全文获取类型
收费全文 | 86656篇 |
免费 | 19616篇 |
国内免费 | 29107篇 |
专业分类
林业 | 9543篇 |
农学 | 9504篇 |
基础科学 | 9585篇 |
35783篇 | |
综合类 | 36075篇 |
农作物 | 7142篇 |
水产渔业 | 6532篇 |
畜牧兽医 | 10655篇 |
园艺 | 3436篇 |
植物保护 | 7124篇 |
出版年
2024年 | 807篇 |
2023年 | 1287篇 |
2022年 | 2064篇 |
2021年 | 2173篇 |
2020年 | 3561篇 |
2019年 | 6900篇 |
2018年 | 6451篇 |
2017年 | 7447篇 |
2016年 | 8104篇 |
2015年 | 8402篇 |
2014年 | 7533篇 |
2013年 | 8054篇 |
2012年 | 8234篇 |
2011年 | 7156篇 |
2010年 | 6092篇 |
2009年 | 5470篇 |
2008年 | 4225篇 |
2007年 | 4334篇 |
2006年 | 3867篇 |
2005年 | 3445篇 |
2004年 | 2980篇 |
2003年 | 2652篇 |
2002年 | 2396篇 |
2001年 | 2051篇 |
2000年 | 1734篇 |
1999年 | 1720篇 |
1998年 | 1540篇 |
1997年 | 1504篇 |
1996年 | 1342篇 |
1995年 | 1366篇 |
1994年 | 1305篇 |
1993年 | 1056篇 |
1992年 | 1045篇 |
1991年 | 876篇 |
1990年 | 701篇 |
1989年 | 662篇 |
1988年 | 597篇 |
1987年 | 411篇 |
1986年 | 420篇 |
1985年 | 216篇 |
1984年 | 205篇 |
1983年 | 192篇 |
1982年 | 193篇 |
1981年 | 235篇 |
1980年 | 193篇 |
1979年 | 150篇 |
1978年 | 131篇 |
1975年 | 110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 218 毫秒
71.
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
![点击此处可从《Canadian journal of veterinary research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
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
72.
Inheritance of myotonic discharges in American quarter horses and the relationship to hyperkalemic periodic paralysis.
下载免费PDF全文
![点击此处可从《Canadian journal of veterinary research》网站下载免费的PDF全文](/ch/ext_images/free.gif)
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
73.
74.
用微量热法测定了剌槐种子的萌发热谱,发现其产热规律与其吸水规律和呼吸规律相关,并获得了衡量种子活力4个参数。 相似文献
75.
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
76.
为获得白皮大蒜组培繁殖体系,以其茎尖为材料,通过BA和NAA不同激素配比试验研究,结果表明:诱导愈伤组织的最适培养基为:MS BA0.2mg/L NAA0.5mg/L,诱导率达60%;诱导不定芽的最适培养基为:MS BA1.0mg/L NAA0.1mg/L,丛生芽繁殖系数高达80%。同时,为建立扩繁最佳体系,分别研究了激素、pH、谷氨酸钠三因素对不定芽增殖系数的调节效果,研究表明:添加0.5mg/L的GA3使增值系数提高到13.8;pH5.8最利于不定芽增值;添加10mg/L谷氨酸钠能在多次继代培养中保持较高的增值系数。 相似文献
77.
78.
79.
不同放牧强度对滩羊生产性能影响的研究 总被引:4,自引:2,他引:2
为寻找适宜宁夏盐池县草地的放牧强度,于2003年5-11月在该县四墩子试点设5个处理(0.45、0.60、1.75、1.05和1.50只/hm2)进行轮牧,轮牧周期为42 d,共放牧154 d。结果表明:1)滩羊采食量随放牧强度的加重而降低。同一放牧强度下,随放牧时间推移,采食量先逐渐增大而后下降。2)在试验期内,不同放牧强度下,滩羊体重随时间推移总体上都呈增加趋势。在10月2日之后体重开始出现分化。与放牧强度重的处理相比,放牧强度轻的处理日增重峰值较高,持续时间较长。3)滩羊个体增重与放牧强度之间存在着强的负相关;单位草地面积(1 hm2)增重与放牧强度之间呈强的正相关,初步可以确定在该类草地上放牧强度应在0.75只/hm2左右。4)随着放牧强度的加重,饲料报酬先增大后减小。在同一放牧强度下,饲料报酬随时间的推移先升高后降低。5)当放牧强度超过0.75只/hm2以后,滩羊出现了空怀、产羔率降低和推迟怀孕的现象。6)综合考虑各研究指标,该类草地放牧强度以不应超过0.75只/hm2为宜。 相似文献
80.