全文获取类型
收费全文 | 2476篇 |
免费 | 173篇 |
国内免费 | 125篇 |
专业分类
化学 | 1866篇 |
晶体学 | 55篇 |
力学 | 93篇 |
综合类 | 4篇 |
数学 | 335篇 |
物理学 | 421篇 |
出版年
2023年 | 20篇 |
2022年 | 52篇 |
2021年 | 55篇 |
2020年 | 43篇 |
2019年 | 61篇 |
2018年 | 55篇 |
2017年 | 48篇 |
2016年 | 90篇 |
2015年 | 86篇 |
2014年 | 115篇 |
2013年 | 181篇 |
2012年 | 169篇 |
2011年 | 193篇 |
2010年 | 117篇 |
2009年 | 91篇 |
2008年 | 155篇 |
2007年 | 114篇 |
2006年 | 120篇 |
2005年 | 109篇 |
2004年 | 102篇 |
2003年 | 79篇 |
2002年 | 102篇 |
2001年 | 71篇 |
2000年 | 55篇 |
1999年 | 43篇 |
1998年 | 32篇 |
1997年 | 27篇 |
1996年 | 32篇 |
1995年 | 22篇 |
1994年 | 25篇 |
1993年 | 24篇 |
1992年 | 17篇 |
1991年 | 15篇 |
1990年 | 22篇 |
1989年 | 13篇 |
1988年 | 8篇 |
1987年 | 13篇 |
1986年 | 12篇 |
1985年 | 13篇 |
1984年 | 15篇 |
1983年 | 9篇 |
1982年 | 21篇 |
1981年 | 19篇 |
1980年 | 10篇 |
1979年 | 12篇 |
1978年 | 11篇 |
1976年 | 9篇 |
1975年 | 9篇 |
1974年 | 14篇 |
1971年 | 9篇 |
排序方式: 共有2774条查询结果,搜索用时 15 毫秒
41.
Hibaone has been synthesized from manool through a photochemical cycloaddition of Δ8(14) podocarpene-13-one to ethylene or 1,2 dichloroethylene. 相似文献
42.
Oxidative stress has been implicated in mediation of vascular disorders. In the presence of vanadate, H(2)O(2) induced tyrosine phosphorylation of PLD1, protein kinase C-alpha (PKC-alpha), and other unidentified proteins in rat vascular smooth muscle cells (VSMCs). Interestingly, PLD1 was found to be constitutively associated with PKC-alpha in VSMCs. Stimulation of the cells by H(2)O(2) and vanadate showed a concentration-dependent tyrosine phosphorylation of the proteins in PLD1 immunoprecipitates and activation of PLD. Pretreatment of the cells with the protein tyrosine kinase inhibitor, genistein resulted in a dose-dependent inhibition of H(2)O(2)-induced PLD activation. PKC inhibitor and down-regulation of PKC abolished H(2)O(2)-stimulated PLD activation. The cells stimulated by oxidative stress (H(2)O(2)) caused increased cell migration. This effect was prevented by the pretreatment of cells with tyrosine kinase inhibitors, PKC inhibitors, and 1-butanol, but not 3-butanol. Taken together, these results suggest that PLD might be involved in oxidative stress-induced migration of VSMCs, possibly via tyrosine phosphorylation and PKC activation. 相似文献
43.
合成了含Mo(0)的三核化合物(Et4N)2[(CO)4Mo(μ-S)2Mo(μ-S)2Mo(CO)4](Ⅰ)和(Et4N)2[(CO)4Mo(μ-S)2W(μ-S)2Mo(CO)4](Ⅱ),测定了(Ⅰ)的晶体结构.Ⅰ属单斜晶系,空间群P2相似文献
44.
Using cotton as a solid-phase extraction sorbent of the precolumn, an on-line coupled precolumn preconcentration-liquid chromatography system with fluorescence detection was developed for the determination of PAHs in aqueous samples. Four PAHs including fluorene, phenanthrene, fluoranthene and benzo[k]fluoranthene were preconcentrated by a precolumn packed with 30 mg of absorbent cotton and then separated by C18 analytical column. When 100 ml of sample was enriched, the proposed procedure provided detection limits in the range of 0.5-57 ng l−1. Several water samples spiked with PAHs were analyzed with recoveries in the range of 92-119% at spiking level of 100 ng l−1 for fluorene, phenanthrene and fluoranthene, and 10 ng l−1 for benzo[k]fluoranthene, respectively. 相似文献
45.
A silica monomer-estrone complex (EstSi) having a thermally cleavable urethane bond and a cross-linkable triethoxysilane group was synthesized. From EstSi and TEOS, spherical silica particles with sizes of 1.5-3 mum were prepared. The template molecules were removed from the silica matrix by heating at 180 degrees C in DMSO in the presence of water, generating a cavity with an amino group. The control silica particles that had the same sizes and shapes were obtained with aminopropyl triethoxysilane and TEOS. When ethylene glycol was added in place of H2O, an ethyl alcoholic group was formed in the cavity. Their recognition ability and specific binding for estrone were characterized by uptake experiments. The estrone-imprinted silica particles showed a much higher recognition ability than the control silica particles and higher selectivity for estrone than testosterone propionate. 相似文献
46.
It is proved that the even-order equationy
(2n)
+p(t)y=0 is (n,n) oscillatory at if
相似文献
47.
48.
Conrad Newton Per Osland Tai Tsun Wu 《Zeitschrift fur Physik C Particles and Fields》1994,61(3):441-447
As a method of regularization, point splitting has played an essential role in the recent theoretical determination of the masses of the Higgs boson and the top quark. It is the purpose of this paper to put this pointsplitting regularization on a firm basis. The result turns out to be extremely simple: replace the usual vertex factor-ieγ µ in quantum electrodynamics by $$ - ie(\gamma _\mu - \frac{{\not p}}{{p \cdot \delta }}\delta _\mu ),$$ wherep is the momentum of the photon line, andδ µ is the distance for point splitting. No additional vertices are needed. 相似文献
49.
Nguyen Quang Do Thong 《K-Theory》1993,7(5):429-441
The well-known formula of Riemann-Hurwitz gives the change of genuses in ann-fold covering of compact connected Riemann surfaces. In Iwasawa theory, there existp-adic analogues which give the change of certain ±-invariants in ap-extension ofCM number fields. Using functorial and arithmetical properties ofK
3, we extend such Riemann-Hurwitzp-adic formulas to non-CM fields, assuming some restrictive hypotheses on the capitulation ofK
2. 相似文献
50.
|