首页 | 官方网站   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   3995篇
  免费   277篇
  国内免费   16篇
工业技术   4288篇
  2023年   58篇
  2022年   27篇
  2021年   124篇
  2020年   99篇
  2019年   113篇
  2018年   117篇
  2017年   139篇
  2016年   183篇
  2015年   122篇
  2014年   202篇
  2013年   281篇
  2012年   281篇
  2011年   342篇
  2010年   270篇
  2009年   217篇
  2008年   225篇
  2007年   198篇
  2006年   160篇
  2005年   139篇
  2004年   90篇
  2003年   102篇
  2002年   109篇
  2001年   87篇
  2000年   66篇
  1999年   64篇
  1998年   92篇
  1997年   45篇
  1996年   43篇
  1995年   32篇
  1994年   22篇
  1993年   27篇
  1992年   14篇
  1991年   12篇
  1990年   15篇
  1989年   24篇
  1988年   14篇
  1987年   16篇
  1986年   15篇
  1985年   14篇
  1984年   18篇
  1983年   13篇
  1982年   9篇
  1981年   5篇
  1980年   5篇
  1979年   4篇
  1978年   6篇
  1977年   5篇
  1976年   6篇
  1975年   7篇
  1974年   4篇
排序方式: 共有4288条查询结果,搜索用时 15 毫秒
991.
Esophagitis is divided into four grades according to the progress degree of disease by the LA classification method. This research was carried out on image processing with endoscope images for quantifying the four grades under the LA Classification. In a previous paper, which presented our work, the algorithm for detecting abnormal parts from one image was developed. This paper was conducted to classify esophagitis grade of one image itself. Whole 30 images were used in an experiment and included normal images and abnormal images with four grades. GLCM (gray level co-occurrence matrices) factors were extracted. The distributions of the texture image histogram were analyzed from each image for texture images. The algorithm to determine esophagitis grade used BPN (Back propagation network) that was composed of the texture histogram distribution for input data. It learned 20 images and verified with 10 images to diagnose under the LA classification system. Recognition ratio of learning result was 93.0% and verification result 77.0%. With features of the neural network, the success rate could be improved with this result by learning the data which were errors. Consequently, the recognition success rate appeared at 96% by total re-learned 30 images in addition to 10 images. This paper was recommended for publication in revised form by Associate Editor Dae-Eun Kim  相似文献   
992.
Spatial audio coding (SAC) is an extremely high compact representation of encoded multi‐channel audio material. This paper suggests a multi‐channel audio service in the terrestrial digital multimedia broadcasting (T‐DMB) system using a novel SAC tool, which is called a virtual source location information (VSLI)‐based SAC tool. Intensive experiments are presented to evaluate the validity of the proposed VSLI‐based SAC tool, and prototypical systems are also presented to demonstrate the reliability of the proposed multi‐channel T‐DMB system in real applications.  相似文献   
993.
We develop a simulation tool for an all-optical gain-clamped erbium-doped fiber amplifier (GC-EDFA) based on an amplified spontaneous emission (ASE) reflector and thoroughly verify its validity by comparing simulation data with experimental ones. We carry out simulation work as changing conditions like reflection ratio and bandwidth of the ASE reflector, EDF length, and pump power. From this work, we have an exact understanding about the gain clamping principle that a reflected ASE acts like an intensity reservoir against input signal intensity variation. In general, as a reflected ASE power becomes higher, both a dynamic range and a noise figure (NF) increase; on the other hand, a clamped gain value decreases. The ASE reflector-based gain clamping scheme can be used for EDFAs with low NF characteristics at small input signal range in case a reflected ASE power is set at a level much lower than powers required for normal gain clamping function.  相似文献   
994.
The integrated gasification combined cycle (IGCC) system is well known for its high efficiency compared with that of other coal fueled power generating systems. In this study, gasification using different types of burners with different oxygen supply angles in a bench-scale entrained flow gasifier was investigated. The effects of the oxygen gas supply angle of the coal burner and resulting oxygen supply location in the gasifier on the syngas composition and temperature of the gasifier were experimentally examined. These changes had a significant influence on the syngas composition of the final stream, carbon conversion, and efficiencies. According to the experimental results, the models using the Aspen Plus process simulator were positioned to define the effects of the experimental parameters and to find the optimum operating conditions in the bench gasifier facility.  相似文献   
995.
996.
Seo  D.-K. Kim  K.-T. Bae  J.-H. Kim  H.-T. 《Electronics letters》2001,37(18):1132-1133
In the area of radar signature modelling, subspace-based methods have recently become very popular. To model radar signals using subspace-based methods, spatial-smoothing preprocessing (SSP) is essential to estimate the covariance matrix of the received signals. Here, the performances of two typical SSP techniques are compared in the context of radar signature modelling  相似文献   
997.
Two 20-membered penta- and hexadentate macrocycles containing one or two pyridine subunits, namely [20]aneNO2S2 (L1) and [20]aneN2O2S2 (L2), have been synthesized. Reaction of L1 with silver(I) nitrate afforded a unique 2:2 (M:L) disilver(I) complex [μ2-Ag2(L1)2](NO3)2 (1) in which two four-coordinate Ag atoms bridge two ligands to form a cyclic dimer. In contrast, an endo-dentate 1:1 monosilver(I) complexes [AgL2]X; [X = ClO4 (2) or PF6 (3)] which show isomorphous structures were obtained from the reactions of L2 with silver(I) salts.  相似文献   
998.
To treat cutting oil wastewater produced in metal surface treatment industry, Ultrasonication (US)-Fenton process, which is one of the advanced oxidation processes, was used. The optimum conditions to treat non-biodegradable pollutants using the US-Fenton process were that the application rates of H2O2 and FeSO4 were 10% and 3 g/L, respectively, the value of pH was 3, and the ultrasonication time was 30 min. It identified non-degradable pollutants such as ethylene diamine tetraacetic acid (EDTA) and Triethanolamine (TEA) in the cutting oil wastewater. TLC analysis of two compounds of treated water by the coagulation process was similar to that of raw water. However, TLC analysis of two compounds of US-Fenton process was different from that of raw water, meaning that US-Fenton process decomposed the EDTA and TEA. To study the possibility of application with the US-Fenton process to pilot plant, the pollutants treatment efficiency of three different methods, such as US-Fenton process, activated sludge process and coagulation process, in continuous experiments were compared. The removal rate of pollutants by the US-Fenton process according to the effluent time was higher than any other processes. The removal rates of COD, SS, T-N and T-P by US-Fenton process were 98, 93, 75 and 95%, respectively.  相似文献   
999.
1000.
Collisions and grounding always give rise to structural crashworthiness issues involving crushing, yielding, and fracture. For accidental limit state design and safety assessment associated with collisions and grounding, the resulting progressive structural crashworthiness characteristics should be analyzed to evaluate the energy absorption capability of the structure in the corresponding accidental event in conjunction with the associated criteria. The accidental energy absorption capability of a structure under collisions or grounding can be predicted by integrating the area below the reaction forces versus penetration curve until or after the accidental limit state is reached. For risk assessment associated with such accidents, the results of structural crashworthiness analysis are also used as a basis of the consequence analysis. The aim of the present paper is to present an efficient and accurate method which is useful for the progressive structural crashworthiness analysis of ships and ship-shaped offshore structures under collisions or grounding. Theoretical outline of the method is addressed. Application examples of the method to ship-shaped test structures are presented by a comparison with experimental results.  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-23

京公网安备 11010802026262号