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991.
992.
This is one of the applications of Part (I), in which the angular stiffness, and the corresponding stress distributions of U-shaped bellows were discussed. The bellows
was divided into protruding sections, concave sections and ring plates for the calculation that the general solution (I) with its reduced form to ring plates were used respectively, but the continuity of the surface stresses and the meridian
rotations at each joint of the sections were entirely satisfied. The resent results were compared with those of the slender
ring shell solution proposed earlier by the authors, the standards of the Expansion Joint Manufacturers Association (EJMA),
the experiment and the finite element method. It is shown that the governing equation and the general solution (I) are very effective.
Contributed by HUANG Qian
Biography: ZHU Wei-ping (1962-) 相似文献
993.
Zusammenfassung Nach einer kurzen Beschreibung über die Anwendung der Taylor-Wirbelströmung bei der Filtration von nichtnewtonschen Flüssigkeiten werden polymere Modellflüssigkeiten charakterisiert, die als Partikel- und Netzwerklösungen in einer Wirbelströmungsapparatur eingesetzt wurden. Die Fließkurven der Polymerlösungen zeigen aufgrund der extrem hochmolekularen Polymerproben neben strukturviskosen Erscheinungen auch dilatantes Fließverhalten mit besonderer Wirkung auf die Taylor-Wirbelströmung.Die Versuchsflüssigkeiten offenbaren vier verschiedene Typen von Strömungsinstabilitäten: spiralförmige, schwingende und stationäre Instabilitäten sowie gedämpfte Turbulenz. Während die stark strukturviskosen Netzwerklösungen alle genannten Formen aufweisen, fehlt bei den Partikellösungen die spiralförmige Instabilität.Unter Zuhilfenahme des Hantelmolekülmodells zur Beschreibung viskoelastischer Strömungsphänomene gelingt es, durch Einführung einer kritischen Deborahzahl den Einsatzpunkt nichtnewtonscher Taylorströmungseffekte vorauszusagen. Die gefundene Beziehung steht in engem Zusammenhang mit dehnviskositätserhöhenden Polymerwirkungen in Porenströmungen und mit reibungsmindernden Polymereffekten in turbulenten Rohrströmungen.
Nomenklatur A, B Konstanten aus Randbedingungen der Ringspaltströmung - C Polymerkonzentration - D Schergeschwindigkeit - De Deborahzahl - l Länge einer Wirbelzelle - L Zylinderlänge - m Gesamtanzahl der Wirbelpaare zur Bestimmung der Wellenzahl - M Molmasse der Polymere - M w Gewichtsmittel der Molmasse - M v Viskositätsmittel der Molmasse - n Drehzahl des Rotors - universelle Gaskonstante - r Radius - R a Radius des Außenzylinders - R i Radius des Innenzylinders - s Spaltweite - s * dimensionslose Spaltweite - T Temperatur - Ta Taylorzahl - v Umfangsgeschwindigkeit - z Anzahl der Wirbelpaare zur Bestimmung der Wellenzahl Griechische Symbole Deformationskoeffizient von Makromolekülen - Wellenzahl - Dehnrate - dynamische Viskosität - [] Grenzviskositätszahl - Relaxationszeit - Dichte - Schubspannung - Winkelgeschwindigkeit - a Winkelgeschwindigkeit des Außenzylinders - i Winkelgeschwindigkeit des Innenzylinders Indices c kritisch (erstmaliges Auftreten von Taylorwirbel) - N newtonsch - o onset, Schwellwert - P polymer - r radial - Sch schwingend - Spir spiralförmig - Stat stationär - Turb turbulent - T Taylorströmung - Umfangsrichtung Herrn Prof. Dr. Heinz Harnisch zum 60. Geburtstag gewidmet 相似文献
Experimental investigations dealing with dilute polymer solutions are described after a short review of the application of Taylor-vortex flow in the filtration processes of non-Newtonian fluids. The test fluids represent both viscoelastic solutions with isolated macromolecules and network solutions with power law fluid behaviour.These solutions show four different types of flow instabilities: spiral-shaped, oscillatory, steady and turbulent phenomena. The Taylor-numbers which depend upon the polymer concentration are determined for the onset of these instability types. For isolated macromolecule solutions, the Deborah-number concept for dilute dumbbell solutions can be applied to describe the first appearance of irregular nonstationary Taylor vortices.The present data are compared to literature values. This fluid behaviour is related to extensional viscosity increases which are also observed in porous media flow and turbulent pipe flow of dilute macromolecular solutions.
