全文获取类型
收费全文 | 723篇 |
免费 | 6篇 |
国内免费 | 1篇 |
专业分类
化学 | 453篇 |
晶体学 | 2篇 |
力学 | 17篇 |
数学 | 103篇 |
物理学 | 155篇 |
出版年
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 5篇 |
2017年 | 4篇 |
2016年 | 5篇 |
2015年 | 8篇 |
2014年 | 8篇 |
2013年 | 40篇 |
2012年 | 27篇 |
2011年 | 34篇 |
2010年 | 11篇 |
2009年 | 9篇 |
2008年 | 36篇 |
2007年 | 41篇 |
2006年 | 29篇 |
2005年 | 46篇 |
2004年 | 29篇 |
2003年 | 28篇 |
2002年 | 21篇 |
2001年 | 10篇 |
2000年 | 6篇 |
1999年 | 11篇 |
1998年 | 7篇 |
1997年 | 8篇 |
1996年 | 13篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 12篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 5篇 |
1988年 | 4篇 |
1987年 | 16篇 |
1986年 | 12篇 |
1985年 | 18篇 |
1984年 | 11篇 |
1983年 | 9篇 |
1982年 | 10篇 |
1981年 | 12篇 |
1980年 | 18篇 |
1979年 | 10篇 |
1978年 | 14篇 |
1977年 | 12篇 |
1976年 | 6篇 |
1975年 | 8篇 |
1974年 | 11篇 |
1973年 | 7篇 |
1972年 | 4篇 |
1971年 | 5篇 |
排序方式: 共有730条查询结果,搜索用时 453 毫秒
111.
Adam NE Alexander JP Berkelman K Cassel DG Crede V Duboscq JE Ecklund KM Ehrlich R Fields L Galik RS Gibbons L Gittelman B Gray R Gray SW Hartill DL Heltsley BK Hertz D Jones CD Kandaswamy J Kreinick DL Kuznetsov VE Mahlke-Krüger H Meyer TO Onyisi PU Patterson JR Peterson D Phillips EA Pivarski J Riley D Ryd A Sadoff AJ Schwarthoff H Shi X Shepherd MR Stroiney S Sun WM Urner D Wilksen T Weaver KM Weinberger M Athar SB Avery P Breva-Newell L Patel R Potlia V Stoeck H Yelton J Rubin P Cawlfield C 《Physical review letters》2006,96(8):082004
We observe signals for the decays psi(3770) --> XJ/psi from data acquired with the CLEO detector operating at the CESR e+ e- collider with square root of s = 3773 MeV. We measure the following branching fractions Beta(psi(3770) --> XJ/psi and significances: (189 +/- 20 +/- 20) x 10(-5) (11.6sigma) for X = pi+ pi-, (80 +/- 25 +/- 16) x 10(-5) (3.4sigma) for X = pi0 pi0, and (87 +/- 33 +/- 22) x 10(-5) (3.5sigma) for X = eta, where the errors are statistical and systematic, respectively. The radiative return process e+ e- --> gamma psi(2S) populates the same event sample and is used to measure Gamma ee[psi(2S)] = (2.54 +/- 0.03 +/- 0.11) keV. 相似文献
112.
Rosner JL Adam NE Alexander JP Berkelman K Cassel DG Duboscq JE Ecklund KM Ehrlich R Fields L Gibbons L Gray R Gray SW Hartill DL Heltsley BK Hertz D Jones CD Kandaswamy J Kreinick DL Kuznetsov VE Mahlke-Krüger H Meyer TO Onyisi PU Patterson JR Peterson D Phillips EA Pivarski J Riley D Ryd A Sadoff AJ Schwarthoff H Shi X Stroiney S Sun WM Wilksen T Weinberger M Athar SB Avery P Breva-Newell L Patel R Potlia V Stoeck H Yelton J Rubin P Cawlfield C Eisenstein BI Karliner I Kim D Lowrey N Naik P 《Physical review letters》2006,96(12):121801
We present the first experimental limits on high-q2 contributions to charmless semileptonic decays of the form expected from the weak annihilation (WA) decay mechanism. Such contributions could bias determinations of /Vub/ from inclusive measurements of B-->Xulupsilon. Using a wide range of models based on available theoretical input we set a limit of GammaWA/Gammab-->u<7.4% (90% confidence level) on the WA fraction, and assess the impact on previous inclusive determinations of /Vub/. 相似文献
113.
