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   154篇
  免费   1篇
化学   68篇
晶体学   1篇
力学   4篇
物理学   82篇
  2022年   1篇
  2021年   1篇
  2018年   1篇
  2017年   2篇
  2016年   3篇
  2015年   1篇
  2014年   1篇
  2013年   5篇
  2012年   3篇
  2011年   6篇
  2010年   7篇
  2009年   3篇
  2008年   17篇
  2007年   22篇
  2006年   14篇
  2005年   15篇
  2004年   12篇
  2003年   7篇
  2002年   11篇
  2001年   3篇
  2000年   2篇
  1997年   1篇
  1996年   1篇
  1992年   2篇
  1990年   3篇
  1989年   1篇
  1988年   2篇
  1987年   2篇
  1986年   1篇
  1984年   1篇
  1983年   2篇
  1980年   1篇
  1975年   1篇
排序方式: 共有155条查询结果,搜索用时 31 毫秒
71.
Thermal recycling of recovered plastic resin has been investigated by supplying plastic resin powder as an additional fuel to the proposed twin-fuel industrial burner. The results emphasize the necessity of fundamental investigations, such as high-speed microscopic observations of micro plastic particles under abrupt heating. To observe the multiphase process of macro plastic particles under abrupt heating and to elucidate their combustion enhancement mechanism, some original devises are introduced; one for optical imaging and three for abrupt heating and ceasing. The former is a mini optical composite which enables simultaneous photographing of the direct silhouetted and schlieren images. The latter three are reforming of a rugged resin particle into a spherical one, a vertical type circular mini-burner for abrupt heating, and a mini-puff generator for abrupt extinguishment. Three types of fine supports made of tungsten, silicon-carbide, and quartz glass are used. Detailed optical observations clarify many characteristics concerning the multiphase process of plastic resin particles under abrupt heating, such as the occurrence of multiple internal micro bubbling, multiple micro explosions and jets. The burning rate constant is also estimated based on the temporal reduction rate of the particle surface area. It is found that the values obtained for three supporting wires are greater than those of typical liquid fuels, and that the key factor to the prominent enhancement rate of micro PET particle combustion can be attributed to the occurrence of the multiphase process particular to micro plastic particles.  相似文献   
72.
We present the first evidence of the decay B- --> tau- nu(tau), using 414 fb(-1) of data collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+ e- collider. Events are tagged by fully reconstructing one of the B mesons in hadronic modes. We detect the signal with a significance of 3.5 standard deviations including systematics and measure the branching fraction to be B(B- --> tau- nu(tau)) = (1.79(-0.49) +0.56(stat)(-0.51) +0.46(syst)) x 10(-4). This implies that fB = 0.229(-0.031) +0.036(stat)(-0.037) +0.034(syst) GeV and is the first direct measurement of this quantity.  相似文献   
73.
Summary: Precise syntheses of soluble star polymers containing a sugar residue could be attained by adopting sequential ring-opening metathesis polymerizations of norbornene, 1,4,4a,5,8,8a-hexahydro-1,4,5,8-exo-endo-dimethanonaphtalene, and then 1,2:3,4-di-O-isopropylidene-α-D-galacto-pyranos-6-O-yl 5-norbornene-2-carboxylate using Mo(CHCMe2Ph)(N-2,6-iPr2C6H3)(OtBu)2. The resultant polymers possessed uniform molecular weight distributions, and the Mn values could be varied by the monomer/Mo molar ratios; their spherical images were observed in the TEM micrographs.  相似文献   
74.
We report the first observation of color-suppressed B( 0)-->D(0)pi(0), D(*0)pi(0), D0eta, and D0omega decays, and evidence for B( 0)-->D(*0)eta and D(*0)omega. The branching fractions are B(B( 0)-->D0pi(0)) = (3.1 +/- 0.4 +/- 0.5)x10(-4), B(B( 0) -->D(*0)pi(0)) = (2.7(+0.8+0.5)(-0.7-0.6))x10(-4), B(B( 0) --> D0eta) = (1.4(+0.5)(-0.4) +/- 0.3)x10(-4), B(B( 0) --> D0omega) = (1.8 +/- 0.5(+0.4)(-0.3))x10(-4), and we set 90% confidence level upper limits of B(B( 0) --> D(*0)eta)<4.6 x 10(-4) and B(B( 0)-->D(*0)omega)<7.9 x 10(-4). The analysis is based on a data sample of 21.3 fb(-1) collected at the Upsilon(4S) resonance by the Belle detector at the KEKB e(+)e(-) collider.  相似文献   
75.
