全文获取类型
收费全文 | 402篇 |
免费 | 10篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 3篇 |
综合类 | 3篇 |
化学工业 | 28篇 |
金属工艺 | 4篇 |
机械仪表 | 18篇 |
建筑科学 | 42篇 |
矿业工程 | 2篇 |
轻工业 | 85篇 |
水利工程 | 2篇 |
石油天然气 | 27篇 |
武器工业 | 3篇 |
无线电 | 21篇 |
一般工业技术 | 141篇 |
冶金工业 | 2篇 |
自动化技术 | 35篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 4篇 |
2020年 | 5篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 1篇 |
2015年 | 2篇 |
2014年 | 7篇 |
2013年 | 1篇 |
2012年 | 29篇 |
2011年 | 29篇 |
2010年 | 6篇 |
2009年 | 4篇 |
2008年 | 34篇 |
2007年 | 35篇 |
2006年 | 15篇 |
2005年 | 40篇 |
2004年 | 13篇 |
2003年 | 10篇 |
2002年 | 6篇 |
2001年 | 9篇 |
2000年 | 22篇 |
1999年 | 10篇 |
1998年 | 11篇 |
1997年 | 7篇 |
1996年 | 12篇 |
1995年 | 11篇 |
1994年 | 11篇 |
1993年 | 7篇 |
1992年 | 2篇 |
1991年 | 8篇 |
1990年 | 8篇 |
1989年 | 6篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 4篇 |
1972年 | 2篇 |
排序方式: 共有416条查询结果,搜索用时 15 毫秒
51.
Janczyk P Trevisi P Souffrant WB Bosi P 《International journal of food microbiology》2008,126(1-2):258-261
Thirty two weaned pigs (24 d-old) were fed a diet without or with 1% (w/w) thymol. Pigs from each dietary treatment remained unchallenged or were challenged with Salmonella enterica serovar typhimurium. Jejunal content was collected and molecular microbial diversity was investigated using 16S rRNA gene polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). Shannon index analysis showed no differences in diversity but Pearson coefficient analysis showed clear clustering of profiles, which delineated thymol fed and control groups irrespective of Salmonella challenge. Moreover, absence of bands corresponding to Actinobacillus minor (98-99% identity) was observed in thymol groups. A band corresponding to Citrobacter freundii (98% identity) was observed in almost all pigs from thymol groups, and only in 4 samples from pigs fed no thymol in the diet. Supplementation of pig diet with thymol caused clear changes in small intestine microbacterial community. Surprisingly, Salmonella infection caused no major perturbations to the community structure. 相似文献
52.
We report observation of fluorescence from individual rhodamine 6G molecules in streams of charged 1-μm-diameter water droplets. With this approach, illumination volumes comparable to diffraction-limited fluorescence microscopy techniques (≤500 aL) are achieved, resulting in similarly high contrast between single-molecule fluorescence signals and nonfluorescent background. However, since the fluorescent molecules are confined to electrically charged droplets, in situ electrodynamic manipulation (e.g., focusing, switching, or merging) can be accomplished in a straightforward manner, allowing experimental control over both the delivery of molecules of interest to the observation region and the laser-molecule interaction time. As illustrated by photocount statistics that are independent of molecular diffusion and spatial characteristics of the excitation field, individual rhodamine 6G molecules in 1-μm droplets are reproducibly delivered to a target a few micrometers in diameter at a rate of between 10 and 100 Hz, with laser beam transit times more than 1 order of magnitude longer than diffusion-limited laser-molecule interaction times in equivalent volumes of free solution. 相似文献
53.
The collection of fluorescence from a molecule inside a sphere illuminated with single or counterpropagating plane waves is modeled. The results are applicable to microdroplet-based single molecule detection techniques and to some microparticle characterization techniques using inelastic emission. The large position-dependent variations in the fluorescence collection rate are primarily attributable to variations in the excitation intensity. With plane-wave illumination the collection from shadow regions is low because the incident energy is refracted by the droplet surface away from these regions. The average collection rate from molecules in shadow regions can be increased by illuminating with counterpropagating beams. 相似文献
54.
