全文获取类型
收费全文 | 277212篇 |
免费 | 3461篇 |
国内免费 | 840篇 |
专业分类
化学 | 145859篇 |
晶体学 | 4280篇 |
力学 | 12182篇 |
综合类 | 1篇 |
数学 | 32500篇 |
物理学 | 86691篇 |
出版年
2021年 | 2385篇 |
2020年 | 2699篇 |
2019年 | 2693篇 |
2018年 | 3614篇 |
2017年 | 3384篇 |
2016年 | 5275篇 |
2015年 | 3641篇 |
2014年 | 5205篇 |
2013年 | 12662篇 |
2012年 | 10604篇 |
2011年 | 12573篇 |
2010年 | 8570篇 |
2009年 | 8201篇 |
2008年 | 11371篇 |
2007年 | 11446篇 |
2006年 | 10627篇 |
2005年 | 9748篇 |
2004年 | 8859篇 |
2003年 | 7655篇 |
2002年 | 7413篇 |
2001年 | 7743篇 |
2000年 | 5940篇 |
1999年 | 4643篇 |
1998年 | 3891篇 |
1997年 | 3764篇 |
1996年 | 3709篇 |
1995年 | 3267篇 |
1994年 | 3248篇 |
1993年 | 3350篇 |
1992年 | 3483篇 |
1991年 | 3597篇 |
1990年 | 3338篇 |
1989年 | 3284篇 |
1988年 | 3282篇 |
1987年 | 3159篇 |
1986年 | 2972篇 |
1985年 | 4109篇 |
1984年 | 4283篇 |
1983年 | 3389篇 |
1982年 | 3674篇 |
1981年 | 3574篇 |
1980年 | 3450篇 |
1979年 | 3541篇 |
1978年 | 3630篇 |
1977年 | 3524篇 |
1976年 | 3669篇 |
1975年 | 3314篇 |
1974年 | 3344篇 |
1973年 | 3383篇 |
1972年 | 2324篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
S. V. Kondrashov Yu. I. Merkulova P. S. Marakhovskii T. P. D’yachkova K. A. Shashkeev O. V. Popkov O. V. Startsev M. V. Molokov E. V. Kurshev G. Yu. Yurkov 《Russian Journal of Applied Chemistry》2017,90(5):788-796
The dependence of the physicomechanical properties of epoxy nanocomposites subjected to heat and humidity aging on the type of covalently functionalized carbon nanotubes and on the uniformity of their distribution in the epoxy matrix was studied. Two types of carbon nanotubes were used: those modified with carboxy and amide groups. The elastic modulus, bending deflection, and ultimate bending strength for the initial epoxy nanocomposites with carbon nanotubes and for those subjected to heat and humidity aging were determined. The epoxy binders modified with carboxylated carbon nanotubes are more resistant to the action of aging factors. The presence of aggregates of carboxylated carbon nanotubes in the epoxy matrix positively influences the preservation of physicomechanical properties of the composite subjected to heat and humidity aging. Microscopic examination revealed structural features of the epoxy nanocomposite and their effect on the resistance of the composite to the heat and humidity aging. 相似文献
152.
E. G. Kalinina E. Yu. Pikalova V. D. Zhuravlev S. V. Scherbinin A. P. Safronov 《Russian Journal of Applied Chemistry》2017,90(6):862-869
Potentialities of the method of electrophoretic deposition of thin-film coatings based on micrometer powders of multidoped barium cerate BaCe0.8Sm0.19Cu0.01O3–δ (BCSCuO) and BaCe0.89Gd0.1Cu0.01O3–δ (BCGCuO) were considered. Micrometer powders of BCSCuO and BCGCuO were produced by the methods of solid-phase and citrate-nitrate syntheses, respectively. The dispersity, fraction composition, and electrokinetic potential of nonaqueous suspensions of these powders and the electrokinetic parameters of the electrophoretic deposition process were examined. An ultrasonic treatment and ultracentrifugation produced aggregatively stable suspensions of BCGCuO and BCSCuO micrometer particles in a mixed (70/30 vol %) isopropanol–acetyl acetone medium. These suspensions are characterized by high positive values of the zeta potential (+24 and +28 mV, respectively). Thin film coatings of the electrolyte materials BCSCuO and BCGCuO, which are of interest for the technology of medium-temperature solid-oxide fuel cells, were produced by the electrophoretic deposition onto a dense model cathode. 相似文献
153.
