全文获取类型
收费全文 | 2939篇 |
免费 | 181篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 86篇 |
综合类 | 4篇 |
化学工业 | 711篇 |
金属工艺 | 61篇 |
机械仪表 | 98篇 |
建筑科学 | 101篇 |
矿业工程 | 8篇 |
能源动力 | 121篇 |
轻工业 | 490篇 |
水利工程 | 14篇 |
石油天然气 | 13篇 |
无线电 | 178篇 |
一般工业技术 | 764篇 |
冶金工业 | 24篇 |
原子能技术 | 9篇 |
自动化技术 | 439篇 |
出版年
2023年 | 21篇 |
2022年 | 12篇 |
2021年 | 61篇 |
2020年 | 56篇 |
2019年 | 66篇 |
2018年 | 115篇 |
2017年 | 111篇 |
2016年 | 139篇 |
2015年 | 100篇 |
2014年 | 144篇 |
2013年 | 326篇 |
2012年 | 207篇 |
2011年 | 216篇 |
2010年 | 180篇 |
2009年 | 127篇 |
2008年 | 136篇 |
2007年 | 120篇 |
2006年 | 95篇 |
2005年 | 55篇 |
2004年 | 32篇 |
2003年 | 48篇 |
2002年 | 38篇 |
2001年 | 31篇 |
2000年 | 36篇 |
1999年 | 30篇 |
1998年 | 21篇 |
1997年 | 15篇 |
1996年 | 26篇 |
1995年 | 20篇 |
1994年 | 29篇 |
1993年 | 23篇 |
1992年 | 23篇 |
1991年 | 20篇 |
1990年 | 20篇 |
1989年 | 17篇 |
1988年 | 13篇 |
1985年 | 32篇 |
1984年 | 34篇 |
1983年 | 28篇 |
1982年 | 24篇 |
1981年 | 36篇 |
1980年 | 32篇 |
1979年 | 25篇 |
1978年 | 24篇 |
1977年 | 18篇 |
1976年 | 20篇 |
1975年 | 13篇 |
1974年 | 11篇 |
1973年 | 14篇 |
1972年 | 14篇 |
排序方式: 共有3121条查询结果,搜索用时 15 毫秒
61.
A novel SON2‐based similarity index and its application for the rationalization of river water quality monitoring network 下载免费PDF全文
In this paper, a novel self‐organizing network (SON) based similarity index and its application for the optimization of sampling locations in an existing river water quality monitoring network (WQMN) is presented. A rationalization of the River Danube WQMN on its stretch through Serbia was performed using the proposed SON2‐based similarity index. A high‐dimensional dataset was used, which is composed of 18 water quality parameters that were collected during the period 2002–2010 at 17 monitoring locations. The SON‐based seasonal classification that divides 12 months into the cold, moderate, and warm seasons was employed, whereas its second application on each seasonal class yielded subclasses that were used to compare the monitoring locations. The obtained SON2‐based similarity index can be utilized for analysing seasonal variations, as well as overall similarities among neighbouring sites. Based on the calculated similarities of locations and characteristics of the River Danube basin a rationalized WQMN, which uses 30% less monitoring sites, has been proposed. 相似文献
62.
In this paper we present an electromagnetism (EM) metaheuristic for solving NP hard Maximum Betweenness Problem (MBP). A new encoding scheme with appropriate objective functions is implemented. Specific representation of the individuals enables the EM operators to explore the searching space in a way that achieves high quality solutions. An effective 1-swap based local search procedure improved by the specific caching technique is performed on each EM point. The algorithm is tested both on real and artificial instances from the literature. Experimental results show that the proposed EM approach achieves all previously known optimal solutions, except one, and achieves the best-known solutions or outperforms other approaches on all large-scale instances, except two. Provided statistical analysis indicates that the EM approach is significantly better than other approaches. 相似文献
63.
Branko Mitrović 《Nexus Network Journal》2013,15(1):51-62
Nelson Goodman’s highly influential book Languages of Art argued that that all visual experience is merely a cultural construct. In presenting his thesis Goodman relied on a series of geometrical arguments intended to show that the geometrical construction of perspective does not rely on the geometry of light rays. In this article I analyze the geometrical validity of Goodman’s arguments. 相似文献
64.
65.
This paper deals with modelling and performance of adjustable speed drives (ASDs) subjected to voltage disturbances in electric supply. The aim of this study was to develop appropriate models of typical ASD and investigate their sensitivity to voltage disturbances under various practical modes of operation and control. Accordingly, scalar controlled open and closed loop volts–hertz (V–Hz) and vector controlled closed loop ASDs are modelled in PSCAD/EMTDC environment, and their performance in the presence of voltage disturbances is investigated under typical operating and loading conditions. 相似文献
66.
