全文获取类型
收费全文 | 12324篇 |
免费 | 2739篇 |
国内免费 | 1275篇 |
专业分类
化学 | 2694篇 |
晶体学 | 170篇 |
力学 | 1318篇 |
综合类 | 152篇 |
数学 | 2076篇 |
物理学 | 9928篇 |
出版年
2024年 | 22篇 |
2023年 | 146篇 |
2022年 | 286篇 |
2021年 | 340篇 |
2020年 | 392篇 |
2019年 | 320篇 |
2018年 | 329篇 |
2017年 | 427篇 |
2016年 | 505篇 |
2015年 | 474篇 |
2014年 | 715篇 |
2013年 | 917篇 |
2012年 | 798篇 |
2011年 | 866篇 |
2010年 | 819篇 |
2009年 | 825篇 |
2008年 | 826篇 |
2007年 | 770篇 |
2006年 | 782篇 |
2005年 | 707篇 |
2004年 | 721篇 |
2003年 | 606篇 |
2002年 | 552篇 |
2001年 | 452篇 |
2000年 | 440篇 |
1999年 | 375篇 |
1998年 | 322篇 |
1997年 | 260篇 |
1996年 | 231篇 |
1995年 | 158篇 |
1994年 | 144篇 |
1993年 | 110篇 |
1992年 | 93篇 |
1991年 | 82篇 |
1990年 | 77篇 |
1989年 | 86篇 |
1988年 | 60篇 |
1987年 | 46篇 |
1986年 | 55篇 |
1985年 | 38篇 |
1984年 | 27篇 |
1983年 | 13篇 |
1982年 | 23篇 |
1981年 | 20篇 |
1980年 | 17篇 |
1979年 | 12篇 |
1978年 | 13篇 |
1977年 | 9篇 |
1976年 | 7篇 |
1957年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
Curtis Bennett Kathy J. Dempsey Bruce E. Sagan 《Journal of Algebraic Combinatorics》1994,3(3):261-283
We construct a family of partially ordered sets (posets) that are q-analogs of the set partition lattice. They are different from the q-analogs proposed by Dowling [5]. One of the important features of these posets is that their Whitney numbers of the first and second kind are just the q-Stirling numbers of the first and second kind, respectively. One member of this family [4] can be constructed using an interpretation of Milne [9] for S[n, k] as sequences of lines in a vector space over the Galois field F
q. Another member is constructed so as to mirror the partial order in the subspace lattice. 相似文献
102.
提出了一种制备偶数个多原子Greenberger-Horne-Zerlinger态的方案,它是基于原子-腔场相互作用.首先n个分离的腔初始时处于真空态,通过双光子转移,把n个腔制备成数态|2>和真空态|o>的缠结态.随后,与腔场发生共振相互作用的2n个等同的原子被分别送入n个腔,通过相互作用后,2n个原子处于GHZ态,而n个腔仍然处于真空态. 相似文献
103.
一、引 言 利用垂直场反馈控制等离子体位移是所有托卡马克装置运行的重要组成部分。对于中小型的托卡马克装置,人们曾倾向于用大功率晶闸管作反馈系统的调节器。它所遇到的主要困难有:第一需要有一个较大功率的中频电源。无论是中频发电机或者是逆变器都需要有较大的投资。另一方面受到中频电源的频率及晶闸管的关断时间的限制使反馈系统的时间响 相似文献
104.
Li Heng—pei 《大学数学》1993,(1)
<正> In this paper we'll prove a fundameutal property of the vector space by means of the ex-tension field,i.e.the numbers of the elements of a basis of the vector space V over the field Fequal to the d imensions(V:F). 相似文献
105.
ZHU Hai-Xia YAN Shi-Lei 《理论物理通讯》2004,42(11)
We study the ferromagnetic properties of spin-1 system, which is considered in the frame of the bond dilution and random positive or negative anisotropy Blume-Capel model in the effective field theory and a cutting approximation. The investigation of phase diagrams displays some rich properties of the trajectory of tricritical point, reentrant henomena at low temperatures. Under certain both bond concentrations and random negative anisotropy, there are new transition lines of double tricritical points. So special emphasis is placed on the influence of the bond dilution and random anisotropy on phase diagrams. The magnetizations of the system are also discussed. Some results have not been evealed in previous reports. 相似文献
106.
