全文获取类型
收费全文 | 2033篇 |
免费 | 65篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 10篇 |
综合类 | 1篇 |
化学工业 | 518篇 |
金属工艺 | 44篇 |
机械仪表 | 56篇 |
建筑科学 | 63篇 |
矿业工程 | 3篇 |
能源动力 | 26篇 |
轻工业 | 371篇 |
水利工程 | 11篇 |
石油天然气 | 5篇 |
无线电 | 52篇 |
一般工业技术 | 638篇 |
冶金工业 | 143篇 |
原子能技术 | 8篇 |
自动化技术 | 152篇 |
出版年
2023年 | 11篇 |
2022年 | 56篇 |
2021年 | 77篇 |
2020年 | 31篇 |
2019年 | 48篇 |
2018年 | 73篇 |
2017年 | 60篇 |
2016年 | 67篇 |
2015年 | 55篇 |
2014年 | 67篇 |
2013年 | 95篇 |
2012年 | 122篇 |
2011年 | 189篇 |
2010年 | 99篇 |
2009年 | 87篇 |
2008年 | 142篇 |
2007年 | 91篇 |
2006年 | 89篇 |
2005年 | 46篇 |
2004年 | 42篇 |
2003年 | 45篇 |
2002年 | 50篇 |
2001年 | 34篇 |
2000年 | 31篇 |
1999年 | 18篇 |
1998年 | 39篇 |
1997年 | 41篇 |
1996年 | 28篇 |
1995年 | 24篇 |
1994年 | 18篇 |
1993年 | 10篇 |
1992年 | 8篇 |
1991年 | 10篇 |
1990年 | 9篇 |
1989年 | 17篇 |
1988年 | 12篇 |
1987年 | 6篇 |
1986年 | 12篇 |
1985年 | 6篇 |
1984年 | 13篇 |
1983年 | 11篇 |
1982年 | 16篇 |
1981年 | 9篇 |
1980年 | 9篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1976年 | 22篇 |
1975年 | 7篇 |
1973年 | 6篇 |
1968年 | 4篇 |
排序方式: 共有2101条查询结果,搜索用时 18 毫秒
91.
Legumes can be a source of mineral elements but also of antinutritional factors which can affect their absorption. An in vitro method including gastrointestinal digestion was used to estimate mineral bioavailability. Soluble (bioaccessible) and insoluble calcium, iron and zinc from white beans, chickpeas and lentils were determined after gastrointestinal digestion. The influence of the original sample weight on the soluble mineral fraction was also estimated. The results obtained show that white beans are the legumes with the highest bioaccessible calcium and iron contents. Lentils have a high iron content but its bioaccessibility is much lower than that of iron from white beans and chickpeas. An increase in sample weight increases the amount of bioaccessible element available for intake, but the increase is not always proportional. 相似文献
92.
Antônio Alisson Alencar Freitas Fernando Lessa Tofoli Edilson Mineiro Sá Junior Sergio Daher Fernando Luiz Marcelo Antunes 《International Journal of Electronics》2016,103(5):898-912
A high voltage step-up nonisolated DC–DC converter based on coupled inductors suitable to photovoltaic (PV) systems applications is proposed in this paper. Considering that numerous approaches exist to extend the voltage conversion ratio of DC–DC converters that do not use transformers, a detailed comparison is also presented among the proposed converter and other popular topologies such as the conventional boost converter and the quadratic boost converter. The qualitative analysis of the coupled-inductor-based topology is developed so that a design procedure can be obtained, from which an experimental prototype is implemented to validate the theoretical assumptions. 相似文献
93.
In this work the electrochemical characteristics of copper and steel in chromate, cyanide, and phosphate baths as well as in a commercial bath (ENSTRIP S-180), in the absence of chromium and cyanides were determined. Average rates of copper coatings stripping from steel in the above mentioned baths and the baths influence on the morphology of steel surfaces were described. It was found that the commercial bath ENSTRIP S-180 could be successfully used for stripping of copper coatings from steel elements. 相似文献
94.
