全文获取类型
收费全文 | 1459篇 |
免费 | 47篇 |
专业分类
电工技术 | 19篇 |
化学工业 | 142篇 |
金属工艺 | 29篇 |
机械仪表 | 17篇 |
建筑科学 | 61篇 |
矿业工程 | 27篇 |
能源动力 | 27篇 |
轻工业 | 127篇 |
水利工程 | 15篇 |
石油天然气 | 22篇 |
武器工业 | 1篇 |
无线电 | 209篇 |
一般工业技术 | 174篇 |
冶金工业 | 266篇 |
原子能技术 | 4篇 |
自动化技术 | 366篇 |
出版年
2023年 | 10篇 |
2022年 | 9篇 |
2021年 | 23篇 |
2020年 | 20篇 |
2019年 | 26篇 |
2018年 | 27篇 |
2017年 | 40篇 |
2016年 | 44篇 |
2015年 | 33篇 |
2014年 | 55篇 |
2013年 | 79篇 |
2012年 | 59篇 |
2011年 | 103篇 |
2010年 | 86篇 |
2009年 | 71篇 |
2008年 | 87篇 |
2007年 | 84篇 |
2006年 | 75篇 |
2005年 | 65篇 |
2004年 | 60篇 |
2003年 | 56篇 |
2002年 | 31篇 |
2001年 | 31篇 |
2000年 | 13篇 |
1999年 | 25篇 |
1998年 | 27篇 |
1997年 | 25篇 |
1996年 | 58篇 |
1995年 | 27篇 |
1994年 | 19篇 |
1993年 | 19篇 |
1992年 | 13篇 |
1991年 | 4篇 |
1990年 | 7篇 |
1989年 | 8篇 |
1988年 | 8篇 |
1987年 | 11篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 8篇 |
1975年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有1506条查询结果,搜索用时 15 毫秒
81.
A low-power, large-scale parallel video compression architecture for a single-chip digital CMOS camera is discussed in this paper. This architecture is designed for highly computationally intensive image and video processing tasks necessary to support video compression. Two designs of this architecture, an MPEG2 encoder and a DV encoder, are presented. At an image resolution of 640 × 480 pixels (MPEG2) and 720 × 576 (DV) and a frame rate of 25 to 30 frames per second, a computational throughput of up to 1.8 billion operations per second (BOPS) is required. This is supported in the proposed architecture using a 40 MHz clock and an array of 40 to 45 parallel processors implemented in a 0.2 m CMOS technology and with a 1.5 V supply voltage. Power consumption is significantly reduced through the single-chip integration of the CMOS photo sensors, the embedded DRAM technology, and the proposed pipelined parallel processors. The parallel processors consume approximately 45 mW of power resulting a power efficiency of 40 BOPS/W. 相似文献
82.
A new type of biosensor that combines the inexpensiveness and mass-produceability of reflection holograms with the selectivity and specificity of enzymes is described. pH-sensitive holographic sensors were fabricated from ionizable monomers incorporated into thin, polymeric, hydrogel films which were transformed into volume holograms using a diffusion method coupled with holographic recording, using a frequency-doubled Nd:YAG laser (532 nm). These holograms were used as transducer systems to monitor the pH changes associated with specific enzymatic reactions to construct prototype urea- and penicillin-sensitive biosensors. The diffraction wavelength (color) of the holographic biosensors was used to characterize their shrinkage and swelling behavior as a function of analyte concentration. The potential of these sensors for the measurement of the clinically and industrially important metabolites urea and penicillin G is demonstrated. 相似文献
83.
