全文获取类型
收费全文 | 20052篇 |
免费 | 1067篇 |
国内免费 | 1541篇 |
专业分类
林业 | 1929篇 |
农学 | 2310篇 |
基础科学 | 1200篇 |
3078篇 | |
综合类 | 5350篇 |
农作物 | 1185篇 |
水产渔业 | 871篇 |
畜牧兽医 | 4566篇 |
园艺 | 705篇 |
植物保护 | 1466篇 |
出版年
2024年 | 64篇 |
2023年 | 226篇 |
2022年 | 564篇 |
2021年 | 718篇 |
2020年 | 746篇 |
2019年 | 683篇 |
2018年 | 493篇 |
2017年 | 707篇 |
2016年 | 584篇 |
2015年 | 724篇 |
2014年 | 740篇 |
2013年 | 922篇 |
2012年 | 1110篇 |
2011年 | 1320篇 |
2010年 | 1077篇 |
2009年 | 1059篇 |
2008年 | 1037篇 |
2007年 | 952篇 |
2006年 | 882篇 |
2005年 | 823篇 |
2004年 | 492篇 |
2003年 | 432篇 |
2002年 | 438篇 |
2001年 | 400篇 |
2000年 | 456篇 |
1999年 | 565篇 |
1998年 | 439篇 |
1997年 | 379篇 |
1996年 | 355篇 |
1995年 | 296篇 |
1994年 | 351篇 |
1993年 | 300篇 |
1992年 | 284篇 |
1991年 | 254篇 |
1990年 | 224篇 |
1989年 | 211篇 |
1988年 | 127篇 |
1987年 | 122篇 |
1986年 | 81篇 |
1985年 | 79篇 |
1984年 | 79篇 |
1983年 | 65篇 |
1982年 | 67篇 |
1980年 | 41篇 |
1979年 | 46篇 |
1978年 | 45篇 |
1977年 | 44篇 |
1976年 | 45篇 |
1974年 | 42篇 |
1969年 | 43篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Botha CJ Schultz RA Van Der Lugt JJ Retief E Labuschagne L 《The Onderstepoort journal of veterinary research》1999,66(3):237-244
The plant Nierembergia hippomanica var. violacea has been incriminated in field outbreaks of neurotoxicity in calves in the Free State Province. Hepatotoxicity and electrocardiogram (ECG) deviations were induced in a sheep dosed with 5 g/kg dried plant material on four consecutive days. A calf dosed with 2.5 g/kg dried plant material, on two consecutive days, did not show overt clinical changes. Voluntary ingestion of approximately 30 g/kg fresh flowering plants by a second calf resulted in nervous signs characterized by chewing motions, protrusion of the tongue, dysphagia, hypermetria, ataxia, paresis and lateral recumbency. Salivation, dehydration and cardiac irregularities completed the clinical picture. Clinical chemistry changes revealed muscle damage and increased serum urea and creatinine concentrations indicative of kidney involvement. This is the first confirmed outbreak of Nierembergia hippomanica var. violacea intoxication of stock in South Africa. 相似文献
992.
本文研究了不同发芽促进剂及热震荡对芸薹属的不同种质的破眠效果,结果表明:(1)野生或自生种质的种子与栽培种质相比,均有较深的休眠性,其中尤以云南野生白菜(Brassiacampestris L.)及新疆毛芥(B.xinjiangensis Y.Z.Lan)的休眠性为强。(2)GA_2结合其他发芽促进剂与单独GA_2处理,对种子的萌发都有明显的促进作用,破眠程度(DBE)值在0.78—0.86之间,两者之间不存在显著差异,但是不同种质的DBE变化较大,以较深休眠的自生芥菜(B.juncea L.)效果最差。(3)热震荡对于解除芸薹属自生芥菜种子休眠的效果更差,劣于200ppm GA_3。 相似文献
993.
磷对板栗结实性能及产量的影响 总被引:26,自引:2,他引:24
试验结果表明,磷对板栗(Castanea mollissima Blume)雌花的形成数量有重要影响,结果母枝含磷量与母枝抽生结果枝数量和着生雌花数量呈显著正相关。板栗结果母枝含磷量比雄花母枝和营养枝分别高5.19%和5.27%。树体磷素含量水平与板栗雌、雄花枝比例和结果枝结栗苞数量也存在密切的相关性。在不同施磷水平下,结果枝粗度与果枝结栗苞数均具有显著的回归关系,但b值差异大。本研究结果在鄂东大别山区进行了大面积施磷肥示范,生产实践证明,施磷肥对板栗具有一致的增产效益。 相似文献
994.
995.
