全文获取类型
收费全文 | 148789篇 |
免费 | 1507篇 |
国内免费 | 401篇 |
专业分类
化学 | 81716篇 |
晶体学 | 2433篇 |
力学 | 6092篇 |
综合类 | 3篇 |
数学 | 13630篇 |
物理学 | 46823篇 |
出版年
2021年 | 1051篇 |
2020年 | 1206篇 |
2019年 | 1276篇 |
2018年 | 1653篇 |
2017年 | 1698篇 |
2016年 | 2574篇 |
2015年 | 1604篇 |
2014年 | 2391篇 |
2013年 | 6134篇 |
2012年 | 4938篇 |
2011年 | 6031篇 |
2010年 | 4236篇 |
2009年 | 4268篇 |
2008年 | 5819篇 |
2007年 | 5627篇 |
2006年 | 5503篇 |
2005年 | 5051篇 |
2004年 | 4559篇 |
2003年 | 4203篇 |
2002年 | 4091篇 |
2001年 | 5588篇 |
2000年 | 4024篇 |
1999年 | 3097篇 |
1998年 | 2129篇 |
1997年 | 2223篇 |
1996年 | 2100篇 |
1995年 | 1948篇 |
1994年 | 1938篇 |
1993年 | 1752篇 |
1992年 | 2255篇 |
1991年 | 2321篇 |
1990年 | 2146篇 |
1989年 | 2112篇 |
1988年 | 2094篇 |
1987年 | 2102篇 |
1986年 | 1928篇 |
1985年 | 2386篇 |
1984年 | 2415篇 |
1983年 | 1919篇 |
1982年 | 1929篇 |
1981年 | 1767篇 |
1980年 | 1750篇 |
1979年 | 2046篇 |
1978年 | 2112篇 |
1977年 | 2059篇 |
1976年 | 1991篇 |
1975年 | 1869篇 |
1974年 | 1862篇 |
1973年 | 1883篇 |
1972年 | 1241篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
961.
V. T. Astrelin A. V. Burdakov V. S. Koidan K. I. Mekler P. I. Mel’nikov V. V. Postupaev M. A. Shcheglov 《Journal of Experimental and Theoretical Physics》1998,86(3):489-500
This paper presents the results of experiments on two-stage heating of a dense plasma by a relativistic electron beam in the
GOL-3 facility. A dense plasma with a length of about a meter and a hydrogen density up to 1017 cm−3 was created in the main plasma, whose density was 1015 cm−3. In the process of interacting with the plasma, the electron beam (1 MeV, 40 kA, 4 μs) imparts its energy to the electrons of the main plasma through collective effects. The heated electrons, as they disperse
along the magnetic field lines, in turn reach the region of dense plasma and impart their energy to it by pairwise collisions.
Estimates based on experimental data are given for the parameters of the flux of hot plasma electrons, the energy released
in the dense plasma, and the energy balance of the beam-plasma system. The paper discusses the dynamics of the plasma, which
is inhomogeneous in density and temperature, including the appearance of pressure waves.
Zh. éksp. Teor. Fiz. 113, 897–917 (March 1998) 相似文献
962.
A nonlinear model is developed for the photoresponse of a bolometric structure taking into account the temperature dependences
of the thermal constants of the YBaCuO/MgO structure and its boundary thermal resistance. The model also allows for the specific
form of the currentvoltage characteristic of YBaCuO and the heat release from the transport current flow. A comparison between
the experimental data and the model showed that the nonlinear thermal model accurately describes the temporal characteristics
of the photoresponse.
Fiz. Tverd. Tela (St. Petersburg) 40, 191–194 (February 1998) 相似文献
963.
The problems of choosing the optimal mathematical model for a prescribed range of parameters of a pulsed action are discussed.
A preliminary analysis performed by similarity and dimensional-analysis methods using interpolation equations of state of
the matter shows that the complete system of equations of gasdynamics can be simplified by dropping individual terms which
are not important in a given parameter range. The results of an analysis are presented in the form of nomograms, which also
make it possible to identify the class of fast and energy-intensive gasdynamic processes more accurately than at an intuitive
level.
