全文获取类型
收费全文 | 190篇 |
免费 | 19篇 |
专业分类
林业 | 17篇 |
农学 | 13篇 |
24篇 | |
综合类 | 4篇 |
农作物 | 10篇 |
水产渔业 | 31篇 |
畜牧兽医 | 78篇 |
园艺 | 7篇 |
植物保护 | 25篇 |
出版年
2023年 | 3篇 |
2022年 | 5篇 |
2021年 | 9篇 |
2020年 | 15篇 |
2019年 | 19篇 |
2018年 | 16篇 |
2017年 | 8篇 |
2016年 | 13篇 |
2015年 | 3篇 |
2014年 | 14篇 |
2013年 | 16篇 |
2012年 | 11篇 |
2011年 | 8篇 |
2010年 | 8篇 |
2009年 | 15篇 |
2008年 | 9篇 |
2007年 | 8篇 |
2006年 | 3篇 |
2005年 | 5篇 |
2004年 | 1篇 |
2003年 | 5篇 |
2002年 | 3篇 |
2001年 | 1篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有209条查询结果,搜索用时 343 毫秒
81.
Taís da Silva Lopes Thiago Mendes de Freitas Rosngela K. Jomori Dalton Jos Carneiro Maria Clia Portella 《Journal of the World Aquaculture Society》2014,45(1):15-27
Skeletal anomalies in fish are frequent, representing a major problem for the aquaculture industry. The anomalies usually arise in the larval phase and worsen, persist, or recover over the ensuing stages of development. In addition to impairing larval quality, they compromise the growth, health, and food conversion of fish, lowering their economic value. This study evaluated the occurrence of skeletal anomalies in pacu larvae during the first 30 d of development. The newly hatched larvae of six breeding pairs taken from the Paranapanema River (offspring A, B, C, D, E, and F) and subjected to induced spawning were reared separately for 30 d, feeding on live prey (Artemia nauplii). Nearly 20 larvae from each breeding pair were killed and stored 1, 2, 4, 6, 8, 10, 13, 16, 19, 22, 25, and 30 days post‐hatching. The larvae were stained to differentiate cartilage and bones and examined under a stereo microscope. A total of 1310 larvae were checked for the presence (1) or absence (0) of anomalies in the head, vertebral column, and fins. Associations between growth parameters (total length [TL] vs. standard length [SL]; SL vs. vertebral column length [VL]) were obtained by regression. Correspondence analysis was used to correlate data on the different parameters evaluated. On completion of observation, larvae from pair E had the highest SL, whereas offspring F were the shortest. All types of skeletal anomalies were detected in the larvae irrespective of the offspring, affecting the normal growth of pacu larvae obtained from wild‐caught breeders. 相似文献
82.
Pollyanna de Moraes Frana Ferreira Lidiane da Silva Nascimento Devlynn Coelho Dias Diogo Magalhes da Veiga Moreira Ana Lúcia Salaro Mariella Bontempo Duca de Freitas Antonio Policarpo Souza Carneiro Jener Alexandre Sampaio Zuanon 《Journal of the World Aquaculture Society》2014,45(1):28-34
This study aimed to evaluate the potential of oregano oil as a growth promoter for the yellowtail tetra, Astyanax altiparanae. The fish (1.46 ± 0.09 g) were distributed into twenty‐four 60‐L aquaria at a stocking density of 0.5 fish/L. Six isonitrogenous (350 g crude protein/kg) and isocaloric (4272 kcal gross energy/kg) diets containing 0.0, 0.5, 1.0, 1.5, 2.0 and 2.5 g/kg of oregano oil were evaluated. At the end of 90 d there was a quadratic effect of oregano oil levels for weight gain, specific growth rate, protein efficiency ratio and carcass weight, and the estimated values to maximize these variables were between 0.2 and 0.6 g/kg. There was also a quadratic effect on the feed conversion ratio, and the estimated value to improve this variable was 0.62 g/kg. A positive linear effect of the treatments was observed for muscle glycogen. With increased levels of oregano oil in the diet, there was a reduction in dry matter and ether extract and an increase in the protein content of the carcass. Thus, it can be concluded that oregano oil, at the level of 0.5 g/kg, acts as a growth promoter for A. altiparanae by improving growth performance and carcass composition. 相似文献
83.
The removal or maintenance of harvest residues in eucalypt plantations may influence site quality and productivity. Removal of slash from the site may facilitate further management operations and provide a valuable energy resource, but effects on site productivity and sustainability for a rotation time span were not yet assessed under Mediterranean conditions. Therefore, a study was carried out to assess the effects of slash (harvest residues plus forest floor litter) management and soil preparation options on stand productivity and understory vegetation dynamics, hypothesizing that those options influence tree growth, forest floor dynamics and understory biomass and diversity. An experiment was installed in West Central Portugal, consisting on: removal of slash without soil preparation (R); broadcast of harvest residues on the soil surface without soil disturbance (S); as in S, but concentrating the woody debris between tree rows (W); incorporation of slash into the soil by harrowing (I); removal of slash followed by harrowing (RH); and as in I followed by ripping (IS). The experiment was monitored for a rotation time span (140 months). Maintenance of slash followed by deep soil disturbance led to the highest wood production, but differences between treatments were not significant (p > 0.05). Forest floor load and understory biomass were also similar between treatments. Ground vegetation played an important role on nutrient cycling in early rotation stages, such effect being irrespective on slash management options. Incorporation of slash into the soil followed by ripping is probably the best option to match production and environmental sustainability of eucalypt plantations in Mediterranean conditions. 相似文献
84.
