全文获取类型
收费全文 | 677篇 |
免费 | 6篇 |
专业分类
化学 | 491篇 |
晶体学 | 12篇 |
力学 | 26篇 |
数学 | 39篇 |
物理学 | 115篇 |
出版年
2021年 | 7篇 |
2018年 | 7篇 |
2016年 | 7篇 |
2013年 | 29篇 |
2012年 | 25篇 |
2011年 | 25篇 |
2010年 | 13篇 |
2009年 | 13篇 |
2008年 | 25篇 |
2007年 | 33篇 |
2006年 | 20篇 |
2005年 | 19篇 |
2004年 | 18篇 |
2003年 | 18篇 |
2002年 | 28篇 |
2001年 | 11篇 |
2000年 | 16篇 |
1999年 | 12篇 |
1998年 | 8篇 |
1997年 | 7篇 |
1996年 | 9篇 |
1995年 | 9篇 |
1994年 | 12篇 |
1993年 | 15篇 |
1992年 | 22篇 |
1991年 | 13篇 |
1990年 | 9篇 |
1988年 | 14篇 |
1987年 | 6篇 |
1986年 | 10篇 |
1985年 | 8篇 |
1984年 | 10篇 |
1983年 | 7篇 |
1982年 | 7篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1976年 | 10篇 |
1975年 | 9篇 |
1974年 | 12篇 |
1973年 | 8篇 |
1972年 | 10篇 |
1971年 | 12篇 |
1970年 | 6篇 |
1969年 | 5篇 |
1960年 | 5篇 |
1958年 | 9篇 |
1954年 | 5篇 |
排序方式: 共有683条查询结果,搜索用时 15 毫秒
141.
142.
David Reynolds Anthony J. Mulholland Jagannathan Gomatam 《Journal of mathematical chemistry》1997,22(1):25-37
We present a new class of techniques for the solution of the chemical and phase equilibria problem for reacting species in a closed system. The minimisation of the Gibbs free energy for all the species in the system is conducted using the technique of simulated annealing (SA). The SA objective function incorporates non‐ideal equations of state. This new approach is demonstrably able to solve multi‐species and multi‐phase LTCE problems in ideal‐gas solutions, ideal solutions and mixtures of ideal and non‐ideal solutions. 相似文献
143.
This paper describes the acceleration measurements and data analysis aspect of a comprehensive multidisciplined field study of several hundred chipper and grinder workers using pneumatic hand-held tools. Engineering testing of a sampling of these tools indicated that for a frequency range of 6·3 Hz to 1000 Hz, overall acceleration levels between 2000 m/s2 and 24 000 m/s2 were measured on the chisels and levels between 37 m/s2 and 350 m/s2 were measured on the handles of chipping hammers. Hand grinder acceleration levels ranged from 6 m/s2 to 21 m/s2. 相似文献
144.
A real-world, multi-stage, industrial scheduling problem is presented. An algorithm is described that converts a sequence of jobs into a complete schedule. Backward simulation is used to determine minimum storage requirements when scheduling each job, and to calculate the minimum amount of delay required. Combining this algorithm with a metaheuristic, such as simulated annealing, results in an effective algorithm for schedule optimization. 相似文献
145.
A.M. Reynolds 《Fluid Dynamics Research》1998,22(6):317-328
Properties of the mean-streamlines of a turbulent wake flow behind a low-rise building have been investigated in numerical simulations. For some near wind directions, the solutions to the equations for the mean-streamlines in the recirculating region of flow are found to be chaotic. This is shown to be analogous to the occurrence of chaotic advection in laminar flows and consistent with the current understanding of chaotic dynamics in Hamiltonian systems. The transitions between regular and chaotic solutions for the mean-streamlines are found to occur abruptly over incremental changes, Δθ<2°, in the mean wind direction, θ. These transitions are shown to be accompanied by abrupt changes in the characteristics of plumes formed from tracer-particles undergoing turbulent dispersion. Small fluctuations in the mean wind direction at the transition between regular and chaotic solutions for the mean-streamlines are predicted to result in strongly intermittent turbulent dispersion. 相似文献
146.
147.
An X-ray scattering study is presented of the lamellar/nematic/isotropic sequence in the lyotropic system DACI/H2O/NH4Cl. The whole reciprocal space of monocrystalline samples oriented in magnetic fields are reconstructed from their two dimensional sections on photographic films. Intense diffuse scatterings are observed in the lamellar phase, around and away from the Bragg spots. Their evolution close to the lamellar/nematic transition reveals the presence of intense structural fluctuations. They take place over temperature ranges which are significantly greater than those associated with the smectic/nematic transitions in thermotropic liquid crystals. A similar situation is observed in the isotropic phase in the vicinity of the nematic/isotropic transition. 相似文献
148.
149.
Colin Thomson Christopher A. Reynolds 《International journal of quantum chemistry》1986,30(6):751-762
The results of ab initio calculations using a 4–21G basis set are reported for various possible metabolites of N,N'-dimethylnitrosamine. The relevance of these results to the nature of the alkylating agent is discussed. Although the calculations widen the range of possible alkylating agents that need to be considered, the diazonium ion appears to be the most likely candidate. 相似文献
150.
This paper presents a method for calculating power transmitted to the hands of operators who use vibrating hand tools. Results that relate to a comprehensive multidisciplined NIOSH field study of several hundred chipper and grinder workers who used pneumatic hand tools are presented. The results of this study indicated that the power in the frequency range of 6·3 Hz to 1000 Hz transmitted to the hand ranged from 1·08 × 103 to 7·23 × 103 J/s for the chisel and from 8·52 × 10?1 to 1·57 × 102 J/s for the handle of chipping hammers. For pneumatic grinders the power transmitted to the hands of the tool operators was in the range of 6·58 × 10?3 to 2·35 × 10?3 J/s over the same frequency range. 相似文献