全文获取类型
收费全文 | 2930篇 |
免费 | 85篇 |
国内免费 | 7篇 |
专业分类
化学 | 2155篇 |
晶体学 | 7篇 |
力学 | 24篇 |
数学 | 389篇 |
物理学 | 447篇 |
出版年
2023年 | 18篇 |
2022年 | 17篇 |
2021年 | 35篇 |
2020年 | 64篇 |
2019年 | 41篇 |
2018年 | 18篇 |
2017年 | 13篇 |
2016年 | 83篇 |
2015年 | 64篇 |
2014年 | 86篇 |
2013年 | 148篇 |
2012年 | 171篇 |
2011年 | 180篇 |
2010年 | 104篇 |
2009年 | 89篇 |
2008年 | 157篇 |
2007年 | 128篇 |
2006年 | 141篇 |
2005年 | 141篇 |
2004年 | 147篇 |
2003年 | 106篇 |
2002年 | 101篇 |
2001年 | 55篇 |
2000年 | 51篇 |
1999年 | 41篇 |
1998年 | 32篇 |
1997年 | 41篇 |
1996年 | 43篇 |
1995年 | 41篇 |
1994年 | 47篇 |
1993年 | 45篇 |
1992年 | 41篇 |
1991年 | 29篇 |
1990年 | 29篇 |
1989年 | 32篇 |
1988年 | 36篇 |
1987年 | 27篇 |
1985年 | 38篇 |
1984年 | 21篇 |
1983年 | 18篇 |
1982年 | 23篇 |
1981年 | 28篇 |
1980年 | 20篇 |
1979年 | 23篇 |
1978年 | 19篇 |
1977年 | 28篇 |
1976年 | 20篇 |
1975年 | 20篇 |
1973年 | 17篇 |
1970年 | 12篇 |
排序方式: 共有3022条查询结果,搜索用时 0 毫秒
41.
42.
Huebl H Stegner AR Stutzmann M Brandt MS Vogg G Bensch F Rauls E Gerstmann U 《Physical review letters》2006,97(16):166402
The hyperfine interaction of phosphorus donors in fully strained Si thin films grown on virtual Si(1-x)Ge(x) substrates with x< or =0.3 is determined via electrically detected magnetic resonance. For highly strained epilayers, hyperfine interactions as low as 0.8 mT are observed, significantly below the limit predicted by valley repopulation. Within a Green's function approach, density functional theory shows that the additional reduction is caused by the volume increase of the unit cell and a relaxation of the Si ligands of the donor. 相似文献
43.
The nowadays most accepted hypothesis of the origin of mental diseases is an impaired connectivity between various brain areas. Magnetic resonance tractography reveals structural connectivities through neuronal fibers and resting state functional imaging allows one to visualize functional connectivities. The detection of the small signal changes needs the highest sensitivity and the magnetic resonance imaging scans must be repeated as fast as possible. Statistical evaluation and cross correlation of the signals in all voxels show synchrony of signal-level fluctuations even in remote brain areas. This makes it possible to establish brain networks. The most important of them are the default mode network, the salience network, and the central executive network. Applications to schizophrenia and depression will be discussed. In deep brain stimulation, the excitation, currently used for therapy of Parkinson’s disease, is now introduced for therapy of major depressive disorder and can be taylored to the necessary brain location. 相似文献
44.
The hyperfine structure of the (v'-v") = (27-0) band of the b(3)Pi(u0(+)) <-- X(1)Sigma(+)(g) transition has been observed by laser excitation spectroscopy in a highly collimated molecular beam. Hyperfine parameters for magnetic dipole and electric quadrupole interaction are derived from least-squares fitting of the hyperfine pattern and deperturbation between A(1)Sigma(+)(u) and b(3)Pi(u0(+)). Copyright 2000 Academic Press. 相似文献
45.
