全文获取类型
收费全文 | 92篇 |
免费 | 7篇 |
专业分类
化学工业 | 14篇 |
机械仪表 | 2篇 |
建筑科学 | 3篇 |
能源动力 | 5篇 |
轻工业 | 15篇 |
水利工程 | 3篇 |
无线电 | 5篇 |
一般工业技术 | 14篇 |
冶金工业 | 7篇 |
自动化技术 | 31篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 2篇 |
2019年 | 2篇 |
2018年 | 3篇 |
2017年 | 7篇 |
2016年 | 3篇 |
2015年 | 4篇 |
2014年 | 3篇 |
2013年 | 7篇 |
2012年 | 6篇 |
2011年 | 1篇 |
2010年 | 6篇 |
2009年 | 3篇 |
2008年 | 2篇 |
2007年 | 1篇 |
2006年 | 5篇 |
2005年 | 2篇 |
2004年 | 3篇 |
2003年 | 6篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1998年 | 7篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 2篇 |
1993年 | 2篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1982年 | 1篇 |
1976年 | 1篇 |
1958年 | 1篇 |
排序方式: 共有99条查询结果,搜索用时 15 毫秒
91.
Lucia De Stefano Pedro Martínez-Santos Fermín Villarroya Daniel Chico Luis Martínez-Cortina 《Water Resources Management》2013,27(7):2691-2707
The European Union (EU) Water Framework Directive (WFD) requires EU countries to achieve good status of all their waters by 2015. This should be achieved through the implementation of river basin management plans (RBMPs), which in turn are based on water resources baseline data. While it is too soon to assess the WFD effectiveness, the planning process has contributed to identify possible pitfalls of the WFD design and has provided an opportunity to enhance the knowledge of European water resources. Groundwater plays a strategic role in Spain’s economy and also in the maintenance of its aquatic ecosystems, making that country an excellent testing ground for getting an insight into the definition of baseline groundwater under the WFD mandate. This paper presents the results of compiling the information produced for the RBMPs to attain an overall picture at a national scale. In doing so, it examines some of the methodological and technical choices involved in the definition of a baseline for groundwater, assessing their practical consequences on groundwater management. This paper argues that having baseline figures for the RBMPs required compromises or shortcuts to be taken. Undoubtedly, the process leading to the first WFD Plans has been an extremely enriching learning process, but it leaves questions unanswered. The periodic (6 year) RBMP revision should become an opportunity to revisit and better tune the baseline conditions established during this first planning cycle. 相似文献
92.
Pavel Rizo-Acosta Fermín Cuevas Michel Latroche 《International Journal of Hydrogen Energy》2018,43(34):16774-16781
Magnesium hydride is extensively examined as a hydrogen store due to its high hydrogen content and low cost. However, high thermodynamic stability and sluggish kinetics hinder its practical application. To overcome this last drawback, different Ti amounts (y = 0, 0.025, 0.05, 0.1, 0.2 and 0.3) were added to magnesium to form (1-y)MgH2+yTiH2 nanocomposites (NC) by reactive ball milling under hydrogen gas. Thermodynamic stability of the MgH2 phase in NCs was determined using a manometric Sieverts rig. Reversible hydrogen capacity and reaction kinetics were determined at 573 K over 20 sorption cycles under a limited reaction time of 15 min. On increasing Ti amount, reaction kinetics are enhanced both in absorption and desorption leading to a higher reversibility for hydrogen storage with the MgH2 phase. However, titanium increases the molar weight of NCs and forms irreversible titanium hydride. The highest reversible capacity (4.9 wt% H) was obtained for the lowest here studied TiH2 content (y = 0.025). 相似文献
93.
Othmane MH Carriedo JA De la Fuente F San Primitivio F 《The Journal of dairy research》2002,69(1):53-62
A total of 7492 test-day observations for mean contents of fat, protein, casein, serum protein and lactose and individual laboratory cheese yield (ILCY) were obtained, at approximately monthly intervals, from 1119 ewes belonging to eight Churra dairy flocks. The effect of various factors on these variables was examined and phenotypic correlations among all traits were estimated. Least squares analyses showed significant effects of flock test-date, stage of lactation, age of ewe, and number of lambs weaned on almost all variables. Protein content and composition were not affected by the number of lambs weaned. ILCY had an unadjusted mean (26-55 kg cheese/100 l milk) close to those reported for real cheese yield in dairy ewes and was affected similarly to the main milk components. Fat, protein, casein, and serum protein contents, and ILCY, showed a generally increasing trend as lactation progressed. These components reached a minimum at 1 month into lactation, when milk yield was highest, and increased for the remainder of the lactation. ILCY depended mainly on fat, protein and casein contents. Protein and casein contents were closely related and equally correlated with ILCY. An increase in somatic cell count (SCC) was associated with decreased milk yield and decreased lactose content. 相似文献
94.
95.
