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   399篇
  免费   2篇
电工技术   3篇
化学工业   64篇
金属工艺   23篇
机械仪表   3篇
建筑科学   6篇
能源动力   7篇
轻工业   7篇
水利工程   4篇
石油天然气   2篇
无线电   75篇
一般工业技术   51篇
冶金工业   59篇
原子能技术   3篇
自动化技术   94篇
  2024年   3篇
  2023年   4篇
  2022年   4篇
  2021年   6篇
  2020年   6篇
  2019年   8篇
  2018年   6篇
  2017年   10篇
  2016年   10篇
  2015年   7篇
  2014年   9篇
  2013年   19篇
  2012年   16篇
  2011年   13篇
  2010年   12篇
  2009年   20篇
  2008年   20篇
  2007年   12篇
  2006年   23篇
  2005年   9篇
  2004年   13篇
  2003年   10篇
  2002年   8篇
  2001年   10篇
  2000年   10篇
  1999年   8篇
  1998年   24篇
  1997年   15篇
  1996年   11篇
  1995年   9篇
  1994年   4篇
  1993年   8篇
  1992年   2篇
  1991年   2篇
  1990年   2篇
  1989年   4篇
  1988年   3篇
  1987年   2篇
  1986年   7篇
  1985年   3篇
  1984年   4篇
  1982年   3篇
  1981年   3篇
  1980年   3篇
  1979年   4篇
  1977年   2篇
  1976年   2篇
  1975年   4篇
  1973年   2篇
  1972年   1篇
排序方式: 共有401条查询结果,搜索用时 15 毫秒
361.
In a joint project the Universidade Federal de Uberlândia and the German Aerospace Center are developing solar water treatment technologies for industrial applications. Wastewater from chip-board production is difficult to detoxify by standard processes. Different advanced oxidation processes using solar light were tested on this effluent. In opposition to TiO2 treatment, the application of the photo-Fenton process using a compound parabolic collector (CPC) type solar reactor shows excellent results, with a reduction in the COD higher than 70% with the application of about 800 kJ m−2 of UVA radiation. HPLC analysis shows an efficient degradation of the organic matter present in the effluent (formaldehyde, melamine, urea, wood extractives, lignin and urea/formaldehyde and melamine/formaldehyde resins fragments) prior to their complete disappearance.  相似文献   
362.
The purpose of this paper is to present a new approach for measurand uncertainty characterization. The Markov chain Monte Carlo (MCMC) is applied to measurand probability density function (pdf) estimation, which is considered as an inverse problem. The measurement characterization is driven by the pdf estimation in a nonlinear Gaussian framework with unknown variance and with limited observed data. These techniques are applied to a realistic measurand problem of groove dimensioning using remote field eddy current (RFEC) inspection. The application of resampling methods such as bootstrap and the perfect sampling for convergence diagnostics purposes gives large improvements in the accuracy of the MCMC estimates.  相似文献   
363.
A direct sequence (DS) spread spectrum code division multiple access (CDMA) communication system is considered where several users transmit data symbols over different multipath channels. The main objective of this work is the proposal of a sequential algorithm for joint parameter estimation and multiuser data detection. The computationally prohibitive maximization of the log-likelihood function is replaced by a sequential scheme using the multistage detector for recovering the data symbols and the expectation-maximization algorithm for estimating the channel parameters. The performance of the resulting multiuser receiver is evaluated via Monte Carlo simulations using both synthetic as well as measured channel impulse responses. A comparison of the performance with analytical expressions for the single-user single-path case shows that the proposed system is capable of eliminating the near-far effect existing in conventional DS/CDMA systems.  相似文献   
364.
Women may choose to initiate, reinitiate, or discontinue hormone replacement therapy (HRT) at any time beyond the perimenopausal period. HRT, exercise, and nutrition are reviewed in terms of their potential benefits as primary and secondary preventive therapies against coronary heart disease, osteoporosis, breast and genital cancers, and the maintenance of cognitive function among older postmenopausal women. Lifestyle alternatives involving nutrition and exercise that offer many of the same benefits as HRT are discussed. Since both pharmacologic and lifestyle interventions offer significant benefit for primary and secondary prevention of disease and disability, each should be offered to women for consideration as they enter the perimenopausal period. Additionally, each can be recommended for initiation even at much older ages and subsequent to adverse health occurrences, such as the experience of breast or genital cancer or a cardiac event. Each should be sustained over the long term. The decision whether to discontinue these interventions among the most elderly will be influenced by other quality of life considerations.  相似文献   
365.
Previous studies characterized the third variable (V3) loop of the envelope gp120 as the principal neutralizing determinant for laboratory T-cell-line-adapted (TCLA) strains of human immunodeficiency virus type 1 (HIV-1). However, primary viruses isolated from infected individuals are more refractory to neutralization than TCLA strains, suggesting that qualitatively different neutralizing antibodies may be involved. In this study, we investigated whether the V3 loop constitutes a linear target epitope for antibodies neutralizing primary isolates. By using peptides representative of the V3 regions of various primary isolates, an early, relatively specific and persistent antibody response was detected in sera from HIV-infected patients. To assess the relationship between these antibodies and neutralization, the same peptides were used in competition and depletion experiments. Addition of homologous V3 peptides led to a competitive inhibition in the neutralization of the TCLA strain HIVMN/MT-4 but had no effect on the neutralization of the autologous primary isolate. Similarly, the removal of antibodies that bind to linear V3 epitopes resulted in a loss of HIVMN/MT-4 neutralization, whereas no decrease in the autologous neutralization was measured. The different roles of V3-specific antibodies according to the virus considered were thereby brought to light. This confirmed the involvement of V3 antibodies in the neutralization of a TCLA strain but emphasized a more pronounced contribution of either conformational epitopes or epitopes outside the V3 loop as targets for antibodies neutralizing primary HIV-1 isolates. This result underlines the need to focus on new vaccinal immunogens with epitopes able to induce broadly reactive and efficient antibodies that neutralize a wide range of primary HIV-1 isolates.  相似文献   
366.
