全文获取类型
收费全文 | 15610篇 |
免费 | 2675篇 |
国内免费 | 1103篇 |
专业分类
化学 | 8827篇 |
晶体学 | 103篇 |
力学 | 1108篇 |
综合类 | 265篇 |
数学 | 1711篇 |
物理学 | 7374篇 |
出版年
2024年 | 31篇 |
2023年 | 134篇 |
2022年 | 522篇 |
2021年 | 520篇 |
2020年 | 518篇 |
2019年 | 466篇 |
2018年 | 468篇 |
2017年 | 586篇 |
2016年 | 669篇 |
2015年 | 624篇 |
2014年 | 817篇 |
2013年 | 1136篇 |
2012年 | 1060篇 |
2011年 | 981篇 |
2010年 | 830篇 |
2009年 | 735篇 |
2008年 | 792篇 |
2007年 | 961篇 |
2006年 | 873篇 |
2005年 | 703篇 |
2004年 | 651篇 |
2003年 | 623篇 |
2002年 | 536篇 |
2001年 | 431篇 |
2000年 | 472篇 |
1999年 | 431篇 |
1998年 | 342篇 |
1997年 | 377篇 |
1996年 | 293篇 |
1995年 | 264篇 |
1994年 | 209篇 |
1993年 | 174篇 |
1992年 | 178篇 |
1991年 | 145篇 |
1990年 | 143篇 |
1989年 | 124篇 |
1988年 | 123篇 |
1987年 | 77篇 |
1986年 | 60篇 |
1985年 | 62篇 |
1984年 | 57篇 |
1983年 | 25篇 |
1982年 | 39篇 |
1981年 | 24篇 |
1980年 | 24篇 |
1979年 | 16篇 |
1978年 | 13篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1974年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
The main objects of study in this article are two classes of Rankin–Selberg L-functions, namely L(s,f×g) and L(s, sym2(g)× sym2(g)), where f,g are newforms, holomorphic or of Maass type, on the upper half plane, and sym2(g) denotes the symmetric square lift of g to GL(3). We prove that in general, i.e., when these L-functions are not divisible by L-functions of quadratic characters (such divisibility happening rarely), they do not admit any LandauSiegel zeros. Such zeros, which are real and close to s=1, are highly mysterious and are not expected to occur. There are corollaries of our result, one of them being a strong lower bound for special value at s=1, which is of interest both geometrically and analytically. One also gets this way a good bound onthe norm of sym2(g). 相似文献
72.
The use of compressive crushing equipment such as gyratory crushers within minerals processing plants can potentially generate large quantities of dust. Remedies to this problem include the retrofitting of shrouds, enclosures, local exhaust ventilation (LEV) systems and water suppression systems. The single or combined application of these systems must be optimised to ensure they operate efficiently. It is desirable that the future design planning of such facilities include integrated dust suppression and/or removal systems to ensure material delivery rates are maintained and the welfare of the workforce is protected. 相似文献
73.
Toshiki Kono Toshikazo Sakaguchi Yanming Hu Masashi Shiotsuki Fumio Sanda Toshio Masuda 《Journal of polymer science. Part A, Polymer chemistry》2006,44(20):5943-5953
Phenylacetylene (PA) derivatives having two polar groups (ester, 2a – d ; amide, 4) or one cyclic polar group (imide, 5a – c ) were polymerized using (nbd)Rh+[(η6‐C6H5)B?(C6H5)3] catalyst to afford high molecular weight polymers (~1 × 106 – 4 × 106). The hydrolysis of ester‐containing poly(PA), poly( 2a) , provided poly(3,4‐dicarboxyPA) [poly ( 3 )], which could not be obtained directly by the polymerization of the corresponding monomer. The solubility properties of the present polymers were different from those of poly(PA) having no polar group; that is, poly( 2a )–poly( 2d ) dissolved in ethyl acetate and poly( 4 ) dissolved in N,N‐dimethylformamide, while poly(PA) was insoluble in such solvents. Ester‐group‐containing polymers [poly( 2a )–poly( 2d )] afforded free‐standing membranes by casting from THF solutions. The membrane of poly( 2a ) showed high carbon dioxide permselectivity against nitrogen (PCO2/PN2 = 62). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5943–5953, 2006 相似文献
74.
