全文获取类型
收费全文 | 35041篇 |
免费 | 1149篇 |
国内免费 | 252篇 |
专业分类
化学 | 23916篇 |
晶体学 | 246篇 |
力学 | 827篇 |
数学 | 5767篇 |
物理学 | 5686篇 |
出版年
2022年 | 190篇 |
2021年 | 433篇 |
2020年 | 533篇 |
2019年 | 506篇 |
2018年 | 398篇 |
2017年 | 380篇 |
2016年 | 863篇 |
2015年 | 783篇 |
2014年 | 848篇 |
2013年 | 1825篇 |
2012年 | 1945篇 |
2011年 | 2440篇 |
2010年 | 1202篇 |
2009年 | 1081篇 |
2008年 | 2106篇 |
2007年 | 2104篇 |
2006年 | 2075篇 |
2005年 | 1965篇 |
2004年 | 1652篇 |
2003年 | 1451篇 |
2002年 | 1350篇 |
2001年 | 458篇 |
2000年 | 437篇 |
1999年 | 395篇 |
1998年 | 358篇 |
1997年 | 390篇 |
1996年 | 528篇 |
1995年 | 390篇 |
1994年 | 351篇 |
1993年 | 333篇 |
1992年 | 326篇 |
1991年 | 277篇 |
1990年 | 243篇 |
1989年 | 240篇 |
1988年 | 262篇 |
1987年 | 237篇 |
1986年 | 218篇 |
1985年 | 382篇 |
1984年 | 379篇 |
1983年 | 273篇 |
1982年 | 345篇 |
1981年 | 362篇 |
1980年 | 337篇 |
1979年 | 315篇 |
1978年 | 289篇 |
1977年 | 264篇 |
1976年 | 244篇 |
1975年 | 226篇 |
1974年 | 234篇 |
1973年 | 243篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
F. Klein 《Fresenius' Journal of Analytical Chemistry》1885,24(1):379-388
Ohne ZusammenfassungNieder-Ingelheim, 3. Mai 1885. 相似文献
42.
A time discrete scheme is used to approximate the solution toa phase field system of PenroseFife type with a non-conservedorder parameter. An a posteriori error estimate is presentedthat allows the estimation of the difference between continuousand semidiscrete solutions by quantities that can be calculatedfrom the approximation and given data. 相似文献
43.
David S. McGuinness Edward L. Marshall Vernon C. Gibson Jonathan W. Steed 《Journal of polymer science. Part A, Polymer chemistry》2003,41(23):3798-3803
Hetero‐bimetallic Fe(II) alkoxide/aryloxides were evaluated as initiators for the ring‐opening polymerization of rac‐lactide. [(THF)NaFe(OtBu)3]2 ( 1 ) and [(THF)4Na2Fe(2,6‐diisopropylphenolate)4] ( 2 ) (THF = tetrahydrofuran) both polymerized lactide efficiently at room temperature, with complex 1 affording better control over the molecular weight parameters of the resultant polymer. At conversions below 70%, a linear increase in molecular weight with conversion was observed, indicative of a well‐controlled polymerization process. Complex 2 is the first example of a dianionic Fe(II) alkoxide and has been structurally characterized to reveal a distorted square planar FeO4 array in which both Na counterions bridge two aryloxide ligands and are further complexed by two THF ligands. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3798–3803, 2003 相似文献
44.
We prove some new evaluations for multiple polylogarithms of arbitrary depth. The simplest of our results is a multiple zeta evaluation one order of complexity beyond the well-known Broadhurst–Zagier formula. Other results we provide settle three of the remaining outstanding conjectures of Borwein, Bradley, and Broadhurst. A complete treatment of a certain arbitrary depth class of periodic alternating unit Euler sums is also given. 相似文献
45.
46.
Experiments concerning the properties of soap films have recently been carried out and these systems have been proposed as experimental versions of theoretical two‐dimensional liquids. A silk filament introduced into a flowing soap film, was seen to demonstrate various stable modes, and these were, namely, a mode in which the filament oscillates and one in which the filament is stationary and aligns with the flow of the liquid. The system could be forced from the oscillatory mode into the non‐ oscillatory mode by varying the length of the filament. In this article we use numerical and computational techniques in order to simulate the strongly coupled behaviour of the filament and the fluid. Preliminary results are presented for the specific case in which the filament is seen to oscillate continuously for the duration of our simulation. We also find that the filament oscillations are strongly suppressed when we reduce the effective length of the filament. We believe that these results are reminiscent of the different oscillatory and non‐oscillatory modes observed in experiment. The numerical solutions show that, in contrast to experiment, vortices are created at the leading edge of the filament and are preferentially grown in the curvature of the filament and are eventually released from the trailing edge of the filament. In a similar manner to oscillating hydrofoils, it seems that the oscillating filaments are in a minimal energy state, extracting sufficient energy from the fluid to oscillate. In comparing numerical and experimental results it is possible that the soap film does have an effect on the fluid flow especially in the boundary layer where surface tension forces are large. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
47.
Bou-Huot Phe Véronique Bounor-Legare Laurent David Alain Michel 《Journal of Sol-Gel Science and Technology》2004,31(1-3):47-50
We study the synthesis of organic-inorganic hybrids in the molten state of the polymer without solvent, by reactive processing. The synthesis is based in a first step upon the crosslinking of ethylene vinyl acetate copolymer (EVA) through an exchange reaction between the pendant ester groups of EVA and tetrapropoxysilane (TPOS) in presence of dibutyltin oxide (DBTO) as an indispensable catalyst. Then in a second step the hydrolysis-condensation reactions of residual alkoxide groups results in silica network formation, which is covalently bonded with the organic network. An original approach was developed to correlate the evolution of the hydrolysis-condensation reactions through the assessment of propanol by gas chromatography and the evolution of the morphology through SAXS and TEM analysis. Silica-rich domains with a diameter close to 5 nm are obtained. 相似文献
48.
49.
50.
This note chronicles various roles played by the Yasuda-Shimada theorem in some recent developments of Riemann--Finsler geometry. We shall demonstrate that the said theorem is, at various stages of its life, an enigma, an inspiration, a flawed icon, and a powerful catalyst. 相似文献