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141.
Carlo H. Séquin Author Vitae 《Computer aided design》2005,37(7):737-750
The role of computers and of computer-aided design tools for the creation of geometrical shapes that will be judged primarily by aesthetic considerations is reviewed. Examples are the procedural generation of abstract geometrical sculpture or the shape optimization of constrained curves and surfaces with some global ‘cost’ functional. Different possibilities for such ‘beauty functionals’ are discussed. Moreover, rapid prototyping tools based on layered manufacturing now add a new dimension to the visualization of emerging designs. Finally, true interactivity of the CAD tools allows a more effective exploration of larger parts of the design space and can thereby result in an actual amplification of the creative process. 相似文献
142.
Luca Becchetti Paola Bertolazzi Carlo Gaibisso Giorgio Gambosi 《Theoretical computer science》2002,270(1-2):341-359
In this paper we deal with the problem of designing virtual path layouts in ATM networks when the hop-count is given and the load has to be minimized. We first prove a lower bound for networks with arbitrary topology and arbitrary set of connection requests. This result is then applied to derive lower bounds for the following settings: (i) one-to-all (one node has to be connected to all other nodes of the network) in arbitrary networks; (ii) all-to-all (each node has to be connected to all other nodes in the network) in several classes of networks, including planar and k-separable networks and networks of bounded genus. We finally study the all-to-all setting on two-dimensional meshes and we design a virtual path layout for this problem. When the hop-count and the network degree are bounded by constants, our results show that the upper bounds proposed in this paper for the one-to-all problem in arbitrary networks and for the all-to-all problem in two-dimensional mesh networks are asymptotically optimal. Moreover, the general lower bound shows that the algorithm proposed in Gerstel (Ph.D. Thesis, Technion-Haifa, Israel, 1995) for the all-to-all problem in k-separable networks is also asymptotically optimal. The upper bound for mesh networks also shows that the lower bound presented in this paper for the all-to-all problem in planar networks is asymptotically tight. 相似文献
143.
It has been known for many years that in a circular counterflow pipe there exist two different states of turbulence of helium II: the T-1 state, which appears at low values of heat flux, and the T-2 state, which appears suddenly at higher heat flux and is characterized by a much higher density of quantized vortex lines. Until now the nature of the two turbulent states has been a mystery. To understand this problem we have addressed the issue of the velocity profile of the normal fluid and its stability. The computed critical heat flux of the transition from the T-1 state to the T-2 state is found to be in good agreement with the observations. The result indicates that in the T-1 state the superfluid is turbulent but the normal fluid is still laminar. The T-1 to T-2 transition corresponds to the onset of normal fluid turbulence. 相似文献
144.
The isotopic ordering of H2–D2 mixtures adsorbed at low temperature on graphite in the monolayer range is measured by small angle neutron scattering (SANS). We show that below 8 K, solid mixtures exhibit isotopic clustering at large density (monolayer completion) and a tendency towards the formation of ordered compounds for smaller density (near the commensurate structure). 相似文献
145.
146.
Gian Carlo Alfonso Luigi Olivero Antonio Turturro Enrico Pedemonte 《Polymer International》1973,5(2):141-154
The self-seeding crystallisation technique is applied to a dilute solution of polyethylene in xylene containing, in suspension, foreign particles; data concerning some pigments usually employed for colouring the plastics are reported. It is shown that this method allows easy demonstration of the interactions existing between the dissolved polymer and the pigment; at the same time, it is possible to study the morphology which is evolved as a consequence of these interactions under particularly simple conditions as only a small amount of polymer crystallises on the pigment particles. The behaviour of several pigments is consistent with the results obtained by crystallising the bulk polyethylene coloured with the same pigments. Some unusual morphologies are made evident. 相似文献
147.
Nowadays, the use of implanted devices is a well-acknowledged practice in the field of orthopaedic and dental surgery. Scientific research and clinical experience suggest that the successful exploitation of these devices mainly depends on osseointegration, considered as both anatomical congruency and load-bearing capacity. Indeed, the osseointegration process is influenced by a wide range of factors: anatomical location, implant size and design, surgical procedure, loading effects, biological fluids, age and sex, and, in particular, surface characteristics. For this reason, several attempts have been aimed at modifying implant surface composition and morphology to optimise implant-to-bone contact and improve integration. Preliminary interactions between implanted materials and biological environment are deemed to be governed by the surface properties; they control the amount and quality of cell adhesion on the surface and, consequently, cell/tissue growth. Thus, surface properties govern new bone tissue formation and implant osseointegration. This paper reviews the state of art in the field of physical, chemical and biochemical treatments commonly used on Ti-based biomaterials for the production of biomedical devices. In particular, roughness characteristics due to physical and chemical techniques are investigated; the development of biologically active surfaces by means of biochemical functionalisation is also considered. 相似文献
148.
Perri Roberta; Serra Laura; Carlesimo Giovanni Augusto; Caltagirone Carlo 《Canadian Metallurgical Quarterly》2007,21(5):549
Episodic long-term, short-term, and implicit memory were investigated in 79 elderly subjects who fulfilled criteria for the amnestic form of mild cognitive impairment (a-MCI; i.e., by having an idiopathic amnestic disorder with absence of impairment in cognitive areas other than memory and without confounding medical or psychiatric conditions) and who developed Alzheimer's disease (AD) after 2 years as well as in 111 subjects affected by a-MCI who did not develop dementia. Results document a memory profile in a-MCI subjects characterized by preserved short-term and implicit memory and extensive impairment of episodic long-term memory. In virtually all episodic memory indexes examined (learning, forgetting, recognition abilities), a-MCI subjects who converted to AD were more severely impaired than were subjects who did not become demented. This memory profile, which closely resembles that exhibited by amnestic patients with bilateral mesial-temporal lobe lesions, confirms a precocious phase in preclinical AD characterized by selective involvement of mesial-temporal areas and worsening of the memory impairment as atrophic changes progress in hippocampal structures. In this context of pervasive episodic memory impairment, tests assessing the free recall of verbal material following a delay interval demonstrated the greater sensitivity to memory deficits of a-MCI subjects who developed AD. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
149.
Alessio Gagliardi Thomas A. Niehaus Thomas Frauenheim Alessandro Pecchia Aldo Di Carlo 《Journal of Computational Electronics》2007,6(1-3):345-348
In this paper we present calculations of ballistic transport in molecular wires. The calculations are performed using an approximated
version of the GW correction in the plasmon-pole framework, which is used to improve the starting Density Functional Theory energy spectrum
of the molecule between metallic leads. We show that this correction reduces the error of the correlation part for the electron
energy. Finally a model with complex bands is implemented in order to get the damping regime for long polymers. 相似文献
150.
Carlo S. Iorio Oleg A. Kabov Jean-Claude Legros 《Microgravity science and technology》2007,19(3-4):27-29
In this paper, some of the preparatory experiments of the ESA sponsored space program CIMEX-1 are presented. A liquid layer of variable thickness is subject to a flow of inert gas. The non-uniform evaporation induced by the gas flow creates a temperature gradient parallel to the interface triggering in that way thermocapillary convection. The combined action of evaporation, thermocapillarity and gravity has been not completely clarified both theoretically and experimentally. The experiment presented in this work concerns a liquid layer of ethanol of 2.2 mm thickness in presence of a mass flow of Nitrogen whose intensity varies in the range of hundreds of milliliter per minute. The experiments were performed at an initial liquid temperature of 21°C. The patterns observed are strongly dependent on the flow rate of inert gas. A change in the instability patterns has been observed for a gas flow of about 1.7 l/min. 相似文献