全文获取类型
收费全文 | 2069362篇 |
免费 | 58592篇 |
国内免费 | 23109篇 |
专业分类
电工技术 | 57708篇 |
技术理论 | 57篇 |
综合类 | 31635篇 |
化学工业 | 340452篇 |
金属工艺 | 87586篇 |
机械仪表 | 72996篇 |
建筑科学 | 81443篇 |
矿业工程 | 25053篇 |
能源动力 | 61211篇 |
轻工业 | 158454篇 |
水利工程 | 23971篇 |
石油天然气 | 62268篇 |
武器工业 | 3561篇 |
无线电 | 241460篇 |
一般工业技术 | 352874篇 |
冶金工业 | 283965篇 |
原子能技术 | 38253篇 |
自动化技术 | 228116篇 |
出版年
2022年 | 18728篇 |
2021年 | 30327篇 |
2020年 | 23244篇 |
2019年 | 23681篇 |
2018年 | 28580篇 |
2017年 | 29551篇 |
2016年 | 33374篇 |
2015年 | 32518篇 |
2014年 | 47932篇 |
2013年 | 110744篇 |
2012年 | 64923篇 |
2011年 | 82347篇 |
2010年 | 69329篇 |
2009年 | 75507篇 |
2008年 | 72977篇 |
2007年 | 70211篇 |
2006年 | 70760篇 |
2005年 | 63044篇 |
2004年 | 57481篇 |
2003年 | 55616篇 |
2002年 | 53031篇 |
2001年 | 49953篇 |
2000年 | 47977篇 |
1999年 | 50322篇 |
1998年 | 85008篇 |
1997年 | 65177篇 |
1996年 | 54255篇 |
1995年 | 43588篇 |
1994年 | 39325篇 |
1993年 | 37680篇 |
1992年 | 30330篇 |
1991年 | 27250篇 |
1990年 | 26957篇 |
1989年 | 25796篇 |
1988年 | 24164篇 |
1987年 | 21827篇 |
1986年 | 21218篇 |
1985年 | 24313篇 |
1984年 | 23550篇 |
1983年 | 21461篇 |
1982年 | 20211篇 |
1981年 | 20367篇 |
1980年 | 19030篇 |
1979年 | 19269篇 |
1978年 | 18453篇 |
1977年 | 19906篇 |
1976年 | 23677篇 |
1975年 | 16499篇 |
1974年 | 15902篇 |
1973年 | 16057篇 |
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
991.
Parsania P. H. Sankhavara Dharmesh B. Chopda Jalpa Patel Jignesh P. 《Polymer Bulletin》2020,77(6):3111-3128
Polymer Bulletin - Jute and glass composites of epoxy resin of (2E, 6E)-bis(4-hydroxybenzylidene)cyclohexanone (EBHBC) were prepared by compressing molding technique using three different hardeners... 相似文献
992.
Maimaitiaili Tayier Yunfeng Zhao Dengle Duan Rongge Zou Yunpu Wang Roger Ruan 《木材化学与工艺学杂志》2020,40(3):190-199
AbstractLignin biochar-catalytic depolymerization using biochar Fe-600, Fe-800, Ni-600, Ni-800 catalysts under microwave-heating (180?°C for 30?min) was explored in an ethanol/formic acid (1:1) media. Non-catalyst depolymerization was also studied and compared with the biochar-catalysts results. Characteristics of the bio-char catalysts were analyze by BET, XRD, and FT-IR. GPC, FT-IR, and MALDI-TOF MS spectrometry were also used to characterize the depolymerization products. The experimental results showed that the SBET, Vt, and Vmec and average pore diameter of the biochars are considerably dependent on the preparation temperature and type of cation (Ni2+ or Fe3+). The maximum yield of bio-oil product was obtained as 85?wt% with the addition of biochar Ni-600 and the total amount of oligomers or monomers with a molecular weight of 164 to 446 reaches 80.4%. 相似文献
993.
Palmitoleic acid has been classified as an insulin-sensitizing lipokine, but evidence for this from human studies has been inconsistent. We hypothesized that this is related to either the types of samples or conditions under which samples are collected. We measured plasma palmitoleic acid and total free fatty acids (FFA) using ultra-performance liquid chromatography in blood samples collected from 34 adults under a variety of conditions. We collected duplicate samples of adipose (n = 10), FFA (n = 9), and very low density lipoprotein triacylglycerol (VLDL-TAG) (n = 7) to measure the palmitoleic acid as a percentage of total fatty acids. We tested whether the percentage of palmitoleic acid was correlated with insulin resistance, as measured by homeostatic model of insulin resistance (HOMA-IR). Adipose stearoyl-coenzyme A desaturase 1 (SCD-1) protein was measured by capillary Western blotting. FFA-palmitoleic acid percentage increased as a function of total FFA and was greater (p < 0.005) in females than males. Adipose palmitoleic acid percentage was greater in females than males (p < 0.001), as was adipose SCD-1. Palmitoleic acid was greater in femoral fat than in abdominal fat in both females and males (p < 0.001), and correlated positively with HOMA-IR only in females. The test–retest reliability values for percentage palmitoleic acid were 7 ± 10% for adipose, 24 ± 26% for VLDL, and 53 ± 31% for FFA. Because FFA-palmitoleic acid percentage varies as a function of total FFA, investigators should re-evaluate how palmitoleic acid data is presented. The positive relationship between adipose palmitoleic acid and HOMA-IR in females suggests that it is not a potent insulin-sensitizing lipokine in humans. 相似文献
994.
