全文获取类型
收费全文 | 181801篇 |
免费 | 37561篇 |
国内免费 | 26324篇 |
专业分类
化学 | 120448篇 |
晶体学 | 2187篇 |
力学 | 12282篇 |
综合类 | 625篇 |
数学 | 22214篇 |
物理学 | 87930篇 |
出版年
2024年 | 607篇 |
2023年 | 2743篇 |
2022年 | 4294篇 |
2021年 | 4317篇 |
2020年 | 5131篇 |
2019年 | 5399篇 |
2018年 | 4796篇 |
2017年 | 5020篇 |
2016年 | 7116篇 |
2015年 | 7043篇 |
2014年 | 8024篇 |
2013年 | 11645篇 |
2012年 | 13397篇 |
2011年 | 15279篇 |
2010年 | 15325篇 |
2009年 | 15210篇 |
2008年 | 9739篇 |
2007年 | 8864篇 |
2006年 | 8077篇 |
2005年 | 7560篇 |
2004年 | 7016篇 |
2003年 | 5580篇 |
2002年 | 5127篇 |
2001年 | 5122篇 |
2000年 | 4091篇 |
1999年 | 4650篇 |
1998年 | 4011篇 |
1997年 | 3703篇 |
1996年 | 4158篇 |
1995年 | 4158篇 |
1994年 | 4202篇 |
1993年 | 3919篇 |
1992年 | 3437篇 |
1991年 | 3021篇 |
1990年 | 2545篇 |
1989年 | 2399篇 |
1988年 | 2285篇 |
1987年 | 1528篇 |
1986年 | 1583篇 |
1985年 | 1201篇 |
1984年 | 1242篇 |
1983年 | 521篇 |
1982年 | 1040篇 |
1981年 | 854篇 |
1980年 | 858篇 |
1979年 | 582篇 |
1978年 | 578篇 |
1977年 | 667篇 |
1976年 | 1085篇 |
1972年 | 553篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
171.
172.
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
173.
174.
Addition of functionalized zinc-copper reagents to the title complexes proceeds in a highly diastereoselective fashion to afford dienol complexes. The relative configurations of adducts 3d were determined by single X-ray diffraction analysis. 相似文献
175.
A new secoiridoid, multiflorin (1) has been isolated from the EtOAc-soluble fraction of Jasminum multiflorum (Oleaceace). The structure of I was determined by application of spectral methods. 相似文献
176.
Twelve series of linear oligomers of four different degrees of polymerization (xn = 8.77−41.55), having a common perfluorinated random copolymeric chain as molecular body and two equal foreign end units of one of the types listed in Table 1, have been synthesized by derivatization of base samples of one of them having a diolic---CH2OH functionality. The glass transition temperature Tg of all the series was measured and thus examined as a function of xn. A clear end unit effect is observed, dominantly determined in every series by chemical nature and structure of the end units, quantitatively expressed at any xn by different positive or negative Tg deviations from the common asymptotic Tg∞ value. The results are also discussed in terms of copolymer end effect and of relation between Tg and end copolymeric composition. 相似文献
177.
A short regio- and stereoselective synthesis of two carbocyclic 3′-deoxynucleoside analogues is described, the key step of which consists in the photosensitized addition of MeOH to a cyclopent-2-enone derivative. As in both cases functional groups capable to react with each other are present in the same molecule, the synthetic compounds can form polymers similar to oligonucleotides. 相似文献
178.
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
179.
180.