全文获取类型
收费全文 | 456篇 |
免费 | 26篇 |
专业分类
化学 | 318篇 |
晶体学 | 2篇 |
力学 | 4篇 |
数学 | 44篇 |
物理学 | 114篇 |
出版年
2023年 | 5篇 |
2022年 | 10篇 |
2021年 | 13篇 |
2020年 | 16篇 |
2019年 | 15篇 |
2018年 | 9篇 |
2017年 | 7篇 |
2016年 | 8篇 |
2015年 | 13篇 |
2014年 | 25篇 |
2013年 | 18篇 |
2012年 | 25篇 |
2011年 | 33篇 |
2010年 | 17篇 |
2009年 | 16篇 |
2008年 | 25篇 |
2007年 | 23篇 |
2006年 | 32篇 |
2005年 | 23篇 |
2004年 | 13篇 |
2003年 | 12篇 |
2002年 | 21篇 |
2001年 | 13篇 |
2000年 | 2篇 |
1999年 | 7篇 |
1998年 | 6篇 |
1997年 | 4篇 |
1996年 | 5篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 6篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 13篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1974年 | 1篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1897年 | 1篇 |
1894年 | 1篇 |
1891年 | 1篇 |
排序方式: 共有482条查询结果,搜索用时 31 毫秒
51.
Phan-Xuan T Durand D Nicolai T Donato L Schmitt C Bovetto L 《Langmuir : the ACS journal of surfaces and colloids》2011,27(24):15092-15101
Stable suspensions of protein microgels are formed by heating salt-free β-lactoglobulin solutions at concentrations up to about C = 50 g·L(-1) if the pH is set within a narrow range between 5.75 and 6.1. The internal protein concentration of these spherical particles is about 150 g·L(-1) and the average hydrodynamic radius decreases with increasing pH from 200 to 75 nm. The formation of the microgels leads to an increase of the pH, which is a necessary condition to obtain stable suspensions. The spontaneous increase of the pH during microgel formation leads to an increase of their surface charge density and inhibits secondary aggregation. This self-stabilization mechanism is not sufficient if the initial pH is below 5.75 in which case secondary aggregation leads to precipitation. Microgels are no longer formed above a critical initial pH, but instead short, curved protein strands are obtained with a hydrodynamic radius of about 15-20 nm. 相似文献
52.
Larsen TR Bache N Gramsbergen JB Roepstorff P 《Journal of the American Society for Mass Spectrometry》2011,22(6):989-996
Protein nitration take place on tyrosine residues under oxidative stress conditions and may influence a number of processes
including enzyme activity, protein-protein interactions and phospho-tyrosine signalling pathways. Nitrated proteins have been
identified in a number of diseases, however, the study of these proteins has been compromised by the lack of good methods
for identifying nitrated proteins, their nitration sites and the level of nitration. Here, we present a method for identification
of nitrated peptides that allows the site specific assignment of nitration, is easy to use and reproducible, and opens up
for the possibility to quantify the level of nitration of specific peptides as function of different oxidative conditions,
namely combined fractional diagonal chromatography (COFRADIC) in combination with off-line nano-LC-MALDI. We identify six
nitrated peptides from in vitro nitrated bovine serum albumin and propose that automated COFRADIC using nano-LC and off-line MALDI-MS might be a possibility
for identification of tyrosine nitrated proteins and the nitration sites in complex samples. 相似文献
53.
Türkoglu G Heinemann FW Burzlaff N 《Dalton transactions (Cambridge, England : 2003)》2011,40(17):4678-4686
The new N,N,O ligand 2,2-bis(3,5-dimethylpyrazol-1-yl)propionic acid (2,2-Hbdmpzp) (2) and its transition metal complexes [Mn(2,2-bdmpzp)(CO)(3)] (3), [Re(2,2-bdmpzp)(CO)(3)] (4), [Cu(2,2-bdmpzp)(2)] (5), and [Ru(2,2-bdmpzp)Cl(L)(PPh(3))] [L = PPh(3) (6), N(2) (7), CO (8a/b), SO(2) (9a/b)] have been synthesized, characterized and compared to analogous complexes bearing a bis(3,5-dimethylpyrazol-1-yl)acetic acid. It was found that the additional methyl group has a remarkable influence on the stability and reactivity of transition metal complexes. 相似文献
54.