Chunliang Li Theo Veldhuis Bart Reuvers Rafaël J Sablong Cor E Koning 《Polymer International》2020,69(1):24-30
Limonene‐derived polycarbonate‐based alkyd resins (ARs) have been prepared by copolymerization of limonene dioxide with CO2, catalysed by a β‐diiminate zinc–bis(trimethylsilyl)amido complex, and subsequent chemical modification with soybean oil fatty acids using triphenylethylphosphonium bromide as the catalyst. This quantitative partial modification was realized via epoxy–carboxylic acid chemistry, affording ARs with higher oil lengths, lower polydispersities and higher glass transition temperatures (Tg) in comparison to a conventional polyester AR based on phthalic acid, multifunctional polyol pentaerythritol and soybean fatty acid. The novel limonene polycarbonate AR and the conventional polyester AR were evaluated as coatings and both the physical drying (without the presence of the oxidative drying accelerator Borchi® Oxy Coat) and chemical curing (with Borchi® Oxy Coat) processes of these coatings were monitored by measuring the König hardness and complex modulus development with time. A better performance was obtained for the alkyd paint containing polycarbonates modified with fatty acids (FA‐PCs), which showed a faster chemical drying, a higher König hardness and a higher Tg in coating evaluation, demonstrating that the fully renewable FA‐PCs are promising resins for alkyd paint applications. © 2019 Society of Chemical Industry 相似文献
995.
Nathan M. Wilbur Antin M. O'Sullivan Kerry T. B. MacQuarrie Tommi Linnansaari R. Allen Curry 《河流研究与利用》2020,36(5):769-783
Anthropogenic influences, including climate change, are increasing river temperatures in northern and temperate regions and threatening the thermal habitats of native salmonids. When river temperatures exceed the tolerance levels of brook trout and Atlantic salmon, individuals exhibit behavioural thermoregulation by seeking out cold‐water refugia – often created by tributaries and groundwater discharge. Thermal infrared (TIR) imagery was used to map cold‐water anomalies along a 53 km reach of the Cains River, New Brunswick. Trout and salmon parr did not use all identified thermal anomalies as refugia during higher river temperature periods (>21°C). Most small‐bodied trout (8–30 cm) were observed in 80% of the thermal anomalies sampled. Large‐bodied trout (>35 cm) required a more specific set of physical habitat conditions for suitable refugia, that is, 100% of observed large trout used 30% of the anomalies sampled and required water depths >65 cm within or adjacent to the anomaly. Densities of trout were significantly higher within anomalies compared with areas of ambient river temperature. Salmon parr were less aligned with thermal anomalies at the observed temperatures, that is, 59% were found in 65% of the sampled anomalies; and densities were not significantly different within/ outside anomalies. Salmon parr appeared to aggregate at 27°C, and after several events over 27°C variability in aggregation behaviour was observed – some fish aggregated at 25°C, others did not. We stipulate this is due to variances of thermal fatigue. Habitat suitability curves were developed for velocity, temperature, depth, substrate, and deep water availability to characterize conditions preferred by fish during high‐temperature events. These findings are useful for managers as our climate warms, and can potentially be used as a tool to help conserve and enhance thermal refugia for brook trout and Atlantic salmon in similar systems. 相似文献
996.
I. P. Ivanchenko A. N. Prokopenko 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2020,53(6):671-680
Equipment of the Krasnoyarsk HPP is considered as an example to analyze the dependence of crack formation in runner blades on the operating conditions of t 相似文献
997.
High‐intensity sweeteners in espresso coffee: ideal and equivalent sweetness and time–intensity analysis
下载免费PDF全文
![点击此处可从《International Journal of Food Science & Technology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Bruna M. Azevedo Flávio L. Schmidt Helena M. A. Bolini 《International Journal of Food Science & Technology》2015,50(6):1374-1381
The efficient substitution of sucrose by a sweetener in beverages requires the application of some sensory techniques. First, one must determine the concentrations of the sweeteners under study, equivalent in sweetness to the ideal sucrose concentration. In addition, it is fundamental to determine which is most similar to sucrose. The objectives of this study were to determine the ideal sweetness for espresso coffee and the equivalent concentrations in sweetness of different sweeteners, as well as characterise the time–intensity profile of each sweetener in relation to sweetness. The sweeteners evaluated were sucralose, aspartame, neotame, a cyclamate/saccharin mixture (2:1) and stevia. The sucrose concentration considered ideal by consumers was 12.5% (w/v), and the equivalent concentrations of the sweeteners were 0.0159% for sucralose, 0.0549% for aspartame, 0.0016% for neotame, 0.0359% for the cyclamate/saccharin mixture and 0.0998% for stevia. The time–intensity analysis indicated that possibly the sweeteners neotame, aspartame and sucralose would be the best substitutes for sucrose. 相似文献
998.
999.
1000.