全文获取类型
收费全文 | 128586篇 |
免费 | 3639篇 |
国内免费 | 452篇 |
专业分类
电工技术 | 1073篇 |
综合类 | 2361篇 |
化学工业 | 19986篇 |
金属工艺 | 5643篇 |
机械仪表 | 3930篇 |
建筑科学 | 3627篇 |
矿业工程 | 645篇 |
能源动力 | 2128篇 |
轻工业 | 9533篇 |
水利工程 | 1626篇 |
石油天然气 | 536篇 |
武器工业 | 6篇 |
无线电 | 11690篇 |
一般工业技术 | 23982篇 |
冶金工业 | 14661篇 |
原子能技术 | 529篇 |
自动化技术 | 30721篇 |
出版年
2023年 | 395篇 |
2022年 | 470篇 |
2021年 | 1102篇 |
2020年 | 888篇 |
2019年 | 837篇 |
2018年 | 15645篇 |
2017年 | 14607篇 |
2016年 | 11314篇 |
2015年 | 1857篇 |
2014年 | 1868篇 |
2013年 | 3432篇 |
2012年 | 5777篇 |
2011年 | 11693篇 |
2010年 | 10056篇 |
2009年 | 7203篇 |
2008年 | 8628篇 |
2007年 | 9288篇 |
2006年 | 1527篇 |
2005年 | 2387篇 |
2004年 | 2204篇 |
2003年 | 2126篇 |
2002年 | 1397篇 |
2001年 | 676篇 |
2000年 | 760篇 |
1999年 | 759篇 |
1998年 | 3942篇 |
1997年 | 2382篇 |
1996年 | 1562篇 |
1995年 | 903篇 |
1994年 | 794篇 |
1993年 | 786篇 |
1992年 | 260篇 |
1991年 | 293篇 |
1990年 | 256篇 |
1989年 | 261篇 |
1988年 | 243篇 |
1987年 | 203篇 |
1986年 | 209篇 |
1985年 | 257篇 |
1984年 | 213篇 |
1983年 | 158篇 |
1982年 | 202篇 |
1981年 | 214篇 |
1980年 | 185篇 |
1979年 | 148篇 |
1978年 | 147篇 |
1977年 | 237篇 |
1976年 | 475篇 |
1975年 | 106篇 |
1973年 | 99篇 |
排序方式: 共有10000条查询结果,搜索用时 968 毫秒
921.
This paper presents texture segmentation realised with image treatment methods and an artificial neural network model. Gabor oriented filters are used to extract frequential texture features and Self-Organising Feature Maps are used to group and interpolate these features. In order to decrease the number of filters, we use a pyramidal multiresolution method of image representation. We intend to build an architecture inspired by the early stages of the visual cortex, while making local frequential analysis of the images, which must be able to segment different textured images. 相似文献
922.
Dr. P. Bošnjakovié Dipl.-Ing. B. Djokié 《Electrical Engineering (Archiv fur Elektrotechnik)》1992,75(2):131-135
Contents This paper analyzes a problem of phase shifting and deseribes a novel method for electronic reactive energy measurement. The proposed measurement structure, composed of an integrator as a phase shifting circuit and a frequency controlled analog-to-pulse-rate converter, provides for the measurement completely in accordance with IEC definition of reactive energy, which is performed with simple but high performance metering device.
Die Blindverbrauchsmessung anhand eines netzsynchronisierten Analog-Frequenz-Wandlers
Übersicht In diesem Artikel wird das Problem der Phasenverschiebung analysiert und eine neue Meßmethode für elektronische Blindverbrauschsmessung aufgezeigt. Die vorgeschlagene Strucktur, bestehend aus einem Integrator als Phasenschieber und netzkontrolliertem Analog-Frequenz-Wandler, ermöglicht die Verwirklichung eines einfachen aber präzisen Elektrizitätszählers zur Messung der Blindenergie, dessen Arbeitsprinzip mit den IEC Empfehlungen vollkommen übereinstimmt.相似文献
923.
F Balagué P Damidot M Nordin M Parnianpour M Waldburger 《Canadian Metallurgical Quarterly》1993,18(9):1199-1205
Our surveys have shown lifetime prevalence of L.BP. over 30% among schoolchildren. The purpose of this study was to evaluate the relationship between back and isokinetic trunk strength, anthropometric parameters, and sports activities. One hundred and seventeen healthy children aged 10-16 years were included. All these volunteers had semi-structured interview, anthropometric and dynamic strength measurements. Lifetime prevalence of back pain was 44.5% and point prevalence was 13%. In this cross-sectional study, anthropometric and strength profiles were significantly related to age and gender. Non specific low back pain was not correlated to trunk muscle strength and/or sports activities. 相似文献
924.
