全文获取类型
收费全文 | 369篇 |
免费 | 7篇 |
国内免费 | 1篇 |
专业分类
化学 | 145篇 |
晶体学 | 3篇 |
力学 | 48篇 |
数学 | 41篇 |
物理学 | 140篇 |
出版年
2020年 | 6篇 |
2019年 | 6篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 9篇 |
2014年 | 3篇 |
2013年 | 19篇 |
2012年 | 14篇 |
2011年 | 18篇 |
2010年 | 9篇 |
2009年 | 4篇 |
2008年 | 8篇 |
2007年 | 13篇 |
2006年 | 7篇 |
2005年 | 5篇 |
2004年 | 10篇 |
2003年 | 23篇 |
2002年 | 16篇 |
2001年 | 12篇 |
2000年 | 10篇 |
1999年 | 20篇 |
1998年 | 5篇 |
1996年 | 12篇 |
1995年 | 7篇 |
1994年 | 3篇 |
1993年 | 8篇 |
1992年 | 3篇 |
1991年 | 5篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1978年 | 9篇 |
1977年 | 6篇 |
1975年 | 4篇 |
1974年 | 3篇 |
1973年 | 9篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1967年 | 2篇 |
1966年 | 4篇 |
1955年 | 2篇 |
1936年 | 4篇 |
1934年 | 2篇 |
1933年 | 2篇 |
1927年 | 3篇 |
1926年 | 2篇 |
排序方式: 共有377条查询结果,搜索用时 250 毫秒
81.
P. Knowles J. Deutsch J. Egger W. Fetscher F. Foroughi J. Govaerts M. Hadri K. Kirch S. Kistryn J. Lang X. Morelle O. Naviliat A. Ninane R. Prieels N. Severijns L. Simons J. Sromicki S. Vandormael P. Van Hove 《Hyperfine Interactions》1999,118(1-4):73-76
Unlike the majority of Michel parameters which are consistent with the Standard Model V-A interaction, the experimental value of ξ″(=0.65±0.36) [1] is poorly known. Our experiment will measure the longitudinal polarization,
P
L
, of positrons emitted from the decay of polarized muons. The value of P
L
, equal to unity in the Standard Model, will decrease for high energy positrons emitted antiparallel to the muon spin if the
combination of Michel parameters ξ″/ξξ′ − 1 deviates from the Standard Model value of zero.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
82.
G.M. Marshall T.A. Porcelli A. Adamczak J.M. Bailey G.A. Beer M.P. Faifman M.C. Fujiwara T.M. Huber R. Jacot-Guillarmod P. Kammel S.K. Kim P.E. Knowles A.R. Kunselman M. Maier V.E. Markushin G.R. Mason F. Mulhauser A. Olin C. Petitjean J. Zmeskal 《Hyperfine Interactions》1999,118(1-4):89-101
Solid hydrogen in the form of an inhomogeneous layered target offers several experimental advantages when compared with liquid
or gas. Beams of non-thermalized muonic hydrogen atoms allow us to explore resonant molecular ion formation processes near
eV kinetic energies. Isotopically specific layers make it possible to separate competing and confusing interactions and to
employ the time of flight for comparison with predictions based on theoretical energy dependences. Unambiguous charged fusion
product detection simplifies absolute intensity measurements.
The systematic uncertainties encountered in resonant molecular ion formation measurements, using solid hydrogen target layers,
are being investigated with simulations which use the many calculated energy-dependent rates and cross-sections which are
now available. The importance of the rates for processes such as muon transfer and elastic scattering are discussed, and results
of some recent analyses are presented.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
83.
