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   4505篇
  免费   359篇
  国内免费   6篇
电工技术   38篇
综合类   4篇
化学工业   1064篇
金属工艺   61篇
机械仪表   101篇
建筑科学   156篇
矿业工程   6篇
能源动力   130篇
轻工业   870篇
水利工程   64篇
石油天然气   16篇
无线电   220篇
一般工业技术   673篇
冶金工业   788篇
原子能技术   5篇
自动化技术   674篇
  2024年   17篇
  2023年   51篇
  2022年   106篇
  2021年   173篇
  2020年   119篇
  2019年   148篇
  2018年   206篇
  2017年   210篇
  2016年   240篇
  2015年   175篇
  2014年   189篇
  2013年   362篇
  2012年   304篇
  2011年   362篇
  2010年   219篇
  2009年   189篇
  2008年   181篇
  2007年   204篇
  2006年   120篇
  2005年   93篇
  2004年   87篇
  2003年   80篇
  2002年   94篇
  2001年   51篇
  2000年   39篇
  1999年   50篇
  1998年   281篇
  1997年   166篇
  1996年   106篇
  1995年   50篇
  1994年   35篇
  1993年   40篇
  1992年   9篇
  1991年   15篇
  1990年   8篇
  1989年   5篇
  1988年   9篇
  1987年   8篇
  1986年   3篇
  1985年   10篇
  1984年   4篇
  1983年   2篇
  1981年   7篇
  1980年   5篇
  1978年   6篇
  1977年   7篇
  1976年   23篇
  1973年   1篇
  1969年   1篇
排序方式: 共有4870条查询结果,搜索用时 15 毫秒
71.
The moderate consumption of red wine has been proposed to reduce the incidence of colorectal cancer. Its anti-cancer action my in part be mediated by the actions of polyphenols on colon cancer epithelial cells. We show that a red wine phenolic (50 μg/ml) extract devoid of anthocyanins (removed to reflect polyphenol bioavailability to the large intestine) and the major red wine flavonols quercetin, myricetin, laricitrin and syringetin (50 μM) are capable of inhibiting the proliferation of colorectal epithelial adenocarcinoma cells. This anti-proliferative activity was partly mediated by the direct cytotoxic actions of flavonols and also their ability to cause a significant cell cycle blockage in G2/M. The anti-proliferative effects induced by flavonols were preceded, in most cases, by a strong and significant reduction of cyclooxygenase-2 (COX-2) and cyclin D1 expression. These results indicate that the observed inverse correlation between colon cancer and a moderate red wine intake may be partly mediated by the actions of red wine flavonols on the growth of cancer cells.  相似文献   
72.
73.
74.
75.
76.
Goldenberry is a wild fruit that has been widely used for centuries, mainly in folk medicine. Most studies of goldenberry have focused on the fruit, but new research has studied its byproducts, which were considered to be waste until recently. The main objective of our study was to systematize the published information regarding the composition of goldenberry byproducts (calyces, leaves, seeds, and pomace) and their effects on biological systems. Goldenberry byproducts contain minerals, amino acids, withanolides, flavonoids, and essential fatty acids, thus representing good sources of these compounds. Some of their major biological effects include anti-inflammatory, antioxidant, antidiabetic, and antiproliferative effects. Information regarding their toxicity is also presented here. To determine the optimal dosage, further safety studies would be recommended to ensure the best health benefits of these compounds. The available evidence has demonstrated the nutritional value of different byproducts of goldenberry, suggesting them to be potential candidates for use in the cosmetic industry, in the preparation of functional foods, and in phytomedicine for the prevention and adjuvant treatment of some diseases. © 2020 Society of Chemical Industry  相似文献   
77.
78.
