全文获取类型
收费全文 | 11034篇 |
免费 | 475篇 |
国内免费 | 11篇 |
专业分类
化学 | 6960篇 |
晶体学 | 132篇 |
力学 | 398篇 |
综合类 | 1篇 |
数学 | 1878篇 |
物理学 | 2151篇 |
出版年
2023年 | 76篇 |
2022年 | 92篇 |
2021年 | 139篇 |
2020年 | 194篇 |
2019年 | 201篇 |
2018年 | 277篇 |
2017年 | 247篇 |
2016年 | 440篇 |
2015年 | 342篇 |
2014年 | 380篇 |
2013年 | 903篇 |
2012年 | 764篇 |
2011年 | 826篇 |
2010年 | 479篇 |
2009年 | 429篇 |
2008年 | 653篇 |
2007年 | 667篇 |
2006年 | 554篇 |
2005年 | 507篇 |
2004年 | 393篇 |
2003年 | 368篇 |
2002年 | 311篇 |
2001年 | 157篇 |
2000年 | 124篇 |
1999年 | 110篇 |
1998年 | 99篇 |
1997年 | 72篇 |
1996年 | 103篇 |
1995年 | 86篇 |
1994年 | 81篇 |
1993年 | 73篇 |
1992年 | 73篇 |
1991年 | 50篇 |
1990年 | 51篇 |
1989年 | 57篇 |
1988年 | 43篇 |
1987年 | 42篇 |
1985年 | 84篇 |
1984年 | 68篇 |
1983年 | 44篇 |
1982年 | 74篇 |
1981年 | 56篇 |
1980年 | 69篇 |
1979年 | 70篇 |
1978年 | 59篇 |
1977年 | 54篇 |
1976年 | 74篇 |
1975年 | 57篇 |
1974年 | 55篇 |
1973年 | 45篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
J. C. Fabris S. V. B. Gonçalves P. E. de Souza 《General Relativity and Gravitation》2002,34(12):2111-2126
The mass power spectrum for a Universe dominated by the Chaplygin gas is evaluated numerically from scales of the order of the Hubble horizon to 100 Mpc. The results are compared with a pure baryonic Universe and a cosmological constant model. In all three cases, the spectrum increases with k, the wavenumber of the perturbations. The slope of the spectrum is higher for the baryonic model and smaller for the cosmological constant model, the Chaplygin gas interpolating these two models. The results are analyzed in terms of the sound velocity of the Chaplygin gas and the moment the Universe begins to accelerate. 相似文献
12.
Balázs Szendröi 《Mathematische Zeitschrift》2002,240(2):233-241
This note shows that a certain toric quotient of the quintic Calabi-Yau threefold in provides a counterexample to a recent conjecture of Cox and Katz concerning nef cones of toric hypersurfaces.
Received: 8 February 2001; in final form: 17 September 2001 / Published online: 1 February 2002 相似文献
13.
We analyze the dynamics of an AdS5 braneworld with matter fields when gravity is allowed to deviate from the Einstein form on the brane. We consider exact five-dimensional warped solutions which are associated with conformal bulk fields of weight –4 and describe on the brane the following three dynamics: those of inhomogeneous dust, of generalized dark radiation, and of homogeneous polytropic dark energy. We show that, with modified gravity on the brane, the existence of such dynamical geometries requires the presence of non-conformal matter fields confined to the brane. 相似文献
14.
D. C. Oliveira Y. Messaddeq K. Dahmouche S. J. L. Ribeiro R. R. Gonçalves A. Vesperini D. Gindre J.-M. Nunzi 《Journal of Sol-Gel Science and Technology》2006,40(2-3):359-363
Organic-inorganic hybrid materials were prepared from an ureasil precursor (ureapropyltriethoxysilane designated as UPTES)
and acrylic acid modified zirconium (IV) n-propoxide. Thin films containing rhodamine 6G (Rh6G) were prepared by spin-coating on glass substrates with different Zr:Si molar ratios (Zr:Si = 75:25, 50:50 and 25:75). Refractive
index, thickness, number of propagating modes and attenuation coefficient were measured at 543.5, 632.8 and 1550 nm wavelengths
by the prism coupling technique. Distributed feedback (DFB) laser effect was observed and studied as a function of films thickness
and refractive index. 相似文献
15.
16.
For more than 25 yearsJΨ production has helped to sharpen our understanding of QCD. In proton induced reaction some observations are rather well understood
while others are still unclear. The current status of the theory ofJΨ production will be sketched, paying special attention to the issues of formation time andJΨ re-interaction in a nuclear medium. 相似文献
17.
In order to investigate the relative effects of the differences between the structures and lipophilicities of 1, 10-dioxa-4, 7, 13, 16-tetra-azacyclo-octadecane (TA-18-crown-6) and the tetrabenzyl derivative of 1,10-dioxa-4, 7, 13, 16-tetra-azacyclo-octadecane (TBTA-18-crown-6) on their extraction-abilities and -selectivities for transition metal cations, constants of the overall extraction (logK
ex) of 1:1 (M:L) complexes, the distribution (K
D) for two diluents (CH2Cl2 and CHCl3) with different dielectric constants have been determined at 25 ± 0.1 °C. The magnitude of logK
ex is largely determined by that of K
D. The equilibrium constants of TA-18-crown-6 have been compared with those of TBTA-18-crown-6. It is found that:(i) logK
ex sequences of TA-18-crown-6 and TBTA-18-crown-6 for transition metals in CH2Cl2 lie in order: Fe3+ > Cu2+ > Mn2+ > Co2+ > Cd2+ > Ni2+ > Zn2+ and Fe3+ > Cu2+ > Co2+ > Mn2+ > Ni2+ > Cd2+ > Zn2+ respectively; (ii) the stability sequences of two types of tetra-aza-crown ethers with the transition metal cations in CHCl3 are the same as follows: Fe3+ > Ni2+ > Cu2+ > Co2+ > Zn2+ > Cd2+ > Mn2+, and (iii) unusual selectivities are observed for transition metal-tetra-aza-crowns, e.g. the high Fe3+/M
n+ selectivity factors (Sf) of TA-18-crown-6, except for the competitive-extractions for the special case in CHCl3 of TBTA-18-crown-6, it was found that the Mn2+/M
n+ values were relatively higher according to the other transition metal cations. A systematic sequence in these two types of solvents is not found for a given transition metal cation in terms of the variation of selectivity with the tetra-aza-crown ethers. The results provide alternatives for the rational design of other specific ligands on the transition metal cations. 相似文献
18.
19.
K. Morigaki K. Takeda H. Hikita C. Ogihara P. Roca i Cabarrocas 《Journal of Non》2008,354(19-25):2131-2134
Our model for light-induced defect creation in hydrogenated amorphous silicon is applied to its kinetics, i.e., the growing curve of light-induced dangling bond density as a function of illumination time, which is fitted to a stretched exponential function. Two parameters β and τ involved in the function are estimated as functions of saturated dangling bond density in terms of our model. These are compared with two experimental results, i.e., our results obtained from ESR measurements and Shimakawa et al.’s results obtained from photoconductivity measurements. The saturated dangling bond density is also measured as a function of the generation rate of free carriers. The experimental results are compared with calculated results and discussed. 相似文献
20.
We introduce here some Itô calculus for non-continuous Dirichlet processes. Such calculus extends what was known for continuous Dirichlet processes or for semimartingales. In particular we prove that non-continuous Dirichlet processes are stable under C
1 transformation. 相似文献