全文获取类型
收费全文 | 104581篇 |
免费 | 5233篇 |
国内免费 | 4032篇 |
专业分类
化学 | 43939篇 |
晶体学 | 1085篇 |
力学 | 8127篇 |
综合类 | 271篇 |
数学 | 34981篇 |
物理学 | 25443篇 |
出版年
2024年 | 45篇 |
2023年 | 481篇 |
2022年 | 571篇 |
2021年 | 852篇 |
2020年 | 993篇 |
2019年 | 1079篇 |
2018年 | 11166篇 |
2017年 | 10889篇 |
2016年 | 7264篇 |
2015年 | 2077篇 |
2014年 | 1839篇 |
2013年 | 2389篇 |
2012年 | 6222篇 |
2011年 | 12968篇 |
2010年 | 7484篇 |
2009年 | 7768篇 |
2008年 | 8567篇 |
2007年 | 10522篇 |
2006年 | 2011篇 |
2005年 | 2702篇 |
2004年 | 2650篇 |
2003年 | 2871篇 |
2002年 | 1907篇 |
2001年 | 956篇 |
2000年 | 836篇 |
1999年 | 743篇 |
1998年 | 621篇 |
1997年 | 538篇 |
1996年 | 581篇 |
1995年 | 444篇 |
1994年 | 362篇 |
1993年 | 373篇 |
1992年 | 254篇 |
1991年 | 269篇 |
1990年 | 220篇 |
1989年 | 182篇 |
1988年 | 170篇 |
1987年 | 151篇 |
1986年 | 141篇 |
1985年 | 117篇 |
1984年 | 105篇 |
1983年 | 80篇 |
1982年 | 76篇 |
1981年 | 63篇 |
1980年 | 74篇 |
1979年 | 54篇 |
1978年 | 50篇 |
1973年 | 43篇 |
1914年 | 45篇 |
1909年 | 41篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Graham Smith 《The Journal of the Operational Research Society》1989,40(9):761-770
Courses which teach discrete-event simulation are based on many different simulation languages. The requirements for a language to support teaching simulation are discussed. In particular, it is recommended that such languages separate into distinct modules those aspects of simulation which are taught as separate topics. Implementation of the separation is discussed. The SEESIM language, developed as a teaching aid, is described, and examples of its use are given. Straightforward use of SEESIM can be learned quickly, yet the language provides facilities for a staged introduction to advanced concepts of simulation. 相似文献
62.
63.
A two-dimensional, nonlinear, compressible, diabatic, nonhydrostatic photochemical-dynamical gravity wave model has been advanced. The model includes diabetic process produced by photochemistry and the effect of gravity wave on atmospheric chemical species. In the horizontal direction, the pseudospectral method is used. The finite difference approximations are used in vertical direction z and time t. The FICE method is used to solve the model. The model results on small amplitude fluctuation are very close to those of linear theory, which demonstrates the correctness of the model.
相似文献64.
J Ashenfelter 《Pramana》2002,59(5):713-717
The ESTU began operation in 1988 and achieved the design voltage of 20 MV in 1990. Since that time, improvements to the gas
handling system, negative ion injector, accelerator terminal and control system have greatly increased its capability and
reliability. Today, the ESTU can efficiently produce an extensive assortment of stable ions at wide-ranging energies in support
of low-energy nuclear physics. 相似文献
65.
66.
A pressure sensitive paint (PSP) measurement has been known as a pressure field measurement technique based on the oxygen quenching phenomenon of luminescence of specific luminophores. A PSP measurement was applied for pressure field measurement in a low-solidity circular cascade diffuser of a single-stage transonic centrifugal compressor with 5 in pressure ratio for HFC134a gas. The oxygen concentration was about 500 ppm. Ru (bath-phen) was adsorbed on a silica-gel thinlayer chromatography sheet, and the sheet was pasted onto the side-wall between the cascade vanes. A drastic change in luminescent intensity was recognized during a surge condition. Also the pressure variations based on luminescent intensity agreed well with the pressure fluctuations measured using a semiconductor pressure sensor with high-frequency-response. It was shown that a PSP measurement worked well to investigate the unsteady pressure fields in a circular cascade diffuser of a transonic centrifugal compressor. Moreover, the time response of PSP becomes clear as a problem to be overcome for the present. 相似文献
67.
A new method is introduced to generate a elliptical hollow beam inside a cavity. Using a matrix eigenvalue method, the laser resonator with optical diffraction elements is theoretically analyzed and simulated. A elliptical hollow beam of good quality is realized experimentally. The interaction between linearly polarized elliptical hollow beam and a two-level atom is investigated theoretically. Although the linearly polarized elliptical hollow beam does not carry angular momentum, it can produce very high torque. The atoms initially at rest and located at off-beam- axis positions will rotate under the drive of the torque of the beam. The atomic motion trajectory in the field of elliptical hollow beam has been demonstrated. The study shows that the elliptical hollow beam might be a useful tool in the study of vortex property of Bose-Einstein condensate or ultra cold atom media. 相似文献
68.
69.
Dual fractional cutting plane algorithms, in which cutting planes are used to iteratively tighten a linear relaxation of an integer program,
are well-known and form the basis of the highly successful branch-and-cut method. It is rather less well-known that various primal cutting plane algorithms were developed in the 1960s, for example by Young. In a primal algorithm, the main role of the cutting
planes is to enable a feasible solution to the original problem to be improved. Research on these algorithms has been almost
non-existent.
In this paper we argue for a re-examination of these primal methods. We describe a new primal algorithm for pure 0-1 problems based on strong valid inequalities and give some encouraging computational results. Possible extensions to the case of general
mixed-integer programs are also discussed. 相似文献
70.
Yasuyuki Kawahigashi 《Communications in Mathematical Physics》2002,226(2):269-287
We study the recent construction of subfactors by Rehren which generalizes the Longo–Rehren subfactors. We prove that if
we apply this construction to a non-degenerately braided subfactor N⊂M and α±-induction, then the resulting subfactor is dual to the Longo–Rehren subfactor M⊗M
opp⊂R arising from the entire system of irreducible endomorphisms of M resulting from αplusmn;-induction. As a corollary, we solve a problem on existence of braiding raised by Rehren negatively. Furthermore, we generalize
our previous study with Longo and Müger on multi-interval subfactors arising from a completely rational conformal net of factors
on S
1 to a net of subfactors and show that the (generalized) Longo–Rehren subfactors and α-induction naturally appear in this context.
Received: 11 September 2001 / Accepted: 7 October 2001 相似文献