全文获取类型
收费全文 | 225篇 |
免费 | 4篇 |
国内免费 | 1篇 |
专业分类
化学 | 92篇 |
数学 | 44篇 |
物理学 | 94篇 |
出版年
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 5篇 |
2016年 | 2篇 |
2015年 | 3篇 |
2013年 | 7篇 |
2012年 | 5篇 |
2011年 | 6篇 |
2010年 | 5篇 |
2009年 | 6篇 |
2008年 | 7篇 |
2007年 | 3篇 |
2006年 | 10篇 |
2005年 | 4篇 |
2004年 | 4篇 |
2003年 | 5篇 |
2002年 | 3篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1996年 | 5篇 |
1995年 | 9篇 |
1994年 | 7篇 |
1993年 | 8篇 |
1992年 | 6篇 |
1991年 | 12篇 |
1990年 | 11篇 |
1989年 | 7篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1982年 | 2篇 |
1981年 | 3篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 2篇 |
1977年 | 4篇 |
1976年 | 8篇 |
1975年 | 2篇 |
1973年 | 2篇 |
1971年 | 2篇 |
1957年 | 1篇 |
1936年 | 4篇 |
1935年 | 3篇 |
1934年 | 2篇 |
1932年 | 1篇 |
1930年 | 1篇 |
1929年 | 2篇 |
1922年 | 1篇 |
1894年 | 1篇 |
排序方式: 共有230条查询结果,搜索用时 234 毫秒
121.
Mahon CS Jackson AW Murray BS Fulton DA 《Chemical communications (Cambridge, England)》2011,47(25):7209-7211
A water soluble polymer-scaffolded dynamic combinatorial library whose members can interconvert through acylhydrazone exchange was prepared and shown to re-equilibrate in the presence of macromolecular templates. 相似文献
122.
Bayram E Linehan JC Fulton JL Roberts JA Szymczak NK Smurthwaite TD Özkar S Balasubramanian M Finke RG 《Journal of the American Chemical Society》2011,133(46):18889-18902
Determining the true, kinetically dominant catalytically active species, in the classic benzene hydrogenation system pioneered by Maitlis and co-workers 34 years ago starting with [RhCp*Cl(2)](2) (Cp* = [η(5)-C(5)(CH(3))(5)]), has proven to be one of the most challenging case studies in the quest to distinguish single-metal-based "homogeneous" from polymetallic, "heterogeneous" catalysis. The reason, this study will show, is the previous failure to use the proper combination of: (i) in operando spectroscopy to determine the dominant form(s) of the precatalyst's mass under catalysis (i.e., operating) conditions, and then crucially also (ii) the previous lack of the necessary kinetic studies, catalysis being a "wholly kinetic phenomenon" as J. Halpern long ago noted. An important contribution from this study will be to reveal the power of quantitiative kinetic poisoning experiments for distinguishing single-metal, or in the present case subnanometer Rh(4) cluster-based catalysis, from larger, polymetallic Rh(0)(n) nanoparticle catalysis, at least under favorable conditions. The combined in operando X-ray absorption fine structure (XAFS) spectroscopy and kinetic evidence provide a compelling case for Rh(4)-based, with average stoichiometry "Rh(4)Cp*(2.4)Cl(4)H(c)", benzene hydrogenation catalysis in 2-propanol with added Et(3)N and at 100 °C and 50 atm initial H(2) pressure. The results also reveal, however, that if even ca. 1.4% of the total soluble Rh(0)(n) had formed nanoparticles, then those Rh(0)(n) nanoparticles would have been able to account for all the observed benzene hydrogenation catalytic rate (using commercial, ca. 2 nm, polyethyleneglycol-dodecylether hydrosol stabilized Rh(0)(n) nanoparticles as a model system). The results--especially the poisoning methodology developed and employed--are of significant, broader interest since determining the nature of the true catalyst continues to be a central, often vexing issue in any and all catalytic reactions. The results are also of fundamental interest in that they add to a growing body of evidence indicating that certain, appropriately ligated, coordinatively unsaturated, subnanometer M(4) transition-metal clusters can be relatively robust catalysts. Also demonstrated herein is that Rh(4) clusters are poisoned by Hg(0), demonstrating for the first time that the classic Hg(0) poisoning test of "homogeneous" vs "heterogeneous" catalysts cannot distinguish Rh(4)-based subnanometer catalysts from Rh(0)(n) nanoparticle catalysts, at least for the present examples of these two specific, Rh-based catalysts. 相似文献
123.
