全文获取类型
收费全文 | 2125篇 |
免费 | 159篇 |
专业分类
林业 | 54篇 |
农学 | 43篇 |
基础科学 | 7篇 |
235篇 | |
综合类 | 398篇 |
农作物 | 62篇 |
水产渔业 | 104篇 |
畜牧兽医 | 1210篇 |
园艺 | 37篇 |
植物保护 | 134篇 |
出版年
2023年 | 15篇 |
2021年 | 26篇 |
2020年 | 32篇 |
2019年 | 38篇 |
2018年 | 37篇 |
2017年 | 48篇 |
2016年 | 44篇 |
2015年 | 35篇 |
2014年 | 48篇 |
2013年 | 89篇 |
2012年 | 71篇 |
2011年 | 97篇 |
2010年 | 52篇 |
2009年 | 44篇 |
2008年 | 76篇 |
2007年 | 86篇 |
2006年 | 70篇 |
2005年 | 70篇 |
2004年 | 76篇 |
2003年 | 79篇 |
2002年 | 87篇 |
2001年 | 59篇 |
2000年 | 77篇 |
1999年 | 52篇 |
1998年 | 17篇 |
1997年 | 13篇 |
1996年 | 17篇 |
1995年 | 22篇 |
1992年 | 40篇 |
1991年 | 48篇 |
1990年 | 41篇 |
1989年 | 27篇 |
1988年 | 26篇 |
1987年 | 33篇 |
1986年 | 34篇 |
1985年 | 34篇 |
1984年 | 20篇 |
1983年 | 29篇 |
1982年 | 12篇 |
1979年 | 32篇 |
1978年 | 16篇 |
1977年 | 15篇 |
1976年 | 13篇 |
1973年 | 17篇 |
1972年 | 20篇 |
1971年 | 24篇 |
1970年 | 29篇 |
1969年 | 12篇 |
1967年 | 17篇 |
1966年 | 18篇 |
排序方式: 共有2284条查询结果,搜索用时 8 毫秒
71.
extract Spergula arvensis (Spurrey, known locally as Yarr) is a fine- stemmed, viscid, erect or sprawling annual up to 30cm tall, with small white flowers and narrow, needle-shaped leaves in whorls at each stem node. It is a common weed of recently cultivated pastures. We have found no record of toxicity associated with ingestion of this plant, apart from a suggestion of illness when fed to caged birds (Roy et al., 1998). One of the authors (JDH) can recall a calcium-responsive recumbency in a small number of ewes grazing a poorly established swede crop in summer in which Yarr was the predominant green feed available. 相似文献
72.
73.
Effects of interferents on the kinetic Jaffé reaction and an enzymatic colorimetric test for serum creatinine concentration determination in cats, cows, dogs and horses. 下载免费PDF全文
R M Jacobs J H Lumsden J A Taylor E Grift 《Canadian journal of veterinary research》1991,55(2):150-154
The effects of acetoacetic acid, acetone, bilirubin, beta-carotene, three cephalospoprin antibiotics, glucose, hemoglobin and lipid on the kinetic Jaffé reaction and an enzymatic reaction for the determination of creatinine concentration were studied in bovine, canine, feline and equine serum. There were no obvious species' differences. The kinetic Jaffé reaction was unaffected by the addition of beta-carotene and hemoglobin. Acetone, cefazolin, cefoxitin, ceftiofur and glucose caused a positive bias while acetoacetic acid, bilirubin, and lipid caused a negative bias when added to the kinetic Jaffé reaction. The enzymatic reaction was unaffected by the addition of acetoacetic acid, acetone, beta-carotene, cefazolin, cefoxitin, glucose and hemoglobin while added lipid, bilirubin and ceftiofur caused a negative bias in the test results. Over all species and interferents, there was no difference in the precision of the two assay methods. In a series of sera from hospitalized patients, the two methods were highly correlated in a linear fashion. The enzymatic creatinine assay deals effectively with most interferents but has a greater cost and shorter shelf-life compared with the kinetic Jaffé reaction. 相似文献
74.
