全文获取类型
收费全文 | 5891篇 |
免费 | 972篇 |
国内免费 | 315篇 |
专业分类
电工技术 | 167篇 |
技术理论 | 2篇 |
综合类 | 316篇 |
化学工业 | 688篇 |
金属工艺 | 230篇 |
机械仪表 | 269篇 |
建筑科学 | 334篇 |
矿业工程 | 71篇 |
能源动力 | 368篇 |
轻工业 | 2355篇 |
水利工程 | 629篇 |
石油天然气 | 603篇 |
武器工业 | 98篇 |
无线电 | 150篇 |
一般工业技术 | 346篇 |
冶金工业 | 54篇 |
原子能技术 | 48篇 |
自动化技术 | 450篇 |
出版年
2024年 | 41篇 |
2023年 | 159篇 |
2022年 | 256篇 |
2021年 | 305篇 |
2020年 | 308篇 |
2019年 | 313篇 |
2018年 | 250篇 |
2017年 | 278篇 |
2016年 | 312篇 |
2015年 | 294篇 |
2014年 | 344篇 |
2013年 | 478篇 |
2012年 | 485篇 |
2011年 | 467篇 |
2010年 | 329篇 |
2009年 | 273篇 |
2008年 | 253篇 |
2007年 | 313篇 |
2006年 | 271篇 |
2005年 | 186篇 |
2004年 | 146篇 |
2003年 | 141篇 |
2002年 | 154篇 |
2001年 | 106篇 |
2000年 | 93篇 |
1999年 | 55篇 |
1998年 | 58篇 |
1997年 | 69篇 |
1996年 | 69篇 |
1995年 | 44篇 |
1994年 | 42篇 |
1993年 | 40篇 |
1992年 | 60篇 |
1991年 | 34篇 |
1990年 | 20篇 |
1989年 | 22篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 14篇 |
1985年 | 14篇 |
1984年 | 20篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1981年 | 1篇 |
1980年 | 6篇 |
1979年 | 2篇 |
1977年 | 3篇 |
1959年 | 1篇 |
排序方式: 共有7178条查询结果,搜索用时 31 毫秒
1.
Pedro Ideia Lorenzo Degli Esposti Carla Caseiro Miguel Alessio Adamiano Michele Iafisco Paula C. Castilho 《International Journal of Applied Ceramic Technology》2021,18(1):235-243
The conversion of food industry by-products to compounds with high added value is nowadays a significant topic, for social, environmental, and economic reasons. In this paper, calcium phosphate-based materials were obtained from black scabbardfish (Aphanopus carbo) bones and grey triggerfish (Balistes capriscus) skin, which are two of the most abundant fish by-products of Madeira Island. Different calcination temperatures between 400 and 1000°C were employed. Materials obtained from calcination of bones of black scabbard fish were composed by homogeneous mixtures of hydroxyapatite (Ca10(PO4)6(OH)2, HAp) and β-tricalcium phosphate (β-Ca3(PO4)2, β-TCP). Because of the high biocompatibility of HAp and the good resorbability of β-TCP, these natural biphasic materials could be very relevant in the field of biomaterials, as bone grafts. The ratio between HAp and β-TCP in the biphasic compound was dependent on the calcination temperature. Differently, the material obtained from skin of grey triggerfish contained HAp as the main phase, together with small amounts of other mineral phases, such as halite and rhenanite, which are known to enhance osteogenesis when used as bone substitutes. In both cases, the increase of calcination temperature led to an increase in the particles size with a consequent decrease in their specific surface area. These results demonstrate that from the fish by-products of the most consumed fishes in Madeira Island it is possible to obtain bioceramic materials with tunable composition and particle morphology, which could be promising materials for the biomedical field. 相似文献
2.
3.
