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141.
David Hoff 《纯数学与应用数学通讯》2002,55(11):1365-1407
We prove the global existence of solutions of the Navier‐Stokes equations of compressible, barotropic flow in two space dimensions which exhibit convecting singularity curves. The fluid density and velocity gradient have jump discontinuities across these curves, exactly as predicted by the Rankine‐Hugoniot conditions, and these jump discontinuities decay exponentially in time, more rapidly for smaller viscosities. The singularity curves remain C1+α despite the fact that the velocity fields which convect them are not continuously differentiable. © 2002 Wiley Periodicals, Inc. 相似文献
142.
We prove that solutions of the Navier-Stokes equations of three-dimensional compressible flow, restricted to fluid-particle trajectories, can be extended as analytic functions of complex time. As consequences we derive backward uniqueness of solutions as well as sharp rates of smoothing for higher-order Lagrangean time derivatives. The solutions under consideration are in a reasonably broad regularity class corresponding to small-energy initial data with a small degree of regularity, the latter being required for conversion to the Lagrangean coordinate system in which the analysis is carried out. 相似文献
143.
144.
Three different routes have been investigated for the preparation of 6-aryl-N-(1-arylethyl)thienopyrimidin-4-amines. First the possibilities of selective Suzuki reactions on 6-bromo-4-chlorothienopyrimidine were investigated. The preference for mono arylation at C-6 could be increased, in the case of Pd(PPh3)4 catalysis, by reducing the water content of the reaction, or by using less electron rich Pd-ligands. The highest selectivity was obtained with Pd(OAc)2 or Pd2(dba)3, while reactions with the more electron rich Pd(PPh3)4 and especially XPhos gave a lower mono- to dicoupled product ratio. Secondly, two alternative strategies avoiding this selectivity issue were tested. Suzuki reaction on C-6 of 6-bromothienopyrimidin-4(3H)-one (three examples) proceeded in 70-89% yield using Pd(PPh3)4 in dioxane/water. Similar conditions on 4-amino-6-bromo-thienopyrimidine (eight examples) gave 67-95% yield. The reaction could be performed with boronic acids containing nonprotected phenolic groups in the ortho, meta and para positions. By prolonging the reaction time, coupling with sterically crowded arylboronic acids was also efficient. Diarylation of 6-bromo-4-chlorothienopyrimidine gave the corresponding 4,6-diarylated derivatives in 71-80% yield depending on the nature of the arylboronic acid. 相似文献
145.
Znakovskaya I von den Hoff P Marcus G Zherebtsov S Bergues B Gu X Deng Y Vrakking MJ Kienberger R Krausz F de Vivie-Riedle R Kling MF 《Physical review letters》2012,108(6):063002
The steering of electron motion in molecules is accessible with waveform-controlled few-cycle laser light and may control the outcome of light-induced chemical reactions. An optical cycle of light, however, is much shorter than the duration of the fastest dissociation reactions, severely limiting the degree of control that can be achieved. To overcome this limitation, we extended the control metrology to the midinfrared studying the prototypical dissociative ionization of D(2) at 2.1 μm. Pronounced subcycle control of the directional D(+) ion emission from the fragmentation of D(2)(+) is observed, demonstrating unprecedented charge-directed reactivity. Two reaction pathways, showing directional ion emission, could be observed and controlled simultaneously for the first time. Quantum-dynamical calculations elucidate the dissociation channels, their observed phase relation, and the control mechanisms. 相似文献
146.
147.
