全文获取类型
收费全文 | 346304篇 |
免费 | 3530篇 |
国内免费 | 1046篇 |
专业分类
化学 | 177153篇 |
晶体学 | 5885篇 |
力学 | 15512篇 |
综合类 | 7篇 |
数学 | 40411篇 |
物理学 | 111912篇 |
出版年
2021年 | 2638篇 |
2020年 | 2941篇 |
2019年 | 3290篇 |
2018年 | 4321篇 |
2017年 | 4305篇 |
2016年 | 6436篇 |
2015年 | 3915篇 |
2014年 | 6241篇 |
2013年 | 15624篇 |
2012年 | 11975篇 |
2011年 | 14434篇 |
2010年 | 10183篇 |
2009年 | 10088篇 |
2008年 | 13309篇 |
2007年 | 13279篇 |
2006年 | 12670篇 |
2005年 | 11345篇 |
2004年 | 10578篇 |
2003年 | 9402篇 |
2002年 | 9151篇 |
2001年 | 10499篇 |
2000年 | 7998篇 |
1999年 | 6204篇 |
1998年 | 5106篇 |
1997年 | 5035篇 |
1996年 | 4667篇 |
1995年 | 4389篇 |
1994年 | 4224篇 |
1993年 | 4027篇 |
1992年 | 4597篇 |
1991年 | 4532篇 |
1990年 | 4415篇 |
1989年 | 4166篇 |
1988年 | 4221篇 |
1987年 | 4252篇 |
1986年 | 3961篇 |
1985年 | 5200篇 |
1984年 | 5476篇 |
1983年 | 4654篇 |
1982年 | 4891篇 |
1981年 | 4702篇 |
1980年 | 4577篇 |
1979年 | 4771篇 |
1978年 | 4898篇 |
1977年 | 4840篇 |
1976年 | 4939篇 |
1975年 | 4688篇 |
1974年 | 4633篇 |
1973年 | 4895篇 |
1972年 | 3176篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
201.
Kh. T. Mirzaazimova S. D. Gusakova A. I. Glushenkova 《Chemistry of Natural Compounds》1994,30(5):555-558
The yields and fatty acid compositions of the free lipids and lipids weakly and strongly bound to proteins from seeds of cottonplant varieties resistant and susceptible to verticillium wilt have been determined and the changes in these indices in the seeds of the infected plants have been measured. It has been established that the seeds of healthy plants of the two varieties are similar in the qualitative compositions of the lipids and fatty acids but differ with respect the amounts of lipids in them bound with protein in different ways and with respect to the amounts of the individual fatty acids. The observed changes in the lipid and fatty-acid compositions depend on the degree of resistance of the variety to wilt. 相似文献
202.
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
203.
204.
205.
D. Kh. Khalikov M. G. Mukhiddinov M. G. Asoev V. A. Degtyarev 《Chemistry of Natural Compounds》1994,30(6):734-738
Some features of the kinetics of the hydrolysis of apple protopectin have been studied on the basis of an analysis of monosaccharide residues of the pectin substances and determinations of characteristic viscosity. It has been shown that the fine regulation of the physicochemical parameters of the hydrolysis of protopectin leads to the formation of pectin substances with different properties. 相似文献
206.
207.
N. I. Khamidov B. T. Kadyrov N. T. Ul'chenko A. Sh. Isamukhamedov A. I. Glushenkova 《Chemistry of Natural Compounds》1994,30(4):430-433
The phsicochemical indices and the fatty-acid and triacylglycerol compositions of cottonseed and palm oils, of cottonseed
oil hydrogenate, and of compositions based on them have been determined with the aid of IR and UV spectroscopies, GLC analysis,
and chemical transformations. The compositions and amounts of the main classes of lipids in the initial oils and the hydrogenate
have been studied. It has been found that in the process of hydrogenation the amount of oxygenated components falls.
The work was conducted with the financial support of the Uzbek Fund for Fundamental Investigations. 相似文献
208.
209.
V. N. Plugar' Ya. V. Rashkes A. Ovezdurdyev I. D. Sham'yanov 《Chemistry of Natural Compounds》1994,29(4):462-466
The main directions of fragmentation and the EI of six pseudoguaianolides related to carpesiolin have been studied. It has been established that acylation of the OH group at C-6 suppresses the selective breakdown of the guaiane skeleton, while the simultaneous presence of AcO groups at C-2 and C-4 favors the formation of a number of characteristic ions. The hydrogenation of the exomethylene group has no appreciable influence on direction of fragmentation.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 530–535, July–August, 1993. 相似文献
210.
D. N. Dalimov M. B. Gafurov Z. Tilyabaev F. G. Kamaev A. A. Abdugakhabov 《Chemistry of Natural Compounds》1994,30(1):61-64
The synthesis has been effected of alkyl anabasinoprop-2-yl and alkyl piperidinoprop-2-yl methylphosphonothionates. It has been shown by1H,13C and31P NMR spectroscopies that the anabasine derivatives exist in solution as four diastereomeric forms. The kinetics of the interaction of the compounds synthesized with two types of cholinesterases has been studied.A. S. Sadykov Institute of Bioorganic Chemistry, Academy of Sciences of the Republic of Uzbekistan, Tashkent, Fax 627071. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 70–74, January–February, 1994. 相似文献