of a series of supramolecular materials that contain different ratios of two complementary symmetrically-substituted alkoxy-bis(phenylethynyl)benzene AA- and BB-type monomers. One monomer has thymine units placed at either end of the rigid mesogenic core, while the other has N6-(4-methoxybenzoyl)-adenine units placed on the ends. Differential scanning calorimetric and polarized optical microscopy studies have been carried out on these systems. These studies show that the material's behavior is strongly dependent on its thermal history. As a result, the materials can exhibit, on heating, either a liquid crystalline phase, a crystalline phase, or the coexistence of crystalline and liquid crystalline regions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5049–5059, 2006 相似文献
123.
Olga Ordeig Craig E Banks Trevor J Davies F Javier del Campo Francesc Xavier Mu?oz Richard G Compton 《Analytical sciences》2006,22(5):679-683
Gold ultra-microelectrode arrays are used to explore the electrochemical oxidation of hydroxide ions and are shown to be analytical useful. Two types of ultra-microelectrode arrays are used; the first consist of 256 individual electrodes of 5 microm in radius, 170 of which are electrochemically active in a cubic arrangement which are separated from their nearest neighbour by a distance of 100 microm. The second array compromises 2597 electrodes of 2.5 microm in radius and of which 1550 of which are electrochemically active in a hexagonal arrangement separated by the nearest neighbour by 55 microm. Well defined voltammetric waves are found with peak currents proportional to the concentration of hydroxide ions in the range 50 microM to 1 mM. Detection limits of 20 microM using the 170 ultra-microelectrode and 10 microM with the 1550 ultra-microelectrode array are shown to be possible but with a higher sensitivity of 4 mA M(-1) observed using the 1550 ultra-microelectrode array compared to 1.2 mA M(-1) with the 170 ultra-microelectrode array. 相似文献
124.
The exterior of a cross-linked polymer gel resembles a polymer brush. Such gel including its brush can be swollen by a good solvent. The detachment of the solvent–vapor (L–V) interface from the brush is controlled by the adsorption of polymer segments onto this interface and is to a very good approximation not influenced by long-range van der Waals contributions. A wetting transition in this system coincided with the adsorption–desorption transition for chains onto such L–V interface and has various unusual features. There are several indications that in practice this system should feature a second-order wetting transition. 相似文献
125.
Demin D. L. Dzhelepov V. P. Filchenkov V. V. Grafov N. N. Grebinnik V. G. Migachev D. V. Konin A. D. Rudenko A. I. Sidorov V. T. Zhestkov Yu. G. Zinov V. G. Davies J. D. Bom V. R. van Eijk C. W. E. 《Hyperfine Interactions》1996,101(1):13-19
The ddµ molecule formation rate is experimentally measured for the two hyperfine states of the dµ-atom in the temperature range of 5–30 K. Results are consistent with a preliminary measurement by the TRIUMF group and contradict theoretical predictions. The work has been performed on the JINR phasotron (Dubna). 相似文献
126.
This paper discusses recent trends in the field of reverse engineering, particularly those highlighted at the Second Working
Conference on Reverse Engineering, held in July 1995. The trends observed include increased orientation toward tasks, grounding
in complex real-world applications, guidance from empirical study, analysis of non-code sources, and increased formalization.
The paper also summarizes open research issues and provides pointers to future events and sources of information in this area. 相似文献
127.
128.
In many metrics of physical interest, the gravitational field can be represented as an optical medium with an effective index of refraction. We show that, in such a metric, the orbits of both massive and massless particles are governed by a variational principle which involves the index of refraction and which assumes the form of Fermat's principle or of Maupertuis's principle. From this variational principle we derive exact equations of motion of Newtonian form which govern both massless and massive particles. These equations of motion are applied to some problems of physical interest. 相似文献
129.
130.
Fluorescence correlation spectroscopy (FCS) measurements have been performed in order to determine the translational diffusion coefficients of three differently charged fluorescent probes (cationic: rhodamine 6G, neutral: 4-dicyanomethylene-2-methyl-6-p-dimethylaminostyryl-4-H-pyran, DCM, and anionic: fluorescein) dissolved within the common room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate, [bmim][PF6]. These experiments demonstrate that FCS is a rapid, sensitive, precise (typical RSD from 4-8%), and low-consumption screening tool for the determination of analyte mobility within microliter ionic liquid samples. 相似文献