全文获取类型
收费全文 | 186825篇 |
免费 | 30836篇 |
国内免费 | 23431篇 |
专业分类
化学 | 114106篇 |
晶体学 | 2474篇 |
力学 | 11526篇 |
综合类 | 514篇 |
数学 | 23066篇 |
物理学 | 89406篇 |
出版年
2023年 | 1724篇 |
2022年 | 3057篇 |
2021年 | 3330篇 |
2020年 | 3901篇 |
2019年 | 4635篇 |
2018年 | 4883篇 |
2017年 | 5340篇 |
2016年 | 6465篇 |
2015年 | 5552篇 |
2014年 | 6664篇 |
2013年 | 10109篇 |
2012年 | 10692篇 |
2011年 | 12310篇 |
2010年 | 13649篇 |
2009年 | 13923篇 |
2008年 | 8727篇 |
2007年 | 7866篇 |
2006年 | 7117篇 |
2005年 | 6903篇 |
2004年 | 7277篇 |
2003年 | 6174篇 |
2002年 | 6168篇 |
2001年 | 5983篇 |
2000年 | 4562篇 |
1999年 | 4401篇 |
1998年 | 3855篇 |
1997年 | 3446篇 |
1996年 | 3705篇 |
1995年 | 3894篇 |
1994年 | 4002篇 |
1993年 | 3960篇 |
1992年 | 3561篇 |
1991年 | 3244篇 |
1990年 | 2892篇 |
1989年 | 2879篇 |
1988年 | 2727篇 |
1987年 | 2025篇 |
1986年 | 2061篇 |
1985年 | 1763篇 |
1984年 | 1856篇 |
1983年 | 1183篇 |
1982年 | 1656篇 |
1981年 | 1427篇 |
1980年 | 1393篇 |
1979年 | 1296篇 |
1978年 | 1296篇 |
1977年 | 1354篇 |
1976年 | 1855篇 |
1973年 | 1220篇 |
1972年 | 1223篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The effect of an applied magnetic field on an inhomogeneous superconductor is studied and the value of the upper critical magnetic field Hc3 at which superconductivity can nucleate is estimated. In addition, the authors locate the concentration of the order parameter, which depends on the inhomogeneous term a(x). Unlikely to the homogeneous case, the order parameter may concentrate in the interior of the superconducting material, due to the influence of the inhomogeneous term a(x). 相似文献
992.
The notion of a fuzzy retract was introduced by Rodabaugh (1981). The notion of a fuzzy pairwise retract was introduced in 2001. Some weak forms and some strong forms of α-continuous mappings were introduced in 1988 and 1997. The authors extend some of these forms to the L-fuzzy bitopological setting and construct various α-fuzzy pairwise retracts. The concept of weakly induced spaces in the case L = [0,1] was introduced by Martin (1980). Liu and Luo (1987) generalized this notion to the case that L is an arbitrary F-lattice and introduced the notion of induced L-fts. Several results are obtained, especially, for L-valued pairwise stratification spaces. 相似文献
993.
吴臻 《数学物理学报(B辑英文版)》2004,24(1):91-99
The existence and uniqueness results of fully coupled forward-backward stochastic differential equations with stopping time (unbounded) is obtained. One kind of comparison theorem for this kind of equations is also proved. 相似文献
994.
995.
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
996.
997.
Edison Munaf Toyohide Takeuchi Hiroki Haraguchi 《Fresenius' Journal of Analytical Chemistry》1992,342(1-2):154-156
Summary A continuous flow analysis is described for the determination of total mercury by cold vapor atomic absorption spectrometry. Organic mercury compounds such as methylmercury(II) chloride, ethylmercury(II) chloride and phenylmercury(II) chloride were decomposed by potassium peroxodisulphate with addition of ferric chloride as catalytic reagent. The reducing reagent used was tin(II) chloride in sodium hydroxide solution. With 1,000 mg Fe/l added in the decomposition process, we found that methylmercury(II) chloride and ethylmercury(II) chloride gave response signals similar to those of mercury(II) chloride. The proposed method was applied to the analysis of total mercury in waste water.
Permanent address: Department of Chemistry, Faculty of Mathematics and Natural Sciences, Andalas University, Padang, West Sumatra, Indonesia 相似文献
998.
Testing exponentiality against a class of alternatives which includes the RNBUE distributions based on the empirical laplace transform 总被引:1,自引:0,他引:1
S. G. Meintanis Ya. Yu. Nikitin A. V. Tchirina 《Journal of Mathematical Sciences》2007,145(2):4871-4879
A scale-free test for exponentiality is proposed which is consistent within an extended set of models, including, but not
limited to, the “renewal new better than used in expectation” (RNBUE) class of life distributions. The limiting null distribution of the test statistics is derived, and the approximate local
Bahadur efficiency is calculated for several families of alternatives. Finite-sample properties of the proposed procedures
are investigated via simulation. Bibliography: 24 titles.
__________
Translated from Zapiski Nauchnykh Seminarov POMI, Vol. 339, 2006, pp. 63–77. 相似文献
999.
1000.
The dynamical Casimir effect is analyzed in the framework of the S-matrix formulation for a one-dimensional cavity that exhibits contraction at a constant rate over a finite time interval. The exact solution to the problem is presented. It is demonstrated that the efficiency of the creation of pairs nonmonotonically depends on the contraction time. This is due to the fact that the particles are only created at the moments corresponding to the acceleration and stopping of the moving boundary, so that the contributions of these processes on the number of the created particles interfere with each other. The parameters that correspond to the optimal creation of pairs and the stability of a vacuum are presented. The effect of the finiteness of the cavity-boundary acceleration on the results obtained is studied. 相似文献