全文获取类型
收费全文 | 1232篇 |
免费 | 57篇 |
国内免费 | 2篇 |
专业分类
化学 | 854篇 |
晶体学 | 12篇 |
力学 | 46篇 |
数学 | 103篇 |
物理学 | 276篇 |
出版年
2023年 | 15篇 |
2022年 | 15篇 |
2021年 | 17篇 |
2020年 | 29篇 |
2019年 | 27篇 |
2018年 | 27篇 |
2017年 | 16篇 |
2016年 | 36篇 |
2015年 | 35篇 |
2014年 | 26篇 |
2013年 | 55篇 |
2012年 | 83篇 |
2011年 | 84篇 |
2010年 | 50篇 |
2009年 | 29篇 |
2008年 | 70篇 |
2007年 | 59篇 |
2006年 | 54篇 |
2005年 | 49篇 |
2004年 | 37篇 |
2003年 | 39篇 |
2002年 | 32篇 |
2001年 | 15篇 |
2000年 | 17篇 |
1999年 | 13篇 |
1998年 | 7篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 12篇 |
1994年 | 15篇 |
1993年 | 18篇 |
1992年 | 14篇 |
1991年 | 14篇 |
1990年 | 8篇 |
1989年 | 7篇 |
1988年 | 11篇 |
1986年 | 7篇 |
1985年 | 13篇 |
1984年 | 8篇 |
1982年 | 11篇 |
1981年 | 9篇 |
1980年 | 17篇 |
1979年 | 19篇 |
1978年 | 23篇 |
1977年 | 20篇 |
1976年 | 6篇 |
1975年 | 17篇 |
1974年 | 9篇 |
1973年 | 17篇 |
1970年 | 6篇 |
排序方式: 共有1291条查询结果,搜索用时 46 毫秒
81.
The number of atoms trapped within the mode of an optical cavity is determined in real time by monitoring the transmission of a weak probe beam. Continuous observation of atom number is accomplished in the strong coupling regime of cavity quantum electrodynamics and functions in concert with a cooling scheme for radial atomic motion. The probe transmission exhibits sudden steps from one plateau to the next in response to the time evolution of the intracavity atom number, from N>or=3 to N=2-->1-->0 atoms, with some trapping events lasting over 1 s. 相似文献
82.
Carter EB Culver SL Fox PA Goode RD Ntai I Tickell MD Traylor RK Hoffman NW Davis JH 《Chemical communications (Cambridge, England)》2004,(6):630-631
The anions of the sweeteners saccharin and acesulfame form ionic liquids when paired with a variety of organic cations. 相似文献
83.
Because of dispersion in head-related transfer functions (HRTFs), the interaural time difference (ITD) varies with frequency. This physical effect ought to have consequences for the size or shape of the auditory image of broadband noise because different frequency regions of the noise have different ITDs. However, virtual reality experiments suggest that human listeners are insensitive to head-related dispersion. The experiments of this article test that suggestion by experiments that isolate dispersion from amplitude effects in the HRTF and attempt to optimize the opportunity for detecting it. Nevertheless, the experiments find that the only effect of dispersion is to shift the lateralization of the auditory image. This negative result is explained in terms of the cross-correlation function for head-dispersed noise. Although the broad-band cross-correlation function differs considerably from 1.0, the cross-correlation functions within bands characteristic of auditory filters do not. A detailed study of the lateralization shifts show that the experimental shifts can be successfully calculated as an average of stimulus ITDs as weighted by Raatgever's frequency-weighting function (Thesis, Delft, The Netherlands, 1980). 相似文献
84.