Abigail J. Dobbyn Peter J. Knowles Robert J. Harrison 《Journal of computational chemistry》1998,19(11):1215-1228
A parallel implementation of the internally contracted (IC) multireference configuration (MRCI) module of the MOLPRO quantum chemistry program is described. The global array (GA) toolkit has been used in order to map an existing disk-paging small-memory algorithm onto a massively parallel supercomputer, where disk storage is replaced by the combined memory of all processors. This model has enabled a rather complicated code to be ported to the parallel environment without the need for the wholesale redesign of algorithms and data structures. Examples show that the parallel ICMRCI program can deliver results in a fraction of the time needed for equivalent uncontracted MRCI computations. Further examples demonstrate that ICMRCI computations with up to 107 variational parameters, and equivalent to uncontracted MRCI with 109 configurations, are feasible. The largest calculation demonstrates a parallel efficiency of about 80% on 128 nodes of a Cray T3E-300. © 1998 John Wiley & Sons, Inc. J Comput Chem 19: 1215–1228, 1998 相似文献
84.
85.
Knowles J Armatas G Hudson M Pomonis P 《Langmuir : the ACS journal of surfaces and colloids》2006,22(1):410-418
In this study, we carried out an investigation related to the determination of the anisotropy (b) of pores as well as the extent of microporosity (mic%) in various groups of nanostructured mesoporous materials. The mesoporous materials examined were fifteen samples belonging to the following groups of solids: MCM-48s, SBA-15s, SBA-16s, and mesoporous TiO(2) anatases. The porosities of those materials were modified either during preparation or afterward by the addition of Cu(II) species and/or 3(5)-(2-pyridinyl) pyrazole (PyPzH) into the pores. The modification of porosity in each group took place to make possible the internal comparison of the b and mic% values within each group. The estimation of both the b and mic% parameters took place from the corresponding nitrogen adsorption-desorption isotherms. The new proposed method is able to detect a percentage of microporosity as low as a few percent, which is impossible by any of the methods used currently, without the use of any reference sample or standard isotherms. A meaningful inverse relationship is apparent between the b and mic% values, indicating that large values of b correspond to small values of mic%. 相似文献
86.
With the prevalence of particle image velocimetry (PIV) as a quantitative tool for fluid mechanics diagnostics, its application
for analyzing complicated multiphase flows has been steadily increasing over the last several decades. While the primary issue
in using PIV for multiphase flows is in separating the information of the phases for independent analysis with a minimum of
spurious “cross-talk,” an equally crucial but often overlooked point is in the accurate quantitative measurement of the dispersed
phase concentration. Accurate concentration measurement is important due to the fact that the dispersed phase is often heterogeneously
distributed in both space and time, either due to a non-uniformity of the source of particulates (such as a spray nozzle or
sediment boundary) or due to inertial migration of the particles even from originally homogeneous spatial distributions. In
the current work, we examine the effects of light sheet profile distortion and attenuation by tracer seeding particles, as
well as reflected light from local wall boundaries on the effective light sheet thickness. The effective thickness is critical
for concentration measurements, as it dictates the dispersed phase detection volume. A direct calibration method is demonstrated
to measure the effective light sheet thickness in a water/glass bead system, which shows that systematic bias errors on the
order of 30% can result if the reflective bed condition is not accounted for, and the errors can be as high as 50% or more
if a single-point measure of the sheet width is used. 相似文献
87.
