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   351篇
  免费   19篇
电工技术   5篇
化学工业   76篇
金属工艺   4篇
机械仪表   8篇
建筑科学   14篇
能源动力   5篇
轻工业   39篇
无线电   35篇
一般工业技术   74篇
冶金工业   71篇
原子能技术   3篇
自动化技术   36篇
  2023年   10篇
  2022年   12篇
  2021年   24篇
  2020年   14篇
  2019年   8篇
  2018年   12篇
  2017年   14篇
  2016年   9篇
  2015年   15篇
  2014年   15篇
  2013年   15篇
  2012年   14篇
  2011年   28篇
  2010年   13篇
  2009年   12篇
  2008年   10篇
  2007年   10篇
  2006年   7篇
  2005年   8篇
  2004年   3篇
  2003年   3篇
  2001年   2篇
  2000年   5篇
  1999年   6篇
  1998年   22篇
  1997年   9篇
  1996年   12篇
  1995年   5篇
  1994年   11篇
  1993年   6篇
  1992年   4篇
  1991年   2篇
  1989年   1篇
  1988年   1篇
  1986年   1篇
  1985年   3篇
  1984年   3篇
  1983年   2篇
  1981年   1篇
  1980年   1篇
  1978年   2篇
  1977年   1篇
  1976年   2篇
  1975年   1篇
  1974年   1篇
  1973年   2篇
  1971年   2篇
  1962年   1篇
  1959年   1篇
  1939年   1篇
排序方式: 共有370条查询结果,搜索用时 15 毫秒
101.
OBJECTIVES: The purpose of this study was to determine how risks associated with increasing age differed in patients treated with percutaneous transluminal coronary angioplasty versus thrombolysis. BACKGROUND: Advancing age is a risk factor for adverse outcome in patients with acute myocardial infarction. Primary angioplasty has been thought to be particularly beneficial in higher risk patients including the elderly. There is, however, limited data on any differential incremental benefit of angioplasty compared with thrombolysis in candidates for either treatment. METHODS: In the GUSTO-IIb angioplasty substudy, 1,138 patients were randomized to receive primary angioplasty or accelerated tissue-type plasminogen activator (t-PA). The effect of age on outcome was assessed as a discrete and continuous variable for each treatment group. Models using age as a linear factor as well as cubic spline transformations were used for the major end points of 30-day death or disabling stroke; death or reinfarction; and death, reinfarction or disabling stroke. RESULTS: For each 10-year patient group, outcome was improved with angioplasty (n = 565) compared with t-PA (n = 573). Irrespective of treatment, however, risk increased with age. After adjusting for baseline characteristics, each increment of 10 years of age increased the risk of death or myocardial infarction by 1.32 (95% confidence interval 1.04 to 1.76, p = 0.022). For all adverse outcomes, this incremental effect of increasing age was constant. CONCLUSIONS: Advancing age is associated with worse outcomes, and the risks increase in proportion to age. Although primary angioplasty improves outcomes over thrombolysis, it does not appear to be more beneficial in older than in younger patient groups. The incremental adverse effect of age does not vary by treatment strategy.  相似文献   
102.
Liver metastases are the most common site of metastatic spread in colorectal cancer. Current treatment approaches involve effective systemic therapies in combination with surgical and/or interventional strategies. Multimodal strategies greatly improved clinical outcomes of patients with metastatic colorectal cancer over the last decades. Identification of predictive and prognostic biomarkers helped to comprehensively refine individual targeted treatment approaches and resulted in median overall survival rates of 30 months or longer. Current guidelines, thus, recommend treatment selection according to patients’ performance status, tumor localization and stage as well as the tumor’s molecular and genetic status. Here, we outline the latest developments in molecular decision-making for patients with upfront resectable, potentially or initially unresectable and non/never-resectable colorectal cancer liver metastases.  相似文献   
103.
104.
The knowledge of the accurate laser tool position is of extreme importance for quality assurance during the laser beam welding. Already minimum deviations of the desired track can impair the result of the manufacturing process, e.g. due to tolerances of thermal deformation. A contribution of this problem is an optical sensor system, which detects the three-dimensional position of the weldseam in on-line coupling parallel to the welding process and then derives the actual laser beam position relative to the workpiece. Under laboratory conditions the function of the sensor system for the on-line tracking of the laser tool was tested successfully in connection with a handling system.  相似文献   
105.
