全文获取类型
收费全文 | 395篇 |
免费 | 20篇 |
专业分类
电工技术 | 2篇 |
综合类 | 4篇 |
化学工业 | 63篇 |
金属工艺 | 1篇 |
机械仪表 | 3篇 |
建筑科学 | 34篇 |
能源动力 | 9篇 |
轻工业 | 52篇 |
水利工程 | 3篇 |
石油天然气 | 2篇 |
无线电 | 33篇 |
一般工业技术 | 82篇 |
冶金工业 | 30篇 |
原子能技术 | 5篇 |
自动化技术 | 92篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 5篇 |
2021年 | 7篇 |
2020年 | 9篇 |
2019年 | 9篇 |
2018年 | 10篇 |
2017年 | 7篇 |
2016年 | 18篇 |
2015年 | 11篇 |
2014年 | 21篇 |
2013年 | 26篇 |
2012年 | 29篇 |
2011年 | 36篇 |
2010年 | 23篇 |
2009年 | 30篇 |
2008年 | 35篇 |
2007年 | 25篇 |
2006年 | 9篇 |
2005年 | 16篇 |
2004年 | 21篇 |
2003年 | 6篇 |
2002年 | 9篇 |
2001年 | 3篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 1篇 |
1996年 | 5篇 |
1995年 | 1篇 |
1994年 | 5篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1986年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
排序方式: 共有415条查询结果,搜索用时 15 毫秒
61.
Currently, comparison between countries in terms of their road safety performance is widely conducted in order to better understand one's own safety situation and to learn from those best-performing countries by indicating practical targets and formulating action programmes. In this respect, crash data such as the number of road fatalities and casualties are mostly investigated. However, the absolute numbers are not directly comparable between countries. Therefore, the concept of risk, which is defined as the ratio of road safety outcomes and some measure of exposure (e.g., the population size, the number of registered vehicles, or distance travelled), is often used in the context of benchmarking. Nevertheless, these risk indicators are not consistent in most cases. In other words, countries may have different evaluation results or ranking positions using different exposure information. In this study, data envelopment analysis (DEA) as a performance measurement technique is investigated to provide an overall perspective on a country's road safety situation, and further assess whether the road safety outcomes registered in a country correspond to the numbers that can be expected based on the level of exposure. In doing so, three model extensions are considered, which are the DEA based road safety model (DEA-RS), the cross-efficiency method, and the categorical DEA model. Using the measures of exposure to risk as the model's input and the number of road fatalities as output, an overall road safety efficiency score is computed for the 27 European Union (EU) countries based on the DEA-RS model, and the ranking of countries in accordance with their cross-efficiency scores is evaluated. Furthermore, after applying clustering analysis to group countries with inherent similarity in their practices, the categorical DEA-RS model is adopted to identify best-performing and underperforming countries in each cluster, as well as the reference sets or benchmarks for those underperforming ones. More importantly, the extent to which each reference set could be learned from is specified, and practical yet challenging targets are given for each underperforming country, which enables policymakers to recognize the gap with those best-performing countries and further develop their own road safety policy. 相似文献
62.
Wang L Bogaerts W Dumon P Selvaraja SK Teng J Pathak S Han X Wang J Jian X Zhao M Baets R Morthier G 《Applied optics》2012,51(9):1251-1256
Athermal arrayed waveguide gratings (AWGs) in silicon-on-insulator (SOI) are experimentally demonstrated for the first time to our knowledge. By using narrowed arrayed waveguides, and then overlaying a polymer layer, the wavelength temperature dependence of the AWGs is successfully reduced to -1.5 pm/°C, which is more than 1 order of magnitude less than that of normal SOI AWGs. The athermal behavior of the AWGs is obtained with little degradation of their performance. For the central channel, the cross talk is less than -15 dB and the insertion loss is around 2.6 dB. Good characteristics can be maintained with temperatures up to 75 °C. The total size of the device is 350 μm × 250 μm. 相似文献
63.
The objective of this research is to explain why actors are not using interorganizational information and communication technology (ICT) in construction projects in the intended way, by determining the mechanisms that influence the way actors use this ICT over time during a construction project. This explorative research results in a theoretical model that contains four key categories that explains the way actors use ICT in construction projects: (1) personal motivation; (2) external motivation; (3) knowledge and skills; and (4) acting opportunities. The model is compared with three existing influential models about the adoption and use of ICT: the unified theory of acceptance and use of technology, the theory of planned behavior, and the technology acceptance model. In these models missing elements are found. In addition, it is found that fundamental characteristics of construction projects, such as the fragmented and temporarily nature of construction projects, and the different working practices, resources, and objectives of the organizations involved cause most of the barriers to the intended use of interorganizational ICT. 相似文献
64.