Wenjie Liu Jianmin Liu Shu Xing Xiaobin Li Liwen Han Kechun Liu Tao Wei Mingyang Zhou 《European Journal of Lipid Science and Technology》2021,123(6):2000276
In this study, the anti-atherosclerotic properties of three marine phospholipids (MPLs) extracts from fishery by-products including codfish roe, squid gonad, and shrimp head are verified. Their effects on key factors involved in atherosclerosis are examined and compared to explore whether the differences in their constitutions lead to the differences in the function. All three MPLs dampen oxidation of low- density lipoproteins (LDL) in vitro. Treating RAW264.7 macrophages and HUVECs endothelial cells with each MPLs ranging 10–100 µg mL−1 does not decrease cell viability, yet ox-LDL caused cytotoxicity of both cells are alleviated by 50 or 100 µg mL−1 MPLs treatment. In addition, the three MPLs reduce ox-LDL induced macrophage foam-like transition, mainly through inhibition of lipid uptake. Of the three MPLs, the one from squid gonad exhibits the best effect. On the other hand, all three MPLs modulate inflammatory responses, equally, by inhibiting the adhesion of monocytes to endothelial cells, and decreasing secretion of pro-inflammatory cytokines IL-6 and MCP-1. Using a high-cholesterol diet induced zebrafish model, it is found that all three MPLs, especially the one from squid gonad, alleviates cholesterol accumulation in early plaques, and decreases total cholesterol as well as lipid peroxide in vivo. Practical Applications: As a way of making the best of the increasingly scarce marine resources, valuable lipid components can be recovered from by-products and wastes from the fishery industry. Here, we tested the anti-atherosclerotic effects and the mechanisms of three MPLs extracted from codfish roe, squid gonad, and shrimp head. Our study provides further evidence that marine phospholipids extracted from fishery by-products could protect against atherosclerosis, and helps to elucidate the structure-function relationship of MPLs. 相似文献
4.
为解决定距螺旋桨与船用主机在船舶运行工况的机桨匹配问题,结合船舶系泊和航行试验的相关标准,分析和归纳船舶运行数据,将实船测试与船机桨匹配理论计算相结合,得出运输船和拖轮在常用工况及特殊工况下定距螺旋桨对主机外特性的定量要求,为配套不同细分市场时船用主机的优化和开发提供参考依据。 相似文献
5.
6.
7.
随着我国环境保护法规《大气污染防治法》的修订和《涂料征收消费税通知》的公布,探讨了其对船舶涂料企业的冲击及其应对措施。 相似文献
8.
9.
Pakteera Sripokar Yi Zhang Benjamin K. Simpson Egon Bech Hansen Suppasil Maneerat Sappasith Klomklao 《International Journal of Food Science & Technology》2021,56(12):6368-6375
Beardless barb is a common fish species used in fermentation of fish paste Ka-pi-plaa. Autolytic profile of beardless barb muscle showed the maximum autolysis was at 50 °C, at both acidic and alkaline pH values. With augmentation concentration of NaCl, autolytic activity slightly decreased. Endogenous proteinases isolated from fish muscle in crude extract forms were also characterised. The acidic proteinases had optimum activity at pH 3.0 and 50°C, and they showed higher proteolytic activity than the alkaline proteinases which were optimally active at pH 9.0 and 50 °C. Proteinases in peak at pH 3.0 were inhibited by pepstatin A, but those in peak at pH 9.0 were highly inhibited by PMSF, TLCK and soybean trypsin inhibitor, suggesting that both aspartic and serine proteinases were existed in beardless barb muscle. The proteinases were stable in pH range of 2.0-5.0 but unstable at the temperatures higher than 40 °C. NaCl suppressed the proteolytic activity, ATP activated the proteinase activity, while CaCl2, MgCl2 and CoCl2 exhibited no influence on the activity. The results implied that cathepsin D is the predominant proteinase responsible for autolysis in beardless barb. The findings were useful to improve the processing and qualities of Ka-pi-plaa product using beardless barb as raw material. 相似文献
10.
Edible film from water-soluble fish proteins were developed by casting film solution on leveled trays and effects of pH (9.5, 10.0 and 10.5), heating temperature (60, 70 and 80 °C), and heating time (10, 20 and 30 min) of the film solution on various film properties were determined using Response Surface Methodology (RSM). The impact of pH and heating temperature of film solution was more significant, overall, on the film's properties than heating time. Contour plots of tensile strength and elongation at break was highest at pH of 10.0 at 70 °C (2.75-3.02 MPa) but low in elongation at break (6.35-9.16%), while water vapor permeability and oxygen permeability were at their lowest (58.55-65.96 g mm/m2 d kPa and 351.33-624.18 cm3 μm/m2 d kPa). There was a direct correlation between the films’ and proteins’ solubility on one hand, and heating temperature of film solution on the other, which reversed with change in pH of film solution. Film color was darker and more yellowish with increase in the pH of film solution. 相似文献