全文获取类型
收费全文 | 4788篇 |
免费 | 116篇 |
专业分类
电工技术 | 48篇 |
综合类 | 2篇 |
化学工业 | 633篇 |
金属工艺 | 34篇 |
机械仪表 | 53篇 |
建筑科学 | 203篇 |
矿业工程 | 3篇 |
能源动力 | 69篇 |
轻工业 | 419篇 |
水利工程 | 66篇 |
石油天然气 | 8篇 |
武器工业 | 1篇 |
无线电 | 323篇 |
一般工业技术 | 579篇 |
冶金工业 | 1978篇 |
原子能技术 | 15篇 |
自动化技术 | 470篇 |
出版年
2023年 | 31篇 |
2022年 | 70篇 |
2021年 | 77篇 |
2020年 | 61篇 |
2019年 | 57篇 |
2018年 | 56篇 |
2017年 | 48篇 |
2016年 | 86篇 |
2015年 | 49篇 |
2014年 | 96篇 |
2013年 | 189篇 |
2012年 | 161篇 |
2011年 | 244篇 |
2010年 | 191篇 |
2009年 | 193篇 |
2008年 | 221篇 |
2007年 | 232篇 |
2006年 | 194篇 |
2005年 | 147篇 |
2004年 | 129篇 |
2003年 | 122篇 |
2002年 | 127篇 |
2001年 | 77篇 |
2000年 | 84篇 |
1999年 | 99篇 |
1998年 | 341篇 |
1997年 | 200篇 |
1996年 | 125篇 |
1995年 | 115篇 |
1994年 | 98篇 |
1993年 | 102篇 |
1992年 | 63篇 |
1991年 | 33篇 |
1990年 | 56篇 |
1989年 | 50篇 |
1988年 | 45篇 |
1987年 | 47篇 |
1986年 | 46篇 |
1985年 | 61篇 |
1984年 | 40篇 |
1983年 | 29篇 |
1982年 | 31篇 |
1981年 | 43篇 |
1980年 | 26篇 |
1979年 | 32篇 |
1978年 | 25篇 |
1977年 | 31篇 |
1976年 | 74篇 |
1975年 | 24篇 |
1974年 | 18篇 |
排序方式: 共有4904条查询结果,搜索用时 0 毫秒
51.
Matthew L. Bolton Ellen J. Bass Radu I. Siminiceanu 《International journal of human-computer studies》2012,70(11):888-906
Breakdowns in complex systems often occur as a result of system elements interacting in unanticipated ways. In systems with human operators, human–automation interaction associated with both normative and erroneous human behavior can contribute to such failures. Model-driven design and analysis techniques provide engineers with formal methods tools and techniques capable of evaluating how human behavior can contribute to system failures. This paper presents a novel method for automatically generating task analytic models encompassing both normative and erroneous human behavior from normative task models. The generated erroneous behavior is capable of replicating Hollnagel's zero-order phenotypes of erroneous action for omissions, jumps, repetitions, and intrusions. Multiple phenotypical acts can occur in sequence, thus allowing for the generation of higher order phenotypes. The task behavior model pattern capable of generating erroneous behavior can be integrated into a formal system model so that system safety properties can be formally verified with a model checker. This allows analysts to prove that a human–automation interactive system (as represented by the model) will or will not satisfy safety properties with both normative and generated erroneous human behavior. We present benchmarks related to the size of the statespace and verification time of models to show how the erroneous human behavior generation process scales. We demonstrate the method with a case study: the operation of a radiation therapy machine. A potential problem resulting from a generated erroneous human action is discovered. A design intervention is presented which prevents this problem from occurring. We discuss how our method could be used to evaluate larger applications and recommend future paths of development. 相似文献
52.
Interactions of metals and protons with algae 总被引:2,自引:0,他引:2
Crist RH Oberholser K Schwartz D Marzoff J Ryder D Crist DR 《Environmental science & technology》1988,22(7):755-760
53.
