全文获取类型
收费全文 | 1559篇 |
免费 | 52篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 13篇 |
综合类 | 1篇 |
化学工业 | 327篇 |
金属工艺 | 21篇 |
机械仪表 | 18篇 |
建筑科学 | 89篇 |
矿业工程 | 3篇 |
能源动力 | 29篇 |
轻工业 | 197篇 |
水利工程 | 9篇 |
石油天然气 | 1篇 |
无线电 | 134篇 |
一般工业技术 | 240篇 |
冶金工业 | 364篇 |
原子能技术 | 18篇 |
自动化技术 | 148篇 |
出版年
2023年 | 24篇 |
2022年 | 33篇 |
2021年 | 54篇 |
2020年 | 26篇 |
2019年 | 34篇 |
2018年 | 34篇 |
2017年 | 27篇 |
2016年 | 33篇 |
2015年 | 43篇 |
2014年 | 51篇 |
2013年 | 71篇 |
2012年 | 73篇 |
2011年 | 90篇 |
2010年 | 70篇 |
2009年 | 48篇 |
2008年 | 82篇 |
2007年 | 65篇 |
2006年 | 63篇 |
2005年 | 39篇 |
2004年 | 24篇 |
2003年 | 33篇 |
2002年 | 36篇 |
2001年 | 19篇 |
2000年 | 21篇 |
1999年 | 28篇 |
1998年 | 88篇 |
1997年 | 58篇 |
1996年 | 50篇 |
1995年 | 25篇 |
1994年 | 24篇 |
1993年 | 21篇 |
1992年 | 15篇 |
1991年 | 17篇 |
1990年 | 11篇 |
1989年 | 17篇 |
1988年 | 11篇 |
1987年 | 7篇 |
1986年 | 10篇 |
1985年 | 5篇 |
1984年 | 8篇 |
1983年 | 7篇 |
1982年 | 10篇 |
1980年 | 8篇 |
1978年 | 10篇 |
1977年 | 6篇 |
1976年 | 13篇 |
1974年 | 9篇 |
1972年 | 7篇 |
1969年 | 4篇 |
1909年 | 4篇 |
排序方式: 共有1612条查询结果,搜索用时 15 毫秒
121.
Norman MUIRHEAD Paul A. KEOWN David N. CHURCHILL Melanie POULIN‐COSTELLO Sandeep GANTOTTI Lei LEI Matthew GITLIN Tracy J. MAYNE 《Hemodialysis international. International Symposium on Home Hemodialysis》2011,15(1):87-94
The risks/benefits of anemia treatment in dialysis patients have been redefined in the US Epoetin α label. This analysis was carried out to determine if increasing hemoglobin (Hb) levels improve exercise tolerance and physical function in anemic dialysis patients. This is a new analysis of the Canadian Erythropoietin Study Group trial, a double‐blind, randomized, placebo‐controlled trial in dialysis patients. Subjects were 18 to 75 years old, on hemodialysis for >3 months, and had a baseline Hb <9.0 g/dL. Patients with a history of diabetes mellitus, ischemic heart disease, or severe/uncontrolled hypertension were excluded. Patients were randomized to receive Epoetin α to a target Hb of 9.5 to 11.0 g/dL (n=40) or a target of 11.5 to 13.0 g/dL (n=38), or receive placebo (n=40). Results from patients in the Epoetin‐α–treated arms were combined for this analysis. Hb level, exercise tolerance (Treadmill Stress Test and 6‐Minute Walk Test) and patient‐reported physical function measures (Physical Summary domain from the Kidney Disease Questionnaire, and 4 domains from the Sickness Impact Profile) were reported at baseline and months 2, 4, and 6. Differences in measures were statistically significant for exercise tolerance (Treadmill Stress, P=0.0001) and patient‐reported physical function (Kidney Disease Questionnaire Physical, P=0.0001; Sickness Impact Profile Physical, P=0.0015) across all time points for Epoetin‐α–treated patients compared with placebo. Improvements were seen at 2 months and were maintained through months 4 and 6. Dialysis patients receiving Epoetin α showed improved exercise tolerance and physical function. These findings should be considered as physicians weigh the risks and benefits of treatment. 相似文献
122.
Melanie Po-Leen Ooi Hong Kuan Sok Ye Chow Kuang Serge Demidenko Chris Chan 《Engineering Applications of Artificial Intelligence》2013,26(3):1029-1043
The International Technology Roadmap for Semiconductors (ITRS) identifies production test data as an essential element in improving design and technology in the manufacturing process feedback loop. One of the observations made from the high-volume production test data is that dies that fail due to a systematic failure have a tendency to form certain unique patterns that manifest as defect clusters at the wafer level. Identifying and categorising such clusters is a crucial step towards manufacturing yield improvement and implementation of real-time statistical process control. Addressing the semiconductor industry’s needs, this research proposes an automatic defect cluster recognition system for semiconductor wafers that achieves up to 95% accuracy (depending on the product type). 相似文献
123.
Frederick Steiner Laurel McSherry Dean Brennan Mark Soden Joe Yarchin Douglas Green 《Journal of the American Planning Association. American Planning Association》2013,79(2):207-222
As part of ongoing cooperation between the City of Phoenix and Arizona State University, a charrette was organized. Planners, landscape architects, environmental scientists, and architects explored concepts for development within a 110-square-mile (285-km2) portion of Phoenix. The charrette was the summation of over a year of environment studies of the planning area. This part of northern Phoenix occupies a largely undeveloped upper Sonoran desert landscape experiencing intense development pressure. Four charrette teams addressed desert preservation, rural desert development, suburban desert development, and growth corridors. This article focuses on some of the strategies proposed by the suburban desert development team. One of these called for an alternative pattern of development aligned with natural drainage corridors. Several concepts from the charrette and findings from the environmental research were adopted by the City in the revised general plan for the area. 相似文献
124.