A glucose sensor comprising a reflection hologram incorporated into a thin, acrylamide hydrogel film bearing the cis-diol binding ligand, 3-acrylamidophenylboronic acid (3-APB), is described. The diffraction wavelength (color) of the hologram changes as the polymer swells upon binding cis-diols. The effect of various concentrations of glucose, a variety of mono- and disaccharides, and the alpha-hydroxy acid, lactate, on the holographic response was investigated. The sensor displayed reversible changes in diffraction wavelength as a function of cis-diol concentration, with the sensitivity of the system being dependent on the cis-diol tested. The effect of varying 3-APB concentration in the hydrogel on the holographic response to glucose was investigated, and maximum sensitivity was observed at a functional monomer concentration of 20 mol %. The potential for using this holographic sensor to detect real-time changes in bacterial cell metabolism was demonstrated by monitoring the germination and subsequent vegetative growth of Bacillus subtilis spores. 相似文献
84.
Orchard J Greif C Golub GH Bjornson B Atkins MS 《IEEE transactions on medical imaging》2003,22(11):1427-1435
Registration using the least-squares cost function is sensitive to the intensity fluctuations caused by the blood oxygen level dependent (BOLD) signal in functional MRI (fMRI) experiments, resulting in stimulus-correlated motion errors. These errors are severe enough to cause false-positive clusters in the activation maps of datasets acquired from 3T scanners. This paper presents a new approach to resolving the coupling between registration and activation. Instead of treating the two problems as individual steps in a sequence, they are combined into a single least-squares problem and are solved simultaneously. Robustness tests on a variety of simulated three-dimensional EPI datasets show that the stimulus-correlated motion errors are removed, resulting in a substantial decrease in false-positive and false-negative activation rates. The new method is also shown to decorrelate the motion estimates from the stimulus by testing it on different in vivo fMRI datasets acquired from two different 3T scanners. 相似文献
85.
Feature models are widely used in domain engineering to capture common and variant features among systems in a particular domain. However, the lack of a formal semantics and reasoning support of feature models has hindered the development of this area. Industrial experiences also show that methods and tools that can support feature model analysis are badly appreciated. Such reasoning tool should be fully automated and efficient. At the same time, the reasoning tool should scale up well since it may need to handle hundreds or even thousands of features a that modern software systems may have. This paper presents an approach to modeling and verifying feature diagrams using Semantic Web OWL ontologies. We use OWL DL ontologies to precisely capture the inter-relationships among the features in a feature diagram. OWL reasoning engines such as FaCT++ are deployed to check for the inconsistencies of feature configurations fully automatically. Furthermore, a general OWL debugger has been developed to tackle the disadvantage of lacking debugging aids for the current OWL reasoner and to complement our verification approach. We also developed a CASE tool to facilitate visual development, interchange and reasoning of feature diagrams in the Semantic Web environment. 相似文献
86.
MVA Processing of Speech Features 总被引:1,自引:0,他引:1
Chia-Ping Chen Jeff A. Bilmes 《IEEE transactions on audio, speech, and language processing》2007,15(1):257-270
In this paper, we investigate a technique consisting of mean subtraction, variance normalization and time sequence filtering. Unlike other techniques, it applies auto-regression moving-average (ARMA) filtering directly in the cepstral domain. We call this technique mean subtraction, variance normalization, and ARMA filtering (MVA) post-processing, and speech features with MVA post-processing are called MVA features. Overall, compared to raw features without post-processing, MVA features achieve an error rate reduction of 45% on matched tasks and 65% on mismatched tasks on the Aurora 2.0 noisy speech database, and an average 57% error reduction on the Aurora 3.0 database. These improvements are comparable to the results of much more complicated techniques even though MVA is relatively simple and requires practically no additional computational cost. In this paper, in addition to describing MVA processing, we also present a novel analysis of the distortion of mel-frequency cepstral coefficients and the log energy in the presence of different types of noise. The effectiveness of MVA is extensively investigated with respect to several variations: the configurations used to extract and the type of raw features, the domains where MVA is applied, the filters that are used, the ARMA filter orders, and the causality of the normalization process. Specifically, it is argued and demonstrated that MVA works better when applied to the zeroth-order cepstral coefficient than to log energy, that MVA works better in the cepstral domain, that an ARMA filter is better than either a designed finite impulse response filter or a data-driven filter, and that a five-tap ARMA filter is sufficient to achieve good performance in a variety of settings. We also investigate and evaluate a multi-domain MVA generalization 相似文献
87.
