全文获取类型
收费全文 | 2572篇 |
免费 | 208篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 13篇 |
综合类 | 4篇 |
化学工业 | 780篇 |
金属工艺 | 7篇 |
机械仪表 | 40篇 |
建筑科学 | 97篇 |
矿业工程 | 1篇 |
能源动力 | 46篇 |
轻工业 | 533篇 |
水利工程 | 22篇 |
石油天然气 | 13篇 |
无线电 | 97篇 |
一般工业技术 | 292篇 |
冶金工业 | 593篇 |
原子能技术 | 12篇 |
自动化技术 | 232篇 |
出版年
2024年 | 12篇 |
2023年 | 31篇 |
2022年 | 128篇 |
2021年 | 143篇 |
2020年 | 54篇 |
2019年 | 65篇 |
2018年 | 103篇 |
2017年 | 94篇 |
2016年 | 109篇 |
2015年 | 73篇 |
2014年 | 111篇 |
2013年 | 165篇 |
2012年 | 139篇 |
2011年 | 167篇 |
2010年 | 125篇 |
2009年 | 121篇 |
2008年 | 118篇 |
2007年 | 102篇 |
2006年 | 95篇 |
2005年 | 87篇 |
2004年 | 65篇 |
2003年 | 57篇 |
2002年 | 56篇 |
2001年 | 31篇 |
2000年 | 35篇 |
1999年 | 28篇 |
1998年 | 32篇 |
1997年 | 32篇 |
1996年 | 35篇 |
1995年 | 23篇 |
1994年 | 29篇 |
1993年 | 22篇 |
1992年 | 34篇 |
1990年 | 23篇 |
1989年 | 22篇 |
1988年 | 17篇 |
1987年 | 22篇 |
1986年 | 16篇 |
1985年 | 15篇 |
1984年 | 22篇 |
1982年 | 8篇 |
1981年 | 23篇 |
1980年 | 7篇 |
1979年 | 15篇 |
1978年 | 10篇 |
1977年 | 12篇 |
1976年 | 7篇 |
1975年 | 7篇 |
1974年 | 6篇 |
1972年 | 6篇 |
排序方式: 共有2782条查询结果,搜索用时 31 毫秒
101.
Portilla-Sangabriel Melisa Arzate Sandra Macías-Vargas José-Alberto Ramírez-Zamora Rosa-María 《Topics in Catalysis》2021,64(1-2):181-193
Topics in Catalysis - The use of the magnetic fraction (MF) of a low-grade titanium ore (TO) and two oxidants (H2O2 and NaClO), testing each one separately, were compared in photo-Fenton like... 相似文献
102.
Sandra Horvitz María J. Cantalejo 《International Journal of Food Science & Technology》2012,47(9):1935-1943
The effects of chlorine (200 μL L?1), ozonated water (1 μL L?1) and gaseous ozone (0.7 μL L?1) on physicochemical attributes and microbial quality of minimally processed red bell peppers were studied. In all the experiments, O2 continuously decreased and CO2 concentration increased, the pH augmented and a significant softening was observed in all the fruits. By day 14, L* values decreased in all the fruits, with the greatest changes found in the chlorinated samples (approximately 12 units). Peppers treated with the aqueous solutions showed greater changes in the quality attributes with increasing washing times and especially when chlorine was used. The exposure for three min to gaseous O3 reduced the mesophiles, psychrotrophes and fungal populations of the fresh‐cut peppers in 2.5, 3.3 and 1.8 log units, respectively. Combined with modified atmosphere, this could be an appropriate method to maintain the quality and extend the storage period of minimally processed red bell peppers. 相似文献
103.
