全文获取类型
收费全文 | 13571篇 |
免费 | 1214篇 |
国内免费 | 740篇 |
专业分类
化学 | 9321篇 |
晶体学 | 133篇 |
力学 | 532篇 |
综合类 | 52篇 |
数学 | 1609篇 |
物理学 | 3878篇 |
出版年
2023年 | 159篇 |
2022年 | 246篇 |
2021年 | 283篇 |
2020年 | 326篇 |
2019年 | 357篇 |
2018年 | 270篇 |
2017年 | 273篇 |
2016年 | 452篇 |
2015年 | 474篇 |
2014年 | 538篇 |
2013年 | 804篇 |
2012年 | 975篇 |
2011年 | 1106篇 |
2010年 | 723篇 |
2009年 | 731篇 |
2008年 | 860篇 |
2007年 | 802篇 |
2006年 | 713篇 |
2005年 | 624篇 |
2004年 | 573篇 |
2003年 | 487篇 |
2002年 | 439篇 |
2001年 | 350篇 |
2000年 | 296篇 |
1999年 | 219篇 |
1998年 | 173篇 |
1997年 | 152篇 |
1996年 | 190篇 |
1995年 | 143篇 |
1994年 | 166篇 |
1993年 | 130篇 |
1992年 | 127篇 |
1991年 | 108篇 |
1990年 | 113篇 |
1989年 | 86篇 |
1988年 | 99篇 |
1987年 | 63篇 |
1986年 | 71篇 |
1985年 | 99篇 |
1984年 | 70篇 |
1983年 | 73篇 |
1982年 | 55篇 |
1981年 | 50篇 |
1980年 | 54篇 |
1979年 | 38篇 |
1977年 | 41篇 |
1976年 | 43篇 |
1975年 | 37篇 |
1974年 | 53篇 |
1973年 | 50篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
A data-processing technique is proposed for use with conventional frequency-chirped absorption spectroscopy to ensure accurate mapping of spectral features into time-domain signatures with arbitrarily fast readout chirp rates. This technique recovers the spectrum from a signal that is distorted owing to the fast chirp rate and therefore facilitates fast measurement of the spectral features over a broad spectral range with high resolution. Both numerical simulations and experimental results are presented. 相似文献
982.
Tian XC Ban Y Abe K Abe K Aihara H Arinstein K Asano Y Aulchenko V Aushev T Bakich AM Banerjee S Barberio E Barbero M Bay A Bedny I Bitenc U Bizjak I Blyth S Bondar A Bozek A Bracko M Brodzicka J Browder TE Chang P Chao Y Chen A Chen KF Chen WT Cheon BG Chistov R Choi SK Choi Y Choi YK Chuvikov A Dalseno J Danilov M Dash M Dong LY Drutskoy A Eidelman S Enari Y Fang F Fratina S Gabyshev N Gershon T Gokhroo G Golob B Gorisek A Haba J Hara T Hayasaka K Hayashii H Hazumi M Hokuue T Hoshi Y Hou S 《Physical review letters》2005,95(23):231801
Using 281 fb-1 of data from the Belle experiment recorded at or near the (4S) resonance, we have measured the rates of the "wrong-sign" decays D0 --> K+ pi- pi0 and D0 --> K+ pi- pi+ pi- relative to those of the Cabibbo-favored decays D0 --> K- pi+ pi0 and D0 --> K- pi+ pi+ pi-. These wrong-sign decays proceed via a doubly Cabibbo-suppressed amplitude or via D0-D0 mixing; the latter has not yet been observed. We obtain R(WS)(K pi pi0) = [0.229 +/- 0.015(stat)(+0.013)(-0.009)(syst)]% and R(WS)(K3pi) = [0.320 +/- 0.018(stat)(+0.018)(0.013)(syst)]%. The CP asymmetries are measured to be -0.006 +/- 0.053 and -0.018 +/- 0.044 for the K+ pi- pi0 and K+ pi- pi+ pi- final states, respectively. 相似文献
983.
