全文获取类型
收费全文 | 313922篇 |
免费 | 1568篇 |
国内免费 | 738篇 |
专业分类
化学 | 143216篇 |
晶体学 | 4297篇 |
力学 | 18704篇 |
综合类 | 7篇 |
数学 | 59208篇 |
物理学 | 90796篇 |
出版年
2020年 | 2488篇 |
2019年 | 3014篇 |
2018年 | 14613篇 |
2017年 | 14590篇 |
2016年 | 11469篇 |
2015年 | 3407篇 |
2014年 | 5038篇 |
2013年 | 9740篇 |
2012年 | 11311篇 |
2011年 | 19215篇 |
2010年 | 12891篇 |
2009年 | 13451篇 |
2008年 | 14988篇 |
2007年 | 16957篇 |
2006年 | 7899篇 |
2005年 | 8018篇 |
2004年 | 7943篇 |
2003年 | 7844篇 |
2002年 | 7112篇 |
2001年 | 6951篇 |
2000年 | 5248篇 |
1999年 | 3949篇 |
1998年 | 3659篇 |
1997年 | 3398篇 |
1996年 | 3155篇 |
1995年 | 2813篇 |
1994年 | 2700篇 |
1993年 | 2778篇 |
1992年 | 2830篇 |
1991年 | 3164篇 |
1990年 | 3040篇 |
1989年 | 3130篇 |
1988年 | 2930篇 |
1987年 | 2902篇 |
1986年 | 2745篇 |
1985年 | 3374篇 |
1984年 | 3460篇 |
1983年 | 2966篇 |
1982年 | 3062篇 |
1981年 | 2911篇 |
1980年 | 2684篇 |
1979年 | 3027篇 |
1978年 | 3280篇 |
1977年 | 3377篇 |
1976年 | 3369篇 |
1975年 | 3152篇 |
1974年 | 3112篇 |
1973年 | 3263篇 |
1972年 | 2604篇 |
1971年 | 2382篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
We prove that the sufficient conditions for the asymptotic stability of impulsive systems obtained by Gurgula and Perestyuk are also necessary conditions. 相似文献
92.
P L Melgarejo M Ternero I Gracia 《International journal of environmental analytical chemistry》1986,24(4):283-295
A study of the atmospheric pollution by suspended particulate lead in the city of Seville, Spain, was carried out during the period between March 1983 and February 1984. The results obtained from seven sampling stations allowed us to study the site to site variations; there are two locations with average annual concentrations higher than 2 micrograms X m-3. In one station, the meteorological and traffic effects and relationship with other traffic-related pollutants, were investigated. The regression analyses performed on the average monthly data have shown an inverse correlation with wind speed and temperature and a direct correlation with carbon monoxide and smoke concentrations, but no significant correlation was found with the lead deposition levels. 相似文献
93.
94.
I. L. Bataronov A. M. Roshchupkin 《Journal of Applied Mechanics and Technical Physics》1991,32(2):259-265
Translated from Zhurnal Prikladnoi Mekhaniki i Tekhnicheskoi Fiziki, No. 2, pp. 127–134, March–April, 1991. 相似文献
95.
96.
Nikulin S. S. Akatova I. N. Kondrat'eva N. A. 《Russian Journal of Applied Chemistry》2003,76(4):652-655
The influence of the charge of a metal cation and the nature of a coagulant on the recovery of butadiene-styrene rubber and properties of rubber stocks and vulcanizates was examined. 相似文献
97.
Translated from Matematicheskie Zametki, Vol. 49, No. 5, pp. 37–44, May, 1991. 相似文献
98.
Passive methods of remote analysis of waste gases of industrial enterprises and aircrafts engines and gases ejected in eruptions of volcanos, in fires, and in other processes disturbing the atmosphere are now of limited utility because of the lack of well-developed mathematical techniques for solving the inverse problems of gas analysis. However, the advantage of these methods is obvious, since the equipment is limited to a receiving device and the gas medium serves as a radiator. At the same time, in modern techniques, the interpretation of measurements of emissivities of gases is performed using a phenomenological approach such that experimental data on radiation characteristics of various objects are approximated by simple polynomial relations whose coefficients are determined by minimization methods. This approach does not allow one to investigate the mechanism of the processes occurring in a radiating medium and gives no way of solving the inverse problem of monitoring the composition and thermodynamic parameters of a medium which disturbs the atmosphere by thermal effects. In elaborating theoretical methods of gas analysis, the elaboration of the direct problem of calculation of radiating characteristics of gases is of importance, since it is not clear how the emissivity of a gas medium depends on its thermodynamic parameters. This paper is devoted to the above problem. Here, the error is estimated that arises in modeling a nonuniform gas medium with an actual temperature distribution, which linearly depends on coordinate, by a uniform gas layer. It is shown that the difference between the radiation intensities calculated for uniform and nonuniform media can be significant in the practically important case where the recording device is in a zone of normal temperatures. This implies that the error of reconstruction of the spectroscopic and molecular parameters of gaseous compounds from high-temperature measurements of the radiating and absorbing characteristics should take into account the thermodynamic nonuniformity of the medium. 相似文献
99.
Barannikov V. P. Guseinov S. S. V'ugin A. I. 《Russian Journal of Coordination Chemistry》2002,28(3):153-162
A review of the experimental and theoretical studies of the crown ether complexes with polar molecules in their crystals, solutions, and in a gas phase is given. The type of the molecular bonds in the complexes, their stoichiometry, and the change in the macrocycle conformation during complex formation are considered, as well as the effect of the macrocycle structure and the nature of the medium on the efficiency of the molecular bonding. New data are given on the enthalpies of transfer of the crown ethers from tetrachloromethane into solvents capable of forming hydrogen bonds. The enthalpies of specific interactions of macrocycles with the molecules of the solvents in the medium of the same solvents are characterized. The conformations of the crown ethers in the media under study are discussed. 相似文献
100.
M. I. Ivanchov 《Ukrainian Mathematical Journal》2003,55(7):1086-1098
We establish conditions for the existence and uniqueness of a solution of the inverse problem for a one-dimensional heat equation with unknown time-dependent leading coefficient in the case where a part of the boundary of the domain is unknown. 相似文献