Nomenklatur A, B Konstanten aus Randbedingungen der Ringspaltströmung - C Polymerkonzentration - D Schergeschwindigkeit - De Deborahzahl - l Länge einer Wirbelzelle - L Zylinderlänge - m Gesamtanzahl der Wirbelpaare zur Bestimmung der Wellenzahl - M Molmasse der Polymere - M w Gewichtsmittel der Molmasse - M v Viskositätsmittel der Molmasse - n Drehzahl des Rotors - universelle Gaskonstante - r Radius - R a Radius des Außenzylinders - R i Radius des Innenzylinders - s Spaltweite - s * dimensionslose Spaltweite - T Temperatur - Ta Taylorzahl - v Umfangsgeschwindigkeit - z Anzahl der Wirbelpaare zur Bestimmung der Wellenzahl Griechische Symbole Deformationskoeffizient von Makromolekülen - Wellenzahl - Dehnrate - dynamische Viskosität - [] Grenzviskositätszahl - Relaxationszeit - Dichte - Schubspannung - Winkelgeschwindigkeit - a Winkelgeschwindigkeit des Außenzylinders - i Winkelgeschwindigkeit des Innenzylinders Indices c kritisch (erstmaliges Auftreten von Taylorwirbel) - N newtonsch - o onset, Schwellwert - P polymer - r radial - Sch schwingend - Spir spiralförmig - Stat stationär - Turb turbulent - T Taylorströmung - Umfangsrichtung Herrn Prof. Dr. Heinz Harnisch zum 60. Geburtstag gewidmet 相似文献
994.
995.
The solutions of the continuity equation and the equations of motion of the flow in the vicinity of a rotating disk have been established for an Ostwald fluid under steady-state conditions and in modulated flow around a mean value. Under steady-state conditions, the kinematics of the flow is scarcely dependent on the rheological parameters close to the disk, however, for n < 1 long-range effects have been put forward. For modulated flow, in the high-frequency range, a behaviour very different from that observed for a Newtonian fluid was found. In the low-frequency range an asymptotic solution has been proposed which is of special interest in mass transfer problems.Presented at the Second Conference of European Rheologists, Prague, June 17–20, 1986 相似文献
996.
Summary A three-parameter model is introduced to describe the shear rate — shear stress relation for dilute aqueous solutions of polyacrylamide (Separan AP-30) or polyethylenoxide (Polyox WSR-301) in the concentration range 50 wppm – 10,000 wppm. Solutions of both polymers show for
a similar rheological behaviour. This behaviour can be described by an equation having three parameters i.e. zero-shear viscosity
0, infinite-shear viscosity
, and yield stress
0, each depending on the polymer concentration. A good agreement is found between the values calculated with this three-parameter model and the experimental results obtained with a cone-and-plate rheogoniometer and those determined with a capillary-tube rheometer.
a Pa–1 physical quantity defined by:a = {1 – ( / 0)}/ 0 - c l concentration (wppm) - D m capillary diameter - L m length of capillary tube - P Pa pressure drop - R m radius of capillary tube - u m s–1 average velocity - v r m s–1 local axial velocity at a distancer from the axis of the tube - shear rate (–dv r /dr) - local shear rate in capillary flow - s–1 wall shear rate in capillary flow - Pa s dynamic viscosity - a Pa s apparent viscosity defined by eq. [2] - ( a ) Pa s apparent viscosity in capillary tube at a distanceR from the axis - 0 Pa s zero-shear viscosity defined by eq. [4] - Pa s infinite-shear viscosity defined by eq. [5] - l ratior/R - kg m– density - Pa shear stress - 0 Pa yield stress - r Pa local shear stress in capillary flow - R Pa wall shear stress in capillary flow R = (PR/2L) - v m3 s–1 volume rate of flow With 8 figures and 1 table 相似文献
Zusammenfassung Der Zusammenhang zwischen Schubspannung und Schergeschwindigkeit von strukturviskosen Flüssigkeiten wird durch ein Modell mit drei Parametern beschrieben. Mit verdünnten wäßrigen Polyacrylamid-(Separan AP-30) sowie Polyäthylenoxidlösungen (Polyox WSR-301) wird das Modell experimentell geprüft. Beide Polymerlösungen zeigen im untersuchten Schergeschwindigkeitsbereich von ein ähnliches rheologisches Verhalten. Dieses Verhalten kann mit drei konzentrationsabhängigen Größen, nämlich einer Null-Viskosität 0, einer Grenz-Viskosität und einer Fließgrenze 0 beschrieben werden. Die Ergebnisse von Experimenten mit einem Kegel-Platte-Rheogoniometer sowie einem Kapillarviskosimeter sind in guter Übereinstimmung mit den Werten, die mit dem Drei-Parameter-Modell berechnet worden sind.
a Pa–1 physical quantity defined by:a = {1 – ( / 0)}/ 0 - c l concentration (wppm) - D m capillary diameter - L m length of capillary tube - P Pa pressure drop - R m radius of capillary tube - u m s–1 average velocity - v r m s–1 local axial velocity at a distancer from the axis of the tube - shear rate (–dv r /dr) - local shear rate in capillary flow - s–1 wall shear rate in capillary flow - Pa s dynamic viscosity - a Pa s apparent viscosity defined by eq. [2] - ( a ) Pa s apparent viscosity in capillary tube at a distanceR from the axis - 0 Pa s zero-shear viscosity defined by eq. [4] - Pa s infinite-shear viscosity defined by eq. [5] - l ratior/R - kg m– density - Pa shear stress - 0 Pa yield stress - r Pa local shear stress in capillary flow - R Pa wall shear stress in capillary flow R = (PR/2L) - v m3 s–1 volume rate of flow With 8 figures and 1 table 相似文献
997.
