首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   275篇
  免费   7篇
电工技术   6篇
化学工业   70篇
金属工艺   2篇
机械仪表   1篇
建筑科学   14篇
能源动力   10篇
轻工业   14篇
水利工程   6篇
无线电   19篇
一般工业技术   47篇
冶金工业   65篇
原子能技术   6篇
自动化技术   22篇
  2023年   1篇
  2022年   6篇
  2021年   5篇
  2020年   3篇
  2019年   5篇
  2018年   4篇
  2017年   5篇
  2016年   3篇
  2015年   3篇
  2014年   6篇
  2013年   12篇
  2012年   10篇
  2011年   12篇
  2010年   9篇
  2009年   7篇
  2008年   4篇
  2007年   9篇
  2006年   12篇
  2005年   6篇
  2004年   8篇
  2003年   7篇
  2002年   10篇
  2001年   6篇
  2000年   11篇
  1999年   9篇
  1998年   20篇
  1997年   18篇
  1996年   13篇
  1995年   8篇
  1994年   7篇
  1993年   7篇
  1992年   1篇
  1991年   6篇
  1990年   3篇
  1989年   1篇
  1988年   3篇
  1985年   5篇
  1983年   1篇
  1982年   5篇
  1981年   2篇
  1977年   1篇
  1976年   4篇
  1974年   1篇
  1972年   1篇
  1971年   1篇
  1970年   1篇
排序方式: 共有282条查询结果,搜索用时 31 毫秒
1.
The TELEMAC project brings new methodologies from the Information and Science Technologies field to the world of water treatment. TELEMAC offers an advanced remote management system which adapts to most of the anaerobic wastewater treatment plants that do not benefit from a local expert in wastewater treatment. The TELEMAC system takes advantage of new sensors to better monitor the process dynamics and to run automatic controllers that stabilise the treatment plant, meet the depollution requirements and provide a biogas quality suitable for cogeneration. If the automatic system detects a failure which cannot be solved automatically or locally by a technician, then an expert from the TELEMAC Control Centre is contacted via the internet and manages the problem.  相似文献   
2.
Brainstem auditory evoked responses of 355 patients with uni- or bilateral tinnitus were recorded in order to evaluate the effect of tinnitus on the central auditory system. The amplitudes of waves I, III and V and the latencies of each wave and interpeak latencies were compared to those of a group of 129 controls with normal hearing. The study of the control group initially identified a certain number of concurrent parameters. The brainstem evoked responses of men and women evolved differently from the age of 30 years, latencies of I-III and I-V in men lengthening with age and those of women tending to shorten. The patient groups were therefore compared to a control group of the same sex ratio or of the same sex, half being between 30 and 56 years of age. The tinnitus patients were divided into three groups according to the side affected by tinnitus. Latencies and amplitudes in these groups differed significantly from those of the control group. In order to eliminate hearing loss, the most difficult concurrent factor and almost always associated with tinnitus, the results of individuals with symmetrical hearing loss were compared to those of the control group. Tinnitus was always associated with significant lengthening of 0-I and I-V latencies on the tinnitus-affected side, with a significant reduction in amplitudes of waves I and III, and sometimes of wave V, particularly in the group with left-sided tinnitus. Comparison of tinnitus patients with symmetrical and asymmetrical hearing by sex showed that tinnitus patients of all groups had lengthening of right and left 0-I latencies, apart from the women in the group with right-sided tinnitus, and significant reduction in amplitudes of waves I and III in women and of left III only in men. When hearing loss was asymmetrical and on the tinnitus-affected side, there was also lengthening of 0-I latencies on the tinnitus-affected side in both sexes and of ipsi- and contralateral I-V latencies in women. Right- and left-sided tinnitus was associated with additional differences between the three groups. Correlation coefficient study confirmed that 0-I, I- III and I-V latencies were independent of the mean degree of deafness, deafness at high frequencies and at frequencies around the tinnitus, up to a threshold of hearing loss of 40 dB, above which 0-I and 0-V lengthened in addition to tinnitus. On the other hand, whatever the frequency, tinnitus involved significant lengthening of wave I latencies and modification of the previously recorded amplitudes. Two groups of tinnitus patients could be distinguished: the first, with symmetrical hearing loss, with symmetrical normal latencies, apart from 0-I latencies and the amplitude of the wave on the tinnitus side, and the second with hearing loss predominant on the tinnitus-affected side, with different latencies on each side, 0-I being shorter on the unaffected side, I-III and I-V being lengthened on the unaffected side and 0-I being lengthened on the tinnitus-affected side. Moreover, as disturbances of brainstem evoked responses caused by tinnitus particularly affected waves I and III, the hypothesis of possible involvement of the efferent systems could be proposed.  相似文献   
3.
4.
Analysing the Diversity of Water Pricing Structures: The Case of France   总被引:1,自引:1,他引:0  
This paper presents the results of a 2003 national survey of urban water pricing structure implemented by 429 district level water utilities. After providing some background elements on the diversity of existing water pricing structures, the paper shows how each structure can be used to achieve different management objectives (water allocation efficiency, costs recovery, and equity). It then describes the structures adopted by French water utilities, showing that flat rate are rarely adopted; declining blocks frequently used; and increasing blocks pricing which should be used to promote water use efficiency remain extremely rare. A statistical clustering is then conducted and a typology of situations elaborated. The paper concludes with highlighting that current pricing structures are influenced by past practices and that the dominant objective of water utilities is to cover costs.  相似文献   
5.
cDNA clones encoding giant catfish (Pangasianodon gigas) growth hormone (GH) have been isolated using a polymerase chain reaction (PCR) strategy. Pairwise combinations of degenerate and general primers allowed for the amplification of regions both 3' and 5' to the point of entry into the message. The amplified PCR products were cloned and sequenced. The cDNA sequence was found to encode a polypeptide of 200 amino acids (aa), including a putative signal peptide of 22 aa. The 5' and 3' untranslated regions of the message are 58 and 515 nucleotides long, respectively. The giant catfish GH displays the highest aa sequence homology with the carp GH, with 80% of sequence identity. Moreover, giant catfish GH has structural features in common with both mammalian and avian GH polypeptides, and also contains the domains of conserved sequence found in other GH.  相似文献   
6.