The rate of fatty acid synthesis of perirenal adipose tissue of fetal lambs decreased by 90% during the last month of gestation. There was also a 90% decrease in the activity of fatty acid synthetase during this period, but the activity of this enzyme exceeded lipogenic flux by a factor of 10. The activity of acetyl CoA carboxylase in the active state (initial activity) was very similar to the lipogenic flux in adipose tissue from lambs at 120 d of gestation; although activity decreased towards term, the decline was insufficient to account for the fall in rate of fatty acid synthesis. The study also shows that assay of acetyl CoA carboxylase in the active state of ovine adipose tissue and of caprine mammary gland requires the presence of citrate, thus differing from that for rat adipose tissue. Evidence that pyruvate carboxylase can interfere in the assay of acetyl CoA carboxylase also is presented. 相似文献
75.
76.
77.
A computer program was used to analyse data from a large commercial pig unit over two years to assess reproductive efficiency and the efficiency of weaner production. Monthly inspections of the farm and quarterly post mortem examinations of all dead pigs provided further information. The effects of controlled changes in management on production were assessed. Overall the number of piglets reared per sow per year was increased from 15-1 to 17-2 and the eight-week weights improved from a mean of 10-3 kg to 15-0 kg during the two year-study period. 相似文献
78.
P. B. O'Donovan A. Woldegebriel M. S. Taylor A. Gebrewolde 《Tropical animal health and production》1978,10(1):243-249
Summary Two experiments are described involving 33 crossbred (mainly Simmental and Jersey × Zebu) and 33 Zebu (Horro and Boran) bulls and steers. In experiment I, growth rates of crossbred and Zebu cattle rotationally grazed on either native pasture or Rhodes grass(Chloris gayana) were compared during a 140 day grazing period at a stocking rate of 2.4 animals/ha. In experiment II, growth rate of cattle rotationally grazed for 140 days on native pasture was compared with that of a similar group grazed on Rhodes grass either rotationally or continuously at a stocking rate of seven animals/ha.On native pasture the average daily gain by Zebu animals was similar to that of the crossbreds whilst on Rhodes grass liveweight gain of Zebu animals was lower than that of the crossbreds. Daily gains of cattle were significantly (P<0.01) greater on continuous compared with rotationally grazed Rhodes grass.
Rendimiento En Peso De Bovinos Cruzados Y Cebu En Pradera Nativa Y Pasto Rhodes
Resumen Se describen dos experimentos; el primero con 33 animales cruzados (Simmental y Jersey × Cebú) y el segundo con 33 Cebú (Horro y Boran) toros y novillos. En el experimento I, se compararon las ratas de crecimiento del ganado cruzado y del Cebú en pastoreo rotacional en pradera nativa o pasto Rhodes (Chloris gayana), durante 140 días, con una carga animal de 2.4 animales por hectárea. En el experimento II, se comparó la rata de crecimiento de un grupo de ganado en pastoreo rotacional en pradera nativa durante 140 días, con aquella de un grupo similar en pasto Rhodes con pastoreo rotacional o continuo, con una carga animal de siete por hectárea. En pradera nativa, el promedio de ganacia diaria de los animales Cebú fue similar a aquel del grupo de animales cruzados, mientras que en pasto Rhodes la ganancia de peso de los animales Cebú fue más baja que aquella de los animales cruzados. Las ganancias diarias de peso de los animales fueron significativamente (P<0.01) mayores en pastoreo contínuo, comparado con el pastoreo rotacional en pasto Rhodes.
Performances Ponderales De Zebus Et De Metis Zebus Entretenus Sur Des Paturages Naturels Et Das Paturages D'Herbe De Rhodes
Résumé Deux expériences utilisant 33 métis (principalement Simmental et Jersey x Zébu) et 33 zébus (Horro et Boran), taureaux et bouvillons sont décrites.Dans la première, les gains de poids des métis et des zébus entretenus à raison de 2,4 animal à l'hectate par rotation, soit sur des pâturages naturels ou sur de l'herbe de Rhodes ont été comparés durant 140 jours.Dans la seconde expérience, le taux d'accroissement pondéral du bétail entretenu, par rotations des pâturages, pendant 140 jours sur des pâturages naturels a été comparé avec celui d'un groupe identique d'animaux entretenus sur de l'herbe de Rhodes soit par rotation, soit de façon permanente à raison de 7 têtes à l'hectare sur les pâturages naturels; le gain journalier de poids par zébu a été semblable à celui des métis tandis que le gain de poids des zébus entretenus sur de l'herbe de Rhodes a été inférieur à celui des métis. Les gains journaliers de poids ont été significativement (P<0,01) plus élevés chez les animaux en pacage permanent comparés avec ceux obtenus par la rotation des pâturages d'herbe de Rhodes.相似文献
79.
80.