全文获取类型
收费全文 | 26536篇 |
免费 | 151篇 |
国内免费 | 46篇 |
专业分类
化学 | 12035篇 |
晶体学 | 417篇 |
力学 | 964篇 |
综合类 | 11篇 |
数学 | 3682篇 |
物理学 | 9624篇 |
出版年
2023年 | 28篇 |
2022年 | 200篇 |
2021年 | 394篇 |
2020年 | 412篇 |
2019年 | 574篇 |
2018年 | 1065篇 |
2017年 | 1184篇 |
2016年 | 1420篇 |
2015年 | 654篇 |
2014年 | 1197篇 |
2013年 | 1845篇 |
2012年 | 1666篇 |
2011年 | 1756篇 |
2010年 | 1906篇 |
2009年 | 1826篇 |
2008年 | 1837篇 |
2007年 | 1754篇 |
2006年 | 1536篇 |
2005年 | 965篇 |
2004年 | 701篇 |
2003年 | 420篇 |
2002年 | 376篇 |
2001年 | 331篇 |
2000年 | 641篇 |
1999年 | 379篇 |
1998年 | 470篇 |
1997年 | 442篇 |
1996年 | 132篇 |
1995年 | 45篇 |
1994年 | 50篇 |
1993年 | 16篇 |
1992年 | 28篇 |
1991年 | 26篇 |
1990年 | 29篇 |
1989年 | 15篇 |
1988年 | 26篇 |
1987年 | 23篇 |
1986年 | 20篇 |
1985年 | 22篇 |
1984年 | 12篇 |
1983年 | 24篇 |
1982年 | 18篇 |
1981年 | 23篇 |
1980年 | 16篇 |
1979年 | 16篇 |
1978年 | 12篇 |
1977年 | 14篇 |
1974年 | 16篇 |
1972年 | 13篇 |
1968年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
741.
742.
By using a special decomposition of the fundamental solution, we construct a new representation of the Green function of the
Dirichlet problem for the polyharmonic equation in a ball. 相似文献
743.
V. B. Platonov M. N. Rumyantseva T. B. Shatalova A. E. Baranchikov A. M. Gas’kov 《Russian Journal of Applied Chemistry》2018,91(3):447-453
Nanofibers of semiconducting oxides SnO2, ZnO, WO3, produced by the electrospinning method, were tested as sensitive materials for detection of products formed in pyrolysis of polyvinyl chloride in conditions simulating the smoldering of electrically insulating materials upon occurrence of a short-circuit failure in electrical circuits. The method of thermal analysis with mass-spectroscopic determination of gaseous products demonstrated that, in pyrolysis of polyvinyl chloride in the temperature range 200–400°C corresponding to the invisible-smoke stage, the main component of the gas mixture being formed is HCl. It was shown that the materials synthesized can be used to develop gas sensors for early fire warning. 相似文献
744.
N. E. Gordina V. Yu. Prokof’ev T. N. Borisova A. M. Elizarova 《Russian Journal of Applied Chemistry》2018,91(2):180-186
Possibility was examined of synthesizing zeolites granulated without a binder with the use of a preliminary ultrasonic treatment of the suspension at a frequency of 22 kHz from mixtures of sodium metasilicate and aluminum and silicon oxides with various Si: Al ratios. It was found that, after the preliminary treatment, extrusion of grains, and calcination at 650°C, crystalline phases Na6Al4Si4O17, Na8Al4Si4O18, Na2Al2O4, and Na2SiO3 phases are formed in the sample with Si: Al = 1. These phases are precursors for synthesis of NaA and NaP zeolites and sodalite via hydrothermal crystallization in a NaOH solution with concentration of 2 M. Upon a similar treatment of a sample with Si: Al = 2, there are crystalline phases α- and β-Na2Si2O5, from which only NaP zeolite is formed in the course of crystallization. The hydrothermal crystallization in a 6 M alkali solution yields sodalite, irrespective of the Si: Al ratio. It was shown that an ultrasonic treatment gives a gel-like system at Si: Al = 1 and a powdered material at Si: Al = 2, which yields by the end of synthesis samples with cactus-like or wool-like morphology, respectively. 相似文献
745.
A. A. Moiseeva G. V. Gavrilova L. N. Vykhodtseva S. N. Nikolaeva D. P. Krut’ko E. K. Beloglazkina 《Russian Journal of General Chemistry》2014,84(6):1074-1078
The properties of 4-methyl-4-(trichloromethyl)cyclohexa-2,5-dien-1-one which contains the trichloromethyl substituent at a quaternary carbon atom have been studied by cyclic voltammetry, rotating disk electrode voltammetry, and preparative electrolysis. Reductive dehalogenation involves initial two-electron reductive elimination of one of the geminal chlorine atoms followed by consecutive addition of proton, simultaneous elimination of the two residual halogen atoms to form carbene, and rearrangement of cyclohexadienone into the corresponding 4-methylcyclohepta-2,4,6-trien-1-one. 相似文献
746.
Věra Hamplová Alexej Bubnov Corresponding author Miroslav Kašpar Vladimíra Novotná Yveta Lhotáková Milada Glogarová 《Liquid crystals》2013,40(12):1463-1469
New chiral liquid crystalline materials containing a keto group and two lactate units attached to the mesogenic core have been synthesized and studied. All the new compounds show the paraelectric SmA, ferroelectric SmC* and antiferroelectric SmC*A phases each over rather broad temperature ranges. The properties of the phases were characterized by DSC, electro-optical and dielectric studies. The spontaneous polarization, tilt angle, helical pitch, and switching times were determined for the polar phases. 相似文献
747.
748.
A. I. Finaenov A. V. Afonina S. L. Zabud’kov M. V. Medvedeva 《Russian Journal of Applied Chemistry》2013,86(6):853-857
Anodic-corrosion behavior of a number of chromium-nickel steels in a 80% H2SO4 solution was studied in order to replace platinum with less expensive electrodes in electrochemical synthesis of graphite bisulfite and corrosion parameters were determined. 相似文献
749.
N. S. Shaglaeva V. V. Bayandin R. G. Sultangareev G. F. Prozorova T. I. Vakul’skaya S. S. Khutsishvili 《Russian Journal of Applied Chemistry》2013,86(4):611-614
A sulfurized polymer comprising 57.64% of chemically bound sulfur characterizing by paramagnetism with the concentration of paramagnetic centers 2 × 1019 spins g?1 and g-factor 2.0043 was resulted n the treatment of industrial polyvinyl chloride by elemental sulfur. 相似文献
750.
N. I. Selivanov L. G. Samsonova T. A. Solodova T. N. Kopylova E. N. Tel’minov 《Optics and Spectroscopy》2013,114(3):373-378
The spectral and luminescent properties of acridine in SiO2 films synthesized by the sol-gel method using acid hydrolysis of tetraethoxysilane are studied. It is shown that acridine in films exists in protonated form. Ammonia-gas-sensing properties of films doped with acridine are studied by the fluorescence response (decrease in the intensity) of the protonated form. The possibility of multiple use of a sample without a noticeable decrease in its sensitivity is demonstrated. It is shown that the fluorescence response to a maximal permissible concentration of ammonia in the gas mixture with argon is 6–8%. 相似文献