P.M. Nikolić K.M. Paraskevopoulos E. Pavlidou T.T. Zorba T. Ivetić S.S. Vujatović O.S. Aleksić N. Nikolić O. Cvetković V. Blagojević M.V. Nikolić 《Materials Chemistry and Physics》2011,125(1-2):72-76
Far infrared reflectivity spectra of polycrystalline In1?xGaxSb were measured and numerically analyzed using the classical dispersion formula and also a fitting procedure based on the modified plasmon-phonon interaction model in the temperature range from 10 K to 300 K. Optical parameters were calculated and discussed. A local mode belonging to the GaSb rich end and two-mode behavior were observed at low temperatures. 相似文献
67.
Mladen Brnčić Tomislav Bosiljkov Marko Ukrainczyk Branko Tripalo Suzana Rimac Brnčić Sven Karlović Damir Karlović Damir Ježek Dražen Vikić Topić 《Food and Bioprocess Technology》2011,4(7):1296-1306
Production of extrudates from cereals is an often-used technological process in today’s world food industry. Extrudates from corn flour produced using the twin-screw extrusion process and enriched with whey protein concentrate represent high-quality source of proteins and fats. Whey protein concentrate (WPC) as a valuable source of proteins and minerals is one of the highest-quality components for possible extrudate enrichment. In this paper, the influence of various WPC addition and some extrusion process parameters such as feed moisture content ( QtextHtext2 textO Q_{{{text{H}}_{text{2}} {text{O}}}} ) on physicochemical properties of directly expanded corn flour extrudates manufactured in twin-screw co-rotating extruder was investigated. Whey protein concentrate was added in the following ratios 7.5%, 15% and 22.5% and water in 10.08, 12.18 and 14.28 L/h. Final composition of products is determined with measuring of protein, fat and water shares, water absorption index (WAI) and water solubility index (WSI). With added WPC and with increase of water volume flow, there was a significant rise in total protein, fat and water content in final products, as well as lowering of WSI and rising of WAI indexes. The statistical analysis of the obtained data shows that the lowest WSI and the highest WAI had samples with the largest share of WPC (22.5%) and water volume flow of 14.28 L/h. Colour is measured for each sample, and results were represented with hue angle (H), chroma (C) and lightness (L) values. Process parameters, WPC and QtextHtext2 textO Q_{{{text{H}}_{text{2}} {text{O}}}} influence the increase of saturation of C and lightness of L colour value, while H value stays unchanged. Mean value of H was 90.14 ± 1.06, which corresponds to dominance of yellow colour of samples. 相似文献
68.
69.
Coastal parts of Croatia are dominated by the SW‐verging Dinaric foldbelt, to the west and SW of which is the Adriatic Basin (the stable foreland). In both areas, the stratigraphic column is dominated by a thick carbonate succession ranging from Carboniferous to Miocene. Four megasequences have been identified: (i) a pre‐platform succession ranging in age from Late Carboniferous (Middle Pennsylvanian: Moscovian) to Early Jurassic (Early Toarcian; Bru?ane and Ba?ke Ostarije Formations); (ii) an Early Jurassic to Late Cretaceous platform megasequence (Mali Alan Formation); (iii) a Paleogene to Neogene post‐platform megasequence (Ra?a Formation); and (iv) a Neogene to Quaternary (Pliocene to Holocene) megasequence (Istra and Ivana Formations). A number of organic‐rich intervals with source rock potential have been identified on‐ and offshore Croatia: Middle and Upper Carboniferous, Upper Permian, Lower and Middle Triassic, Lower and Upper Jurassic, Lower and Upper Cretaceous, Eocene, and Pliocene – Pleistocene. Traps and potential plays have been identified from seismic data in the Dinaric belt and adjacent foreland. Evaporites of Permian, Triassic and Neogene (Messinian) ages form potential regional seals, and carbonates with secondary porosity form potential reservoirs. Oil and gas shows in wells in the Croatian part of the Adriatic Basin have been recorded but no oil accumulations of commercial value have yet been discovered. In the northern Adriatic offshore Croatia, Pliocene hemi‐pelagic marlstones and shales include source rocks which produce commercial volumes of biogenic gas. The gas is reservoired in unconsolidated sands of the Pleistocene Ivana Formation. 相似文献
70.
Ana Rešček Zlata Hrnjak-Murgić Nino Dimitrov Kata Galić 《Polymer-Plastics Technology and Engineering》2016,55(14):1450-1459
Polyethylene (PE) was modified and prepared as double-layer polyethylene/polycaprolactone (PE/PCL) film. Magnetite and casein were added to the PCL-coating film to improve barrier properties and prevent destruction of basic structure of primary polymer PE. Significant improvements were observed with regards to mechanical (tensile strength, elongation at break) and thermal properties, while barrier (O2 permeability) properties were slightly improved. Overall migration values into acetic acid were lower (from 1 to 4.6 mg/dm2) than the upper limit set by the legislation. Specific migration of iron in PE/PCL-Fe samples is also below (µg/L) specific migration limit value set by the legislation (mg/kg). 相似文献