全文获取类型
收费全文 | 113120篇 |
免费 | 20617篇 |
国内免费 | 31611篇 |
专业分类
林业 | 11047篇 |
农学 | 8825篇 |
基础科学 | 10193篇 |
37497篇 | |
综合类 | 51856篇 |
农作物 | 9196篇 |
水产渔业 | 7525篇 |
畜牧兽医 | 14966篇 |
园艺 | 6161篇 |
植物保护 | 8082篇 |
出版年
2024年 | 1193篇 |
2023年 | 1996篇 |
2022年 | 3554篇 |
2021年 | 3419篇 |
2020年 | 4751篇 |
2019年 | 7819篇 |
2018年 | 6964篇 |
2017年 | 8693篇 |
2016年 | 8622篇 |
2015年 | 9584篇 |
2014年 | 8782篇 |
2013年 | 9629篇 |
2012年 | 10661篇 |
2011年 | 9735篇 |
2010年 | 8508篇 |
2009年 | 7684篇 |
2008年 | 6580篇 |
2007年 | 6415篇 |
2006年 | 5551篇 |
2005年 | 4585篇 |
2004年 | 3937篇 |
2003年 | 3083篇 |
2002年 | 2828篇 |
2001年 | 2487篇 |
2000年 | 2107篇 |
1999年 | 1598篇 |
1998年 | 1276篇 |
1997年 | 1259篇 |
1996年 | 1113篇 |
1995年 | 1169篇 |
1994年 | 1156篇 |
1993年 | 914篇 |
1992年 | 935篇 |
1991年 | 787篇 |
1990年 | 606篇 |
1989年 | 594篇 |
1988年 | 535篇 |
1987年 | 397篇 |
1986年 | 405篇 |
1985年 | 212篇 |
1984年 | 196篇 |
1983年 | 190篇 |
1982年 | 190篇 |
1981年 | 242篇 |
1980年 | 192篇 |
1979年 | 150篇 |
1978年 | 130篇 |
1975年 | 109篇 |
1965年 | 137篇 |
1964年 | 140篇 |
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
71.
越桔对长白山区酸性土壤的适应性 总被引:15,自引:1,他引:14
在长白山区3种类型的酸性土壤上栽培越桔,研究结果表明,`北空'、`美登'、`斯卫克'在暗棕色森林土上生长结果较好,树体营养关系合理;在草甸沼泽土上3个种生长结果均较差,`北空'在水湿地潜育土上生长旺盛,但产量低,综合分析认为,矮丛越桔类型品种对我国长白山区酸性土壤条件的适应性较强,半高丛越桔则适应性差,针对长白山不同类型的土壤,以美登最为适宜暗棕色森林土栽培,斯卫克次之;水湿地潜育土可栽培美登品种 相似文献
72.
73.
74.
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
75.
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
76.
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
77.
78.
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
79.
80.
苦皮藤素微粉剂对玉米中玉米象种群的控制 总被引:2,自引:1,他引:1
苦皮藤素微粉剂1和微粉剂2以不同的浓度混入玉米中,当使用剂量为1000mg/kg时,对玉米象成虫的种群繁殖抑制率分别为96.66%和96.02%,能有效控制玉米象成虫的危害,但对幼虫和卵的控制效果不明显。 相似文献