Hoa V. Phan Pradip Chakraborty Meimei Chen Yitzi M. Calm Dr. Kirill Kovnir Lawrence K. Keniley Jr. Jordan M. Hoyt Elisabeth S. Knowles Dr. Céline Besnard Prof. Mark W. Meisel Prof. Andreas Hauser Prof. Catalina Achim Prof. Michael Shatruk 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(49):15805-15815
Three iron(II) complexes, [Fe(TPMA)(BIM)](ClO4)2?0.5H2O ( 1 ), [Fe(TPMA)(XBIM)](ClO4)2 ( 2 ), and [Fe(TPMA)(XBBIM)](ClO4)2 ?0.75CH3OH ( 3 ), were prepared by reactions of FeII perchlorate and the corresponding ligands (TPMA=tris(2‐pyridylmethyl)amine, BIM=2,2′‐biimidazole, XBIM=1,1′‐(α,α′‐o‐xylyl)‐2,2′‐biimidazole, XBBIM=1,1′‐(α,α′‐o‐xylyl)‐2,2′‐bibenzimidazole). The compounds were investigated by a combination of X‐ray crystallography, magnetic and photomagnetic measurements, and Mössbauer and optical absorption spectroscopy. Complex 1 exhibits a gradual spin crossover (SCO) with T1/2=190 K, whereas 2 exhibits an abrupt SCO with approximately 7 K thermal hysteresis (T1/2=196 K on cooling and 203 K on heating). Complex 3 is in the high‐spin state in the 2–300 K range. The difference in the magnetic behavior was traced to differences between the inter‐ and intramolecular interactions in 1 and 2 . The crystal packing of 2 features a hierarchy of intermolecular interactions that result in increased cooperativity and abruptness of the spin transition. In 3 , steric repulsion between H atoms of one of the pyridyl substituents of TPMA and one of the benzene rings of XBBIM results in a strong distortion of the FeII coordination environment, which stabilizes the high‐spin state of the complex. Both 1 and 2 exhibit a photoinduced low‐spin to high‐spin transition (LIESST effect) at 5 K. The difference in the character of intermolecular interactions of 1 and 2 also manifests in the kinetics of the decay of the photoinduced high‐spin state. For 1 , the decay rate constant follows the single‐exponential law, whereas for 2 it is a stretched exponential, reflecting the hierarchical nature of intermolecular contacts. The structural parameters of the photoinduced high‐spin state at 50 K are similar to those determined for the high‐spin state at 295 K. This study shows that N‐alkylation of BIM has a negligible effect on the ligand field strength. Therefore, the combination of TPMA and BIM offers a promising ligand platform for the design of functionalized SCO complexes. 相似文献
88.
We present a pilot application of the recently proposed quasi-variational coupled cluster method to the energies, polarizabilities, and second hyperpolarizabilities of model hydrogen chains. Relative to other single-reference methods of equivalent computational complexity, we demonstrate this method to be highly robust and especially useful when traditional coupled cluster theory fails to perform adequately. In particular, our results indicate it to be a suitable method for the black-box treatment of multiradicals, making it of widespread general interest and applicability. 相似文献
89.
A Mukherjee M Dasgupta DJ Hinde CR Morton AC Berriman RD Butt JO Newton H Timmers 《Pramana》2001,57(1):195-198
Fusion cross-sections for the 7Li + 12C reaction have been measured at energies above the Coulomb barrier by the direct detection of evaporation residues. The heavy
evaporation residues with energies below 3 MeV could not be separated out from the α-particles in the spectrum and hence their
contribution was estimated using statistical model calculations. The present work indicates that suppression of fusion cross-sections
due to the breakup of 7Li may not be significant for 7Li + 12C reaction at energies around the barrier. 相似文献
90.
G. M. Marshall A. Adamczak J. M. Bailey J. L. Beveridge G. A. Beer J. H. Brewer V. M. Bystritsky M. P. Faifman B. M. Forster M. C. Fujiwara T. M. Huber R. Jacot-Guillarmod P. Kammel K. R. Kendall N. P. Kherani S. K. Kim P. E. Knowles A. R. Kunselman M. Maier V. E. Markushin V. S. Melezhik G. R. Mason F. Mulhauser A. Olin C. Petitjean T. A. Porcelli L. A. Schaller V. A. Stolupin J. Zmeskal 《Hyperfine Interactions》2001,138(1-4):203-211
Since the discovery that muonic deuterium at energies near a few eV could travel distances of the order of 1 mm in condensed
hydrogen, and in particular that muonic tritium and muonic deuterium could emerge from the surface of a solid hydrogen layer,
the advantages of solid targets have enabled the study of several processes important in muon catalyzed fusion. A review of
the results is presented, emphasizing the strengths and limitations of the use of solid hydrogen layer targets.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献