Schüssler-Langeheine C Schlappa J Tanaka A Hu Z Chang CF Schierle E Benomar M Ott H Weschke E Kaindl G Friedt O Sawatzky GA Lin HJ Chen CT Braden M Tjeng LH 《Physical review letters》2005,95(15):156402
Strong resonant enhancements of the charge-order and spin-order superstructure-diffraction intensities in La1.8Sr0.2NiO4 are observed when x-ray energies in the vicinity of the Ni L2,3 absorption edges are used. The pronounced photon-energy and polarization dependences of these diffraction intensities allow for a critical determination of the local symmetry of the ordered spin and charge carriers. We found that not only the antiferromagnetic order but also the charge-order superstructure resides within the NiO2 layers; the holes are mainly located on in-plane oxygens surrounding a Ni2+ site with the spins coupled antiparallel in close analogy to Zhang-Rice singlets in the cuprates. 相似文献
984.
The ground-state energies and pairing gaps in dilute superfluid Fermi gases have now been calculated with the quantum Monte Carlo method without detailed knowledge of their wave functions. However, such knowledge is essential to predict other properties of these gases such as density matrices and pair distribution functions. We present a new and simple method to optimize the wave functions of quantum fluids using the Green's function Monte Carlo method. It is used to calculate the pair distribution functions and potential energies of Fermi gases over the entire regime from atomic Bardeen-Cooper-Schrieffer superfluid to molecular Bose-Einstein condensation, spanned as the interaction strength is varied. 相似文献
985.
It is demonstrated that ultrahigh-resolution angular measurement can be achieved via surface-plasmon-resonance excitation in which the phase difference between p- and s-polarized reflected waves is monitored as a function of the incidence angle. Resolutions down to 1.9 x 10(-6) deg are obtained by performing the measurements at optimal incident wavelengths. This represents an order of magnitude improvement compared with previously reported values. 相似文献
986.
Laveissière G Todor L Degrande N Jaminion S Jutier C Di Salvo R Van Hoorebeke L Alexa LC Anderson BD Aniol KA Arundell K Audit G Auerbach L Baker FT Baylac M Berthot J Bertin PY Bertozzi W Bimbot L Boeglin WU Brash EJ Breton V Breuer H Burtin E Calarco JR Cardman LS Cavata C Chang CC Chen JP Chudakov E Cisbani E Dale DS de Jager CW De Leo R Deur A d'Hose N Dodge GE Domingo JJ Elouadrhiri L Epstein MB Ewell LA Finn JM Fissum KG Fonvieille H Fournier G Frois B Frullani S Furget C Gao H Gao J 《Physical review letters》2004,93(12):122001
We report a virtual Compton scattering study of the proton at low c.m. energies. We have determined the structure functions P(LL)-P(TT)/epsilon and P(LT), and the electric and magnetic generalized polarizabilities (GPs) alpha(E)(Q2) and beta(M)(Q2) at momentum transfer Q(2)=0.92 and 1.76 GeV2. The electric GP shows a strong falloff with Q2, and its global behavior does not follow a simple dipole form. The magnetic GP shows a rise and then a falloff; this can be interpreted as the dominance of a long-distance diamagnetic pion cloud at low Q2, compensated at higher Q2 by a paramagnetic contribution from piN intermediate states. 相似文献
987.
Huang DJ Chang CF Jeng HT Guo GY Lin HJ Wu WB Ku HC Fujimori A Takahashi Y Chen CT 《Physical review letters》2004,93(7):077204
We present measurements of the spin and orbital magnetic moments of Fe3O4 by using SQUID and magnetic circular dichroism in soft x-ray absorption. The measurements show that Fe3O4 has a noninteger spin moment, in contrast to its predicted half-metallic feature. Fe3O4 also exhibits a large unquenched orbital moment. Calculations using the local density approximation including the Hubbard U method and the configuration interaction cluster-model suggest that strong correlations and spin-orbit interaction of the 3d electrons result in the noninteger spin and large orbital moments of Fe3O4. 相似文献
988.
We report a new high-frequency (>10 kHz) ac electrospray that is capable of generating micron-sized electroneutral drops. Unlike its dc counterpart, the drops are not ejected continuously from a sharp Taylor cone but intermittently from a resonating meniscus at the orifice. We attribute the resonant frequency to the capillary-inertia vibration time of the meniscus and the drop ejection to the Maxwell-Wagner electric stress at the drop tip, which is observed to reverse its direction across a crossover frequency. Above this frequency, the oppositely directed Maxwell-Wagner force causes the liquid to recede up the microneedle as an apparent electrowetting effect. 相似文献
989.
990.
[reaction: see text] The expedient synthesis of a library of kanamycin B analogues is reported. The revealed SAR will guide future designs in developing kanamycin-type aminoglycoside antibiotics against drug-resistant bacteria. 相似文献