全文获取类型
收费全文 | 181810篇 |
免费 | 17878篇 |
国内免费 | 12462篇 |
专业分类
化学 | 97656篇 |
晶体学 | 1902篇 |
力学 | 12326篇 |
综合类 | 704篇 |
数学 | 44201篇 |
物理学 | 55361篇 |
出版年
2024年 | 364篇 |
2023年 | 2124篇 |
2022年 | 3874篇 |
2021年 | 4005篇 |
2020年 | 4376篇 |
2019年 | 4120篇 |
2018年 | 13341篇 |
2017年 | 12879篇 |
2016年 | 10782篇 |
2015年 | 5934篇 |
2014年 | 6539篇 |
2013年 | 8449篇 |
2012年 | 13196篇 |
2011年 | 19746篇 |
2010年 | 12190篇 |
2009年 | 12231篇 |
2008年 | 13217篇 |
2007年 | 14553篇 |
2006年 | 6065篇 |
2005年 | 6134篇 |
2004年 | 5312篇 |
2003年 | 4991篇 |
2002年 | 3782篇 |
2001年 | 2588篇 |
2000年 | 2310篇 |
1999年 | 2294篇 |
1998年 | 1978篇 |
1997年 | 1752篇 |
1996年 | 1815篇 |
1995年 | 1534篇 |
1994年 | 1383篇 |
1993年 | 1150篇 |
1992年 | 1001篇 |
1991年 | 877篇 |
1990年 | 741篇 |
1989年 | 589篇 |
1988年 | 458篇 |
1987年 | 418篇 |
1986年 | 409篇 |
1985年 | 336篇 |
1984年 | 270篇 |
1983年 | 205篇 |
1982年 | 201篇 |
1981年 | 135篇 |
1980年 | 127篇 |
1979年 | 107篇 |
1978年 | 82篇 |
1976年 | 61篇 |
1975年 | 53篇 |
1973年 | 55篇 |
排序方式: 共有10000条查询结果,搜索用时 19 毫秒
91.
A pressure sensitive paint (PSP) measurement has been known as a pressure field measurement technique based on the oxygen quenching phenomenon of luminescence of specific luminophores. A PSP measurement was applied for pressure field measurement in a low-solidity circular cascade diffuser of a single-stage transonic centrifugal compressor with 5 in pressure ratio for HFC134a gas. The oxygen concentration was about 500 ppm. Ru (bath-phen) was adsorbed on a silica-gel thinlayer chromatography sheet, and the sheet was pasted onto the side-wall between the cascade vanes. A drastic change in luminescent intensity was recognized during a surge condition. Also the pressure variations based on luminescent intensity agreed well with the pressure fluctuations measured using a semiconductor pressure sensor with high-frequency-response. It was shown that a PSP measurement worked well to investigate the unsteady pressure fields in a circular cascade diffuser of a transonic centrifugal compressor. Moreover, the time response of PSP becomes clear as a problem to be overcome for the present. 相似文献
92.
Chunguang Du Hongyi Chen Shiqun Li 《量子光学学报》2006,12(B08):70-71
Recently, research on left-handed materials (LHMs) has attracted considerable attentions. The LHMs are a kind of metameterial which have negative permittivity and negative permeability, which lead to negative refractive index in a frequency range. The LHMs that have been available so far are in the microwave range and are usually composed of classical particles, such as split-ring resonators. Some quantum phenomena such as spontaneous emission of atoms in the LHMs which are considered to be 'classical background' have also been investigated. Many potential applications of LHMs have been proposed, such as superlenses which, in principle, can achieve arbitrary subwavelength resolution. 相似文献
93.
