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   9275篇
  免费   417篇
  国内免费   14篇
林业   588篇
农学   229篇
基础科学   84篇
  1585篇
综合类   1613篇
农作物   365篇
水产渔业   822篇
畜牧兽医   3373篇
园艺   278篇
植物保护   769篇
  2024年   19篇
  2023年   59篇
  2022年   90篇
  2021年   155篇
  2020年   211篇
  2019年   208篇
  2018年   206篇
  2017年   218篇
  2016年   210篇
  2015年   184篇
  2014年   252篇
  2013年   449篇
  2012年   542篇
  2011年   707篇
  2010年   368篇
  2009年   352篇
  2008年   635篇
  2007年   623篇
  2006年   592篇
  2005年   574篇
  2004年   608篇
  2003年   571篇
  2002年   504篇
  2001年   98篇
  2000年   90篇
  1999年   93篇
  1998年   81篇
  1997年   70篇
  1996年   67篇
  1995年   62篇
  1994年   61篇
  1993年   50篇
  1992年   57篇
  1991年   49篇
  1990年   58篇
  1989年   49篇
  1988年   43篇
  1987年   44篇
  1986年   33篇
  1985年   32篇
  1984年   34篇
  1983年   40篇
  1982年   26篇
  1981年   25篇
  1980年   30篇
  1979年   23篇
  1978年   20篇
  1976年   20篇
  1975年   22篇
  1974年   15篇
排序方式: 共有9706条查询结果,搜索用时 21 毫秒
51.
A group discussion on the theme of "leadership" has been a central event in the annual Cornell Leadership Program for Veterinary Students since 1990. However, these discussions were often unfocused and did not readily demonstrate the leadership skills of distinguished guests who were invited to participate. Since 1998, a new format for this session has been developed in which students and guests are assigned individual roles in a scenario that is unfolded by a moderator over two to three hours. This role-playing exercise ensures that every student is obliged to participate and has an opportunity to practice such leadership skills as critical thinking, verbal communication, and decision making under pressure and with inadequate information. The distinguished guests, in their assigned roles, are able to interact freely with the student fellows and thus demonstrate their expertise as experienced leaders. This challenging experience has become an enjoyable part of the 10-week Leadership Program and one that shows the importance of leadership skills for those who aspire to careers in the biomedical sciences.  相似文献   
52.
53.
54.
Vessel-whale collision events represented the ultimate cause of death for 21 (52.5%) of the 40 North Atlantic right whales (Eubalaena glacialis) necropsied between 1970 and December 2006. Injuries seen in vessel-struck whales fall into two distinct categories: 1) sharp trauma, often resulting from contact with the propeller, and 2) blunt trauma, presumably resulting from contact with a vessel's hull. This study analyzes four trauma cases that resulted from vessel-whale collisions, which together provide a framework for a more critical understanding of lethal blunt and sharp trauma resulting from vessel collisions with right whales. In case no. 1, contact with a propeller resulted in three deep lacerations. The animal survived acute trauma only to succumb nearly 14 years later when the lesions reopened and became infected. In case no. 2, anecdotal reports linked the laceration of large arteries of the peduncle and histologic evidence of perimortem trauma at a bone fracture site to vessel-whale collision trauma. Case no. 3 had a laceration of the oral rete and a fracture of the rostrum. Both of the areas displayed histologic evidence of perimortem blunt trauma. Finally, in case no. 4, an antemortem mandibular fracture, two additional skull fractures, and widespread hemorrhage were consistent with severe blunt trauma. Evidence from each case, including the timing of trauma relative to the time of death and identifying characteristics of both trauma types, are presented. Before this study, no detailed comparative analysis of trauma pathology that resulted from lethal interactions between vessels and right whales had been conducted. This study demonstrates the importance of detailed gross and histologic examination in determining the significance and timing of traumatic events. This work represents a new paradigm for the differential diagnosis of lethal sharp and blunt trauma in right whales hit by ships and will enhance the present understanding of the impact of anthropogenic mortality on this critically endangered species.  相似文献   
55.
Digital radiography is becoming more prevalent in veterinary medicine, and with its increased use has come the recognition of a number of artifacts. Artifacts in digital radiography can decrease image quality and mask or mimic pathologic changes. They can be categorized according to the step during which they are created and include preexposure, exposure, postexposure, reading, and workstation artifacts. The recognition and understanding of artifacts in digital radiography facilitates their reduction and decreases misinterpretation. The purpose of this review is to name, describe the appearance, identify the cause, and provide methods of resolution of artifacts in digital radiography.  相似文献   
56.
57.
58.
The dog is widely used as a translational experimental model studying the host response and new treatments for human endotoxemia. The present study evaluated the applicability of a novel patient-near neutrophil chemiluminescence assay for the measurement of endotoxin activity in human blood when applied to canine blood samples. The assay was observed to be analytically sensitive and specific to endotoxin when tested in vitro, spiked with purified Escherichia coli lipopolysaccharide and live E. coli. The diagnostic sensitivity was sustained during Gram-positive contamination. Finally, it also demonstrated diagnostic potential when able to discriminate dogs with spontaneously occurring endotoxemia from both healthy dogs and diseased dogs without endotoxemia. The rapid patient-near assessment of endotoxin activity in canine blood should facilitate future studies on endotoxemia in both spontaneous disease and in experimental settings.  相似文献   
59.
A 1-month-old male Thoroughbred foal was presented at necropsy. A focal purulent lesion was observed in the right ventricular free wall of the myocardium. To the authors' knowledge, this is the first report of Streptococcus zooepidemicus myocardial abscessation in an equine.  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