全文获取类型
收费全文 | 1494篇 |
免费 | 88篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 13篇 |
综合类 | 4篇 |
化学工业 | 319篇 |
金属工艺 | 15篇 |
机械仪表 | 33篇 |
建筑科学 | 73篇 |
矿业工程 | 1篇 |
能源动力 | 38篇 |
轻工业 | 317篇 |
水利工程 | 9篇 |
石油天然气 | 7篇 |
无线电 | 76篇 |
一般工业技术 | 223篇 |
冶金工业 | 268篇 |
原子能技术 | 11篇 |
自动化技术 | 180篇 |
出版年
2024年 | 5篇 |
2023年 | 20篇 |
2022年 | 38篇 |
2021年 | 59篇 |
2020年 | 35篇 |
2019年 | 37篇 |
2018年 | 40篇 |
2017年 | 55篇 |
2016年 | 54篇 |
2015年 | 42篇 |
2014年 | 55篇 |
2013年 | 93篇 |
2012年 | 81篇 |
2011年 | 126篇 |
2010年 | 69篇 |
2009年 | 69篇 |
2008年 | 86篇 |
2007年 | 73篇 |
2006年 | 61篇 |
2005年 | 56篇 |
2004年 | 47篇 |
2003年 | 30篇 |
2002年 | 47篇 |
2001年 | 32篇 |
2000年 | 22篇 |
1999年 | 20篇 |
1998年 | 35篇 |
1997年 | 43篇 |
1996年 | 25篇 |
1995年 | 14篇 |
1994年 | 16篇 |
1993年 | 9篇 |
1992年 | 12篇 |
1991年 | 8篇 |
1990年 | 10篇 |
1989年 | 9篇 |
1988年 | 8篇 |
1987年 | 4篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1981年 | 4篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1973年 | 2篇 |
排序方式: 共有1587条查询结果,搜索用时 15 毫秒
261.
262.
Evangelia Komitopoulou Ioannis S. Boziaris E. Alison Davies Joss Delves-Broughton &Martin R. Adams 《International Journal of Food Science & Technology》1999,34(1):81-85
Summary The acid-tolerant and heat-resistant bacterium Alicyclobacillus acidoterrestris is a spoilage problem in pasteurized and heat-treated fruit juices. In this study it was shown to grow in orange juice, grapefruit juice and apple juice to produce detectable taint at levels of about 104 –105 c.f.u. ml−1 . Decimal reduction times were determined at 80 °, 90 ° and 95 °C in each juice and confirmed the heat-resistant nature of the spores under normal juice pasteurization conditions. They also confirmed that heat sensitivity increased with decreasing pH but that this effect was less pronounced at higher temperatures. The organism was, however, sensitive to the bacteriocin food preservative nisin. The presence of nisin during heating decreased the D value by up to 40% and the MIC for nisin against spores at 25 °C was only 5 International Units (IU) ml−1 . The results indicate that use of nisin is a potentially useful way of controlling this organism in fruit juices and fruit juice-containing products. 相似文献
263.
Carl R. Dahlen Pawel P. Borowicz Alison K. Ward Joel S. Caton Marta Czernik Luca Palazzese Pasqualino Loi Lawrence P. Reynolds 《International journal of molecular sciences》2021,22(21)
Assisted reproductive techniques (ART) and parental nutritional status have profound effects on embryonic/fetal and placental development, which are probably mediated via “programming” of gene expression, as reflected by changes in their epigenetic landscape. Such epigenetic changes may underlie programming of growth, development, and function of fetal organs later in pregnancy and the offspring postnatally, and potentially lead to long-term changes in organ structure and function in the offspring as adults. This latter concept has been termed developmental origins of health and disease (DOHaD), or simply developmental programming, which has emerged as a major health issue in animals and humans because it is associated with an increased risk of non-communicable diseases in the offspring, including metabolic, behavioral, and reproductive dysfunction. In this review, we will briefly introduce the concept of developmental programming and its relationship to epigenetics. We will then discuss evidence that ART and periconceptual maternal and paternal nutrition may lead to epigenetic alterations very early in pregnancy, and how each pregnancy experiences developmental programming based on signals received by and from the dam. Lastly, we will discuss current research on strategies designed to overcome or minimize the negative consequences or, conversely, to maximize the positive aspects of developmental programming. 相似文献
264.
Elcio Ferreira Frota Vanine V. Silva de Barros Brenda R.S. de Araújo Ângelo Gonzaga Purgatto José J. Linares 《International Journal of Hydrogen Energy》2017,42(36):23095-23106
This study shows the influence of the Pt percentage in Pt catalysts (Pt/C) on their application in Direct Glycerol Fuel Cells (DGFC). Catalysts with 20, 30, 40 and 60% Pt were prepared by formic acid reduction. X-Ray Diffraction (XRD) confirmed the formation of Pt fcc nanocrystals (with average sizes between 3 and 4 nm). Thermogravimetric analysis (TGA) corroborated the Pt loadings and the Transmission Electron Microscopy (TEM) images show a homogeneous distribution of the Pt nanoparticles, with larger particles at higher Pt percentages. Electrochemical measurements reveal that higher Pt percentages promote the activity of the glycerol electroxidation reaction, resulting in lower onset potentials, higher current densities and reduced poisoning of the Pt surface. Single cell tests confirm these results, with greater maximum power density at higher Pt percentages, although the glycerol crossover effect starts to become significant in the 60% Pt/C catalyst, owing to the reduced thickness of this catalytic layer. A final product selectivity analysis indicates that tartronate is the preferential glycerol electroxidation product, along with glycerate and oxalate in lower proportions, with minor amounts of glycolate and mesoxalate. In general, a thicker catalytic layer is associated with the formation of more oxidized products. 相似文献
265.