In two-dimensional echocardiography the sonographer must synthesize multiple tomographic slices into a mental three-dimensional (3D) model of the heart. Computer graphics and virtual reality environments are ideal to visualize complex 3D spatial relationships. In augmented reality (AR) applications, real and virtual image data are linked, to increase the information content. In the presented AR simulator a 3D surface model of the human heart is linked with echocardiographic volume data sets. The 3D echocardiographic data sets are registered with the heart model to establish spatial and temporal congruence. The heart model, together with an animated ultrasound sector represents a reference scenario, which displays the currently selected two-dimensional echocardiographic cutting plane calculated from the volume data set. Modifications of the cutting plane within the echocardiographic data are transferred and visualized simultaneously and in real time within the reference scenario. The trainee can interactively explore the 3D heart model and the registered 3D echocardiographic data sets by an animated ultrasound probe, whose position is controlled by an electromagnetic tracking system. The tracking system is attached to a dummy transducer and placed on a plastic puppet to give a realistic impression of a two-dimensional echocardiographic examination.  相似文献   
106.
C. Regier  J. Pieper 《低温学》2010,50(2):118-125
This work includes the creation and validation of a computer model of a liquid helium cryostat located at the Canadian Light Source (CLS) in Saskatoon, Canada. This cryostat contains a superconducting radio frequency (RF) cavity, and requires careful pressure and level modulation to ensure proper RF control. A detailed mathematical model of the cryostat is generated based on gas and liquid mass balances for a boiling vessel, along with pressure-volume-temperature relations. The model is discretized and solved, and model results are compared with experimental data taken from the actual cryostat at the CLS to determine the accuracy of the simulation. The model is found to reasonably represent the cryostat at the CLS from a process perspective.  相似文献   
107.
By means of plasma polymerization, positively charged, nanometre-thin coatings can be applied to implant surfaces. The aim of the present study was to quantify the adhesion of human bone cells in vitro and to evaluate the bone ongrowth in vivo, on titanium surfaces modified by plasma polymer coatings. Different implant surface configurations were examined: titanium alloy (Ti6Al4V) coated with plasma-polymerized allylamine (PPAAm) and plasma-polymerized ethylenediamine (PPEDA) versus uncoated. Shear stress on human osteoblast-like MG-63 cells was investigated in vitro using a spinning disc device. Furthermore, bone-to-implant contact (BIC) was evaluated in vivo. Custom-made conical titanium implants were inserted at the medial tibia of female Sprague-Dawley rats. After a follow-up of six weeks, the BIC was determined by means of histomorphometry. The quantification of cell adhesion showed a significantly higher shear stress for MG-63 cells on PPAAm and PPEDA compared to uncoated Ti6Al4V. Uncoated titanium alloyed implants showed the lowest BIC (40.4%). Implants with PPAAm coating revealed a clear but not significant increase of the BIC (58.5%) and implants with PPEDA a significantly increased BIC (63.7%). In conclusion, plasma polymer coatings demonstrate enhanced cell adhesion and bone ongrowth compared to uncoated titanium surfaces.  相似文献   
108.
Tetrahedral DNA hybrids with tetrakis(p‐hydroxyphenyl)methane cores hybridize in a sequence‐specific fashion at much higher temperatures than isolated linear duplexes. Dinucleotide DNA arms suffice to induce the formation of a solid at room temperature; this demonstrates the strength of multivalent binding. The graphic shows a view of a modeled assembly.

  相似文献   

109.
In this paper we present both finite element based and analytic model simulations of pentacene based organic thin film transistor. The finite element type simulation is done using Silvaco’s Atlas simulator and the analytic model simulation is performed using a Matlab code based on the standard transistor equations. Both the Atlas and Matlab simulations agree approximately with the published experimental result. The results of the simulations show a current ratio of 2.11×106 for Atlas and 1.8×107 for Matlab simulations. The threshold voltage extracted from the finite element type simulation is 1.1 V which is in good agreement with 1.2 V used for Matlab simulation. However, the contact resistance shows a quite significant variation between the two simulation mechanisms. The finite element type simulation gives a contact resistance of 10 kΩ whereas the Matlab simulation predicts a contact resistance 1.9 kΩ.  相似文献   
110.
Social Networks provide one of the most rapidly evolving data sets in existence today. Traditional Business Intelligence applications struggle to take advantage of such data sets in a timely manner. The BBC SoundIndex, developed by the authors and others, enabled real-time analytics of music popularity using data from a variety of Social Networks. We present this system as a grounding example of how to overcome the challenges of working with this data from social networks. We discuss a variety of technologies to implement near real-time data analytics to transform Social Intelligence into Business Intelligence and evaluate their effectiveness in the music domain. The SoundIndex project helped to highlight a number of key research areas, including named entity recognition and sentiment analysis in Informal English. It also drew attention to the importance of metadata aggregation in multimodal environments. We explored challenges such as drawing data from a wide set of sources spanning a myriad of modalities, developing adjudication techniques to harmonize inputs, and performing deep analytics on extremely challenging Informal English snippets. Ultimately, we seek to provide guidance on developing applications in a variety of domains that allow an analyst to rapidly grasp the evolution in the social landscape, and show how to validate such a system for a real-world application.  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