全文获取类型
收费全文 | 1184篇 |
免费 | 36篇 |
专业分类
化学 | 942篇 |
晶体学 | 8篇 |
力学 | 24篇 |
数学 | 74篇 |
物理学 | 172篇 |
出版年
2023年 | 8篇 |
2022年 | 26篇 |
2021年 | 54篇 |
2020年 | 37篇 |
2019年 | 61篇 |
2018年 | 49篇 |
2017年 | 42篇 |
2016年 | 47篇 |
2015年 | 41篇 |
2014年 | 37篇 |
2013年 | 73篇 |
2012年 | 77篇 |
2011年 | 81篇 |
2010年 | 66篇 |
2009年 | 49篇 |
2008年 | 70篇 |
2007年 | 48篇 |
2006年 | 55篇 |
2005年 | 40篇 |
2004年 | 25篇 |
2003年 | 25篇 |
2002年 | 20篇 |
2001年 | 17篇 |
2000年 | 7篇 |
1999年 | 6篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1995年 | 3篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1987年 | 4篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 5篇 |
1978年 | 7篇 |
1977年 | 11篇 |
1976年 | 13篇 |
1975年 | 9篇 |
1974年 | 9篇 |
1973年 | 9篇 |
1972年 | 6篇 |
1971年 | 12篇 |
1970年 | 5篇 |
1968年 | 3篇 |
1967年 | 2篇 |
1954年 | 2篇 |
排序方式: 共有1220条查询结果,搜索用时 31 毫秒
91.
Ekaterina A. Shilova Valery P. Perevalov Corinne Moustrou 《Tetrahedron letters》2008,49(21):3453-3457
The novel photochromic [2]rotaxane based on chromene molecule introduced into a crown-containing macrocyclic receptor was synthesized. The photochemical properties of rotaxane could be modified by the complexation of the crown ether moiety. 相似文献
92.
Ekaterina Alekseeva Yuri Kochetov Alexander Plyasunov 《European Journal of Operational Research》2008
We study the complexity of finding local minima for the p-median problem. The relationship between Swap local optima, 0–1 local saddle points, and classical Karush–Kuhn–Tucker conditions is presented. It is shown that the local search problems with some neighborhoods are tight PLS-complete. Moreover, the standard local descent algorithm takes exponential number of iterations in the worst case regardless of the tie-breaking and pivoting rules used. To illustrate this property, we present a family of instances where some local minima may be hard to find. Computational results with different pivoting rules for random and Euclidean test instances are discussed. These empirical results show that the standard local descent algorithm is polynomial in average for some pivoting rules. 相似文献
93.
Eric M. Galimov Vyacheslav S. Sevastyanov Nataliya E. Babulevich Ekaterina N. Tyurina 《Rapid communications in mass spectrometry : RCM》2009,23(16):2461-2466
The application of a high‐temperature electrochemical reactor based on stabilized zirconium dioxide (0.9 ZrO20.1 Y2O3) for organic gas sampling in continuous‐flow isotope‐ratio mass spectrometry (CF‐IRMS) has been found to be efficient. This solid electrolyte reactor (SER) can also be used as a chromatographic detector for the quantitative measurements of organic gases. A three‐electrode SER system was studied. Complete stoichiometric oxidation of organic gases has been achieved at 900–950°C due to the large catalytic surface area of the porous platinum coating. At this temperature, the oxygen ions formed from the oxygen of ambient air on the outer surface of the reactor migrate through the solid electrolyte under the action of the applied electric field and allow combustion of gases being analyzed to be effected. It should be noted that oxygen gas was not introduced into the gas‐carrier flow. Similar results for the measurements of carbon isotope ratios were obtained at the oxidation of hydrocarbon gases in both the standard and the solid electrolyte reactors. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
94.
Almir S. Gazizov Andrey V. Smolobochkin Ekaterina A. Anikina Julia K. Voronina Alexander R. Burilov Michail A. Pudovik 《合成通讯》2017,47(1):44-52
Herein we report our studies on the acid-catalyzed cyclisation of N-(4,4-diethoxybutyl)sulfonamides at the presence of polyatomic phenols as an efficient one-pot approach to the synthesis of 1-sulfonyl-2-arylpyrrolidines from the acyclic precursors. 相似文献
95.
The method proposed in [1, 2] is used to construct an analytic solution of the problem of two incompressible plates propelled by the explosion products of a condensed explosive. A solution of the problem by the classical methods of the gas dynamics of a perfect gas with =3 was previously obtained in [3]. However, the analysis carried out in [3] does not reproduce the entire wave configuration which may result from the interaction of expansion waves with moving plates and is limited to the study of the flow configuration realized in the case of single reflection of the waves from the plate contact boundary. This leads to overestimation of the limiting projection velocities when the relative masses of the plates are greater than unity.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 148–152, March–April, 1991. 相似文献
96.
