全文获取类型
收费全文 | 1017篇 |
免费 | 36篇 |
专业分类
化学 | 839篇 |
晶体学 | 9篇 |
力学 | 23篇 |
数学 | 70篇 |
物理学 | 112篇 |
出版年
2024年 | 3篇 |
2023年 | 11篇 |
2022年 | 67篇 |
2021年 | 53篇 |
2020年 | 33篇 |
2019年 | 62篇 |
2018年 | 41篇 |
2017年 | 35篇 |
2016年 | 45篇 |
2015年 | 38篇 |
2014年 | 30篇 |
2013年 | 63篇 |
2012年 | 70篇 |
2011年 | 68篇 |
2010年 | 55篇 |
2009年 | 42篇 |
2008年 | 59篇 |
2007年 | 37篇 |
2006年 | 46篇 |
2005年 | 36篇 |
2004年 | 16篇 |
2003年 | 24篇 |
2002年 | 16篇 |
2001年 | 15篇 |
2000年 | 5篇 |
1999年 | 6篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1970年 | 2篇 |
1968年 | 2篇 |
1966年 | 1篇 |
排序方式: 共有1053条查询结果,搜索用时 31 毫秒
11.
I. P. Nazarova A. I. Glushenkova N. T. Ul'chenko G. P. Moiseeva 《Chemistry of Natural Compounds》1989,25(1):54-57
A study has been made of the gossypol pigments of the seeds and roots of a cotton plant of the variety Tashkent-1 infected with wilt in comparison with a healthy plant. The amount of gossypol in the infected plant was lower than in the healthy plant. In the diseased plant, gossypurpurin was concentrated in the roots, and in the healthy plant it was concentrated in the seeds. Gossypol possessing optical activity was detected in the seeds and roots of both the healthy and the diseased plants.Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 63–66, January–February, 1989. 相似文献
12.
Express detection of nonylphenol in water samples by fluorescence polarization immunoassay 总被引:6,自引:0,他引:6
Yakovleva JN Lobanova AY Shutaleva EA Kourkina MA Mart'ianov AA Zherdev AV Dzantiev BB Eremin SA 《Analytical and bioanalytical chemistry》2004,378(3):634-641
The development of express method for detection of endocrine-disrupting chemicals (EDC) such as alkylphenols is required for ecological monitoring. Several attempts have been made to produce antibodies against 4-nonylphenol (NP) in recent years. This work describes the production of new antibodies against NP and also summarizes the characterization of antibodies obtained earlier. Three approaches used to produce alkylphenol-specific antibodies are compared; these are based on: 1. omega-(4-hydroxyphenyl)nonanoic or omega-(4-hydroxyphenyl)heptanoic acid NP derivatives designed to mimic the linear NP isomer; 2. 4-aminophenol, which potentially mimics various substituted phenolic compounds with different side-chain structures at position 4 of the benzene ring; and 3. a mixture of branched NP isomers, conjugated to the carrier protein via a benzene ring by the Mannich reaction, and expected to be the closest mimic of NP structure by preserving its natural alkyl moiety.Fluorescence polarization immunoassays based on different combinations of antibody and labeled antigen for screening detection of NP were developed and structural aspects of assay sensitivity and specificity were investigated. The assays based on the antisera raised against omega-(4-hydroxyphenyl)nonanoic acid and NP conjugate via Mannich reaction are capable of express detection of NP with detection limit of 7 microg mL(-1 )and assay dynamic range of 18-300 microg mL(-1). 相似文献
13.
We find that the CP-violating asymmetry
at the one-loop order within the minimal supersymmetric extension of the standard model is of the order of few percent for maximal CP violation. It could be measured by considering the rate difference in the one-lepton events. 相似文献
Full-size image
14.
Gekhman A. E. Amelichkina G. E. Moiseeva N. I. Vargaftik M. N. Moiseev I. I. 《Kinetics and Catalysis》2001,42(4):496-505
Anthracene and its alkyl derivatives undergo oxidation in the V(V)/H2O2/AcOH system via a nonradical mechanism through the intermediate formation of the vanadium(V) complex with singlet dioxygen as a ligand. The 1O2molecule is transferred from this complex to an unsaturated substrate. The free singlet dioxygen 1O2(1
g
) is almost inactive toward anthracene in AcOH solution. Consequently, the vanadium(V) complex with singlet dioxygen is the only oxidant species active in the reaction. The ratio between the rate constant of the reaction of this complex with 2-ethylanthracene and the rate constant of its deactivation is an order of magnitude greater than the ratio between the rate constant of the reaction of dissolved free singlet dioxygen with the same substrate and the rate constant of its deactivation (physical quenching). 相似文献
15.
