全文获取类型
收费全文 | 862篇 |
免费 | 31篇 |
国内免费 | 1篇 |
专业分类
化学 | 601篇 |
晶体学 | 2篇 |
力学 | 7篇 |
数学 | 134篇 |
物理学 | 150篇 |
出版年
2023年 | 7篇 |
2022年 | 10篇 |
2021年 | 16篇 |
2020年 | 13篇 |
2019年 | 11篇 |
2018年 | 10篇 |
2017年 | 10篇 |
2016年 | 34篇 |
2015年 | 29篇 |
2014年 | 28篇 |
2013年 | 42篇 |
2012年 | 67篇 |
2011年 | 60篇 |
2010年 | 59篇 |
2009年 | 57篇 |
2008年 | 65篇 |
2007年 | 65篇 |
2006年 | 67篇 |
2005年 | 37篇 |
2004年 | 29篇 |
2003年 | 18篇 |
2002年 | 23篇 |
2001年 | 5篇 |
2000年 | 11篇 |
1999年 | 10篇 |
1998年 | 9篇 |
1997年 | 10篇 |
1996年 | 7篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1993年 | 13篇 |
1992年 | 2篇 |
1991年 | 7篇 |
1990年 | 8篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1977年 | 2篇 |
1975年 | 3篇 |
1972年 | 2篇 |
1968年 | 2篇 |
1943年 | 3篇 |
1941年 | 3篇 |
1928年 | 1篇 |
1927年 | 1篇 |
1926年 | 1篇 |
1922年 | 1篇 |
排序方式: 共有894条查询结果,搜索用时 359 毫秒
91.
The objective of the study is an analysis of lung ventilation during breathing under rest conditions and for high frequency
ventilation (HFV). The measurements include investigations of the flow using an endotracheal tube. A transparent model of
the upper human lung airways down to the 6th generation was generated, and the oscillatory flow through the branching network
was studied by DPIV. The method of refractive index matching of the fluid (water/glycerin) and the model (silicone) allows
an unobstructed view into the internal flow network. The mass flow rate and the frequency were adapted to the characteristic
flow parameters, the Reynolds- and the Womersley-number. The comparison of the results for normal breathing and HFV shows
that a mass exchange occurs for higher frequencies known as Pendelluft, which could not be seen during normal breathing. This
mass exchange between the daughter tubes is a consequence of the asymmetric impedance in the successive daughter branches.
The lung topology determines the local pressure loss in the model and therefore the local mass flow direction of the Pendelluft.
At higher frequencies we observed an increase in exchange between the daughter branches. The transformation of the velocity
profiles between inspiration and expiration suggests a net mass flow which is created into the model along the centerline
and the inner walls of the bifurcations. This flow is compensated with a net mass outflow to the trachea along the outer walls
of the branches. 相似文献
92.
93.
94.
95.
96.
Aubert B Bona M Boutigny D Couderc F Karyotakis Y Lees JP Poireau V Tisserand V Zghiche A Grauges E Palano A Chen JC Qi ND Rong G Wang P Zhu YS Eigen G Ofte I Stugu B Abrams GS Battaglia M Brown DN Button-Shafer J Cahn RN Charles E Gill MS Groysman Y Jacobsen RG Kadyk JA Kerth LT Kolomensky YG Kukartsev G Lynch G Mir LM Orimoto TJ Pripstein M Roe NA Ronan MT Wenzel WA Sanchez Pdel A Barrett M Ford KE Hart AJ Harrison TJ Hawkes CM Watson AT Held T Koch H Lewandowski B Pelizaeus M Peters K 《Physical review letters》2006,97(26):261803
We report measurements of the decays B(+)-->phiphiK(+) and B(0)-->phiphiK(0) using a sample of 231 x 10(6) BB pairs collected with the BABAR detector at the PEP-II asymmetric-energy B factory at the Stanford Linear Accelerator Center. The branching fractions are measured to be B(B(+)-->phiphiK(+))=(7.5+/-1.0(stat)+/-0.7(syst)) x 10(-6) and B(B(0)-->phiphiK(0))=(4.1(-1.4)(+1.7)(stat)+/-0.4(syst)) x 10(-6) for a phiphi invariant mass below 2.85 GeV/c(2). 相似文献
97.
