全文获取类型
收费全文 | 1046篇 |
免费 | 44篇 |
国内免费 | 86篇 |
专业分类
化学 | 201篇 |
晶体学 | 1篇 |
力学 | 49篇 |
综合类 | 7篇 |
数学 | 688篇 |
物理学 | 230篇 |
出版年
2024年 | 6篇 |
2023年 | 9篇 |
2022年 | 9篇 |
2021年 | 13篇 |
2020年 | 8篇 |
2019年 | 11篇 |
2018年 | 15篇 |
2017年 | 8篇 |
2016年 | 22篇 |
2015年 | 19篇 |
2014年 | 17篇 |
2013年 | 166篇 |
2012年 | 61篇 |
2011年 | 62篇 |
2010年 | 39篇 |
2009年 | 62篇 |
2008年 | 53篇 |
2007年 | 45篇 |
2006年 | 47篇 |
2005年 | 48篇 |
2004年 | 29篇 |
2003年 | 33篇 |
2002年 | 43篇 |
2001年 | 43篇 |
2000年 | 33篇 |
1999年 | 37篇 |
1998年 | 22篇 |
1997年 | 41篇 |
1996年 | 29篇 |
1995年 | 32篇 |
1994年 | 30篇 |
1993年 | 17篇 |
1992年 | 18篇 |
1991年 | 8篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 7篇 |
1986年 | 1篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有1176条查询结果,搜索用时 0 毫秒
61.
Mostafa Khorramizadeh Nezam Mahdavi-Amiri 《4OR: A Quarterly Journal of Operations Research》2009,7(2):145-167
We present a new class of integer extended ABS algorithms for solving linear Diophantine systems. The proposed class contains the integer ABS (the so-called EMAS and our proposed MEMAS) algorithms and the generalized Rosser’s algorithm as its members. After an application of each member of the class a particular
solution of the system and an integer basis for the null space of the coefficient matrix are at hand. We show that effective
algorithms exist within this class by appropriately setting the parameters of the members of the new class to control the
growth of intermediate results. Finally, we propose two effective heuristic rules for selecting certain parameters in the
new class of integer extended ABS algorithms.
相似文献
62.
The aim of the present paper is to characterize prime numbers of the form n = x
2 + (x + 1)2 and to obtain certain proper divisors of composite numbers of the same form, i.e. divisors d of n such that 1 < d < n.
相似文献
63.
关于不定方程组x-1=3py^2,x^2+x+1=3z^2 总被引:2,自引:0,他引:2
设P为素数,利用同余及高次丢番图方程的一些结果证明了不定方程组x-1=3py^2,x^2+x+1=3z^2仅有正整数解(p,x,y,z)=(7,22,1,13)。 相似文献
64.
Andrej Dujella 《The Ramanujan Journal》2008,15(1):37-46
A set of m positive integers is called a Diophantine m-tuple if the product of any two of them is one less than a perfect square. It is known that there does not exist a Diophantine
sextuple and that there are only finitely many Diophantine quintuples. On the other hand, there are infinitely many Diophantine
m-tuples for m=2, 3 and 4.
In this paper, we derive asymptotic estimates for the number of Diophantine pairs, triples and quadruples with elements less
than given positive integer N.
The author was supported by the Ministry of Science and Technology, Republic of Croatia, grants 0037110 and 037-0372781-2821. 相似文献
65.
The parameter mixing rules of the Soave–Redlich–Kwong (SRK) equation of state are rewritten as Huron–Vidal mixing rules, where infinite-pressure activity coefficients are predicted by group contributions. Alkanes are treated as composed by one group type and aromatics by two types, aliphatic and aromatic. Hydrocarbon mixtures can be treated using one universal interaction parameter. Light compounds like methane, N2, CO2, H2S, etc. are treated as separate groups; each one requires a pair of parameters for its interactions with aliphatic and aromatic groups. Group interaction parameters were determined from experimental VLE data. From them, binary interaction constants of the classical quadratic mixing rules can directly be derived. 相似文献
66.
In spite of its simplicity and a well-defined theoretical basis, the Flory–Guggenheim approach is conventionally regarded as inapplicable to off-lattice system since the insertion probability of the approach does not account for the excluded region, existing in the off-lattice system. In this work, we propose the insertion probability accounting for the excluded region of off-lattice fluids and derive a new version of equation of state (EOS) for hard-sphere chains basing on the Flory–Guggenheim approach. To investigate the behavior of the excluded regions, a Monte Carlo sampling was performed for hard disks and the various excluded regions were found to have different density dependence. On the basis of the simulation result, we formulated the insertion probability for hard-sphere and that of hard-sphere chain which accounts for the effect of chain-connectivity on the monomer insertion. The proposed insertion probability was found to correctly predict the simulation data for monomer and correctly correlate the simulation data for chain fluids. The resulting EOS was found to meet closed-packed limit and predict the simulation data of compressibility factor for monomer and chains with a reasonable degree of accuracy. When compared with other off-lattice based EOS, it shows a comparable or better result. For second virial coefficient of chain molecules, the model was found to reasonably predict the simulation data. 相似文献
67.
Lin Zhang Ying-Hua LiYu-Ying Yu Xue-Mei LiYun Ma Cheng-Gang GuCheng-Da Dai Ling-Cang Cai 《Physica B: Condensed Matter》2011,406(22):4163-4169
The mean-field potential (MFP) approach is an efficient way to evaluate the free energy contribution of ion motions for both solid and liquid states. In this paper the MFP is generally constructed with a volume-dependent term and a shape function. The former is derived in accordance with quasi-harmonic approximation. The latter is given semi-empirically. Application to multiphase equations of state for β-, γ- and liquid-tin has been examined. The theoretical phase diagram and thermodynamic properties of isotherm, thermal expansion, heat capacity, Hugoniot states as well as phase transitions are all in excellent agreement with experiments. 相似文献
68.
We employ an isospin dependent version of the QMD transport model to study the influence of the isospin dependent part of the nuclear matter equation of state and in-medium nucleon–nucleon cross-sections on the dynamics of heavy-ion collisions at intermediate energies. We find that the extraction of useful information on the isospin-dependent part of the equation of state of nuclear matter from proton or neutron elliptic flows is obstructed by their sensitivity to model parameters and in-medium values of nucleon–nucleon cross-sections. Opposite to that, neutron–proton elliptic flow difference shows little dependence on those variables while its dependence on the isospin asymmetric EoS is enhanced, making it more suitable for a model independent constraining of the high-density behaviour of asy-EoS. Comparison with existing experimental FOPI-LAND neutron–hydrogen data can be used to set an upper limit to the softness of asy-EoS. Successful constraining of the asy-EoS via neutron–proton elliptic flow difference will require experimental data of higher accuracy than presently available. 相似文献
69.
We calculate the strange star properties in the framework of the Field Correlator Method. We find that for gluon condensate values G2 in the range 0.006–0.007 GeV4, which give a critical temperature Tc∼170 MeV at μc=0, the sequences of strange stars are compatible with some of the semi-empirical mass–radius relations and data obtained from astrophysical observations. 相似文献
70.
研究了Kenichiro提出的轮换对称形式的丢番图方程,即方程ab bc ca=ya+b+c3的求解问题,利用素数整除的一些性质,证明了该方程仅有平凡解a=b=c以及非平凡解(a,b,c)=(k,k,4k),(k,4k,k),(4k,k,k)(k∈N),从而完全解决了这个方程. 相似文献