全文获取类型
收费全文 | 376篇 |
免费 | 5篇 |
专业分类
电工技术 | 9篇 |
化学工业 | 74篇 |
金属工艺 | 6篇 |
机械仪表 | 13篇 |
建筑科学 | 3篇 |
能源动力 | 8篇 |
轻工业 | 37篇 |
水利工程 | 4篇 |
无线电 | 36篇 |
一般工业技术 | 59篇 |
冶金工业 | 97篇 |
原子能技术 | 4篇 |
自动化技术 | 31篇 |
出版年
2023年 | 4篇 |
2021年 | 5篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 3篇 |
2014年 | 3篇 |
2013年 | 12篇 |
2012年 | 12篇 |
2011年 | 13篇 |
2010年 | 13篇 |
2009年 | 7篇 |
2008年 | 13篇 |
2007年 | 12篇 |
2006年 | 12篇 |
2005年 | 17篇 |
2004年 | 16篇 |
2003年 | 9篇 |
2002年 | 15篇 |
2001年 | 7篇 |
2000年 | 10篇 |
1999年 | 11篇 |
1998年 | 19篇 |
1997年 | 15篇 |
1996年 | 16篇 |
1995年 | 9篇 |
1994年 | 6篇 |
1993年 | 8篇 |
1992年 | 3篇 |
1991年 | 9篇 |
1990年 | 6篇 |
1989年 | 9篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 9篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1977年 | 4篇 |
1976年 | 8篇 |
1974年 | 3篇 |
1960年 | 2篇 |
1958年 | 1篇 |
1957年 | 1篇 |
1956年 | 2篇 |
1955年 | 1篇 |
排序方式: 共有381条查询结果,搜索用时 15 毫秒
1.
In Experiment 1, a group of listeners with substantial hearing loss due to presbyacusis and a group of listeners with normal hearing were given three localization tests: a frontal plane test in which they judged whether sounds came from the left, overhead, or the right; a sagittal plane test in which they judged whether sounds came from directly in front, overhead, or behind; and an elevation test in which they judged the vertical position of sounds coming from in front. The two groups performed similarly on the frontal plane test, which chiefly depended upon their ability to use binaural localization cues. They performed differently on the sagittal plane and elevation tests, for which the predominant localization cues were spectral. The listeners with presbyacusis were substantially less accurate than those with normal hearing in both of these instances. They had particular difficulty judging source elevation, rarely scoring much above chance. Follow-up testing of a group of subjects in the early stages of presbyacusis showed localization performance that was intermediate to the other two groups, but far more like that of the normal-hearing listeners. In Experiment 2, additional tests were run with the following conditions designed to encourage improved performance by listeners with presbyacusic hearing loss: (1) filtering of stimuli to preclude masking of more informative high-frequency components by low frequencies; (2) simplification of the elevation test and greater spatial separation of its loudspeaker sources; and (3) use of hearing aids. Conditions 1 and 2 had no appreciable effect on performance; condition 3 significantly improved presbyacusic listeners' ability to localize in the sagittal plane, particularly when sounds came from the front. 相似文献
2.
K. A. Taylor J. B. Vander Sande M. Cohen 《Metallurgical and Materials Transactions A》1993,24(11):2585-2588
Y. OHMORI and I. TAMURA:Metall. Trans. A, 1992, vol. 23A, 相似文献
3.
J. Buytaert L. De Boeck F. Verbeure
C. Bricman
F. Cao C. De Clercq L. Etienne B. Goorens J. Lemonne F. Stichelbaut S. Tavernier G. Van Beek C. Vander Velde W. Van Doninck L. Van Lancker J. WickensE. Daubie
F. Defontaines F. Grard J. Kesteman O. Pingot C. Poiret 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1991,310(3):596-606The layout and construction of the muon drift chambers equipping the end caps of the DELPHI detector are described. The performance of this forward muon detection system, determined from cosmic ray tests and data collected during the first year of LEP operation, is presented. 相似文献
4.