There are some controversial opinions about the origin of folding β‐hairpin stability in aqueous solution. In this study, the structural and dynamic behavior of a 16‐residue β‐hairpin from B1 domain of protein G has been investigated at 280, 300, 350 and 450 K using molecular dynamics (MD) simulations by means of Atom‐Bond Electronegativity Equalization Method Fused into Molecular Mechanics i.e., ABEEMδπ/MM and the explicit ABEEM‐7P water solvent model. In addition, a 300 K simulation of one mutant having the aromatic residues substituted with alanines has been performed. The hydrophobic surface area, hydrophilic surface area and some structural properties have been used to measure the role of the hydrophobic interactions. It is found that the aromatic residues substituted with alanines have shown an evident destabilization of the structure and unfolding started after 1.5 ns. It is also found that the number of the main chain hydrogen bonds have different distributions through three different simulations. All above demonstrate that the hydrophobic interactions and the main chain hydrogen bonds play an important role in the stability of the folding structure of β‐hairpin in solution. Furthermore, through the structural analyses of the β‐hairpin structures from four temperature simulations and the comparison with other MD simulations of β‐hairpin peptides, the new ABEEMδπ force field can reproduce the structural data in good agreement with the experimental data. 相似文献
998.
通过对不同分子量的超支化聚乙烯亚胺(hyperbranched polyethyleni mine,HPEI)的端基进行部分或完全异丁酰胺(isobutyric amide,IBAm)化,可以制备一系列具有不同低临界溶解温度(Lower Critical SolutionTemperature,LCST)的超支化温敏聚合物HPEI-IBAm。通过离子键或氢键之间的相互作用,所得超支化温敏聚合物可以吸附于柠檬酸钠还原并稳定的14nm的金纳米粒子(AuNP)的表面,从而得到具有温敏性质的金纳米粒子。所得温敏金的LCST都低于其相应的温敏聚合物,其差值在0.8至6℃之间。在pH值为9.18的缓冲溶液中,通过改变所用聚合物的分子量以及异丁酰胺基团的取代度,所得温敏金的LCST可控制在21.7~48.2℃之间。此外,所得温敏金的LCST也是pH值敏感的,通过溶液pH值的改变,所得温敏金的LCST值可以在更宽的范围内调节。增加溶液的碱性,LCST可能变化不大或降低,减小溶液的碱性会使LCST升高,直到消失。在偏酸的条件下,所得金复合物通常发生聚集,变得不稳定。此外,溶液中的盐度对所得温敏金的LCST也有影响,氯化钠和硫酸钠会降低其LCST,尤其是硫酸钠的效果更显著。 相似文献
999.
Bernd Schröder Luís M.N.B.F. Santos Isabel M. Marrucho João A.P. Coutinho 《Fluid Phase Equilibria》2010
The methodology for the prediction of aqueous solubilities of solid organic compounds, and their temperature dependence, based on the Conductor-like Screening Model for Real Solvents (COSMO-RS/COSMOtherm) procedure, is presented and evaluated. The predictive capability of the quantum chemistry based program and the applied methodology was tested on the most common solid carboxylic acids. From the temperature dependence of the solubilities, the mean apparent enthalpies of solution were derived. The results obtained for a set of 27 carboxylic acids, consisting of aromatic carboxylic acids, dicarboxylic acids, as well as hydroxycarboxylic acids, are in good agreement with the experimental solubility data and their dependence with the temperature. The mean apparent enthalpies of solution, although of the same order of magnitude of the experimentally values, seem to be systematically underestimated. 相似文献
1000.
Several different models have been proposed to explain the origin of the complex anti-hole features observed in hole-burned (HB) spectra of excitonically coupled systems such as photosynthetic complexes. This lack of consensus presents a serious constraint on the interpretation of HB spectra and the underlying electronic structures of these systems. To resolve this problem we present results of modeling studies of non-resonant HB spectra taking uncorrelated excitation energy transfer and excitonic interactions into account. Simplified analytical results are compared with Monte Carlo simulations in which excitonic interactions are explicitly taken into account in order to disentangle a number of distinct effects. It is shown that these effects can accurately account for both hole shapes and the broad anti-hole structure observed in excitonically coupled systems. We argue that these models will provide a necessary framework for probing the electronic structure of these systems via HB spectroscopy. 相似文献