全文获取类型
收费全文 | 693篇 |
免费 | 77篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 2篇 |
综合类 | 29篇 |
化学工业 | 265篇 |
金属工艺 | 3篇 |
机械仪表 | 11篇 |
建筑科学 | 10篇 |
矿业工程 | 4篇 |
轻工业 | 388篇 |
水利工程 | 2篇 |
石油天然气 | 4篇 |
无线电 | 8篇 |
一般工业技术 | 48篇 |
冶金工业 | 1篇 |
原子能技术 | 1篇 |
自动化技术 | 6篇 |
出版年
2024年 | 7篇 |
2023年 | 27篇 |
2022年 | 53篇 |
2021年 | 77篇 |
2020年 | 43篇 |
2019年 | 58篇 |
2018年 | 30篇 |
2017年 | 43篇 |
2016年 | 23篇 |
2015年 | 19篇 |
2014年 | 37篇 |
2013年 | 34篇 |
2012年 | 37篇 |
2011年 | 27篇 |
2010年 | 23篇 |
2009年 | 15篇 |
2008年 | 15篇 |
2007年 | 22篇 |
2006年 | 26篇 |
2005年 | 43篇 |
2004年 | 29篇 |
2003年 | 23篇 |
2002年 | 17篇 |
2001年 | 15篇 |
2000年 | 10篇 |
1999年 | 7篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有782条查询结果,搜索用时 31 毫秒
41.
放线菌YIM31249发酵液萃取物的抗菌活性初步研究 总被引:6,自引:0,他引:6
从云南洱源采集的土壤样品中分离到一株放线菌YIM31249,进行摇瓶发酵,然后用乙酸乙酯萃取发酵液,对萃取物进行体外抗菌实验。试验表明:对大肠杆菌和金黄色葡萄球菌的最低抑菌浓度(HIC)为0.24mg/mL,最低杀菌浓度(MBC)为1.88mg/mL;对灰霉和黑曲霉的MIC和MBC均为0.022mg/mL。因此,放线菌YIM31249菌发酵液中具有天然抗菌活性物质,且抗菌作用明显,有较广的抗菌谱。 相似文献
42.
液膜分离技术在生化产品提取中的应用进展 总被引:6,自引:1,他引:6
介绍了液膜的基本概念、分类和分离机理。与传统的生化产品分离提纯技术相比,液膜分离技术具有简便、高效且成本低的特点。综述了液膜分离技术在抗生素和氨基酸提取中的应用进展,如青霉素、半合成青霉素、头孢菌素、麦白霉素、苯丙氨酸、亮氨酸和谷氨酸的提取,并指出其发展前景。 相似文献
43.
44.
45.
采用以新型高分子材料为生物载体的生物流化床工艺处理高浓度的抗生素废水。试验结果表明,该载体挂膜容易,启动快,一个月后载体附着的生物量可达4136mg/L,在载体表观体积为反应器总体积的50%、进水COD容积负荷低于2.5kg/(m3·d)的情况下,COD去除率可达85%以上。该生物流化床对BOD5的去除率平均高达89.21%,与COD的去除率具有同步性。并研究了反应器中悬浮污泥浓度SS和总生物量MLSS在整个实验期间的动态变化,表明稳定运行时SS和总MLSS基本上稳定不变,当系统受到高负荷冲击时,SS降低,总MLSS升高,而且生物活性也大幅度提高,生物膜处在适应期,反应器抗冲击负荷能力增强。 相似文献
46.
为了解抗生素对石油降解菌的生态效应及微生物对典型抗生素毒害作用的应激响应机制,通过开展不同浓度典型抗生素对高效石油降解菌铜绿假单胞菌(ZS1)的毒性试验,研究了菌体细胞在3种不同种类抗生素(土霉素、红霉素、磺胺嘧啶)作用下的生长及毒理指标。结果表明,3种抗生素对ZS1有不同的抑菌效果,其中土霉素对ZS1活性的抑制程度最强,抑制率随着土霉素浓度的增大而明显上升,有显著的浓度-效应关系。研究了ZS1抗氧化酶(过氧化氢酶、过氧化物酶、超氧化物歧化酶)对抗生素的响应机制,结果表明ZS1受到污染时会通过产生抗氧化酶抵抗外界污染并维持细胞功能。 相似文献
47.
