全文获取类型
收费全文 | 603篇 |
免费 | 8篇 |
国内免费 | 1篇 |
专业分类
林业 | 22篇 |
农学 | 4篇 |
基础科学 | 2篇 |
91篇 | |
综合类 | 154篇 |
农作物 | 19篇 |
水产渔业 | 6篇 |
畜牧兽医 | 278篇 |
园艺 | 12篇 |
植物保护 | 24篇 |
出版年
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 5篇 |
2016年 | 3篇 |
2015年 | 3篇 |
2013年 | 2篇 |
2012年 | 54篇 |
2011年 | 71篇 |
2010年 | 12篇 |
2009年 | 7篇 |
2008年 | 33篇 |
2007年 | 39篇 |
2006年 | 40篇 |
2005年 | 48篇 |
2004年 | 32篇 |
2003年 | 25篇 |
2002年 | 40篇 |
2001年 | 15篇 |
2000年 | 30篇 |
1999年 | 16篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 10篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1976年 | 3篇 |
1971年 | 2篇 |
1968年 | 2篇 |
1967年 | 2篇 |
1959年 | 2篇 |
1958年 | 2篇 |
1956年 | 5篇 |
1954年 | 2篇 |
1953年 | 3篇 |
1948年 | 2篇 |
1947年 | 2篇 |
1923年 | 2篇 |
排序方式: 共有612条查询结果,搜索用时 0 毫秒
1.
2.
轮回选择是玉米育种程序中的组成部分,而且在其它作物中也日趋重要。Sprague等(1977)、Gardner(1978)、Hallauer等(1978)、Hallauer(1984)对不同的轮回选择方法及应用已有过讨论。用于群体内改良的轮回选择法包括混合选择、S_1、S_5、全同胞群体(FS)、修改FS(MFS)、 相似文献
3.
4.
经济价值高、美化环境佳的果树--人心果 总被引:2,自引:0,他引:2
人心果 ,属热带常绿乔木。其果实品质优良 ,经济价值高 ,而且常绿 ,周年挂果 ,是商品性栽培的良好果树 ,也是环境的美化果树。1 生物学特性 叶片浓绿 ,有光泽 ,单叶复生 ,长椭圆形 ,长9 5~ 11 5cm ,宽 2 9~ 3 2cm ,叶柄细长 ,约 2 8~3 1cm ,叶脉呈放射状平行脉 ,叶缘向叶面微卷 ,全缘。花腋生 ,每年 2月开始开花 ,5月果实成熟开始采收。由于人心果周年开花 ,故果实陆续成熟 ,周年都有果实采收 ,而以 6— 8月为最多。果实为浆果 ,略粗糙 ,呈卵形或球形 ,横径 4 5~ 5 5cm ,平均单果重 12 0~ 15 0g ,果实皮黄褐色或淡红褐色 ,果肉… 相似文献
5.
6.
三峡移民搬迁安置从1993年开始启动,现已完成全部移民搬迁任务。但目前只是做到了"搬得出"的目标,还没有达到"稳得住、逐步能致富"的终极目标。文中以巫山县为例对三峡库区后移民时代的移民安置方式进行了初步探讨,通过将政府主导的非自愿型移民安置模式与职业教育移民安置模式进行比较分析,提出了以职业教育移民为主要安置方式的战略选择。 相似文献
7.
MOLECULARANALYSISOFBENZIMIDAZOLEANDPHENYLCARBAMATERESISTANCEINRHYNCHOSPORIUMSECALISANDTHEAFFECTOFRES
Liu Bo Miao Rong 《植物病理学报》1996,(3)
田间抗性监测发现了大麦云纹斑病菌新型的抗性菌株,这类菌株对苯并咪唑类(多菌灵)、Phenylcarbamate(乙霉威)及三唑类(三唑醇)表现多重抗性,先前发现的多菌灵抗药性菌株均是在β-维管蛋白基因的198位点出现等位基因的突变,而新发现的菌株则仅在200位点(TTC)由苯并氨酸转变成赖氨酸(TAC)而导致对3种药剂的抗性。温室试验证明,这类菌株的致病性和野生敏感菌的致病性几乎一致,说明大麦云纹斑病菌对杀菌剂抗药性的发展与致病性之间没有相关性。 相似文献
8.
