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991.
In the paper, a new hybrid genetic algorithm solving the DNA sequencing problem with negative and positive errors is presented. The algorithm has as its input a set of oligonucleotides coming from a hybridization experiment. The aim is to reconstruct an original DNA sequence of a known length on the basis of this set. No additional information about the oligonucleotides nor about the errors is assumed. Despite that, the algorithm returns for computationally hard instances surprisingly good results, of a very high similarity to original sequences. 相似文献
992.
Antiferroelectric behavior is observed in artificially layered KTaO (3)/KNbO (3) perovskite superlattices. While KTaO (3) and KNbO (3) are ferroelectric and paraelectric, respectively, the superlattice appears antiferroelectric based on an increase in the dielectric constant with applied dc bias. This dielectric behavior is inconsistent with the nonlinear response for either paraelectric or ferroelectric materials. However, an increase in the dielectric constant with applied electric field is consistent with antiferroelectric behavior. The antiferroelectric ordering appears to be induced by cation modulation imposed by the superlattice. 相似文献
993.
Low-threshold self-induced modulational instability ring laser in highly nonlinear fiber yielding a continuous-wave 262-GHz soliton train 总被引:1,自引:0,他引:1
Modulational instability (MI) is employed in a self-induced ring cavity configuration based on highly nonlinear dispersion-shifted fiber (HNL DSF) and an erbium-doped fiber amplifier to generate a continuous-wave 262-GHz train of 365-fs optical solitons. The laser operates around 1540 nm, with an average output power of 15 mW. MI is achieved at a low threshold as a result of low average cavity dispersion and high fiber nonlinearity. It is shown that, because of the normal dispersion of the HNL DSF, the solitons exist in the average soliton regime. 相似文献
994.
Copropagating and counterpropagating pumps in second-order- pumped discrete fiber Raman amplifiers 总被引:1,自引:0,他引:1
The gains and noise figures of discrete second-order-pumped fiber Raman amplifiers utilizing copropagating and counterpropagating pump configurations were experimentally obtained, and the gain results were compared with computer simulations. It was found that the additional gain that is due to second-order Raman pumping is larger for the copropagating pumps than for the counterpropagating pumps, in agreement with simulations. In contrast to distributed second-order-pumped fiber Raman amplifiers, a slight increase in noise figure, by as much as ~1 dB was observed relative to the single-pump scheme. However, the advantages of second-order pumping in discrete amplifiers include greater flexibility in design of the gain distribution along the fiber and the ability to spectrally distribute the pump powers to avoid undesired nonlinear effects. 相似文献
995.
Sharma PA Hur N Horibe Y Chen CH Kim BG Guha S Cieplak MZ Cheong SW 《Physical review letters》2002,89(16):167003
Our results from various transport experiments on Mg1-xB2 indicate a surprising effect associated with the presence of a Mg deficiency in MgB2: the phase separation between Mg-vacancy rich and Mg-vacancy poor phases. The Mg-vacancy poor phase is superconducting, but the insulating nature of the Mg-vacancy rich phase probably originates from the Anderson (disorder-induced) localization of itinerant carriers. Furthermore, electron diffraction measurements indicate that within vacancy-rich regions these defects tend to order with intriguing patterns. This electronic phase separation in Mg1-xB2 shows similar, but also distinct characteristics compared with that observed in La(2)CuO(4+delta). 相似文献
996.
[reaction: see text] Regioselective monoacylation of a diamine is achieved by including a suitably positioned 4-(dimethylamino)pyridine (DMAP) group within the molecule. 相似文献
997.
We present a proposal for protecting states against decoherence, based on the engineering of pointer states. We apply this procedure to the vibrational motion of a trapped ion, and show how to protect qubits, squeezed states, approximate phase eigenstates, and superpositions of coherent states. 相似文献
998.
P Leal de Matos 《The Journal of the Operational Research Society》2001,52(8):888-895
Air Traffic Control (ATC) ensures the safe and expeditious passage of all aircraft in controlled airspace, usually, airspace above 5000–7000?ft or around main airports. Serious airspace congestion has led to demands for more cost-effective ATC and to plans to privatise air traffic services in the UK. These trends offer numerous opportunities to apply Operational Research in the 21st century, especially to improve information management. In a context of ATC privatisation, this paper investigates how applicable yield management (YM) policies are to European ATC. Necessary conditions for the use of YM are examined and difficulties in using YM for ATC are identified. Following this, possible YM solutions are outlined. Finally, the implications of YM for airspace users are addressed. 相似文献
999.
Bettina Wolf William J. Frith Scott Singleton Manlio Tassieri Ian T. Norton 《Rheologica Acta》2001,40(3):238-247
The rheological behaviour of suspensions is influenced by many parameters, one of which is the particle shape. For rigid
particle suspensions a number of studies demonstrate the effects of the particle aspect ratio. Indeed, fibres are widely used
as rheology modifiers in different materials such as synthetic polymers. This work is concerned with testing the hypothesis
that regularly shaped particles with aspect ratios larger than one that are made of gelled biopolymers could be used as rheology
modifiers for biopolymer solutions. Biopolymers, and mixtures thereof are a widely used ingredient in foods and other products
with structure functionality. Tailoring rheology modifiers by morphology offers an alternative to using different biopolymers.
It is demonstrated how biopolymer suspensions with regular spheroidal, or cylindrical particle shapes can be produced by gelling
the droplet phase of a liquid two phase biopolymer mixture in a shear field. Biopolymers were chosen such that gelation is
initiated by cooling. Shear-cooling at constant stresses leads to the formation of ellipsoidal particles. Cylindrical particles
can be generated by stepping up the shear stress prior to gelation, i.e., stretching the droplet phase into fibrils, and trapping
the shape prior to break-up through gelation.
Morphologies and steady shear rheological data for suspensions of the two biopolymers gellan and κ-carrageenan with an internal
phase volume of 0.2 are reported. The influence of particle shape on relative viscosity is pronounced. At high shear stresses
particle orientation leads to decreased viscosity with increasing particle aspect ratio. In the low shear region, higher aspect
ratio suspensions show higher viscosities. Additionally, the material properties, including the interfacial tension, which
influence the suspension morphology are reported.
Received: 3 March 2000 Accepted: 22 August 2000 相似文献
1000.
Christopher J. Cramer Armagan Kinal Marta Wloch Piotr Piecuch Laura Gagliardi 《ChemInform》2007,38(1):no-no
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. 相似文献