Laursen JB Nielsen J Haack T Pusuluri S David S Balakrishna R Zeng Y Ma Z Doyle TB Mitscher LA 《Combinatorial chemistry & high throughput screening》2006,9(9):663-681
A synthetic reexamination of a series of ketodihydronicotinic acid class antibacterial agents was undertaken in an attempt to improve their therapeutic potential. A convenient new synthesis was developed involving hetero Diels-Alder chemistry producing 74 new analogs in a multiple parallel synthetic manner and these were examined in vitro for their antimicrobial potential. Several compounds demonstrated significant broad-spectrum activity against clinically derived bacterial strains but previously known 1-(2,4-difluorophenyl)-6-(4-dimethylaminophenyl)-4-pyridone-3-carboxylic acid (7) remained the most potent compound in this class. Cross-resistance with ciprofloxacin supported a commonality of mode of action. Permiabilization of Escherichia coli cells by polymyxin B significantly enhanced potency with these agents suggesting that poor cellular uptake was primarily responsible for the disappointing activity against bacteria that some of the analogs exhibited. 相似文献
114.
Methane activation by group 5 transition-metal atoms in excess argon and the matrix infrared spectra of reaction products have been investigated. Vanadium forms only the monohydrido methyl complex (CH3-VH) in reaction with CH4 and upon irradiation. On the other hand, the heavier metals form methyl hydride and methylidene dihydride complexes (CH3-MH and CH2=MH2) along with the methylidyne trihydride anion complexes (CHMH3-). The neutral products, particularly the methylidene complex, increase markedly on irradiation whereas the anionic product depletes upon UV irradiation or addition of a trace of CCl4 or CBr4 to trap electrons. Other absorptions that emerge on irradiation and annealing increase markedly at higher precursor concentration and are attributed to a higher-order product ((CH3)2MH2)). Spectroscopic evidence suggests that the agostic Nb and Ta methylidene dihydride complexes have two identical metal-hydrogen bonds. 相似文献
115.
El Gabaly F Gallego S Muñoz C Szunyogh L Weinberger P Klein C Schmid AK McCarty KF de la Figuera J 《Physical review letters》2006,96(14):147202
By means of spin-polarized low-energy electron microscopy, we show that the magnetic easy axis of one to three atomic-layer thick cobalt films on Ru(0001) changes its orientation twice during deposition: One-monolayer and three-monolayer thick films are magnetized in plane, while two-monolayer films are magnetized out of plane. The Curie temperatures of films thicker than one monolayer are well above room temperature. Fully relativistic calculations based on the screened Korringa-Kohn-Rostoker method demonstrate that only for two-monolayer cobalt films does the interplay between strain, surface, and interface effects lead to perpendicular magnetization. 相似文献
116.
P. Weinberger 《哲学杂志》2013,93(12):1747-1764
It is shown that by ‘stacking’ together a semi-infinite sample subsystem with a semi-infinite tip subsystem, difficulties with respect to a common Fermi level for the whole system can approximately be overcome in all those cases when the substrate (serving as lead) and the second lead are different materials. Based on this procedure by means of the spin-polarized (fully) relativistic screened Korringa–Kohn–Rostocker method and an equivalent Kubo equation, theoretical spin-polarized STM spectra for Pt(111)/Co n /Cr15 W22/Cu(111) with respect to an applied external magnetic field are evaluated in terms of difference conductivities as a function of the corresponding free energy. These spectra are interpreted using layer-resolved contributions to the difference conductivities in order to indicate which parts of the sample dominate changes in the tunneling current caused by changing the orientation of the magnetization. Also shown are estimates of the time-scales to switch from perpendicular to in-plane and vice versa. All investigated properties suggest that different situations apply when the number of Co layers on top of Pt(111) is increased from one to three. 相似文献
117.
Peter Weinberger 《哲学杂志》2013,93(13):1727-1732
The history of the Periodic Table of Elements covers almost 300 years: from the discovery of phosphorus in 1669 to that of Lawrencium in 1961. Before that period, only elements such as copper, silver, gold, mercury, lead and of course carbon were known, which already had accompanied the history of mankind for millennia. The first “wave” of discoveries of new metals occurred at the close of the eighteenth and the beginning of the nineteenth centuries and was almost entirely based on “wet chemistry”. Because this period, in which no physics-related techniques of identification were available, seems to be now so remote, it is worthwhile to recall these discoveries in the context and style of their time by making use of the Philosophical Magazine archives. 相似文献
118.
Peter Weinberger 《哲学杂志》2013,93(20):2576-2612
Abstract Based on the idea that a scientific journal is also an “agora” (Greek: market place) for the exchange of ideas and scientific concepts, the history of thermodynamics between 1800 and 1910 as documented in the Philosophical Magazine Archives is uncovered. Famous scientists such as Joule, Thomson (Lord Kelvin), Clausius, Maxwell or Boltzmann shared this forum. Not always in the most friendly manner. It is interesting to find out, how difficult it was to describe in a scientific (mathematical) language a phenomenon like “heat”, to see, how long it took to arrive at one of the fundamental principles in physics: entropy. Scientific progress started from the simple rule of Boyle and Mariotte dating from the late eighteenth century and arrived in the twentieth century with the concept of probabilities. Thermodynamics was the driving intellectual force behind the industrial revolution, behind the enormous social changes caused by this revolution. The history of thermodynamics is a fascinating story, which also gives insights into the mechanism that seem to govern science. 相似文献
119.
120.