首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   715篇
  免费   22篇
电工技术   13篇
综合类   1篇
化学工业   182篇
金属工艺   27篇
机械仪表   29篇
建筑科学   35篇
矿业工程   12篇
能源动力   19篇
轻工业   58篇
水利工程   6篇
石油天然气   1篇
无线电   35篇
一般工业技术   94篇
冶金工业   116篇
原子能技术   2篇
自动化技术   107篇
  2023年   9篇
  2022年   32篇
  2021年   28篇
  2020年   16篇
  2019年   17篇
  2018年   12篇
  2017年   11篇
  2016年   18篇
  2015年   19篇
  2014年   34篇
  2013年   53篇
  2012年   34篇
  2011年   48篇
  2010年   44篇
  2009年   26篇
  2008年   29篇
  2007年   31篇
  2006年   33篇
  2005年   13篇
  2004年   20篇
  2003年   13篇
  2002年   16篇
  2001年   16篇
  2000年   11篇
  1999年   13篇
  1998年   9篇
  1997年   11篇
  1996年   5篇
  1995年   6篇
  1994年   5篇
  1993年   10篇
  1992年   11篇
  1991年   4篇
  1990年   5篇
  1987年   4篇
  1986年   8篇
  1985年   4篇
  1984年   3篇
  1983年   3篇
  1982年   7篇
  1981年   10篇
  1979年   4篇
  1978年   3篇
  1977年   5篇
  1976年   2篇
  1975年   3篇
  1974年   3篇
  1961年   2篇
  1960年   2篇
  1959年   2篇
排序方式: 共有737条查询结果,搜索用时 11 毫秒
11.
12.
Preharvest contamination of field crops may have many sources, including feces, soil, and irrigation water. In March 2000, a sewage spill released unchlorinated tertiary-treated effluent into a creek used to irrigate commercial produce. A field of young cabbage transplants was irrigated with creek water as the contaminated water flowed past this land. Cabbage samples were taken from plots within this field, and Escherichia coli was isolated from the roots of these plants but not from the edible portion of the cabbage. No E. coli was isolated from water samples or from control samples taken from a nearby cabbage field watered with chlorinated municipal water. The cabbage field under study had not been fertilized with manure for at least 2 years prior to the contamination incident. Six different E. coli serotypes were identified, although none of them proved to be pathogenic. These serotypes were separated into five groups by a RiboPrinter; the resulting groups correlated well with the serotypes and the locations in the field from which these strains were isolated. We previously found that certain nonpathogenic E. coli strains displayed lower levels of adherence to lettuce seedling roots in a hydroponic adherence assay. The E. coli field strains displayed variable patterns of adherence to lettuce seedlings: strain MW421 showed significantly lower root and shoot adherence levels than did the other field strains, while strains MW423 and MW425 showed significantly higher root and shoot adherence levels. These data suggest that water quality is of paramount importance for the food safety of growing crops.  相似文献   
13.
14.
Experimental breads were made with 2, 4, 6, 8, 10, and 12% torula yeast flour (TYF). Taste panels found that bread fortified with 8% TYF was acceptable. Eight percent TYF raised protein content from 12.42% for all wheat flour bread to 14.22% for supplemented bread. Amino acid analyses indicated a marked increase in amino acid content especially lysine. The protein efficiency ratio (PER) for rats on all-wheat-flour bread was 1.3 1; replacing 8% of the wheat flour with TYF raised PER of supplemented bread to 2.28. Total carcass nitrogen retained by animals fed a diet containing supplemented bread was higher than that retained by rats whose protein was obtained from unsupplemented bread.  相似文献   
15.
BACKGROUND: In this study the effects of pulsed electric field (PEF) pretreatment were evaluated during drying and rehydration of carrots. Carrots pretreated with an electric field intensity of 1 kV cm?1 (capacitance 0.5 µF, 20 pulses) or 1.5 kV cm?1 (capacitance 1 µF, 20 pulses) as well as blanched (100 °C, 3 min) carrots were used for the study. Following pretreatment, samples were oven dried at 70 °C and then rehydrated in distilled water (1:30 w/v) at room temperature (24 ± 1 °C). RESULTS: PEF pretreatment increased the drying rate of carrots. However, the rehydration rate of PEF‐pretreated carrots was lower than that of blanched carrots. There were no colour differences between PEF‐pretreated and blanched carrots before drying and after rehydration. In terms of texture, PEF‐pretreated carrots were firmer than blanched carrots. PEF pretreatment reduced the activity of peroxidase by 30–50%, while blanching completely inactivated the enzyme (>95%). CONCLUSIONS: Overall, the results suggest that PEF could be an effective pretreatment during drying and rehydration of carrots. Copyright © 2009 Society of Chemical Industry  相似文献   
16.
Millets are generally dehulled and subjected to a hydrothermal treatment before consumption, thus the hulls can be used as a potential source of antioxidants. Several millet grains, namely kodo, finger (Ravi), finger (local), proso, foxtail, little and pearl millet were studied. Antioxidant activities of phenolic extracts obtained from whole grains, as well as their corresponding dehulled and cooked grains and hulls were studied for their total phenolic content (TPC), radical scavenging capacity, and antioxidant activity in a β-carotene/linoleate emulsion. The phenolics present in whole grains were identified and quantified using HPLC and HPLC/MS and results were expressed as total for each of the phenolic groups. The TPC ranged from 2 to 112 μmol ferulic acid equivalents/g defatted meal. All varieties exhibited effective inhibition of 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl, peroxyl and superoxide radicals. Dehulling and cooking affected the TPC and radical scavenging and antioxidant activities of the grains, depending on the variety. In general, the antioxidant activity of phenolic extracts was in the order of hull > whole grain > dehulled grain > cooked dehulled grain With the exception of the two finger millet varieties, hulls of other millet grains had high TPC, thus demonstrating their superior antioxidant activity. Hydroxybenzoic acids, hydroxycinnamic acids and flavonoids in whole grains were identified as contributors to the observed effects. Therefore, dehulling of grain and hydrothermal treatments affect the phenolic content and antioxidant potential of millet grains.  相似文献   
17.
18.
19.
Diamond-Blackfan anaemia (DBA) is a red blood cell aplasia that in the majority of cases is associated with ribosomal protein (RP) aberrations. However, the mechanism by which this disorder leads to such a specific phenotype remains unclear. Even more elusive is the reason why non-specific agents such as glucocorticosteroids (GCs), also known as glucocorticoids, are an effective therapy for DBA. In this review, we (1) explore why GCs are successful in DBA treatment, (2) discuss the effect of GCs on erythropoiesis, and (3) summarise the GC impact on crucial pathways deregulated in DBA. Furthermore, we show that GCs do not regulate DBA erythropoiesis via a single mechanism but more likely via several interdependent pathways.  相似文献   
20.
This article examines the presence of the empirical tendency known as the Menzerath–Altmann Law (MAL) on protein secondary structures. MAL is related to optimization principles observed in natural languages and in genetic information on chromosomes or protein domains. The presence of MAL is examined on a non-redundant dataset of 4728 proteins by verifying significant, negative correlations and testing classical and newly proposed formulas by fitting the observed trend. We conclude that the lengths of secondary structures are specifically dependent on their number inside the protein sequence, while possibly reflecting the formula proposed in this paper. This behavior is observed on average but is individually avoidable and possibly driven by a latent cost function. The data suggest that MAL could provide a useful guiding principle in protein design.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号