全文获取类型
收费全文 | 790篇 |
免费 | 10篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 9篇 |
化学工业 | 84篇 |
金属工艺 | 16篇 |
机械仪表 | 15篇 |
建筑科学 | 59篇 |
能源动力 | 13篇 |
轻工业 | 48篇 |
水利工程 | 5篇 |
石油天然气 | 2篇 |
无线电 | 74篇 |
一般工业技术 | 119篇 |
冶金工业 | 287篇 |
原子能技术 | 4篇 |
自动化技术 | 68篇 |
出版年
2022年 | 9篇 |
2021年 | 8篇 |
2020年 | 8篇 |
2019年 | 12篇 |
2018年 | 6篇 |
2017年 | 9篇 |
2016年 | 8篇 |
2015年 | 8篇 |
2014年 | 7篇 |
2013年 | 30篇 |
2012年 | 21篇 |
2011年 | 31篇 |
2010年 | 28篇 |
2009年 | 17篇 |
2008年 | 23篇 |
2007年 | 22篇 |
2006年 | 21篇 |
2005年 | 19篇 |
2004年 | 13篇 |
2003年 | 13篇 |
2002年 | 17篇 |
2001年 | 18篇 |
2000年 | 15篇 |
1999年 | 18篇 |
1998年 | 74篇 |
1997年 | 35篇 |
1996年 | 34篇 |
1995年 | 28篇 |
1994年 | 23篇 |
1993年 | 26篇 |
1992年 | 16篇 |
1991年 | 8篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 12篇 |
1987年 | 13篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 6篇 |
1983年 | 13篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1978年 | 13篇 |
1977年 | 10篇 |
1976年 | 18篇 |
1975年 | 8篇 |
1974年 | 4篇 |
1973年 | 4篇 |
排序方式: 共有803条查询结果,搜索用时 0 毫秒
91.
92.
K Tolidis P Crawford C Stephens Y Papadogiannis C Plakias 《Canadian Metallurgical Quarterly》1998,14(5):214-215
The development of computer-assisted learning software packages is a relatively new field of computer application. The progress made in personal computer technology toward more user-friendly operating systems has stimulated the academic community to develop computer-assisted learning for pre- and postgraduate students. The ability of computers to combine audio and visual data in an interactive form provides a powerful educational tool. The purpose of this study was to develop and evaluate a computer-assisted learning package on dental traumatology. This program contains background information on the diagnosis, classification, and management of dental injuries in both the permanent and the deciduous dentitions. It is structured into chapters according to the nature of the injury and whether injury has occurred in the primary or permanent dentition. At the end of each chapter there is a self-assessment questionnaire as well as references to relevant literature. Extensive use of pictures and video provides a comprehensive overview of the subject. 相似文献
93.
DS Liss DA Waller BD Kennard D McIntire P Capra J Stephens 《Canadian Metallurgical Quarterly》1998,37(5):536-544
BACKGROUND: In the adult respiratory distress syndrome, nitric oxide (NO) inhalation improves oxygenation through reducing ventilation-perfusion mismatching, but detailed information on the pulmonary effects of NO inhalation in septic shock is scarce. The present study investigated the effects of inhaled NO on alveolar dead space (Vdalv) and venous admixture as well as on respiratory system compliance (Crs) and respiratory system resistance (Rrs) in a porcine model of septic shock. Protective effects of NO are discussed. METHODS: Thirteen anaesthetised and ventilated pigs were given an infusion of endotoxin for an observation time of 220 min to induce acute lung injury (ALI). In the NO-early group (n=6), an inhalation of 60 ppm NO was started simultaneously with the endotoxin infusion and continued for 190 min. In 7 control/NO-late animals, 60 ppm NO was administered for 30 min following 190 min of endotoxin infusion. Haemodynamics, single-breath CO2-, pressure-, and flow signals were recorded. RESULTS: Endotoxin induced haemoconcentration, pulmonary vasoconstriction, and a decrease in Crs, while venous admixture, Vdalv, and Rrs increased. In the NO-early group, the pulmonary vasoconstriction was attenuated, no increase in pulmonary venous admixture or in Vdalv was seen before cessation of NO, and the improvements in oxygenation outlasted the NO inhalation. In the control/NO-late group, the NO inhalation reversed the changes in dead space and venous admixture. NO had no effect on the changes in respiratory mechanics. CONCLUSION: In porcine ALI, 60 ppm NO diminishes pulmonary vasoconstriction and improves gas exchange by reducing pulmonary venous admixture and alveolar dead space, but does not prevent a fall in Crs. NO inhalation may help prevent long-lasting pulmonary failure. 相似文献
94.