E. A. Vlasova S. V. Makarov M. N. Malinkina 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(4):573-577
Cobalt octasulfophenyltetrapyrazinoporphyrazine was shown to be an effective catalyst of nitrite reduction by thiourea dioxide. The intermediate product of nitrite reduction was nitrogen(II) oxide, and the final product was ammonia. The kinetic and activation parameters of catalytic process stages were determined. 相似文献
97.
I. M. Vlasova A. M. Saletskii 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(6):1065-1070
The effective constants of binding for probes of the fluorescein family (fluorescein and its halogen derivatives, eosin and
erythrosin) with human serum albumin (HSA) at different pH were determined. It was found that the introduction of halogen
groups into the structural formula of fluorescein changes the character of the dependence on pH of the effective constant
of binding of a nanomarker with HSA: the nonlinear dependence of the effective constants of binding with its protein typical
for fluorescein, eosin, and erythrosine is characterized by an almost linear reduction with increasing pH dependence of the
effective constants of their binding with human serum albumin. It was shown that the presence of more electronegative atoms
in the structural formula of nanomarker leads to decrease of values of effective constants of nanomarker binding with HSA. 相似文献
98.
E. V. Vlasova V. M. Stoyanov M. M. El’chaninov B. S. Lukyanov 《Chemistry of Heterocyclic Compounds》2010,46(6):681-683
Bromination of 2-acetylfuran with copper(II) bromide in a mixture of ethyl acetate and chloroform leads selectively to furacyl
bromide, the nucleophilic substitution of bromine in which by OAc and subsequent use of the Weidenhagen reaction enabled the
synthesis of 4(5)-(2-furyl)imidazole. On N-methylation of this imidazole in KOH–acetone 2 isomers are formed, the 1-methyl-4-
and 1-methyl-5-(2-furyl)imidazoles. It was established that, unlike alkylation of 4(5)-phenylimidazole, the main product of
the reaction is 1-methyl-5-(2-furyl)imidazole. 相似文献
99.
T. K. Meleshko D. M. Il’gach N. N. Bogorad N. V. Kukarkina E. N. Vlasova A. V. Dobrodumov I. I. Malakhova N. I. Gorshkov V. D. Krasikov A. V. Yakimanskii 《Polymer Science Series B》2010,52(9-10):589-599
Multicentered initiators for the controlled (pseudoliving) radical polymerization are synthesized via polymer analog transformation of hydroxyl-containing polyimides based on o-aminophenols. Conditions providing variations in the degree of functionalization of polyimides by initiating 2-bromoisobutyrate groups are determined, and optimum conditions for the preparation of macroinitators containing the above groups in each repeat polyimide unit are found. Via the method of controlled radical polymerization with the atom transfer on multicentered macroinitiators in the presence of complexes of univalent copper halides, graft copolymers of poly(methylmethacrylate) on polyimide backbone are obtained. Molecular-mass characteristics of graft copolymers are studied via multiple-detection size-exclusion liquid chromatography. Preparation of graft copolymers (polymer brushes) with a homogeneous grafting density and a homogeneous length of side chains necessitates grafting of the side chain on the polyimide initiator, which contains initiating groups in each repeat unit. 相似文献
100.
M. L. Levit O. V. Nazarova T. N. Nekrasova A. V. Dobrodumov T. D. Anan’eva A. A. Nikiticheva E. N. Vlasova V. D. Pautov E. F. Panarin 《Polymer Science Series B》2010,52(11-12):648-655
New cholesterol-containing water-soluble polymers based on N-methacryloyl aminoglucose and N-vinylpyrrolidone are synthesized by free-radical copolymerization and polymer-analogous transformations. Binary and ternary copolymers of various composition containing N-allylamine and N,N,N-trimethylaminoethyl methacrylate methyl sulfate units and cholesterol residues are prepared. Luminescently labeled copolymers of the same composition are obtained. Effects of the nature of polymers and the amount of cholesterol in them on the intramolecular mobility of macromolecules in solution are studied with polarized luminescence. When 2–4 mol % of cholesterol residues are incorporated into the copolymer, the intramolecular mobility of macromolecules decreases, thus indicating formation of intramolecular compact structures via interaction of nonpolar cholesterol groups. In copolymers containing charged groups, these structures are looser than those in neutral copolymers. It is shown that macromolecules of cholesterol-containing polymers of various types can interact with each other. 1 This work was supported by the Russian Foundation for Basic Research (project no. 08-03-00324) and the Council for Grants of the President of the Russian Federation for Support of Leading Institutes of Higher Education (NSh-4391.2008.3). 相似文献