全文获取类型
收费全文 | 1356篇 |
免费 | 34篇 |
国内免费 | 1篇 |
专业分类
化学 | 937篇 |
晶体学 | 4篇 |
力学 | 20篇 |
数学 | 207篇 |
物理学 | 223篇 |
出版年
2022年 | 10篇 |
2021年 | 9篇 |
2020年 | 9篇 |
2019年 | 16篇 |
2016年 | 24篇 |
2015年 | 26篇 |
2014年 | 29篇 |
2013年 | 46篇 |
2012年 | 65篇 |
2011年 | 61篇 |
2010年 | 34篇 |
2009年 | 33篇 |
2008年 | 68篇 |
2007年 | 62篇 |
2006年 | 62篇 |
2005年 | 51篇 |
2004年 | 73篇 |
2003年 | 56篇 |
2002年 | 43篇 |
2001年 | 13篇 |
2000年 | 25篇 |
1999年 | 21篇 |
1998年 | 18篇 |
1997年 | 24篇 |
1996年 | 36篇 |
1995年 | 34篇 |
1994年 | 22篇 |
1993年 | 30篇 |
1992年 | 21篇 |
1991年 | 26篇 |
1989年 | 14篇 |
1988年 | 15篇 |
1987年 | 29篇 |
1986年 | 15篇 |
1985年 | 17篇 |
1984年 | 14篇 |
1983年 | 13篇 |
1982年 | 22篇 |
1981年 | 8篇 |
1980年 | 13篇 |
1979年 | 19篇 |
1978年 | 12篇 |
1977年 | 13篇 |
1976年 | 8篇 |
1975年 | 14篇 |
1974年 | 9篇 |
1973年 | 17篇 |
1972年 | 12篇 |
1971年 | 9篇 |
1968年 | 9篇 |
排序方式: 共有1391条查询结果,搜索用时 296 毫秒
21.
Terrence G. Vargo Daniel J. Hook Joseph A. Gardella Mary A. Eberhardt Anne E. Meyer Robert E. Baier 《Journal of polymer science. Part A, Polymer chemistry》1991,29(4):535-545
Recent work in our laboratories has fully characterized the surface region of a segmented poly(ether-urethane) (PEU) extending from the air/polymer interfacial region through bulk depths in the micron range. This characterization utilized energy and angle dependent Electron Spectroscopy for Chemical Analysis (ESCA), Attenuated Total Reflectance–Fourier Transform Infrared Spectroscopy (ATR–FTIR), and Comprehensive Wettability Profiling (contact angle using a homologous series of liquids) as defined by Zisman. In this study this same multi-analytical-technique approach is used to elucidate changes in these PEU surfaces induced through an H2O Radio Frequency Glow Discharge (RFGD) plasma. This investigation reports both qualitative and quantitative changes due to the modification treatments as well as the permanency of the changes effected on these surfaces through the plasma treatment. From our analyses, the amount of surface residing polyurethane (hard segment) is observed to increase due to a proposed plasma etching mechanism. Further, the addition of oxygen containing functionality is detected at the modified surfaces unique with respect to the unmodified PEU. These surface modifications which show large increases in wettability, are finally observed to be semi-permanent over a time period of 6 months. 相似文献
22.
Cyclic sulphurylphosphazochloride (I: formula see ?Inhaltsübersicht”?) reacts with ammonia or methylamine forming the. tetramide(II) and (III), respectively, and with aniline or dimethylamine forming the diamide (IV) resp. (V). The synthesis of the diphenyl derivative (VI) is achieved starting from C6H5? PCl4. (II) gives with PCl5 the ionic compound (VII). 相似文献
23.
Platinum(II) and palladium(II) complexes of the potentially hexadentate P,N-donor ligand family Ar2P-X-PAr2 (X = (CH2)2 [dmape], cyclic-C5H8 [dmapcp]; Ar = o-N,N-dimethylanilinyl) are described. In CH2Cl2, the dmape complexes exist as equilibrium mixtures of MCl2(P,P'-dmape) and [MCl(P,P',N-dmape)]Cl isomers (M = Pd, Pt), governed by deltaH(o) = -19 +/- 4 kJ mol(-1) and deltaS(o) = -100 +/- 30 J mol(-1) K(-1) for M = Pt, and deltaH(o) = -11 +/- 7 kJ mol(-1) and deltaS(o) = -60 +/- 20 J mol(-1) K(-1) for M = Pd. The water-soluble dmapcp complexes exist solely in the [MCl(P,P',N-dmapcp)]Cl form, but the free and coordinated anilinyl rings in these complexes are in slow diastereoselective exchange. X-ray crystal structures for MCl2(P,P'-dmape) (M = Pd, Pt), and the [PdCl(P,P',N-dmape)]+ and [PtCl(P,P',N-dmapcp)]+ cations, are presented. Some of the complexes show marginal activity in water for the catalyzed hydration of maleic to malic acid, giving about 6-7% conversion in 24 h at 100 degrees C and substrate:catalyst loadings of 100:1. Attempts to synthesize a PdCl(P,P',N-dmapm)+ species led instead to isolation of [Pd(mu-Cl)(P,P'-dmapm)]2[PF6]2 (dmapm = Ar2PCH2Ar2). 相似文献
24.
25.
26.
There is a new method of constructing generalized quadrangles (GQs) given by S. Löwe, which is based on covering of nets; all GQs with a regular point can be represented in this way. Here we give a method of constructing GQs with a regular point using the so-called content functions on nets. In the last part of the paper we lay the foundations for a research project aiming to use the more general notion of content to classify GQs and maybe to construct new ones.Both authors acknowledge the financial support by CRUI and DAAD in the frame of Programma Vigoni, which made this work possible. 相似文献
27.
28.
29.
30.