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   102767篇
  免费   5188篇
  国内免费   42篇
林业   6443篇
农学   3917篇
基础科学   651篇
  12490篇
综合类   16873篇
农作物   5672篇
水产渔业   6016篇
畜牧兽医   46503篇
园艺   2080篇
植物保护   7352篇
  2019年   807篇
  2018年   3788篇
  2017年   3929篇
  2016年   2410篇
  2015年   1206篇
  2014年   1375篇
  2013年   3458篇
  2012年   3305篇
  2011年   5047篇
  2010年   3960篇
  2009年   3113篇
  2008年   4185篇
  2007年   4321篇
  2006年   2714篇
  2005年   2621篇
  2004年   2481篇
  2003年   2560篇
  2002年   2331篇
  2001年   2908篇
  2000年   2822篇
  1999年   2268篇
  1998年   975篇
  1997年   893篇
  1996年   790篇
  1995年   958篇
  1994年   863篇
  1993年   865篇
  1992年   1816篇
  1991年   1812篇
  1990年   1751篇
  1989年   1819篇
  1988年   1575篇
  1987年   1680篇
  1986年   1739篇
  1985年   1665篇
  1984年   1312篇
  1983年   1167篇
  1982年   842篇
  1981年   723篇
  1979年   1107篇
  1978年   900篇
  1977年   785篇
  1976年   734篇
  1975年   810篇
  1974年   999篇
  1973年   1041篇
  1972年   995篇
  1971年   946篇
  1970年   887篇
  1969年   812篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
991.
992.
993.
994.
To describe the clinical features and treatment of a cat that was initially presented with fibrotic myopathy affecting the left tensor fascia lata. Approximately 5 months later, the cat was presented again with multiple idiopathic fibrotic myopathies, affecting the ipsilateral rectus femoris and the contralateral semitendinosus muscles. These were each separate lesions and occurred without known history of trauma. Surgical resection of the fibrotic portion of the affected muscles resulted in immediate, but not long-term, resolution of clinical signs.  相似文献   
995.
996.
997.
998.
Genetic parameters of traits related to hepatic lipid metabolism, carcass composition, and product quality of overfed mule ducks were estimated on both parental lines of this hybrid: the common duck line for the maternal side and the Muscovy line for the paternal side. The originality of the statistical model was to include simultaneously the additive genetic effect of the common ducks and that of the Muscovy ducks, revealing a greater genetic determinism in common than in Muscovy. Plasma metabolic indicators (glucose, triglyceride, and cholesterol contents) were heritable, in particular at the end of the overfeeding period, and heritabilities increased with the overfeeding stage. Carcass composition traits were highly heritable in the common line, with values ranging from 0.15 for liver weight, 0.21 for carcass weight, and 0.25 for abdominal fat weight to 0.32 for breast muscle weight. Heritabilities of technological outputs were greater for the fatty liver (0.19 and 0.08, respectively, on common and Muscovy sides for liver melting rate) than for the pectoralis major muscle (between 0.02 and 0.05 on both parental sides for cooking losses). Fortunately, the processing industry is mainly facing problems in liver quality, such as too high of a melting rate, than in meat quality. The meat quality appraisal criteria (such as texture and cooking losses), usually dependent on pH and the rate of decline of pH, were also very lowly heritable. This study demonstrated that genetic determinism of meat quality and ability of overfeeding is not similar in the common population and in the Muscovy population; traits related to fattening, muscle development, and BW have heritability values from 2 to 4 times greater on the common line than on the Muscovy line, which is relevant for considering different selection strategies.  相似文献   
999.
Cefquinome concentrations, following intravenous and aerosol administration to horses, in pulmonary epithelial lining fluid (PELF) were examined and compared to plasma concentrations. Single dose of cefquinome sulphate (1 mg/kg) was administered intravenously to six horses followed by a single aerosol administration (225 mg) with a wash-out period of 14 days between treatments. After each drug administration, cefquinome concentrations in plasma and PELF, obtained by intrabronchial cotton swabs, were determined. After intravenous administration, cefquinome concentrations in plasma declined fast and were not detectable after 12 h. After aerosol administration, plasma concentrations were low or below limit of quantification (LOQ) during the entire sampling period. The degree of penetration of cefquinome into PELF after intravenous administration as described by the AUC(PELF) /AUC(plasma) ratio was 0.33. Following aerosol administration, cefquinome concentrations in PELF were high, but only detectable for 4 h. Based on AUC values, total cefquinome concentrations in PELF were one-third of total plasma concentrations after intravenous administration together with shorter time above Minimum Inhibitory Concentrations (T > MIC) in PELF, thus twice daily dosing may be required when treating lower airway infections in horses. Lower doses of cefquinome can be administered as aerosols providing high local drug concentrations in lung, but additional optimization of formulation is needed to improve distribution and persistence in lung.  相似文献   
1000.
Red-leg syndrome (RLS) is one of the main infectious diseases that cause economic losses in Lithobates catesbeianus hatcheries, Citrobacter freundii being an etiological agent. Treatment or prevention with therapeutics or chemicals results in modifications of the indigenous microbiota, development of antibiotic resistance, presence of their residues in food and enhancement of production costs. Thus, probiotics could be used as an alternative therapy. Lactic acid bacteria are part of the indigenous microbiota of healthy frogs and can prevent pathogen colonization by different mechanisms, including the production of antagonistic substances. In this work, the evaluation and characterization of the inhibition of C. freundii CFb by Lactococcus lactis subsp. lactis CRL 1584, a potentially probiotic candidate, were carried out. This strain produced lactic acid, H(2)O(2) and bacteriocin in static and shaken conditions and inhibited pathogen growth in associative cultures, with an earlier inhibition under agitated conditions. The elimination of each of the antimicrobial metabolites partially abolished the inhibition of the pathogen, suggesting that the inhibitory effect could be attributed to a combined action of the three antagonistic molecules. Electron microphotographs revealed the damage caused by L. lactis CRL 1584 supernatants to C. freundii cells. The addition of pure lactic acid, H(2)O(2) and bacteriocin to the culture media showed that each metabolite caused different morphological modifications in C. freundii, in agreement with the effect on viable cell counts. The results support the possibility that L. lactis CRL 1584 might be considered as a probiotic to be used in the prevention of RLS in raniculture.  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