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   3674篇
  免费   97篇
  国内免费   61篇
电工技术   76篇
综合类   136篇
化学工业   364篇
金属工艺   84篇
机械仪表   80篇
建筑科学   75篇
矿业工程   19篇
能源动力   43篇
轻工业   158篇
水利工程   27篇
石油天然气   16篇
武器工业   4篇
无线电   204篇
一般工业技术   323篇
冶金工业   1970篇
原子能技术   24篇
自动化技术   229篇
  2022年   37篇
  2021年   43篇
  2020年   48篇
  2019年   27篇
  2018年   23篇
  2017年   31篇
  2016年   33篇
  2015年   33篇
  2014年   63篇
  2013年   93篇
  2012年   94篇
  2011年   95篇
  2010年   102篇
  2009年   96篇
  2008年   118篇
  2007年   113篇
  2006年   97篇
  2005年   77篇
  2004年   62篇
  2003年   63篇
  2002年   51篇
  2001年   63篇
  2000年   39篇
  1999年   69篇
  1998年   578篇
  1997年   361篇
  1996年   205篇
  1995年   119篇
  1994年   103篇
  1993年   123篇
  1992年   30篇
  1991年   20篇
  1990年   29篇
  1989年   18篇
  1988年   29篇
  1987年   22篇
  1985年   20篇
  1984年   20篇
  1983年   20篇
  1982年   25篇
  1981年   33篇
  1980年   33篇
  1979年   18篇
  1978年   25篇
  1977年   72篇
  1976年   160篇
  1975年   18篇
  1973年   19篇
  1971年   17篇
  1970年   18篇
排序方式: 共有3832条查询结果,搜索用时 31 毫秒
101.
This study examined trainee crime-scene investigators' preference for, and accuracy in using, four different computer-based decision support interface designs, each of which incorporated a different reduced processing information acquisition strategy. The interfaces differed on the basis of the number of options that could be considered simultaneously and the level of control that could be exercised over the number and sequence in which feature values were accessed. Forty trainee investigators completed six decision scenarios in which they were asked to acquire information and formulate a decision by selecting one of three options. The study comprised two phases, the first of which involved familiarizing participants with each of the four interface designs and collecting performance and subjective data. The second phase involved trainees selecting one of the four interfaces to engage in a fifth and sixth decision scenario involving high or low levels of time-pressure. The results indicated that the “all options, full control” interface was the preferred option in the low time-pressure condition. Although the strategy remained the most frequently selected in the high time-pressure condition, this preference was not significant. It was concluded that the perceptions of difficulty and the degree of user control over information acquisition were more important than perceived efficiency in the selection of computer-based interface designs. The outcomes have implications for the design of decision support systems.  相似文献   
102.
This pilot study examines the use of Camtasia-enhanced lessons to supplement distance education provided to medical laboratory science students. More programs of study are available as distance learning opportunities, creating challenges to find better ways to present material. Librarians provided technical expertise necessary to produce a Camtasia video. This helped instructors prepare engaging lectures for phlebotomy to supplement the PowerPoint presentations and self-directed lessons provided in previous courses. Medical laboratory science faculty collaborated with library staff to produce videos that demonstrate proper phlebotomy technique using training personnel and faculty, whom the students eventually interact with in the clinical environment.  相似文献   
103.
基于TM影像的典型内陆淡水湿地水体提取研究   总被引:11,自引:1,他引:10  
水是维系湿地生态系统稳定和健康的决定性因子,利用卫星遥感影像快速、准确地提取湿地水体信息已经成为湿地调查、研究与保护的重要手段。鉴于TM遥感影像具有较高的空间分辨率、波谱分辨率、极为丰富的信息量、较高的定位精度和相对较低的价格,其必然成为近一段时期湿地调查、研究与保护的重要数据源之一。研究基于TM遥感影像,运用多种方法针对典型内陆淡水湿地的水体信息进行了提取实验,通过对实验结果的分析得出:在面积的准确性、提取的准确度以及视觉效果3种指标下,光谱分类法较其它方法效果要好,其次为单波段阈值分析法与植被指数法,较差的是多波段谱间关系法与水体指数法;影响提取效果的主要原因是湿地水体提取不够完全,这是由影像的分辨率及湿地特殊的水文条件所造成的,采用像元分解及多源遥感数据融合技术将成为提高水体提取精度的重要手段。  相似文献   
104.
