首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   317篇
  免费   3篇
化学   89篇
力学   1篇
数学   6篇
物理学   224篇
  2021年   1篇
  2020年   1篇
  2018年   1篇
  2017年   1篇
  2015年   2篇
  2014年   3篇
  2013年   2篇
  2012年   13篇
  2011年   26篇
  2010年   13篇
  2009年   5篇
  2008年   24篇
  2007年   34篇
  2006年   27篇
  2005年   16篇
  2004年   17篇
  2003年   14篇
  2002年   13篇
  2001年   8篇
  2000年   3篇
  1999年   3篇
  1998年   1篇
  1997年   1篇
  1996年   1篇
  1994年   2篇
  1993年   8篇
  1992年   3篇
  1991年   6篇
  1990年   4篇
  1989年   3篇
  1987年   1篇
  1986年   2篇
  1985年   7篇
  1984年   4篇
  1983年   3篇
  1982年   4篇
  1981年   3篇
  1980年   4篇
  1979年   4篇
  1978年   3篇
  1977年   5篇
  1976年   8篇
  1975年   4篇
  1974年   5篇
  1973年   4篇
  1966年   1篇
  1922年   1篇
  1895年   1篇
排序方式: 共有320条查询结果,搜索用时 0 毫秒
301.
We present the results of a search for new physics in the jets plus missing transverse energy data sample collected from 368 pb(-1) of pp collisions at square root of s = 1.96 TeV recorded by the Collider Detector at Fermilab. We compare the number of events observed in the data with a data-based estimate of the standard model backgrounds contributing to this signature. We observe no significant excess of events, and we interpret this null result in terms of lower limits on the fundamental Planck scale for a large extra dimensions scenario.  相似文献   
302.
We present a measurement of the W-boson mass using 200 pb{-1} of data collected in pp[over ] collisions at sqrt[s]=1.96 TeV by the CDF II detector at run II of the Fermilab Tevatron. With a sample of 63 964 W-->enu candidates and 51 128 W-->munu candidates, we measure M_{W}=80 413+/-34{stat}+/-34{syst}=80,413+/-48 MeV/c;{2}. This is the most precise single measurement of the W-boson mass to date.  相似文献   
303.
Let K   be an algebraic number field. We discuss the problem of counting the number of integral ideals below a given norm and obtain effective error estimates. The approach is elementary and follows a classical line of argument of Dedekind and Weber. The novelty here is that explicit error estimates can be obtained by fine tuning this classical argument without too much difficulty. The error estimate is sufficiently strong to give the analytic continuation of the Dedekind zeta function to the left of the line R(s)=1R(s)=1 as well as explicit bounds for the residue of the zeta function at s=1s=1.  相似文献   
304.
The structure of the [Pb(UMP)-H](+) (UMP = uridine-5'-monophosphate) complex was studied in the gas phase by combining electrospray ionization (ESI), tandem mass spectrometry, and mid-infrared multiple photon dissociation (IRMPD) spectroscopy. The results obtained show that Pb(2+) ions interact not only with the deprotonated phosphate group but also with a carbonyl group of the nucleobase moiety by folding of the mononucleotide, resulting in macrochelates that are not likely to be present in solution. Comparison between the IRMPD and DFT-computed spectra suggests that the ESI-generated complex likely corresponds to a mixture of several structures, and establishes the enolic tautomers as the most abundant species for the [Pb(UMP)-H](+) ion, while the very weak IRMPD signal observed at ~1763 cm(-1) points to a minor population of oxo forms. Our data also suggest that losing the nucleobase residue under CID conditions does not necessarily mean a lack of interaction between the metal and the nucleobase moiety, as commonly reported in the literature for large oligonucleotides.  相似文献   
305.
A search for new dielectron-mass resonances using data recorded by the CDF II detector and corresponding to an integrated luminosity of 5.7 fb(-1) is presented. No significant excess over the expected standard model prediction is observed. In this data set, an event with the highest dielectron mass ever observed (960 GeV/c(2)) was recorded. The results are interpreted in the Randall-Sundrum (RS) model. Combined with the 5.4 fb(-1) diphoton analysis, the RS-graviton lower-mass limit for the coupling k/Mˉ(Pl)=0.1 is 1058 GeV/c(2), making it the strongest limit to date.  相似文献   
306.
