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   510篇
  免费   22篇
林业   20篇
农学   15篇
基础科学   6篇
  108篇
综合类   46篇
农作物   28篇
水产渔业   27篇
畜牧兽医   239篇
园艺   5篇
植物保护   38篇
  2024年   4篇
  2023年   8篇
  2022年   11篇
  2021年   17篇
  2020年   11篇
  2019年   16篇
  2018年   22篇
  2017年   10篇
  2016年   16篇
  2015年   9篇
  2014年   16篇
  2013年   17篇
  2012年   19篇
  2011年   36篇
  2010年   31篇
  2009年   26篇
  2008年   37篇
  2007年   40篇
  2006年   28篇
  2005年   20篇
  2004年   22篇
  2003年   15篇
  2002年   17篇
  2001年   6篇
  2000年   7篇
  1999年   4篇
  1998年   2篇
  1997年   3篇
  1995年   5篇
  1994年   4篇
  1992年   4篇
  1991年   3篇
  1989年   2篇
  1988年   3篇
  1987年   1篇
  1986年   5篇
  1985年   7篇
  1984年   1篇
  1982年   3篇
  1981年   1篇
  1980年   2篇
  1977年   1篇
  1976年   3篇
  1975年   1篇
  1974年   5篇
  1965年   1篇
  1957年   2篇
  1955年   3篇
  1935年   1篇
  1934年   1篇
排序方式: 共有532条查询结果,搜索用时 15 毫秒
121.
In bright beers, the formation of haze is a serious quality problem, which places limitations on the storage life of the product. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) immunoblot analysis using an antiserum that was raised against a silica eluate (SE) protein fraction (obtained from silica gel, used for the colloidal stabilisation of beer), detected a range of protein bands in barley, malt, beer and haze. A polymorphism was observed in which some barley varieties contained a molecular weight (MW) 12,000 band (SE +ve) while in other varieties this band was absent (SE −ve). A survey of 219 Australian and international barley varieties, including a comprehensive selection of current and past malting varieties, identified 181 varieties as SE +ve, and 38 varieties as SE −ve. Previous pilot brewing trials demonstrated that SE −ve varieties are desirable as the beer brewed from the malt of these varieties formed less haze after accelerated ageing than beers brewed using SE +ve malt varieties. The genetic basis for the absence of the SE protein was conferred by a recessive allele at a single locus. Interval mapping analysis showed that the MW 12,000 band mapped to the short arm of chromosome 3H.  相似文献   
122.
The fate of freshly spiked and aged 14C-naphthalene associated residues as investigated in the presence and absence of ectomycorrhizal Scots pine seedlings and enchytraeid worms, in a factorial experimental design. Microcosms were used which enabled the 14C-labelled naphthalene associated residues to be quantified, including plant lipids which acted as an additional naphthalene sink within the microcosms. The presence of plant roots altered the availability of the 14C-naphthalene and associated residues to degrading microbes. Mineralisation and volatilisation of 14C naphthalene in freshly spiked soil were lower in the presence of Scots pine. Conversely, in soil aged for 180 d, Scots pine increased mineralisation, and bioavailability of naphthalene. Root-mediated processes, microbial activity and enchytraeids interact with desorption, bioavailability and mineralisation of naphthalene.  相似文献   
123.
Contagious equine metritis (CEM) is an important venereal disease of horses that is of concern to the thoroughbred industry. Taylorella equigenitalis is a causative agent of CEM but very little is known about it or its close relative Taylorella asinigenitalis. To reveal novel information about Taylorella biology, comparative genomic analyses were undertaken. Whole genome sequencing was performed for the T. equigenitalis type strain, NCTC11184. Draft genome sequences were produced for a second T. equigenitalis strain and for a strain of T. asinigenitalis. These genome sequences were analysed and compared to each other and the recently released genome sequence of T. equigenitalis MCE9. These analyses revealed that T. equigenitalis strains appear to be very similar to each other with relatively little strain-specific DNA content. A number of genes were identified that encode putative toxins and adhesins that are possibly involved in infection. Analysis of T. asinigenitalis revealed that it has a very similar gene repertoire to that of T. equigenitalis but shares surprisingly little DNA sequence identity with it. The generation of genome sequence information greatly increases knowledge of these poorly characterised bacteria and greatly facilitates study of them.  相似文献   
124.
