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   327642篇
  免费   38178篇
  国内免费   205篇
  2018年   2962篇
  2016年   4000篇
  2015年   5518篇
  2014年   6454篇
  2013年   9217篇
  2012年   10270篇
  2011年   10363篇
  2010年   7035篇
  2009年   6285篇
  2008年   9020篇
  2007年   9399篇
  2006年   8767篇
  2005年   8418篇
  2004年   8516篇
  2003年   8196篇
  2002年   8131篇
  2001年   14430篇
  2000年   14443篇
  1999年   11603篇
  1998年   4104篇
  1997年   4194篇
  1996年   3995篇
  1995年   3870篇
  1994年   3860篇
  1993年   3758篇
  1992年   9885篇
  1991年   9456篇
  1990年   9304篇
  1989年   9014篇
  1988年   8415篇
  1987年   8044篇
  1986年   7276篇
  1985年   7400篇
  1984年   6119篇
  1983年   5362篇
  1982年   4227篇
  1981年   3729篇
  1980年   3566篇
  1979年   6148篇
  1978年   4591篇
  1977年   4316篇
  1976年   4003篇
  1975年   4336篇
  1974年   4686篇
  1973年   4761篇
  1972年   4395篇
  1971年   4106篇
  1970年   3465篇
  1969年   3369篇
  1968年   2984篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
142.
143.
144.
145.
146.
147.
An investigational drug (2-picoline, 6-amino-4-nitro-, 1-oxide) was evaluated to characterize the anti-coccidial spectrum of the compound. Two concentrations of the drug (125 and 250 ppm) were evaluated for bioactivity; weight gain, survival, dropping, and lesion scores were the response variables utilized to ascertain activity. The activities of the picoline derivative were compared with monensin, maduramicin, and a narasin/nicarbazin (1:1) combination. The investigational drug had significant activity against Eimeria tenella and Eimeria necatrix, and the 250-ppm level was significantly more active than 125 ppm. At 250 ppm, the E. tenella activity of the picoline derivative was comparable to both monensin (120 ppm) and the 50-ppm narasin/nicarbazin combination, significantly less effective than maduramicin (6 ppm), and significantly more efficacious than 30 ppm narasin/nicarbazin. At the same level (250 ppm), the picoline derivative had significantly less E. necatrix activity than monensin (120 ppm), maduramicin (6 ppm), and narasin/nicarbazin (50 ppm), and significantly greater activity than 30 ppm narasin/nicarbazin. At best, only extremely weak Eimeria acervulina, Eimeria brunetti, and Eimeria maxima activities were noted with the investigational drug; higher concentrations of the picoline derivative may achieve greater anti-coccidial activity against these species. The efficacy of narasin/nicarbazin compared favorably with monensin and maduramicin; the 50-ppm level of the combination appeared significantly more efficacious than 30-ppm.  相似文献   
148.
The differences between the composition of volatile substances in two specimens of dry smoked sausages produced using a standard and experimental (a mixture of propionic acid bacteria and bifidobacteria) cultures were studied by capillary gas chromatography. It was found that the experimental starter culture intensified the flavor-formation processes as compared with the standard culture. The experimental specimen had richer qualitative and quantitative compositions and displayed more intensive aroma and flavor. The contents of lactones and volatile terpenoids in the experimental specimen were much higher than in the control. The organoleptic characteristics of experimental dry smoked sausage specimen were considerably better.  相似文献   
149.
Columba livia is an important reservoir and carrier of Cryptococcus neoformans, Cryptococcus uniguttulatus, Cryptococcus laurentii and Cryptococcus albidus. Upper digestive tract of this species is also known as a habitat for Cryptococcus neoformans. Given the increasing clinical interest of this microorganism, 331 swabs from crop and 174 dropping samples from pigeon lofts in Grand Canary Island have been studied. The obtained results show an extensive presence samples 81 positive (24.47%) of Cryptococcus spp. in analysed crops: 32 (9.66%) for C. neoformans, 24 (7.2%) for C. uniguttulatus, 23 (6.9%) for C. albidus and 2 (0.6%) for C. laurentii. In the same way, Cryptococcus spp was also isolated in 82 (47.13%), dropping samples: C. neoformans in 59 (33.9%), C. uniguttulatus, in 9 (5.17%), C. laurentii in 8 (4.59%) and C. albidus in 6 (3.44%) of the investigated samples, respectively. The cryptococcosis produced by species of cryptococci other than C. neoformans has become more important during the last decade, supporting the study on the role of pigeon in the epidemiology of this disease.  相似文献   
150.
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