Robert L. Fulton 《Molecular physics》2013,111(2):405-413
The Kirkwood expression for the static dielectric constant of a polar substance is extended to non-zero frequencies by a means which avoids the introduction of spherical specimens and the connection between the dipoledipole correlation functions of distinct spatial regions. The procedure is based on a previously derived relation between the dynamic dielectric constant and the current-current susceptibility and on the use of the Callen-Welton theorem to relate the susceptibility to fluctuations. Surface effects are eliminated at the outset by consideration of media which are infinite in extent. A general relation between the long-range dipole-dipole correlations (which fall off as the inverse cube of the distance) and short-range correlations in a specimen composed of non-polarizable molecules is found from a consistency relation. It is shown that the two microscopic relaxation times which result from the existence of but one relaxation time in the dielectric constant correspond to the transverse and longitudinal relaxation times with the longitudinal time being screened relative to the transverse time by the static dielectric constant. 相似文献
124.
Carson W. Reed Mark G. Fulton Kellie D. Nance Craig W. Lindsley 《Tetrahedron letters》2019,60(10):743-745
This communication details the first total synthesis of the 13-membered macrolide, (?)-Melearoride A, as well as unnatural (+)-Melearoride A. The synthesis features a concise 13 step synthesis (11 steps longest linear sequence) that offers flexible stereo-control and multiple opportunities for unnatural analog synthesis to delve into antifungal SAR. The route features a cuprate addition, an Evans asymmetric alkylation, and a ring-closing metathesis (RCM) to close the 13-membered macrocyclic core. 相似文献
125.
Matthew J. Evans Dr. Mathew D. Anker Ahmed Mouchfiq Dr. Matthias Lein Dr. J. Robin Fulton 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(12):2606-2609
Addition of MesN3 (Mes=2,4,6-Me3C6H2) to germylene [(NONtBu)Ge] (NONtBu=O(SiMe2NtBu)2) ( 1 ) gives germanimine, [(NONtBu)Ge=NMes] ( 2 ). Compound 2 behaves as a metalloid, showing reactivity reminiscent of both transition metal-imido complexes, undergoing [2+2] addition with heterocumulenes and protic sources, as well as an activated diene, undergoing a [4+2] cycloaddition, or “metallo”-Diels–Alder, reaction. In the latter case, the diene includes the Ge=N bond and π-system of the Mes substituent, which is reactive towards dienophiles including benzaldehyde, benzophenone, styrene, and phenylacetylene. 相似文献
126.
Pain SD Catford WN Orr NA Angélique JC Ashwood NI Bouchat V Clarke NM Curtis N Freer M Fulton BR Hanappe F Labiche M Lecouey JL Lemmon RC Mahboub D Ninane A Normand G Soić N Stuttge L Timis CN Tostevin JA Winfield JS Ziman V 《Physical review letters》2006,96(3):032502
The breaking of the N=8 shell-model magic number in the 12Be ground state has been determined to include significant occupancy of the intruder d-wave orbital. This is in marked contrast with all other N=8 isotones, both more and less exotic than 12Be. The occupancies of the [FORMULA: SEE TEXT]orbital and the [FORMULA: SEE TEXT], intruder orbital were deduced from a measurement of neutron removal from a high-energy 12Be beam leading to bound and unbound states in 11Be. 相似文献
127.
128.
129.
130.
J A Fulton T D Schlabach J E Kerl E C Toren A R Miller 《Journal of chromatography. A》1979,175(2):269-281
We describe a dual-detector-post-column chromatographic reaction detector system that corrects for substances present in biological samples that interfere with the measurement of isoenzymes separated on a chromatographic column. The response observed at the detector in front of the reaction coil is mathematically dispersed, time transformed and subtracted from the detector behind the coil to produce a blank corrected chromatogram. The same computer program calculates peak areas and other chromatographic parameters such as height equivalent to a theoretical plate and retention time. In addition, we have evaluated the dispersion effects caused by various changes in our experimental system. 相似文献