Lillian F. Feldmann Schwartz 《The Visual computer》1988,4(1):40-48
A recent computer-aided study identified the model immortalized in Leonardo da Vinci's celebratedMona Lisa to be none other than the artist himself. A follow-up investigation empolying similar techniques identifies the subject of asecond HiddenMona Lisa by the same artist. Analysis of photographic and x-ray images indicates that Leonardo first created a sketch of Isabella, Duchess of Aragon, which he later painted over with theMona Lisa, using himself as the model. 相似文献
54.
The DSR (dynamic spatial reconstructor), a multiple X-ray source scanner that generates stop action three-dimensional (3-D) images of a cylindrical volume, was used for quantitative imaging of left ventricular 3-D wall geometry and function in experimentally induced canine left ventricular myocardial infarction. Impaired regional myocardial function was induced by myocardial ischemia or infarction in four mongrel dogs by closed-chest occlusion of the proximal left anterior descending (LAD) coronary artery. At intervals of 6-14 weeks post occlusion, the dogs were scanned with the DSR during biatrial contrast injection. The 3-D shape, extent, and function of hypokinetic myocardium was measured from the DSR images utilizing measurement of the rate of local systolic wall thickening to detect regions of normal, ischemic, or scarred myocardium. The results were compared to scar size and anatomic distribution measured at postmortem examination. The anatomic extent and relationship of hypocontractile to normally contracting muscle was visualized by computer generated, pseudo 3-D shaded surface displays of the left ventricular chamber and by topographic projections of regional wall thickening rates onto a map of the left ventricular endocardial surface. The location of myocardial infarction and the surrounding zone of impaired function is clearly defined by this 3-D CT scanning procedure. The display method presented here provides both localization and quantification of the volume of ischemic and infarcted myocardium. 相似文献
55.
Amy?Richards Chakra?WijesunderaEmail author Phil?Salisbury 《Journal of the American Oil Chemists' Society》2005,82(12):869-874
Lipid oxidation is a major factor affecting flavor quality and shelf life of vegetable oils. Oxidative stability is therefore
an important criterion by which oils are judged for usefulness in various food applications. In this study a method based
on headspace analysis was developed to evaluate relative oxidative stability of canola oils. The method does not require the
use of chemicals, involves minimal sample preparation, and can be performed on a relatively small sample size in comparison
with traditional wet chemical methods. Canola oils freshly extracted in the laboratory from different seed samples were subjected
to accelerated oxidation and analyzed for PV by standard methods and headspace volatiles by solid phase microextraction/GC-MS.
Forward stepwise regression analysis of the data revealed a relationship between PV and headspace concentration of the volatile
lipid oxidation products hexanal and trans,trans-2,4-heptadienal. The PV calculated using this formula correlated (R
2=0.73) with those measured by conventional methods.
Presented in part at the 96th Annual Meeting of the AOCS, 1–4 May 2005, Salt Lake City, UT. 相似文献
56.
57.
Effects of hydrodynamic conditions, current density and solution temperature on the d.c. electrodeposition of Fe–Ni–Co alloys have been investigated with stationary planar and rotating cylindrical electrodes. The deposition rate of Fe showed mass transfer effects at cathodic potentials –1.35 V/sce. Deposition of Ni appeared to be kinetically controlled; deposition of Co appeared to be under kinetic control at potentials –1.35 V/sce but under mixed control at –1.65 V. Current efficiency of the codeposition process increased with increasing current density and decreased with increasing rotation rate. Higher solution temperatures and rotation rates extended the applied current density range where smooth, adherent, and metallic-looking deposits could be obtained. An increase in solution temperatures also decreased anomalous codeposition of Fe–Ni–Co. Calculations based on the Hessami-Tobias model provide qualitative agreement with dependence of experimental electrodeposition on applied current density, hydrodynamics and temperature. 相似文献
58.