V. P. Isupov A. I. Katunina I. A. Borodulina S. S. Shatskaya 《Russian Journal of Applied Chemistry》2017,90(9):1469-1474
The reaction of magnesium hydroxide with a concentrated aqueous solution of iron(III) chloride yields a mixture of magnesium–iron layered double hydroxide and iron oxide–hydroxide in the akaganeite form. The content of these phases depends on the Mg/Fe atomic ratio in the starting reactant mixture. Iron oxide–hydroxide is the major reaction product at the Mg/Fe atomic ratio in the interval 1.5–1.75, and layered magnesium–iron layered double hydroxide, at Mg/Fe = 3–4. The ability of the synthesized products to take up As(III) from aqueous solutions was studied. These sorbents allow the arsenic concentration to be decreased from 3–5 mg L–1 to values below MPC (0.01 mg L–1). 相似文献
154.
P. P. Belov P. A. Storozhenko N. S. Voloshina M. G. Kuznetsova 《Russian Journal of Applied Chemistry》2017,90(11):1804-1809
New organic oxidants (aldehydes and ketones) allowing efficient synthesis of decaborane in a high yield via intermediate alkali metal salt were found. The sodium undecaborate oxidation process was refined, and new reaction stoichiometry was suggested. 相似文献
155.
O. E. Babkin L. A. Babkina T. N. Vasilevskaya M. V. Izotova P. A. Onushchenko S. V. Kozyrev S. G. Yastrebov 《Russian Journal of Applied Chemistry》2017,90(11):1845-1850
The structure of polymer films modified with zinc oxide nanocrystals was studied by the optical absorption and small-angle X-ray scattering methods. Small-angle X-ray scattering allows determination of the nanoparticle size distribution function, which is the decisive factor in predicting the optical properties of heterophase materials, including filled polymer films. The optical absorption spectrum of an acrylate polymer film doped with 1.6 wt % zinc oxide nanocrystals approaches the ideal absorber spectrum, which allows this material to be recommended for use as a protective color filter. 相似文献
156.
N. P. Grigoryan 《Russian Journal of Organic Chemistry》2017,53(1):103-108
Ethyl 4′-amino-5′,8′-dimethyl-1′H-spiro[cyclopentane-1,2′-naphthalene]-3′-carboxylate reacted with allyl isothiocyanate to give 3-allyl-7,10-dimethyl-2-sulfanylidene-2,3,5,6-tetrahydrospiro[benzo[h]quinazoline- 5,1′-cyclopentan]-4(1H)-one. Reactions of the latter with alkyl halides and hydrazine hydrate and subsequent transformations of the products afforded a series of new benzo[h]quinazoline derivatives containing an allyl group in the 3-position. 相似文献
157.
158.
M. S. Belova D. G. Korovina V. N. Tsygankov A. B. Varava I. P. Savchenkova O. A. Legon’kova 《Polymer Science Series D》2017,10(4):357-360
This paper considers the evaluation of the biosafety of cyanoacrylate adhesive in vitro on human multipotent mesenchymal stem cells. This adhesive is intended for medical use, in particular, for X-ray and endovascular interventions. A toxicity study was carried out in a culture of multipotent mesenchymal stem cells isolated from human subcutaneous fat. As a result of the work, the concentration of cyanoacrylate adhesive in lipiodol was chosen, which has the lowest toxicity. 相似文献
159.
When redox enzymes are attached to electrodes and undergo direct electron transfer, their voltammetric responses exhibit diverse shapes that, if analysed correctly, may inform about various aspects of the catalytic mechanism. Here we review the models that have been proposed to interpret these signals in relation to the thermodynamics and kinetics of interfacial and intramolecular electron transfer and active site chemistry. We list the corresponding equations in forms that are ready to use for fitting, and the commands that run these fits in the open source software QSoas. We relate these models to those that have been used for characterizing small synthetic redox catalysts diffusing in solution. 相似文献
160.
Mikhail P. Shushpanov 《Algebra Universalis》2017,78(3):377-387
We consider a lattice generated by three elements, one of which is completely modular. The free lattice with this property is proved to be finite. It is not modular and contains exactly 39 elements. We have also found a finite set of defining relations for the generating elements of this lattice. 相似文献