全文获取类型
收费全文 | 14259篇 |
免费 | 771篇 |
国内免费 | 2210篇 |
专业分类
林业 | 1643篇 |
农学 | 1203篇 |
基础科学 | 1492篇 |
3078篇 | |
综合类 | 5755篇 |
农作物 | 957篇 |
水产渔业 | 595篇 |
畜牧兽医 | 1308篇 |
园艺 | 386篇 |
植物保护 | 823篇 |
出版年
2024年 | 144篇 |
2023年 | 350篇 |
2022年 | 571篇 |
2021年 | 644篇 |
2020年 | 673篇 |
2019年 | 762篇 |
2018年 | 490篇 |
2017年 | 724篇 |
2016年 | 824篇 |
2015年 | 723篇 |
2014年 | 861篇 |
2013年 | 864篇 |
2012年 | 1234篇 |
2011年 | 1178篇 |
2010年 | 908篇 |
2009年 | 846篇 |
2008年 | 760篇 |
2007年 | 815篇 |
2006年 | 650篇 |
2005年 | 603篇 |
2004年 | 437篇 |
2003年 | 337篇 |
2002年 | 294篇 |
2001年 | 262篇 |
2000年 | 215篇 |
1999年 | 190篇 |
1998年 | 164篇 |
1997年 | 135篇 |
1996年 | 109篇 |
1995年 | 96篇 |
1994年 | 75篇 |
1993年 | 58篇 |
1992年 | 54篇 |
1991年 | 40篇 |
1990年 | 36篇 |
1989年 | 40篇 |
1988年 | 22篇 |
1987年 | 14篇 |
1986年 | 8篇 |
1985年 | 11篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1978年 | 1篇 |
1962年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
M. Masko M. Domino K. Skierbiszewska Ł. Zdrojkowski T. Jasinski Z. Gajewski 《Equine Veterinary Education》2020,32(12):654-663
Complications in late gestation are challenging problems for the equine clinician and are causes of considerable distress to owners. Health problems in a pregnant mare in each stage of gestation can adversely affect the pregnancy. It is important to obtain a thorough history and perform a detailed and systematic examination of the pregnant mare so that the mare may be classified as normal or high-risk. However, even after a thorough examination, practitioners may face problems with the interpretation and assessment of risk. Normal mares should foal in the stable or pasture. Mares classified as having a high-risk pregnancy need to be monitored precisely for signs of oncoming foaling with attendance of trained personnel when labour begins. A valuable method for monitoring of the high-risk mare is assessing fetoplacental well-being. Fetoplacental well-being is most accurately assessed with ultrasonography as well as several available hormone profiles. We are proposing our scoring system of the mare's health, which may be useful in the assessment of risk during pregnancy and help clinicians to decide whether sending the mare to the clinic is reasonable or unnecessary. 相似文献
83.
84.
Suzanne M. Donahue VMD DACVECC Cynthia M. Otto DVM PhD DAVECC 《Journal of Veterinary Emergency and Critical Care》2005,15(1):9-16
Objective: To describe the technique of thromboelastography (TEG) and review the applications of this coagulation test in humans and small animals. Data sources: Data sources included scientific reviews and original research publications. Human data synthesis: TEG in humans has been used for documentation of hypercoagulable and hypocoagulable states and has been shown to be beneficial in patient management. Veterinary data synthesis: Clinical evaluation of TEG in veterinary medicine is limited; however, recent reports have documented evidence of hypercoagulability in dogs with parvovirus and protein‐losing nephropathy. Additionally, many of the research models may be relevant to veterinary patients. Conclusions: TEG provides information about coagulation that is not available through routine coagulation tests. The application of TEG monitoring to veterinary patients shows promise; however, prospective clinical studies are needed. 相似文献
85.
我国南方猪高热病的研究(Ⅰ)——大肠杆菌的分离、鉴定和致病性测定 总被引:40,自引:2,他引:40
从湖南3个高热病发病猪场11头病死猪的病料组织中均分离出了大肠杆菌,经血清学鉴定,鞭毛抗原(K88、K99、987P和F41)全为阴性反应。经过157种菌体抗原血清学检测,血清型为5、6、15、22、32和83型。药物敏感试验结果表明,分离的大肠杆菌对大多数常用药物耐药,对氟喹诺酮和头孢类药物敏感。将其中4头猪原代分离的大肠菌培养物以原倍(2×107个/mL)、104和108稀释的菌液分别感染18~22 g小白鼠,原倍菌液感染的小白鼠12/30在感染后24 h内出现死亡,而104和108稀释菌液感染的小白鼠均健活;将未经除菌的病死猪组织悬液、过滤除菌的组织悬液、大肠杆菌、过滤除菌的组织悬液及大肠杆菌分别感染30日龄左右的健康小猪,除未经除菌的组织悬液感染猪3/3发病,2/3死亡外,其余所有感染猪只出现体温升高,升幅达1~2℃,减食,精神萎靡,但没有死亡;将死亡猪再次分离到的大肠杆菌感染小白鼠和猪,小白鼠12/15出现死亡,感染猪只出现体温升高(超过1℃),没有出现死亡。结果证明:大肠杆菌在高热病的发病过程中只起协同诱发作用,引起猪发病死亡的真正原因可能是病毒感染。 相似文献
86.