Swine operations can affect air quality by emissions of odor, volatile organic compounds (VOCs) and other gases, and particulate matter (PM). Particulate matter has been proposed to be an important pathway for carrying odor. However, little is known about the odor-VOCs-PM interactions. In this research, continuous PM sampling was conducted simultaneously with three collocated TEOM 1400a analyzers inside a 1000-head swine finish barn located in central Iowa. Each TEOM was fitted with total suspended particulate (TSP), PM-10, PM-2.5 and PM-1 preseparators. Used filters were stored in 40 mL vials and transported to the laboratory. VOCs adsorbed/absorbed to dust were allowed to equilibrate with vial headspace. Solid-phase microextraction (SPME) Carboxen/polydimethylsiloxane (PDMS) 85 microm fibers were used to extract VOCs. Simultaneous chemical and olfactometry analyses of VOCs and odor associated with swine PM were completed using a gas chromatography-mass spectrometry-olfactometry (GC-MS-O) system. Fifty VOCs categorized into nine chemical function groups were identified and confirmed with standards. Five of them are classified as hazardous air pollutants. VOCs were characterized with a wide range of molecular weight, boiling points, vapor pressures, water solubilities, odor detection thresholds, and atmospheric reactivities. All characteristic swine VOCs and odorants were present in PM and their abundance was proportional to PM size. However, the majority of VOCs and characteristic swine odorants were preferentially bound to smaller-size PM. The findings indicate that a significant fraction of swine odor can be carried by PM. Research of the effects of PM control on swine odor mitigation is warranted. 相似文献
148.
P. von?den Hoff I. Znakovskaya S. Zherebtsov M. F. Kling R. de Vivie-Riedle 《Applied physics. B, Lasers and optics》2010,98(4):659-666
We outline the details of our new method to calculate angular-dependent ionization probabilities based on electronic structure
theory for diatomic and larger systems. To demonstrate its abilities, we compare our calculations to measured ionization probabilities
of the four molecules D2, N2, O2 and CO in the strong-field regime. The calculated angular distributions yield better agreement with the experimental data
than those obtained from the widely used MO-ADK theory. For CO the measured angular distributions of ionic fragments indicate
contributions to the ionization from both the HOMO and the HOMO-1 orbital, an effect that is addressed by the theory. 相似文献
149.
Carroll EC Song SH Kumauchi M van Stokkum IH Jailaubekov A Hoff WD Larsen DS 《The journal of physical chemistry letters》2010,1(19):2793-2799
The ultrafast excited-state dynamics underlying the receptor state photorecovery is resolved in the M100A mutant of the photoactive yellow protein (PYP) from Halorhodospira halophila. The M100A PYP mutant, with its distinctly slower photocycle than wt PYP, allows isolation of the pB signaling state for study of the photodynamics of the protonated chromophore cis-p-coumaric acid. Transient absorption signals indicate a subpicosecond excited-state proton-transfer reaction in the pB state that results in chromophore deprotonation prior to the cis-trans isomerization required in the photorecovery dynamics of the pG state. Two terminal photoproducts are observed, a blue-absorbing species presumed to be deprotonated trans-p-coumaric acid and an ultraviolet-absorbing protonated photoproduct. These two photoproducts are hypothesized to originate from an equilibrium of open and closed folded forms of the signaling state, I(2) and I(2)'. 相似文献
150.
Creating lasso-solutions for the traveling salesman problem with pickup and delivery by Tabu search 总被引:2,自引:0,他引:2
We consider the Traveling Salesman Problem with Pickup and Delivery (TSPPD) where the same costumers might require both deloverie
of goods and pickup of other goods. All the goods should be transported from/to the same depot. A vehicle on a TSPPD-tour
could often get some practical problems when arranging the load. Even if the vehicle has enough space for all the pickups,
one has to consider that they are stored in a way that doesn't block the delivery for the next customer. In real life problems
this occurs for instance for breweries when they deliver bottles of beer or mineral water and collects empty bottles from
the same customers on the same tour. In these situations we could relax the constraints of only checking Hamiltonian tours,
and also try solutions that can visit customers in a way giving rise to a ‘alsso’ model. A solution which first only delivers
bottles until the vehicle is partly unloaded, then do both delivery and pickup at the remaining customers and at last picks
up the empty bottle from the first visited customers, could in these situations be better than a pure Hamiltonian tour, at
least in a practical setting. To find such solutions, we will use the metaheuristic Tabu Search on some well known TSPPD-problems,
and compare them to other kinds of solutions on the same problems. 相似文献