全文获取类型
收费全文 | 1658篇 |
免费 | 20篇 |
国内免费 | 22篇 |
专业分类
化学 | 1074篇 |
晶体学 | 15篇 |
力学 | 51篇 |
数学 | 311篇 |
物理学 | 249篇 |
出版年
2022年 | 17篇 |
2021年 | 23篇 |
2020年 | 15篇 |
2019年 | 19篇 |
2018年 | 19篇 |
2017年 | 21篇 |
2016年 | 38篇 |
2015年 | 20篇 |
2014年 | 44篇 |
2013年 | 80篇 |
2012年 | 80篇 |
2011年 | 76篇 |
2010年 | 59篇 |
2009年 | 68篇 |
2008年 | 87篇 |
2007年 | 111篇 |
2006年 | 102篇 |
2005年 | 87篇 |
2004年 | 78篇 |
2003年 | 59篇 |
2002年 | 48篇 |
2001年 | 33篇 |
2000年 | 23篇 |
1999年 | 20篇 |
1998年 | 20篇 |
1997年 | 22篇 |
1996年 | 33篇 |
1995年 | 24篇 |
1994年 | 22篇 |
1993年 | 23篇 |
1992年 | 19篇 |
1991年 | 16篇 |
1990年 | 21篇 |
1989年 | 15篇 |
1988年 | 17篇 |
1987年 | 14篇 |
1986年 | 15篇 |
1985年 | 23篇 |
1984年 | 19篇 |
1983年 | 13篇 |
1982年 | 24篇 |
1981年 | 12篇 |
1980年 | 15篇 |
1979年 | 8篇 |
1978年 | 13篇 |
1977年 | 18篇 |
1976年 | 10篇 |
1975年 | 6篇 |
1974年 | 8篇 |
1965年 | 8篇 |
排序方式: 共有1700条查询结果,搜索用时 0 毫秒
91.
Omar R. Musaev Eli A. Sutter Jerzy M. Wrobel Michael B. Kruger 《Journal of nanoparticle research》2012,14(2):654-6
A eutectic AuGe target immersed in distilled water was ablated by pulsed ultraviolet laser light. The structure of the ablated
material was investigated by high-resolution transmission electron microscopy (HRTEM). The images show formation of nanowire
structures of AuGe up to 100 nm in length, with widths of 5–10 nm. These nanostructures have Ge content significantly lower
than the target material. Electron diffraction demonstrates that they crystallize in the α-AuGe structure. For comparison,
laser ablation of pure Au and pure Ge targets was also performed under the same conditions. HRTEM shows that Ge forms spherical
nanoparticles with a characteristic size of ~30 nm. Au forms spherical nanoparticles with diameters of ~10 nm. Similar to
AuGe, it also forms chainlike structures with substantially lower aspect ratio. 相似文献
92.
We study local convergence of quasi-Newton methods for solving systems of nonlinear equations defined by B-differentiable functions. We extend the classical linear and superlinear convergence results for general quasi-Newton methods as well as for Broyden's method. We also show how Broyden's method may be applied to nonlinear complementarity problems and illustrate its computational performance on two small examples. 相似文献
93.
One of the alcohols derived from rearrangement of humulene-4,5-epoxide has been converted into a keto-alcohol, the angelate ester of which is a naturally-occurring sesquiterpenoid. 相似文献
94.
Jerzy Kowalski-Glikman 《Physics letters. [Part B]》1984,139(3):159-160
We find a ground state of D = 10, N = 1 supergravity of the form (AdS(3) × R1) × S3 × T3 which preserves all supersymmetries and should provide a gauged D = 4, N = 4 supergravity coupled to supermatter after dimensional reduction. 相似文献
95.
96.
97.
Reaction of tosylhydrazones of O-substituted alpha-hydroxy or N-substituted alpha-amino aldehydes (2, 7, 11, 15, 17, and 20) with selected alpha-magnesio alkyl phenyl sulfones afforded the respective derivatives of allylic alcohols or allylic amines. 2,3-O-Isopropylidene-D-glyceraldehyde (1) was transformed into its tosylhydrazone (2) and then olefins 4a with retention of optical purity. 相似文献
98.
Dutka M Gurbiel RJ Kozioł J Froncisz W 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2004,170(2):5786-227
Applicability of continuous wave multiquantum EPR methods to study relaxation times at X-band is examined. Multiquantum transitions excited in a two-level system by tetrachromatic irradiation are used for these studies. The Bloch equation model is applied to simulate lineshapes of the three quantum transitions as a function of frequency difference between exciting fields. The dependence of multiquantum transition signals on relaxation times and microwave amplitude is shown. On this basis a method of deducing relaxation times from these signals is formulated. The case of a homogeneously and inhomogeneously broadened resonance line is considered. Two experimental methods are used to verify the proposed hypothesis: the X-band continuous wave multiquantum EPR with four frequencies microwave field and saturation recovery EPR. The values of T1 obtained from CW MQ EPR and SR EPR are compared. 相似文献
99.
Despite being size-extensive, the "second-generation" 1-matrix functionals for the electron-electron repulsion energy V(ee) yield vanishing correlation energy for the homogeneous electron gas. This failure is directly related to the idempotency condition imposed upon an auxiliary matrix that enters the expression for V(ee). In particular, the recently proposed Kollmar-Hess functional is not volume-extensive and thus is incapable of properly describing any delocalized system at its thermodynamic limit. 相似文献
100.
To enrich the limited set of isonitriles typically employed, 4-isocyano-2,2,6,6-teramethylpiperidin-1-oxyl (1) is proposed as an isonitrile bearing a nitroxyl moiety. Isocyanide 1 was used in some reactions characteristic of isonitriles. Isoselenocyanate, amides (products of Passerini and Ugi reactions), and tetrazole derivative were obtained. The EPR spectra of the urea derivative 5b and a product of an Ugi reaction 7 (both dinitroxides) were analyzed. [structure: see text] 相似文献