全文获取类型
收费全文 | 1365篇 |
免费 | 30篇 |
国内免费 | 4篇 |
专业分类
化学 | 870篇 |
晶体学 | 9篇 |
力学 | 47篇 |
数学 | 123篇 |
物理学 | 350篇 |
出版年
2022年 | 11篇 |
2021年 | 14篇 |
2020年 | 14篇 |
2019年 | 26篇 |
2018年 | 12篇 |
2016年 | 26篇 |
2015年 | 21篇 |
2014年 | 30篇 |
2013年 | 34篇 |
2012年 | 64篇 |
2011年 | 65篇 |
2010年 | 26篇 |
2009年 | 35篇 |
2008年 | 65篇 |
2007年 | 48篇 |
2006年 | 70篇 |
2005年 | 51篇 |
2004年 | 42篇 |
2003年 | 39篇 |
2002年 | 37篇 |
2001年 | 29篇 |
2000年 | 28篇 |
1999年 | 16篇 |
1998年 | 15篇 |
1997年 | 13篇 |
1996年 | 21篇 |
1995年 | 23篇 |
1994年 | 14篇 |
1993年 | 20篇 |
1992年 | 34篇 |
1991年 | 21篇 |
1990年 | 19篇 |
1989年 | 26篇 |
1988年 | 10篇 |
1987年 | 21篇 |
1986年 | 19篇 |
1985年 | 22篇 |
1984年 | 33篇 |
1983年 | 22篇 |
1982年 | 20篇 |
1981年 | 26篇 |
1980年 | 18篇 |
1979年 | 17篇 |
1978年 | 20篇 |
1977年 | 19篇 |
1976年 | 9篇 |
1975年 | 23篇 |
1974年 | 12篇 |
1973年 | 17篇 |
1968年 | 7篇 |
排序方式: 共有1399条查询结果,搜索用时 62 毫秒
91.
92.
S.G. Parker 《Solid State Communications》1979,31(6):403-408
Factors which influence coercivity, Hc, in (Y,Sm,Lu,Ca)3(FeGe)5O12 films and in (Y,Sm,Tm)3(FeGa)5O12 films grown by LPE have been identified. An anomalous layer at the film-substrate interface exhibits coercivity values different from that of the middle, bulk, portion of the film. The contribution of the transient layer at the substrate interface could be reduced by increasing the rotation rate while immersing the substrate into the melt. Films containing Ga show lower coercivities than films containing CaGe possibly because films with Ga are more uniform in composition. Films with Ga show increased coercivities with increasing growth rates and with increasing Sm content throughout the film. 相似文献
93.
J.C. Selover Marianne Marsi David W. Parker J.A. Gladysz 《Journal of organometallic chemistry》1981,206(3):317-329
A series of kinetically unstable mononuclear anionic formyl complexes have been prepared by the action of Li(C2H5)3BH on neutral metal carbonyl precursors. One of these, Li+[(CO)4Mn(COC6H5)(CHO)]?, is shown to decompose by a hydride transfer disproportionation mechanism involving the by-product (C2H5)3B. 相似文献
94.
Techniques have been developed which permit the direct analysis of optical purity in α-deuterated amines and carboxylic acids. 相似文献
95.
96.
97.
J.L. Osborne C.A. Barnes R.W. Kavanagh R.M. Kremer G.J. Mathews J.L. Zyskind P.D. Parker A.J. Howard 《Nuclear Physics A》1984,419(1):115-132
Cross sections for the 3He(α, γ)7Be reaction have been measured at several energies from Ec.m. = 165 to 1169 keV by counting prompt γ-rays from a windowless, differentially pumped, recirculating, 3He gas target. The cross-section factor S34(Ec.m.) and branching ratio γ1/γ0 were determined at each energy. Cross sections were also measured at Ec.m. = 947 and 1255 keV by counting the γ-rays from the 7Be produced in a 3He gas cell with a Ni entrance foil. Combining the results of these two independent experiments yields a zero-energy intercept for the cross-section factor of S34(0) = 0.53 ± 0.03 keV · b. The relationship between these measurements and several theoretical calculations, and the import of the extrapolated cross section for the solar-neutrino problem are discussed. 相似文献
98.
The analysis of the interaction of threose 4-phosphate and 2-deoxyerythrose 4-phosphate with 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase (DAH7PS) reveals previously unrecognised mechanistic differences between the DAH7PS-catalysed reaction and that catalysed by the closely related enzyme, 3-deoxy-D-manno-octulosonate 8-phosphate synthase (KDO8PS). 相似文献
99.
100.
Parker KJ Taylor LS Gracewski S Rubens DJ 《The Journal of the Acoustical Society of America》2005,117(5):2705-2712
A number of different approaches have been developed to estimate and image the elastic properties of tissue. The biomechanical properties of tissues are vitally linked to function and pathology, but cannot be directly assessed by conventional ultrasound, MRI, CT, or nuclear imaging. Research developments have introduced new approaches, using either MRI or ultrasound to image the tissue response to some stimulus. A wide range of stimuli has been evaluated, including heat, water jets, vibration shear waves, compression, and quasistatic compression, using single or multiple steps or low-frequency (<10 Hz) cyclic excitation. These may seem to be greatly dissimilar, and appear to produce distinctly different types of information and images. However, our purpose in this tutorial is to review the major classes of excitation stimuli, and then to demonstrate that they produce responses that fall within a common spectrum of elastic behavior. Within this spectrum, the major classes of excitation include step compression, cyclic quasistatic compression, harmonic shear wave excitation, and transient shear wave excitation. The information they reveal about the unknown elastic distribution within an imaging region of interest are shown to be fundamentally related because the tissue responses are governed by the same equation. Examples use simple geometry to emphasize the common nature of the approaches. 相似文献