Eric J. Murphy Ralph Stephens Marianne Jurkowitz-Alexander Lloyd A. Horrocks 《Lipids》1993,28(6):565-568
A simple, quantitative method for determining the plasmalogen content of small samples is reported here. The method uses the
different susceptibility to acid-catalyzed hydrolysis of the alkyl, alkenyl and acyl linkages to separate the plasmalogen
subclass from the other two non-labile subclasses. Hydrolysis of plasmenylethanolamine and plasmenylcholine was complete after
4 and 1 min of acid treatment, respectively. The acid-catalyzed hydrolysis did not alter the phospholipid fatty acid composition,
making this method useful for fatty acid compositional analysis of the plasmalogen subclass. High-performance liquid chromatography
was used for separations, and phospholipids were quantitated by assay of lipid phosphorus or by direct quantitation of peak
area. Using this method, small amounts (10 nmol) of ethanolamine glycerophospholipid and choline glycerophospholipid are subjected
to acid-catalyzed hydrolysis and subsequent separation of the resulting lysocompounds obtained from plasmalogens from the
more acid-stable alkylacyl and diacyl glycerophospholipid fractions. Our values for plasmalogens from commercial preparations
of choline and ethanolamine glycerophospholipids agree with literature values. The usefulness of the method is demonstrated
for small glycerophospholipid samples that are equivalent to samples from cultured neural cells. 相似文献
95.
K. J. Murchie K. P. E. Hair C. E. Pullen T. D. Redpath H. R. Stephens S. J. Cooke 《河流研究与利用》2008,24(2):197-217
Globally, rivers are increasingly being subjected to various levels of physical alteration and river regulation to provide humans with services such as hydropower, freshwater, flood control, irrigation and recreation. Although river regulation plays an important role in modern society, there are potential consequences which may negatively affect fish and fish habitat. While much effort has been expended examining the response of fish to fluctuating flow regimes in different systems, there has been little in the way of a comprehensive synthesis. In an effort to better understand the effects of river regulation on fish and fish habitat, we conducted a systematic review of available literature with three goals: (1) summarize the various research methodologies used by regulated river researchers, (2) summarize the effects found on fish and fish habitat and (3) identify opportunities for future research. The results of the synthesis indicate that a wide variety of methodologies are being employed to study regulated river science, yet there is a gap in incorporating methodologies that examine effects on fish at a cellular level or those techniques that are interdisciplinary (e.g. behaviour and physiology). There is a clear consensus that modified flow regimes in regulated rivers are affecting fish and fish habitat, but the severity and direction of the response varies widely. Future study designs should include methods that target all biological levels of fish response, and in which detailed statistical analyses can be performed. There is also a need for more rigorous study designs including the use of appropriate controls and replicates. Data on physical variables that co‐vary with flow should be collected and examined to add explanatory power to the results. Increased multi‐stakeholder collaborations provide the greatest promise of balancing ecological concerns with economic needs. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
96.
While serving as APA president, I very much enjoyed the opportunity to learn more about the variety and complexity of psychology as a discipline and practice. In particular, I became interested in various emerging directions and future possibilities. This article, based on my 2007 presidential address at the APA annual convention, summarizes my observations and reflections and attempts to present a reasonably compelling portrait of psychology's future and that of the APA. I hope that this overview will stimulate others to gaze into their own crystal balls and use their insights to construct an even more lively and vibrant psychology. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
97.
Stephens Mary Ann Parris; Norris Virginia K.; Kinney Jennifer M.; Ritchie Susan W.; Grotz Robert C. 《Canadian Metallurgical Quarterly》1988,3(2):208
We examined ways in which caregivers cope with stressful caregiving situations and the relations between coping strategies and caregivers' psychosocial well-being. Respondents were 58 family caregivers to patients discharged from a rehabilitation hospital. Caregivers identified a recent stressful event in caregiving and indicated strategies used to cope with this event. After controlling for patients' impairment level, analyses indicated that caregivers engaging in more escape–avoidance coping reported greater depression and more conflict in their personal relationships. Those using more positive reappraisal demonstrated greater positive affect. Younger caregivers, many of whom were women, used more avoidance strategies. Results have implications for therapeutic interventions with family caregivers. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
98.
99.
100.