Davis MS Willard MD Nelson SL Mandsager RE McKiernan BS Mansell JK Lehenbauer TW 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2003,17(3):311-314
Human and equine athletes are reported to have a high prevalence of gastric disease, and anecdotal evidence suggests a similar phenomenon applies to racing sled dogs. To investigate the prevalence of gastric disease in racing sled dogs, we conducted 2 gastroscopy studies on dogs competing in the annual Iditarod Sled Dog Race. A pilot study of dogs that were either dropped from the 2000 Iditarod Sled Dog Race because of illness or that finished the race indicated that, approximately 5 days after competing, 10 of 28 dogs (35%) had endoscopic evidence of gastric ulceration, erosion, or hemorrhage. The next year, an endoscopic study of 73 dogs participating in the 2001 Iditarod race was performed in order to evaluate a larger population of dogs. Data from 70 of these dogs could be used; 34 (48.5%) had ulceration, erosion, gastric hemorrhage, or some combination of these findings. When this group of 70 dogs was compared retrospectively to a control group of 87 dogs presented to the Texas A&M University (TAMU) Veterinary Medical Teaching Hospital, the Iditarod sled dogs had a significantly higher prevalence (P = .049) of gastric lesions. These findings suggest that, similar to athletes of other species, elite canine athletes have an increased prevalence of gastric disease compared to the canine population at large. 相似文献
9.
Matsuda K Kim BS Whang IS Lim CW Baek BK 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2003,65(9):971-975
Strongyloides venezuelensis (SVZ) infection was chronologically monitored in 85 Sprague-Dawley rats (SDR), which were orally inoculated with approximately 1,000 infective larvae. In order to describe the characteristics of migrating larvae (MLS) in various visceral organs (the liver, lung, cardiac blood, and small intestine), 5 SDR were sacrificed at 20 min, 45 min, 1 hr, 2 hr, 3 hr, 4 hr, 8 hr, 12 hr, 16 hr, 48 hr, 72 hr, 96 hr, 120 hr, 144 hr, 168 hr and 192 hr post inoculation (PI). MLS were recovered from the liver and blood 20 and 45 min PI and measured 788 +/- 26 microm and 846 +/- 40 microm in length, respectively. MLS were first observed in the lung tissue 45 min PI and measured 925 +/- 38 microm on the average. In the trachea, MLS measuring 849 +/- 75 microm appeared 3 to 96 hrs PI. Adult worms (AWS) measuring 1,926 +/- 521 microm to 2,956 +/- 159 microm in length were observed in the small intestine from 120 hr PI. The worms appeared to mature more than 168 hr PI and attained the average maximum length of 2,420 +/- 532 microm. At 3 hr PI focal hyperemic and necrotic lesions were evidently observed in the liver and lung, together with eosinophilic infiltration in the stomach, liver, and lung. The parasites were histologically detectable in the lung tissues but were very difficult to find in the liver and the epithelial layer of small intestine. These data demonstrate that SVZ parasites take 20 min to reach the liver via the stomach and only three hours to reach the trachea through the same route. The development from eggs to adults takes 168 hr in the SDR model. 相似文献
10.
The acanthocephalan parasite Pomphorhynchus laevis (Müller, 1776) uses freshwater amphipods as its intermediate host. In order to complete the life cycle, the infected amphipod must be consumed by a fish, where the acanthocephalan will mature and reproduce. Parasite transmission, and therefore fitness, could be enhanced if infected amphipods fail to detect or avoid predatory fish. We compared the activity levels of infected and non-infected amphipods, Echinogammarus stammeri (Karaman, 1931), in both the presence and absence of odours from its natural, definitive host, the fish Leuciscus cephalus (L.). Throughout the experiment, infected amphipods were more active than were non-infected individuals. The non-infected amphipods reduced their activity after the addition of fish odours, but the infected amphipods failed to show a significant decrease. The failure of infected amphipods to reduce activity levels in the presence of fish odour may reflect a parasite strategy to increase its chances of transmission by making its amphipod host more vulnerable to predation by fish. 相似文献