全文获取类型
收费全文 | 23901篇 |
免费 | 53篇 |
国内免费 | 45篇 |
专业分类
化学 | 10023篇 |
晶体学 | 405篇 |
力学 | 941篇 |
综合类 | 11篇 |
数学 | 3471篇 |
物理学 | 9148篇 |
出版年
2023年 | 13篇 |
2022年 | 179篇 |
2021年 | 367篇 |
2020年 | 372篇 |
2019年 | 547篇 |
2018年 | 1004篇 |
2017年 | 1114篇 |
2016年 | 1321篇 |
2015年 | 532篇 |
2014年 | 1096篇 |
2013年 | 1664篇 |
2012年 | 1494篇 |
2011年 | 1551篇 |
2010年 | 1770篇 |
2009年 | 1720篇 |
2008年 | 1683篇 |
2007年 | 1612篇 |
2006年 | 1410篇 |
2005年 | 877篇 |
2004年 | 612篇 |
2003年 | 319篇 |
2002年 | 312篇 |
2001年 | 304篇 |
2000年 | 608篇 |
1999年 | 347篇 |
1998年 | 446篇 |
1997年 | 425篇 |
1996年 | 108篇 |
1995年 | 31篇 |
1994年 | 27篇 |
1993年 | 4篇 |
1992年 | 11篇 |
1991年 | 9篇 |
1990年 | 14篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 8篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1978年 | 3篇 |
1977年 | 4篇 |
1974年 | 3篇 |
1971年 | 4篇 |
1968年 | 10篇 |
1875年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 18 毫秒
171.
A. V. Samodurov S. V. Vosel’ A. M. Baklanov A. A. Onishchuk V. V. Karasev 《Colloid Journal》2013,75(4):397-408
Homogeneous nucleation of ibuprofen vapor is studied in a nucleation flow chamber, a horizontal quartz tube equipped with an external heater. The area of the chamber where the nucleation proceeds most efficiently is determined, and the volume of this area is estimated. The temperature and supersaturation are determined and the homogeneous nucleation rate is calculated for this area. Saturation vapor pressure over liquid ibuprofen is measured in a temperature range of 353–383 K. Using an exact formula that has recently been derived for the nucleation rate based on the works by Kusaka, Reiss, as well as the Frenkel liquid-kinetics theory, surface tension and the radius of surface of tension of a critical nucleus σ= 25.9 mN/m and R s = 1.6 nm, respectively, are calculated at 318 K. The measurement of the surface tension of an ibuprofen planar surface shows that, at 318 K, σ∞ = 24.38 mN/m; i.e., σ is higher than σ∞ by 6%. A critical nucleus is established as containing nearly 36 ibuprofen molecules. 相似文献
172.
D. G. Filatova I. F. Seregina K. B. Osipov L. S. Foteeva V. V. Pukhov A. R. Timerbaev M. A. Bol’shov 《Journal of Analytical Chemistry》2013,68(2):106-111
A procedure for the determination of gallium in biological fluids by inductively coupled plasma mass spectrometry was developed. The detection limits of gallium calculated from the 3s value were 60 ng/L for urine, 32 ng/L for a model solution of intestinal juice, and 50 ng/L for serum. The accuracy of the procedure was tested using a standard addition method. The nature of a background signal on the masses of gallium isotopes was studied with the use of a high-resolution mass spectrometer, and the background concentration of gallium in biological fluids was evaluated (5–7 ng/L). It was found that a background level in measurements performed on a quadrupole mass spectrometer depends on the interfering influence of polyatomic ions with close m/z ratios rather than on the background concentration of gallium. The procedure makes it possible to study the stability of pharmaceutical preparations based on gallium in biological media, their metabolism, and the excretion of preparations from the body. 相似文献
173.
A. A. Volod’kin L. N. Kurkovskaya G. E. Zaikov S. M. Lomakin 《Russian Chemical Bulletin》2013,62(10):2265-2265
174.
