全文获取类型
收费全文 | 794篇 |
免费 | 32篇 |
国内免费 | 3篇 |
专业分类
化学 | 587篇 |
晶体学 | 2篇 |
力学 | 10篇 |
数学 | 151篇 |
物理学 | 79篇 |
出版年
2023年 | 9篇 |
2022年 | 9篇 |
2021年 | 26篇 |
2020年 | 30篇 |
2019年 | 27篇 |
2018年 | 11篇 |
2017年 | 13篇 |
2016年 | 27篇 |
2015年 | 27篇 |
2014年 | 27篇 |
2013年 | 43篇 |
2012年 | 68篇 |
2011年 | 56篇 |
2010年 | 32篇 |
2009年 | 32篇 |
2008年 | 38篇 |
2007年 | 41篇 |
2006年 | 42篇 |
2005年 | 43篇 |
2004年 | 39篇 |
2003年 | 30篇 |
2002年 | 23篇 |
2001年 | 7篇 |
2000年 | 6篇 |
1998年 | 5篇 |
1997年 | 11篇 |
1996年 | 8篇 |
1995年 | 5篇 |
1994年 | 8篇 |
1993年 | 4篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1987年 | 4篇 |
1985年 | 5篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1978年 | 4篇 |
1973年 | 3篇 |
1967年 | 2篇 |
1939年 | 2篇 |
1935年 | 2篇 |
1933年 | 2篇 |
1931年 | 2篇 |
1925年 | 2篇 |
1923年 | 2篇 |
1918年 | 3篇 |
1917年 | 2篇 |
1915年 | 2篇 |
排序方式: 共有829条查询结果,搜索用时 640 毫秒
41.
Michaela Kohlov Susana Rocha Clia Gomes Amorim Alberto de Nova Araújo Alice Santos‐Silva Petr Solich Maria Conceio Branco da Silva Montenegro 《Macromolecular bioscience》2020,20(7)
The reduction of free radicals by bioactive membranes used for hemodialysis treatment is an important topic due to the constant rise of oxidative stress‐associated cardiovascular mortality by hemodialysis patients. Therefore, it is urgent to find an effective solution that helps to solve this problem. Polysulfone membranes enriched with α‐lipoic acid, α‐tocopherol, and with both components are fabricated by spin coating. The antioxidant properties of these membranes are evaluated in vitro by determining the lipid‐peroxidation level and the total antioxidant status of the blood plasma. The biocompatibility is assessed by quantifying the protein adsorption, platelet adhesion, complement activation, and hemolytic effect. All types of membranes show in vitro antioxidant activity and a trend to reduce oxidative stress in vivo; the best results show membranes prepared with a combination of both compounds and prove to be nonhemolytic and hemocompatible. Moreover, the membrane specific separation ability for the main waste products is not affected by antioxidants incorporation. 相似文献
42.
Dedicated to the memory of Paul Erdős
A graph is called -free if it contains no cycle of length four as an induced subgraph. We prove that if a -free graph has n vertices and at least edges then it has a complete subgraph of vertices, where depends only on . We also give estimates on and show that a similar result does not hold for H-free graphs––unless H is an induced subgraph of . The best value of is determined for chordal graphs.
Received October 25, 1999
RID="*"
ID="*" Supported by OTKA grant T029074.
RID="**"
ID="**" Supported by TKI grant stochastics@TUB and by OTKA grant T026203. 相似文献
43.
Background
There is fMRI evidence that women are neurally predisposed to process infant laughter and crying. Other findings show that women might be more empathic and sensitive than men to emotional facial expressions. However, no gender difference in the brain responses to persons and unanimated scenes has hitherto been demonstrated. 相似文献44.
45.
Alice?FialowskiEmail author Martin?Schlichenmaier 《Communications in Mathematical Physics》2005,260(3):579-612
We construct algebraic-geometric families of genus one (i.e. elliptic) current and affine Lie algebras of Krichever-Novikov
type. These families deform the classical current, respectively affine Kac-Moody Lie algebras. The construction is induced
by the geometric process of degenerating the elliptic curve to singular cubics. If the finite-dimensional Lie algebra defining
the infinite dimensional current algebra is simple then, even if restricted to local families, the constructed families are
non-equivalent to the trivial family. In particular, we show that the current algebra is geometrically not rigid, despite
its formal rigidity. This shows that in the infinite dimensional Lie algebra case the relations between geometric deformations,
formal deformations and Lie algebra two-cohomology are not that close as in the finite-dimensional case. The constructed families
are e.g. of relevance in the global operator approach to the Wess-Zumino-Witten-Novikov models appearing in the quantization
of Conformal Field Theory. The algebras are explicitly given by generators and structure equations and yield new examples
of infinite dimensional algebras of current and affine Lie algebra type. 相似文献
46.
47.
48.
We show that the formation of a vortex lattice in a weakly interacting Bose condensed gas can be modeled with the nonlinear Schr?dinger equation for both T=0 and finite temperatures without the need for an explicit damping term. Applying a weak rotating anisotropic harmonic potential, we find numerically that the turbulent dynamics of the field produces an effective dissipation of the vortex motion and leads to the formation of a lattice. For T=0, this turbulent dynamics is triggered by a rotational dynamic instability of the condensate. For finite temperatures, noise is present at the start of the simulation and allows the formation of a vortex lattice at a lower rotation frequency, the Landau frequency. These two regimes have different vortex dynamics. We show that the multimode interpretation of the classical field is essential. 相似文献
49.
50.
Low-power laser irradiation improves histomorphometrical parameters and bone matrix organization during tibia wound healing in rats 总被引:7,自引:0,他引:7
Garavello-Freitas I Baranauskas V Joazeiro PP Padovani CR Dal Pai-Silva M da Cruz-Höfling MA 《Journal of photochemistry and photobiology. B, Biology》2003,70(2):81-89
The influence of daily energy doses of 0.03, 0.3 and 0.9 J of He-Ne laser irradiation on the repair of surgically produced tibia damage was investigated in Wistar rats. Laser treatment was initiated 24 h after the trauma and continued daily for 7 or 14 days in two groups of nine rats (n=3 per laser dose and period). Two control groups (n=9 each) with injured tibiae were used. The course of healing was monitored using morphometrical analysis of the trabecular area. The organization of collagen fibers in the bone matrix and the histology of the tissue were evaluated using Picrosirius-polarization method and Masson's trichrome. After 7 days, there was a significant increase in the area of neoformed trabeculae in tibiae irradiated with 0.3 and 0.9 J compared to the controls. At a daily dose of 0.9 J (15 min of irradiation per day) the 7-day group showed a significant increase in trabecular bone growth compared to the 14-day group. However, the laser irradiation at the daily dose of 0.3 J produced no significant decrease in the trabecular area of the 14-day group compared to the 7-day group, but there was significant increase in the trabecular area of the 15-day controls compared to the 8-day controls. Irradiation increased the number of hypertrophic osteoclasts compared to non-irradiated injured tibiae (controls) on days 8 and 15. The Picrosirius-polarization method revealed bands of parallel collagen fibers (parallel-fibered bone) at the repair site of 14-day-irradiated tibiae, regardless of the dose. This organization improved when compared to 7-day-irradiated tibiae and control tibiae. These results show that low-level laser therapy stimulated the growth of the trabecular area and the concomitant invasion of osteoclasts during the first week, and hastened the organization of matrix collagen (parallel alignment of the fibers) in a second phase not seen in control, non-irradiated tibiae at the same period. The active osteoclasts that invaded the regenerating site were probably responsible for the decrease in trabecular area by the fourteenth day of irradiation. 相似文献