全文获取类型
收费全文 | 3491篇 |
免费 | 65篇 |
国内免费 | 13篇 |
专业分类
化学 | 1900篇 |
晶体学 | 24篇 |
力学 | 97篇 |
数学 | 501篇 |
物理学 | 1047篇 |
出版年
2021年 | 26篇 |
2020年 | 25篇 |
2019年 | 29篇 |
2018年 | 22篇 |
2017年 | 32篇 |
2016年 | 43篇 |
2015年 | 62篇 |
2014年 | 61篇 |
2013年 | 179篇 |
2012年 | 136篇 |
2011年 | 165篇 |
2010年 | 96篇 |
2009年 | 60篇 |
2008年 | 196篇 |
2007年 | 168篇 |
2006年 | 153篇 |
2005年 | 163篇 |
2004年 | 107篇 |
2003年 | 117篇 |
2002年 | 101篇 |
2001年 | 92篇 |
2000年 | 85篇 |
1999年 | 30篇 |
1998年 | 39篇 |
1997年 | 37篇 |
1996年 | 66篇 |
1995年 | 71篇 |
1994年 | 61篇 |
1993年 | 57篇 |
1992年 | 49篇 |
1991年 | 55篇 |
1990年 | 50篇 |
1989年 | 27篇 |
1988年 | 36篇 |
1987年 | 22篇 |
1986年 | 33篇 |
1985年 | 49篇 |
1984年 | 39篇 |
1983年 | 36篇 |
1982年 | 42篇 |
1981年 | 52篇 |
1980年 | 43篇 |
1979年 | 55篇 |
1978年 | 44篇 |
1977年 | 64篇 |
1976年 | 55篇 |
1975年 | 48篇 |
1974年 | 40篇 |
1973年 | 54篇 |
1972年 | 20篇 |
排序方式: 共有3569条查询结果,搜索用时 15 毫秒
231.
A vinyl-phenylsilane has been used as a masked vinyl organometallic for a cross coupling reaction with phenyl iodide to provide the cine substitution product in high yield. 相似文献
232.
Blake IM Krivokapic A Katterle M Anderson HL 《Chemical communications (Cambridge, England)》2002,(16):1662-1663
The crystal structure, near-infrared spectrum and electrochemistry of a quinoidal triply-linked porphyrin dimer are compared with those of its singly-linked precursor; fusing the two porphyrins planarizes the pi-system and reduces the optical HOMO-LUMO gap while increasing the gap between the first oxidation and reduction potentials. 相似文献
233.
Kubo K Akemoto M Anderson S Aoki T Araki S Bane KL Blum P Corlett J Dobashi K Emma P Frisch J Fukuda M Guo Z Hasegawa K Hayano H Higo T Higurashi A Honda Y Iimura T Imai T Jobe K Kamada S Karataev P Kashiwagi S Kim E Kobuki T Kotseroglou T Kurihara Y Kuriki M Kuroda R Kuroda S Lee T Luo X McCormick DJ McKee B Mimashi T Minty M Muto T Naito T Naumenko G Nelson J Nguyen MN Oide K Okugi T Omori T Oshima T Pei G Potylitsyn A Qin Q Raubenheimer T Ross M Sakai H Sakai I Schmidt F Slaton T Smith H 《Physical review letters》2002,88(19):194801
Electron beams with the lowest, normalized transverse emittance recorded so far were produced and confirmed in single-bunch-mode operation of the Accelerator Test Facility at KEK. We established a tuning method of the damping ring which achieves a small vertical dispersion and small x-y orbit coupling. The vertical emittance was less than 1% of the horizontal emittance. At the zero-intensity limit, the vertical normalized emittance was less than 2.8 x 10(-8) rad m at beam energy 1.3 GeV. At high intensity, strong effects of intrabeam scattering were observed, which had been expected in view of the extremely high particle density due to the small transverse emittance. 相似文献
234.
Abazov VM Abbott B Abdesselam A Abolins M Abramov V Acharya BS Adams DL Adams M Ahmed SN Alexeev GD Alves GA Amos N Anderson EW Arnoud Y Baarmand MM Babintsev VV Babukhadia L Bacon TC Baden A Baldin B Balm PW Banerjee S Barberis E Baringer P Barreto J Bartlett JF Bassler U Bauer D Bean A Beaudette F Begel M Belyaev A Beri SB Bernardi G Bertram I Besson A Beuselinck R Bezzubov VA Bhat PC Bhatnagar V Bhattacharjee M Blazey G Blessing S Boehnlein A Bojko NI Borcherding F Bos K Brandt A Breedon R 《Physical review letters》2002,88(17):171802
We have performed a search for scalar top quark (stop) pair production in the inclusive electron-muon-missing transverse energy final state, using a sample of pp events corresponding to 108.3 pb(-1) of data collected with the D0 detector at Fermilab. The search is done in the framework of the minimal supersymmetric standard model assuming that the sneutrino is the lightest supersymmetric particle. For the dominant decays of the lightest stop, t-->b chi+1 and t-->blnu, no evidence for signal is found. We derive cross-section limits as a function of stop ( t ), chargino ( chi+1), and sneutrino ( nu) masses. 相似文献
235.
Johannisson P Anderson D Marklund M Berntson A Forzati M Mårtensson J 《Optics letters》2002,27(12):1073-1075
The nonlinear effects of amplitude jitter and ghost pulse generation, which are present in strongly dispersion-managed optical communication systems can be suppressed by alternation of the phase of the bits. A physical explanation for this effect is given that shows that with suitably chosen phase modulations the processes that give rise to the nonlinear effects will counteract each other. 相似文献
236.
R.S. Disselkamp J.F. Kelly R.L. Sams G.A. Anderson 《Applied physics. B, Lasers and optics》2002,75(2-3):359-366
Optical feedback to the laser source in tunable diode laser spectroscopy (TDLS) is known to create intensity modulation noise
due to elatoning and optical feedback (i.e. multiplicative technical noise) that usually limits spectral signal-to-noise (S/N).
The large technical noise often limits absorption spectroscopy to noise floors 100-fold greater than the Poisson shot noise
limit due to fluctuations in the laser intensity. The high output powers generated from quantum cascade (QC) lasers, along
with their high gain, makes these injection laser systems especially susceptible to technical noise. In this article we discuss
a method of using optimal filtering to reduce technical noise. We have observed S/N enhancements ranging from ∼20% to a factor
of ∼50. The degree to which optimal filtering enhances S/N depends on the similarity between the Fourier components of the
technical noise and those of the signal, with lower S/N enhancements observed for more similar Fourier decompositions of the
signal and technical noise. We also examine the linearity of optimal filtered spectra in both time and intensity. This was
accomplished by creating a synthetic spectrum for the species being studied (CH4, N2O, CO2 and H2O in ambient air) utilizing line positions and linewidths with an assumed Voigt profile from a commercial database (HITRAN).
Agreement better than 0.036% in wavenumber and 1.64% in intensity (up to a 260-fold intensity ratio employed) was observed.
Our results suggest that rapid ex post facto digital optimal filtering can be used to enhance S/N for routine trace gas detection.
Received: 1 April 2002 / Revised version: 7 May 2002 / Published online: 21 August 2002
RID="*"
ID="*"Corresponding author. Fax: +1-509/376-6066, E-mail: robert.disselkamp@pnl.gov 相似文献
237.
Anderson HL 《Angewandte Chemie (International ed. in English)》2000,39(14):2451-2453
238.
Anderson MW Holmes SM Hanif N Cundy CS 《Angewandte Chemie (International ed. in English)》2000,39(15):2707-2710
239.
240.