全文获取类型
收费全文 | 340篇 |
免费 | 42篇 |
专业分类
林业 | 29篇 |
农学 | 20篇 |
基础科学 | 1篇 |
52篇 | |
综合类 | 13篇 |
农作物 | 26篇 |
水产渔业 | 40篇 |
畜牧兽医 | 157篇 |
园艺 | 6篇 |
植物保护 | 38篇 |
出版年
2023年 | 3篇 |
2022年 | 14篇 |
2021年 | 20篇 |
2020年 | 17篇 |
2019年 | 26篇 |
2018年 | 16篇 |
2017年 | 15篇 |
2016年 | 21篇 |
2015年 | 17篇 |
2014年 | 18篇 |
2013年 | 18篇 |
2012年 | 27篇 |
2011年 | 31篇 |
2010年 | 16篇 |
2009年 | 14篇 |
2008年 | 14篇 |
2007年 | 14篇 |
2006年 | 11篇 |
2005年 | 9篇 |
2004年 | 11篇 |
2003年 | 7篇 |
2002年 | 9篇 |
2001年 | 6篇 |
2000年 | 1篇 |
1999年 | 3篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1995年 | 3篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1984年 | 2篇 |
1980年 | 1篇 |
1969年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有382条查询结果,搜索用时 46 毫秒
11.
12.
Machado Rui Godinho Sérgio Guiomar Nuno Gil Artur Pirnat Janez 《Landscape Ecology》2020,35(6):1291-1308
Landscape Ecology - The Portuguese montado is an agro-silvopastoral system, similar to the Spanish dehesa, known for its cultural, economic and ecological value. Despite its importance, contrasting... 相似文献
13.
Fagner Machado Ribeiro Mrio Lima Pedro Aurlio Tataíra da Costa Diego Machado Pereira Thony Assis Carvalho Tadeu Vilela de Souza Hortência Aparecida Botelho Fabyano Fonseca e Silva Adriano Carvalho Costa 《Aquaculture Research》2019,50(7):2004-2011
The objective of this work was to evaluate the association between morphometric variables and carcass characteristics in Pirapitinga. We used a thousand specimens of Pirapitinga with an average weight of 1,200 g, which were stunned, slaughtered, weighed, measured, and processed for morphometric and processing yield analysis, to obtain weights, carcass and fillet yields. Initially, the linearity of the variables was verified. Pearson's simple and partial correlation tests were performed between all metrics. Track analysis was performed considering the weights and yields of carcass and filet as dependent variables and the others as independent variables. Ridge regression models were used to eliminate the effects of multicollinearity among the independent variables. Observations showed that the simple correlations between body weights and yields were superior to the partial ones in terms of magnitude. The length and circumference of the specimens were the measures most linearly associated with weight, carcass weight and fillet with rib weight. As for carcass yield and fillet yield, linear correlation coefficients were low and not significant when associated with body weights. With the path analysis, we could observe significant positive correlations between the morphometric measurements for weight, carcass weight and fillet with rib weight. The standard length, body circumference and body circumference/body height ratio are the most correlated. The latter are the most important variables in the evaluation of body weights in Pirapitinga fish. They can serve as criteria for indirect selection in searching for fish with better carcass characteristics. As for fillet and carcass yields, the morphometric variables have not shown to be efficient for indirect selection. 相似文献
14.
15.
Navegantes LC Machado CR Resano NM Migliorini RH Kettelhut IC 《British poultry science》2003,44(1):149-154
1. The role of beta2-agonist and of cAMP in chick skeletal muscle proteolytic pathways and protein synthesis was investigated using an in vitro preparation that maintains tissue glycogen stores and metabolic activity for several hours. 2. In extensor digitorum longus (EDL) muscle total proteolysis decreased by 15 to 20% in the presence of equimolar concentrations of epinephrine, clenbuterol, a selective hbetaagonist, or dibutyryl-cAMP. Rates of protein synthesis were not altered by clenbuterol or dibutyryl-cAMP. 3. The decrease in the rate of total protein degradation induced by 10(-5)M clenbuterol was paralleled by a 44% reduction in Ca2+-dependent proteolysis, which was prevented by 10(-5)M ICI 118.551, a selective fbeta2antagonist. 4. No change was observed in the activity of the lysosomal, ATP-dependent, and ATP-independent proteolytic systems. Ca2+-dependent proteolytic activity was also reduced by 58% in the presence of 10(-4)M dibutyryl-cAMP or isobutylmethylxanthine. 5. The data suggest that catecholamines exert an inhibitory control of Ca2+-dependent proteolysis in chick skeletal muscle, probably mediated by fbeta2adrenoceptors, with the participation of a cAMP-dependent pathway. 相似文献
16.