The approach to the HIV-infected patient with pulmonary disease is summarized by the algorithms in Figures 3 and 4. These are not intended to be followed in a rigid step-wise fashion. Rather, the practitioner's knowledge of the patient with his or her accompanying medical risks influences the path taken, including the depth and the speed of the evaluation. For example, the patient with cough who is afebrile and breathing at 18 breaths a minute, with a normal chest radiograph and a CD4 count of 350 cells/mm3, is reasonably treated with a macrolide or cephalosporin for bacterial bronchitis and clinical follow-up while awaiting cultures (see Fig. 4). A febrile patient with a cough productive of thin mucus, but known to have a CD4 count of 60 cells/mm3 should be started on anti-PCP therapy while being evaluated for PCP with an induced sputum and if nondiagnostic, a bronchoscope despite a normal chest radiograph. Screening can be as simple as placing an oximeter on the patient's finger in the clinic. If the oxygen saturation of a patient with a normal chest radiograph is low, then the patient should be hospitalized and begun on treatment for PCP while diagnostic evaluation is initiated. If the oxygen saturation is normal, the patient can be exercised to elicit desaturation. If there is no desaturation, PCP is unlikely. If the results are equivocal (i.e., a decrease in saturation, but less than 3%), rest and exercise arterial blood gases can be performed, along with a Dlco-Gallium scanning can be done in patients known to have abnormal Dlco or those who cannot exercise. Patients with focal infiltrates who have acute onset of symptoms (see Fig. 4) commonly have bacterial infections, but the possibility of PCP or TB should not be dismissed. Induced sputum should be examined if TB or PCP is suspected. Patients who are severely ill might go quickly to bronchoscopy without awaiting improvement on empiric therapy. The patient with diffuse infiltrates (see Fig. 4) needs no screening because the presence of disease is apparent from the radiograph. The diagnostic part quickly leads to bronchoscopy for these patients and the initiation of therapy for PCP when suspected. In patients with known pulmonary KS, gallium scanning can be helpful to rule out acute infection, but bronchoscopy is warranted if the patient is severely ill, or at high risk for PCP. This approach should avoid unnecessary procedures in patients with simple bacterial infections, without missing opportunistic infections and tumors. 相似文献
5.
J.H. Trienekens P.M. WognumA.J.M. Beulens J.G.A.J. van der Vorst 《Advanced Engineering Informatics》2012,26(1):55-65
Food supply chains are increasingly complex and dynamic due to (i) increasing product proliferation to serve ever diversifying and globalising markets as a form of mass customisation with resulting global flows of raw materials, ingredients and products, and (ii) the need to satisfy changing and variable consumer and governmental demands with respect to food safety, animal welfare, and environmental impact. Transparency in the food supply chain is essential to guarantee food quality and provenance to all users of food and food products. Intensified information exchange and integrated information systems involving all chain actors are needed to achieve transparency with respect to a multitude of food properties.In this paper, specific challenges of food supply chains are highlighted. Major elements are addressed that support transparency to consumers, the government and food companies, which are considered the claimants of transparency. Elements considered to be enablers of transparency are governance mechanisms, quality and safety standards and information exchange. The paper specifies these transparency claimants and enablers for food supply chains and identifies major information system functions and information technology applications needed to comply with transparency demands. It thereby provides a framework for transparency analysis in food supply chains. 相似文献
6.
Robert K. Vander Meer Francisco Alvarez Clifford S. Lofgren 《Journal of chemical ecology》1988,14(3):825-838
TheSolenopsis invicta trail pheromone is synthesized by the Dufour's gland and is released through the sting apparatus. The recruitment subcategory of theS. invicta trail pheromone was shown to be composed of a mixture of the orientation pheromone, (Z,E)--farnesene and an unidentified homosesquiterpene consisting of three rings and one double bond (C-1). C-1 is present in worker Dufour's glands at only 75 pg per worker equivalent. This is the first report that demonstrates that different exocrine products from the same gland control different subcategories of behavior related to mass recruitment. 相似文献
7.
