全文获取类型
收费全文 | 2786篇 |
免费 | 108篇 |
国内免费 | 11篇 |
专业分类
化学 | 2173篇 |
晶体学 | 31篇 |
力学 | 36篇 |
数学 | 175篇 |
物理学 | 490篇 |
出版年
2023年 | 16篇 |
2022年 | 20篇 |
2021年 | 27篇 |
2020年 | 25篇 |
2019年 | 53篇 |
2018年 | 33篇 |
2017年 | 30篇 |
2016年 | 71篇 |
2015年 | 64篇 |
2014年 | 70篇 |
2013年 | 134篇 |
2012年 | 162篇 |
2011年 | 165篇 |
2010年 | 80篇 |
2009年 | 95篇 |
2008年 | 177篇 |
2007年 | 179篇 |
2006年 | 175篇 |
2005年 | 178篇 |
2004年 | 141篇 |
2003年 | 139篇 |
2002年 | 98篇 |
2001年 | 52篇 |
2000年 | 60篇 |
1999年 | 36篇 |
1998年 | 14篇 |
1997年 | 38篇 |
1996年 | 32篇 |
1995年 | 19篇 |
1994年 | 28篇 |
1993年 | 20篇 |
1992年 | 34篇 |
1991年 | 23篇 |
1990年 | 26篇 |
1989年 | 15篇 |
1988年 | 20篇 |
1987年 | 20篇 |
1986年 | 14篇 |
1985年 | 46篇 |
1984年 | 39篇 |
1983年 | 17篇 |
1982年 | 27篇 |
1981年 | 26篇 |
1980年 | 19篇 |
1979年 | 22篇 |
1978年 | 23篇 |
1977年 | 25篇 |
1976年 | 24篇 |
1975年 | 21篇 |
1974年 | 9篇 |
排序方式: 共有2905条查询结果,搜索用时 0 毫秒
1.
Kouichi Akahane Naokatsu Yamamoto Naoki Ohtani 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):295
We fabricated InAs quantum dots (QDs) with a GaAsSb strain-reducing layer (SRL) on a GaAs(0 0 1) substrate. The wavelength of emission from InAs QD is shown to be controllable by changing the composition and thickness of the SRL. An increase in photoluminescence intensity with increasing compositions of Sb and thickness of the GaAsSb SRL is also seen. The efficiency of radiative recombination was improved under both conditions because the InAs/GaAsSb/GaAs hetero-interface band structure more effectively suppressed carrier escape from the InAs QDs. 相似文献
2.
Ryoichi Kizu Naoki Otsuki Yoshiko Kishida Akira Toriba Atsushi Mizokami Kerry L Burnstein Carolyn M Klinge Kazuichi Hayakawai 《Analytical sciences》2004,20(1):55-59
We developed a new mammalian cell-based luciferase reporter gene assay for androgenic and antiandrogenic activities of chemicals and environmental samples. Environmental samples usually have a complex matrix that may contain the constituents acting as androgen receptor (AR) agonists, AR antagonists or aryl hydrocarbon receptor (AhR) agonists. AhR agonists are known to elicit the antiandrogenic effect through cross-talk between AR and AhR signal transduction pathways. In this study, PC3/AR human prostate carcinoma cells were transiently transfected with a prostate-specific antigen (PSA) promoter-driven luciferase expression plasmid. The cells were treated with a test compound or an environmental sample for 24 h at 37 degrees C and then measured for luciferase activity. The luciferase activity was induced by dihydrotestosterone (DHT) in a concentration-dependent manner in a concentration range from 10 fM to 1 nM. R1881, a synthetic androgen receptor agonist, induced luciferase activity and its inductive effects was additive to that of DHT. The luciferase activity was not induced by cortisol, a glucocorticoid, progesterone, a progestin, and 17beta-estradiol, an estrogen in a concentration range of up to 1 microM. DHT-induced luciferase activity was reduced by bicalutamide and cyproterone acetate, AR antagonists, and also by benzo[a]pyrene, an aryl hydrocarbon receptor agonist, through AhR-mediated pathways. All of these findings indicate that the present assay system correctly responds to AR agonists, AR antagonists and AhR agonist and, therefore, it is a powerful tool for the sensitive and selective screening of chemicals and environmental samples for their androgenic and antiandrogenic activities. We developed the first assay system, in which the expression of luciferase was driven by the promoter of a prostate-specific antigen gene, a typical human androgen-regulated gene. 相似文献
3.
Regularity of Harmonic Functions in Cheeger-Type Sobolev Spaces 总被引:3,自引:0,他引:3
We give a geometric approach to the study of the regularity of harmonic functions in Cheeger-type Sobolev spaces, and prove the Hölder continuity of such functions. In the proof, we give a definition of an upper curvature bound of the unit sphere of a Banach space, which seems to be of independent interest. 相似文献
4.
Naoki Miyamoto Shusuke Nisiyama Satoshi Tomioka Takeaki Enoto 《Optics Communications》2007,272(1):67-72
We utilize nitroanisole, that absorbs infrared (IR) radiation as heat, as an optical modulation device based on a thermal process. The nitroanisole exhibits a thermal lens effect, i.e. a temperature dependent refractive index. Hence, the nitroanisole can induce phase modulation to visible light, in direct response to intensity of the incident IR radiation. The proposed method can be used to obtain the phase modulation distribution that corresponds to the IR intensity distribution, i.e. the IR hologram itself, on the nitroanisole by examining the phase map of visible light that is modulated upon passing through the nitroanisole. The IR wavefront can be reconstructed by calculating extracted IR holograms through the Fresnel transform. It is verified that both the amplitude and the phase of the IR wavefront can be reconstructed accurately by proposed method. 相似文献
5.
This article concerns several geometric properties of metricmeasure spaces satisfying the measure contraction property (MCP),which can be considered as a generalized notion of lower Riccicurvature bounds. We prove that the MCP of spaces descends totheir products and Euclidean cones. We also show that a positivelycurved space in terms of the MCP with a maximal diameter canbe represented as the spherical suspension of some topologicalmeasure space. 相似文献
6.
7.
Nahoko Yamaji Manabu Horikawa Hideo Naoki Terumi Nakajima 《Tetrahedron letters》2004,45(28):5371-5373
A novel polyamine toxin, named MG30, was isolated from the venom of the spider, Macrothele gigas, and its structure was elucidated by two-dimensional NMR and mass analysis. In addition, the enantioselective synthesis of MG30 was achieved to assign its absolute stereochemistry. 相似文献
8.
Naoki Murabayashi 《Journal of Number Theory》2004,108(2):268-286
The purpose of this paper is to decide the conditions under which a CM elliptic curve is modular over its field of definition. 相似文献
9.
10.
Yue Liu Masahito Ohta Grozdena Todorova 《Annales de l'Institut Henri Poincaré (C) Analyse Non Linéaire》2007
We study here instability problems of standing waves for the nonlinear Klein–Gordon equations and solitary waves for the generalized Boussinesq equations. It is shown that those special wave solutions may be strongly unstable by blowup in finite time, depending on the range of the wave's frequency or the wave's speed of propagation and on the nonlinearity. 相似文献