全文获取类型
收费全文 | 679篇 |
免费 | 4篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 68篇 |
金属工艺 | 4篇 |
机械仪表 | 1篇 |
建筑科学 | 27篇 |
能源动力 | 3篇 |
轻工业 | 29篇 |
水利工程 | 2篇 |
无线电 | 16篇 |
一般工业技术 | 24篇 |
冶金工业 | 485篇 |
自动化技术 | 23篇 |
出版年
2022年 | 3篇 |
2021年 | 4篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2013年 | 24篇 |
2012年 | 9篇 |
2011年 | 8篇 |
2010年 | 4篇 |
2009年 | 7篇 |
2008年 | 3篇 |
2007年 | 8篇 |
2006年 | 4篇 |
2004年 | 3篇 |
2002年 | 5篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1999年 | 24篇 |
1998年 | 176篇 |
1997年 | 81篇 |
1996年 | 48篇 |
1995年 | 36篇 |
1994年 | 21篇 |
1993年 | 28篇 |
1992年 | 11篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 6篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1977年 | 12篇 |
1976年 | 33篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1971年 | 2篇 |
1970年 | 2篇 |
1968年 | 3篇 |
1967年 | 3篇 |
1966年 | 4篇 |
1960年 | 2篇 |
1959年 | 2篇 |
1958年 | 2篇 |
排序方式: 共有683条查询结果,搜索用时 15 毫秒
41.
This article reports the proceedings of a workshop held on 3 June 2010, that aimed to establish a dialogue between historians
of agriculture and academics working in development studies. Including papers by historians from the Netherlands, Canada and
the UK, and a commentary from the development anthropologist, Paul Richards, the workshop identified a number of themes for
further investigation, and confirmed the value of continuing dialogue between historians and policy academics. 相似文献
42.
Bitterness is generally considered a negative attribute in food, yet many individuals enjoy some bitterness in products like coffee or chocolate. In chocolate, bitterness arises from naturally occurring alkaloids and phenolics found in cacao. Fermentation and roasting help develop typical chocolate flavor and reduce the intense bitterness of raw cacao by modifying these bitter compounds. As it becomes increasingly common to fortify chocolate with `raw' cacao to increase the amount of healthful phytonutrients, it is important to identify the point at which the concentration of bitter compounds becomes objectionable, even to those who enjoy some bitterness. Classical threshold methods focus on the presence or absence of a sensation rather than acceptability or hedonics. A new alternative, the rejection threshold, was recently described in the literature. Here, we sought to quantify and compare differences in Rejection Thresholds (RjT) and Detection Thresholds (DT) in chocolate milk spiked with a food safe bitterant (sucrose octaacetate). In experiment 1, a series of paired preference tests was used to estimate the RjT for bitterness in chocolate milk. In a new group of participants (experiment 2), we determined the RjT and DT using the forced choice ascending method of limits. In both studies, participants were segmented on the basis of self-declared preference for milk or dark solid chocolate. Based on sigmoid fits of the indifference-preference function, the RjT was ~2.3 times higher for those preferring dark chocolate than the RjT for those preferring milk chocolate in both experiments. In contrast, the DT for both groups was functionally identical, suggesting that differential effects of bitterness on liking of chocolate products are not based on the ability to detect bitterness in these products. 相似文献
43.
44.
45.
Ohya J. Kurumisawa J. Nakatsu R. Ebihara K. Iwasawa S. Harwood D. Horprasert T. 《Multimedia, IEEE》1999,6(2):29-39
The virtual metamorphosis system lets people change their forms into any other form in a virtual scene. To realize these changes, a computer vision system estimates facial expressions and body postures and reproduces them in a computer graphics avatar in real time. We introduce three systems in order of their development: the Virtual Kabuki system, Networked Theater and “Shall We Dance?” 相似文献
46.
47.
We report analysis of both inorganic and amino acid forms of selenium by ion chromatography with inductively coupled plasma atomic emission spectroscopic detection. Three chromatographic systems are compared; effects of representative sample matrices on the separations are investigated. We are unable to resolve selenate and seleno-cystine using the Dionex AS4A column. Elution of seleno-cystine and seleno-cysteine is strongly suppressed in samples of bacterial cell extract matrix analyzed with the Dionex AS10 column; this interference is not observed with the Dionex AS11 column. Synthetic sea water sample matrix has little effect on analytical results. Quantitation parameters are reported. 相似文献
48.