In eight Japanese patients, three different laparoscopic procedures were used to excise an early gastric carcinoma; partial resection in four, intragastric resection of the gastric mucosa in two, and laparoscopic-assisted distal partial gastrectomy with the abdominal wall-elevating method in two patients. Histological examinations revealed that the lesions were completely resected, and there was no evidence of lymphatic metastasis. The operation time ranged from 2 to 4 h. These forms of laparoscopic gastric surgery for patients with early gastric carcinomas may be useful from the standpoint of minimal access, rapid recovery, less pain, and good cosmesis.  相似文献   
7.
When European laboratories decided to develop a digital sound broadcasting system (DSB), they specified three main conditions to fulfil:
  • quality improvement up to the level of ‘CD’ sound, even in difficult reception conditions (mobile vehicles, etc)
  • additional significant digital data transmissions in order to transform sound broadcasting into a really new service
  • the possibility of a common system for satellite and terrestrial transmissions.
It is on these bases that the European project ‘Eureka 147’ defined the system called DAB (digital audio broadcasting). In 1992, the ITU Conference WARC 92 allocated 40 MHz to DSB in the L-band in the configuration of complementary terrestrial and satellite networks; nevertheless, the present state of technical possibilities makes such mixed networks almost unfeasible and the lack of available spectrum in VHF bands led a significant number of countries to envisage L-band for T-DAB. The situation could turn to a competition between terrestrial and satellite networks, especially because the bandwidth in L-band is not that large! France belongs to the countries facing this problem. L-band alone is intended to be used by T-DAB, and broadcasters taking part in the work of ‘Club DAB’ estimated that 20 MHz would be a minimum to ensure the success of T-DAB introduction. It is half of the DSB band. Splitting this band into two parts has already been decided by CEPT, but in the proportion of 1/3 for T-DAB. This organization intends to arrange a European planning meeting for T-DAB in July 1995, and, shortly after, several countries are ready to start the implementation of the terrestrial networks. At the same time, international broadcasters wonder whether satellite transmission could present an alternative to HF.  相似文献   
8.
The development of alliance-based software requires the collaboration of many stakeholders. These different stakeholders across multiple organizations form a complex social network. The goal of this paper is to develop a novel modeling framework, which will help task managers devise optimal workforce assignments considering both short-term and long-term aspects of the software development process. The proposed framework is composed of an assignment module and a prediction module. For a given task, the assignment module first selects a candidate workforce mix. Based on the candidate workforce mix, the prediction module then predicts the short-term performance (productivity) as well as the long-term performance (workforce training and robustness of the organization) of the organization. Then, the assignment module selects another candidate mix, and this iteration continues until an optimal workforce mix is found. The prediction module and the assignment module are based on an agent-based simulation method and a multi-objective optimization model, respectively. The proposed modeling framework is illustrated with a software enhancement request process in Kuali, an alliance-based open source software development project involving 12 organizations. The constructed framework is executed with varying parameters to demonstrate its use and benefit in the software enhancement process.  相似文献   
9.
Zn and Zn–Ni alloy coatings were electrodeposited on mild steel from sulfate-based bath containing Sn as additive. The effect of Ni content on the microstructure, morphology, microhardness and the tribological behavior of these coatings were studied and discussed. Adding Sn in the sulfate bath had a significant effect on the surface morphology, particularly on the Zn–8 wt% Ni coatings. By increasing the Ni concentration from 8 to 14 wt%, the X-ray patterns showed that the phase structure of Zn–Ni alloy coatings was changed from η-phase Ni3Zn22 to γ-phase Ni5Zn21. The plastic deformation and delamination were found to be wear mechanisms for the investigated coatings. While the Zn–14 wt% Ni alloys had the best wear resistance, Zn films had the most severe wear volume loss and the highest friction coefficient.  相似文献   
10.
The quality level of a mechanism can be evaluated a posteriori after several months by following the number of warranty returns. However, it is more interesting to evaluate a predicted quality level in the design stage: this is one of the aims of statistical tolerance analysis. A possible method consists of computing the defect probability (PD) expressed in ppm. It represents the probability that a functional requirement will not be satisfied in mass production. For assembly reasons, many hyperstatic mechanisms require gaps, which their functional requirements depend on. The defect probability assessment of such mechanisms is not straightforward, and requires advanced numerical methods. This problem particularly interests the VALEO W.S. company, which experiences problems with an assembly containing gaps. This paper proposes an innovative methodology to formulate and compute the defect probability of hyperstatic mechanisms with gaps in two steps. First, a complex feasibility problem is converted into a simpler problem. Then the defect probability is efficiently computed thanks to system reliability methods and the m-dimensional multivariate normal distribution Φm. Finally, a sensitivity analysis is provided to improve the original design. The whole approach is illustrated with an industrial case study, but can be adapted to other similar problems.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号