Shmyreva Zh. V. Moiseeva L. V. Ponomareva L. F. Zelenskaya Yu. E. Dolgova T. Yu. 《Russian Journal of Applied Chemistry》2003,76(11):1862-1863
Effect of transition metal (Mn, Fe, Co, Ni, Cu, Zn) diketonates on oxidation of sunflower-seed oil with atmospheric oxygen was studied. 相似文献
16.
17.
K. P. Butin A. A. Moiseeva T. V. Magdesieva E. V. Sergeeva V. I. Rozenberg V. G. Kharitonov 《Russian Chemical Bulletin》1994,43(5):783-789
The potentials of electrochemical oxidation (
) and reduction (
) of monobromo- and isomeric di- and tribromo[2.2]paracyclophanes as well as
of mono-, di-, and tribromobenzenes were measured in acetonitrile. The similarity between the properties ofpseudo-para-disubstituted cyclophanes andmeta-disubstituted benzenes, on the one hand, andpseudo-meta-disubstituted cyclophanes andpara-disubstituted benzenes, on the other hand, was confirmed by the existence of a linear relationship between
of bromo-substituted [2.2]paracyclophanes and
of the corresponding bromo-substituted benzenes. The results were explained in terms of the qualitative theory of molecular orbitals, taking into account a through space interaction between the -systems of the benzene rings.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 839–845, May, 1994.The authors wish to express their gratitude to Professor R. Hoffmann (Cornell University, USA) for a useful discussion and criticisms of the text of this paper.This work was financially supported by the Russian Foundation for Basic Research (Project 93-03-5246). 相似文献
18.
G. P. Moiseeva I. D. Sham'yanov A. Mallabaev M. R. Yagudaev G. P. Sidyakin 《Chemistry of Natural Compounds》1980,15(5):569-571
A study of the circular dichroism of chlorine-containing guainolides has shown that a negative Cotton effect in the 260-nm region correlates with the trans-linkage of the lactone ring in acroptilin, hyrcanin, chlorohyssopifolin B, elegin, and biebsanin. It has been established that this nature of the linkage does not change on relactonization and hydrogenation. A chloromethylene substituent at C4 causes a bathochromic shift of the lactone Cotton effect.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 650–652, September–October, 1979. 相似文献
19.
G. P. Moiseeva I. D. Sham'yanov A. Mallabaev M. R. Yagudaev G. P. Sidyakin 《Chemistry of Natural Compounds》1979,15(5):569-571
A study of the circular dichroism of chlorine-containing guainolides has shown that a negative Cotton effect in the 260-nm region correlates with the trans-linkage of the lactone ring in acroptilin, hyrcanin, chlorohyssopifolin B, elegin, and biebsanin. It has been established that this nature of the linkage does not change on relactonization and hydrogenation. A chloromethylene substituent at C4 causes a bathochromic shift of the lactone Cotton effect. 相似文献
20.
The circular dichroism method has been used to establish the stereochemical features of the structure of the withasteroids. The 22S-configuration of the asymmetric center has been confirmed for physangulide. The 22R-configuration has been confirmed for 14-hydroxyixocarpanolide, vamonolide, ixocarpanolide, 24,25-epoxywithanolide D, and withanolide T. On the basis of changes in the circular dichroism spectra in acid and alkaline media it is suggested that in compounds having a 4-hydroxy-1-oxo-5,6-epoxy-2,3-ene grouping the 2,3 bond disappears, while in compounds having a 5-hydroxy-1-oxo-6,7-epoxy-2,3-ene grouping dehydration takes place at C-4-C-5. These characteristics can be used in the identification of the withasteroids. The isolation of withanolide T from the leaves ofPhysalis angulata L. is described and its spectral characteristics are given.Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 371–376, May–June, 1990. 相似文献