Lucia T Corrêa MN Deschamps JC Bianchi I Donin MA Machado AC Meincke W Matheus JE 《Preventive veterinary medicine》2002,53(4):57-292
We evaluated stillbirth risk factors in two commercial swine farms of the Rio Grande do Sul State (south of Brazil). The study was conducted during 1 month in Farm A and during 2 months in Farm B, both during 1999. Data for all farrowings that occurred during the study period were recorded (101 for Farm A and 373 for Farm B), without interference in the farm management. In Farm A, 39% of all litters born during the period of interest had stillborn piglets and the stillborn risk for piglets was 12%. In Farm B, 25% of all litters had stillborn piglets whereas the stillborn risk was 2%. Variables considered as potential risk factors for stillbirths were: parity (1, 2–3, 4+); breed (purebred or crossbred); sow body-condition (normal or fat); use of oxytocin during parturition (yes or no); obstetric intervention through vaginal palpation (yes or no); farrowing duration (<4 or ≥4 h); mummified fetuses (yes or no); total litter size (<12 or ≥12 piglets); and litter birth weight (<11 or ≥11 kg). All stillborn piglets had their classification validated by necropsy. In multivariable logistic-regressions, the cases were the litters having at least one stillborn piglet. In Farm A, litters having at least 12 pigs and in which oxytocin was used during the parturition had 20.8-times-higher odds of stillborn occurrence. In Farm B, litters from sows having parity ≥4 had 2.2-times-higher odds of stillborn occurrence than litters from parity 2 to 3 females, litters having ≥12 pigs had 2.0-times-higher odds of a stillborn piglet than smaller litters and farrowings in which vaginal palpation was performed had 8.0-times-higher odds. Farrowing room management to minimize stillborn risk should target higher-parity females, large litters and optimization of practices of obstetric interventions. 相似文献
17.
18.
Vieira Aline Bomfim Restrepo Mariana Alvarez Auzenne Danielle Molina Kevin O’Sullivan Meghan Machado Marcus Vinicius Cavanaugh Sarah Marie 《Veterinary research communications》2022,46(2):527-535
Veterinary Research Communications - Obesity is considered the most common nutritional disease of dogs. Even though overt obesity is more likely to impair health, even moderately overweight dogs... 相似文献
19.
Despite many studies of the percent loss of hydraulic conductivity in excised branches, there is doubt as to whether cutting stems in air introduces unnatural embolism into the xylem at the cut surface. To address this question, hydraulic conductivity was measured in seedlings of northern red oak (Quercus rubra L.) and rooted scions of eastern cottonwood (Populus deltoides Bartr. ex Marsh.) that had been droughted in pots. Results indicate that in situ dehydration produced a very similar vulnerability curve (% loss of conductivity versus water potential) to those previously obtained by bench-top dehydration of excised branches of eastern cottonwood and red oak. In eastern cottonwood cuttings, conductivity loss increased sharply below water potentials of -1.0 MPa, with 100% loss of conductivity occurring by -2.0 MPa, whereas conductivity loss in red oak seedlings was more gradual, i.e., increasing below -1.5 MPa and sustaining 100% loss of conductivity by about -4.0 MPa. 相似文献
20.
Reproductive Performance and Reconception of Nellore Cows According to Their Pure‐ or Cross‐Bred Calves
下载免费PDF全文
![点击此处可从《Reproduction in domestic animals》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The objective of the present research was to evaluate the effect of a calf's genetic group on the productive and reproductive efficiency of its Nellore dam. Fixed‐time artificial insemination was applied to 800 cows using semen extracted from Nellore, Simmental and Angus Red bulls. Four hundred eleven cows calved, producing 119 Nellore, 103 ½Simmental–½Nellore and 189 ½Nellore–½Angus Red calves. The second mating period, which paired Nellore cows with Simmental bulls, was initiated 10 days after parturitions began and lasted for 5 months. Based on the two successive parturitions, the cumulative parturition rate for calving periods of 3, 4 and 5 months was calculated. Although no significant difference was observed for birth weight among the genetic groups, cross‐bred calves weighed, on average, 10% more than did pure‐bred calves at the age of 205 days. Nellore dams experienced a gestation period that was 7 days longer than did the cross‐bred dams, and the former showed a higher parturition rate at 90 and 120 days of the calving season, but not at 150 days (calving rates of 80.6, 76.4 and 76.2% for mothers of Nellore, ½Nellore–½Angus Red and ½Nellore–½Simmental, respectively, p > 0.05). At 90 and 120 days, Nellore dams produced more kg of calf per mated dam. In conclusion, in a short breeding season, Nellore dams nursing pure‐bred Nellore calves were found to have a higher biological efficiency compared with Nellore dams nursing cross‐bred calves. 相似文献