全文获取类型
收费全文 | 915篇 |
免费 | 32篇 |
国内免费 | 3篇 |
专业分类
化学 | 640篇 |
晶体学 | 15篇 |
力学 | 23篇 |
数学 | 70篇 |
物理学 | 202篇 |
出版年
2024年 | 3篇 |
2023年 | 8篇 |
2022年 | 13篇 |
2021年 | 31篇 |
2020年 | 32篇 |
2019年 | 23篇 |
2018年 | 28篇 |
2017年 | 28篇 |
2016年 | 34篇 |
2015年 | 28篇 |
2014年 | 44篇 |
2013年 | 69篇 |
2012年 | 96篇 |
2011年 | 57篇 |
2010年 | 59篇 |
2009年 | 44篇 |
2008年 | 67篇 |
2007年 | 50篇 |
2006年 | 37篇 |
2005年 | 44篇 |
2004年 | 31篇 |
2003年 | 19篇 |
2002年 | 16篇 |
2001年 | 12篇 |
2000年 | 11篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 6篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1972年 | 2篇 |
1970年 | 1篇 |
1965年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有950条查询结果,搜索用时 29 毫秒
101.
In this paper, we show that self-similarity with respect to the existence of a (purely radial) homothetic Killing vector field for spherically symmetric spacetimes implies the separability of the spacetime metric in terms of the co-moving coordinates (and vice versa) and that the metric is, uniquely, the one recently reported in (Class. Quantam Grav. 18: 2147–2162; 2001). This spacetime, in general, has non-vanishing energy flux and shear. An interesting feature of this spacetime, in contrast to other self-similar spherically symmetric spacetimes (not reducible to our form) is that it has an arbitrary radial distribution of matter. 相似文献
102.
CaS phosphor activated with Dy ions is prepared by the solid-state diffusion method. The phosphor is characterized by x-ray powder diffraction, thermogravimetric analysis and photoiuminescence. Defect centres formed in CaS:Dy are studied using the technique of electron spin resonance. The thermoluminescence glow curve shows peaks at around 117℃ and 345℃. Irradiated CaS:Dy exhibits ESR lines due to defect centres. The thermal annealing behaviour of one of the defect centres appears to correlate with the TL peaks at 117℃ and 345℃. This centre is characterized by an isotropic g-value of 2.0035 and is assigned to an F^+ centre. 相似文献
103.
U. V. Manoj Jatinder N. D Gupta Sushil K. Gupta Chelliah Sriskandarajah 《Annals of Operations Research》2008,161(1):53-86
We study the benefits of coordinated decision making in a supply chain consisting of a manufacturer, a distributor, and several
retailers. The distributor bundles finished goods produced by the manufacturer and delivers them to the retailers to meet
their demands. The distributor is responsible for managing finished goods inventory. An optimal production schedule of the
manufacturer, if imposed on the distributor, may result in an increased inventory holding cost for the distributor. On the
other hand, an optimal distribution schedule of the distributor, if imposed on the manufacturer, may result in an increased
production cost for the manufacturer. In this paper we develop mathematical models for individual optimization goals of the
two partners and compare the results of these models with the results obtained for a joint optimization model at the system
level. We investigate the computational complexities of these scheduling problems. The experimental results indicate that
substantial cost savings can be achieved at the system level by joint optimization. We also study conflict and cooperation
issues in the supply chain. The cost of conflict of a supply chain partner is a measure of the amount by which the unconstrained
optimal cost increases when a decision is to be made under the scheduling constraint imposed by the other partner. We quantify
these conflicts and show that the cost of conflicts are significant. We also show that a cooperative decision will generate
a positive surplus in the system which can be shared by the two partners to make cooperation and coordination strategy more
attractive. 相似文献
104.
Functionalization of 4-methyl group in cycloartane-type triterpenoids has been accomplished utilizing, in the key step, photolytic decomposition of an hypoiodite derived from a 3β-hydroxymethyl-4,4-dimethyl precursor. The synthesis of cycloeucalanone from cyclolaudanone is reported. 相似文献
105.
A.S. Wagh 《Physica A》1975,81(3):369-390
The transport processes can be discussed either by kinetic equation method or by correlation function method. Using the former, linear transport equations are developed for the study of dynamic conductivity of a quantum imperfect gas employing a resolution of BBGKY hierarchy using Green functions. From this transport equation a modified form of Kubo (correlation function) formula is obtained to show the equivalence between the two methods. This equivalence may be used for the justification of the concept of adiabatic switching of the field. The simple formula derived, gives the conductivity in terms of one-particle Green function, unlike the usual discussions which express it in higher order Green functions. 相似文献
106.
A linear σ-model is used to describe the N and Δ as three quarks interacting via σ and π mesons. The effects of confinement are neglected. Although we solve the mean field equations for a hedgehog baryon we can calculate observables for states of good spin and isospin. These are in resonable agreement with experiment. 相似文献
107.
The bi-variational SCF scheme for dilated closed shell atomic hamiltonians is studied and discussed. Applications to the Be atom are presented. 相似文献
108.
The diagonal 2ph-TDA and quasiparticle decouplings of the dilated electron propagator (based on an underlying bi-variational
SCF) are utilized to calculate energy and width of the Be+(1s
−1)2S Auger resonance for the first time. Comparison with experimental and other theoretical results reveals that the renormalized
infinite order diagonal 2ph-TDA decoupling seems to offer a less balanced approach to the treatment of resonances than the
second-order decoupling. The diagonal quasiparticle approximation to the self energy is seen to offer an effective and economic
alternative to the non-diagonal propagator calculations. 相似文献
109.
110.
Manoj K. Rajpoot Tapan K. Sengupta Pravir K. Dutt 《Journal of computational physics》2010,229(10):3623-3651
In this paper we examine the constrained optimization of explicit Runge–Kutta (RK) schemes coupled with central spatial discretization schemes to solve the one-dimensional convection equation. The constraints are defined with respect to the correct error propagation equation which goes beyond the traditional von Neumann analysis developed in Sengupta et al. [T.K. Sengupta, A. Dipankar, P. Sagaut, Error dynamics: beyond von Neumann analysis, J. Comput. Phys. 226 (2007) 1211–1218]. The efficiency of these optimal schemes is demonstrated for the one-dimensional convection problem and also by solving the Navier–Stokes equations for a two-dimensional lid-driven cavity (LDC) problem. For the LDC problem, results for Re=1000 are compared with results using spectral methods in Botella and Peyret [O. Botella, R. Peyret, Benchmark spectral results on the lid-driven cavity flow, Comput. Fluids 27 (1998) 421–433] to calibrate the method in solving the steady state problem. We also report the results of the same flow at Re=10,000 and compare them with some recent results to establish the correctness and accuracy of the scheme for solving unsteady flow problems. Finally, we also compare our results for a wave-packet propagation problem with another method developed for computational aeroacoustics. 相似文献