BACKGROUND: In 1992, 12 large children's hospitals established the Benchmarking Effort for Networking Children's Hospitals (BENCHmark). The goal was for the BENCHmark effort to supplement the hospitals' continuous quality improvement (CQI) programs and to speed adoption of best practices from peer institutions. For three years, the hospitals have been comparing data on cost, quality, and speed indicators. Also, "best practice" groups have met to share information on how processes can be improved. RESULTS: The BENCHmark hospitals have experienced significant process improvement in areas such as emergency department waiting time and admitting process time. EXAMPLE: The BENCHmark hospitals selected admitting as one of the first best practice groups to meet. Interdisciplinary staff from all BENCHmark hospitals met three times over the course of a year to define their indicator and share information on best practices. St Louis Children's Hospital, as a result, instituted a pre-arrival team and cross-trained staff, with the result being a reduction of admitting processing time from 58 minutes to 19 minutes. Same-day surgery patients now bypass the admitting department and go directly to the surgical floor. Patient and surgeon satisfaction has increased greatly. CONCLUSIONS: Hospitals that are planning to benchmark are encouraged to reach consensus on project goals and to focus on indicators that provide a clear business advantage. Physician involvement is key to improving performance and physicians will only be engaged if the hospitals against whom they are benchmarked are considered peers. Being willing to share initial data openly seems to be a key factor in determining successful integration of the BENCHmark process into hospital CQI efforts. The BENCHmark project has been so successful that a second group of 12 comparable pediatric institutions, known as the Network II, has been established.  相似文献   
105.
RATIONALE AND OBJECTIVES: Traditionally, multireader receiver operating characteristic (ROC) studies have used a "paired-case, paired-reader" design. The statistical power of such a design for inferences about the relative accuracies of the tests was assessed and compared with alternative designs. METHODS: The noncentrality parameter of an F statistic was used to compute power as a function of the reader and patient sample sizes and the variability and correlation between readings. RESULTS: For a fixed-power and Type I error rate, the traditional design reduces the number of verified cases required. A hybrid design, in which each reader interprets a different sample of patients, reduces the number of readers, total readings, and reading required per reader. The drawback is a substantial increase in the number of verified cases. CONCLUSION: The ultimate choice of study design depends on the nature of the tests being compared, limiting resources, a priori knowledge of the magnitude of the correlations and variability and logistic complexity.  相似文献   
106.
OBJECTIVE: To assess how members of different specialties vary in their decisions about which form of life support to withdraw. The hypothesis was that each specialty would be more comfortable withdrawing its "own" form of life support relative to other forms and other specialties. DESIGN: Mail survey. SETTING: 24 medical centers. PARTICIPANTS: 225 specialists in six specialties and 225 comparison physicians randomly matched according to percentage of time devoted to clinical practice. MEASUREMENTS: The six specialties were linked with six life-sustaining technologies related to their special expertise: 1) pulmonologists with mechanical ventilation, 2) nephrologists with hemodialysis, 3) gastroenterologists with tube feedings, 4) hematologists with blood products, 5) cardiologists with intravenous vasopressors, and 6) infectious disease specialists with antibiotics. The subjects ranked different forms of life support in the order in which they would prefer to withdraw them. They also expressed their preferences in response to hypothetical clinical vignettes. RESULTS: In five of the six specialties, the specialists had a relative preference for withdrawing their "own" form of life support, compared with the preferences of the comparison physicians. Overall, the physicians tended to prefer withdrawing a form of life support closely linked with their own specialty. CONCLUSIONS: Just as some specialist physicians tend to reach for different technologies first in treating patients, they also tend to reach for different technologies first when ceasing treatment. Specialists' preferences for different ways to withdraw life support not only may reflect a special understanding of the limits of certain technologies, but also may reveal how ingrained are physicians' patterns of practice.  相似文献   
107.
