全文获取类型
收费全文 | 458篇 |
免费 | 3篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 57篇 |
金属工艺 | 2篇 |
机械仪表 | 8篇 |
建筑科学 | 19篇 |
能源动力 | 8篇 |
轻工业 | 23篇 |
水利工程 | 1篇 |
石油天然气 | 2篇 |
无线电 | 26篇 |
一般工业技术 | 62篇 |
冶金工业 | 188篇 |
原子能技术 | 11篇 |
自动化技术 | 51篇 |
出版年
2021年 | 6篇 |
2019年 | 2篇 |
2018年 | 1篇 |
2017年 | 2篇 |
2016年 | 2篇 |
2015年 | 4篇 |
2014年 | 8篇 |
2013年 | 12篇 |
2012年 | 7篇 |
2011年 | 19篇 |
2010年 | 7篇 |
2009年 | 18篇 |
2008年 | 13篇 |
2007年 | 25篇 |
2006年 | 17篇 |
2005年 | 9篇 |
2004年 | 9篇 |
2003年 | 8篇 |
2002年 | 8篇 |
2001年 | 8篇 |
2000年 | 10篇 |
1999年 | 10篇 |
1998年 | 65篇 |
1997年 | 36篇 |
1996年 | 33篇 |
1995年 | 19篇 |
1994年 | 20篇 |
1993年 | 13篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 7篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 9篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1972年 | 1篇 |
1968年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有461条查询结果,搜索用时 15 毫秒
31.
Jean-Savin Heron Germain M. Souche Florian R. Ong Philippe Gandit Thierry Fournier Olivier Bourgeois 《Journal of Low Temperature Physics》2009,154(5-6):150-160
We report on the dynamic measurements of thermal properties of nanosystems at very low temperatures. These techniques are based on the modulation of the temperature and hence leads to highly sensitive measurements. We will discuss the intrinsic limitations of these methods when the thermal properties of nano-objects are studied at very low temperatures, much below 1 K. Firstly, we will present thermal conductance measurements using the 3ω method. This technique is limited at low temperatures due to the significant increase of the mean free path. Secondly, heat capacity measurements using ac calorimetry are outlined, and again restrictions occur due to the continuous temperature gradient inherent to that technique. Propositions are made in order to overcome these limitations. 相似文献
32.
33.
The beta-lactamase genes of Klebsiella oxytoca were previously divided into two main groups: bla(OXY-1) and bla(OXY-2). The two beta-lactamase groups were each represented by beta-lactamases with four different pIs. In each group, one form of beta-lactamase is more frequent than the others combined. The beta-lactamase gene of each representative beta-lactamase with a different pI that was not yet sequenced (pIs 5.7, 6.8 [OXY-2], 7.1, 8.2, and 8.8 [OXY-1]) was cloned and sequenced. The susceptibility patterns as well as relative rates and kinetic parameters for beta-lactam hydrolysis revealed that OXY-2 enzymes hydrolyzed several of the beta-lactams that were examined (carbenicillin, cephalothin, cefamandole, ceftriaxone, and aztreonam) at a greater rate than the OXY-1 enzymes did. Comparison of K. oxytoca beta-lactamases with plasmid-mediated extended-spectrum beta-lactamases MEN-1 and TOHO-1 implied that the threonine at position 168 present in OXY-2 beta-lactamase instead of the alanine in OXY-1 could be responsible for its modified substrate hydrolysis. In each group, the beta-lactamase with a variant pI differs from the main form of beta-lactamase by one to five amino acid substitutions. The substrate profile and the 50% inhibitory concentrations revealed that all substitutions differing from the main form of beta-lactamase were neutral except one difference in the OXY-1 group. This substitution of an Ala to a Gly at position 237 increases the hydrolysis of some beta-lactams, particularly aztreonam; decreases the hydrolysis of benzylpenicillin, cephaloridine, and cefamandole, and decreases the susceptibility to clavulanic acid (fivefold increase in the 50% inhibitory concentration). 相似文献
34.
A 24-year-old man was found to have angiographically normal coronary arteries shortly after suffering blunt thoracic trauma. Selective ergonovine administration into the left coronary artery induced total occlusion of the left anterior descending branch and electrical alternans of the ST-segment. This case demonstrates coronary artery spasm as a possible mechanism of coronary occlusion after blunt thoracic trauma. 相似文献
35.
36.
37.
McDonagh Annmarie; Friedman Matthew; McHugo Gregory; Ford Julian; Sengupta Anjana; Mueser Kim; Demment Christine Carney; Fournier Debra; Schnurr Paula P.; Descamps Monica 《Canadian Metallurgical Quarterly》2005,73(3):515
The authors conducted a randomized clinical trial of individual psychotherapy for women with posttraumatic stress disorder (PTSD) related to childhood sexual abuse (n = 74), comparing cognitive-behavioral therapy (CBT) with a problem-solving therapy (present-centered therapy; PCT) and to a wait-list (WL). The authors hypothesized that CBT would be more effective than PCT and WL in decreasing PTSD and related symptoms. CBT participants were significantly more likely than PCT participants to no longer meet criteria for a PTSD diagnosis at follow-up assessments. CBT and PCT were superior to WL in decreasing PTSD symptoms and secondary measures. CBT had a significantly greater dropout rate than PCT and WL. Both CBT and PCT were associated with sustained symptom reduction in this sample. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
38.
