全文获取类型
收费全文 | 3597篇 |
免费 | 235篇 |
国内免费 | 10篇 |
专业分类
化学 | 2308篇 |
晶体学 | 6篇 |
力学 | 117篇 |
数学 | 603篇 |
物理学 | 571篇 |
无线电 | 237篇 |
出版年
2023年 | 51篇 |
2022年 | 61篇 |
2021年 | 92篇 |
2020年 | 81篇 |
2019年 | 108篇 |
2018年 | 80篇 |
2017年 | 57篇 |
2016年 | 154篇 |
2015年 | 137篇 |
2014年 | 136篇 |
2013年 | 205篇 |
2012年 | 327篇 |
2011年 | 349篇 |
2010年 | 190篇 |
2009年 | 170篇 |
2008年 | 264篇 |
2007年 | 244篇 |
2006年 | 221篇 |
2005年 | 188篇 |
2004年 | 169篇 |
2003年 | 119篇 |
2002年 | 101篇 |
2001年 | 45篇 |
2000年 | 44篇 |
1999年 | 28篇 |
1998年 | 18篇 |
1997年 | 18篇 |
1996年 | 9篇 |
1995年 | 10篇 |
1994年 | 12篇 |
1993年 | 9篇 |
1992年 | 7篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 10篇 |
1986年 | 5篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 8篇 |
1980年 | 3篇 |
1979年 | 4篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1975年 | 6篇 |
1974年 | 9篇 |
1929年 | 4篇 |
排序方式: 共有3842条查询结果,搜索用时 453 毫秒
31.
Nicolas Gaillard Alain Guyot Jerome Claverie 《Journal of polymer science. Part A, Polymer chemistry》2003,41(5):684-698
Amphiphilic block copolymers of poly(acrylic acid‐b‐butyl acrylate) were prepared by reversible addition–fragmentation chain transfer polymerization in a one‐pot reaction. These copolymers were characterized by NMR, static and dynamic light scattering, tensiometry, and size exclusion chromatography. The aggregation characteristics of the copolymers corresponded to those theoretically predicted for a star micelle. In a butyl acrylate and methyl methacrylate emulsion polymerization, low amounts of these copolymers could stabilize latices with solid contents up to 50%. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 684–698, 2003 相似文献
32.
A. L'Esprance J. Nicolas D.K. Wilson D.W. Thomson Y. Gabillet G. Daigle 《Applied Acoustics》1993,40(4)
This paper presents a set of acoustical and meteorological data from an outdoor sound propagation experiment. This experiment was done in a farm field near Rock Springs, Pennsylvania, on 7 July 1990. Meteorological and acoustical measurements were recorded simultaneously during six different times in the day. The meteorological measurements permitted determination of the sound speed profiles during each of the measurement sessions, using a method based on surface-layer similarity scaling. The acoustical measurements allowed precise determination of the relative sound pressure levels for a frequency range up to 3150 Hz at six different distances (66, 88, 125, 175, 250 and 350 m). The results show atmospheric conditions have an important effect on sound propagation. At medium and high frequencies, variations of the relative SPL have been measured at distances as short as 62 m. These effects increased with the distances so that variations as great as 30 dB have been measured during that day. Comparisons with the fast field program predictions are also presented, and amply demonstrate the accuracies of this model, especially for the downward refraction cases. 相似文献
33.
34.
Nicolas Bergeron 《Comptes Rendus Mathematique》2002,334(5):395-400
Following the ideas of [2,3], we describe an explicit construction of the dual harmonic form to a quasi-Fuchsian surface in a hyperbolic 3-manifold. To cite this article: N. Bergeron, C. R. Acad. Sci. Paris, Ser. I 334 (2002) 395–400. 相似文献
35.
36.
Parasteh Pirasteh Ali Soltani Lazhar Haji Nicolas Errien 《Applied Surface Science》2006,253(4):1999-2002
In order to understand the optical loss mechanisms in porous silicon based waveguides, structural and optical studies have been performed. Scanning and transmission electron microscopic observations of porous silicon layers are obtained before and after an oxidation process at high temperature in wet O2. Pore size and shape of heavily p-type doped Si wafers are estimated and correlated to the optical properties of the material before and after oxidation. The refractive index was measured and compared to that determined by the Bruggeman model. 相似文献
37.
Nicolas Bouleau 《Journal of Functional Analysis》2007,251(1):325-345
The error on a real quantity Y due to the graduation of the measuring instrument may be asymptotically represented, when the graduation is regular and fines down, by a Dirichlet form on R whose square field operator does not depend on the probability law of Y as soon as this law possesses a continuous density. This feature is related to the “arbitrary functions principle” (Poincaré, Hopf). We give extensions of this property to Rd and to the Wiener space for some approximations of the Brownian motion. This gives new approximations of the Ornstein-Uhlenbeck gradient. These results apply to the discretization of some stochastic differential equations encountered in mechanics. 相似文献
38.
Peter Friz Nicolas Victoir 《Annales de l'Institut Henri Poincaré (B) Probabilités et Statistiques》2007,43(6):775-785
We study large deviation principles for Gaussian processes lifted to the free nilpotent group of step N. We apply this to a large class of Gaussian processes lifted to geometric rough paths. A large deviation principle for enhanced (fractional) Brownian motion, in Hölder- or modulus topology, appears as special case. 相似文献
39.
A highly flexible method for direct and quantitative determination of surface Br?nsted acidity of solids in terms of number, type and strength of the acid sites based on quantitative H/D exchange kinetics between the acid solid and gaseous D2O has been developed and applied to materials covering the whole range of acidity. 相似文献
40.
Nicolas Le Calvez 《中国化学会会志》2002,49(4):585-592
The aim of this study was to develop an analytical method to determine the organochlorine concentrations in sediments. Combination of Microwave assisted Solvent Extraction (MASE) and capillary gas chromatography with specific detection (electron capture detector) was a viable approach for the determination of pesticides in solid matrixes. In this study, MASE development was focused on the selection of a suitable extraction solvent for all the target analytes. MASE procedure was validated by comparison with conventional methods such as Soxhlet and sonication extraction. The proposed method was then applied to determine the organochlorine insecticides concentrations in samples from Authie Bay (France). Environmental water samples were analysed and five target analytes were detected in concentrations from 0.03 to 0.56 ng/g of dry sediment. These investigations showed the accumulation and the persistency of these products in sediments in spite of the fact they were banned a few decades ago. 相似文献