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991.
Sam Van Wassenbergh Peter Aerts Anthony Herrel 《Journal of the Royal Society Interface》2006,3(9):507-514
The magnitude of sub-ambient pressure inside the bucco-pharyngeal cavity of aquatic animals is generally considered a valuable metric of suction feeding performance. However, these pressures do not provide a direct indication of the effect of the suction act on the movement of the prey item. Especially when comparing suction performance of animals with differences in the shape of the expanding bucco-pharyngeal cavity, the link between speed of expansion, water velocity, force exerted on the prey and intra-oral pressure remains obscure. By using mathematical models of the heads of catfishes, a morphologically diverse group of aquatic suction feeders, these relationships were tested. The kinematics of these models were fine-tuned to transport a given prey towards the mouth in the same way. Next, the calculated pressures inside these models were compared. The results show that no simple relationship exists between the amount of generated sub-ambient pressure and the force exerted on the prey during suction feeding, unless animals of the same species are compared. Therefore, for evaluating suction performance in aquatic animals in future studies, the focus should be on the flow velocities in front of the mouth, for which a direct relationship exists with the hydrodynamic force exerted on prey. 相似文献
992.
Memorializes Donald L. Thistlethwaite, who made important contributions to the birth of cognitive psychology. His interests centered on human logic & its distortions. His studies included examinations of latent learning, persuasive communication and attitude change, and student achievement and attitudes. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
993.
Neiderhiser Jenae M.; Bussell Danielle A.; Pike Alison; Plomin Robert; Simmens Sam; Howe George W.; Hetherington E. Mavis; Reiss David 《Canadian Metallurgical Quarterly》1999,35(5):1265
This article addresses concerns raised by M. C. Neale (see record 1999-15302-008) in his commentary on the D. A. Bussell et al. (see record 1999-15302-007) Nonshared Environment in Adolescent Development (NEAD) study. These concerns fall into two categories: (a) model assumptions and sample design and (b) testing of alternative models. The validity of the assumptions of quantitative genetic models is a concern for all researchers in this area. Discussion of those assumptions in this reply is brief and focuses on those most relevant to the NEAD sample. The two alternative models proposed by Neale were designed to provide alternatives to the large shared environmental effect found in the original report of Bussell et al. Because these alternative models did not provide a better fit, the appropriateness of Bussell et al.'s basic model and the importance of shared environmental influences for explaining the association among family subsystems are supported. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
994.
We determine the weakest failure detector to solve nonuniform consensus in any environment, i.e., regardless of the number of faulty processes. Together with previous results, this closes all aspects of the following question: What is the weakest failure detector to solve (uniform or nonuniform) consensus in any environment? 相似文献
995.
H. Padma Kumar James T. Joseph J. K. Thomas K. Joy Sam Solomon 《Journal of Materials Science: Materials in Electronics》2009,20(6):551-554
Pr
x
Y1−x
TiTaO6 solid solutions were prepared through the solid state ceramic route. The materials were sintered in the range 1,525–1,600 °C.
The structure of the system was analyzed by X-ray diffraction methods. The scanning electron microscopic images show the co-existence
of two phases in the composite. The dielectric constant (εr), temperature coefficient of resonant frequency (τf) and the unloaded quality factor (Q
u) are measured in the microwave frequency region using cavity resonator method. The dielectric constant (εr) varies from 17.6 to 39.6 and temperature coefficient of resonant frequency (τf) from −52.2 to +55.9 ppm/°C. These variations are in accordance with the structural variation. Very low temperature coefficient
of resonant frequency and high quality factor were obtained for x = 0.2, 0.23 and 0.24 and are useful materials for practical applications. 相似文献
996.
997.
Steven Bradshaw Willem Louw Cariné van der Merwe Howard Reader Sam Kingman Ma?gorzata Celuch Weronika Kijewska 《The Journal of microwave power and electromagnetic energy》2007,40(4):228-240
Microwave heating of mineral ores had previously been shown to result in process benefits such as reduced strength and improved mineral liberation, but the economics of the process were not attractive and no attention was given to feasible scale-up. This paper provides an overview of the multi-disciplinary approach that has been required to address these failings and develop the technology to pilot scale. Thermal stress simulations show that the operation at high power densities and short residence times is the optimal operating strategy. Experiments using high power densities (approximately 10(9) W/m3 absorbing phase) and short residence times (approximately 0.1 s) were used to confirm that the benefits can now be achieved at economically viable microwave energy inputs (approximately 1 kWh/t). In order to design applicators, reliable measurement of effective microwave properties of crushed ores is required. A method has been developed to extract dielectric properties when the sample thickness is a multiple of half a guide wavelength at some point in the measurement band. Finite difference time domain modeling has been used to design and simulate applicators. A transverse E field applicator with a reflection compensating step has been developed, and a unit with a capacity of > 10 tons/h is being tested. Preliminary economic analysis shows that the overall cost of the process will be between US $0.16 - 0.85 per ton of ore. 相似文献
998.
