全文获取类型
收费全文 | 234761篇 |
免费 | 3337篇 |
国内免费 | 1454篇 |
专业分类
化学 | 132169篇 |
晶体学 | 3307篇 |
力学 | 9356篇 |
综合类 | 61篇 |
数学 | 26795篇 |
物理学 | 67864篇 |
出版年
2020年 | 1936篇 |
2019年 | 2065篇 |
2018年 | 2645篇 |
2017年 | 2661篇 |
2016年 | 3922篇 |
2015年 | 2647篇 |
2014年 | 3809篇 |
2013年 | 9566篇 |
2012年 | 8340篇 |
2011年 | 10279篇 |
2010年 | 7082篇 |
2009年 | 6833篇 |
2008年 | 9496篇 |
2007年 | 9659篇 |
2006年 | 9168篇 |
2005年 | 8436篇 |
2004年 | 7525篇 |
2003年 | 6655篇 |
2002年 | 6555篇 |
2001年 | 6890篇 |
2000年 | 5229篇 |
1999年 | 3812篇 |
1998年 | 3195篇 |
1997年 | 3181篇 |
1996年 | 3214篇 |
1995年 | 2765篇 |
1994年 | 2881篇 |
1993年 | 2709篇 |
1992年 | 2961篇 |
1991年 | 3030篇 |
1990年 | 2814篇 |
1989年 | 2717篇 |
1988年 | 2689篇 |
1987年 | 2621篇 |
1986年 | 2619篇 |
1985年 | 3482篇 |
1984年 | 3565篇 |
1983年 | 2955篇 |
1982年 | 3254篇 |
1981年 | 3003篇 |
1980年 | 2818篇 |
1979年 | 2964篇 |
1978年 | 3175篇 |
1977年 | 3184篇 |
1976年 | 3207篇 |
1975年 | 2924篇 |
1974年 | 3043篇 |
1973年 | 3097篇 |
1972年 | 2378篇 |
1971年 | 1895篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
G. N. Dalimova Kh. A. Abduazimov R. K. Rakhmanberdieva V. G. Gorokhova L. N. Petrushenko B. A. Babkin N. A. Koshilev 《Chemistry of Natural Compounds》1994,30(3):400-403
On the basis of the results of acid hydrolysis, chromatographic analysis of the hydrolysates, and a study of IR spectra, it has been established that the suspended particles liberated under the action of electrohydraulic shocks on heterodisperse water—plant systems consist of small fragments of the lignocarbohydrate complex of the plant tissue. 相似文献
112.
The qualitative and quantitative compositions of the carbohydrates of the leaf vegetables Lactuca sativa L., Spinacea oleracea L., and Rumex acetosa L. have been studied.M. V. Lomonosov Odessa Technological Institute of the Food Industry. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 349–351, May–June, 1993. 相似文献
113.
114.
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
115.
Chromatographia - Previously [11], the theoretical limit ofresolution in one class of chromatographic conditions was found and its proof was briefly outlined. Here, the theoretical limits... 相似文献
116.
117.
118.
Synthesis of optically active sesquiterpenes with a eudesmane C-skeleton from the chiral starting material thujone involves transformation of a tricyclic intermediate (1R,2R,4S)-1,7-dimethyl-4-(1-methylethyl)tricyclo[4.4.0.02,4]dec-6-en-8-one ( 2 ) into the bicyclic compound β -cyperone ( 5 ). Hydroxylation of 2 at C(5) or C(11) permits subsequent opening of the cyclopropane ring and rearrangement to β -cyperone. In this publication, studies involving hydroxylation of 2 by fungal cultures are presented. The resultant products are useful intermediates in efficient synthesis of eudesmane sesquiterpenes. Of five fungi tested, Rhizopus oryzae ATCC 11145 proved most versatile. It hydroxylates at the exocyclic C(11) position in high yield (70%) and, to a lesser extent, at C(5) (5%). Enzymatic activity appears at the end of growth phase and at least 2.2 g of 2 per liter can be metabolized without significant loss of product yield. A second fungus, Cunninghamella echinulata ATCC 9244, proved most useful for hydroxylation of derivatives of 2 for the preparation of derivatives of β -cyperone, although product yields were low (2–20%), some derivatives were nonreactive, and hydroxylation at C(9) occurred. The relationship between precursor structure and enzyme affinity is discussed. 相似文献
119.
120.
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