Vander Wal RL 《Applied optics》1996,35(33):6548-6559
Theoretical predictions suggest that soot particle size and local gas temperature affect both the spectral intensity and the temporal evolution of laser-induced incandescence. A discussion of both the physical structure and the theoretical absorption models of soot aggregates is presented, suggesting that the soot particle size relevant to laser-induced incandescence (LII) is the primary particle size regardless of whether the primary particle exists individually or is assembled into an aggregate. Experimental results of LII measurements in a laminar gas-jet flame with different signal collection strategies for the LII are presented. These results suggest that (a) signal integration during the laser pulse is essential for minimizing particle size and local temperature bias in the LII signal, (b) signal integration times subsequent to the laser pulse produce a size and local gas-temperature-dependent bias in the LII signal with long integration times more sensitive to these effects, and (c) long wavelength detection produces less of a size and local gas-temperature-dependent bias than short wavelength detection. 相似文献
8.
Vincent Verhaert Hans Druyts Dorien Van Deun Vasileios Exadaktylos Johan Verbraecken Marie Vandekerckhove Bart Haex Jos Vander Sloten 《International Journal of Industrial Ergonomics》2012,42(5):489-498
This study aims at evaluating spinal alignment during sleep by combining personalized human models with mattress indentation measurements. A generic surface model has been developed that can be personalized based on anthropometric parameters derived from silhouette extraction. Shape assessment of the personalized surface models, performed by comparison with 3-D surface scans of the trunk, showed a mean unsigned distance of 9.77 mm between modeled and scanned surface meshes. The surface model is combined with an inner skeleton model, allowing the model to simulate distinct sleep postures. An automatic fitting algorithm sets the appropriate degrees of freedom to position the model on the measured indentation according to the adopted sleep posture. Validation on lateral sleep positions showed good intraclass correlations (0.73–0.88) between estimated and measured angular spinal deformations, indicating that silhouette-derived body shape models provide a valuable tool for the unobtrusive assessment of spinal alignment during sleep.Relevance to industry: A common drawback of the available techniques to assess spinal deformation on bedding systems is that they interfere with the actual sleep process. The current study presents a novel method based on silhouette-derived body shape models in order to estimate spine shape during sleep unobtrusively. 相似文献
9.
Persky Irena; Spring Bonnie; Wal Jillon S. Vander; Pagoto Sherry; Hedeker Donald 《Canadian Metallurgical Quarterly》2005,24(2):153
The authors tested whether adherence to simultaneous health behavior changes was unitary or domain specific among 76 women who modified smoking, eating, and physical activity to accomplish smoking cessation plus weight control. Random-effects regression analyses showed that adherence to both smoking and diet plans declined linearly and covaried positively; their association tended to grow stronger over time. In contrast, physical activity plan adherence did not change over time and was unrelated to other domains. At the end of treatment, 65%, 30.5%, and 25% adhered well or excellently to smoking, diet, and activity treatments, respectively. Findings support both unitary and domain-specific aspects of adherence and suggest that among smokers, smoking and eating behaviors may have similarities unshared by physical activity. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
10.
Supply Chain Management in Food Chains: Improving Performance by Reducing Uncertainty 总被引:3,自引:0,他引:3
J.G.A.J. van der Vorst A.J.M. Beulens W. de Wit P. van Beek 《International Transactions in Operational Research》1998,5(6):487-499
This paper investigates the impact of Supply Chain Management on logistical performance indicators in food supply chains. From a review of quantitative and more qualitative managerial literature, we believe that Supply Chain Management should be concerned with the reduction or even elimination of uncertainties to improve the performance of the chain. The following clusters of sources of uncertainty are identified: order forecast horizon, input data, administrative and decision processes and inherent uncertainties. For each source of uncertainty, several improvement principles are identified. A case study was conducted in a food chain in which a simulation model helped quantify the effects of alternative configurations and operational management concepts. By comparing this simulation study with a pilot study, the model is validated against real data, and organisational consequences are identified. The results of the case study suggest that reduction of uncertainties can improve service levels significantly, although current supply chain configurations restrict possible benefits. The availability of real-time information systems is found to be a requirement for obtaining efficient and effective Supply Chain Management concepts. 相似文献