全文获取类型
收费全文 | 1961篇 |
免费 | 53篇 |
国内免费 | 14篇 |
专业分类
化学 | 1299篇 |
晶体学 | 14篇 |
力学 | 42篇 |
数学 | 257篇 |
物理学 | 416篇 |
出版年
2023年 | 16篇 |
2022年 | 8篇 |
2021年 | 37篇 |
2020年 | 23篇 |
2019年 | 32篇 |
2018年 | 32篇 |
2017年 | 40篇 |
2016年 | 56篇 |
2015年 | 34篇 |
2014年 | 50篇 |
2013年 | 108篇 |
2012年 | 94篇 |
2011年 | 133篇 |
2010年 | 79篇 |
2009年 | 74篇 |
2008年 | 102篇 |
2007年 | 106篇 |
2006年 | 102篇 |
2005年 | 109篇 |
2004年 | 79篇 |
2003年 | 82篇 |
2002年 | 82篇 |
2001年 | 25篇 |
2000年 | 34篇 |
1999年 | 18篇 |
1998年 | 14篇 |
1997年 | 23篇 |
1996年 | 34篇 |
1995年 | 23篇 |
1994年 | 24篇 |
1993年 | 17篇 |
1992年 | 16篇 |
1991年 | 22篇 |
1990年 | 17篇 |
1989年 | 21篇 |
1988年 | 16篇 |
1987年 | 15篇 |
1986年 | 10篇 |
1985年 | 17篇 |
1984年 | 18篇 |
1983年 | 13篇 |
1982年 | 9篇 |
1981年 | 15篇 |
1980年 | 14篇 |
1979年 | 17篇 |
1978年 | 22篇 |
1976年 | 10篇 |
1975年 | 9篇 |
1973年 | 9篇 |
1972年 | 6篇 |
排序方式: 共有2028条查询结果,搜索用时 125 毫秒
1.
This research extends previous work with dynamic models to manage groundwater quality by using the consumptive nitrate use rate instead of the nitrate application rate. The analysis indicates that misspecification results in overestimation of economic benefits, and supra-optimum nitrogen fertilizer application rates and groundwater nitrate stocks at a steady state. 相似文献
2.
Guillermo Palma 《Zeitschrift fur Physik C Particles and Fields》1992,54(4):679-682
In latticeφ 4 close to the critical line, finite size effects can be computed by renormalized loop expansions. In order to do so, the constraint effective potential is computed to two loop order. Using this expression, we are able to extract results for renormalized masses and coupling constants from Multigrid Monte Carlo data of Mack and Meyer for the constraint effective potential close to the critical line, and compare them with the analytical results ofLüscher and Weisz. Perfect agreement is found. 相似文献
3.
We complete our previous(1, 2) demonstration that there is a family of new solutions to the photon and Dirac equations using spatial and temporal circles and four-vector behaviour of the Dirac bispinor. We analyse one solution for a bound state, which is equivalent to the attractive two-body interaction between a charged point particle and a second, which remains at rest. We show this yields energy and angular momentum eigenvalues that are identical to those found by the usual method of solving of the Dirac equation,(4) including fine structure. We complete our previous derivation(2) of QED from a set of rules for the two-body interaction and generalise these. We show that QED may be decomposed into a two-body interaction at every point in spacetime. 相似文献
4.
Guillermo Ferreyra 《Probability Theory and Related Fields》1989,83(3):391-403
Summary A theory of stochastic differential equations driven by predictable processes in Stratonovich sense is developed. These driving processes include a large class of discontinuous semimartingales. The theory of stochastic differential equations driven by continuous semimartingales in Stratonovich sense is extended without involving Lebesgue-Stieltjes integrals as done by Meyer. Moreover, a change of variables formula without extra terms involving the jumps of the processes holds for this theory. Results on approximation of driving processes are preserved.Research partially supported by the Institute for Mathematics and its Applications at the University of Minnesota, Minneapolis, USA; by the AFOSR under contract #AFOSR-85-0315, the ARO under contract #DAAG 29-84-K-0082, and #DAAL 03-86-K-0171. 相似文献
5.
