全文获取类型
收费全文 | 5107篇 |
免费 | 231篇 |
国内免费 | 5篇 |
专业分类
化学 | 3678篇 |
晶体学 | 21篇 |
力学 | 126篇 |
数学 | 677篇 |
物理学 | 841篇 |
出版年
2023年 | 37篇 |
2022年 | 38篇 |
2021年 | 54篇 |
2020年 | 82篇 |
2019年 | 71篇 |
2018年 | 80篇 |
2017年 | 66篇 |
2016年 | 143篇 |
2015年 | 130篇 |
2014年 | 157篇 |
2013年 | 295篇 |
2012年 | 353篇 |
2011年 | 376篇 |
2010年 | 207篇 |
2009年 | 157篇 |
2008年 | 292篇 |
2007年 | 276篇 |
2006年 | 248篇 |
2005年 | 260篇 |
2004年 | 199篇 |
2003年 | 168篇 |
2002年 | 148篇 |
2001年 | 61篇 |
2000年 | 74篇 |
1999年 | 52篇 |
1998年 | 41篇 |
1997年 | 55篇 |
1996年 | 39篇 |
1995年 | 51篇 |
1994年 | 49篇 |
1993年 | 46篇 |
1992年 | 33篇 |
1991年 | 34篇 |
1990年 | 33篇 |
1989年 | 30篇 |
1987年 | 31篇 |
1986年 | 24篇 |
1985年 | 38篇 |
1984年 | 41篇 |
1983年 | 25篇 |
1982年 | 50篇 |
1981年 | 22篇 |
1980年 | 32篇 |
1979年 | 36篇 |
1978年 | 40篇 |
1977年 | 34篇 |
1976年 | 39篇 |
1975年 | 28篇 |
1960年 | 23篇 |
1959年 | 23篇 |
排序方式: 共有5343条查询结果,搜索用时 15 毫秒
1.
2.
3.
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
4.
5.
Roland Glowinski Jiwen He Jacques Rappaz Joël Wagner 《Comptes Rendus Mathematique》2003,337(10):679-684
In this paper we present a method to solve numerically elliptic problems with multi-scale data using multiple levels of not necessarily nested grids. The method consists in calculating successive corrections to the solution in patches whose discretizations are not necessarily conforming. It resembles the FAC method (see Math. Comp. 46 (174) (1986) 439–456) and its convergence is obtained by a domain decomposition technique (see Math. Comp. 57 (195) (1991) 1–21). However it is of much more flexible use in comparison to the latter. To cite this article: R. Glowinski et al., C. R. Acad. Sci. Paris, Ser. I 337 (2003). 相似文献
6.
G. Lujanienë 《Czechoslovak Journal of Physics》2003,53(1):A57-A65
In order to understand better the way in which radioactive contamination may be transferred from the atmosphere to other ecological compartments it is necessary to obtain information of the deposition mechanisms of radionuclides. Concentration and speciation of 137Cs and 7Be in the atmospheric aerosol and deposition were studied. The mixed deposition velocities of water-soluble and insoluble 137Cs and 7Be were determined. The relation between activity concentrations of insoluble 7Be in the atmosphere and its amount in deposition was observed. It is supposed that in the deposition process of radiocesium the precipitation plays an important role in scavenging of water-soluble radiocesium by falling raindrops, in contrast to insoluble 137Cs where the dry deposition becomes predominant. 相似文献
7.
Thomas Pautzsch Elisabeth Klemm 《Journal of polymer science. Part A, Polymer chemistry》2004,42(12):2911-2919
Poly{bis(4,4′‐tert‐butyl‐2,2′‐bipyridine)–(2,2′‐bipyridine‐5,5′‐diyl‐[1,4‐phenylene])–ruthenium(II)bishexafluorophosphate} ( 3a ), poly{bis(4,4′‐tert‐butyl‐2,2′‐bipyridine)–(2,2′‐bipyridine‐4,4′‐diyl‐[1,4‐phenylene])–ruthenium(II)bishexafluorophosphate} ( 3b ), and poly{bis(2,2′‐bipyridine)–(2,2′‐bipyridine‐5,5′‐diyl‐[1,4‐phenylene])–ruthenium(II)bishexafluorophosphate} ( 3c ) were synthesized by the Suzuki coupling reaction. The alternating structure of the copolymers was confirmed by 1H and 13C NMR and elemental analysis. The polymers showed, by ultraviolet–visible, the π–π* absorption of the polymer backbone (320–380 nm) and at a lower energy attributed to the d–π* metal‐to‐ligand charge‐transfer absorption (450 nm for linear 3a and 480 nm for angular 3b ). The polymers were characterized by a monomodal molecular weight distribution. The degree of polymerization was approximately 8 for polymer 3b and 28 for polymer 3d . © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2911–2919, 2004 相似文献
8.
Thomas Pautzsch Lars Blankenburg Elisabeth Klemm 《Journal of polymer science. Part A, Polymer chemistry》2004,42(3):722-732
A series of novel π-conjugated polymers containing ruthenium bipyridine complexes was synthesized by a cross-coupling reaction and characterized. These polymers exhibit absorption maxima around 330–350 nm (π-π*) and 460–500 nm metal-to-ligand charge transfer (MLCT), respectively. They are soluble in common organic solvents, and all polymers can be converted into transparent films. We investigated the influence of different donating and acceptor diethynylarenes of the ultraviolet-visible spectra. The oxidation potential, which was measured by cyclic- and square-wave voltametry, showed a typical Ru2+/3+ exhibited at 1.25 V versus the saturated calomel electrode. The polymers were further characterized with photoluminescence measurements. When excited at 442 nm ( 11a ), the polymer exhibited an emission peak at 690 nm. This peak was attributed to the MLCT states. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 722–732, 2004 相似文献
9.
10.
E. Goering M. Justen J. Geissler U. Rüdiger M. Rabe G. Güntherodt G. Schütz 《Applied Physics A: Materials Science & Processing》2002,74(6):747-753
Highly a-axis-textured CrO2 films have been deposited on Al2O3 (0001) substrates by chemical vapor deposition. CrO2 has been found to have highly a-axis (010)-oriented columnar growth on a Cr2O3 (0001) initial layer. The six-fold surface symmetry of the Cr2O3 initial layer leads to three equivalent in-plane orientations of the a-axis-oriented CrO2 unit cell. We report Cr L2,3 X-ray magnetic circular dichroism data along the surface normal and at 60° off-normal sample orientation. For a 60° sample
alignment, a strong increase of the projected orbital moment could be observed for unoccupied majority t2g states using moment analysis. Therefore, the c axis is identified as the intrinsic magnetic easy axis of CrO2. In addition, a small spin moment and a very strong magnetic dipole term Tz have been found.
Received: 8 January 2002 / Accepted: 8 January 2002 相似文献