Uwe Schobel Hans-Joachim Egelhaaf Dieter Fröhlich Andreas Brecht Dieter Oelkrug Günter Gauglitz 《Journal of fluorescence》2000,10(2):147
The cyanine dyes Cy5 and Cy5.5 are presented as a new long wavelength-excitable donor-acceptor dye pair for homogeneous fluoroimmunoassays. The deactivation pathways responsible for the quenching of the fluorescence of the antibody-bound donor are elucidated. Upon binding of the donor dye to the antibodies at low dye/protein ratios, its fluorescence quantum yield rises to unity. Higher dye/protein ratios lead to progressive aggregation of the dyes, which results in quenching of monomer fluorescence due to resonance energy transfer (RET) from the monomers to the nonfluorescent dimers. The dependence of the quenching efficiency on the labeling ratio is described quantitatively by assuming a Poisson distribution of the dyes over the antibodies. The maximum fluorescence intensity per antibody is obtained at a labeling ratio of 4. Upon formation of the antibody-antigen complex, electron transfer and RET to the antigen-bound acceptor dye occur. Steady-state and time-resolved fluorescence measurements reveal that approximately 50% of the donor quenching is due to RET, while the residual quenching effect is caused by the static quenching process. 相似文献
46.
We demonstrate a passively mode-locked femtosecond Yb:KLu(WO(4))(2) thin-disk laser oscillator. Chirped-pulse operation in the positive dispersion regime as well as solitary operation have been realized, and the laser performance of both configurations are compared. In the solitary mode-locking regime the output power exceeds 25 W in a diffraction-limited beam, and pulse durations as short as 440 fs at a 34.7 MHz repetition rate have been generated. For the first time we present a chirped-pulse operation of a thin-disk oscillator that yields a maximum average output power of 9.5 W with a Fourier limit of 450 fs. 相似文献
47.
Rodolfo Sánchez Angela Braeuning-Demian Jan Glorius Siegbert Hagmann Pierre-Michel Hillenbrand Anton Kalinin Thomas Köhler Yuri A. Litvinov Nikolaos Petridis Shahab Sanjari Uwe Spillmann Thomas Stöhlker 《X射线光谱测定》2020,49(1):33-36
The atomic physics collaboration SPARC is a part of the APPA pillar at the future Facility for Antiproton and Ion Research. It aims at atomic-physics research across virtually the full range of atomic matter. An emphasis of this contribution are the atomic physics experiments addressing the collision dynamics in strong electro-magnetic fields as well as the fundamental interactions between electrons and heavy nuclei at the HESR. Here we give a short overview about the central instruments for SPARC experiments at this storage ring. 相似文献
48.
A striking size dependence of the mean-square displacement of diffusing particles in the two-dimensional lattice gas of hard squares has been observed by Monte Carlo simulation. It is shown that the size effect is due to the formation of a stable cage structure in small lattices when the particle concentration is high. The formation of cages is governed by a new type of percolation problem related to bootstrap percolation. 相似文献
49.
The accumulation of the Jacobian matrix F of a vector function can be regarded as a transformation of its linearized computational graph into a subgraph of the directed complete bipartite graph Kn,m. This transformation can be performed by applying different elimination techniques that may lead to varying costs for computing F. This paper introduces face elimination as the basic technique for accumulating Jacobian matrices by using a minimal number of arithmetic operations. Its superiority over both edge and vertex elimination methods is shown. The intention is to establish the conceptual basis for the ongoing development of algorithms for optimizing the computation of Jacobian matrices. 相似文献
50.
Elisabeth Scheiner Kurt Hammerschmidt Uwe Jürgens Petra Zwirner 《Journal of voice》2002,16(4):509-529
The nonverbal vocal utterances of seven normally hearing infants were studied within their first year of life with respect to age- and emotion-related changes. Supported by a multiparametric acoustic analysis it was possible to distinguish one inspiratory and eleven expiratory call types. Most of the call types appeared within the first two months; some emerged in the majority of infants not until the 5th (“laugh”) or 7th month (“babble”). Age-related changes in acoustic structure were found in only 4 call types (“discomfort cry,” “short discomfort cry,” “wail,” “moan”). The acoustic changes were characterized mainly by an increase in harmonic-to-noise ratio and homogeneity of the call, a decrease in frequency range and a downward shift of acoustic energy from higher to lower frequencies. Emotion-related differences were found in the acoustic structure of single call types as well as in the frequency of occurrence of different call types. A change from positive to negative emotional state was accompanied by an increase in call duration, frequency range, and peak frequency (frequency with the highest amplitude within the power spectrum). Negative emotions, in addition, were characterized by a significantly higher rate of “crying,” “hic” and “ingressive vocalizations” than positive emotions, while positive emotions showed a significantly higher rate of “babble,” “laugh,” and “raspberry.” 相似文献