Occurrence,prevention and remediation of toxigenic fungi and mycotoxins in silage: a review 总被引:1,自引:0,他引:1 下载免费PDF全文
Eva Wambacq Ilse Vanhoutte Kris Audenaert Leen De Gelder Geert Haesaert 《Journal of the science of food and agriculture》2016,96(7):2284-2302
Ruminants are considered to be less sensitive towards mycotoxins than monogastric animals because rumen microbiota have mycotoxin‐detoxifying capacities. Therefore the effect of mycotoxins towards ruminants has been studied to a lesser extent compared with monogastric animals. Worldwide, a high proportion of the ruminant diet consists of silages made of forage crops (i.e. all parts of the crop above the stubble are harvested). In practice, silages are often contaminated with multiple mycotoxins. Exposure to a cocktail of mycotoxins can hamper animal production and have severe health consequences. In this article the different aspects associated with mycotoxin contamination of silage are reviewed ‘from seed to feed’. An overview is given on the occurrence of toxigenic fungal species and their concomitant mycotoxins in forage crops before and after ensiling. The mycotoxin load of visually non‐mouldy samples and mouldy hot spots within the same silo is also compared. Subsequently, this review delves into different problem‐solving strategies. A logical first step is prevention of mould growth and mycotoxin production in the field, during harvest and during ensiling. If prevention should fail, several remediation strategies are available. These are listed, mainly focusing on the possibilities of microbial degradation of mycotoxins in vivo in silage. © 2015 Society of Chemical Industry 相似文献
65.
Delphine S.A. Beeckman Geert Meesen Patrick Van Oostveldt Daisy Vanrompay 《Microscopy research and technique》2009,72(5):398-402
Traditionally, the amount of infective chlamydiae in a given sample is determined by inoculating dilution series into cell cultures and physically counting chlamydial inclusions. This approach is time consuming, tedious, and error prone, mainly when dealing with high titers. Therefore, this paper describes a largely automated technique that was developed to standardize the determination of chlamydial load in vitro. Cells are fixed at 36 h post-inoculation and bacteria visualized using standard immunological detection methods. Consequently, for 81 microscopic fields, an image is recorded at the interpolated focal plane. These images are then automatically processed using an ImageJ plugin and the obtained results are imported into Excel to determine the number of inclusion forming units per mL in the sample. The main advantage of this technique is that no or minimal sample dilution is required, thus minimizing dilution errors. In addition, this technique was employed during the early, middle and late growth stages of the chlamydial developmental cycle and results correlated well (P < 0.01) with 16S rRNA values from previous experiments, thereby proving its suitability to follow chlamydial growth in vitro. The method described is highly suitable for high throughput titration of cell culture inoculated samples and assessment of possible antichlamydial effects of novel compounds throughout the chlamydial growth cycle. Microsc. Res. Tech., 2009. © 2009 Wiley-Liss, Inc. 相似文献
66.
Dik J Janssens K Van der Snickt G van der Loeff L Rickers K Cotte M 《Analytical chemistry》2008,80(16):6436-6442
Vincent van Gogh (1853-1890), one of the founding fathers of modern painting, is best known for his vivid colors, his vibrant painting style, and his short but highly productive career. His productivity is even higher than generally realized, as many of his known paintings cover a previous composition. This is thought to be the case in one-third of his early period paintings. Van Gogh would often reuse the canvas of an abandoned painting and paint a new or modified composition on top. These hidden paintings offer a unique and intimate insight into the genesis of his works. Yet, current museum-based imaging tools are unable to properly visualize many of these hidden images. We present the first-time use of synchrotron radiation based X-ray fluorescence mapping, applied to visualize a woman's head hidden under the work Patch of Grass by Van Gogh. We recorded decimeter-scale, X-ray fluorescence intensity maps, reflecting the distribution of specific elements in the paint layers. In doing so we succeeded in visualizing the hidden face with unprecedented detail. In particular, the distribution of Hg and Sb in the red and light tones, respectively, enabled an approximate color reconstruction of the flesh tones. This reconstruction proved to be the missing link for the comparison of the hidden face with Van Gogh's known paintings. Our approach literally opens up new vistas in the nondestructive study of hidden paint layers, which applies to the oeuvre of Van Gogh in particular and to old master paintings in general. 相似文献
67.
