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41.
The anodic behavior of gold has been investigated in presence of chloride and/or water in 1-butyl-3-methylimidazolium methanesulfonate (BMI CH3SO3) ionic liquid (IL). The cyclic voltammetry (CVs) in presence of chloride ions shows two waves attributed to the oxidation of the gold electrode which occurs under two steps: the first one is attributed to the electrochemical dissolution of gold into to gold(I), while the second one is attributed to an overlap of the chloride oxidation step as well as the oxidation of Au(I) to Au(III). Furthermore the determination of water and chloride content in IL allowed observing that the passive layer induced by water could be removed under chloride. Thanks to those results we were able to clarify the conditions of gold recovering in this kind of electrolyte. 相似文献
42.
CJ Reist GE Archer CJ Wikstrand DD Bigner MR Zalutsky 《Canadian Metallurgical Quarterly》1997,57(8):1510-1515
The crystal structure is reported of a complex between the dodecanucleotide sequence d(CGCGAATTCGCG)2and an analogue of the DNA binding drug Hoechst 33258, in which the piperazine ring has been replaced by an amidinium group and the phenol ring by a phenylamidinium group. The structure has been refined to an R factor of 19.5% at 2.2 A resolution. The drug is held in the minor groove by five strong hydrogen bonds, together with bridging water molecules at both ends. There are few other contacts with the floor of the groove, indicating a lack of isohelicity with the groove and suggesting (i) that the observed high DNA affinity of this drug is primarily due to the array of hydrogen bonds and (ii) that these more than compensate for its poor isohelicity. 相似文献
43.
Rodney G. TeKrony Glen D. Sanders Billy Cummins 《Canadian Metallurgical Quarterly》2004,130(2):148-153
In the early days of the Reclamation Service, the criteria for irrigability of lands generally consisted of two elements: (1) is water available? and (2) can we get the water to the land? Within a few years, many of the early projects were experiencing reduced agricultural productivity and reduced ability to repay construction loans because the soils were becoming waterlogged and saline. By 1915, construction of subsurface drainage facilities had been initiated on several projects. However, at the time, subsurface drainage was more of an art than a science. Much of the world’s experience with agricultural drainage had been gained in humid areas which were quite different from arid areas. With no standards and limited knowledge of ground water movement, these early drainage efforts met with varying degrees of success. This paper summarizes the development of scientific methods to ensure successful application of drainage in a sustainable irrigated agriculture. Reclamation has introduced these methods to solve irrigated drainage problems at the international level. This paper will address the international experience, and how the same design and construction methods and procedures are now being used to design corrective drainage facilities for dams and other major structures and to support environmental enhancement programs. 相似文献
44.
In this paper, we establish a probabilistic framework for adaptive transform coding that leads to a generalized Lloyd type algorithm for transform coder design. Transform coders are often constructed by concatenating an ad hoc choice of transform with suboptimal bit allocation and quantizer design. Instead, we start from a probabilistic latent variable model in the form of a mixture of constrained Gaussian mixtures. From this model, we derive an transform coder design algorithm, which integrates optimization of all transform coder parameters. An essential part this algorithm is our introduction of a new transform basis-the coding optimal transform-which, unlike commonly used transforms, minimizes compression distortion. Adaptive transform coders can be effective for compressing databases of related imagery since the high overhead associated with these coders can be amortized over the entire database. For this work, we performed compression experiments on a database of synthetic aperture radar images. Our results show that adaptive coders improve compressed signal-to-noise ratio (SNR) by approximately 0.5 dB compared with global coders. Coders that incorporated the coding optimal transform had the best SNRs on the images used to develop the coder. However, coders that incorporated the discrete cosine transform generalized better to new images. 相似文献
45.
A technique is described that permits the rapid determination of all four noise parameters of a MESFET or HEMT at wafer level. The fully automated procedure, which has been implemented in the 2-8 GHz range, uses 16 accurately measured, very repeatable source impedance standards. The standards have been selected for optimum coverage of the input impedance plane to result in stable and rapidly convergent least-squares solutions for the minimum noise figure, optimum source impedance, and noise resistance of practical devices. The resultant system is very stable and produces accurate noise parameters for a wide range of devices 相似文献
46.