Thirty-two lambs were finished on a total mixed ration (TMR) pelleted alone (00SS) or including sunflower soap stock (SS): 15SS (15 g SS per kg TMR), 30SS (30 g SS per kg TMR) and 60SS (60 g SS per kg TMR). Lambs (8 per group) were slaughtered at 27 kg live weight. Colour evolution, lipid oxidation, microbial growth and detection of diarrhoeagenic Escherichia coli were studied in meat samples. SS in the diet reduced meat lipid oxidation (< 0.05), but had no significant effect (P > 0.05) on the cholesterol oxidation products. Meat from 60SS and control animals (00SS) revealed greater discoloration (< 0.05) than 15SS. SS supplementation did not affect the microbiological populations, whereas high doses of SS seemed to increase the proliferation of diarrhoeagenic E. coli on day 14 (< 0.10). These results suggest that the rate of SS inclusion in the diet of fattening lambs should not be above 15 g SS per kg TMR.  相似文献   
79.
Staphylococcus species, categorized into Staphylococcus aureus and non-aureus staphylococci (NAS), are frequent causes of mastitis in dairy cattle around the world. Current treatments using antimicrobials are under increasing scrutiny due to rising prevalence of multi-drug resistance in S. aureus. Objectives of this study were to determine: (1) genetic diversity of Staphylococcus species isolated from clinical mastitis in cows from large Chinese dairy farms; and (2) prevalence and distribution of antimicrobial resistance genes (ARG) in these isolates. Staphylococcus aureus (n = 96) were isolated from 26 herds located in 12 provinces of China, whereas NAS (n = 112) were isolated from 59 herds located in 18 provinces of China. The NAS were identified at the species level using a partial 16S rRNA sequencing method, whereas random amplification of polymorphic DNA (RAPD) PCR was done to determine genetic relationships of isolates. Finally, PCR was used to detect resistance and biofilm formation genes. Staphylococcus chromogenes (33%) was the most common NAS species, followed by Staphylococcus sciuri (17%) and Staphylococcus epidermidis (8%). Staphylococcus aureus was grouped in 12 genotypes, of which 2 types represented 56% of isolates. Staphylococcus chromogenes (n = 37) clustered into 8 RAPD types, with 2 prevalent types containing 73% of isolates. The most prevalent ARG in S. aureus isolates was blaZ (95%), followed by tetM (33%), tetK (31%), ermT (26%), and aacA-aphD (23%). The mecA and vanA were detected in 16 and 4% of isolates, respectively. In NAS, blaZ (100%), mecA (73%), tetK (79%), tetM (96%), mphC (63%), and msrA (54%) were frequently detected. Antimicrobial resistance genes mecA, tetK, tetL, tetM, dfrG, ermB, msrA, mphC, aadD, and aphA3 were more commonly detected in NAS than in S. aureus. Biofilm formation genes (icaA and icaD) were frequently detected in staphylococci isolated from bovine clinical mastitis. The existence of predominant RAPD types in S. aureus and S. chromogenes isolates across Chinese dairy farms indicated that specific genotypes had disseminated within herds and become more udder-adapted. High prevalence of ARG, especially in NAS, highlighted the risk of selection of multi-drug resistant staphylococci with potential as a reservoir of ARG.  相似文献   
80.
The probiotic strains Lactobacillus brevis CCMA1284 and Lactobacillus plantarum CCMA0359 were microencapsulated by spray drying using different matrices – whey powder (W), whey powder with inulin (WI) and whey powder with maltodextrin (WM). Viability of the microencapsulated strains in acid and bile juices and during 90 days of storage (seven and 25 °C) was evaluated. The two strains exhibited high encapsulation efficiency (> 86%) by spray drying. The different matrices maintained L. plantarum viability above six log CFU g−1 at 7 °C for 90 days, whereas similar results for L. brevis were observed only for W. The use of inulin as matrix of encapsulation did not enhance bacterial viability in the evaluated conditions. In general, the use of W and WM as matrices was effective for L. plantarum viability. However, only W was effective for L. brevis in the evaluated conditions. The spray drying technique was successfully adopted for the encapsulation of L. plantarum CCMA0359 and L. brevis CCMA1284 strains.  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