Preparation of glycol derivatives of partially hydrogenated soybean oil fatty acids and their potential as lubricants 总被引:1,自引:0,他引:1
Hemendra N. Basu Ellen M. Robley Max E. Norris 《Journal of the American Oil Chemists' Society》1994,71(11):1227-1230
Glycol diesters and mixtures of mono- and diesters have been prepared from methyl esters of partially hydrogenated soybean
oil fatty acids and diethylene, dipropylene, neopentyl and triethylene glycols. The catalyst used in these reactions was a
mixture of calcium acetate/barium acetate (3∶1, w/w). The reactions were carried out under nitrogen with 0.5% catalyst at
temperatures in the range of 190–275°C. Borated esters of mixed mono- and diesters were prepared with 0.33 equivalent of boric
acid per 1.0 equivalent hydroxyl group on the ester. Refractive indices, viscosities, and flash and fire points were determined
for diesters, mixed mono- and diesters, and mixed diesters and borated esters. The viscosities, flash points and fire points
indicate that these esters can be used as a component of lubricating oils. Wear-prevention characteristics of mixed diesters
and borated esters indicated that they can be used as antifriction additives in lubricating oils.
Lecture presented at the joint meeting of the International Society for Fat Research and the American Oil Chemists' Society
in Toronto, May 10, 1992. 相似文献
59.
Dietary stearic acid and risk of cardiovascular disease: Intake,sources, digestion,and absorption 总被引:1,自引:2,他引:1
Individual FA have diverse biological effects, some of which affect the risk of cardiovascular disease (CVD). In the context
of food-based dietary guidance designed to reduce CVD risk, fat and FA recommendations focus on reducing saturated FA (SFA)
and trans FA (TFA), and ensuring an adequate intake of unsaturated FA. Because stearic acid shares many physical properties with the
other long-chain SFA but has different physiological effects, it is being evaluated as a substitute for TFA in food manufacturing.
For stearic acid to become the primary replacement for TFA, it is essential that its physical properties and biological effects
be well understood. 相似文献
60.
The effects of linoleic, linolenic and columbinic acids fed as 4% of a high carbohydrate (50% glucose) diet on the activities
and the amounts of several enzymes associated with fatty acid synthesis in livers and mammary glands of lactating mice were
compared with those for stearic and oleic acids. Fatty acid synthesis, measured in vivo, was significantly lower in livers
of mice ingesting all 3 polyunsaturated fatty acids (PUFA), whereas in mammary glands synthesis was lower only in mice receiving
columbinic acid. The activities of fatty acid synthetase (FAS) and acetyl CoA carboxylase were significantly reduced in liver
by all 3 PUFA, as were activities of glucose-6-phosphate dehydrogenase, malic enzyme (ME) and citrate cleavage enzyme (CCE),
also associated with lipogenesis. In mammary gland, on the other hand, the activities of these enzymes were unaffected by
dietary PUFA. The tissue contents of FAS, ME and CCE, measured by rocket immunoelectrophoresis, were found to be significantly
reduced in liver by linoleate, linolenate and columbinate but were not significantly altered in mammary gland. The decrease
in hepatic lipogenesis observed was principally due to a decrease in the amounts of these enzymes induced by the dietary PUFA
but the inhibition in mammary gland caused by columbinate could not be accounted for by a reduction in enzyme contents and
therefore may be due to allosteric effects which occur when fatty acid synthesis is measured with3H2O. The fatty acid composition in liver and mammary gland of dams and in liver and kidney of pups completely reflected dietary
fatty acids. Columbinate made up ca. 20% of the total fatty acids in both tissues of the columbinic acid-fed mice and ca.
15% in the pup tissues. This suggests that columbinate is incorporated into milk lipids of dams and is easily absorbed by
pups. The elevated ratios of 16/16∶1 and 18/18∶1 in liver and mammary gland of dams and liver and kidney of the pups from
dams fed linoleate, linolenate and columbinate suggest that each of these polyunsaturated fatty acids in the diet can inhibit
the activity of Δ9 desaturase. 相似文献