A radiotracer technique has been used to measure both mercury self-diffusion and surface concentration values in bulk and
liquid phase epitaxy, LPE, grown Hg1−xCdxTe. A high resolution sectioning technique has allowed profiling of thin epitaxial layers in submicron steps. Hg1-xCdxTe samples with composition values betweenx
Cd= 0.16 and 0.23 were isothermally annealed in carefully controlled and monitored diffusion con-ditions. Mercury reservoirs
containing Hg203 were used to provide vapour diffusion sources during closed tube isothermal anneals in the temperature range 300° C to 400°
C. Evidence has been found which may indicate the presence of two components in the radio-tracer profiles for both bulk and
epitaxially grown material. In some cases it was possible to estimate two diffusion coefficients,D
1andD
2, from the near surface and deeply penetrating components, respectively. Our results forD
1andD
2are compared with other work. For bulk material annealed at 400° C under a saturated mercury pressureD
1= 2.0 x 10-12cm2s-1 andD
2= 1.1 x 10-11cm2s−1. Diffusion coefficients at 310° C under saturated mercury pressure, have been measured in bulk and epitaxial material. Close
agreement was found between these results with an average value ofD
1= 1.4 x 10−13cm2s−1. We believe this to be the first time radiotracer results for epitaxial material have been presented. We have collated diffusion
data, as a function of reciprocal temperature, from several workers and suggest there is evidence for a change in the activation
energy for mercury diffusion around 350° C. This may be due to a change in the dominant diffusion mechanism. 相似文献
47.
The experiences of 3 social psychologists asked to evaluate (and improve) a series of large-scale programs designed to change energy-related attitudes and behavior are described. The research generated significant change but also substantial conflict involving both the utility companies being evaluated and the state agency that commissioned the evaluation. This experience is reviewed with an eye to maximizing the usefulness of future efforts to apply social psychology in complex and potentially conflicted public policy arenas. The difference between influence and power models of applied research is discussed, and possible remedies are examined for social psychologists undertaking future research similar in scale, policy consequences, or potential controversy. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
48.
Greater male than female variability is found in behavioral and morphological traits in animals. A theory that greater male variability is associated with variability in parental investment is described and contrasted with sexual strategies theory, which posits no sex differences in variability. Predictions from the theories were tested through meta-analyses of variance ratios for data sets involving sexually selected characteristics analyses (physical aggression and 5 aspects of mate choice) and 2 unlikely to have resulted from sexual selection (anger and self-esteem). Variation was significantly greater among men than women in 5 of the 6 former data sets and was similar for men and women in the latter 2 data sets, broadly supporting the predictions. A further analysis extends the theory to intellectual abilities. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
49.
Billy L. Crynes 《工程教育杂志》1997,86(4):301-304
In 1992 only four engineering programs required student ownership of computers. Today that number is 14. However, a recent survey of United States engineering deans indicates in the next three years over 100 engineering programs may require student computer ownership in some form. Most faculty and administrators recognize that student computer ownership is simply the next step in the continuum of calculational power in engineering curricula having evolved from simple pencil and paper, then to slide rule, hand held calculators, and now computers. Everyone agrees that those who hire our graduates expect them to be fully comfortable and competent with the enhanced computational capabilities, modeling, simulation, word processing, spread sheeting, and other hardware and software tools available. However, the more exciting reason for ownership, and one that holds the greatest promise of drastically changing the teaching/learning enterprise, is that proper application of information technologies will permit us to change how students learn and to improve how faculty and student time is utilized. 相似文献
50.
The authors have developed a method to measure an effective base drift field and the base transit-time reduction factor of bipolar transistors, by measuring the excess phase of the base transport factor. This technique relies on measuring small-signal characteristics of the transistor at a low frequency and following the phase of the transconductance at the frequency approaching and exceeding the unit current gain frequency (f T). With this technique, the authors verify that the effective drift inside the base of Si bipolar transistors decreases with increased base implantation energy and thermal treatment. Such directly measured drift-dependent base transport provides additional insight for optimizing processing used in bipolar technology development 相似文献