Thomas Steiner 《Crystallography Reviews》2013,19(2-3):177-228
An overview is given on C–H···O hydrogen bonding in the solid state. Following a short survey of the early literature, the general properties of C–H···O bonding are discussed. The structural characteristics and some physical consequences of C–H···O bonds are described. A number of special systems are discussed in greater detail; these include water acceptors, inclusion complexes, and some biological structures. 相似文献
125.
We study a single-machine scheduling problem in a flexible framework where both job processing times and due dates are decision
variables to be determined by the scheduler. The model can also be applied for quoting delivery times when some parts of the
jobs may be outsourced. We analyze the problem for two due date assignment methods and a convex resource consumption function.
For each due date assignment method, we provide a bicriteria analysis where the first criterion is to minimize the total weighted
number of tardy jobs plus due date assignment cost, and the second criterion is to minimize total weighted resource consumption.
We consider four different models for treating the two criteria. Although the problem of minimizing a single integrated objective
function can be solved in polynomial time, we prove that the three bicriteria models are NP\mathcal{NP}-hard for both due date assignment methods. We also present special cases, which frequently occur in practice, and in which
all four models are polynomially solvable. 相似文献
126.
Sonja Berg Melanie J. Leng Christopher P. Kendrick Holger Cremer Bernd Wagner 《SILICON》2013,5(1):19-34
Organic carbon occluded in diatom silica is assumed to be protected from degradation in the sediment. δ13C from diatom carbon (δ13C(diatom)) therefore potentially provides a signal of conditions during diatom growth. However, there have been few studies based on δ13C(diatom). Numerous variables can influence δ13C of organic matter in the marine environment (e.g., salinity, light, nutrient and CO2 availability). Here we compare δ13C(diatom) and δ13C(TOC) from three sediment records from individual marine inlets (Rauer Group, East Antarctica) to (i) investigate deviations between δ13C(diatom) and δ13C(TOC), to (ii) identify biological and environmental controls on δ13C(diatom) and δ13C(TOC), and to (iii) discuss δ13C(diatom) as a proxy for environmental and climate reconstructions. The records show individual δ13C(diatom) and δ13C(TOC) characteristics, which indicates that δ13C is not primarily controlled by regional climate or atmospheric CO2 concentration. Since the inlets vary in water depths offsets in δ13C are probably related to differences in water column stratification and mixing, which influences redistribution of nutrients and carbon within each inlet. In our dataset changes in δ13C(diatom) and δ13C(TOC) could not unequivocally be ascribed to changes in diatom species composition, either because the variation in δ13C(diatom) between the observed species is too small or because other environmental controls are more dominant. Records from the Southern Ocean show depleted δ13C(diatom) values (1–4 ‰) during glacial times compared to the Holocene. Although climate variability throughout the Holocene is low compared to glacial/interglacial variability, we find variability in δ13C(diatom), which is in the same order of magnitude. δ13C of organic matter produced in the costal marine environment seems to be much more sensitive to environmental changes than open ocean sites and δ13C is of strongly local nature. 相似文献
127.
128.
We tested the hypothesis that poor performance on the Piagetian invisible displacement task is related to increased memory requirements. Rhesus monkeys and orangutans received 3 types of problems (invisible, visible, and no transfer problems) each containing a number of steps equivalent to that of standard invisible displacements. If failure to solve invisible displacements was due to increased memory requirements, then the primates should perform at chance level on all 3 problems. However, rhesus monkeys solved visible and no transfer problems, but not invisible transfer problems. Half of the orangutans solved all 3 transfer problems, although their performance on invisible transfer problems was lower than that on the other problems. A subsequent cuing phase led to improved performance, and a few monkeys solved invisible transfer problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
129.
The migration of acetaldehyde from polyethylene terephthalate bottles for fresh beverages containing carbonic acid 总被引:1,自引:0,他引:1
S Eberhartinger I Steiner J Washüttl G Kroyer 《Zeitschrift für Lebensmittel-Untersuchung und -Forschung》1990,191(4-5):286-289
The migration of acetaldehyde from polyethylene terephthalate (PET) under various conditions was analysed by headspace gas chromatography and flame ionisation detection. The residual amounts of new PET bottles were about 6.3 mg/kg with a migration value of 200 micrograms/l. On studying the migration at different temperatures and times, behaviour curves characteristic of packing materials made from plastics are obtained. The amount of acetaldehyde diffusing from PET at a temperature of 40 degrees C reached a constant level after 4 days which was about 10% of the residual value of acetaldehyde. On increasing the temperature by 20 degrees C, this level was raised up to 50%. The results of the analysis of acetaldehyde in soft drinks containing carbonic acid show that the migration in fact is not sufficiently high to influence the taste of these soft drinks. A negative effect on the taste may be recognized with mineral waters and soda when they are exposed to higher temperatures (e.g. 40 degrees C or more) over a longer period of time. 相似文献
130.
Understanding a link between sexual harassment and eating disorder symptoms: A mediational analysis.
Using data from 3 samples of working women and men, the present study examines the association between sexual harassment and eating disorder symptoms by studying the processes that may underlie this relationship. The results of structural equation modeling suggest a link between sexual harassment and eating disorder symptoms among women and indicate that this relationship is mediated by psychological distress, self-esteem, and self-blame. Further, sexual harassment was found to predict eating disorder symptoms among women even when experiences of sexual assault were included in the model. No relationship was found between sexual harassment and eating disorder symptoms among men. The theoretical and clinical implications of these results are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献