Zh. Tekh. Fiz. 68, 44–47 (May 1998) 相似文献
964.
4-Aminophthalimide Derivatives as Environment-Sensitive Probes 总被引:2,自引:0,他引:2
The potential of 4-aminophthalimide (AP) and its derivatives as fluorescence probes for organized media is highlighted. The fluorescence response of AP, as measured from the position of the fluorescence maximum, fluorescence intensity and lifetime, is highly sensitive to the polarity of the medium. The sensitivity of the fluorescence parameters is further enhanced due to the involvement of the emitting intramolecular charge transfer state in hydrogen bonding interaction with the solvent molecules containing hydroxyl groups. It is shown that the microheterogeneous environments of organized media such as cyclodextrins and micelles can be very conveniently monitored using this probe. The results of the investigations carried out employing AP and its derivatives as fluorescence probe molecules in these media clearly suggest that a combination of the hydrophobic interaction with the host media and hydrogen bonding interaction with the solvent molecules determine the location of the fluorophore, which in all cases is found to be the interfacial region separating the nonpolar core of the micelle or the cyclodextrin cavity and the polar aqueous environment. Guidelines for the design of probes of this class of systems for the nonpolar core region of the micelles are provided and possible ways to increase the sensitivity of the fluorescence response of the systems are suggested. 相似文献
965.
G. V. Loseva S. G. Ovchinnikov É. K. Yakubailik N. I. Kiselev T. A. Gaidalova 《Physics of the Solid State》1998,40(10):1715-1717
A study has been made of the FexV1−x
S solid solutions with 0<x<0.5. For the compounds with x>0.1, x-ray diffraction analysis discloses a V5S8 superstructure. Samples with x>0.1 are magnetically ordered at room temperature. The concentration dependences of resistivity and magnetization exhibit
sharp peaks for x=0.1 and x=0.2, respectively. The main features of the structure and electronic properties have been qualitatively explained in terms
of the three-band exciton-insulator model, and the maxima in resistivity and magnetization are assigned to the formation of
localized magnetic moments with S=1, which become delocalized with increasing x.
Fiz. Tverd. Tela (St. Petersburg) 40, 1890–1893 (October 1998) 相似文献
966.
967.
The solvent extraction of cobalt(II), nickel(II) and copper(II) using 2,4-pent-dione (Hacac) and 4-phenyl-2, 4-but-dione (Hbzac)
is carried out by varying the reagent concentration and pH of the aqueous phase. Each of these metals is quantitatively separated
(≈ 98%) from their binary mixtures with monovalent (Ag), divalent (Mn, Zn, Cd, Hg, Mg, Sn, Pb) and trivalent (Cr, Fe) metals.
The extraction constants are calculated from the metal distribution data using linear regression analysis. The extracted species
is MA2 in each case. A most significant result is separation of copper(II) from iron(III) which otherwise interferes when extracted
from the acidic medium. 相似文献
968.
969.
Chaos in duopoly pricing 总被引:5,自引:0,他引:5
T. Puu 《Chaos, solitons, and fractals》1991,1(6):573-581
The dynamics of two competing firms in a market is studied in terms of Cournot's duopoly theory. Assuming iso-elastic demand and constant unit production costs the iterative mapping for the outputs of the two firms ensues. The two constants are the unit production costs. The fixed point, the Cournot equilibrium, has earlier been assumed to be the only interesting feature of this model. It is, however, shown that the model can produce persistent motion, periodic or chaotic. 相似文献
970.
T. P. Bochkareva B. V. Passet K. R. Popov N. V. Platonova T. I. Koval'chuk 《Chemistry of Heterocyclic Compounds》1987,23(10):1084-1089
A novel method has been developed for the synthesis of sulfonic acids of five-membered heterocycles containing two heteroatoms, with a solution of sulfur trioxide in 1,2-dichloroethane. High yields of the required products are obtained, under conditions which are mild in comparison with those used in earlier methods. The mechanism of sulfonation is discussed, and some azole·SO3 complexes have been obtained and described.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1353–1359, October, 1987. 相似文献