全文获取类型
收费全文 | 144277篇 |
免费 | 10570篇 |
国内免费 | 6970篇 |
专业分类
化学 | 69364篇 |
晶体学 | 1408篇 |
力学 | 10994篇 |
综合类 | 515篇 |
数学 | 39616篇 |
物理学 | 39920篇 |
出版年
2024年 | 228篇 |
2023年 | 1400篇 |
2022年 | 2281篇 |
2021年 | 2355篇 |
2020年 | 2521篇 |
2019年 | 2423篇 |
2018年 | 12056篇 |
2017年 | 11672篇 |
2016年 | 8701篇 |
2015年 | 3868篇 |
2014年 | 3924篇 |
2013年 | 5136篇 |
2012年 | 9488篇 |
2011年 | 16060篇 |
2010年 | 9445篇 |
2009年 | 9756篇 |
2008年 | 10512篇 |
2007年 | 12243篇 |
2006年 | 3760篇 |
2005年 | 4337篇 |
2004年 | 3942篇 |
2003年 | 3791篇 |
2002年 | 2657篇 |
2001年 | 1752篇 |
2000年 | 1699篇 |
1999年 | 1709篇 |
1998年 | 1518篇 |
1997年 | 1309篇 |
1996年 | 1417篇 |
1995年 | 1183篇 |
1994年 | 1081篇 |
1993年 | 957篇 |
1992年 | 820篇 |
1991年 | 726篇 |
1990年 | 603篇 |
1989年 | 538篇 |
1988年 | 424篇 |
1987年 | 406篇 |
1986年 | 354篇 |
1985年 | 346篇 |
1984年 | 244篇 |
1983年 | 212篇 |
1982年 | 186篇 |
1981年 | 150篇 |
1980年 | 128篇 |
1979年 | 93篇 |
1978年 | 90篇 |
1977年 | 70篇 |
1975年 | 73篇 |
1973年 | 82篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
This paper studies a supply chain consisting of two suppliers and one retailer in a spot market, where the retailer uses the
newsvendor solution as its purchase policy, and suppliers compete for the retailer’s purchase. Since each supplier’s bidding
strategy affects the other’s profit, a game theory approach is used to identify optimal bidding strategies. We prove the existence
and uniqueness of a Nash solution. It is also shown that the competition between the supplier leads to a lower market clearing
price, and as a result, the retailer benefits from it. Finally, we demonstrate the applicability of the obtained results by
deriving optimal bidding strategies for power generator plants in the deregulated California energy market.
Supported in part by RGC (Hong Kong) Competitive Earmarked Research Grants (CUHK4167/04E and CUHK4239/03E), a Distinguished
Young Investigator Grant from the National Natural Sciences Foundation of China, and a grant from Hundred Talents Program
of the Chinese Academy of Sciences. 相似文献
992.
Clifford algebra corresponds to Minkwoski space. The coupling between real object particles and light quantums can be discussed
by Minkowski space’s directional strangeness. We introduce Galilei transfomation and Schr?dinger equation into Minkowski space
and give a geometrical explanation for classical quantum theory. 相似文献
993.
Kung-Yu Chen 《Journal of Mathematical Analysis and Applications》2004,298(2):411-417
In his recent investigations involving differential operators for some generalizations of the classical Laguerre polynomials, H. Bavinck [J. Phys. A Math. Gen. 29 (1996) L277-L279] encountered and proved a certain summation identity for the classical Laguerre polynomials. The main object of this sequel to Bavinck's work is to prove a generalization of this summation identity for the Srivastava-Singhal polynomials. The demonstration, which is presented here in the general case, differs markedly from the earlier proof given for the known special case. It is also indicated how the general summation identity can be applied to derive the corresponding result for one class of the Konhauser biorthogonal polynomials. 相似文献
994.
995.
Currently, most combinatorial optimisation problems have to be solved, if the optimum solution is sought, using general techniques
to explore the space of feasible solutions and, more specifically, through exploratory enumerative procedures in trees and
search graphs. We propose Branch and Win, a general formulation for understanding and synthesising the different tree search
procedures that have been presented in the literature of operations research as well as in that of artificial intelligence.
Several general ideas are also presented, whose application allows designing new hybrid search algorithms, in order to implement
the procedure. 相似文献
996.
Zhigang Yin Nuofu Chen Shulin Song Jun Zhong Kurash Ibrahim 《Solid State Communications》2005,135(7):430-433
Nickel-doped ZnO (Zn1−xNixO) have been produced using rf magnetron sputtering. X-ray diffraction measurements revealed that nickel atoms were successfully incorporated into ZnO host matrix without forming any detectable secondary phase. Ni 2p core-level photoemission spectroscopy confirmed this result and suggested Ni has a chemical valence of 2+. According to the magnetization measurements, no ferromagnetic but paramagnetic behavior was found for Zn0.86Ni0.14O. We studied the electronic structure of Zn0.86Ni0.14O by valence-band photoemission spectroscopy. The spectra demonstrate a structure at ∼2 eV below the Fermi energy EF, which is of Ni 3d origin. No emission was found at EF, suggesting the insulating nature of the film. 相似文献
997.
Arne Schirrmacher 《Physics in Perspective (PIP)》2003,5(1):4-20
David Hilbert (1862-1943) played an important role in establishing quantum physics in Göttingen. I analyze the ways in which his influence was decisive by comparison with Woldemar Voigt (1850-1919). Voigt was the leading Göttingen theoretical physicist before the arrival of Peter Debye (1884-1966), who was appointed to a new professorship in 1914 at Hilbert's instigation. I portray the Göttingen mathematicians, above all Hermann Minkowski (1864-1909) and David Hilbert, as planting the seeds for the blossoming of quantum physics under their student Max Born (1882-1970) in the 1920s. 相似文献
998.
Sulaiman Wadi Harun Nizam Tamchek Mohd Kamil Abd-Rahman Prabakaran Poopalan Harith Ahmad 《Optical Review》2003,10(3):133-135
A multiwavelength Brillouin/erbium fibre laser (BEFL) which operates in the long wavelength (L-band) region is demonstrated for potential applications in an L-band wavelength division multiplexing (WDM) communication system. The laser configuration consists of a long erbium-doped fibre to enable L-band amplification where two 3-dB couplers take a portion of the generated BEFL signal and re-inject it into the single mode fibre to seed a cascaded BEFL line in the same direction as the first BEFL line. A stable and strong laser comb of up to five lines with 10-GHz spacing has been obtained with a Brillouin pump (BP) of 9.2 mW and a 980 nm pump of 92 mW. The BEFL has shown a broad tuning range with a tuning characteristic for line #1 which is flat over a range greater than 9.9 nm. 相似文献
999.
Wolfgang Staubach 《Journal d'Analyse Mathématique》2003,91(1):389-400
In this paper, we present an explicit calculation of the heat kernel, fundamental solution and Schwartz kernel of the resolvent
for the Heisenberg Laplacian using Wiener path integrals and their realizations via the Trotter product formula. This also
gives another derivation of mehler’s formula. 相似文献
1000.
Xiuhong Chen 《Journal of Mathematical Analysis and Applications》2003,286(1):261-270
A dual problem associated with a class of variational problems is formulated that involves second derivatives of the functions. Under the invexity assumptions on the functions that compose the primal problems, second-order duality results (weak duality, strong duality and converse duality) are derived for this pair of problems. 相似文献