Godau T Bleifuss SM Müller AL Roth T Hoffmann S Heinemann FW Burzlaff N 《Dalton transactions (Cambridge, England : 2003)》2011,40(24):6547-6554
One-pot syntheses of three new enantiopure heteroscorpionate ligands derived from (+)-camphor or (-)-menthone are described. The ligands are obtained by reacting pyrazoles derived from (+)-camphor or (-)-menthone with sodium hydride and thionyl chloride. Subsequent reactions with pyridine and various aldehydes afford the tripod ligands in multi-gram amounts. Especially the menthopyrazole based ligand 6 showed encouraging ee values up to 69% in the Cu(I) catalysed enantioselective cyclopropanation of styrene with ethyl diazoacetate. 相似文献
55.
The unique catalytic activity of vanadium nitrogenase suggests a new direction for the direct production of biofuels from CO with either synthetic catalysts or nitrogenase-containing bacteria. The reduction of CO by V?nitrogenase to light hydrocarbons shows striking similarities to the established Fischer-Tropsch process; however, the enzyme does not use H(2) directly for this reaction. ADP=adenosine diphosphate, ATP= adenosine triphosphate. 相似文献
56.
57.
An attempt is made to understand the root spaces of Kac Moody algebras of hyperbolic type, and in particularE
10, in terms of a DDF construction appropriate to a subcritical compactified bosonic string. While the level-one root spaces can be completely characterized in terms of transversal DDF states (the level-zero elements just span the affine subalgebra), longitudinal DDF states are shown to appear beyond level one. In contrast to previous treatments of such algebras, we find it necessary to make use of a rational extension of the self-dual root lattice as an auxiliary device, and to admit non-summable operators (in the sense of the vertex algebra formalism). We demonstrate the utility of the method by completely analyzing a non-trivial level-two root space, obtaining an explicit and comparatively simple representation for it. We also emphasize the occurrence of several Virasoro algebras, whose interrelation is expected to be crucial for a better understanding of the complete structure of the Kac Moody algebra.Supported by Konrad-Adenauer-Stiftung e.V.This article was processed by the author using the Latex style filepljour1 from Springer-Verlag. 相似文献
58.
59.
Stanislaw Ciechanowicz Nicolai Popov 《Zeitschrift fur Physik C Particles and Fields》1993,57(4):623-629
Multipole expansion of the partial transition amplitude in the nuclear muon capture with massive lefthanded Dirac neutrino has been derived. The multipole amplitudes for the partial nuclear transitions are given as the explicit functions of the neutrino mass parameter. As an example, the capture rate, the recoil asymmetry and the neutrino polarization are investigated in terms of these multipole amplitudes. The transversal neutrino polarization provides a connection between theT-violation and the neutrino mass: ifT-odd component in the neutrino polarization is observed, then neutrino must be a massive particle. It turns out that in the capture rate and recoil polarization, the effects due to very small neutrino mass can be proportional to the square ratio of the neutrino mass to its momentum, while the neutrino transversal polarization is proportional to this ratio only. Under the recent limits on the muon neutrino mass, the observable effects inthe partial transition may be below the order of ?10?3. 相似文献
60.
After integration over the fermions in an SU(2) lattice gauge theory, the effective fermionic action may be expressed as a sum over all possible closed gauge field loops with corresponding weight factors. We approximate this sum and perform a Monte Carlo simulation of a coupled fermion-gauge system on a 44 lattice. We compare our results for 〈Seff〉 and for different values of the gauge field coupling β and fermion coupling κ with the free fermion theory on a lattice. 〈Seff〉 turns out to be quite small for . 相似文献