全文获取类型
收费全文 | 127131篇 |
免费 | 2030篇 |
国内免费 | 411篇 |
专业分类
化学 | 53924篇 |
晶体学 | 1052篇 |
力学 | 7511篇 |
综合类 | 1篇 |
数学 | 41022篇 |
物理学 | 26062篇 |
出版年
2023年 | 368篇 |
2022年 | 372篇 |
2021年 | 566篇 |
2020年 | 767篇 |
2019年 | 704篇 |
2018年 | 11073篇 |
2017年 | 10846篇 |
2016年 | 7698篇 |
2015年 | 2377篇 |
2014年 | 1889篇 |
2013年 | 3776篇 |
2012年 | 6782篇 |
2011年 | 13088篇 |
2010年 | 7368篇 |
2009年 | 7466篇 |
2008年 | 8892篇 |
2007年 | 10794篇 |
2006年 | 2301篇 |
2005年 | 3296篇 |
2004年 | 3278篇 |
2003年 | 3432篇 |
2002年 | 2317篇 |
2001年 | 1285篇 |
2000年 | 1327篇 |
1999年 | 902篇 |
1998年 | 781篇 |
1997年 | 656篇 |
1996年 | 836篇 |
1995年 | 590篇 |
1994年 | 625篇 |
1993年 | 596篇 |
1992年 | 594篇 |
1991年 | 508篇 |
1990年 | 554篇 |
1989年 | 469篇 |
1988年 | 483篇 |
1987年 | 428篇 |
1986年 | 426篇 |
1985年 | 555篇 |
1984年 | 530篇 |
1983年 | 413篇 |
1982年 | 432篇 |
1981年 | 441篇 |
1980年 | 375篇 |
1979年 | 388篇 |
1978年 | 365篇 |
1976年 | 361篇 |
1975年 | 328篇 |
1974年 | 329篇 |
1973年 | 330篇 |
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
901.
Prior studies have shown that inventories in a one vendor, multi-buyer supply chain with deterministic demands can be coordinated effectively through the use of common replenishment epochs (CRE). In this paper, we study the impact of demand uncertainty on the effectiveness of coordinating such a supply chain. We develop a model to analyse the coordination mechanism using CRE in a one-vendor, multi-buyer supply chain, when the demand faced by the buyers is stochastic. Our numerical study based on the model found that coordination through CRE may not always be beneficial when the demand variance is high. We also investigate a strategy of advance order processing by the vendor to improve the effectiveness of coordination through CRE. 相似文献
902.
903.
There is a general interest in ranking schemes applied to complex entities described by multiple attributes. Published rankings
for universities are in great demand but are also highly controversial. We compare two classification and ranking schemes
involving universities; one from a published report, ‘Top American Research Universities’ by the University of Florida's TheCenter and the other using DEA. Both approaches use the same data and model. We compare the two methods and discover important equivalences.
We conclude that the critical aspect in classification and ranking is the model. This suggests that DEA is a suitable tool
for these types of studies. 相似文献
904.
N J Curtis P J Dortmans J Ciuk 《The Journal of the Operational Research Society》2006,57(11):1300-1312
The essential first step of any OR investigation is to ensure that the ‘right problem’ is studied. Our approach is to propose a set of six ‘rights’ or questions whereby achievement against particular aspects of a problem space is made and these provide the basis for scoping the context, understanding the system, and proposing sound options to the decision-maker. This style of problem structuring is an essential element of the Defence problem domain, and especially so for the Land Force, where there exist multiple degrees of freedom for poorly defined problems in an environment of uncertainty and ambiguity. Central to this is performing conceptual rather than analytical modelling, as perturbations then provide a basis for exploring a space, rather than solving a problem. 相似文献
905.
After the laser was invented in 1960, a phase conjugation mirror has been respected to be the most fantastic one for the laser
resonator composition because it can compensate any distortions of the laser beams occurred by the many inhomogenuities of
the laser media and optical components. Among the many phase conjugation configurations, the stimulated Brillouin scattering
phase conjugation mirror is the most simple one and many researchers have tried to utilize it to develop high power/energy
laser systems. For realizing a high energy/power laser system the thermal problem is the most difficult to solve, and some
researchers suggested a beam combination technique to reduce the thermal load of the big laser media to many small sized ones.
To accomplish the beam combination using stimulated Brillouin scattering phase conjugation mirrors (SBS-PCMs), it is necessary
to lock/control the phases of the SBS-PCMs. And some researchers have developed several ways for it, but they can lock the
phases of a limited number of beams overlapped at the foci less than 5, or lock the phases by back-seeding technique but it
loses the phase conjugation characteristics. For realization of the laser fusion driver, it is necessary to combine more than
10 or 100 beams. And the authors have developed recently a new phase controlling/locking technique which is isolated and independent
totally from other beams and it can be applied to an unlimited number of beams in principle. 相似文献
906.
Influence of boric acid on the electrochemical deposition of Ni 总被引:1,自引:0,他引:1
M. Šupicová R. Rozik L. Trnková R. Oriňáková M. Gálová 《Journal of Solid State Electrochemistry》2006,10(2):61-68
The electrolytic deposition of Ni onto a paraffin-impregnated graphite electrode from supporting chloride electrolyte (0.5 mol dm−3 NaCl) adjusted to the required pH using dilute HCl is investigated. The effect of electrolyte composition on the Ni electrodeposition
is studied using linear sweep voltammetry in the cathodic region. An elimination voltammetry procedure was applied to evaluate
the polarization curves. The aim of this work was to deduce the mechanism of Ni reduction in the chloride bath as well as
the influence of boric acid on this. Positively-charged NiCl+ ions were found to be the electroactive particles in the Ni reduction mechanism. The strong competition between the NiCl+, Cl− and H+ ions for active sites at the electrode is discussed. Kinetically-controlled adsorption/desorption processes of various species
were also confirmed using elimination voltammetry with a linear scan. The evolution of gaseous hydrogen, catalyzed by the
freshly-deposited Ni, accompanies the electrodeposition process. The presence of boric acid at a sufficiently high concentration
inhibits the deposition of Ni and, at the same time, improves the morphology and brightness, as well as the adhesion of the
deposited Ni.
Elimination voltammetry with a linear scan is an efficient way to evaluate current–potential curves that reflect the electrodeposition
of one-component Ni coatings. By eliminating selected currents, additional interesting and useful information can be obtained
from voltammetric data. 相似文献
907.
908.
909.
Positive Steady States of a Prey-predator Model with Diffusion and Non-monotone Conversion Rate 总被引:1,自引:0,他引:1
Rui PENG Ming Xin WANG Wen Van CHEN 《数学学报(英文版)》2007,23(4):749-760
In this paper, we study the positive steady states of a prey-predator model with diffusion throughout and a non-monotone conversion rate under the homogeneous Dirichlet boundary condition. We obtain some results of the existence and non-existence of positive steady states. The stability and uniqueness of positive steady states are also discussed. 相似文献
910.
Chang-Wan Kim 《Archiv der Mathematik》2007,88(4):378-384
We showed that any compact locally symmetric Finsler metric with positive flag curvature must be Riemannian.
Dedicated to Professor Karsten Grove on the occassion of his sixtieth birthday
Received: 8 May 2006 相似文献