全文获取类型
收费全文 | 433篇 |
免费 | 13篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 5篇 |
综合类 | 9篇 |
化学工业 | 86篇 |
金属工艺 | 3篇 |
机械仪表 | 8篇 |
建筑科学 | 12篇 |
矿业工程 | 8篇 |
能源动力 | 13篇 |
轻工业 | 28篇 |
水利工程 | 4篇 |
石油天然气 | 1篇 |
无线电 | 27篇 |
一般工业技术 | 45篇 |
冶金工业 | 110篇 |
原子能技术 | 2篇 |
自动化技术 | 90篇 |
出版年
2023年 | 3篇 |
2022年 | 7篇 |
2021年 | 11篇 |
2020年 | 4篇 |
2019年 | 5篇 |
2018年 | 2篇 |
2017年 | 5篇 |
2016年 | 11篇 |
2015年 | 4篇 |
2014年 | 11篇 |
2013年 | 19篇 |
2012年 | 20篇 |
2011年 | 27篇 |
2010年 | 21篇 |
2009年 | 12篇 |
2008年 | 14篇 |
2007年 | 21篇 |
2006年 | 19篇 |
2005年 | 10篇 |
2004年 | 9篇 |
2003年 | 11篇 |
2002年 | 12篇 |
2001年 | 8篇 |
2000年 | 5篇 |
1999年 | 11篇 |
1998年 | 23篇 |
1997年 | 20篇 |
1996年 | 15篇 |
1995年 | 6篇 |
1994年 | 9篇 |
1993年 | 9篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 6篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1986年 | 3篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1977年 | 3篇 |
1976年 | 5篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1966年 | 1篇 |
1964年 | 2篇 |
1957年 | 2篇 |
1947年 | 3篇 |
排序方式: 共有451条查询结果,搜索用时 349 毫秒
31.
32.
Thallium (TI) is a metal of great toxicological concern and its prevalence in the natural environment has steadily increased as a result of manufacturing and combustion practices. Due to its low natural abundance and increasing demand, TI is the fourth most expensive metal, thus, recovery and reuse could be a profitable endeavor. The hyperaccumulator Iberis intermedia was examined via in vivo micro-X-ray absorption near edge (micro-XANES) and micro-X-ray fluorescence (micro-XRF) spectroscopies to determine the speciation and distribution of TI within leaves of the plant. I. intermedia plants were cultivated under controlled conditions in 0, 10, and 20 mg TI kg(-1) soil leading to a shoot concentration of up to 13 430 mg TI kg(-1) dry weight plant mass during 10 weeks of growth. Live plant leaves were examined by micro-XANES and micro-XRF which determined aqueous TI(I) to be the model species distributed primarily throughout the vascular network. A direct relationship of vein size to TI concentration was observed. The high uptake of TI and high potential biomass of I. intermedia, combined with knowledge of TI speciation and compartmentation within the plant, are discussed in terms of accumulation/tolerance mechanisms, consequences for potential food chain contamination, and phytomining strategies to reclaim TI-contaminated soils, sediments, and waters. 相似文献
33.
We developed a new algorithm that estimates locations and sizes of anomalies in electrically conducting medium based on electrical impedance tomography (EIT) technique. When only the boundary current and voltage measurements are available, it is not practically feasible to reconstruct accurate high-resolution cross-sectional conductivity or resistivity images of a subject. In this paper, we focus our attention on the estimation of locations and sizes of anomalies with different conductivity values compared with the background tissues. We showed the performance of the algorithm from experimental results using a 32-channel EIT system and saline phantom. With about 1.73% measurement error in boundary current-voltage data, we found that the minimal size (area) of the detectable anomaly is about 0.72% of the size (area) of the phantom. Potential applications include the monitoring of impedance related physiological events and bubble detection in two-phase flow. Since this new algorithm requires neither any forward solver nor time-consuming minimization process, it is fast enough for various real-time applications in medicine and nondestructive testing. 相似文献
34.
Van Houte H De Hoffmann E Van Veldhoven PP Mannaerts GP Carchon H Baes MI Declercq PE 《Lipids》2001,36(4):367-372
The goal of this study was to clarify the mechanism responsible for the catabolism of α-tocopherol. The vitamin, bound to
albumin, was incubated with rat liver microsomes and appeared to be broken down. Optimal production of the metabolite was
obtained when 1 mg of microsomal protein was incubated with 36 μM of α-tocopherol in the presence of 1.5 mM of NADPH. Chromatographic
and mass spectrometric analyses of the metabolite led to the conclusion that it consists of an ω-acid with an opened chroman
ring, although we could not perform nuclear magnetic resonance analysis to confirm this. Our data show that α-tocopherol is
ω-oxidized to a carboxylic acid and that this process can occur in rat liver microsomes in the presence of NADPH and O2. The oxidation to the quinone structure appears to be a subsequent event that may be artifactual and/or catalyzed by a microsomal
enzyme(s). 相似文献
35.