Makoto Kato Azusa Tsukigase Hiromitsu Tanaka Arimitsu Usuki Isamu Inai 《Journal of polymer science. Part A, Polymer chemistry》2006,44(3):1182-1188
Isobutylene isoprene rubber (IIR)‐clay nanocomposites have been prepared successfully by melt intercalation with maleic anhydride‐grafted IIR (Ma‐g‐IIR) and organophilic clay. In IIR‐clay nanocomposites, the silicate layers of the clay were exfoliated and dispersed into the monolayer. The nanocomposites exhibited greater gas barrier properties compared with those of Ma‐g‐IIR. When 15 phr clay was added, gas barrier properties were 2.5 times greater than those of Ma‐g‐IIR. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1182–1188, 2006 相似文献
75.
Tungsten trioxide and titanium dioxide thin films were synthesised by pulsed laser deposition. We used for irradiations of oxide targets an UV KrF* (λ = 248 nm, τFWHM ≅ 20 ns, ν = 2 Hz) excimer laser source, at 2 J/cm2 incident fluence value. The experiments were performed in low oxygen pressure. The (0 0 1) SiO2 substrates were heated during the thin film deposition process at temperature values within the 300-500 °C range. The structure and crystalline status of the obtained oxide thin films were investigated by high resolution transmission electron microscopy. Our analyses show that the films are composed by nanoparticles with average diameters from a few to a few tens of nm. Moreover, the films deposited at substrate temperatures higher than 300 °C are crystalline. The tungsten trioxide films consist of a mixture of triclinic and monoclinic phases, while the titanium dioxide films structure corresponds to the tetragonal anatase phase. The oxide films average transmittance in the visible-infrared spectral range is higher than 80%, which makes them suitable for sensor applications. 相似文献
76.
77.
Jeffrey C. Johnson Dawn L. Parks 《Computational & Mathematical Organization Theory》1998,4(3):223-239
Earlier research has shown a relationship between various forms of structural centrality and perceived leadership and role
satisfaction in small experimental groups. The limited amount of research on this topic in naturally occurring social networks
has yielded results that often conflict with one another. Different results have generally been attributed to possible differences
in task environments. This paper examines the relationship between two types of structural centrality and perceived influence,
role satisfaction, and perceived effectiveness in an environmental resource management program. Findings in this paper suggest
that the observed differences in relationships between the network and other variables is partly a function of global network
properties (e.g., marginality of subgroups) and related task environments.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
78.
We consider the two-dimensional one-component plasma without a background and confined to a half-plane near a metal wall. The particles are also subjected to an external potential acting perpendicular to the wall with an inverse-power-law Boltzmann factor. The model has a known solvable isotherm which exhibits a Kosterlitz-Thouless-type transition from a conductive to an insulator phase as the power law is varied. This allows predictions of theoretical methods of analyzing the Kosterlitz-Thouless transition to be compared with the exact solution. In particular, we calculate the asymptotic density profile by resumming its low-fugacity expansion near the zero-density critical coupling in the insulator phase, and solving a mean-field equation deduced from the first BGY equation. Agreement with the exact solution is obtained. As the former calculation makes essential use of the nested dipole hypothesis of Kosterlitz and Thouless, the validity of this hypothesis is explicitly verified. 相似文献
79.
80.
We investigate the topology of the phase diagram of binary alloys on the fee lattice with first-neighbor antiferromagnetic interactions around the superdegenerate point, where the L10 and L12 phases meet. We treat the system as a hard-constraint lattice gas, following a procedure previously described by Lebowitzet al. We perform cluster variation method calculations in theT0 limit and Monte Carlo simulations directly atT=0 K on the ground states of the superdegenerate point. We find that: (i) there is no disordered phase in the neighborhood of this point; (ii) a phase L for which two of the four cubic sublattices have the same average occupancy and each of the two others are different appears between L10 and L12; (iii) the transition L/L12 is of first order. 相似文献