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排序方式: 共有109条查询结果,搜索用时 15 毫秒
101.
SANTOS JUAN ENRIQUE; DOUGLAS JIM JR; MORLEY MARY E.; LOVERA OSCAR M. 《IMA Journal of Numerical Analysis》1988,8(4):415-433
A model is defined to simulate the propagation of waves in aradially symmetric, isotropic, composite system consisting ofa fluid-filled well bore f through a fluid-saturated poroussolid p. Biot's equations of motion are chosen to describe thepropagation of waves in p, while the standard equation of motionfor compressible inviscid fluids is used for f, with appropriateboundary conditions at the contact surface between f and p.Also, absorbing boundary conditions for the artificial boundariesof p are derived for the model, their effect being to make themtransparent for waves arriving normally First, results on the existence and uniqueness of the solutionof the differential problem are given and then a discrete-time,explicit finite element procedure is defined and analysed, withfinite element spaces suited for radially symmetric problemsbeing used for the spatial discretisation. 相似文献
102.
W. A. SUMMERS JR. C. ENWALL J. G. BURR R. L. LETSINGER 《Photochemistry and photobiology》1973,17(5):295-301
Abstract— Quantum yields for 254 nm ultraviolet photoaddition of the nucleophiles hydrazine, HCN, HSO3 - , methyl amine, and BH4 - to uracil have been measured; the quantum yields for hydrazine, HCN, and HSO3 - additions are pH-dependent. The nucleophiles sulfide, azide, chloride, bromide, iodide, nitrite and thiocyanate failed to photo–add under similar conditions. These reactions are interpreted as 1,4-additions to the conjugated enone system of the anti-aromatic compound, uracil; as suggested by S. Y. Wang (Wang and Nnadi, 1968). The nuclear magnetic resonance (NMR) spectrum of the photohydrate of uracil-5-d-showed that the proton was added to the 5-position in a stereochemically random manner. The photoaddition of HSO3 - takes place at much lower concentrations than required for the thermal addition of this anion and is also stereochemically random. 相似文献
103.
C. T. LIN Y. G. CHYAN G. C. KRESHECK HERBERT C. BITTING JR M. A. EL-SAYED 《Photochemistry and photobiology》1989,49(5):641-648
Several spectroscopic techniques (absorption, emission, transient absorption and differential scanning calorimetry--DSC) were used to investigate the deprotonation of dibucaine.HCl in a hydrophobic environment, and the interaction sites and mechanisms of the local anesthetic dibucaine.HCl on bacteriorhodopsin (bR) in purple membrane. The important results are summarized as follows: (1) the visible absorption features of native (lambda max = 568 nm) and deionized (lambda max = 608 nm) bR are sensitive to the amount of dibucaine.HCl added; (2) the emission spectrum of dibucaine.HCl embedded in the retinal-free mutant bR is similar to that of dibucaine free base in Triton X-100 micellar solutions; (3) the phosphorescence emission of dibucaine at 77 K is completely quenched by bR and the fluorescence quenching rate for the incorporated dibucaine.HCl in bR was determined as kq = 4.09 x 10(13) M-1 s-1; (4) the incorporation of dibucaine.HCl in bR inhibits the slow component rate of formation of M412 and decreases the amount of M412 formation in the photochemical cycle of bR; and (5) the thermal stability of native bR was measured by DSC in the presence and absence of dibucaine and yielded an endothermic transition at 95.9 +/- 1.0 degrees C with 13.6 J/g (3.25 +/- 0.12 cal/g) of enthalpy changes. All observations suggest that the action site of the local anesthetic, dibucaine.HCl, is near or at the chromophore, i.e. the retinal Schiff base of bR. The anesthetic action on bR purple membrane is probably via a specific site binding, but not a conformational mechanism. 相似文献
104.
Alves GA Amato S Anjos JC Appel JA Astorga J Bracker SB Cremaldi LM Dagenhart WD Darling CL Dixon RL Errede D Fenker HC Gay C Green DR Jedicke R Karchin PE Kennedy C Kwan S Lueking LH de Mello Neto JR Metheny J Milburn RH de Miranda JM da Motta Filho H Napier A Passmore D Rafatian A dos Reis AC Ross WR Santoro AF Sheaff M Souza MH Spalding WJ Stoughton C Streetman ME Summers DJ Takach SF Wallace A Wu Z 《Physical review letters》1996,77(12):2392-2395
105.
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107.
R. M. Shannon S. Chamberlin N. J. Cornish J. A. Ellis C. M. F. Mingarelli D. Perrodin P. Rosado A. Sesana S. R. Taylor L. Wen C. G. Bassa J. Gair G. H. Janssen R. Karuppusamy M. Kramer K. J. Lee K. Liu I. Mandel M. Purver T. Sidery R. Smits B. W. Stappers A. Vecchio 《General Relativity and Gravitation》2014,46(8):1-11
This paper summarizes parallel session C1: Pulsar Timing Arrays of the Amaldi10/GR20 Meeting held in Warsaw, Poland in July 2013. The session showcased recent results from pulsar timing array collaborations, advances in modelling the gravitational-wave signal, and new methods to search for and characterize gravitational waves in pulsar timing array observations. 相似文献
108.
Jonathan R. Gair Ilya Mandel M. Coleman Miller Marta Volonteri 《General Relativity and Gravitation》2011,43(2):485-518
We discuss the capability of a third-generation ground-based detector such as the Einstein Telescope (ET) to enhance our astrophysical
knowledge through detections of gravitational waves emitted by binaries including intermediate-mass and massive black holes.
The design target for such instruments calls for improved sensitivity at low frequencies, specifically in the ~ 1-10{\sim 1-10} Hz range. This will allow the detection of gravitational waves generated in binary systems containing black holes of intermediate
mass,
~ 100-10000 M\odot{\sim100-10000\,\,M_{\odot}} . We primarily discuss two different source types—mergers between two intermediate mass black holes (IMBHs) of comparable
mass, and intermediate-mass-ratio inspirals (IMRIs) of smaller compact objects with mass
~ 1-10 M\odot{\sim1-10\,\,M_{\odot}} into IMBHs. IMBHs may form via two channels: (i) in dark matter halos at high redshift through direct collapse or the collapse
of very massive metal-poor Population III stars, or (ii) via runaway stellar collisions in globular clusters. In this paper,
we will discuss both formation channels, and both classes of merger in each case. We review existing rate estimates where
these exist in the literature, and provide some new calculations for the approximate numbers of events that will be seen by
a detector like the Einstein Telescope. These results indicate that the ET may see a few to a few thousand comparable-mass
IMBH mergers and as many as several hundred IMRI events per year. These observations will significantly enhance our understanding
of galactic black-hole growth, of the existence and properties of IMBHs and of the astrophysics of globular clusters. We finish
our review with a discussion of some more speculative sources of gravitational waves for the ET, including hypermassive white
dwarfs and eccentric stellar-mass compact-object binaries. 相似文献
109.
Abstract Humic substances are the major organic constituents of soils and sediments. They also occur in small concentrations in natural surface waters and groundwaters. They form through the breakdown of plant and animal tissues by chemical and biological processes that tend to produce complex chemical structures that are more stable than the original material from which they were derived. One of the more important characteristics of humic substances is their ability to form water-soluble and water-insoluble complexes with metal ions and hydrous oxides and to interact with clay minerals and various organic compounds such as alkanes, fatty acids, and toxic organic substances such as pesticides. 相似文献