A mathematical model is developed for calculating linear sloshing effects in the dynamic response of horizontal-cylindrical and spherical liquid containers under external excitation, with emphasis on earthquake excitation. The velocity potential is expressed in a series form, where each term is the product of a time function and the associated spatial function. Because of the configuration of the containers, the associated spatial functions are nonorthogonal and the problem is not separable, resulting in a system of coupled nonhomogeneous ordinary linear differential equations of motion. The solution can be obtained through either direct integration or modal analysis. Particular emphasis is given on the rate of convergence of the solution. The cases of half-full cylinders and spheres are examined in detail, where explicit expressions for the coefficients of the governing equations are derived. Using the proposed methodology, sloshing frequencies and masses are calculated rigorously for arbitrary liquid height of horizontal-cylindrical or spherical containers, and the response under two characteristic seismic events is obtained. The results describe the linear dynamic response of such containers and can be used for an efficient seismic analysis and design of industrial pressure vessels.  相似文献   
367.
When intercepting a mobile object or an apparent movement, participants show a temporal bias i.e. they are in advance when dealing with a slow-moving stimulus and late with a fast-moving object. The authors studied 6 participants (aged 22–33 yrs) intercepting an apparent movement by sliding a disk on a table. Using a fast and a slow stimulus speed, 3 factors were varied: duration of presentation of the stimulus, distance covered by the stimulus, and speed context (constant or varied) of stimulus presentation. In addition to temporal bias, spatial accuracy and kinematic measures were collected. The temporal bias created by speed was evident across all 3 factors. Speed, in addition to strongly determining the temporal bias, significantly affected the throwing strategy adopted by the Ss as revealed by latency, movement time, and disk trajectory duration. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
368.
Unresectable liver tumors are often treated with interstitial probes that modify tissue temperature, and efficacious treatment relies on image guidance for tissue targeting and assessment. Here, we report the in vivo evaluation of an interstitial applicator with a mechanically oscillating five-element dual-mode transducer. After thoroughly characterizing the transducer, tissue response to high-intensity ultrasound was numerically calculated to select parameters for experimentation in vivo. Using perfused porcine liver, B-mode sector images were formed before and after a 120-s therapy period, and M-mode imaging monitored the therapy axis during therapy. The time-averaged transducer surface intensity was 21 or 27 W/cm$^2$. Electroacoustic conversion efficiency was maximally 72 $pm$ 3% and impulse response length was 295 $pm$ 1.0 ns at $-$6 dB. The depth of thermal damage measured by gross histology ranged from 10 to 25 mm for 13 insertion sites. For six sites, M-mode data exhibited a reduction in gray-scale intensity that was interpreted as the temporal variation of coagulation necrosis. Contrast ratio analysis indicated that the gray-scale intensity dropped by 7.8 $pm ;$3.3 dB, and estimated the final lesion depth to an accuracy of 2.3 $pm ;$2.4 mm. This paper verified that the applicator could induce coagulation necrosis in perfused liver and demonstrated the feasibility of real-time monitoring.   相似文献   
369.
The selection of the most suitable radio access technology to serve as the communication means for a service in a heterogeneous wireless access network is a complex task. It considers a number of different parameters and it involves numerous network technologies and entities. Several mechanisms have been proposed that focus on different aspects and follow different strategies. We introduce a policy based scheme that takes into consideration the user preferences, along with network conditions and user moving speed. Its ultimate goal is to support a session through the most desirable radio access technology, from the user perspective, while managing the overall network resources in an optimum way. It comprises a distributed algorithm running at the terminal and the network side. The performance of the proposed mechanism is evaluated against that of a typical load balancing scheme, commonly used in the literature. The results show that the holistic treatment of the diverse parameters fulfils the aforementioned goal.  相似文献   
370.
The aim of this experiment was to test the influence of target context on adaptation to scale perturbations introduced by a video display. Participants performed pointing movements without direct vision of their moving hand, although they could see their movements on a video display. Their perceived movements could be reduced, enlarged. or displayed at their actual size. Three target contexts were compared: dark surround, illuminated frame, and familiar object. Movements were executed with or without vision of hand displacement. Results showed that target context enhanced an allocentric coding of the movement, which improved movement execution. However, the effect of target context changed whether or not the displacement of the hand was available. Overall, the results suggest that target context allowed the extraction of dynamic information about movements, which is used to program and control movements. This suggests that target context could be used efficiently to improve spatial accuracy and speed in teleoperation learning. Potential applications include the reduction of difficulties encountered during teleoperation learning through the introduction of visual context.  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