Luisa Cunha Carneiro Adolfo Firmo Ferreira Mariana Padua João Paulo Saut Antonio Sergio Ferraudo Ricarda Maria dos Santos 《Tropical animal health and production》2014,46(8):1435-1439
In dairy cattle, uterine infections are not life threatening and often unavoidable; however, they reduce fertility and increase the production costs of properties. The aim of this study was to evaluate the incidence of subclinical endometritis from 32 to 70 days in milk (DIM) and its effects on the reproductive performance of crossbred dairy cows. Lactating cows (Holstein/Gir; n?=?172), with no history of retained placenta, without clinical signs of uterine infection were used. The body condition score (BCS) was evaluated on a scale from 1 to 5. Ultrasound examination was performed to evaluate uterine lining and ovarian activity, while vaginal mucus was analyzed by gloved hand. The diagnosis of subclinical endometritis was performed by endometrial cytobrush technique. The samples were collected, stained, and examined microscopically; positive cases for subclinical endometritis were considered with the presence of ≥5 % of neutrophils. Later, the cows were submitted to conventional artificial insemination or timed artificial insemination. The incidence of subclinical endometritis in the herd was 26 %, and this was not affected by the season of calving, presence of corpus luteum, DIM, and parity. Cows with a BCS ≤2.50 had a higher incidence of subclinical endometritis. The conception rate to first insemination and pregnancy rate at 150 days postpartum were not influenced by the presence of subclinical endometritis in crossbred dairy cows. 相似文献
85.
86.
Fontes-Sousa AP Moura C Carneiro CS Teixeira-Pinto A Areias JC Leite-Moreira AF 《Veterinary journal (London, England : 1997)》2009,181(3):326-331
Limited data are available on the use of more recent echocardiographic parameters in the rabbit. Echocardiographic examination, including conventional echocardiography and tissue Doppler imaging (TDI), was performed on 26 male New Zealand white rabbits under ketamine–midazolam sedation. Particular emphasis was placed on the more recent systolic and diastolic parameters, such as myocardial performance index (Tei index) and mitral annular motion (from septal and lateral sides of the left ventricle) obtained using pulsed TDI.Parameters that assessed systolic and diastolic function (fractional shortening, Tei index, and maximal mitral E- and A-wave velocities) were comparable to those reported in the literature for rabbits in the awake state. The less cardiodepressive anaesthetic protocol could offer a good alternative in performing echocardiographic evaluation whenever such caution is necessary. TDI is feasible in healthy rabbits and potentially suitable for the investigation of left ventricle systolic and diastolic function. 相似文献
87.
Mapping QTLs for aluminum tolerance in maize 总被引:11,自引:0,他引:11
Fernando Enrique Ninamango-Cárdenas Claudia Teixeira Guimarães Paulo Roberto Martins Sidney Netto Parentoni Newton Portilho Carneiro Maurício Antônio Lopes José Roberto Moro Edilson Paiva 《Euphytica》2003,130(2):223-232
Aluminum toxicity is one of the major constraints for plant development in acid soils, limiting food production in many countries.
Cultivars genetically adapted to acid soils may offer an environmental compatible solution, providing a sustainable agriculture
system. The aim of this work was to identify genomic regions associated with Al tolerance in maize, and to quantify the genetic
effects on the phenotypic variation. A population of 168F3:4 families derived from a cross between two contrasting maize inbred lines for Al tolerance was evaluated using the NSRL and
RSRL parameters in nutrient solution containing toxic level of aluminum. Variance analyses indicated that the NSRL was the
most reliable phenotypicindex to measure Al tolerance in the population, being used for further QTL mapping analysis. RFLP
and SSR markers were selected for bulked segregant analysis, and additional SSR markers, flanking the polymorphisms of interest,
were chosen in order to saturate the putative target regions. Seven linkage groups were constructed using 17 RFLP and 34 SSR
markers. Five QTLs were mapped on chromosomes 2, 6 and 8, explaining 60% of the phenotypic variation. QTL4 and marker umc043 were located on chromosomes 8and 5, close to genes encoding for enzymes involved in the organic acids synthesis
pathways, a widely proposed mechanism for Al tolerance in plants. QTL2 was mapped in the same region as Alm2,also associated with Al tolerance in maize. In addition, dominant and additive effects were important in the control of this
trait in maize.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
88.
D. Hatch H. Trindade L. Cardenas J. Carneiro J. Hawkins D. Scholefield D. Chadwick 《Biology and Fertility of Soils》2005,41(4):225-232
An automated laboratory soil incubation system enabled the effects on gaseous emissions from a soil to be quantified accurately, when amended with slurry plus a nitrification inhibitor: dicyandiamide (DCD), or 3,4-dimethylpyrazole phosphate (DMPP). Nitrification inhibitors applied with slurry under simulated Portuguese conditions were very efficient in reducing N2O emission, and did not increase CH4 emissions significantly, when the soil was predominantly aerobic. The inhibitors were also indirectly effective in reducing N2O emissions due to denitrification during a subsequent anaerobic phase. All gaseous emissions followed strong diurnal patterns that were positively correlated with soil temperature and obeyed a Q10=2 relationship. The widespread use of DCD and DMPP inhibitors with slurry applied to Portuguese soils could have the potential to reduce N2O emissions from this source by ten- to 20-fold. 相似文献
89.