87.
分别用超声波处理不同粉碎粒度的高温脱脂豆粕,然后采用醇法浸提工艺提取其中的大豆浓缩蛋白(SPC)。结果显示:40目、60目及80目豆粕提取的大豆浓缩蛋白中粗蛋白含量分别为51.85%、55.50%和54.32%(P〈0.05)。提取率分别为97.65%、97.51%和95.80%(P〈0.05);超声波处理之后提取的大豆浓缩蛋白中粗蛋白含量分别为55.44%、55.11%和58.77%(P〈0.05),提取率分别为97.50%、96.78%和95.65%(P〈0.05)。不同的粉碎粒度对大豆浓缩蛋白中粗蛋白的含量及提取率有显著影响,粒度越小,粗蛋白含量越高,提取率越低;在相同的粉碎粒度下,超声波处理能提高大豆浓缩蛋白中粗蛋白的含量,但是对其提取率无显著影响。 相似文献
88.
天然草地牧草营养品质的优劣不仅影响家畜的生长发育,同时也影响畜产品的品质,对草牧业的发展具有至关重要的意义。高光谱遥感技术的飞速发展使深入研究天然草地牧草品质的动态变化成为可能。本研究综述了目前可利用的高光谱遥感数据以及天然草地牧草营养品质遥感反演的主要成果、常用方法和最新研究动态,分析了我国在天然草地牧草营养品质监测与评价方面尚存在数据获取困难、相关研究缺乏、软硬件性能不足等问题;在多种观测平台及相关技术不断革新背景下,探索星载、机载和地面高光谱数据的有机结合,强化高光谱遥感仪器性能,提高关键营养成分的反演精度是未来研究的重点。 相似文献
89.
Stacy L Anderson Tanya Duke‐Novakovski Baljit Singh 《Veterinary anaesthesia and analgesia》2014,41(2):113-126
ObjectiveTo review the immune response to anesthesia including mechanical ventilation, inhaled anesthetic gases, and injectable anesthetics and sedatives.Study designReview.Methods and databasesMultiple literature searches were performed using PubMed and Google Scholar from spring 2012 through fall 2013. Relevant anesthetic and immune terms were used to search databases without year published or species constraints. The online database for Veterinary Anaesthesia and Analgesia and the Journal of Veterinary Emergency and Critical Care were searched by issue starting in 2000 for relevant articles.ConclusionRecent research data indicate that commonly used volatile anesthetic agents, such as isoflurane and sevoflurane, may have a protective effect on vital organs. With the lung as the target organ, protection using an appropriate anesthetic protocol may be possible during direct pulmonary insults, including mechanical ventilation, and during systemic disease processes, such as endotoxemia, generalized sepsis, and ischemia-reperfusion injury. 相似文献
90.
《The Journal of Applied Poultry Research》2014,23(3):393-402
The purpose of this study was to evaluate feeding 2 levels of spray-dried bovine plasma protein (SDP) on production performance of laying hens subjected to high ambient temperatures. Two groups of 96 Hy-Line W-98 hens (38 wk of age) were housed in each of 2 environmentally controlled chambers. At 40 wk of age, all hens were fed 3 diet treatments consisting of (1) a control diet (0% SDP); (2) the control diet supplemented with 0.75% SDP; and (3) the control diet supplemented with 1.50% SDP. Hens in each chamber (8 cages of 4 hens per cage) were ad libitum fed 1 of each diet for 5 wk. The heat stress (HS) chamber was maintained at 21°C (wk 1), 29°C (wk 2), and 35°C (wk 3 to 5). The thermoneutral chamber was maintained at 21°C during wk 1 to 5. A significant main effect of week was observed for hens maintained in the HS chamber for egg production, egg weight, egg mass, and feed consumption, which resulted in acute heat stress causing a reduction in these parameters. Hens fed the 1.50% SDP diet in the HS chamber produced greater (P < 0.05) egg mass on average than hens fed the control or 0.75% SDP diet (wk 1 to 5). During the second week of acute HS (wk 4), hens fed the control and 1.50% SDP diets had greater (P < 0.05) egg production than those fed the 0.75% SDP diet. During wk 5, hens in the HS chamber that were fed the 1.50% SDP diet produced more (P < 0.05) eggs than those fed the control diet. Therefore, based on the results of this study, acute HS negatively affected short-term production performance. In addition, feeding hens an SDP-supplemented diet may have a slight positive effect on production performance when maintained in acute HS conditions. 相似文献