全文获取类型
收费全文 | 1136篇 |
免费 | 30篇 |
国内免费 | 11篇 |
专业分类
化学 | 771篇 |
晶体学 | 12篇 |
力学 | 11篇 |
数学 | 73篇 |
物理学 | 310篇 |
出版年
2022年 | 7篇 |
2021年 | 12篇 |
2020年 | 11篇 |
2019年 | 18篇 |
2018年 | 10篇 |
2016年 | 17篇 |
2015年 | 21篇 |
2014年 | 19篇 |
2013年 | 39篇 |
2012年 | 67篇 |
2011年 | 66篇 |
2010年 | 42篇 |
2009年 | 42篇 |
2008年 | 60篇 |
2007年 | 58篇 |
2006年 | 56篇 |
2005年 | 62篇 |
2004年 | 47篇 |
2003年 | 50篇 |
2002年 | 51篇 |
2001年 | 31篇 |
2000年 | 35篇 |
1999年 | 16篇 |
1998年 | 18篇 |
1997年 | 10篇 |
1996年 | 15篇 |
1995年 | 15篇 |
1994年 | 24篇 |
1993年 | 8篇 |
1992年 | 11篇 |
1991年 | 6篇 |
1990年 | 7篇 |
1989年 | 14篇 |
1988年 | 12篇 |
1987年 | 11篇 |
1986年 | 8篇 |
1985年 | 20篇 |
1984年 | 6篇 |
1983年 | 12篇 |
1982年 | 8篇 |
1981年 | 12篇 |
1980年 | 6篇 |
1979年 | 12篇 |
1978年 | 9篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1975年 | 9篇 |
1974年 | 7篇 |
1973年 | 9篇 |
1972年 | 13篇 |
排序方式: 共有1177条查询结果,搜索用时 15 毫秒
91.
92.
Giles GI Fry FH Tasker KM Holme AL Peers C Green KN Klotz LO Sies H Jacob C 《Organic & biomolecular chemistry》2003,1(23):4317-4322
Oxidative stress is implicated, either directly or indirectly, in the pathology of a range of human diseases. As a consequence, the development of efficient antioxidants for medical use has become increasingly important. We have synthesised a range of structurally related organo-sulfur, -selenium and -tellurium agents and demonstrated that a combination of electrochemical methodology, in vitro assays and cell culture tests can be used to rationalise the antioxidant activity of these catalytic agents. Based on its exceptionally low anodic oxidation potential (Epa) and high activity against the representative oxidative stressors tert-butyl hydroperoxide and peroxynitrite, 4,4'-dihydroxydiphenyltelluride is predicted to be a potent antioxidant. This compound exhibits a correspondingly high activity with a remarkably low IC50 value of 20 nM, when tested in PC12 cell culture using a bioassay indicative of the early stages of Alzheimer's disease. 相似文献
93.
Wilson AJ Groves K Jain RK Park HS Hamilton AD 《Journal of the American Chemical Society》2003,125(15):4420-4421
Using circular dichroism, UV-vis, and trypsin proteolysis, we have shown how a metalloporphyrin dimer induces the unfolding of a protein, cytochrome c, under physiologically relevant conditions and accelerates its rate of proteolytic degradation. 相似文献
94.
McGuinness DS Wasserscheid P Keim W Morgan D Dixon JT Bollmann A Maumela H Hess F Englert U 《Journal of the American Chemical Society》2003,125(18):5272-5273
Cr(III) complexes of tridentate SNS ligands have been prepared and evaluated as catalysts for ethylene trimerization, with several giving very high activity and excellent selectivity toward 1-hexene when activated with methylaluminoxane. The new complexes illustrate the potential of sulfur-based ligands on early transition metals for catalysis. 相似文献
95.
[reaction: see text] Mellitic triimides undergo three sequential one-electron reduction processes whose potentials are significantly lowered in the presence of alkyl thioureas. The two sequential reductions of benzene diimides are similarly stabilized. Calculation of the relative free energy change between the different electronic states of the imide acceptors and their corresponding alkyl thiourea complexes indicates dramatic increases in hydrogen bond strength with increasing acceptor charge density. 相似文献
96.
A mild and high-yielding cyanating reaction of amine, sulfur, and carbanion nucleophiles is reported here using 1-cyanoimidazole as an electrophilic cyanating agent. 相似文献
97.
Hetherington NB Kulak AN Sheard K Meldrum FC 《Langmuir : the ACS journal of surfaces and colloids》2006,22(5):1955-1958
Single crystals of calcite with regular patterned surfaces comprising close-packed arrays of hemispherical cavities or domes were produced by crystallization on colloidal monolayers or PDMS replicas of these monolayers, respectively. Perfect replication of the substrate topography was achieved for all colloidal particles, irrespective of their size and surface chemistry when the substrate geometry permitted unrestricted ion flow to the growing crystal. This work demonstrates that crystallization within a mould provides a very general route to producing single crystals with curved surfaces and unusual morphologies and that such patterning can be applied from the micro- to the nanoscale. 相似文献
98.
Production of bacterial cellulose by Acetobacter xylinum ATCC 10821 and 23770 in static cultures was tested from unamended food process effluents. Effluents in cluded low-solids
(LS) and high-solids (HS) potato effluents, cheese whey permeate (CW), or sugar beet raffinate (CSB). Strain 23770 produced
10% less cellulose from glucose than did strain 10821 and diverted more glucose to gluconate. Unamended HS, CW, and CSB were
unsuitable for cellulose production by either strain, and LS was unsuitable for production by strain 10821. However, strain
23770 produced 17% more cellulose from LS than from glucose, indicating that unamended LS could serve as a feedstock for bacterial
cellulose. 相似文献
99.
Lisa A. Liotta Irene Medina Jennifer L. Robinson Po-Shen Pan Jennifer V.C. Johnston Fiona A. Curtis Shelli R. McAlpine 《Tetrahedron letters》2004,45(46):8447-8450
Described are the syntheses of 15 macrocyclic peptides designed to trap Holliday junctions (HJs) in bacteria during site-specific and homologous recombination. This leads to inhibiting bacterial growth. These second generation macrocycles were based on the C-2 symmetrical HJ. They were synthesized using a strategy that permits elucidation of the amino acid role in binding HJs. The syntheses of these macrocycles are an important step in the development of a new class of antibiotics. 相似文献
100.
In this paper k-sets of type (a, b) with respect to hyperplanes are constructed in finite projective spaces using powers of Singer cycles. These are then used to construct further examples of sets of type (a, b) using various disjoint sets. The parameters of the associated strongly regular graphs are also calculated. The construction technique is then related to work of Foulser and Kallaher classifying rank three subgroups of AL(1, p
R). It is shown that the sets of type (a, b) arising from the Foulser and Kallaher construction in the case of projective spaces are isomorphic to some of those constructed in the present paper. 相似文献