EU27 and USA leadership in fruit and vegetable research: a bibliometric study from 2000 to 2009 总被引:1,自引:0,他引:1
Marie-Violaine Tatry Dominique Fournier Benoît Jeannequin Françoise Dosba 《Scientometrics》2014,98(3):2207-2222
We performed an analysis of published literature related to fruit and vegetable and indexed in the Web of Science®, covering the period 2000–2009. The EU27 and the USA are the two leading actors in terms of number of fruit and vegetable articles published. This paper compares their publication outputs using bibliometric methods. We assessed the fruit and vegetable species, topics (from Web of Science® categories), countries and institutions involved. The top species, topics and institutions are ranked according to their number of publications. Collaboration networks between countries were mapped to visualize the intensity of the relationships involved in international fruit and vegetable research and to obtain an overall picture of the fruit and vegetable research landscape. These results can be useful for policy makers. 相似文献
39.
Ramos-Padrón E Bordenave S Lin S Bhaskar IM Dong X Sensen CW Fournier J Voordouw G Gieg LM 《Environmental science & technology》2011,45(2):439-446
Oil sands tailings ponds receive and store the solid and liquid waste from bitumen extraction and are managed to promote solids densification and water recycling. The ponds are highly stratified due to increasing solids content as a function of depth but can be impacted by tailings addition and removal and by convection due to microbial gas production. We characterized the microbial communities in relation to microbial activities as a function of depth in an active tailings pond routinely treated with gypsum (CaSO(4)·2H(2)O) to accelerate densification. Pyrosequencing of 16S rDNA gene sequences indicated that the aerobic surface layer, where the highest level of sulfate (6 mM) but no sulfide was detected, had a very different community profile than the rest of the pond. Deeper anaerobic layers were dominated by syntrophs (Pelotomaculum, Syntrophus, and Smithella spp.), sulfate- and sulfur-reducing bacteria (SRB, Desulfocapsa and Desulfurivibrio spp.), acetate- and H(2)-using methanogens, and a variety of other anaerobes that have been implicated in hydrocarbon utilization or iron and sulfur cycling. The SRB were most abundant from 10 to 14 mbs, bracketing the zone where the sulfate reduction rate was highest. Similarly, the most abundant methanogens and syntrophs identified as a function of depth closely mirrored the fluctuating methanogenesis rates. Methanogenesis was inhibited in laboratory incubations by nearly 50% when sulfate was supplied at pond-level concentrations suggesting that in situ sulfate reduction can substantially minimize methane emissions. Based on our data, we hypothesize that the emission of sulfide due to SRB activity in the gypsum treated pond is also limited due to its high solubility and oxidation in surface waters. 相似文献
40.
Fournier D Halasz A Thiboutot S Ampleman G Manno D Hawari J 《Environmental science & technology》2004,38(15):4130-4133
Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) is a recalcitrant energetic chemical that tends to accumulate in soil, close to the surface. The present study describes the aerobic biodegradability of HMX using Phanerochaete chrysosporium. When added to 7 day old static P. chrysosporium liquid cultures, HMX (600 nmol) degraded within 25 days of incubation. The removal of HMX was concomitant with the formation of transient amounts of its mono-nitroso derivative (1-NO-HMX). The latter apparently degraded via two potential routes: the first involved N-denitration followed by hydrolytic ring cleavage, and the second involved alpha-hydroxylation prior to ring cleavage. The degradation of 1-NO-HMX gave the ring-cleavage product 4-nitro-2,4-diazabutanal (NDAB), nitrite (NO2 -), nitrous oxide (N2O), and formaldehyde (HCHO). Using [14C]-HMX, we obtained 14CO2 (70% in 50 days), representing three C atoms of HMX. Incubation of real soils, contaminated with either HMX (403 micromol kg(-1)) (military base soil) or HMX (3057 micromol kg(-1)), and RDX (342 micromol kg(-1)) (ammunition soil) with the fungus led to 75 and 19.8% mineralization of HMX (liberated 14CO2), respectively, also via the intermediary formation of 1-NO-HMX. Mineralization in the latter soil increased to 35% after the addition of glucose, indicating that a fungus-based remediation process for heavily contaminated soils is promising. The present findings improve our understanding about the degradation pathway of HMX and demonstrate the utility of using the robust and versatile fungus P. chrysosporium to develop effective remediation processes for the removal of HMX. 相似文献