全文获取类型
收费全文 | 1728篇 |
免费 | 65篇 |
国内免费 | 5篇 |
专业分类
化学 | 1151篇 |
晶体学 | 18篇 |
力学 | 67篇 |
数学 | 186篇 |
物理学 | 376篇 |
出版年
2023年 | 9篇 |
2022年 | 25篇 |
2021年 | 45篇 |
2020年 | 26篇 |
2019年 | 41篇 |
2018年 | 56篇 |
2017年 | 21篇 |
2016年 | 55篇 |
2015年 | 52篇 |
2014年 | 59篇 |
2013年 | 116篇 |
2012年 | 125篇 |
2011年 | 129篇 |
2010年 | 93篇 |
2009年 | 69篇 |
2008年 | 106篇 |
2007年 | 127篇 |
2006年 | 96篇 |
2005年 | 81篇 |
2004年 | 57篇 |
2003年 | 59篇 |
2002年 | 52篇 |
2001年 | 21篇 |
2000年 | 18篇 |
1999年 | 18篇 |
1998年 | 16篇 |
1997年 | 21篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 9篇 |
1992年 | 5篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 12篇 |
1984年 | 10篇 |
1983年 | 13篇 |
1982年 | 8篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1978年 | 5篇 |
1977年 | 11篇 |
1976年 | 4篇 |
1975年 | 4篇 |
1973年 | 8篇 |
1972年 | 4篇 |
排序方式: 共有1798条查询结果,搜索用时 31 毫秒
1.
S. P. Mukherjee A. K. Chattopadhyay 《The Journal of the Operational Research Society》1989,40(5):489-494
Consider an organization with several categories of staff, each having a specified number of members. The age of entry into service and the age of retirement are both specified. Withdrawals occur at time-independent rates. Under this set-up, the authors have computed the maximum ages at which promotions should take place, assuming that the staff members continuing at various ages are random. Some illustrative calculations have been carried out. 相似文献
2.
Milan V. Patel Samir A. Patel Arabinda Ray Rajni M. Patel 《Journal of polymer science. Part A, Polymer chemistry》2004,42(20):5227-5234
Copolymers of monomers 2,4‐dichlorophenyl methacrylate (2,4‐DMA) and methyl methacrylate (MMA) were synthesized with different monomer feed ratios using toluene as a solvent and 2,2′‐azobisisobutyronitrile (AIBN) as an initiator at 70 °C. The copolymers were characterized by IR‐spectroscopy, and copolymer composition was determined with UV‐spectroscopy. The linearization method of Fineman–Ross was employed to obtain the monomer reactivity ratios. The molecular weights and polydispersity indexes were determined by gel permeation chromatography (GPC). Thermogravimetric analyses of polymers were carried out in nitrogen atmosphere. The homo‐ and copolymers were tested for their antimicrobial properties against selected microorganisms. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5227–5234, 2004 相似文献
3.
A server needs to compute a broadcast schedule for n pages whose request times are known in advance. Outputting a page satisfies all outstanding requests for the page. The goal is to minimize the average waiting time of a client. In this paper, we show the equivalence of two apparently different relaxations that have been considered for this problem. 相似文献
4.
N. Ponpandian A. Narayanasamy D. Prabhu K. Ganesan M. Manivel Raja K. Chattopadhyay 《Journal of magnetism and magnetic materials》2006
The Fe73.5Cu1Nb3Si13.5B9 FINEMET alloy has been prepared by the rapid solidification technique. The critical behaviour of this alloy in the amorphous as well as in its nanocrystalline states has been studied near their respective Curie temperatures. From the values of the critical exponents one can conclude that the alloy behaves like a 3D Heisenberg ferromagnet in the amorphous and nanocrystalline states. But there exists a slight increase in the value of β for the alloy annealed at 823 K (the nanocrystalline state) as observed in most of the amorphous alloys. 相似文献
5.
Bilevel programming approach applied to the flow shop scheduling problem under fuzziness 总被引:1,自引:0,他引:1
Samir A. Abass 《Computational Management Science》2005,2(4):279-293
This paper presents a fuzzy bilevel programming approach to solve the flow shop scheduling problem. The problem considered
here differs from the standard form in that operators are assigned to the machines and imposing a hierarchy of two decision
makers with fuzzy processing times. The shop owner considered higher level and assigns the jobs to the machines in order to
minimize the flow time while the customer is the lower level and decides on a job schedule in order to minimize the makespan.
In this paper, we use the concepts of tolerance membership function at each level to define a fuzzy decision model for generating
optimal (satisfactory) solution for bilevel flow shop scheduling problem. A solution algorithm for solving this problem is
given.
Mathematics Subject Classification:
90C70, 90B36, 90C99 相似文献
6.
7.
A convenient and enantioselective synthesis of ethyl (8RS, 15R)-8-acetoxy-15-hydroxyhexadecanoate15 via a chemoenzymatic approach has been described. The salient features of the synthesis were operational simplicity, use of easily accessible materials, and excellent enantiocontrol via lipase catalyzed acetylation of 2-alkanol. 相似文献
8.
We derive a fourth-order compact finite difference scheme for a two-dimensional elliptic problem with a mixed derivative and constant coefficients. We conduct experimental study on numerical solution of the problem discretized by the present compact scheme and the traditional second-order central difference scheme. We study the computed accuracy achieved by each scheme and the performance of the Gauss-Seidel iterative method, the preconditioned GMRES iterative method, and the multigrid method, for solving linear systems arising from the difference schemes. 相似文献
9.
J. Mohanty H. Pal S. K. Nayak S. Chattopadhyay A. V. Sapre 《Chemical physics letters》2003,370(5-6):641-646
Fluorescence quenching of methoxycalixarenes (MOCX) by chloroalkanes (CA) has been investigated in acetonitrile solutions. Observed quenching is attributed to photoinduced dissociative electron transfer (DET) interaction, which is supported by the characterization of the Cl− ions and by the radical scavenging experiments. Comparing the Cl− yields with different DET systems, it is inferred that both concerted and stepwise DET mechanisms operate simultaneously in MOCX–CA systems. A correlation of the quenching constants with the free-energy changes following a suitable DET theory supports the above inference. 相似文献
10.
It has been found that the states of the 2-charge extremal D1–D5 system are given by smooth geometries that have no singularity and no horizon individually, but a ‘horizon’ does arise after ‘coarse-graining’. To see how this concept extends to the 3-charge extremal system, we construct a perturbation on the D1–D5 geometry that carries one unit of momentum charge P. The perturbation is found to be regular everywhere and normalizable, so we conclude that at least this state of the 3-charge system behaves like the 2-charge states. The solution is constructed by matching (to several orders) solutions in the inner and outer regions of the geometry. We conjecture the general form of ‘hair’ expected for the 3-charge system, and the nature of the interior of black holes in general. 相似文献