Geert?van?Campenhout Tom?van?CaneghemEmail author Steve?van?Uytbergen 《Scientometrics》2008,77(1):61-90
In most scientific disciplines, a number of divergent and often highly specialized research areas are examined, which is reflected
in substantial differences among journal scopes. Using the accounting literature as an example, we argue that this diversity
in scopes should be considered when assessing journal influence. Concretely, we examine a citation-based structural influence
measure for a sample of 41 accounting journals. Next, we identify sub-areas in the accounting literature and we explore journal
influence in these sub-areas. Our results clearly demonstrate the importance of distinguishing between overall and sub-area
influence. In addition, we show that sub-areas should be identified using a fuzzy clustering procedure. 相似文献
68.
运用环境扫描电镜、能谱仪和X射线衍射等微观分析手段研究了稳定环境中,半浸泡混凝土试件在硫酸钠和硫酸镁溶液中的劣化破坏特征,以及混凝土碳化对"混凝土硫酸盐结晶破坏"的影响。结果表明:粗骨料界面过渡区生成的大量钙矾石和石膏等晶体是引起混凝土试件劣化的原因;在碳化混凝土内发现了硫酸钠结晶破坏现象。 相似文献
69.
Pyrethrins Protect Pyrethrum Leaves Against Attack by Western Flower Thrips, <Emphasis Type="Italic">Frankliniella occidentalis</Emphasis> 总被引:1,自引:0,他引:1
Yang T Stoopen G Wiegers G Mao J Wang C Dicke M Jongsma MA 《Journal of chemical ecology》2012,38(4):370-377
Pyrethrins are active ingredients extracted from pyrethrum flowers (Tanacetum cinerariifolium), and are the most widely used botanical insecticide. However, several thrips species are commonly found on pyrethrum flowers
in the field, and are the dominant insects found inside the flowers. Up to 80 % of western flower thrips (WFT, Frankliniella occidentalis) adults died within 3 days of initiating feeding on leaves of pyrethrum, leading us to evaluate the role of pyrethrins in
the defense of pyrethrum leaves against WFT. The effects of pyrethrins on WFT survival, feeding behavior, and reproduction
were measured both in vitro and in planta (infiltrated leaves). The lethal concentration value (LC50) for pyrethrins against WFT adults was 12.9 mg/ml, and pyrethrins
at 0.1 % (w/v) and 1 % (w/v) had significantly negative effects on feeding, embryo development, and oviposition. About 20-70 %
of WFT were killed within 2 days when they were fed chrysanthemum leaves containing 0.01-1 % pyrethrins. Chrysanthemum leaves
containing 0.1 % or 1 % pyrethrins were significantly deterrent to WFT. In a no-choice assay, the reproduction of WFT was
reduced significantly when the insects were fed leaves containing 0.1 % pyrethrins, and no eggs were found in leaves containing
1 % pyrethrins. Our results suggest that the natural concentrations of pyrethrins in the leaves may be responsible for the
observed high mortality of WFT on pyrethrum. 相似文献
70.
Ma Y King AP Gogin N Gijsbers G Rinaldi CA Gill J Razavi R Rhode KS 《IEEE transactions on bio-medical engineering》2012,59(1):122-131
X-ray fluoroscopically guided cardiac electrophysiological procedures are routinely carried out for diagnosis and treatment of cardiac arrhythmias. X-ray images have poor soft tissue contrast and, for this reason, overlay of static 3-D roadmaps derived from preprocedural volumetric data can be used to add anatomical information. However, the registration between the 3-D roadmap and the 2-D X-ray image can be compromised by patient respiratory motion. Three methods were designed and evaluated to correct for respiratory motion using features in the 2-D X-ray images. The first method is based on tracking either the diaphragm or the heart border using the image intensity in a region of interest. The second method detects the tracheal bifurcation using the generalized Hough transform and a 3-D model derived from 3-D preoperative volumetric data. The third method is based on tracking the coronary sinus (CS) catheter. This method uses blob detection to find all possible catheter electrodes in the X-ray image. A cost function is applied to select one CS catheter from all catheter-like objects. All three methods were applied to X-ray images from 18 patients undergoing radiofrequency ablation for the treatment of atrial fibrillation. The 2-D target registration errors (TRE) at the pulmonary veins were calculated to validate the methods. A TRE of 1.6 mm ± 0.8 mm was achieved for the diaphragm tracking; 1.7 mm ± 0.9 mm for heart border tracking, 1.9 mm ± 1.0 mm for trachea tracking, and 1.8 mm ± 0.9 mm for CS catheter tracking. We present a comprehensive comparison between the techniques in terms of robustness, as computed by tracking errors, and accuracy, as computed by TRE using two independent approaches. 相似文献