Motion segmentation using occlusions 总被引:4,自引:0,他引:4
Ogale AS Fermüller C Aloimonos Y 《IEEE transactions on pattern analysis and machine intelligence》2005,27(6):988-992
We examine the key role of occlusions in finding independently moving objects instantaneously in a video obtained by a moving camera with a restricted field of view. In this problem, the image motion is caused by the combined effect of camera motion (egomotion), structure (depth), and the independent motion of scene entities. For a camera with a restricted field of view undergoing a small motion between frames, there exists, in general, a set of 3D camera motions compatible with the observed flow field even if only a small amount of noise is present, leading to ambiguous 3D motion estimates. If separable sets of solutions exist, motion-based clustering can detect one category of moving objects. Even if a single inseparable set of solutions is found, we show that occlusion information can be used to find ordinal depth, which is critical in identifying a new class of moving objects. In order to find ordinal depth, occlusions must not only be known, but they must also be filled (grouped) with optical flow from neighboring regions. We present a novel algorithm for filling occlusions and deducing ordinal depth under general circumstances. Finally, we describe another category of moving objects which is detected using cardinal comparisons between structure from motion and structure estimates from another source (e.g., stereo). 相似文献
96.
Gonzalo C Tardáguila JA De La Fuente LF San Primitivo F 《The Journal of dairy research》2004,71(1):33-38
The study was carried out in a commercial flock on 286 Churra breed ewes (566 half-udders) assigned to three lots depending on the type of antibiotic dry therapy received in the lactation previous to the one studied. One-hundred-and-four ewes were given complete therapy in all udders, 103 received selective therapy of infected half-udders, and 79 received no therapy at all. Half-udders of all animals were sampled for bacteriological study at < or = 72 h (lambing), 60 d, 120 d, and 155 d (drying-off) post partum. Dry therapy, parity number, lactation stage and therapy x parity interaction contributed significantly to variation in intramammary infection prevalence. Antibiotic dry therapy had the most significant effect. Prevalence during the whole of the subsequent lactation was significantly lower in lots receiving complete (18.8%) and selective (15.6%) dry therapy than in the untreated control lot (48.3%). Coagulase-negative staphylococci and streptococci (in particular Streptococcus agalactiae) were the organisms most significantly affected by dry therapy. In untreated ewes, prevalence increased noticeably from the 2nd to the 6th and subsequent lactations, but no significant changes were observed in the treated lots. Milk yield in the dry treated lots was 6.9% higher that in the untreated one. It was concluded that complete and selective treatments of ewes at drying-off were efficient and comparable methods of reducing the intramammary infection prevalence, improving bacteriological quality of milk, and increasing milk yield. 相似文献
97.
Directions of Motion Fields are Hardly Ever Ambiguous 总被引:2,自引:2,他引:0
Brodsky Tomas Fermüller Cornelia Aloimonos Yiannis 《International Journal of Computer Vision》1998,26(1):5-24
International Journal of Computer Vision - If instead of the full motion field, we consider only the direction of the motion field due to a rigid motion, what can we say about the three-dimensional... 相似文献
98.
Birch production and utilization for energy 总被引:1,自引:0,他引:1
Ari Ferm 《Biomass & bioenergy》1993,4(6):391-404
Natural birch stands represent a significant biomass resource since birches are one of the most common deciduous genera in cool temperate regions, even in places ranging up to the forest line. Many characteristics of birch make it highly suited for short rotation forestry. However, growing birch in very short rotations (less than 10 years) in northern climates is not worthwhile on the basis of biomass production and economics. Rotations of 15 to 20 years may give good results everywhere. The intensive culture of birch plantations has largely remained untested, but it is very likely that the yield levels can be increased significantly by using cloned material as well as improved silvicultural treatments, fertilization and pest control. Birch feedstock, compared to material of many other tree species, is of even quality. Moisture content is low and basic density high. Branches and bark are also suitable for energy use. Birch plays an important part in the energy budget of entire nations, particularly of Finland and Sweden 相似文献
99.
Zhiya Han Diana Tranca Fermín Rodríguez-Hernández Kaiyue Jiang Jichao Zhang Mingyuan He Fu Wang Sheng Han Peng Wu Xiaodong Zhuang 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(17):2208102
Ammonia is a key chemical feedstock worldwide. Compared with the well-known Haber–Bosch method, electrocatalytic nitrogen reduction reaction (ENRR) can eventually consume less energy and have less CO2 emission. In this study, a plasma-enhanced chemical vapor deposition method is used to anchor transition metal element onto 2D conductive material. Among all attempts, Ru single-atom and Ru-cluster-embedded perovskite oxide are discovered with promising electrocatalysis performance for ENRR (NH3 yield rate of up to 137.5 ± 5.8 µg h−1 mgcat−1 and Faradaic efficiency of unexpected 56.9 ± 4.1%), reaching the top record of Ru-based catalysts reported so far. In situ experiments and density functional theory calculations confirm that the existence of Ru clusters can regulate the electronic structure of Ru single atoms and decrease the energy barrier of the first hydrogenation step (*NN to *NNH). Anchoring Ru onto various 2D perovskite oxides (LaMO-Ru, MCr, Mn, Co, or Ni) also show boosted ENRR performance. Not only this study provides an unique strategy toward transition-metal-anchored new 2D conductive materials, but also paves the way for fundamental understanding the correlation between cluster-involved single-atom sites and catalytic performance. 相似文献