Bearden IG Beavis D Besliu C Blyakhman Y Budick B Bøggild H Chasman C Christensen CH Christiansen P Cibor J Debbe R Enger E Gaardhøje JJ Germinario M Hagel K Hansen O Holm A Holme AK Ito H Jakobsen E Jipa A Jundt F Jørdre JI Jørgensen CE Karabowicz R Keutgen T Kim EJ Kozik T Larsen TM Lee JH Lee YK Løvhøiden G Majka Z Makeev A McBreen B Mikelsen M Murray M Natowitz J Nielsen BS Norris J Olchanski K Olness J Ouerdane D Płaneta R Rami F Ristea C Röhrich D Samset BH Sandberg D Sanders SJ 《Physical review letters》2003,90(10):102301
We present ratios of the numbers of charged antihadrons to hadrons (pions, kaons, and protons) in Au+Au collisions at sqrt[s(NN)]=200 GeV as a function of rapidity in the range y=0-3. While the ratios at midrapidity are approaching unity, the K(-)/K(+) and p;/p ratios decrease significantly at forward rapidities. An interpretation of the results within the statistical model indicates a reduction of the baryon chemical potential from mu(B) approximately 130 MeV at y=3 to mu(B) approximately 25 MeV at y=0. 相似文献
85.
86.
In this paper, we construct a parallel image of the conventional Maxwell theory by replacing the observer-time by the proper-time of the source. This formulation is mathematically, but not physically, equivalent to the conventional form. The change induces a new symmetry group which is distinct from, but closely related to the Lorentz group, and fixes the clock of the source for all observers. The new wave equation contains an additional term (dissipative), which arises instantaneously with acceleration. This shows that the origin of radiation reaction is not the action of a charge on itself but arises from inertial resistance to changes in motion. This dissipative term is equivalent to an effective mass so that classical radiation has both a massless and a massive part. Hence, at the local level the theory is one of particles and fields but there is no self-energy divergence (nor any of the other problems). We also show that, for any closed system of particles, there is a global inertial frame and unique (invariant) global proper-time (for each observer) from which to observe the system. This global clock is intrinsically related to the proper clocks of the individual particles and provides a unique definition of simultaneity for all events associated with the system. We suggest that this clock is the historical clock of Horwitz, Piron, and Fanchi. At this level, the theory is of the action-at-a-distance type and the absorption hypothesis of Wheeler and Feynman follows from global conservation of energy. 相似文献
87.
Time-resolved differential transmission measurements of self-assembled In0.4Ga0.6As quantum dots clearly indicate a phonon bottleneck between the n = 2 and n = 1 electronic levels. The key to this observation is the generation of electrons in dots where there are no holes so that electron-hole scattering does not mask the bottleneck. We use a simple carrier capture model consisting of two capture configurations to explain the bottleneck signal and offer arguments to rule out other possible sources of the signal. 相似文献
88.
Bearden IG Bøggild H Boissevain J Christiansen PH Conin L Dodd J Erazmus B Esumi S Fabjan CW Ferenc D Franz A Gaardhøje JJ Hansen AG Hansen O Hardtke D van Hecke H Holzer EB Humanic TJ Hummel P Jacak BV Kaimi K Kaneta M Kohama T Kopytine M Leltchouk M Ljubicic A Lörstad B Maeda N Martin L Medvedev A Murray M Ohnishi H Paic G Pandey SU Piuz F Pluta J Polychronakos V Potekhin M Poulard G Reichhold D Sakaguchi A Schmidt-Sørensen J Simon-Gillo J Sondheim W Sugitate T Sullivan JP Sumi Y Willis WJ 《Physical review letters》2001,87(11):112301
Two-particle interferometry of positive kaons is studied in Pb+Pb collisions at mean transverse momenta
approximately 0.25 and 0.91 GeV/c. A three-dimensional analysis was applied to the lower p(T) data, while a two-dimensional analysis was used for the higher p(T) data. We find that the source-size parameters are consistent with the m(T) scaling curve observed in pion-correlation measurements in the same collisions, and that the duration time of kaon emission is consistent with zero within the experimental sensitivity. 相似文献
89.
Zachary Maddock 《Monatshefte für Mathematik》2010,121(3):167-186
The Takagi function τ(x) is a continuous non-differentiable function on the unit interval defined by Takagi in 1903. This paper studies level sets
L(y) = {x : τ(x) = y} of the Takagi function and bounds their Minkowski dimensions and Hausdorff dimensions above by 0.668. There exist level
sets with Minkowski dimension 1/2. The method of proof involves a multiscale analysis that relies upon the self-similarity
of τ(x) up to affine shifts. 相似文献
90.