Leonard M. Tender Sam A. Gray Ethan Groveman Daniel A. Lowy Peter Kauffman Julio Melhado Robert C. Tyce Darren Flynn Rose Petrecca Joe Dobarro 《Journal of power sources》2008
Here we describe the first demonstration of a microbial fuel cell (MFC) as a practical alternative to batteries for a low-power consuming application. The specific application reported is a meteorological buoy (ca. 18-mW average consumption) that measures air temperature, pressure, relative humidity, and water temperature, and that is configured for real-time line-of-sight RF telemetry of data. The specific type of MFC utilized in this demonstration is the benthic microbial fuel cell (BMFC). The BMFC operates on the bottom of marine environments, where it oxidizes organic matter residing in oxygen depleted sediment with oxygen in overlying water. It is maintenance free, does not deplete (i.e., will run indefinitely), and is sufficiently powerful to operate a wide range of low-power marine-deployed scientific instruments normally powered by batteries. Two prototype BMFCs used to power the buoy are described. The first was deployed in the Potomac River in Washington, DC, USA. It had a mass of 230 kg, a volume of 1.3 m3, and sustained 24 mW (energy equivalent of ca. 16 alkaline D-cells per year at 25 °C). Although not practical due to high cost and extensive in-water manipulation required to deploy, it established the precedence that a fully functional scientific instrument could derive all of its power from a BMFC. It also provided valuable lessons for developing a second, more practical BMFC that was subsequently used to power the buoy in a salt marsh near Tuckerton, NJ, USA. The second version BMFC has a mass of 16 kg, a volume of 0.03 m3, sustains ca. 36 mW (energy equivalent of ca. 26 alkaline D-cells per year at 25 °C), and can be deployed by a single person from a small craft with minimum or no in-water manipulation. This BMFC is being further developed to reduce cost and enable greater power output by electrically connecting multiple units in parallel. Use of this BMFC powering the meteorological buoy highlights the potential impact of BMFCs to enable long term (persistent) operation of durable low-power marine instruments (up to 100 mW average power consumption) far longer than practical by batteries. 相似文献
999.
Jong Soo Ko Min Gon Lee Jeong Sam Han Jeung Sang Go Bosung Shin Dae‐Sik Lee 《ETRI Journal》2006,28(3):389-392
In this letter, a laterally‐driven bistable electromagnetic microrelay is designed, fabricated, and tested. The proposed microrelay consists of a pair of arch‐shaped leaf springs, a shuttle, and a contact bar made from silicon, low temperature oxide (LTO), and gold composite materials. Silicon‐on‐insulator wafers are used for electrical isolation and releasing of the moving microstructures. The high‐aspect‐ratio microstructures are fabricated using a deep reactive ion etching (DRIE) process. The tandem‐typed leaf springs with a silicon/gold composite layer enhance the mechanical performances while reducing the electrical resistance. A permanent magnet is attached at the bottom of the silicon substrate, resulting in the generation of an external magnetic field in the direction vertical to the surface of the silicon substrate. The leaf springs show bistable characteristics. The resistance of the pair of leaf springs was 7.5 Ω, and the contact resistance was 7.7 Ω. The relay was operated at ±0.12 V. 相似文献
1000.
A procedure for exploiting a two-dimensional (2D) explicit, numerical computer code for the 3D formulation of dynamic lateral soil-pile interactions is considered. The procedure is applied to two models using simultaneous computation of a series of plane strain boundary value problems, each of which represents a horizontal layer of soil. The first model disregards the shear forces developed between the horizontal layers, and may be considered as a generalized Winkler model. The second model takes account of these forces by coupling the behavior of the horizontal layers. Several verification problems for a single pile and pile groups in a homogeneous soil layer modeled as a viscoelastic material were solved and compared to known solutions in order to assess the reliability of the models. Excellent agreement was observed between results of the present analyses and existing solutions. 相似文献