全文获取类型
收费全文 | 175篇 |
免费 | 21篇 |
国内免费 | 2篇 |
专业分类
林业 | 5篇 |
农学 | 1篇 |
2篇 | |
综合类 | 22篇 |
农作物 | 1篇 |
水产渔业 | 2篇 |
畜牧兽医 | 151篇 |
园艺 | 1篇 |
植物保护 | 13篇 |
出版年
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 5篇 |
2016年 | 3篇 |
2015年 | 6篇 |
2014年 | 5篇 |
2013年 | 13篇 |
2012年 | 5篇 |
2011年 | 11篇 |
2010年 | 4篇 |
2009年 | 7篇 |
2008年 | 5篇 |
2007年 | 3篇 |
2006年 | 4篇 |
2005年 | 5篇 |
2004年 | 6篇 |
2003年 | 3篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1994年 | 2篇 |
1992年 | 9篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 12篇 |
1988年 | 2篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 7篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1970年 | 3篇 |
1969年 | 1篇 |
1968年 | 2篇 |
1967年 | 2篇 |
1936年 | 1篇 |
1912年 | 1篇 |
排序方式: 共有198条查询结果,搜索用时 218 毫秒
171.
172.
173.
DK Keefer SD deFrance ME Moseley JB Richardson DR Satterlee A Day-Lewis 《Science (New York, N.Y.)》1998,281(5384):1833-1835
The archaeological site of Quebrada Tacahuay, Peru, dates to 12,700 to 12,500 calibrated years before the present (10,770 to 10,530 carbon-14 years before the present). It contains some of the oldest evidence of maritime-based economic activity in the New World. Recovered materials include a hearth, lithic cutting tools and flakes, and abundant processed marine fauna, primarily seabirds and fish. Sediments below and above the occupation layer were probably generated by El Nino events, indicating that El Nino was active during the Pleistocene as well as during the early and middle Holocene. 相似文献
174.
175.
WL Vianna ME Pinese A de Campos Rosseto PP Bombonato PHM Rodrigues A de Sant''Anna Moretti 《Reproduction in domestic animals》2004,39(6):381-384
Swine uterine capacity affects litter size, and it could be used as a selection parameter of reproductive performance. Although there are some controversial results, evidences show that the catheter penetration length is positively correlated with litter size, and it could be used as a tool for predicting selection methods. The aim of this study was to determine whether there is any association between the prenatal survival rate and placental size at 70 days of gestation, the vaginal length [catheter penetration length during artificial insemination (AI)] and the uterine capacity in a homogeneous group of gilts. Sixty-six commercial-line gilts in pre-pubertal phase had their oestrus induced by hormonal treatment [600 UI of Equine Chorionic Gonadtrophin (eCG) i.m. and after a 72-h period 5 mg of luteinizing hormone (LH) i.m.], but only 40 gilts showed cyclicity after induction. The AI catheter penetration length was tested on these 40 gilts at the moment of AI using a calibrated AI catheter. Four gilts returned to oestrus and the other 36 were killed at around day 69 of pregnancy. The uterine length and weight showed a significant and positive correlation with the prenatal survival rate (p <0.05). The catheter penetration length was unable to predict the conceptus survival rate on 70 days of gestation; however, the uterine size influenced the survival rate positively. The mean placental area was positively correlated with the mean placental weight (p <0.0001), and both with the mean foetal weight (p <0.0001 and p <0.001, respectively). The analysis of the results obtained showed that neither did the catheter penetration length measurement during AI, nor the prenatal survival rate on day 70 of pregnancy predict the uterine capacity, but the uterine and placental size had a significant influence on the prenatal survival and foetus weight, respectively. 相似文献
176.
177.
G E Burrows 《Journal of the American Veterinary Medical Association》1980,176(11):1280-1281
178.
在分析时态数据库的研究与应用现状基础上,针对森林资源数据特点,在对象—关系Oracle数据库上,扩展基本数据类型和函数集,实现森林资源时空数据的有效储存,对森林资源数据的现状及变化等基本信息进行空间拓扑、时态拓扑和时空拓扑操作,提供完善的时序分析功能,高效地回答与时间相关的各类问题,准确地描述森林资源信息,完整地反映森林资源演变过程,为森林资源数据管理提供服务,对森林资源数据库的建设提供新的思路和方法。 相似文献
179.
180.
Percutaneous endoscopic tube gastrostomy was performed in 10 dogs, using mushroom-tip catheters (16 to 24 F) maintained in place for 5 to 32 days. Dogs were observed daily. Although placement of the catheter was simple and quick, 3 dogs destroyed their catheters. Patency of the catheter was maintained with or without regular flushings with saline solution. Pyrexia (greater than or equal to 39.4 C) developed in 3 dogs, but the rectal temperature returned to base line within 24 hours after catheter removal. After catheter removal, all wounds healed without complication. All dogs were euthanatized. Five were examined radiographically before euthanasia to determine the fate of the mushroom tip after transection of the catheter at skin level between days 5 and 21, and 5 dogs were evaluated at postmortem examination between days 10 and 32. In all dogs, the tip was not present in the gastrointestinal tract by 96 hours after catheter transection. During postmortem examination of the 5 dogs, minimal inflammatory lesions were seen in the gastric tissue. A gastrocutaneous fistula had formed in each dog, resulting in an adhesion between the stomach and peritoneum. 相似文献