R. M. Islamova O. I. Ishkinina S. V. Nazarova O. N. Chupakhin I. A. Utepova N. M. Andriyashina A. O. Terent’ev 《Russian Chemical Bulletin》2013,62(5):1282-1285
Cyclic peroxides as initiators for the radical polymerization of methyl methacrylate were proposed. The initial rates, initiation rates, and effective activation energies of polymerization initiated by cyclic peroxides and cyclic peroxide-1-pyridyl-2-ferrocene systems were determined. The radical yields to the volume upon the thermal decomposition of cyclic peroxides and their catalytic decomposition in the presence of 1-pyridyl-2-ferrocene were determined. In combination with 1-pyridyl-2-ferrocene cyclic peroxides form efficient initiating systems favoring an increase in the polymerization rate, a decrease in the molecular weights, and an increase in syndiotacticity of the synthesized poly(methyl methacrylate). 相似文献
175.
E. V. Shchegol’kov Ya. V. Burgart V. I. Saloutin O. N. Chupakhin 《Russian Chemical Bulletin》2013,62(1):220-222
Fluorinated 2-amino-5-phenyl-1,3,4-thiadiazines were obtained for the first time. A study of their tautomeric structures revealed that trifluoromethyl-containing 1,3,4-thiadiazines exist as the 4H-tautomer in both solutions and the solid state, while their monofluoroaryl analogs exist as the 6H-tautomer. 相似文献
176.
A. G. Medvedev A. A. Mikhailov P. V. Prikhodchenko T. A. Tripol’skaya O. Lev A. V. Churakov 《Russian Chemical Bulletin》2013,62(8):1871-1876
The crystal structures of new peroxosolvates of the following pyridinemonocarboxylic acids were studied: picolinic 2-C5H4NCOOH·H2O2 (1), nicotinic 3-C5H4NCOOH·H2O2 (2), and isonicotinic 4-C5H4NCOOH·2H2O2 (3). In these compounds, the acids exist exclusively as zwitterions, as opposed to non-solvated crystals. In compounds 1–3, the hydrogen peroxide molecules form two donor hydrogen bonds and, in some cases, one additional acceptor hydrogen bond. Peroxosolvate 2 can be considered as a novel drug formulation of vitamin B3. 相似文献
177.
M. A. Malenkovskaya M. K. Grachev I. I. Levina E. E. Nifant’ev 《Russian Journal of Organic Chemistry》2013,49(12):1777-1782
New amphiphilic β-cyclodextrin derivatives containing pharmacologically important aromatic and aliphatic monocarboxylic acid fragments at both primary and secondary hydroxy groups were synthesized with the use of palmitic, acetylsalicylic, and 2-(4-isobutylphenyl)propionic acid chlorides. The position of the acyl groups in the carbohydrate fragments of β-cyclodextrin was determined by 13C NMR spectroscopy. 相似文献
178.
179.
A. N. Yarkevich Z. V. Safronova L. N. Petrova A. V. Gabrelyan V. L. Zamoyski V. V. Grigor’ev S. O. Bachurin N. S. Zefirov 《Russian Journal of General Chemistry》2013,83(1):41-45
Bis(dialkylamides) of phosphoryl-substituted α,ω-dicarboxylic acids were synthesized and their biological activity was studied. 相似文献
180.
N. A. Dudina E. V. Antina G. B. Guseva A. I. V’yugin 《Russian Journal of General Chemistry》2013,83(12):2306-2308
We have compared the coordination properties of decamethyl-substituted 3,3′-bis-(dipyrrolylmethenes) (H2L) with different ms-spacers separating the dipyrrolylmethene domains: methylene -CH2-, methoxyphenylmethylene -CH(p-C6H4OMe)-, and trifluoromethylmethylene -CH(CF3)-. The stable binuclear homoligand complexes [M2L2] are formed in reactions of the ligands with Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Hg(II) acetates. In the cases of all H2L ligands the thermodynamic constants of the complex formation reactions increase in the following series: Cu(II) < Cd(II) < Hg(II) < Ni(II) < Co(II) < Zn(II). The change in -CH2- ms-spacer to -CH(p-C6H4OMe)- or -CH(CF3)- results in a decrease in the constant of H2L complex formation by 1–4 orders of magnitude, the cation being the same. The influence of ms-substitution on the stability and luminescence properties of [M2L2] has been discussed. 相似文献