The principle aim of the present study is to synthesis a novel mesoporous silica-based dual drug delivery system (DDDS) with unique features for the delivery of amoxicillin (antibiotic) and thiamine hydrochloride (vitamin). The DDDS was characterized by Fourier transform infrared, X ray diffraction, differential scanning calorimetry, scanning electron microscopy and atomic force micrographs analyses. The stimuli response behaviour of the drug carrier was studied by conducting swelling experiments as a function of pH and time. Drug release studies were carried out by mimicking gastric and intestinal conditions and found that the release of both drugs attained its maximum in the intestinal condition. The in vitro release data were analysed using Peppa’s potential equation in order to predict the release mechanism. The release of antibiotic follows non-Fickian mechanism whereas that of vitamin was diffusion controlled. An in vitro cytotoxicity analysis was carried out on L929 cells and the results showed that the synthesized DDDS is safe. DPPH assay and antibacterial activity were also analysed. From the investigation, it is evident that the prepared DDDS has potential application as dual drug carrier. 相似文献
48.
This study aimed to describe and compare the role of veterinarians and feed-store vendors in the use of antibiotics on small dairy farms in Cajamarca, Peru, a major dairy-producing center characterized by small, rural farms with poor, mostly uneducated farmers. We used a purposive sampling strategy to recruit 12 veterinarians into 2 focus group discussions and supplemented these data with 8 semi-structured interviews with feed-store vendors. Participants reported that inappropriate antibiotic usage was widespread among their clients, which may prevent the efficient use of drugs on farms where animal disease can be devastating to the livelihood of the farmer. Participants also identified many barriers to appropriate prescribing and use, including availability of drugs, competition from other prescribers, economic constraints and habits of farmers, and limited farmer knowledge of drugs and disease. Veterinarians expressed mistrust toward nonprofessional prescribers, whereas feed-store vendors felt that veterinarians were important partners in promoting the health of their clients’ animals. 相似文献
49.
抗生素废水处理的中试研究 总被引:4,自引:0,他引:4
采用中试规模的厌氧复合床 (2 2m3 )和周期循环活性污泥系统 (12m3 )处理抗生素废水 .当厌氧复合床的容积负荷为 6 0kgCOD/(m3 ·d)时 ,SS ,COD ,BOD5的去除率分别为 74 9% ,91 1% ,95 5 % ;当周期循环活性污泥系统的污泥浓度为 4 0 0 0mgMLSS/L ,污泥负荷为 0 4kgCOD/(kgMLSS·d)时 ,SS ,COD ,BOD5的去除率分别为 90 3% ,87 6 % ,95 4 % ,出水水质达到了国家生物制药工业废水排放标准 (GB8978- 1996 ) ,为工业规模的应用提供了技术参数和科学的实施方案 相似文献
50.
Rogers CA Fitzgerald AC Carr MA Covey BR Thomas JD Looper ML 《Journal of dairy science》2004,87(5):1558-1564
A 3-phase study was conducted to assess on-farm management decisions to reduce antibiotic residue violations and improve carcass characteristics in market (cull) dairy cows. In Phase 1, questionnaires were mailed to dairy producers (n = 142) to determine current on-farm management strategies for reducing antibiotic residues in market dairy cattle. In Phase 2, Holstein market cows (n = 77) were assigned randomly to each of the 3 feeding treatments (0, 30, or 60 d). Average daily gain (ADG), body condition score (BCS), and carcass characteristics were assessed. Phase 3 determined the meat withdrawal time of Holstein cows (n = 62) administered procaine penicillin G. Eighty-six percent of dairy farms responding to the questionnaire had at least one cow condemned annually, and no producer had a designated feeding protocol for market cows prior to selling. In Phase 2, ADG was greater in cows fed for 30 d (1.4+/-0.6 kg/d) than in cows fed for 60 d (0.9+/-0.4 kg/d). Additional feeding did not influence the carcass characteristics studied with the exception of kidney, pelvic and heart fat, which was higher in cows fed for 60 d compared with those fed for 0 and 30 d. In Phase 3, 31% of cows treated with procaine penicillin G exceeded the 10-d label withdrawal recommendation by an average of 3.1+/-1.9 d. Feeding market cows may not influence carcass characteristics, but can increase ADG and may ensure that recommended meat withdrawal times for antibiotics are exceeded. 相似文献