A randomized, blinded, controlled field trial was conducted during summer 2006 in a northern California, USA, herd of beef cattle to evaluate the efficacy of a recombinant Moraxella bovoculi cytotoxin subunit vaccine to prevent naturally occurring infectious bovine keratoconjunctivitis (IBK; pinkeye). A convenience sample comprised of 127 steers were administered a subcutaneous dose of either adjuvant alone (ISCOM matrices; control group) or recombinant M. bovoculi cytotoxin carboxy terminus adjuvanted with ISCOM matrices (MbvA group) and were boostered 21 days later. The steers were examined once weekly for 15 weeks for evidence of IBK. No significant difference in the cumulative proportion of corneal ulcerations was detected between groups. Compared to the control calves, the MbvA vaccinates had significantly higher increases in serum neutralizing titers to M. bovoculi hemolysin between week 0 and week 6. The prevalence of M. bovis isolations was higher from ulcerated eyes of calves vaccinated with MbvA as compared to control calves. Vaccination of calves against the carboxy terminus of M. bovoculi RTX toxin resulted in significant increases in serum hemolysin neutralizing titers and may modulate organism type cultured from ulcerated eyes of calves in herds where both M. bovis and M. bovoculi exist. Use of M. bovoculi antigens alone in vaccines to prevent IBK may not be beneficial in herds where IBK is associated with both M. bovoculi and M. bovis.  相似文献   
125.
126.
At present, collective action regarding bio-security among UK cattle and sheep farmers is rare. Despite the occurrence of catastrophic livestock diseases such as bovine spongiform encephalopathy (BSE) and foot and mouth disease (FMD), within recent decades, there are few national or local farmer-led animal health schemes. To explore the reasons for this apparent lack of interest, we utilised a socio-psychological approach to disaggregate the cognitive, emotive and contextual factors driving bio-security behaviour among cattle and sheep farmers in the United Kingdom (UK). In total, we interviewed 121 farmers in South-West England and Wales. The main analytical tools included a content, cluster and logistic regression analysis.The results of the content analysis illustrated apparent ‘dissonance’ between bio-security attitudes and behaviour.1 Despite the heavy toll animal disease has taken on the agricultural economy, most study participants were dismissive of the many measures associated with bio-security. Justification for this lack of interest was largely framed in relation to the collective attribution or blame for the disease threats themselves. Indeed, epidemic diseases were largely related to external actors and agents. Reasons for outbreaks included inadequate border control, in tandem with ineffective policies and regulations. Conversely, endemic livestock disease was viewed as a problem for ‘bad’ farmers and not an issue for those individuals who managed their stock well. As such, there was little utility in forming groups to address what was largely perceived as an individual problem.Further, we found that attitudes toward bio-security did not appear to be influenced by any particular source of information per se. While strong negative attitudes were found toward specific sources of bio-security information, e.g. government leaflets, these appear to simply reflect widely held beliefs. In relation to actual bio-security behaviours, the logistic regression analysis revealed no significant difference between in-scheme and out of scheme farmers.We concluded that in order to support collective action with regard to bio-security, messages need to be reframed and delivered from a neutral source. Efforts to support group formation must also recognise and address the issues relating to perceptions of social connectedness among the communities involved.  相似文献   
127.
A 3-month-old Hereford heifer calf was presented for lethargy. Blood gas analysis and plasma biochemical testing revealed severe metabolic acidosis, azotemia, hyponatremia, hyperchloremia, and normal anion gap. Results of a urinalysis were consistent with acute tubular necrosis with inadequate acidification of urine based on the degree of acidemia. Salmonella enterica serovar agona was cultured from both urine and feces. The calf was treated with intravenous polyionic fluids, bicarbonate, and antimicrobials. Acidosis and azotemia resolved, and 4 months following initial presentation the heifer was clinically normal.  相似文献   
128.
Horses with large colon volvulus (LCV) often require intensive postoperative medical management. Although early referral and surgical intervention are critical for minimal postoperative complications and a successful outcome, this is often not possible for many reasons. Endotoxemia, extensive mucosal damage with subsequent severe hypoproteinemia, and focal ischemic necrosis are the major causes of postoperative morbidity and mortality.Although fluid therapy, flunixin meglumine, and antimicrobials are still the mainstay of perioperative management, synthetic colloids are being used to maintain plasma oncotic pressure, hyperimmune antiendotoxic plasma and polymixin B are being used for management of endotoxemia, and lidocaine and constant rate infusion of butorphanol can be used for postoperative analgesia. The use of heparin, dimethyl sulfoxide, and corticosteroids for management of LCV are still controversial. Future studies are required to investigate nutritional improvement and methods to manage cases after surgery to prevent recurrence.  相似文献   
129.
130.
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