Effects of 1,4-Benzoxazin-3-One Derivatives from Maize on Survival and Fecundity of Metopolophium dirhodum (Walker) on Artificial Diet 总被引:3,自引:0,他引:3
Effects of 2--D-glucopyranosyloxy-4-hydroxy-7-methoxy-1,4benzoxazin-3-one (DIMBOA-Glc) and DIMBOA-Glc N-O-methylated (HDMBOA-Glc), two compounds present in high concentration in maize, were tested on the aphid Metopolophium dirhodum reared on artificial diet. HDMBOA-Glc and DIMBOA-Glc decrease survival of adults with an LD50 of 1 mM and 5.6 mM, respectively, after 72 hr of feeding. These compounds also decrease the fecundity of the aphids at concentrations of 2 mM and 1 mM, respectively. At concentrations of 2 mM HDMBOA-Glc and 8 mM DIMBOA-Glc in the diet, the average lifetime fecundity of 10 females is near zero. Offspring mortality on diet with 2 mM DIMBOA-Glc is significantly higher than with the control diet. In contrast, HDMBOA-Glc has no effect on the survival of offspring. The possibility that these compounds protect Poaceae against aphids is discussed. 相似文献
36.
Edmond P. Saliklis Michael Bauer David P. Billington 《Canadian Metallurgical Quarterly》2008,14(1):25-29
Aesthetic and ethical issues of building design are presented here to encourage meaningful discussion among today’s architectural engineering students and practitioners. The evaluative aesthetic ideas of scale, simplicity, and surprise are applied to two important structures designed by Fazlur R. Khan. Khan’s profound understanding of load flow in his buildings influenced his aesthetic ideas. Furthermore, his aesthetic ideas were intimately intertwined with his ethical ideas about structural logic and the role of structure in architecture. We explore these ideas and present new insights as well. Our goal is to encourage a public discourse within our profession on the topic of evaluating structural form. 相似文献
37.
John K. G. Kramer Frank D. Sauer Edward R. Farnworth Dan Stevenson Gail A. Rock 《Lipids》1998,33(1):1-10
Canola oil is not presently permitted in infant formulations in the United States because of lack of information concenring
the effects of feeding canola oil to the newborn. We have previously reported a transient decrease in platelet counts and
an increase in platelet size in newborn piglets fed canola oil for 4 wk, and have confirmed this in the present study. In
canola oil-fed piglets, changes in platelet size and number were overcome by adding either long-chain saturated fatty acids
from cocoa butter (16:0 and 18:0), or shorter-chain saturates from coconut oil (12:0 and 14:0). Feeding a high erucic acid
rapeseed (HEAR) oil, with 20% 22:1n−9, led to an even greater platelet reduction and increased platelet size throughout the
4-wk trial. Bleeding times were longer in piglets fed canola oil or HEAR oil compared to sow-reared and soybean oil-fed piglets.
There were no other diet-related changes. Diet-induced platelet changes were not related to platelet lipid class composition,
but there were fatty acid changes. The incorporation of 22:1n−9 into platelet phospholipids of piglets fed canola oil was
low (0.2–1.2%), and even for the HEAR oil group ranged from only 0.2% in phosphatidylinositol to 2.4% in phosphatidylserine.
A much greater change was observed in the concentration of 24:1n−9 and in the 24:1n−9/24:0 ratio in platelet sphingomyelin
(SM). The 24:1n−9 increased to 49% in the HEAR oil group compared to about 12% in animals fed the control diets (sow-reared
piglets and soybean oil-fed group), while the 24:1n−9/24:0 ratio increased from about 1 to 12. Even feeding canola oil, prepared
to contain 2% 22:1n−9, led to a marked increase in 24:1n−9 to 29% and had a 24:1n−9/24:0 ratio of 5. The canola oil/cocoa
butter group, which also contained 2% 22:1n−9, showed a lower level of 24:1n−9 (20%) and the 24:1n−9/24:0 ratio (3) compared
to the canola oil group. The results suggest that the diet-related platelet changes in newborn piglets may be related to an
increase in 24:1n−9 in platelet SM, resulting from chain elongation of 22:1n−9. The inclusion of canola oil as the sole source
of fat in the milk-replacer diets of newborn piglets resulted in significant platelet and lipid changes. 相似文献
38.
Meghan Allen Rock Leung Joanna McGrenere Barbara Purves 《Universal Access in the Information Society》2008,7(3):145-154
Teams engaging in assistive technology research should include expertise in the domain of disability itself, in addition to
other areas of expertise that are more typical in human–computer interaction (HCI) research, such as computer science and
psychology. However, unexpected problems can arise when HCI researchers do not adequately plan the involvement of domain experts
in a research project. Although many research teams have included domain experts when designing assistive technologies, there
has been little work published on how to best involve these experts in the research process. This paper is a first step towards
filling that void. Based on the authors’ own experiences involving domain experts in research, as well as those documented
in the literature, five types of domain experts and three broad roles that domain experts can play are identified, and five
guidelines for their involvement are presented. This analysis will be useful to anyone in the assistive technology and universal
accessibility communities, especially those who are in the early stages of conducting research in this area. It is intended
to lay the foundation of best practices for involving domain experts in assistive technology research. 相似文献
39.
40.
A new high voltage field-effect transistor is described. It features an array of uncontacted gate elements between the main gate and the drain which float so as to inhibit avalanche breakdown. Good agreement is obtained between model predictions and the performance of experimental devices fabricated in Si-TaSi/sub 2/ semiconductor-metal eutectic material. Transistors are demonstrated which hold off up to 1000 V, compared with the avalanche breakdown potential of 300 V or less expected for conventional devices made with similarly doped silicon.<> 相似文献