不同断奶日龄仔猪消化道酸度和胃蛋白酶活性的动态变化 总被引:17,自引:0,他引:17
将12窝同日龄新生仔猪随机分成4组,每组3窝,每窝为一个重复组,分别采取17、21、28和35日龄断奶,在断奶后12h、1周、2周和3周从每个重复组中随机抽取1头屠宰,共测定了54头仔猪胃、十二指肠、空肠和回肠食糜pH值及胃食糜中胃蛋白酶的活性。结果发现断奶后12h胃食糜pH值均高于同龄哺乳仔猪,并且达该组整个试验期间的最高,随后逐渐降低。4组仔猪在断奶后胃pH值回复到3.5所需的时间分别为3、2、1和1周,这表明断奶日龄越早,胃中pH值回复到3.5所需要的时间越长。 除十二指肠外,空肠和回肠食糜pH值基本上不受日龄和断奶的影响。哺乳仔猪从18-36日龄胃蛋白酶相对活性(U/ml胃液)和比活(U/mg蛋白质)增加10倍以上。不同断奶日龄仔猪各组在断奶后12h胃蛋白酶的相对活性和比活均聚然升高,达到该日龄铒猪阶段正常值的2倍左右,特别是小日龄断奶仔猪为明显,随后在3周内逐渐降低,至50日龄时稳定在一个较低水平。 相似文献
996.
997.
检测儿科常见疾病患者中的红细胞免疫粘附功能发现:(1)新生儿的红细胞免疫粘附功能尚未发育完善,低于正常儿童水平;(2)急性肾炎患儿的红细胞免疫粘附功能呈现继发性增强;(3)肾病综合征、风湿性疾病、大叶性肺炎、秋季腹泻及急性白血病等患儿的红细胞免疫粘附功能呈继发性降低;(4)红细胞免疫粘附功能的变化与疾病的发展及转归有关。提示在儿科疾病的诊断和治疗中观察患儿的红细胞免疫粘附功能有重要意义。 相似文献
998.
G. J. Bollen E. P. Van Der Hoeven J. G. Lamers M. P. M. Schoonen 《European journal of plant pathology / European Foundation for Plant Pathology》1983,89(1-2):55-66
The mycoflora of culm bases and roots of rye was assessed in field trials, where benomyl was applied at dose rates ranging from 0.24 to 4.80 kg ha?1. Samples of culm bases were taken three times during the growing season, those of roots only at the harvest date. On culms with various symptoms from untreated plots,Pseudocercosporella herpotrichoides, Alternaria spp. andGerlachia nivalis were prevalent and on those from benomyl-treated plotsAlternaria spp. andFusarium culmorum. In later stages of growth,G. nivalis sharply declined andAlternaria spp. andF. culmorum increased. At the end of the season,Periconia macrospinosa andTyphula incarnata appeared in treated plots. In samples of roots taken more than two months after the last spray, porosporous dematiaceous species (Alternaria, Ulocladium andDendryphion), Mortierella spp. and other resistant fungi were prevalent in plots treated with 1.20 kg ha?1 or more, but not in those that received 0.24 kg ha?1, which is recommended for disease control. Lower counts were recorded only for species that are highly sensitive in vitro, e.g.Microdochium bolleyi andTrichoderma spp. Some fusaria were either not affected or tended to be slightly stimulated by the treatment. An attempt was made to attribute the incidence of these moderately sensitive fungi to the effect of the fungicide on non-pathogens. 相似文献
999.
In utero transmission of bovine leukemia virus 总被引:8,自引:0,他引:8
M J Van der Maaten J M Miller M J Schmerr 《American journal of veterinary research》1981,42(6):1052-1054
In an initial study, 18 calves born to cows persistently infected with bovine leukemia virus (BLV) were tested for infective virus and antibodies at birth, and no infected or seropositive animals were found. Four of these calves were maintained in quarters where infected animals were housed, and 3 of the 4 subsequently became infected. These were probably contact infections acquired during, or at some time after, birth. The remaining 14 calves were kept in isolation pens in a building housing no infected cattle. None of this group was found to be BLV infected during 1 year of observation. In further studies, 15 pregnant cows inoculated with BLV became infected. One abortion, considered to be unrelated to the BLV inoculation, occurred 38 days later. The remaining 14 cows gave birth to 1 dead and 14 live calves. The dead calf and its live twin were seropositive for BLV at birth, indicating that they had been infected in utero. The remaining 13 calves were negative for BLV antibodies at birth and remained so during 1 year of observation. 相似文献
1000.
Interpreting problem diarrheas of dogs 总被引:2,自引:0,他引:2