为了提高回声状态网络对于混沌时间序列特征提取与预测的能力,提出一种层次化可塑性回声状态网络模型.该模型将多个储备池顺序连接,通过逐层特征变换的方式增强对非线性多尺度动态特征的提取能力.同时,引入神经科学中的内在可塑性机制模拟真实生物神经元的放电率分布,以最大化神经元的信息传递为目标对储备池进行预训练.层次化可塑性回声状态网络不仅能够增加模型的容量,降低随机投影所带来的不稳定性,而且也为理解储备池的表示、处理、记忆及储存操作提供一种新的思路.仿真实验结果表明,相比于其他7种改进的回声状态网络模型,所提出的模型在人造数据和真实数据所构成的混沌时间序列预测任务中均能取得最优的预测精度.  相似文献   
108.
“互联网+”背景下厨房系统的设计服务模式   总被引:2,自引:2,他引:0  
吴志军  那成爱 《包装工程》2016,37(8):12-15,23
目的构建"互联网+"背景下厨房系统的设计服务模式。方法在分析"互联网+"内涵的基础上,比较传统"微笑曲线"模式和"互联网+制造业"模式下工业设计切入模式的差异,构建"互联网+"背景下整体厨房云设计服务系统的功能目标、服务流程和生长模式。结论在"互联网+"背景下,厨房系统不仅实现了开放协同的定制设计,而且还实现了从产品形象一致性到用户体验一致性的设计转型,有助于快速创新和解决产能过剩问题。  相似文献   
109.
袁野  纳薇  王华  高文桂 《材料导报》2016,30(24):25-31
用直接合成法制备了不同铝硅物质的量比Al-SBA-15(β)(β=n(Al)/n(Si)=0,0.02,0.03,0.05)介孔分子筛,并采用浸渍法制备了金属负载量m=35%的CZZ/Al-SBA-15(β)负载型介孔催化剂,考察了Al/Si比对负载催化剂结构和性能的影响。采用N_2吸附-脱附、X射线衍射(XRD)、H_2程序升温还原(H_2-TPR)、CO_2吸附(CO_2-TPD)、NH3吸附(NH3-TPD)和透射电子显微镜(TEM)等手段对样品进行了表征,在固定床反应器上评价了其CO_2加氢合成甲醇的催化性能。实验结果表明,CZZ/Al-SBA-15(β)具有介孔结构,Al的引入不但增加了载体表面酸性位点,同时还提高了催化剂表面铜分散度(DCu%)和铜比表面积(SCu)以及促进了Cu~+-O-Zn活性位的形成,从而大大提高了催化剂的活性。其中CZZ/Al-SBA-15(0.03)催化剂的甲醇选择性达到26%,与不掺铝的CZZ/Al-SBA-15(0)催化剂相比,甲醇选择性提高了11%,但随着掺Al量的继续增加,酸性太强,CO_2吸附能力下降,活性反而降低。  相似文献   
110.
近年来,苯系物等类油物质泄漏事故频发。由于苯系物多数具有极强的毒性和挥发性,因此苯系物比原油等重油泄漏事故引发的危害更大。考虑到苯系物和油类物质理化性质的相似性,对苯系物泄漏事故的应急处置办法可以参考溢油事故的处置办法。通过对溢油事故中常用的无机类吸附材料、有机高分子吸附材料和天然高分子吸附材料的研究现状和应用前景进行了综述,希望能够为相关科研工作者解决苯系物泄漏的应急处置提供思路,促进该领域的快速发展。  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