全文获取类型
收费全文 | 6511篇 |
免费 | 189篇 |
国内免费 | 15篇 |
专业分类
化学 | 4911篇 |
晶体学 | 74篇 |
力学 | 75篇 |
综合类 | 2篇 |
数学 | 229篇 |
物理学 | 1424篇 |
出版年
2023年 | 33篇 |
2022年 | 49篇 |
2021年 | 58篇 |
2020年 | 89篇 |
2019年 | 100篇 |
2018年 | 78篇 |
2017年 | 44篇 |
2016年 | 132篇 |
2015年 | 145篇 |
2014年 | 129篇 |
2013年 | 298篇 |
2012年 | 314篇 |
2011年 | 377篇 |
2010年 | 202篇 |
2009年 | 232篇 |
2008年 | 370篇 |
2007年 | 394篇 |
2006年 | 358篇 |
2005年 | 357篇 |
2004年 | 302篇 |
2003年 | 264篇 |
2002年 | 252篇 |
2001年 | 130篇 |
2000年 | 138篇 |
1999年 | 102篇 |
1998年 | 73篇 |
1997年 | 61篇 |
1996年 | 100篇 |
1995年 | 66篇 |
1994年 | 64篇 |
1993年 | 80篇 |
1992年 | 77篇 |
1991年 | 74篇 |
1990年 | 65篇 |
1989年 | 64篇 |
1988年 | 60篇 |
1987年 | 71篇 |
1986年 | 57篇 |
1985年 | 101篇 |
1984年 | 95篇 |
1983年 | 51篇 |
1982年 | 71篇 |
1981年 | 63篇 |
1980年 | 62篇 |
1979年 | 67篇 |
1978年 | 54篇 |
1977年 | 39篇 |
1976年 | 44篇 |
1974年 | 32篇 |
1973年 | 40篇 |
排序方式: 共有6715条查询结果,搜索用时 15 毫秒
991.
M. Musha Y. Sato K. Nakagawa K. Ueda A. Ueda M. Ishiguro 《Applied physics. B, Lasers and optics》2006,82(4):555-559
We have developed an optical fiber length stabilization system for the distribution of reference millimeter wave signals in a long-baseline phased-array radio telescope. The fiber length was compared with an absolute wavelength reference laser using a Michelson interferometer. We used a digital servo system including a digital phase-frequency discriminator with a wide phase dynamic range and a digital signal processor (DSP) for the digital servo system. All-digital servo system made it possible to realize a robust and precise length stabilization of a 25-km long optical fiber. PACS 42.62.Eh; 42.81.Uv; 95.55.Jz 相似文献
992.
Allylic alcohols are chemoselectively oxidized to alpha,beta-unsaturated carbonyl compounds in high yield with aqueous H(2)O(2) in the presence of Pt black catalyst under organic solvent-free conditions. The catalyst is easily recyclable and effective for at least 7 cycles. 相似文献
993.
Rationality of Moduli Spaces of Parabolic Bundles 总被引:1,自引:0,他引:1
The moduli space of parabolic bundles with fixed determinantover a smooth curve of genus greater than one is proved to berational whenever one of the multiplicities of the quasi-parabolicstructure equals one. This gives a new proof that the modulispace of vector bundles of coprime rank and degree is stablyrational, a result originally due to Ballico, and the boundon the level is strong enough to deduce rationality in manycases, extending results of Newstead. 相似文献
994.
M. Matoba M. Hyakutake S. Nakamura T. Katayama T. Tonai K. Yagi K. Sato Y. Aoki 《Physics letters. [Part B]》1973,44(2):159-160
In the (p,p′) reaction on 130Te, strong excitation of the second 3? state was found at 3.36±0.01 MeV excitation energy. No strong second 3? state was observed in the (p,p′) reaction on 126Te. 相似文献
995.
Koji Matsuo 《Annals of Global Analysis and Geometry》1995,13(1):43-54
We introduce the notion of a locally conformally Hermitian-flat manifold and derive a necessary and sufficient condition for a Hermitian manifold to be locally conformally Hermitian-flat. In addition, we construct a family of examples. 相似文献
996.
One of the most challenging transformations in current organic chemistry is the catalytic carboxylation of a C(sp(3))-H bond using CO(2) gas, an inexpensive and ubiquitous C1 source. A sequential protocol for C(sp(3))-H carboxylation by employing a nitrogen-directed, metal-assisted, C-H activation/catalytic silylation reaction in conjunction with fluoride-mediated carboxylation with CO(2) was established. The carboxylation proceeded only at the benzylic C(sp(3))-Si bond, not at the aromatic C(sp(2))-Si, which is advantageous for further manipulations of the products. 相似文献
997.
998.
Drag reduction in spatially developing turbulent boundary layers by spatially intermittent blowing at constant mass-flux 总被引:1,自引:0,他引:1
Yukinori Kametani Koji Fukagata Ramis Örlü Philipp Schlatter 《Journal of Turbulence》2016,17(10):913-929
A series of large-eddy simulations of spatially developing turbulent boundary layers with uniform blowing at moderate Reynolds numbers (based on free-stream velocity, U∞, and momentum thickness, θ) up to Reθ ≈ 2500 were performed with the special focus on the effect of intermittent (separated in streamwise direction) blowing sections. The number of blowing sections, N, investigated is set to be 3, 6, 20, 30 and compared to N = 1, which constitutes the reference case, while the total wall-mass flux is constrained to be the same for all considered cases, corresponding to a blowing amplitude of 0.1% of U∞ for the reference case. Results indicate that the reference case provides a net-energy saving rate of around 18%, which initially decreases at most 2% points for N = 3 but recovers with increasing N, where the initial reduction of the drag reduction is found to be related to the shorter streamwise length of the intermittent blowing sections. The physical decomposition of the skin friction drag through the Fukagata-Iwamoto-Kasagi (FIK) identity shows that the distribution of all components over each blowing section has similar trends, resulting in similar averaged values over the whole control region. 相似文献
999.
M. Samiul Islam Sarker Takahiro Nakamura Yuliati Herbani Shunichi Sato 《Applied Physics A: Materials Science & Processing》2013,110(1):145-152
Many late transition binary alloy nanoparticles (NPs) have been fabricated through a wide variety of techniques. Various steps are involved in the fabrication of such NPs. Here, we used a simple and green route to fabricate solid-solution Rh–Pd and Rh–Pt bimetallic alloy NPs through femtosecond laser irradiation in a solution without any chemicals like reducing agents. X-ray diffraction (XRD) peaks of NPs obtained in the solutions with different ratios of Rh–Pd and Rh–Pt ions monotonically varied from the position of pure Rh to those of Pd and to Pt which respectively indicated that these NPs were alloy. Composition of fabricated NPs was fully tuned over the entire range of Rh1?x –Pd x , and Rh1?x –Pt x with varying the mixing ratio of metal ions in the solution. Studies of Rh–Pd and Rh–Pt solid-solution system suggest that the alloy formation occurs through the nucleation of Rh and then followed by the diffusion of Rh, Pd and Rh, Pt to form a homogeneous alloy. The variety of average size of the alloy NPs for different compositions could be attributed to different reduction rate and surface energies of metal ions. Our result implies that femtosecond laser irradiation in aqueous solution is one of the potential methodologies to form multimetallic solid-solution alloy NPs with fully tunable composition. 相似文献
1000.