EH Herman J Zhang BB Hasinoff KT Tran DP Chadwick JR Clark VJ Ferrans 《Canadian Metallurgical Quarterly》1998,128(1):35-52
We have determined the time course, the spatial spread in brain tissue, and the intracellular distribution of biotin- and fluorescein-labeled phosphorothioate oligodeoxynucleotides (ODNs) following single injections into the rat striatum or the lateral ventricle. These time and space parameters were correlated with the ability of c-fos phosphorothioate antisense ODNs to suppress the induction of Fos protein by cocaine. A rapid and dose-dependent tissue penetration of labeled ODNs was observed following either intrastriatal or intraventricular injections of a constant sample volume. Inspection of tissue sections by confocal microscopy uncovered a distinct change in the intracellular disposition of labeled ODNs during the 24 h post-injection period. At 1, 6 and 12 h, the vast majority of the fluorescent signal was confined to the interstitial spaces throughout the zone penetrated by ODNs. Neuronal nuclei displayed faint labeling along the outer portion of the nucleus at 1 and 6 h post-injection. At these time-points, ODNs were not detected in the cytoplasm. By 16 h, ODNs were barely detectable in the extracellular space and absent from neuronal nuclei. Instead, ODNs were seen in large cytoplasmic granules of neurons throughout the tissue zone penetrated by the ODNs. Experiments with intrastriatal injections of antisense ODNs to c-fos mRNA revealed Fos suppression between 3 and 12 h, but not at 16 and 24 h. This combined analysis has revealed that (1) restricted tissue penetration by ODNs limits their antisense effects on protein expression, and (2) depletion of extracellular ODNs and sequestration of c-fos antisense ODNs into large intracellular granules coincides with the loss of their biological activity. 相似文献
49.
2-Ketocyclohexanecarboxyl coenzyme A (2-ketochc-CoA) hydrolase has been proposed to catalyze an unusual hydrolytic ring cleavage reaction as the last unique step in the pathway of anaerobic benzoate degradation by bacteria. This enzyme was purified from the phototrophic bacterium Rhodopseudomonas palustris by sequential Q-Sepharose, phenyl-Sepharose, gel filtration, and hydroxyapatite chromatography. The sequence of the 25 N-terminal amino acids of the purified hydrolase was identical to the deduced amino acid sequence of the badI gene, which is located in a cluster of genes involved in anaerobic degradation of aromatic acids. The deduced amino acid sequence of badI indicates that 2-ketochc-CoA hydrolase is a member of the crotonase superfamily of proteins. Purified BadI had a molecular mass of 35 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and a native molecular mass of 134 kDa as determined by gel filtration. This indicates that the native form of the enzyme is a homotetramer. The purified enzyme was insensitive to oxygen and catalyzed the hydration of 2-ketochc-CoA to yield pimelyl-CoA with a specific activity of 9.7 micromol min(-1) mg of protein(-1). Immunoblot analysis using polyclonal antiserum raised against the purified hydrolase showed that the synthesis of BadI is induced by growth on benzoate and other proposed benzoate pathway intermediates but not by growth on pimelate or succinate. An R. palustris mutant, carrying a chromosomal disruption of badI, did not grow with benzoate and other proposed benzoate pathway intermediates but had wild-type doubling times on pimelate and succinate. These data demonstrate that BadI, the 2-ketochc-CoA hydrolase, is essential for anaerobic benzoate metabolism by R. palustris. 相似文献
50.
VJ Di Maio 《Canadian Metallurgical Quarterly》1998,18(2):189-201
To investigate the roles of astroglial cells, we targeted their ablation genetically. Transgenic mice were generated expressing herpes simplex virus thymidine kinase from the mouse glial fibrillary acidic protein (GFAP) promoter. In adult transgenic mice, 2 weeks of subcutaneous treatment with the antiviral agent ganciclovir preferentially ablated transgene-expressing, GFAP-positive glia from the jejunum and ileum, causing a fulminating and fatal jejuno-ileitis. This pathology was independent of bacterial overgrowth and was characterized by increased myeloperoxidase activity, moderate degeneration of myenteric neurons, and intraluminal hemorrhage. These findings demonstrate that enteric glia play an essential role in maintaining the integrity of the bowel and suggest that their loss or dysfunction may contribute to the cellular mechanisms of inflammatory bowel disease. 相似文献