全文获取类型
收费全文 | 358880篇 |
免费 | 2280篇 |
国内免费 | 746篇 |
专业分类
化学 | 175140篇 |
晶体学 | 5257篇 |
力学 | 17683篇 |
综合类 | 7篇 |
数学 | 52682篇 |
物理学 | 111137篇 |
出版年
2021年 | 2401篇 |
2020年 | 2668篇 |
2019年 | 3079篇 |
2018年 | 11386篇 |
2017年 | 12023篇 |
2016年 | 9255篇 |
2015年 | 3799篇 |
2014年 | 5263篇 |
2013年 | 11982篇 |
2012年 | 12811篇 |
2011年 | 21456篇 |
2010年 | 13965篇 |
2009年 | 13987篇 |
2008年 | 19390篇 |
2007年 | 22422篇 |
2006年 | 9942篇 |
2005年 | 14152篇 |
2004年 | 10721篇 |
2003年 | 10297篇 |
2002年 | 8456篇 |
2001年 | 7884篇 |
2000年 | 6299篇 |
1999年 | 4537篇 |
1998年 | 3980篇 |
1997年 | 3898篇 |
1996年 | 3723篇 |
1995年 | 3135篇 |
1994年 | 3191篇 |
1993年 | 3218篇 |
1992年 | 3405篇 |
1991年 | 3504篇 |
1990年 | 3348篇 |
1989年 | 3364篇 |
1988年 | 3233篇 |
1987年 | 3163篇 |
1986年 | 3027篇 |
1985年 | 3859篇 |
1984年 | 4105篇 |
1983年 | 3340篇 |
1982年 | 3640篇 |
1981年 | 3423篇 |
1980年 | 3186篇 |
1979年 | 3461篇 |
1978年 | 3717篇 |
1977年 | 3663篇 |
1976年 | 3593篇 |
1975年 | 3407篇 |
1974年 | 3396篇 |
1973年 | 3548篇 |
1972年 | 2400篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
M. A. Mikhaleva B. M. Bolotin T. A. Kizner E. S. Serebrykova 《Chemistry of Heterocyclic Compounds》1994,30(1):79-81
We have synthesized 5-alkyl(alkoxy)-2-(o-lzydroxy-p-alkoxyphenyl)pyrimidines and considered the effect of the OH group on the inesomorphism. We have found that in binuclear o-hydroxyarylpyrimidines, an ortho OH group forming an intramolecular hydrogen bond increases Tmp, inhibits the appearance of nematic properties, and promotes the appearance of a smectic A.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 30, No. 1, pp. 90–92, January, 1994. 相似文献
93.
94.
The electron-impact mass spectra of a number of phenylpropanoids and iridoid glycosides containing a phenylethanoid fragment in their structure have been studied. This has revealed features of the formation of fragments of 4-hydroxyphenylethyl and 3,4-dihydroxyphenylethyl alcohols and also of fragments of phenylethylamine and indolylethylamine derivatives present in the structures of the compounds investigated. 相似文献
95.
96.
97.
98.
S. O. Kolusheva B. A. Salakhutdinov T. F. Aripov L. P. Vernon 《Chemistry of Natural Compounds》1994,29(4):523-525
It has been shown by the ESR of spin probes that thionin initially interacts with with negatively charged membranes electrostatically and then passes into the membranes to a depth comparable with the length of the hydrophobic sections of the protein loops.Institute of Bioorganic Chemistry, Academy of Sciences of the Republic of Uzbekistan, Tashkent. Brigham Young University, Provo, Utah, USA. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 594–597, July–August, 1993. 相似文献
99.
The properties of a polymer-concrete composed of polyester matrix and locally available rock aggregate are investigated. The formula of the concrete is found by an experimental-calculation approach in such a way as to attain a closer packing of the aggregate particles on the one hand, and to ensure the needed processing characteristics (placeability) of the mix on the other. It is shown experimentally that the material obtained has a rather high compression strength. Under prolonged compression loads, the polymer-concrete exhibits a noticeable creep behavior with a linear relation between the creep strains and stresses. After the action of half the ultimate load over 3000 h, the total strains exceed the instantaneous ones by 2.0 to 2.2 times. The accumulation of irreversible strains is also observed; however, their contribution to the total strain is small. It is found that the stress-strain relation can be represented by the equation of linear hereditary creep theory.Institute of Polymer Mechanics, University of Latvia, Riga, LV-1006, Latvia. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 2, pp. 147–162, March–April, 1999. 相似文献
100.
The applicability of differential electrolytic potentiometry as a detection system in flow injection analysis is investigated. A computer-controlled injector which delivers precise volumes of sample solutions in a reproducible manner was developed. Conditions such as current density employed, the concentrations of the solutions used and the flow rate were optimized. Chloride in water was determined by means of this system. The relation between chloride concentration and the measured signal was found to be Nernstian for solutions of concentrations above 6 μg ml−1 chloride. For solutions below this concentration, the relation is linear. 相似文献