全文获取类型
收费全文 | 11857篇 |
免费 | 1765篇 |
国内免费 | 3922篇 |
专业分类
化学 | 10582篇 |
晶体学 | 464篇 |
力学 | 1056篇 |
综合类 | 325篇 |
数学 | 1085篇 |
物理学 | 4032篇 |
出版年
2024年 | 86篇 |
2023年 | 341篇 |
2022年 | 473篇 |
2021年 | 484篇 |
2020年 | 379篇 |
2019年 | 457篇 |
2018年 | 280篇 |
2017年 | 390篇 |
2016年 | 435篇 |
2015年 | 511篇 |
2014年 | 834篇 |
2013年 | 691篇 |
2012年 | 709篇 |
2011年 | 755篇 |
2010年 | 663篇 |
2009年 | 663篇 |
2008年 | 755篇 |
2007年 | 698篇 |
2006年 | 753篇 |
2005年 | 723篇 |
2004年 | 695篇 |
2003年 | 708篇 |
2002年 | 614篇 |
2001年 | 643篇 |
2000年 | 472篇 |
1999年 | 451篇 |
1998年 | 396篇 |
1997年 | 336篇 |
1996年 | 338篇 |
1995年 | 337篇 |
1994年 | 281篇 |
1993年 | 233篇 |
1992年 | 253篇 |
1991年 | 200篇 |
1990年 | 178篇 |
1989年 | 164篇 |
1988年 | 53篇 |
1987年 | 34篇 |
1986年 | 23篇 |
1985年 | 19篇 |
1984年 | 15篇 |
1983年 | 14篇 |
1982年 | 2篇 |
1980年 | 2篇 |
1959年 | 2篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 656 毫秒
51.
52.
53.
54.
The solid-liquid interface motion of NaBi(WO4)2 (NBWO) melt crystal growth is observed in an in situ system, in which the whole processes of interface transition from fiat interface and cellular to dendrite are visualized. The spacing of the dendrite under smaller temperature gradient turns out to be larger than that under larger temperature gradient, which is found to be sensitive to the temperature distribution. The mechanism of dendrite growth of NBWO is studied based on the model of the growth units of anion coordination polyhedra. The { 001} face has two apex links, so it shows higher stability and has high growth rate and forms the arm of dendrite, whereas the {010} face has only one apex link, and thus shows relative slower growth rate and firstly forms the branches. 相似文献
55.
Entangled states based on two coherent states 3π/2 out of phase with each other, i.e. |α〉 and e^iФ|-iα〉, as well as on a special state with a relative phase Ф = |α|^2, are constructed. By analysing the amount of entanglement it is evident that entangled states based on this special state can be used as an excellent resource for quantum teleportation. It is also revealed that these entangled states possess some nonclassical features. 相似文献
56.
It is shown that the configuration of phase coding for quantum key distribution with single photon can also be used for continuous variable quantum key distribution. Therefore the robust long-distance high-speed quantum key distribution can be achieved with current technology. 相似文献
57.
氧碘化学激光气固相化学反应体系热力学分析 总被引:1,自引:1,他引:0
许正 《工程物理研究院科技年报》2004,(1):297-297
氧碘化学激光器(COIL)的发展已经到了提高系统安全性和工作环境适应性、降低系统复杂性阶段,而改进O2(^1△g)的产生方式和方法正是这个阶段的重要工作内容之一。近期,美国空军研究实验室运用气-固相反应方式产生O2(^1△g)。采用碱金属过氧化物或碱土金属过氧化物与卤化氢反应,生成O2(^1△g)。通常气一固相反应有着反应速度慢,接触面积小,反应产物难以脱出固体表面的缺陷,使得产出率低,而不被广泛采用。但随着表面化学研究的突飞猛进,借助表面活化分子,特殊性质的表面构造,大表面的构造,都为气一固相反应的进行提供了可行途径。如果此方法能用在氧碘激光器上,将克服传统方法的诸多不足。 相似文献
58.
实验研究了Bi-2212粉末在空气,8%O2和纯O2种处理的相组成特征,指出通过改变热处理温度和气氛可控制前驱粉中对2223成相影响较大的(Bi,Pb)-2212相,Ca2PbO4相,2201相和14:24AEC等相。 相似文献
59.
60.
Self-assembly behaviour of amphiphilic diblock copolymer in selective solvents studied by synchrotron small-angle x-ray scattering 下载免费PDF全文
The aggregation behaviour of styrene-vinyl benzoic acid (PSm-b-PVBAn) amphiphilic diblock copolymers in selective solvents with different m and n was investigated by synchrotron small-angle x-ray scattering (SAXS). We have carried out a detailed analysis of scattering intensity, dimension, shape and microstructure of the diblock copolymers of narrow distribution in water, methanol, ethanol and isopropanol selective solvents, respectively. We have found that the aggregation behaviour of the copolymer depends on the nature of the solvent and the micelle forms fiat disc objects with the ratio of radius ω=0.4. The average radius gyration Rg of the copolymer decreases as solvents change from isopropanol to ethanol and to methanol, and increases with increasing pH in aqueous solution, but decreases with the addition of COCl2 in ethanol solvent. The scattering intensity of diblock copolymer micelle follows I(h) ∝ h^-α in different selective solutions, suggesting that the PSm-b-PVBAn coils have self-similar structure behaviour or a fractal structure in the selective solvents. All of these revealed that the aggregation behaviour of the diblock copolymer changes dramatically with experimental condition in the selective solvent. The increase of mass fractal dimension (Dm) from 2.12 to 2.47 indicates that the copolymer chain changes from a swollen coil to a rather compact disc in the course of changing solvents, decreasing surface fractal dimension (Ds) from 2.98 to 2.58 indicates that the copolymer micelle change from a rather rough surface to a smooth form in the course of increasing pH in aqueous solutions, and increasing Dm and Ds from 2.29 to 2.35 and 2.70 to 2.90, respectively, indicates the shrinkage of copolymer micelle to a rather compact and rough disc form by adding COCl2 in ethanol solvents. 相似文献