M. Di Valentin A. Bisol G. Agostini G. Giacometti D. Carbonera 《Applied magnetic resonance》2006,30(3-4):555-576
A comparative electron paramagnetic resonance (EPR) study has been performed on a series of structurally related molecular triads which undergo photoinduced electron transfer and differ one from the other in terms of the acceptor or donor moieties. The molecular triads, C-P-C60, TTF-P-C60 and C-P-PF, share the same free-base, tetraarylporphyrin (P) as the primary electron donor, which after light excitation initiates the electron transfer process, but differ either in terms of the electron acceptor (fullerene derivative, C60, versus fluorinated free-base porphyrin, PF), or in terms of the final electron donor (carotenoid polyene, C, versus tetrathiafulvalene, TTF). All these molecular triads can be considered artificial photosynthetic reaction centers in their ability to mimic several key properties of the reaction center primary photochemistry. Photoinduced charge separation and recombination have been followed by time-resolved EPR in a glass of 2-methyltetrahydrofuran and in the nematic phase of the uniaxial liquid crystal E-7. All the triads undergo photoinduced electron transfer, with the generation of charge-separated states in both the low-dielectric environment of the 2-methyl-tetrahydrofuran glass and in anisotropic E-7 medium. Different photochemical pathways have been recognized depending on the specific donor and acceptor moieties constituting the molecular triads. In the presence of the tetrathiafulvalene electron donor singlet- and triplet-initiated electron transfer routes are concurrently active. Recombination to the low-lying carotenoid triplet state occurs in the carotene-based triads, while singlet recombination is the only active route for the TTF-P-C60 triad, where a low-lying triplet state is lacking. Long-lived charge separation has been observed in the case of TTF-P-C60: about 8 μs for the singlet-born radical pair in the glassy isotropic matrix and about 7 μs for the triplet-born radical pair in the nematic phase of E-7. For all the molecular triads, a weak exchange interaction (J?1 G) between the electrons in the final spin-correlated radical pair has been evaluated by simulation of the EPR spectra, providing evidence for superexchange electronic interactions mediated by the tetraarylporphyrin bridge. 相似文献
94.
95.
Yasuyuki Kawahigashi 《Communications in Mathematical Physics》2002,226(2):269-287
We study the recent construction of subfactors by Rehren which generalizes the Longo–Rehren subfactors. We prove that if
we apply this construction to a non-degenerately braided subfactor N⊂M and α±-induction, then the resulting subfactor is dual to the Longo–Rehren subfactor M⊗M
opp⊂R arising from the entire system of irreducible endomorphisms of M resulting from αplusmn;-induction. As a corollary, we solve a problem on existence of braiding raised by Rehren negatively. Furthermore, we generalize
our previous study with Longo and Müger on multi-interval subfactors arising from a completely rational conformal net of factors
on S
1 to a net of subfactors and show that the (generalized) Longo–Rehren subfactors and α-induction naturally appear in this context.
Received: 11 September 2001 / Accepted: 7 October 2001 相似文献
96.
Julio Castellanos 《Mathematische Zeitschrift》2002,239(4):777-802
We consider complete ideals supported on finite sequences of infinitely near points, in regular local rings with dimensions
greater than two. We study properties of factorizations in Lipman special *-simple complete ideals. We relate it to a type
of proximity, linear proximity, of the points, and give conditions in order to have unique factorization. Several examples
are presented.
Received: 2 February 2000 / in final form: 14 March 2001 / Published online: 18 January 2002 相似文献
97.
A FUNDAMENTAL SOLUTION FOR THE LAPLACE OPERATOR ON THE QUATERNIONIC HEISENBERG GROUP 总被引:2,自引:0,他引:2
朱理 《数学物理学报(B辑英文版)》2002,22(3)
In this paper, the author studies the Laplace operator on the quaternionic Heisenberg group, construct a fundamental solution for it and use this solution to prove the Lp-boundedness and the weak (1-1) boundedness of certain singular convolution operators on the quaternionic Heisenberg group. 相似文献
98.
99.
100.
Claudia-Elisabeth Wulz 《Czechoslovak Journal of Physics》2002,52(3):C155-C170
The principal physics goals of the Compact Muon Solenoid experiment under construction at the Large Hadron Collider at CERN in Geneva are reviewed. Procedures to search for the Standard Model Higgs boson, supersymmetric Higgses and other supersymmetric particles are described. 相似文献