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   8603篇
  免费   602篇
  国内免费   253篇
电工技术   351篇
综合类   344篇
化学工业   1681篇
金属工艺   477篇
机械仪表   386篇
建筑科学   603篇
矿业工程   130篇
能源动力   381篇
轻工业   796篇
水利工程   97篇
石油天然气   261篇
武器工业   37篇
无线电   793篇
一般工业技术   1386篇
冶金工业   486篇
原子能技术   115篇
自动化技术   1134篇
  2024年   30篇
  2023年   117篇
  2022年   182篇
  2021年   319篇
  2020年   280篇
  2019年   252篇
  2018年   293篇
  2017年   305篇
  2016年   311篇
  2015年   261篇
  2014年   394篇
  2013年   714篇
  2012年   469篇
  2011年   559篇
  2010年   468篇
  2009年   483篇
  2008年   455篇
  2007年   443篇
  2006年   419篇
  2005年   343篇
  2004年   252篇
  2003年   232篇
  2002年   194篇
  2001年   194篇
  2000年   158篇
  1999年   198篇
  1998年   197篇
  1997年   140篇
  1996年   140篇
  1995年   111篇
  1994年   102篇
  1993年   84篇
  1992年   54篇
  1991年   53篇
  1990年   41篇
  1989年   39篇
  1988年   32篇
  1987年   19篇
  1986年   20篇
  1985年   13篇
  1984年   8篇
  1983年   9篇
  1982年   7篇
  1981年   8篇
  1979年   8篇
  1978年   6篇
  1976年   11篇
  1975年   8篇
  1972年   3篇
  1965年   3篇
排序方式: 共有9458条查询结果,搜索用时 250 毫秒
61.
Provision of automated support for planning protocol-directed therapy requires a computer program to take as input clinical data stored in an electronic patient-record system and to generate as output recommendations for therapeutic interventions and laboratory testing that are defined by applicable protocols. This paper presents a synthesis of research carried out at Stanford University to model the therapy-planning task and to demonstrate a component-based architecture for building protocol-based decision-support systems. We have constructed general-purpose software components that (1) interpret abstract protocol specifications to construct appropriate patient-specific treatment plans; (2) infer from time-stamped patient data higher-level, interval-based, abstract concepts; (3) perform time-oriented queries on a time-oriented patient database; and (4) allow acquisition and maintenance of protocol knowledge in a manner that facilitates efficient processing both by humans and by computers. We have implemented these components in a computer system known as EON. Each of the components has been developed, evaluated, and reported independently. We have evaluated the integration of the components as a composite architecture by implementing T-HELPER, a computer-based patient-record system that uses EON to offer advice regarding the management of patients who are following clinical trial protocols for AIDS or HIV infection. A test of the reuse of the software components in a different clinical domain demonstrated rapid development of a prototype application to support protocol-based care of patients who have breast cancer.  相似文献   
62.
A stability-indicating reversed-phase high performance liquid chromatographic method was developed for the detection of mitoxantrone HC1 and its degradation products under accelerated degradation conditions. The degradation kinetics of mitoxantrone HC1 in aqueous solution over a pH range of 1.18 to 7.20 and its stability in propylene glycol-or polyethylene glycol 400-based solutions were investigated. The observed rate constants were shown to follow apparent first-order kinetics in all cases. The pH-rate profile shows that maximum stability of mitoxantrone HC1 was obtained at pH 4.01. No general acid or base catalysis from acetate or phosphate buffer species was observed. The catalysis rate constants on the protonated mitoxantrone imposed by hydrogen ion water and hydroxy ion were determined to be 3.72 × 10 min-1 5.64 × 10-min-1 and 1.108 × 10-2min-1, respectively. The degradation rate constants of mitoxantrone affected by different ionic strength systems. Irradiation with 254 nm UV light at 25±0.5°C was found when canpared with the light-protected controls. Incorporation of nonaqueous propylene glycol or polyethylene glycol in the pH 4.01 mitoxantrone solution shows an increase in its stability at 502±0.5°C.  相似文献   
63.