Prsio Leister de Almeida Barros Euclides de Mesquita Neto 《International journal for numerical methods in engineering》2000,47(5):951-967
A method of interpolation of the boundary variables that uses spline functions associated with singular elements is presented. This method can be used in boundary element method analysis of 2‐D problems that have points where the boundary variables present singular behaviour. Singular‐ended splines based on cubic splines and Overhauser splines are developed. The former provides C2‐continuity and the latter C1‐continuity across element edges. The potentialities of the methodology are demonstrated analysing the dynamic response of a 2‐D rigid footing interacting with a half‐space. It is shown that, for a given number of elements at the soil–foundation interface, the singular‐ended spline interpolation increases substantially the displacement convergence rate and delivers smoother traction distributions. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
266.
267.
Lucas Wauters Raúl Y. Tito Matthias Ceulemans Maarten Lambaerts Alison Accarie Leen Rymenans Chloë Verspecht Joran Toth Raf Mols Patrick Augustijns Jan Tack Tim Vanuytsel Jeroen Raes 《International journal of molecular sciences》2021,22(24)
Proton pump inhibitors (PPI) may improve symptoms in functional dyspepsia (FD) through duodenal eosinophil-reducing effects. However, the contribution of the microbiome to FD symptoms and its interaction with PPI remains elusive. Aseptic duodenal brushings and biopsies were performed before and after PPI intake (4 weeks Pantoprazole 40 mg daily, FD-starters and controls) or withdrawal (2 months, FD-stoppers) for 16S-rRNA sequencing. Between- and within-group changes in genera or diversity and associations with symptoms or duodenal factors were analyzed. In total, 30 controls, 28 FD-starters and 19 FD-stoppers were followed. Mucus-associated Porphyromonas was lower in FD-starters vs. controls and correlated with symptoms in FD and duodenal eosinophils in both groups, while Streptococcus correlated with eosinophils in controls. Although clinical and eosinophil-reducing effects of PPI therapy were unrelated to microbiota changes in FD-starters, increased Streptococcus was associated with duodenal PPI effects in controls and remained higher despite withdrawal of long-term PPI therapy in FD-stoppers. Thus, duodenal microbiome analysis demonstrated differential mucus-associated genera, with a potential role of Porphyromonas in FD pathophysiology. While beneficial effects of short-term PPI therapy were not associated with microbial changes in FD-starters, increased Streptococcus and its association with PPIeffects in controls suggest a role for duodenal dysbiosis after long-term PPI therapy. 相似文献
268.
Phytoplankton were sampled fortnightly in summer and monthly in winter for 33 months to determine temporal and spatial variations in taxonomic structure and relate these to the physical and chemical environment. Using canonical correspondence analysis, environmental variables selected by stepwise regression were found to be correlated with the major variable(s) determining phytoplankton composition. An improved proportion of explained variance was achieved by classifying data into three seasonal subsets. The highest percentage of explained variance in phytoplankton composition was achieved for the months March to May (36·5%), the lowest variance explained was for the period June to September (28·6%). Within each season, general linear modelling was used to predict taxa responses to variations in particular environmental variables. Taxa responses to discharge are presented as examples for determining river management policies. The rationale of conceptual models and the empirical models used for this study are discussed. © 1997 John Wiley & Sons, Ltd. 相似文献
269.
Helen Sheldon John Alexander Esther Bridges Lucia Moreira Svetlana Reilly Koon Hwee Ang Dian Wang Salwa Lin Syed Haider Alison H. Banham Adrian L. Harris 《International journal of molecular sciences》2021,22(20)
ELTD1 is expressed in endothelial and vascular smooth muscle cells and has a role in angiogenesis. It has been classified as an adhesion GPCR, but as yet, no ligand has been identified and its function remains unknown. To establish its role, ELTD1 was overexpressed in endothelial cells. Expression and consequently ligand independent activation of ELTD1 results in endothelial-mesenchymal transistion (EndMT) with a loss of cell-cell contact, formation of stress fibres and mature focal adhesions and an increased expression of smooth muscle actin. The effect was pro-angiogenic, increasing Matrigel network formation and endothelial sprouting. RNA-Seq analysis after the cells had undergone EndMT revealed large increases in chemokines and cytokines involved in regulating immune response. Gene set enrichment analysis of the data identified a number of pathways involved in myofibroblast biology suggesting that the endothelial cells had undergone a type II EMT. This type of EMT is involved in wound repair and is closely associated with inflammation implicating ELTD1 in these processes. 相似文献
270.
Glen Fox Alison Kelly Jan Bowman Andy Inkerman David Poulsen Robert Henry 《Journal of the Institute of Brewing》2009,115(2):95-104
Barley grain from a combined intermediate and advanced barley breeding trial was assessed for grain, feed and malt quality from two sites over two consecutive years, with the objective to ascertain relationships between these traits. Results indicated there were genetic effects for both malt (hot water extract and friability) and “feed” traits (as measured by hardness, acid detergent fibre, starch and in‐sacco dry matter digestibility). The feed trait values were generally independent of the malt trait values. However, there were positive relationships between friability, hardness and protein, as well as a negative relationship between extract and husk. Extract also had a positive relationship with test weight but appeared to be independent from the feed traits. Test weight also showed little relationship to the feed traits. Heritability values ranged from low to high for almost all traits. This study details where both malt and cattle feed parameters have been compared and the results indicated that while malt and feed traits do not correlate directly, malt cultivars can exhibit excellent feed characteristics, equal to or better than feed cultivars. This data highlights the benefit of selecting for malt quality even if a breeding program would be interested at targeting specific feed quality. 相似文献