Mpho Sandra Malaka Kersch Naidoo John Kabuba 《Chemical Engineering Communications》2017,204(7):813-819
Siphonochilus aethiopicus is an indigenous South African plant also known as African ginger. It has often been used for its medicinal properties to treat various ailments such as flu, colds, and so forth. The research aim of this study was to optimize the process parameters of steam distillation for the extraction of oil from African ginger rhizomes. This technology is the oldest and well known for extracting essential oils due to its economic viability and the higher final oil purity. The effects of operating parameters such as extraction duration, moisture content, particle size, and temperatures between 80°C and 100°C were studied for maximum oil recovery. The oil recovery of 0.61% (w/w) was achieved after 270?min of extraction time, using 6.37% (dry) moisture content of particle size 2.4?mm–4?mm at a maximum temperature of 100°C. Fick’s first law was used to mathematically model the experimental data of this study. 相似文献
104.
Benedetta Pasquini Mohammad Goodarzi Serena Orlandini Giangiacomo Beretta Sandra Furlanetto Bieke Dejaegher 《International Journal of Food Science & Technology》2014,49(5):1351-1359
In this article, discrimination models are presented, relating the origin of honey samples to several variables, being the concentrations of different cations and anions in the honey samples measured by ion chromatography, and parameters that measure/reflect the antioxidant activity of the honey samples. The unsupervised method, principal component analysis, and supervised discrimination methods, such as linear and quadratic discriminant analysis, and classification and regression trees (CART), were applied to evaluate the existence of data patterns and the relationship between geographical origin and the measured parameters. The model with the best predictive ability (%CCRTEST = 66.67%), the best overall % specificity (80%) and the best overall % sensitivity (67%) was found to be CART. It was proven that the mineral content and parameters analysed can provide enough information for the geographical characterisation and discrimination of honey. 相似文献
105.
A Systematic Structure–Activity Study of a New Type of Small Peptidic Transfection Vector Reveals the Importance of a Special Oxo-Anion-Binding Motif for Gene Delivery
下载免费PDF全文
![点击此处可从《Chembiochem : a European journal of chemical biology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Dr. Sandra Junghänel Sarah Karczewski Sandra Bäcker Prof. Dr. Shirley K. Knauer Prof. Dr. Carsten Schmuck 《Chembiochem : a European journal of chemical biology》2017,18(22):2268-2279
We discovered a new class of artificial peptidic transfection vectors based on an artificial anion-binding motif, the guanidiniocarbonylpyrrole (GCP) cation. This new type of vector is surprisingly smaller than traditional systems, and our previous work suggested that the GCP group was important for promoting critical endosomal escape. We now present here a systematic comparison of similar DNA ligands featuring our GCP oxo-anion-binding motif with DNA ligands only consisting of naturally occurring amino acids. Structure–activity studies showed that the artificial binding motif clearly outperformed natural amino acids such as histidine, lysine, and arginine. It improved the ability to shuttle foreign genetic material into cells, yet successfully mediated endosomal escape. Also, plasmids that were complexed by our artificial ligands were stabilized against cytosolic degradation to some extent. This resulted in the successful expression of plasmid information (comparable to gold standards such as polyethyleneimine). Hence, our study clearly demonstrates the importance of the tailor-made GCP anion-binding site for efficient gene transfection. 相似文献
106.
Florian Röper Markus Wolfahrt Sandra Schlögl Georg Kucher Gerald Pinter 《应用聚合物科学杂志》2019,136(19):47506
Repair of composite structures and the impact of demanding environmental conditions is a crucial issue for the aircraft industry because of the increasing use of composites in modern aircraft. Consequently, the impact of environmental conditions common for aircraft applications on repair specimens in comparison to nonrepaired specimens is studied. All specimens are produced from a woven carbon fiber-reinforced epoxy-based prepreg. For the repair-specimens, an epoxy-based film adhesive is used for the soft patch repair approach. During the repair process, the surface of the precured prepreg is prepared by a mechanical method (sanding) and an additional chemical functionalization, respectively. Moisture absorption of the repair specimens is independent of the surface preparation method and higher for the repaired than for the nonrepaired specimens. The key influencing environmental conditions for the tensile strength and the failure mode of the repair specimens are elevated temperature testing as well as hot/wet conditioning and conditioning in deionized water. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47506. 相似文献
107.