Despite frequent discussions of what it means to be normal in clinical, social, and personality psychology theory, the characteristics of individuals who call themselves normal are little understood. In 5 studies, the authors investigated various hypotheses concerning the nature of normality evaluations. The authors add to recent evidence that normality evaluations represent a distinct dimension of evaluative judgments, showing self-judgments of being normal (versus strange) to be relatively independent from self-judgments of being average (versus unique). Normality evaluations showed positive relations with communal traits such as agreeableness, conscientiousness, and emotional stability, and were negatively related to openness to experience. Supporting a broader hypothesis that normality evaluations may be involved in directing or motivating personality development processes, normality evaluations were positively associated with well-being and a sense of fitting in with one's peers, and individuals who felt abnormal felt a heightened sense that they needed to improve their personality. Finally, the personality correlates of normality evaluations were found to change over the lifespan, largely in parallel with the actual mean-level development of personality traits with age. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
88.
The internship has long been considered the capstone experience in the sequence of doctoral education in professional psychology. Since at least 1999, the number of available internship positions in the United States and Canada has been outstripped by the number of students seeking these positions. The resulting imbalance between supply and demand for internship positions has grown substantially since 2002 and now should be considered to have reached crisis proportions. Although no complete solution to this imbalance is imminently feasible, a comprehensive approach to addressing the crisis requires that both the supply of internships and the growth in demand be addressed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
89.
Jason McCormick Jeff Tyber Reginald DesRoches Ken Gall Hans J. Maier 《Canadian Metallurgical Quarterly》2007,133(9):1019-1029
This paper continues to address the overarching goal to provide a more unified understanding of NiTi shape memory alloys intended for use in structural applications by attempting to link standard processing practice and basic materials characterization to the deformation behavior of large diameter bars. Results from cyclic tensile tests performed on large diameter Ni-rich polycrystalline NiTi bars are presented. Coupon specimens taken from deformation processed bars with diameters of 12.7, 19.1, and 31.8?mm are tested along with their respective full-scale specimens. The coupon tests results reveal small and highly variable differences between specimens taken from the different size bars. The full-scale specimen tests continue to show the presence of the R phase, but lack a Lüders-like transformation. A comparison of the results suggests that coupon specimens provide only limited information in terms of the full-scale behavior. Full-scale tests using an earthquake-type loading then show similar behavior to the tensile cyclic tests suggesting the ability to use NiTi in structural applications. Overall, this paper and Tyber et al. 2007 provide a multiscale analysis of NiTi shape memory alloys to be used by both material scientist and civil engineers in the development of applications for NiTi. 相似文献
90.
Schimel Jeff; Hayes Joseph; Williams Todd; Jahrig Jesse 《Canadian Metallurgical Quarterly》2007,92(5):789
According to terror management theory, if the cultural worldview protects people from thoughts about death, then weakening this structure should increase death-thought accessibility (DTA). Five studies tested this DTA hypothesis. Study 1 showed that threatening Canadian participants' cultural values (vs. those of another culture) increased DTA on a word-fragment completion task. Study 2 showed that when participants could dismiss the threat, DTA remained low. Study 3 replicated the results of Study 1, but DTA was measured using a lexical decision task. Response latencies to death, negative, and neutral content were measured. Worldview threat increased DTA relative to accessibility for negative and neutral content. Study 4 showed that the DTA effect emerged independently of the arousal of anger or anxiety. Finally, Study 5 demonstrated that participants with a pro-creation (vs. pro-evolution) worldview had higher DTA after reading an anti-creation article. Discussion focused on theoretical implications and directions for further research. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献