We reconstruct the rare decays B(+)→K(+)μ(+0μ(-0, B90)→K*(892)(0)μ(+)μ(-), and B(s)(0)→?(1020)μ(+)μ(-) in a data sample corresponding to 4.4 fb(-1) collected in pp collisions at √[s]=1.96 TeV by the CDF II detector at the Tevatron Collider. Using 121±16 B(+)→K(+)μ(+)μ(-) and 101±12 B(0)→K(*0)μ(+)μ(-) decays we report the branching ratios. In addition, we report the differential branching ratio and the muon forward-backward asymmetry in the B(+) and B(0) decay modes, and the K(*0) longitudinal polarization fraction in the B(0) decay mode with respect to the squared dimuon mass. These are consistent with the predictions, and most recent determinations from other experiments and of comparable accuracy. We also report the first observation of the B(s)(0)→?μ(+)μ(-) decay and measure its branching ratio BR(B(s)(0)→?μ(+)μ(-))=[1.44±0.33±0.46]×10(-6) using 27±6 signal events. This is currently the most rare B(s)(0) decay observed.  相似文献   
307.
We present a measurement of the B(s)(0) lifetime in fully and partially reconstructed B(s)(0)→D(s)(-)(?π(-))X decays in 1.3 fb(-1) collected in pp ˉ collisions at √s=1.96 TeV by the CDF II detector at the Fermilab Tevatron. We measure τ(B(s)(0))=1.518±0.041(stat)±0.027(syst) ps. The ratio of this result and the world average B(0) lifetime yields τ(B(s)(0))/τ(B(0))=0.99±0.03, which is in agreement with recent theoretical predictions.  相似文献   
308.
Secreted frizzled related protein-1 (SFRP1) plays a key role in many diverse processes, including embryogenesis, tissue repair, bone formation, and tumor genesis. Previous studies have shown the effects of the SFRP1 gene on lung development using the SFRP1 knockout mouse model via histological and physiological studies. In this study, the feasibility of ADC (acquired via HP 3He) to detect altered lung structure in the SFRP1 knockout (SFRP1−/−) mice was investigated, and compared to analysis by histology. This study consisted of two groups, the wild-type (WT) mice and the knockout (KO) mice with n = 6 mice for each group. 3He ADC MRI and histology were performed on all of the animals. The global Lm values of WT and KO mice were 35.0 ± 0.8 μm and 38.4 ± 3.8 μm, respectively, which translated to an increase of 9.58% in the Lm of KO mice. The mean global ADCs for the WT and KO mice were 0.12 ± 0.01 cm2/s and 0.13 ± 0.01 cm2/s, respectively, which equated to a relative increase of 8.0% in the KO mice compared to the WT mice. In the sub-analysis of the anterior, medial and posterior lung regions, Lm increased by 10.50%, 6.66% and 11.84% in the KO mice, respectively, whereas the differences in ADC between the two groups in the anterior, medial, and posterior regions were 7.3%, 8.3%, and 4.6%, respectively. These results suggest that HP MRI measurements can be used as a suitable substitute for histology to obtain valuable information about lung geometry non-invasively. This technique is also advantageous as regional measurements can be performed, which can identify lung destruction more precisely. Most importantly, this approach extends far beyond the specific pathology analyzed in this study, as it can be applied to many other pathological conditions in the lung tissue, as well to many other embryonic studies.  相似文献   
309.
The science of granular matter has expanded from an activity for specialised engineering applications to a fundamental field in its own right. This has been accompanied by an explosion of research and literature, which cannot be reviewed in one paper. A key to progress in this field is the formulation of a statistical mechanical formalism that could help develop equations of state and constitutive relations. This paper aims at reviewing some milestones in this direction. An essential basic step toward the development of any static and quasi-static theory of granular matter is a systematic and useful method to quantify the grain-scale structure and we start with a review of such a method. We then review and discuss the ongoing attempt to construct a statistical mechanical theory of granular systems. Along the way, we will clarify a number of misconceptions in the field, as well as highlight several outstanding problems.  相似文献   
310.
We report the results of a search for a charged Higgs boson in the decays of top quarks produced in pp collisions at a center-of-mass energy of 1.96 TeV. We use a data sample corresponding to an integrated luminosity of 193 pb-1 collected by the upgraded Collider Detector at Fermilab. No evidence for charged Higgs production is found, allowing 95% C.L. upper limits to be placed on BR(t-->H+b) for different charged Higgs decay scenarios. In addition, we present in the minimal supersymmetric standard model (mH+/-, tanbeta) plane the first exclusion regions with radiative and Yukawa coupling corrections.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号