AVO技术在寻找薄气层中的应用   总被引:3,自引:0,他引:3  
  相似文献   
64.
In this study, experimental and three-dimensional numerical studies were performed to investigate the effects of plate spacing and temperature difference on natural convection between isothermally heated upward-facing lower horizontal plate and externally insulated horizontal upper plate. Air is used as the heat transfer medium. Rayleigh number varied in the 1108–2.339 × 105 range. Several numerical simulations for three-dimensional steady laminar and turbulent flows heat transfer were carried out using a commercial CFD code Fluent 6.2. Results have shown that there is a good agreement between the numerical and present experimental results as well as with available data in literature.  相似文献   
65.
VCO非线性度检测是实现其非线性度精确校正的前提,研究VCO非线性度检测方法具有重要理论意义和实用价值。针对目前基于微元法和分数阶傅里叶变换的VCO非线性度检测方法在抗噪性、实时性等方面存在的不足,提出了一种基于重叠分段和分数阶傅里叶变换的VCO非线性度检测方法。所提方法采取重叠分段的策略以抑制噪声干扰,在分数阶傅里叶变换域进行幅度峰值搜索时改用收敛速度快的黄金分割法以增强实时性。仿真实验表明所提方法具有良好的抗噪性,分段重叠率为0.25时其检测的均方根误差约为现有方法的1/2;当重叠率小于2/3时,其实时性也优于现有方法。  相似文献   
66.
67.

Due to the budget and environmental issues, adaptive energy efficiency receives a lot of attention these days, especially for cloud computing. In the previous research, we developed a combined methodology based on nonparametric prediction and convex optimization to produce proactive energy efficiency-oriented solution. In this work, the predictive analysis was further enhanced by deriving the mixture power spectral density to model the complex cloud monitoring statistics. By engaging the improved technique to the predictive analysis, the prediction process was more adaptive to handle the fluctuation in system utilization. As a consequence, the optimization process could subsequently produce more appropriate setting for energy savings. After the infrastructure setting has been made available, the instruction of virtual machine migration was created and implemented by the cloud orchestrator. This instruction condensed the services into the pool of active facilities, satisfying the objective of power efficiency. Eventually, any physical machine out of the power configuration would be gradually terminated. Compared to our former method, the effectiveness of the proposed technique has been proven by cutting down 4.92% of energy consumption, while still maintaining a similar quality of services.

  相似文献   
68.
Neural Computing and Applications - Renewable energy sources are installed into both distribution and transmission grids more and more with the introduction of smart grid concept. Hence, efficient...  相似文献   
69.
Advances in information technology (IT) have forced financial services firms to explore new organizational forms and deliver service innovation. Given the obvious differences in the business model in which the financial services sector provides online services, it is natural to ask whether the emergence of Internet channels leads to superior achievement. Using a sample of twenty-four Taiwanese publicly traded financial services firms from 1997 to 2003, this empirical study attempts to assess the Internet channel??s effect on firm performance by means of applying event study methodology and data envelopment analysis. Results show that the magnitudes of average abnormal returns are uniformly positive and increase the operating efficiency of firms following announcements via Internet channels. This work therefore concludes that Internet channels have positive influences on firm performance.  相似文献   
70.
Conventional constant false alarm rate (CFAR) methods use a fixed number of cells to estimate the background variance. For homogeneous environments, it is desirable to increase the number of cells, at the cost of increased computation and memory requirements, in order to improve the estimation performance. For nonhomogeneous environments, it is desirable to use less number of cells in order to reduce the number of false alarms around the clutter edges. In this work, we present a solution with two exponential smoothers (first order IIR filters) having different time-constants to leverage the conflicting requirements of homogeneous and nonhomogeneous environments. The system is designed to use the filter having the large time-constant in homogeneous environments and to promptly switch to the filter having the small time constant once a clutter edge is encountered. The main advantages of proposed Switching IIR CFAR method are computational simplicity, small memory requirement (in comparison to windowing based methods) and its good performance in homogeneous environments (due to the large time-constant smoother) and rapid adaptation to clutter edges (due to the small time-constant smoother).  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