全文获取类型
收费全文 | 88821篇 |
免费 | 19799篇 |
国内免费 | 29314篇 |
专业分类
林业 | 9627篇 |
农学 | 9533篇 |
基础科学 | 9504篇 |
35937篇 | |
综合类 | 37256篇 |
农作物 | 7350篇 |
水产渔业 | 6827篇 |
畜牧兽医 | 10918篇 |
园艺 | 3631篇 |
植物保护 | 7351篇 |
出版年
2024年 | 822篇 |
2023年 | 1381篇 |
2022年 | 2213篇 |
2021年 | 2231篇 |
2020年 | 3719篇 |
2019年 | 7008篇 |
2018年 | 6463篇 |
2017年 | 7592篇 |
2016年 | 8136篇 |
2015年 | 8538篇 |
2014年 | 7575篇 |
2013年 | 8162篇 |
2012年 | 8392篇 |
2011年 | 7433篇 |
2010年 | 6266篇 |
2009年 | 5662篇 |
2008年 | 4493篇 |
2007年 | 4575篇 |
2006年 | 4017篇 |
2005年 | 3541篇 |
2004年 | 3041篇 |
2003年 | 2583篇 |
2002年 | 2369篇 |
2001年 | 2021篇 |
2000年 | 1714篇 |
1999年 | 1692篇 |
1998年 | 1516篇 |
1997年 | 1498篇 |
1996年 | 1331篇 |
1995年 | 1385篇 |
1994年 | 1330篇 |
1993年 | 1062篇 |
1992年 | 1048篇 |
1991年 | 921篇 |
1990年 | 683篇 |
1989年 | 671篇 |
1988年 | 592篇 |
1987年 | 417篇 |
1986年 | 416篇 |
1985年 | 221篇 |
1984年 | 204篇 |
1983年 | 192篇 |
1982年 | 195篇 |
1981年 | 241篇 |
1980年 | 194篇 |
1979年 | 152篇 |
1978年 | 131篇 |
1975年 | 110篇 |
1965年 | 138篇 |
1964年 | 140篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
研究了箭舌豌豆不同器官对种子产量的贡献,结果表明:箭舌豌豆种子利用花后光合产物较多,不同器管对箭舌豌豆种子产量的贡献是复叶〉茎〉托叶,叶片对种子产量的贡献与其所在位置有关,花后叶因离荚果较近,其光合产物易于向荚果运输。 相似文献
62.
63.
将红檬实生苗培养于改良无土基质中,接种泡囊-丛枝菌根Glomuscitrocolum,以不接种菌根为对照,并分别施用含氮量相等的3种氮肥,即硝酸按(NO3-N)、尿素(NH2-N)和硫酸铵(NH4-N)。接种菌根16周后,施不同氮肥的红檬实生苗均有效地感染了菌根,并促进了植株的生长。试验证明,红实生苗施硝态氮(NO3-N)使植株的菌根依赖性有明显提高。 相似文献
64.
用两株单克隆抗体混合后包被ELLISA微孔板,加牛冠状病毒抗原,加经白陶土处理过的兔抗牛冠状病毒免血清,再加上辣根氧化物酶标记的羊抗兔IgG抗体,加底物质显色间接ELISA检测牛冠状病毒抗原获得成功。用此方法检测细胞培养的牛冠状病毒上清液,其敏感度高出血凝试验(HA)8倍,从武汉市附近3个奶牛场采集犊牛腹泻粪便105份,用单抗ELISA检测牛冠状病毒抗原,共检出阳性36份,并与血凝及血凝抑制试验, 相似文献
65.
Studies on efficacy and stability of a vaccine bait containing ERA strain of rabies virus propagated in a BHK-21 cell line. 下载免费PDF全文
K F Lawson H Chiu M Matson P Bachmann J B Campbell 《Canadian journal of veterinary research》1992,56(2):135-141
In a dose response study in foxes, the median protective dose of ERA BHK21 vaccine in a blister pack bait was 10(6.0) tissue culture infective doses (TCID)/mL, while artificially aged baits with titers of 10(6.3) TCID/mL induced seroconversion in 78% of foxes. There was no significant difference in the development of antibodies in foxes receiving 1, 2 or 3 mL volumes of vaccine in the bait. When baits were exposed to the elements and fed to foxes over a 21 day period, 85% of the animals seroconverted. Age, sex and the way in which the vaccine container was contacted did not appear to be factors in the responses of these animals. Juvenile foxes, approximately six months of age, were marked more readily with the tetracycline bait marker than older animals. Approximately 25% of foxes did not appear to respond well to vaccination and the titer of the vaccine was a critical factor in producing seroconversion in these animals. 相似文献
66.
Inheritance of myotonic discharges in American quarter horses and the relationship to hyperkalemic periodic paralysis. 下载免费PDF全文
J M Naylor J A Robinson E C Crichlow J E Steiss 《Canadian journal of veterinary research》1992,56(1):62-66
Electromyography (EMG) was used to detect myotonic discharges in Quarter Horse breeding stock and to follow the results of mating horses with hyperkalemic periodic paralysis (HPP). The studies were performed on two brood mare farms. A total of six breeding stock showed myotonic discharges and 15 were nonmyotonic. Myotonic discharges were seen in five of six horses belonging to the blood line previously implicated as being predisposed to HPP. Two of these horses had shown clinical signs of HPP. Only one of 15 breeding horses unrelated to the HPP predisposed blood line showed myotonic discharges. When both parents were non-myotonic on EMG than the F1 generation (n = 6) were also nonmyotonic. When a stallion with HPP and myotonic discharges was mated to eight nonmyotonic mares over a six year period half the animals of the F1 generation (n = 25) showed myotonic discharges. When both parents showed myotonic discharges four F1 offspring were myotonic and two were nonmyotonic on EMG testing. There was no evidence of sex linkage. The results are consistent with an autosomal dominant mode of inheritance. Hyperkalemic periodic paralysis and myotonic discharges on EMG may be different manifestations of the same underlying defect. 相似文献
67.
68.
J. Cabaret H. M. Baudet J. Devos J. Hubert J. Cortet C. Sauv 《Veterinary parasitology》1995,60(3-4):331-337
Multispecific resistance to benzimidazoles was studied in three selected farms. These farms had bred dairy goats for more than 15 years. The helminths were introduced with the goats at the establishment of the farms which afterwards remained isolated. Nematode resistance could then be related to their own management practices. Faecal egg count tests and egg hatch assays were performed to assess intensity of resistance. The generic (infective larvae in faecal cultures) and specific richness (adult worms) were assessed. The resistant species were Trichostrongylus colubriformis, Teladorsagia circumcincta, Haemonchus contortus and Oesophagostomum venulosum. Faecal egg count reduction tests and egg-hatch assays did not match exactly. Faecal larval counts after treatments gave a distorted picture of multispecific resistance: Haemonchus and Oesophagostomum were very largely over represented. The number of species found in the three farms was relatively low compared with other reports in goat farms of the area. This reduction of diversity might also be due in part to characteristics of breeding management and history (use of permanent pasture and introduction of goats at the establishment of farm). 相似文献
69.
70.
鱼类的消化道比较短,而且口腔摄取食物变化也不同于家畜,加上生活在水环境中,因此要求饲料必须易消化而且形状、大小和水中的沉浮性必须与鱼的大小、种类、自然采食习惯相适应。可以通过配方和加工工艺控制饲料的这些特点。这些指标中相比较水产饲料的密度被认为是评价产品质量 相似文献