Effect of watershed parameters on mercury distribution in different environmental compartments in the Mobile Alabama River Basin, USA 总被引:1,自引:0,他引:1
Warner KA Bonzongo JC Roden EE Ward GM Green AC Chaubey I Lyons WB Arrington DA 《The Science of the total environment》2005,347(1-3):187-207
Total mercury (THg) and mono-methylmercury (MeHg) levels in water, sediment, and largemouth bass (LMB) (Micropterus salmoides) were investigated at 52 sites draining contrasting land use/land cover and habitat types within the Mobile Alabama River Basin (MARB). Aqueous THg was positively associated with iron-rich suspended particles and highest in catchments impacted by agriculture. Sediment THg was positively associated with sediment organic mater and iron content, with the highest levels observed in smaller catchments influenced by wetlands, followed by those impacted by agriculture or mixed forest, agriculture, and wetlands. The lowest sediment THg levels were observed in main river channels, except for reaches impacted by coal mining. Sediment MeHg levels were a positive function of sediment THg and organic matter and aqueous nutrient levels. The highest levels occurred in agricultural catchments and those impacted by elevated sulfate levels associated with coal mining. Aqueous MeHg concentrations in main river channels were as high as those in smaller catchments impacted by agriculture or wetlands, suggesting these areas were sources to rivers. Elevated Hg levels in some LMB were observed across all types of land use and land cover, but factors such as shallow water depth, larger wetland catchment surface area, low aqueous potassium levels, and higher Chl a concentrations were associated with higher Hg burdens, particularly in the Coastal Plain province. It is suggested that the observed large variability in LMB Hg burdens is linked to fish displacement by anglers, differences in food web structure, and sediment biogeochemistry, with surficial sediment iron oxides buffering the flux of MeHg from sediments to deeper water pelagic food webs. 相似文献
55.
56.
本文回顾了南昌大学图文信息中心的设计过程。通过对项目背景、总图关系、功能空间形态、建筑形态等方面的介绍,探讨了当代高校图书馆的内涵和外延所发生的一些新的变化,指出了从读书行为到信息交流的转变是促使图书馆新形态产生的直接原动力。 相似文献
57.
We present a system for analyzing the assembly pathway of DNA nanostructures. This enables the identification, explanation, and avoidance of obstacles to proper structure formation. Potential problems include strand end-pinning and misfolding caused by the structural bias of nominally flexible junctions. We have used this system to guide the construction of parallel motifs that had previously, for unknown reasons, resisted assembly. 相似文献
58.
Closed-loop, multiobjective optimization of two-dimensional gas chromatography/mass spectrometry for serum metabolomics 总被引:4,自引:0,他引:4
O'Hagan S Dunn WB Knowles JD Broadhurst D Williams R Ashworth JJ Cameron M Kell DB 《Analytical chemistry》2007,79(2):464-476
Metabolomics seeks to measure potentially all the metabolites in a biological sample, and consequently, we need to develop and optimize methods to increase significantly the number of metabolites we can detect. We extended the closed-loop (iterative, automated) optimization system that we had previously developed for one-dimensional GC-TOF-MS (O'Hagan, S.; Dunn, W. B.; Brown, M.; Knowles, J. D.; Kell, D. B. Anal. Chem. 2005, 77, 290-303) to comprehensive two-dimensional (GCxGC) chromatography. The heuristic approach used was a multiobjective version of the efficient global optimization algorithm. In just 300 automated runs, we improved the number of metabolites observable relative to those in 1D GC by some 3-fold. The optimized conditions allowed for the detection of over 4000 raw peaks, of which some 1800 were considered to be real metabolite peaks and not impurities or peaks with a signal/noise ratio of less than 5. A variety of computational methods served to explain the basis for the improvement. This closed-loop optimization strategy is a generic and powerful approach for the optimization of any analytical instrumentation. 相似文献
59.
A cost-effective optical cancer screening and monitoring technique was demonstrated in a pilot study of canine serum samples and was patented for commercialization. Compared to conventional blood chemistry analysis methods, more accurate estimations of the concentrations of albumin, globulins, and hemoglobin in serum were obtained by fitting the near UV absorbance and photoluminescence spectra of diluted serum as a linear combination of component reference spectra. Tracking these serum proteins over the course of treatment helped to monitor patient immune response to carcinoma and therapy. For cancer screening, 70% of dogs with clinical presentation of cancer displayed suppressed serum hemoglobin levels (below 20 mg/dL) in combination with atypical serum protein compositions, that is, albumin levels outside of a safe range (from 4 to 8 g/dL) and globulin levels above or below a more normal range (from 1.7 to 3.7 g/dL). Of the dogs that met these criteria, only 20% were given a false positive label by this cancer screening test. 相似文献
60.
Quadratic correlation filters (QCFs) have been used successfully to detect and recognize targets embedded in background clutter. Recently, a QCF called the Rayleigh quotient quadratic correlation filter (RQQCF) was formulated for automatic target recognition (ATR) in IR imagery. Using training images from target and clutter classes, the RQQCF explicitly maximized a class separation metric. What we believe to be a novel approach is presented for ATR that synthesizes the RQQCF using compressed images. The proposed approach considerably reduces the computational complexity and storage requirements while retaining the high recognition accuracy of the original RQQCF technique. The advantages of the proposed scheme are illustrated using sample results obtained from experiments on IR imagery. 相似文献