This paper considers a deterministic flow inn-dimensional space, perturbed by a Markov jump process with small variance. Asymptotic expansions are obtained for certain functionals of Feynman—Kac type, in powers of a small parameter representing a noise intensity. The methods are analytical rather than probabilistic.The research of the first author was partly supported by AFOSR under Contract No. 91-0116-0, by ONR under Contract No. N0014-83-K-0542, and by the Institute for Mathematics and Its Applications with funds provided by the NSF and ONR. The second author's research was partly supported by NSF under Contract No. DMS-8702537, and by the Institute for Mathematics and Its Applications with funds provided by the NSF and ONR. 相似文献
6.
In this paper, we study the Hilbert–Samuel function of a generic standard graded K-algebrawhen refined by an (ℓ)-adic filtration, ℓ being a linear form. From this we obtain a structure theorem which describes the stairs of a generic complete intersection for the degree-reverse-lexicographic order. We show what this means for generic standard (or Gröbner) bases for this order; in particular, we consider an “orderly filling up” conjecture, and we propose a strategy for the standard basis algorithm which could be useful in generic-like cases. 相似文献
K[X1,…,Xn]/(g1,…,gm)
7.
Colin J. Thompson Keith M. Briggs Peter Farrell Anthony Fleming Bruce Hocking Kenneth Joyner Vitas Anderson Andrew W. Wood 《Physica A》1995,220(3-4):471-484
A nonlinear Lorenz model describing interactions between charged particles and combined ac-dc electromagnetic fields is studied for various combinations of frequencies, field strengths and relative angle (θ) between the ac and dc magnetic fields. Strong directional effects on the magnitude and location of resonant particle motion are observed when θ is varied and the regular resonance windows in the aligned field (θ = 0) and linear version of the model studied previously by Durney etaal., break up to form irregular and less well pronounced regions of large and small particle displacements when nonlinearities are taken into account. The length of time takne to achieve resonant behaviour also becomes larger and more variable when nonlinearities are present. The possible relevance of these effects to interactions between electromagnetic fields and biological media is briefly discussed. 相似文献
8.
We study extension of operators T: E→ L0([0, 1]), where E is an F–function space and L0([0, 1]) the space of measurable functions with the topology of convergence in measure, to domains larger than E, and we study the properties of such domains. The main tool is the integration of scalar functions with respect to stochastic
measures and the corresponding spaces of integrable functions.
Partially supported by D.G.I. #MTM2006-13000-C03-01 (Spain). 相似文献
9.
We exhibit a probabilistic algorithm which computes a rational point of an absolutely irreducible variety over a finite field defined by a reduced regular sequence. Its time-space complexity is roughly quadratic in the logarithm of the cardinality of the field and a geometric invariant of the input system. This invariant, called the degree, is bounded by the Bézout number of the system. Our algorithm works for fields of any characteristic, but requires the cardinality of the field to be greater than a quantity which is roughly the fourth power of the degree of the input variety.
10.
Novel mixed valence states have been obtained by the treatment of cobaltous ferrocyanides (Co+2FeII) and ferricyanides (Co+2FeIII) in an ozone flow. The CN stretching bands occur at 2085 cm–1 for Co+2FeII and at 2160 cm–1 for Co+2FeIII. After the ozonization process of Co+2FeII, an intense band approximately at 2125 cm–1 is detected. This intermediate band must correspond to a mixed valence state of the type: FeII–CN–Co2+–NC–FeIII Mössbauer spectra recorded in situ during the ozonization of Co+2FeII show the presence of two components: a doublet with isomer shift and quadrupole splitting values close to the cobalti ferricyanide and a very broad line for the mixed valence state. From the Mössbauer and infrared spectra of the aged samples of the Co+2FeII after ozonization, a relaxation process to the initial state of the samples is observed but the mixed valence state is stable. 相似文献