全文获取类型
收费全文 | 666198篇 |
免费 | 8454篇 |
国内免费 | 2257篇 |
专业分类
电工技术 | 11284篇 |
综合类 | 2777篇 |
化学工业 | 99827篇 |
金属工艺 | 27768篇 |
机械仪表 | 20777篇 |
建筑科学 | 16921篇 |
矿业工程 | 3509篇 |
能源动力 | 15945篇 |
轻工业 | 56503篇 |
水利工程 | 7119篇 |
石油天然气 | 9775篇 |
武器工业 | 35篇 |
无线电 | 80828篇 |
一般工业技术 | 130033篇 |
冶金工业 | 107320篇 |
原子能技术 | 11891篇 |
自动化技术 | 74597篇 |
出版年
2021年 | 4499篇 |
2019年 | 4216篇 |
2018年 | 20819篇 |
2017年 | 19913篇 |
2016年 | 17222篇 |
2015年 | 5941篇 |
2014年 | 9202篇 |
2013年 | 26720篇 |
2012年 | 17806篇 |
2011年 | 29292篇 |
2010年 | 23827篇 |
2009年 | 23453篇 |
2008年 | 25523篇 |
2007年 | 26719篇 |
2006年 | 17381篇 |
2005年 | 17113篇 |
2004年 | 16266篇 |
2003年 | 15949篇 |
2002年 | 14892篇 |
2001年 | 14732篇 |
2000年 | 13784篇 |
1999年 | 14175篇 |
1998年 | 32396篇 |
1997年 | 23480篇 |
1996年 | 18437篇 |
1995年 | 14358篇 |
1994年 | 12725篇 |
1993年 | 12587篇 |
1992年 | 9640篇 |
1991年 | 9290篇 |
1990年 | 8858篇 |
1989年 | 8580篇 |
1988年 | 8349篇 |
1987年 | 7113篇 |
1986年 | 7121篇 |
1985年 | 8476篇 |
1984年 | 7962篇 |
1983年 | 7082篇 |
1982年 | 6543篇 |
1981年 | 6468篇 |
1980年 | 6316篇 |
1979年 | 6216篇 |
1978年 | 5939篇 |
1977年 | 6824篇 |
1976年 | 8724篇 |
1975年 | 5139篇 |
1974年 | 4910篇 |
1973年 | 4904篇 |
1972年 | 4131篇 |
1971年 | 3647篇 |
排序方式: 共有10000条查询结果,搜索用时 21 毫秒
71.
In this paper, we describe a method for increasing the external efficiency of polymer light‐emitting diodes (LEDs) by coupling out waveguided light with Bragg gratings. We numerically model the waveguide modes in a typical LED structure and demonstrate how optimizing layer thicknesses and reducing waveguide absorption can enhance the grating outcoupling. The gratings were created by a soft‐lithography technique that minimizes changes to the conventional LED structure. Using one‐dimensional and two‐dimensional gratings, we were able to increase the forward‐directed emission by 47 % and 70 %, respectively, and the external quantum efficiency by 15 % and 25 %. 相似文献
72.
N. P. Mandal S. C. Agarwal 《Journal of Materials Science: Materials in Electronics》2003,14(10-12):797-798
Exposure to ammonia (NH3) increases the dark current (DC) in nanocrystalline silicon. Light soaking (LS) for short periods also enhances the dark current, which remains at a high value for a long time. Pumping alone is unable to restore the initial annealed state, but annealing brings it back. The final state obtained by LS and NH3 exposure depends on the order in which they are performed. Evaporated selenium (Se) deposited on nanocrystalline silicon decreases the DC. These effects cannot be explained entirely by the presence of a-Si : H alone, in our sample. DC and photoluminescence (PL) measurements indicate the presence of two types of center in our sample, which behave differently when exposed to NH3. 相似文献
73.
