全文获取类型
收费全文 | 374896篇 |
免费 | 5073篇 |
国内免费 | 995篇 |
专业分类
化学 | 192684篇 |
晶体学 | 5590篇 |
力学 | 16343篇 |
综合类 | 8篇 |
数学 | 47750篇 |
物理学 | 118589篇 |
出版年
2021年 | 3671篇 |
2020年 | 4050篇 |
2019年 | 4395篇 |
2018年 | 6183篇 |
2017年 | 6322篇 |
2016年 | 9077篇 |
2015年 | 5576篇 |
2014年 | 8434篇 |
2013年 | 18983篇 |
2012年 | 15180篇 |
2011年 | 17567篇 |
2010年 | 12804篇 |
2009年 | 12434篇 |
2008年 | 15589篇 |
2007年 | 15355篇 |
2006年 | 14071篇 |
2005年 | 12491篇 |
2004年 | 11485篇 |
2003年 | 10052篇 |
2002年 | 9914篇 |
2001年 | 11224篇 |
2000年 | 8509篇 |
1999年 | 6582篇 |
1998年 | 5443篇 |
1997年 | 5218篇 |
1996年 | 5022篇 |
1995年 | 4260篇 |
1994年 | 4290篇 |
1993年 | 4122篇 |
1992年 | 4552篇 |
1991年 | 4664篇 |
1990年 | 4494篇 |
1989年 | 4333篇 |
1988年 | 4104篇 |
1987年 | 4223篇 |
1986年 | 3978篇 |
1985年 | 5028篇 |
1984年 | 5068篇 |
1983年 | 4177篇 |
1982年 | 4288篇 |
1981年 | 4004篇 |
1980年 | 3905篇 |
1979年 | 4170篇 |
1978年 | 4149篇 |
1977年 | 4144篇 |
1976年 | 4140篇 |
1975年 | 3895篇 |
1974年 | 3852篇 |
1973年 | 3908篇 |
1972年 | 2739篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The phase transitions and phase state of hydroxypropylcellulose mixtures with ethanol and acetic acid under static conditions and in the shear field have been studied by the turbidity-point method and polarization microscopy with the use of a polarization-photoelectric setup and a modified plastoviscometer. The deformation of solutions leads to a decrease in the temperature of mesomorphic phase formation and to a change in the type of liquid crystals from cholesteric to nematic. 相似文献
992.
On‐line coupling of LC and ICP‐MS has been used for fractionation and detection of species of Cu, Fe, I, Se and Zn in human serum. It has been shown that anion exchange chromatography provided better separation capability (both intra‐ and inter‐element) than size‐exclusion chromatography. The mobile phases for ion exchange chromatography consisted of Tris–HNO3 buffer and ammonium salt (nitrate, acetate or formate). Formate was found to be the best mobile phase counter ion, enabling good chromatographic separation, and is acceptable for mass spectrometry too. The quantitative evaluation of element concentrations adhering to individual fractions was performed by the peak area normalization method. The repeatability of results ranged from 3 to 15% (depending on the element concentration level) and represented the main part of the result uncertainty. The accuracy of Cu and Zn fraction determinations was confirmed by comparison with the isotope dilution technique. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
993.
S. V. Valueva L. N. Borovikova V. V. Koreneva Ya. I. Nazarkina A. I. Kipper V. V. Kopeikin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2007,81(7):1170-1173
Nanostructures formed during the reduction of ionic selenium in the selenite-ascorbate redox system in an aqueous solution of bovine serum albumin (BSA) were studied using static and dynamic light scattering and flow birefringence. It was established that this process results in the formation of stable aggregates of selenium nanoparticles that adsorb BSA molecules. It was found that highly-ordered superhigh-molecular-weight spherical nanostructures with high density and unique morphology are formed. Experiments with a cell culture of promyelocytic leukemia HL-60 showed that BSA adsorbed on selenium nanoparticles can inhibit the growth of tumor cells and deactivate free radicals with an efficiency comparable with that of sodium selenite. 相似文献
994.
Received December 31, 2001 / Published online May 21, 2002 相似文献
995.
996.
Recently, the theory of sortability of partition property has been shown to be an effective tool to prove the existence of an optimal partition with that property. In this paper, we extend the theory to multi-partition where the partition is on t types of components. We apply our results to settle an optimal assignment problem whose proof was incomplete as given in the literature. 相似文献
997.
998.
Effects of various cardioactive agents and a water extract of the pilose antler of Cervus nippon var. mantchuricus on periodic beating of cultured myocardial cell sheets were examined by using an image analyzing system. Norepinephrine increased the beating rate and the beating amplitude, whereas digoxin and forskolin enlarged only the beating amplitude. Verapamil and propranolol decreased both the beating rate and the beating amplitude. The water extract of the pilose antler showed no remarkable effects in a standard medium (2.1 mM Ca2+). However, it significantly increased the beating amplitude when the beating was suppressed by replacement with a low calcium medium (0.5 mM Ca2+). A similar effect was found for 70% ethanol-soluble and -insoluble fractions of the extract. 相似文献
999.
1000.
T Yamakawa H Matsukura Y Nomura M Yoshioka M Masaki H Igata S Okabe 《Chemical & pharmaceutical bulletin》1991,39(7):1746-1752
A series of N-substituted 2-[(2-imidazolylsulfinyl)methyl]anilines (3) was synthesized and evaluated for its biological activity against gastric H+/K(+)-ATPase prepared from rabbit stomach and gastric acid secretions in Heidenhain pouch dogs. Monoalkyl substituents on the nitrogen atom of the aniline moiety markedly inhibited the enzyme activity to the same degree as omeprazole, a representative H+/K(+)-ATPase inhibitor. Most of these compounds, administered at 3 mg/kg i.v. inhibited histamine-stimulated gastric acid secretion. The inhibitory activity of these derivatives on the enzymes at pH 6.0 was more potent than that at pH 7.4, and was distinctly correlated to stability in aqueous solution at pH 5.0. 相似文献