Aubert B Bona M Boutigny D Couderc F Karyotakis Y Lees JP Poireau V Tisserand V Zghiche A Grauges E Palano A Chen JC Qi ND Rong G Wang P Zhu YS Eigen G Ofte I Stugu B Abrams GS Battaglia M Brown DN Button-Shafer J Cahn RN Charles E Gill MS Groysman Y Jacobsen RG Kadyk JA Kerth LT Kolomensky YG Kukartsev G Lynch G Mir LM Orimoto TJ Pripstein M Roe NA Ronan MT Wenzel WA del Amo Sanchez P Barrett M Ford KE Hart AJ Harrison TJ Hawkes CM Watson AT Held T Koch H Lewandowski B Pelizaeus M Peters K 《Physical review letters》2006,97(23):232001
We report the first observation of an excited singly charmed baryon Omega c* (css) in the radiative decay Omega c0gamma, where the Omega c0 baryon is reconstructed in the decays to the final states Omega(-)pi+, Omega(-)pi+pi0, Omega(-)pi+pi(-)pi+, and Xi(-)K(-)pi+pi+. This analysis is performed using a data set of 230.7 fb(-1) collected by the BABAR detector at the PEP-II asymmetric-energy B factory at the Stanford Linear Accelerator Center. The mass difference between the Omega c* and the Omega c0 baryons is measured to be 70.8+/-1.0(stat)+/-1.1(syst) MeV/c2. We also measure the ratio of inclusive production cross sections of Omega c* and Omega c0 in e+e(-) annihilation. 相似文献
98.
Aubert B Barate R Bona M Boutigny D Couderc F Karyotakis Y Lees JP Poireau V Tisserand V Zghiche A Grauges E Palano A Chen JC Qi ND Rong G Wang P Zhu YS Eigen G Ofte I Stugu B Abrams GS Battaglia M Brown DN Button-Shafer J Cahn RN Charles E Gill MS Groysman Y Jacobsen RG Kadyk JA Kerth LT Kolomensky YG Kukartsev G Lynch G Mir LM Orimoto TJ Pripstein M Roe NA Ronan MT Wenzel WA del Amo Sanchez P Barrett M Ford KE Harrison TJ Hart AJ Hawkes CM Morgan SE Watson AT Held T Koch H Lewandowski B 《Physical review letters》2006,97(21):211801
We report a measurement of the B-->pi l nu branching fraction based on 211 fb(-1) of data collected with the BABAR detector. We use samples of B0 and B+ mesons tagged by a second B meson reconstructed in a semileptonic or hadronic decay and combine the results assuming isospin symmetry to obtain B(B(0)-->pi- l+ nu) = (1.33+/-0.17stat+/-0.11syst) x 10(-4). We determine the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element absolute value V(ub) by combining the partial branching fractions measured in ranges of the momentum transfer squared and theoretical calculations of the form factor. Using a recent lattice QCD calculation, we find absolute value V(ub) = (4.5+/-0.5stat+/-0.3syst(+0.7) -0.5FF x 10(-3), where the last error is due to the normalization of the form factor. 相似文献
99.
Aubert B Barate R Bona M Boutigny D Couderc F Karyotakis Y Lees JP Poireau V Tisserand V Zghiche A Grauges E Palano A Chen JC Qi ND Rong G Wang P Zhu YS Eigen G Ofte I Stugu B Abrams GS Battaglia M Brown DN Button-Shafer J Cahn RN Charles E Gill MS Groysman Y Jacobsen RG Kadyk JA Kerth LT Kolomensky YG Kukartsev G Lynch G Mir LM Oddone PJ Orimoto TJ Pripstein M Roe NA Ronan MT Wenzel WA del Amo Sanchez P Barrett M Ford KE Harrison TJ Hart AJ Hawkes CM Morgan SE Watson AT Goetzen K Held T Koch H 《Physical review letters》2006,97(17):171803
The photon spectrum in B-->Xs gamma decay, where Xs is any strange hadronic state, is studied using a data sample of 88.5 x 10(6) e+ e- --> Upsilon(4S) --> BB decays collected by the BABAR experiment at the Stanford Linear Accelerator Center. The partial branching fraction, DeltaB(B --> Xs gamma) = (3.67+/-0.29(stat)+/-0.34(syst)+/-0.29(model)) x 10(-4), the first moment = 2.288+/-0.025+/-0.017+/-0.015 GeV, and the second moment E2(gamma) = 0.0328+/-0.0040+/-0.0023+/-0.0036 GeV2 are measured for the photon energy range 1.9 GeV < E gamma < 2.7 GeV. They are also measured for narrower E gamma ranges. The moments are then fit to recent theoretical calculations to extract the heavy quark expansion parameters m(b) and mu2(pi) and to extrapolate the partial branching fraction to E gamma > 1.6 GeV. In addition, the direct CP asymmetry A(CP)(B-->X(s+d gamma) is measured to be -0.110+/-0.115(stat)+/-0.017(syst). 相似文献
100.