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   105803篇
  免费   5474篇
  国内免费   52篇
林业   4319篇
农学   3053篇
基础科学   733篇
  11740篇
综合类   20730篇
农作物   4310篇
水产渔业   4643篇
畜牧兽医   54467篇
园艺   1203篇
植物保护   6131篇
  2018年   1213篇
  2017年   1340篇
  2016年   1290篇
  2015年   1103篇
  2014年   1271篇
  2013年   3946篇
  2012年   2582篇
  2011年   3206篇
  2010年   2090篇
  2009年   2058篇
  2008年   3227篇
  2007年   2947篇
  2006年   2819篇
  2005年   2649篇
  2004年   2749篇
  2003年   2684篇
  2002年   2630篇
  2001年   3275篇
  2000年   3297篇
  1999年   2447篇
  1998年   1072篇
  1997年   1084篇
  1995年   1253篇
  1994年   1165篇
  1993年   1122篇
  1992年   2367篇
  1991年   2536篇
  1990年   2443篇
  1989年   2498篇
  1988年   2278篇
  1987年   2353篇
  1986年   2487篇
  1985年   2395篇
  1984年   1918篇
  1983年   1774篇
  1982年   1165篇
  1981年   1123篇
  1980年   1025篇
  1979年   1762篇
  1978年   1424篇
  1977年   1147篇
  1976年   1131篇
  1975年   1166篇
  1974年   1524篇
  1973年   1610篇
  1972年   1584篇
  1971年   1515篇
  1970年   1408篇
  1969年   1262篇
  1967年   1094篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
51.
Nucleotide sequences of ribosomal DNA (rDNA) of Babesia (B.) gibsoni occurring in Miyazaki, western Japan, were examined using blood samples obtained from seven dogs suffering from natural canine babesiosis. DNA isolated from these blood samples was subjected to the polymerase chain reaction (PCR). The nucleotide sequences of the PCR products were determined and compared with other rDNA sequences of B. gibsoni isolated from Asia, Europe and U.S.A. Although homology values between our isolates and those isolated from Europe and U.S.A. were both 84.0%, respectively, our isolates were identical to the Asian types. In conclusion, B. gibsoni occurring in Miyazaki was revealed to have the genotype Asia 1 or Asia 2 from a comparison of the partial rDNA sequences.  相似文献   
52.
The dietary lysine requirement of juvenile red drum Sciaenops ocellatus was reevaluated in two separate experiments. In the first experiment, lyophilized red drum muscle was combined with an L-form crystalline amino acid premix to yield diets containing approximately 35% protein on a dry-matter basis. Gradations (0.25%) of L-lysine HCl were added to the basal diet containing approximately 1.0% lysine. Each diet was fed to triplicate groups of juvenile red drum initially weighing 6–7 g for 8 weeks. Based on growth and feed efficiency data, the lysine requirement (±SE) was determined to be 1.55% (±0.079%) of dry diet or 4.430% of dietary protein. In a second experiment, the lysine requirement of red drum was investigated with diets containing 35% intact protein from zein and red drum muscle. Each of the zein-based diets containing incremental levels of lysine was fed to triplicate groups of juvenile red drum initially weighing 1–2 g for 8 weeks. A crystalline amino acid test diet serving as a control in this experiment significantly outperformed the zein-based diets, and palatability of those diets was questionable due to an obvious change in feeding behavior of the fish. Due to the inferior performance of the fish fed the zein-based diets, the authors were not successful in determining a requirement with these diets. Thus, a lysine requirement of 1.55% of dry diet (4.43% of dietary protein) as determined in the first experiment is recommended for juvenile red drum.  相似文献   
53.
54.
Meat regulations also involve game inspection. This publication deals with the regulations concerning furred game intended for slaughter and furred game hunted for food.  相似文献   
55.
A complete radiographic examination of the equine foot consists of properly exposed, processed, and positioned radiographs. For radiographic interpretation, in addition to knowing radiographic signs of disease, a knowledge of normal radiographic anatomy and possible insignificant anatomic variations is necessary.  相似文献   
56.
Efficacy of ivermectin treatment (0.2 mg/kg) against 28-day experimental infections of Parascaris equorum was determined in 18 pony foals6–17.5 weeks old. There were 6 foals in each group: nontreated control, ivermectin injectable or oral paste. In comparison with larvae found in the nontreated controls, ivermectin injectable or paste was 96.0% and 99.9% efficacious. There was a distinct difference in drug effect against the larger (ca 26mm.) vs the smaller (13–19mm) larvae by the 2 formulations of ivermectin. There were no adverse signs related to treatment of the young foals.  相似文献   
57.
Although there are notable infectious conditions that are capable of producing clinical disease in the NWC, overall, these species are quite healthy. Of the bacterial diseases, enterotoxemia caused by Clostridium perfringens types C and D would be deemed the most significant in North America, while type A also would be regarded as important in South America. Other important bacterial infections of potential concern are tuberculosis, Johne's disease, anthrax, malignant edema, actinomycosis, tetanus, and the South American condition referred to as alpaca fever, which, to date, has not been observed in North America. Fungal infections include classical ringworm, principally caused by Trichophyton spp., and the cases of coccidioidomycosis that are associated with the arid desert lands of the southwestern United States. Most notable of naturally occurring viral infections in the NWC would be rabies, ecthyma, and a recently described blindness neuropathy that has been associated with the equine herpesvirus I. NWC can be infected experimentally with agents causing hoof-and-mouth disease and vesicular stomatitis, but naturally occurring cases do not seem to occur. Serological evidence of exposure to many viral agents, including blue tongue, parainfluenza 3, bovine respiratory syncytial virus, bovine herpesvirus I, bovine viral diarrhea, influenza A, and rotavirus, has been demonstrated; however, no clinical disease associated with these agents, as yet, is apparent.  相似文献   
58.
Infectious diseases remain one of the most important limitations to the successful propagation of aquatic animals. Most of the losses caused by pathogens in aquaculture could be prevented by health inspection, adequate environment and sound management practices. Effective control measures, mainly based upon 1) avoidance of pathogens 2) modification of the environment 3) improvement of host resistance 4) vaccination and 5) chemoprophylaxis are described.  相似文献   
59.
A survey of the potential use of synthetic oligopeptides in the field of virology is given. The potential value of synthetic peptides as vaccines and diagnostic antigens is discussed. The advantages compared to conventional vaccines as well as the limitations, e.g. the poor efficiency of immune response, are described.  相似文献   
60.
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