108.
Altered blood flow during embryonic development has been shown to cause cardiac defects; however, the mechanisms by which the resulting haemodynamic forces trigger heart malformation are unclear. This study used heart outflow tract banding to alter normal haemodynamics in a chick embryo model at HH18 and characterized the immediate blood flow response versus the degree of band tightness. Optical coherence tomography was used to acquire two-dimensional longitudinal structure and Doppler velocity images from control (n = 16) and banded (n = 25, 6–64% measured band tightness) embryos, from which structural and velocity data were extracted to estimate haemodynamic measures. Peak blood flow velocity and wall shear rate (WSR) initially increased linearly with band tightness (p < 0.01), but then velocity plateaued between 40% and 50% band tightness and started to decrease with constriction greater than 50%, whereas WSR continued to increase up to 60% constriction before it began decreasing with increased band tightness. Time of flow decreased with constriction greater than 20% (p < 0.01), while stroke volume in banded embryos remained comparable to control levels over the entire range of constriction (p > 0.1). The haemodynamic dependence on the degree of banding reveals immediate adaptations of the early embryonic cardiovascular system and could help elucidate a range of cardiac adaptations to gradually increased load. 相似文献
109.
Sandra P.O Dwyer David OBeirne Deirdre Ní Eidhin Brendan T. OKennedy 《Journal of food science》2012,77(12):N58-N65
Abstract: This study examined the effectiveness of fat and water soluble antioxidants on the oxidative stability of omega (ω)‐3 rich table spreads, produced using novel multiple emulsion technology. Table spreads were produced by dispersing an oil‐in‐water (O/W) emulsion (500 g/kg 85 camelina/15 fish oil blend) in a hardstock/rapeseed oil blend, using sodium caseinate and polyglycerol polyricinoleate as emulsifiers. The O/W and oil‐in‐water‐in‐oil (O/W/O) emulsions contained either a water soluble antioxidant (green tea extract [GTE]), an oil soluble antioxidant (α‐Tocopherol), or both. Spreads containing α‐Tocopherol had the highest lipid hydroperoxide values, whereas spreads containing GTE had the lowest (P < 0.05), during storage at 5 °C, while p‐Anisidine values did not differ significantly. Particle size was generally unaffected by antioxidant type (P < 0.05). Double emulsion (O/W/O) structures were clearly seen in confocal images of the spreads. By the end of storage, none of the spreads had significantly different G′ values. Firmness (Newtons) of all spreads generally increased during storage (P < 0.05). Practical Application: Lipid oxidation is a major problem in omega‐3 rich oils, and can cause off‐odors and off‐flavors. Double emulsion technology was used to produce omega‐3 enriched spreads (O/W/O emulsions), wherein the omega‐3 oil was incorporated into the inner oil phase, to protect it from lipid oxidation. Antioxidants were added to further protect the spreads by reducing lipid oxidation. Spreads produced had good oxidative stability and possessed functional (omega‐3 addition) properties. 相似文献
110.
Explaining the Formation of Online News Startups in France and the United States: A Field Analysis
下载免费PDF全文
![点击此处可从《The Journal of communication》网站下载免费的PDF全文](/ch/ext_images/free.gif)
This article examines the differential formation of online news startups in Toulouse, France, and Seattle, United States. While Seattle is home to many startups, in Toulouse there have been just 4—and only 1 continues publishing. Drawing on Bourdieu's field theory, we argue that amount and types of capital held by journalists in the 2 cities varied as a result of differences in journalism's position in the field of power. These differences shaped the extent of startup formation in each city and structured journalists' capacities to convert their capital into the resources needed to form startups (e.g., funding, credentials, partnerships). These findings are positioned in relation to literatures on journalism innovation and comparative media. 相似文献