全文获取类型
收费全文 | 4776篇 |
免费 | 134篇 |
国内免费 | 28篇 |
专业分类
化学 | 3249篇 |
晶体学 | 38篇 |
力学 | 105篇 |
数学 | 778篇 |
物理学 | 768篇 |
出版年
2023年 | 27篇 |
2022年 | 38篇 |
2021年 | 50篇 |
2020年 | 73篇 |
2019年 | 88篇 |
2018年 | 65篇 |
2017年 | 44篇 |
2016年 | 105篇 |
2015年 | 107篇 |
2014年 | 142篇 |
2013年 | 256篇 |
2012年 | 247篇 |
2011年 | 290篇 |
2010年 | 180篇 |
2009年 | 166篇 |
2008年 | 254篇 |
2007年 | 228篇 |
2006年 | 209篇 |
2005年 | 194篇 |
2004年 | 159篇 |
2003年 | 136篇 |
2002年 | 133篇 |
2001年 | 72篇 |
2000年 | 85篇 |
1999年 | 52篇 |
1998年 | 70篇 |
1997年 | 57篇 |
1996年 | 64篇 |
1995年 | 66篇 |
1994年 | 54篇 |
1993年 | 63篇 |
1992年 | 59篇 |
1991年 | 68篇 |
1990年 | 43篇 |
1989年 | 53篇 |
1988年 | 61篇 |
1987年 | 50篇 |
1986年 | 60篇 |
1985年 | 64篇 |
1984年 | 71篇 |
1983年 | 44篇 |
1982年 | 37篇 |
1981年 | 50篇 |
1980年 | 57篇 |
1979年 | 44篇 |
1978年 | 45篇 |
1977年 | 42篇 |
1976年 | 37篇 |
1975年 | 30篇 |
1974年 | 26篇 |
排序方式: 共有4938条查询结果,搜索用时 15 毫秒
1.
Nuclear Magnetic Resonance (NMR) was used to investigate the extrusion behaviour of PTFE pastes in a ram extruder. By means
of 1H-NMR imaging (MRI) it is possible to determine the local proton density and therefore, the local fluid concentration. The
19F-MRI provides the local solid concentration. Thus the local saturation and the local porosity can be calculated with the
information of the local fluid and solid concentration. Furthermore displacement profiles can be derived from NMR images by
means of correlation techniques without any preparation or marking of the pastes.
Received: 8 May 2000 Accepted: 1 May 2001 相似文献
2.
Matrix extensions and eigenvalue completions, the generic case 总被引:2,自引:0,他引:2
William Helton Joachim Rosenthal Xiaochang Wang 《Transactions of the American Mathematical Society》1997,349(8):3401-3408
In this paper we provide new necessary and sufficient conditions for the so-called eigenvalue completion problem.
3.
For the first time a comparative study of holographic recording in planarly oriented films of nematic and cholesteric azobenzene-containing polymers was performed. The influence of temperature and light intensity on the values of diffraction efficiencies of holographic gratings was investigated. The kinetics of grating relaxation at different temperatures was studied. It was shown that the helical supramolecular structure of cholesteric copolymer causes a significant decrease of the diffraction efficiency in comparison with the one observed for the nematic state of the homopolymer. 相似文献
4.
5.
E. Mathieu Y. Foucher P. Dellamonica J. P. Daures 《Methodology and Computing in Applied Probability》2007,9(3):389-397
In AIDS control, physicians have a growing need to use pragmatically useful and interpretable tools in their daily medical
taking care of patients. Semi-Markov process seems to be well adapted to model the evolution of HIV-1 infected patients. In
this study, we introduce and define a non homogeneous semi-Markov (NHSM) model in continuous time. Then the problem of finding
the equations that describe the biological evolution of patient is studied and the interval transition probabilities are computed.
A parametric approach is used and the maximum likelihood estimators of the process are given. A Monte Carlo algorithm is presented
for realizing non homogeneous semi-Markov trajectories. As results, interval transition probabilities are computed for distinct
times and follow-up has an impact on the evolution of patients.
相似文献
6.
Klaus Anderle Richard Birenheide Martin J. A. Werner Joachim H. Wendorff 《Liquid crystals》1991,9(5):691-699
Polarized light leads to an effective reorientation of the optic axis in the glassy state of liquid-crystalline side chain polymers containing azobenzene mesogenic groups, via a trans-cis and cis-trans isomerization. Using a combination of U V and IR dichroitic studies it is shown for copolymers consisting of chromophores (azobenzene) and non-chromophores (phenylbenzoate) that only the chromophores are reoriented by light as far as the glassy state is concerned. Individual chromophores are thus addressed by photoselection. Photoselection in the fluid nematic state, on the other hand, leads also to a reorientation of the non-chromophores. 相似文献
7.
8.
9.
In this paper one specifies the ergodic behavior of the 2D-stochastic Navier–Stokes equation by giving a Large Deviation Principle for the occupation measure for large time. It describes the exact rate of exponential convergence. The considered random force is non-degenerate and compatible with the strong Feller property. 相似文献
10.
Two bases of states are presented for modules of the graded parafermionic conformal field theory associated to the coset
. The first one is formulated in terms of the two fundamental (i.e., lowest-dimensional) parafermionic modes. In that basis, one can identify the completely reducible representations, i.e., those whose modules contain an infinite number of singular vectors; the explicit form of these vectors is also given. The second basis is a quasiparticle basis, determined in terms of a modified version of the
exclusion principle. A novel feature of this model is that none of its bases are fully ordered and this reflects a hidden structural
exclusion principle. 相似文献