The interaction between MEGA-10 and surface active agents was studied by means of circular dichroism. The molecular ellipticity of MEGA-10 varied with the addition of surface active agents, but its peak wavelength did not. The carbonyl group of MEGA-10 did not interact with the nonionic surface active agents nor the catanionic surfactant (of which the anionic and cationic portions were decanesulfonate and decyltrimethylammonium, respectively). It did, however, interact with the ionic surfactants, and also strongly with the ammonium group and the benzene ring. The interaction between MEGA-10 and ionic surfactant charges did not differ according to the sign of the charge. Circular dichroism spectra are a useful tool for performing research into the interaction between an optically active carbonyl group and an additive.  相似文献   
76.
We report a new measurement of the time-dependent CP-violating parameters in B(0)-->pi(+)pi(-) decays with 535 x 10(6) BB pairs collected with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider operating at the Upsilon(4S) resonance. We find 1464+/-65 B(0)-->pi(+)pi(-) events and measure the CP-violating parameters S(pipi)=-0.61+/-0.10(stat)+/-0.04(syst) and A(pipi)=+0.55+/-0.08(stat)+/-0.05(syst). We observe large direct CP violation with a significance greater than 5 standard deviations for any S(pipi) value. Using isospin relations, we measure the Cabibbo-Kobayashi-Maskawa quark-mixing matrix angle phi(2)=(97+/-11) degrees for the solution consistent with the standard model and exclude the range 11 degrees 相似文献   
77.
We report the first observation of B(0)-->J/psieta decay. These results are obtained from a data sample that contains 449 x10(6) BB[over] pairs accumulated at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. We observe a signal with a significance of 8.1 sigma and obtain a branching fraction of (9.5+/-1.7(stat)+/-0.8(syst)) x 10(-6).  相似文献   
78.
We report the first search for CP-violating decays of the Upsilon(4S) using a data sample that contains 535 x 10(6) Upsilon(4S) mesons with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. A partial reconstruction technique is employed to enhance the signal sensitivity. No significant signals were observed. We obtain an upper limit of 4 x 10(-7) at the 90% confidence level for the branching fractions of the CP violating modes, Upsilon(4S)-->B(0)B(0)-->J/psiK(S)(0)+J/psi(eta(c))K(S)(0). Extrapolating the result, we find that an observation with 5sigma significance is expected with a 30 ab(-1) data sample, which is within the reach of a future super B factory.  相似文献   
79.
We present a search for the rare decays B --> h(*)nunu[over ], where h(*) stands for a light meson. A data sample of 535 x 10{6} BB[over ] pairs collected with the Belle detector at the KEKB e{+}e{-} collider is used. Signal candidates are required to have an accompanying B meson fully reconstructed in a hadronic mode and signal side particles consistent with a single h(*) meson. No significant signal is observed and we set upper limits on the branching fractions at 90% confidence level. The limits on B{0} --> K{*0}nunu[over ] and B{+} --> K{+}nunu[over ] decays are more stringent than the previous constraints, while the first searches for B{0} --> K{0}nunu[over ], pi{0}nunu[over ], rho{0}nunu[over ], varphinunu[over ] and B{+} --> K{*+}nunu[over ], rho{+}nunu[over ] are reported.  相似文献   
80.
We present a measurement of CP asymmetry using a time-dependent Dalitz plot analysis of B0-->pi+pi-pi0 decays based on a 414 fb(-1) data sample containing 449 x 10(6) BB pairs. The data was collected on the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric energy e+ e- collider. Combining our analysis with information on charged B decay modes, we perform a full Dalitz and isospin analysis and obtain a constraint on the CKM angle phi2, 68 degrees < phi2 < 95 degrees as the 68.3% confidence interval for the phi2 solution consistent with the standard model (SM). A large SM-disfavored region also remains.  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