Malcolm J. Beynon 《国际智能系统杂志》2006,21(2):173-191
The granularity of an information system has an incumbent effect on the efficacy of the analysis from many machine learning algorithms. An information system contains a universe of objects characterized and categorized by condition and decision attributes. To manage the concomitant granularity, a level of continuous value discretization (CVD) is often undertaken. In the case of the rough set theory (RST) methodology for object classification, the granularity contributes to the grouping of objects into condition classes with the same condition attribute values. This article exposits the effect of a level of CVD on the subsequent condition classes constructed, with the introduction of the condition class space—the domain within which the condition classes exist. This domain elucidates the association of the condition classes to the related decision outcomes—reflecting the inexactness incumbent when a level of CVD is undertaken. A series of measures is defined that quantify this association. Throughout this study and without loss of generality, the findings are made through the RST methodology. This further offers a novel exposition of the relationship between all the condition attributes and the RST‐related reducts (subsets of condition attributes). © 2006 Wiley Periodicals, Inc. Int J Int Syst 21: 173–191, 2006. 相似文献
74.
Many organisations use decision models in their processes such as tables or trees to provide decision support to their operational
divisions. For example, in fault management, customer contact centre operators usually use a decision model in the form of
prescribed interviews. Based on the answers given by customers, the operator navigates through the decision model to reach
an assessment of the problem. In order to achieve customer satisfaction and operational excellence, it is very important to
constantly monitor the performance of a decision model not only on an overall level, but also on the level of individual decisions.
In this paper we present a configurable business process analytics tool, known as the intelligent Universal Service Management
System, that constantly monitors decision data and is capable of optimising the decisions based on high-level business objectives.
We explain the various features of the software and show how it can be used to optimise decision processes. We also show how
we can easily provide a customised version to monitor the performance of provision processes. 相似文献
75.
Learning in multiple model adaptive control switch 总被引:1,自引:0,他引:1
Including a learning mechanism in SMMAC (switched, multiple-model adaptive control) avoids the need for a priori knowledge of the model set of the plant to control and leads to a significant performance improvement with respect to the sole inclusion of an adaptive control channel in combination with switched fixed local controllers. 相似文献
76.
Interest in real-time model-based control is increasing as more and more facilities are being asked to meet stricter effluent requirements while at the same time minimizing costs. It has been identified that biological process models and automated process control technologies are being used at wastewater treatments plants throughout the world and that great potential for optimising biotreatment may exist with the integration of these two technology areas. According to our experience, wastewater treatment plants are indeed looking for ways to successfully integrate their modelling knowledge into their process control structure; however, there are practical aspects of this integration that must be addressed if the benefits of this integration are to be realised. This paper discusses the practical aspects of monitoring, filtering and analysing real sensor data with an aim to produce a reliable real-time data stream that might be used within a model-based control structure. Several real case study examples are briefly discussed in this paper. 相似文献
77.
The aim of this study was to evaluate the use of total coliforms (TC) and faecal coliforms (FC) using a membrane filtration method for precise monitoring of faecal pollution in Korean surface water. The samples were collected in Korea from both main rivers and their tributaries. Presumptive TC * FC were enumerated. The ratios of presumptive FC to TC were not constant, but varied widely, and TC were difficult to enumerate because of overgrowth by background colonies. For FC this was not the case. Seven hundred and three purified strains of presumptive TC * FC and their background colonies were biotyped using API 20E. Among 272 presumptive TC, non-faecal related species, Aeromonas hydrophila dominated (34.6%) and E. coli accounted for only 5.1%. In contrast, E. coli made up 89% of the 209 presumptive FC. Furthermore, of 164 background colonies on Endo Agar LES, 54.9% was A. hydrophila, while background colonies on m-FC Agar were few (58 strains), and despite their atypical colony appearance, most of them were biotyped as enteric bacteria. These results reveal that the detection of FC rather than TC using m-FC Agar is more appropriate for faecal pollution monitoring in eutrophicated surface water located in a temperate region. 相似文献
78.
A method of measuring and identifying the static parameters of a bipolar transistor is considered. The characteristic of the transistor, from which the parameters of the model are determined, is chosen depending on what group the calculated parameters belong to. The characteristics are measured in such a way that the equations of the model describing them can be reduced to the simplest form. 相似文献
79.
80.
M. N. Levin A. V. Tatarintsev V. A. Makarenko V. R. Gitlin 《Russian Microelectronics》2006,35(5):329-336
A model is formulated that describes how radiation-induced charge accumulates in the gate oxide of a MOS structure and how it decays through tunneling and thermal emission. The model is used in a numerical analysis of the x-ray or UV adjustment of threshold voltage in MOS-circuit manufacture. The limits of this process technique are evaluated. 相似文献