全文获取类型
收费全文 | 406篇 |
免费 | 16篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 93篇 |
金属工艺 | 10篇 |
机械仪表 | 5篇 |
建筑科学 | 32篇 |
矿业工程 | 1篇 |
能源动力 | 8篇 |
轻工业 | 73篇 |
水利工程 | 6篇 |
无线电 | 20篇 |
一般工业技术 | 63篇 |
冶金工业 | 45篇 |
原子能技术 | 3篇 |
自动化技术 | 62篇 |
出版年
2024年 | 2篇 |
2023年 | 9篇 |
2022年 | 11篇 |
2021年 | 21篇 |
2020年 | 11篇 |
2019年 | 14篇 |
2018年 | 15篇 |
2017年 | 12篇 |
2016年 | 11篇 |
2015年 | 11篇 |
2014年 | 15篇 |
2013年 | 29篇 |
2012年 | 27篇 |
2011年 | 36篇 |
2010年 | 20篇 |
2009年 | 8篇 |
2008年 | 26篇 |
2007年 | 20篇 |
2006年 | 14篇 |
2005年 | 20篇 |
2004年 | 14篇 |
2003年 | 17篇 |
2002年 | 5篇 |
2001年 | 9篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 1篇 |
1993年 | 4篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1985年 | 3篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
排序方式: 共有422条查询结果,搜索用时 15 毫秒
51.
52.
Bekaert B Cooper ML Green FR McNulty H Pentieva K Scott JM Molloy AM Rayman MP 《Molecular nutrition & food research》2008,52(11):1324-1333
The level of plasma total homocysteine (tHcy), long known to be B vitamin dependent, has recently been shown to be inversely associated with plasma selenium (Se) concentration in human subjects. We therefore, chose to investigate the interaction between Se, tHcy and B vitamins in a double-blind, placebo-controlled trial where 501 healthy UK elderly volunteers were randomly allocated to receive 100, 200, or 300 microg Se/day as high-Se-yeast, or placebo-yeast for 6 months. Plasma Se, tHcy, folate, vitamin B-12, pyridoxal-5'-phosphate (PLP) and its catabolite, 4-pyridoxic acid, were measured in all participants at baseline and in samples from the placebo, 100 and 300 microg Se/day groups, at follow-up. At baseline, Se was inversely correlated with tHcy but only in males (p < 0.001). Before supplementation, tHcy concentration was significantly lower in the highest compared to the lowest Se tertile in males (p < 0.05), and in females when folate concentrations were also in the top tertile (p < 0.05). The effect of folate, PLP and vitamin B-12 concentrations on plasma tHcy correlated with Se concentration at baseline. After 6 months of Se supplementation, only Se concentration had changed significantly. Supplementation with Se does not affect tHcy concentration in the UK elderly population. 相似文献
53.
54.
Crispie F Alonso-Gómez M O'Loughlin C Klostermann K Flynn J Arkins S Meaney W Paul Ross R Hill C 《The Journal of dairy research》2008,75(3):374-384
In the accompanying article, we demonstrated that a live culture of Lactococcus lactis compares favourably with antibiotics for treatment of bovine mastitis in two initial field trials. In an effort to explain the mechanism involved, this study investigated the effect of culture administration on the local immune response. In this respect we initially observed that infusion of the live culture Lactococcus lactis stimulated substantial recruitment of polymorphonucleocytes (PMN) and lymphocytes to the udder. For instance, in one assay, quarters infused with the probiotic experienced a dramatic increase (approximately 20,000-fold) in neutrophils over the first 48-h period from an average value of 83.6 cells/ml pre-treatment to 1.78 x 106 cells/ml 48 h post-infusion. Levels of the acute phase proteins haptaglobin and milk amyloid A were also elevated significantly in comparison with controls following infusion of the culture. The results of flow cytometric assays also demonstrated that while infusion of a live lactococcal culture led to an enhanced recruitment of PMN to the udder (from 1.85 x 104 cells/ml pre-infusion to 1.45 x 106 cells/ml 24 h post-infusion) cell-free supernatant from the same culture was not able to do so, indicating that live Lc. lactis can specifically trigger the mammary immune response to elicit PMN accumulation. These results suggest that the mechanism responsible for this probiotic treatment of mastitis is associated with stimulation of the host intramammary immune system. 相似文献
55.
56.
Complementary proteomic approaches reveal mitochondrial dysfunction,immune and inflammatory dysregulation in a mouse model of Gulf War Illness 下载免费PDF全文
57.
