全文获取类型
收费全文 | 41276篇 |
免费 | 3286篇 |
国内免费 | 2574篇 |
专业分类
化学 | 28476篇 |
晶体学 | 469篇 |
力学 | 1763篇 |
综合类 | 236篇 |
数学 | 4351篇 |
物理学 | 11841篇 |
出版年
2023年 | 307篇 |
2022年 | 395篇 |
2021年 | 858篇 |
2020年 | 878篇 |
2019年 | 943篇 |
2018年 | 789篇 |
2017年 | 771篇 |
2016年 | 1361篇 |
2015年 | 1324篇 |
2014年 | 1696篇 |
2013年 | 2595篇 |
2012年 | 3140篇 |
2011年 | 3476篇 |
2010年 | 2344篇 |
2009年 | 2226篇 |
2008年 | 2912篇 |
2007年 | 2713篇 |
2006年 | 2587篇 |
2005年 | 2332篇 |
2004年 | 1992篇 |
2003年 | 1573篇 |
2002年 | 1681篇 |
2001年 | 1197篇 |
2000年 | 1004篇 |
1999年 | 634篇 |
1998年 | 458篇 |
1997年 | 431篇 |
1996年 | 459篇 |
1995年 | 351篇 |
1994年 | 351篇 |
1993年 | 340篇 |
1992年 | 323篇 |
1991年 | 254篇 |
1990年 | 186篇 |
1989年 | 178篇 |
1988年 | 176篇 |
1987年 | 144篇 |
1986年 | 113篇 |
1985年 | 187篇 |
1984年 | 119篇 |
1983年 | 108篇 |
1982年 | 126篇 |
1981年 | 94篇 |
1980年 | 88篇 |
1978年 | 97篇 |
1977年 | 90篇 |
1976年 | 101篇 |
1975年 | 104篇 |
1974年 | 84篇 |
1973年 | 108篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
121.
Recently, the theory of sortability of partition property has been shown to be an effective tool to prove the existence of an optimal partition with that property. In this paper, we extend the theory to multi-partition where the partition is on t types of components. We apply our results to settle an optimal assignment problem whose proof was incomplete as given in the literature. 相似文献
122.
Bing Yong HSIE 《数学学报(英文版)》2006,22(2):507-514
This paper gives a p-adic analogue of the Mackey theory, which relates representations of a group of type G - H × t A to systems of imprimitivity. 相似文献
123.
124.
125.
126.
Yu You George W. Kattawar Ping Yang Yong X. Hu Bryan A. Baum 《Journal of Quantitative Spectroscopy & Radiative Transfer》2006,100(1-3):470-482
Measurements from depolarized lidars provide a promising method to retrieve both cloud and aerosol properties and a versatile complement to passive satellite-based sensors. For lidar observations of clouds and aerosols, multiple scattering plays an important role in the scattering process. Monte Carlo simulations are carried out to investigate the sensitivity of lidar backscattering depolarization to cloud and aerosol properties. Lidar parameters are chosen to be similar to those of the upcoming space-based CALIPSO lidar. Cases are considered that consist of a single cloud or aerosol layer, as well as a case in which cirrus clouds overlay different types of aerosols. It is demonstrated that besides thermodynamic cloud phase, the depolarized lidar signal may provide additional information on ice or aerosol particle shapes. However, our results show little sensitivity to ice or aerosol particle sizes. Additionally, for the case of multiple but overlapping layers involving both clouds and aerosols, the depolarized lidar contains information that can help identify the particle properties of each layer. 相似文献
127.
We apply a Bayesian approach to the problem of prediction in an unbalanced growth curve model using noninformative priors. Due to the complexity of the model, no analytic forms of the predictive densities are available. We propose both approximations and a prediction-oriented Metropolis-Hastings sampling algorithm for two types of prediction, namely the prediction of future observations for a new subject and the prediction of future values for a partially observed subject. They are illustrated and compared through real data and simulation studies. Two of the approximations compare favorably with the approximation in Fearn (1975, Biometrika, 62, 89–100) and are very comparable to the more accurate Rao-Blackwellization from Metropolis-Hastings sampling algorithm. 相似文献
128.
129.
N.-K. Lee T.A. Vilgis 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(4):451-465
We study the elastic properties of single A/B random copolymer chains, with a specific sequence and use them as theoretical
model for so called HP proteins. HP proteins carry hydrophilic (P) and hydrophobic (H) monomers. We predict a rich structure
in the force-extension relations which can be attributed to the information in the sequence. The variational method is used
to probe local minima on the path of stretching and releasing for the chain molecules. At a given force, we find multiple
configurations which are separated by energy barriers. A collapsed globular configuration consists of several domains which
unravel cooperatively. Upon stretching, the unfolding path shows a stepwise pattern corresponding to the unfolding of each
domain. While releasing, several cores can be created simultaneously in the middle of the chain, resulting in a different
path of collapse. The long-range interactions and stiffness of the chain simplify the potential landscape given by the disorder
in sequence.
Received 5 March 2002 / Received in final form 16 May 2002 Published online 13 August 2002 相似文献
130.
Myung-Soon Lee 《Applied Surface Science》2006,252(14):5019-5025
We prepared high quality Au(1 1 1) film on Si wafer through the spin coating and thermal decomposition of a gold ink, spin-coated-and-fired (SCAF) Au film. The X-ray measurements, XRD and pole-figure analysis, showed that the SCAF Au film has a (1 1 1) out-of-plane orientation with a random in-plane orientation. In order to confirm the chemical activity of the SCAF Au film, we demonstrate the formation of patterned structures with the film by using soft lithography technique. The chemical activities of this physically stable SCAF Au film to the alkanethiols were at least equivalent those of physically deposited the Au films. The possibility of the mass production of micro patterned structure with the SCAF Au film was also demonstrated over the wide region on Si wafer by the microcontact lithography. These suggest that the Au film will help the easy fabrication of various nanosized devices on Si wafer and other substrates. 相似文献