925.
Y Clément JM Launay D Bondoux P Venault B Martin J Young P Robel G Chapouthier 《Canadian Metallurgical Quarterly》1996,110(1):28-35
It is believed that DOPA-negative melanocytes in the outer root sheath of the human hair follicle are activated, become identifiable by DOPA staining, and migrate into the epidermis during the repigmenting phase of vitiligo. These cells are difficult to identify, however, and otherwise have not been characterized. These cells are readily identified by immunofluorescence, immunohistochemistry, and immunoelectronmicroscopy using the antibodies NKI/beteb and A4F11, which recognize premelanosome-related antigens. The majority of the outer root sheath melanocytes were found in the mid to the upper portion of the hair follicle. Double staining revealed that these cells were distinct from HLA-DR-bearing dendritic cells. Further immunohistochemical investigation using alpha-PEP-7, alpha-PEP-1, or TMH-1 and alpha-PEP-8 antibodies revealed that outer root sheath melanocytes cannot be identified by antibodies to tyrosinase, TRP-1, or TRP-2, respectively. These cells also did not react with HMB45 antibody, which recognizes a melanosome-associated cytoplasmic antigen. We believe that the inactive outer root sheath melanocytes contain some of the early structural proteins but not any of the enzymatic proteins necessary for melanogenesis. Therefore, activation is the process whereby outer root sheath melanocytes acquire all of the structural and enzymatic proteins necessary for melanogenesis. 相似文献
926.
J González de Dios M Moya Benavent MC Sirvent Mayor T Durá Travé 《Canadian Metallurgical Quarterly》1996,45(4):403-408
Cytomegalovirus is the main agent of congenital viral infections. The aim of this study was to compare the incidence of congenital cytomegalovirus infections of two groups of newborns of differing socioeconomic status. Cytomegalovirus was isolated from urine or oropharingeal secretions in 218 children born in a private clinic and 471 born in a public hospital. Positive viral isolates were confirmed with indirect immunofluorescence using monoclonal antibodies. Infection was detected in 12 children (1.82%), four coming from the private clinic (1.86%) and 8 coming from the public hospital (1.81%). Ninety two percent of infected children were asymptomatic. Urine and oropharingeal secretion samples had the same yield for viral isolation. It is concluded that the incidence of congenital cytomegalovirus infection is similar to that described in developed countries. 相似文献
927.
928.
Zheng Liu Zhiyun Xue Rick S. Blum Robert Laganière 《Pattern Analysis & Applications》2006,8(4):375-389
Images acquired by heterogeneous image sensors may provide complementary information about the scene, for instance, the visual image can provide personal identification information like the facial pattern while the infrared (IR) or millimeter wave image can detect the suspicious regions of concealed weapons. Usually, a technique, namely multiresolution pixel-level image fusion is applied to integrate the information from multi-sensor images. However, when the images are significantly different, the performance of the multiresolution fusion algorithms is not always satisfactory. In this study, a new strategy consisting of two steps is proposed. The first step is to use an unsupervised fuzzy k-means clustering to detect the concealed weapon from the IR image. The detected region is embedded in the visual image in the second step and this process is implemented with a multiresolution mosaic technique. Therefore, the synthesized image retains the quality comparable to the visual image while the region of the concealed weapon is highlighted and enhanced. The experimental results indicate the efficiency of the proposed approach.This material is based on part of the work carried out at the SPCR laboratory of Lehigh University and the work is partially supported by the U. S. Army Research Office under grant number DAAD19-00-1-0431. The content of the information does not necessarily reflect the position or the policy of the federal government, and no official endorsement should be inferred. 相似文献
929.
930.
In this article, a new extension of affine arithmetic is introduced. This technique is based on a quadratic form named general quadratic form. We focus here on the computation of reliable bounds of a function over a hypercube by using this new tool. Some properties
of first quadratic functions and then polynomial ones are reported. In order to show the efficiency of such a method, ten
polynomial global optimization problems are presented and solved by using an interval branch-and-bound based algorithm.
The work of the first author was also supported by the Laboratoire de Mathématiques Appliquées CNRS–FRE 2570, Université de
Pau et des Pays de l'Adour, France, and by the Laboratoire d'Electrotechnique et d'Electronique Industrielle CNRS–UMR5828,
Group EM3, INPT–ENSEEIHT. 相似文献