全文获取类型
收费全文 | 8014篇 |
免费 | 774篇 |
国内免费 | 414篇 |
专业分类
化学 | 6059篇 |
晶体学 | 79篇 |
力学 | 249篇 |
综合类 | 46篇 |
数学 | 934篇 |
物理学 | 1835篇 |
出版年
2024年 | 10篇 |
2023年 | 88篇 |
2022年 | 103篇 |
2021年 | 174篇 |
2020年 | 202篇 |
2019年 | 257篇 |
2018年 | 189篇 |
2017年 | 170篇 |
2016年 | 331篇 |
2015年 | 306篇 |
2014年 | 399篇 |
2013年 | 550篇 |
2012年 | 625篇 |
2011年 | 715篇 |
2010年 | 500篇 |
2009年 | 397篇 |
2008年 | 570篇 |
2007年 | 446篇 |
2006年 | 447篇 |
2005年 | 413篇 |
2004年 | 320篇 |
2003年 | 280篇 |
2002年 | 312篇 |
2001年 | 193篇 |
2000年 | 147篇 |
1999年 | 112篇 |
1998年 | 89篇 |
1997年 | 66篇 |
1996年 | 78篇 |
1995年 | 66篇 |
1994年 | 63篇 |
1993年 | 56篇 |
1992年 | 47篇 |
1991年 | 64篇 |
1990年 | 51篇 |
1989年 | 32篇 |
1988年 | 28篇 |
1987年 | 24篇 |
1986年 | 16篇 |
1985年 | 34篇 |
1984年 | 17篇 |
1983年 | 13篇 |
1982年 | 17篇 |
1981年 | 22篇 |
1980年 | 12篇 |
1979年 | 17篇 |
1978年 | 12篇 |
1977年 | 17篇 |
1976年 | 12篇 |
1974年 | 10篇 |
排序方式: 共有9202条查询结果,搜索用时 15 毫秒
31.
有界连通区域上Dirichlet空间及其算子 总被引:1,自引:0,他引:1
本文主要讨论了有界连通区域Dirichlet空间上Toeplitz算子的Fredholm性质,计算了符号在C1中的Toeplitz算子的本性谱和Fredholm指标. 相似文献
32.
We investigate the connection between the entanglement system in Minkowski spacetime and the black hole using the scaling analysis. Here we show that the entanglement system satisfies the Bekenstein entropy bound. Even though the entropies of two systems are the same form, the entanglement energy is different from the black hole energy. Introducing the Casimir energy of the vacuum energy fluctuations rather than the entanglement energy, it shows a feature of the black hole energy. Hence the Casimir energy is more close to the black hole than the entanglement energy. Finally, we find that the entanglement system behaves like the black hole if the gravitational effects are included properly. 相似文献
33.
构造了第孙中禹种强度不等的非对称三态叠加多模叠加态光场|ψ1(ABC)〉q.利用多模压缩态理论研究了态|ψ1(ABC)〉q第一正交分量高次和压缩.结果发现:①当构成态|ψ1(ABC)〉q的三个多模相干态光场的强度不相等时,在一定条件下,态|ψ1(ABC)〉q的第一正交分量可出现任意幂次的高次和压缩.②当上述的三个多模相干态光场强度相等时,态|ψ1(ABC)〉q的第一正交分量的高次和压缩现象消失.在这种情况下,态|ψ1(ABC)〉q的第一正交分量恒处于NH最小测不准态. 相似文献
34.
Summary We study Sobolev space functions with prescribed growth properties on large spheres. In particular, we prove a weighted Poincaré
type inequality for such functions. An extension to weighted Sobolev spaces is sketched.
Sunto Si studiano funzioni che appartengono a certi spazi di Sobolev e che hanno crescita assegnata su sfere di grande raggio. Per tali funzioni si dimostra una disuguaglianza di tipo Poincaré con peso. Si indica inoltre anche una estensione di tale risultato a funzioni in spazi di Sobolev con peso.相似文献
35.
36.
本文借助文[1]除去零空间的技巧,利用L—S度数理论讨论了一类浙近线性波方程。在对非线性项不做单调性假设的前提下,给出了一个新的多解定理。 相似文献
37.
Kyung Hwa Hong Jong Lyoul Park In Hwan Sul Ji Ho Youk Tae Jin Kang 《Journal of Polymer Science.Polymer Physics》2006,44(17):2468-2474
Polyvinyl alcohol (PVA) nanofibers containing Ag nanoparticles were prepared by electrospinning PVA/silver nitrate (AgNO3) aqueous solutions, followed by short heat treatment, and their antimicrobial activity was investigated for wound dressing applications. Since PVA is a water soluble and biocompatible polymer, it is one of the best materials for the preparation of wound dressing nanofibers. After heat treatment at 155 °C for 3 min, the PVA/AgNO3 nanofibers became insoluble, while the Ag+ ions therein were reduced so as to produce a large number of Ag nanoparticles situated preferentially on their surface. The residual Ag+ ions were reduced by subsequent UV irradiation for 3 h. The average diameter of the Ag nanoparticles after the heat treatment was 5.9 nm and this value increased slightly to 6.3 nm after UV irradiation. It was found that most of the Ag+ ions were reduced by the simple heat treatment. The PVA nanofibers containing Ag nanoparticles showed very strong antimicrobial activity. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2468–2474, 2006 相似文献
38.
We consider the classical problem of searching for a heavier coin in a set of n coins, n-1 of which have the same weight. The weighing device is b-balance which is the generalization of two-arms balance. The minimum numbers of weighings are determined exactly for worst-case sequential algorithm, average-case sequential algorithm, worst-case predetermined algorithm, average-case predetermined algorithm.We also investigate the above search model with additional constraint: each weighing is only allowed to use the coins that are still in doubt. We present a worst-case optimal sequential algorithm and an average-case optimal sequential algorithm requiring the minimum numbers of weighings. 相似文献
39.
D. Liu Y. Li R. An Y. Dou H. Yang Q. Gong 《Applied Physics A: Materials Science & Processing》2006,84(3):257-260
We studied the influence of focusing depth on the index change threshold and damage threshold of silica glass irradiated by a focused 120 fs laser beam. Both thresholds increased with the focusing depth. The aspect ratio of the waveguide cross section can be selected by changing the focusing depth. A 5 mm long waveguide was written at the depth of 2100 μm, which was single mode at 632.8 nm and exhibited propagation loss of 0.56 dB/cm. The refractive index change was calculated to be ∼2.47×10-3. The influence of the focusing depth should be considered in multi-layer devices as shown in the fabrication of a 3×3 waveguide array. PACS 42.62.-b; 42.82.Et; 81.05.Kf 相似文献
40.