C. A. Clarkson A. A. Coley E. S. D. O'Neill R. A. Sussman R. K. Barrett 《General Relativity and Gravitation》2003,35(6):969-990
We discuss inhomogeneous cosmological models which satisfy the Copernican principle. We construct some inhomogeneous cosmological models starting from the ansatz that the all the observers in the models view an isotropic cosmic microwave background. We discuss multi-fluid models, and illustrate how more general inhomogeneous models may be derived, both in General Relativity and in scalar-tensor theories of gravity. Thus we illustrate that the cosmologicalprinciple, the assumption that the Universe we live in is spatially homogeneous, does not necessarily follow from the Copernican principle and the high isotropy of the cosmic microwave background. We also present some new conformally flat two-fluid solutions of Einstein's field equations. 相似文献
107.
Ken‐ichi Shinohara Tasuku Suzuki Takeshi Kitami Shingo Yamaguchi 《Journal of polymer science. Part A, Polymer chemistry》2006,44(2):801-809
We fabricated a micrometer‐long supramolecular chain in which π‐conjugated polyrotaxane was coupled. A new experimental setup was designed and constructed, and the simultaneous direct imaging of the structure and fluorescent function was achieved. Furthermore, we identified the formation of a polymer intertwined network and observed novel fluorescence due to a long‐range interaction via this intertwined network over a distance of 5 μm or more without quenching over 15 min in the near field. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 801–809, 2006 相似文献
108.
J.D. Dutson D. Litvinov M.R.J. Gibbs Y. Inaba H. Muraoka K. O’Grady 《Journal of magnetism and magnetic materials》2006
In this paper, we discuss two key aspects of magnetisation reversal in magnetic thin films with perpendicular anisotropy. Firstly, a study has been made of the additional field required to erase data written perpendicular to a thin film recording disk as the linear data density is increased. It has been found that an increase in data density from 40 to 360 kfci results in an increase of 1.25 kOe in the field required to erase the data. Secondly, the effect of varying the level of exchange coupling by co-sputtering CoCrPt samples with SiO2 has been studied using a characterisation technique that is independent of the self-demagnetising field. It has been found that the samples are fully exchange de-coupled when the film contains >9.8% SiO2 and the activation volume of reversal remains constant for higher levels of SiO2. 相似文献
109.
Nicolas Bouleau 《Journal of Functional Analysis》2007,251(1):325-345
The error on a real quantity Y due to the graduation of the measuring instrument may be asymptotically represented, when the graduation is regular and fines down, by a Dirichlet form on R whose square field operator does not depend on the probability law of Y as soon as this law possesses a continuous density. This feature is related to the “arbitrary functions principle” (Poincaré, Hopf). We give extensions of this property to Rd and to the Wiener space for some approximations of the Brownian motion. This gives new approximations of the Ornstein-Uhlenbeck gradient. These results apply to the discretization of some stochastic differential equations encountered in mechanics. 相似文献
110.
The mid-infrared (1500-3800 cm−1) absorption spectrum of gaseous nitric oxide has been studied at low temperature (99 K) with a long absorption path (160 m) in order to observe weak combination, difference, and overtone bands of the NO dimer. About ten new bands were assigned with greater or lesser certainty. Combined with previous results, they lead to a set of 12 secure and 7 tentative vibrational term values for (NO)2, essentially doubling our knowledge of NO dimer vibrational states. The strongest non-fundamental bands in this region, other than the ν1 (symmetric N-O stretch) + ν5 (asymmetric N-O stretch) overtone, involve combinations of ν5 with ν3 (intermolecular stretch). Excitation of ν5 results in increased frequencies for the intermolecular modes ν2, ν3, and ν4. A new value of 155.5 cm−1 was obtained for ν4, the elusive infrared-inactive out-of-plane fundamental vibration. 相似文献