Sulaiman Al-Khattaf Syed A. Ali Abdullah M. Aitani Naděžda Žilková David Kubička 《Catalysis Reviews》2014,56(4):333-402
Alkylbenzenes form an important segment of petrochemical industry for the manufacture of widely used commodities and specialty products. Since the last review on this topic (8), numerous new zeolite-based catalysts have been synthesized, characterized and evaluated in various transformations of aromatic hydrocarbons. This comprehensive review covers major reactions of mono-, di-, and tri-alkylbenzenes such as disproportionation, alkylation, transalkylation, isomerization, etc., over different zeolite-based acid catalysts. During the last decade, significant progress was made in the synthesis and structure determination of novel zeolites, mesoporous single crystals, hierarchic zeolites and two-dimensional zeolites. These developments have enhanced the understanding of the role of zeolites (effects of structural type, morphology, acid sites, accessibility of acid sites, shape selectivity factors) in transformations of aromatics. In this review, the emphasis is on the influence of the type of acid sites, zeolite topology, and reaction conditions on the activity, selectivity and pathways of these reactions. Thermodynamics and reaction kinetics of transformations of aromatic hydrocarbons are also discussed. This article covers mostly literature published during the period of 2002–2013. 相似文献
95.
96.
97.
Anton Trník Igor Štubňa Jana Moravčíková 《International Journal of Thermophysics》2009,30(4):1323-1328
The sound velocity of Sedlec kaolin during heating from 20 °C to 1100 °C was investigated by modulated force thermomechanical
analysis (mf-TMA). In the interval from 20 °C to 250 °C, the sound velocity increases which can be explained by liberation
of the water molecules from pores and micropores. Dehydroxylation (450 °C to 650 °C) presents itself with a decrease of the
sound velocity. After dehydroxylation, a two-step increase of the sound velocity was observed. The first step of the increase
of the sound velocity is due to solid-state sintering at low temperatures. The second step starts at 950 °C as a consequence
of the collapse of the metakaolinite structure. After the maximum, a steep increase of the sound velocity follows as a result
of solid-state sintering. 相似文献
98.
O. Dóka D. Bicanic J. G. Buijnsters R. Spruijt S. Luterotti Gy. Végvári 《European Food Research and Technology》2010,230(6):813-819
The total carotenoid concentration (TCC) of several commercially available dried pastas prepared with or without eggs was
assessed by means of the two well-established destructive approaches [spectrophotometry (SP) and high-performance liquid chromatography (HPLC)] and three non-destructive, direct (i.e., no sample preparation required) methods (resonance Raman spectroscopy, photoacoustic (PA) spectroscopy and colorimetry).
The results obtained by the three direct methods correlate well with the TCC of investigated dried pastas assessed by SP and
HPLC. The best linear correlation and detection limit were achieved for the PA method at 470 nm. 相似文献
99.
Atomic force microscopy (AFM) has been used to study the effect of various photoinitiators doped into poly(methyl methacrylate)
(PMMA) on the mechanical properties of PMMA films at the nanometer scale. Pure and modified PMMA films (containing four different
photoinitiators) were exposed to a mercury vapor lamp in air atmosphere. Force–distance curves for hardness, Young modulus,
and adhesion forces were obtained using different AFM modes (tapping or contact-mode) and different tips (diamond or silicon
nitride). The results revealed that the added photoinitiators slightly changed the nanomechanical properties of PMMA as a
result of alterations in the photochemical reactions and physical processes occurring in the studied systems. tert-Butyl peroxybenzoate had the most efficient effect on the measured parameters in UV-irradiated PMMA, whereas benzoyl peroxide
was less active. The mechanism of the observed processes is discussed. 相似文献
100.
What is the source of ochratoxin A in wine? 总被引:1,自引:0,他引:1
Cabañes FJ Accensi F Bragulat MR Abarca ML Castellá G Minguez S Pons A 《International journal of food microbiology》2002,79(3):213-215
During a microvinification trial using natural mouldy grapes from a research experimental vineyard, ochratoxin A (OTA) contaminated white wine was obtained. Potential OTA-producing mycobiota of grape samples used in this microvinification process was assessed. Only Aspergillus carbonarius isolates were detected as producers of OTA. Our report is a strong evidence of the contribution of A. carbonarius in the OTA contamination in wine. 相似文献