Thomas Seth Davis Fiona B. Horne Jens C. Yetter Jane E. Stewart 《Journal of chemical ecology》2018,44(6):601-610
Conifer secondary metabolites play a key role in mechanisms of resistance to biotic disturbance, especially by bark beetles and beetle-associated microorganisms. Here, we describe variation in constitutive monoterpenes isolated from Engelmann spruce, Picea engelmannii, phloem across fourteen high-elevation populations in the Rocky Mountains of Colorado, and test interactions between phloem monoterpenes and an endophloedic symbiotic fungus, Leptographium abietinum, associated with the North American spruce beetle, Dendroctonus rufipennis. We consistently identified ten monoterpenes in Engelmann spruce phloem, and the trees in our samples could be classified into two geographically interspersed chemical phenotypes, or ‘chemotypes’: one in which α- and β-pinene were the most abundant monoterpenes, and one in which 3-carene was the most abundant monoterpene. Media amended with low concentrations of α-pinene, β-pinene, 3-carene, myrcene, and terpinolene stimulated growth of L. abietinum. Increasing monoterpene concentrations uniformly retarded fungal growth. Linalool completely suppressed fungal growth at all concentrations, while terpinolene completely suppressed growth at low and intermediate concentrations, indicating relatively high toxicity of these compounds. Tests with monoterpene blends representing the ‘average’ monoterpene composition of each chemotype indicated that representative chemotypes are equivalent in fungistatic activity, with chemotype blends being inhibitory even at low concentrations. Total constitutive monoterpene abundances in Engelmann spruce phloem ranged from 42 to 1796 μg/g. Induction of Engelmann spruce phloem monoterpenes in response to L. abietinum or other biotic agents has yet to be quantified, but is important for further understanding Engelmann spruce resistance to the D. rufipennis-L. abietinum complex. 相似文献
58.
ABSTRACT Families are increasingly choosing to raise children in the growing number of private, high-rise apartment complexes developed in Australian capital cities. However, most of these developments have been designed for the childless and there are concerns as to how supportive these settings are for young children. This paper explores parents’ experiences of the environment surrounding their high-rise dwellings in an inner-city municipality of Melbourne, Australia using the participatory method, Photovoice. Ten parents photographed elements of their dwellings and environments that had positive or negative impacts on raising young children. Findings indicate that environments surrounding parents’ high-rise dwellings were used on a daily basis, often due to limited space within apartment complexes. However, aspects of this environment were challenging, requiring mutual accommodation between families and their immediate settings. This has implications for policy to ensure the neighbourhoods surrounding high-rise developments in inner-city areas are more child friendly. 相似文献
59.
Ljung K Torin A Smirk M Maley F Cook A Weinstein P 《The Science of the total environment》2008,407(1):589-593
Air quality is commonly assessed by the ambient concentration of airborne particles sized smaller than 10 microm (PM10). However, in addition to concentration, particle shape as well as the type and bioaccessibility of elements adsorbed to this particulate fraction are likely to be related to subsequent respiratory health effects. In order to investigate this relationship, a relatively large mass of the relevant size fraction is needed since sample preparation is necessary prior to analysis. Most existing methods for sampling dust have been developed for analysing the dust directly, without prior handling or digestion. In order to provide sufficient material to be used for subsequent bioaccessibility analysis, these methods require repetitive and time consuming sampling as well as special equipment and procedures which are high in both cost and maintenance. This paper describes an inexpensive and relatively simple procedure for extracting the PM10 fraction from soil to be used for lung bioaccessibility studies. The method described involves dry and wet sieving in order to exclude larger size fractions as far as possible. Vacuum filtering of the wet-sieved soil solution through a 10 microm mesh was then employed to extract the required fraction. In order to avoid frequent blocking of the mesh, Stokes's law was applied in the construction of a tube which enables separation of the solution holding the smallest fraction. 相似文献
60.
Bronwyn Isaac Raylene Cooke Dianne Simmons Fiona Hogan 《Landscape and urban planning》2008,84(3-4):212-218
Urban expansion is a principal process threatening biodiversity globally. It is predicted that over half of the world's population will reside in urban centres by 2010. If we are to conserve biodiversity, a shift in perspective from traditional ecological studies based in natural environments, to studies based in less natural environments is paramount. To effectively conserve species which occur in urban environments, comprehensive analysis is necessary to determine the processes that are driving this urban usage. Geographical Information Systems (GIS) technology provides a valuable tool for efficient spatial analysis and predictive mapping of species distributions.This study used GIS to analyze current breeding sites for the powerful owl, a vulnerable top order predator in urban Melbourne, Australia. GIS analysis suggests that a number of ecological attributes were influencing powerful owl usage of urban environments. Using these ecological attributes, predictive mapping was undertaken, which identified a number of potential breeding sites for powerful owls within urbanized Melbourne.Urban environments are traditionally perceived as “the wastelands” of natural environments, however, this study demonstrates that they have the potential to support apex predators, an important finding for the management of rare and threatened species. 相似文献