全文获取类型
收费全文 | 359篇 |
免费 | 35篇 |
专业分类
林业 | 28篇 |
农学 | 5篇 |
基础科学 | 3篇 |
64篇 | |
综合类 | 32篇 |
农作物 | 18篇 |
水产渔业 | 34篇 |
畜牧兽医 | 177篇 |
园艺 | 7篇 |
植物保护 | 26篇 |
出版年
2023年 | 6篇 |
2022年 | 6篇 |
2021年 | 16篇 |
2020年 | 20篇 |
2019年 | 16篇 |
2018年 | 15篇 |
2017年 | 14篇 |
2016年 | 22篇 |
2015年 | 18篇 |
2014年 | 25篇 |
2013年 | 21篇 |
2012年 | 30篇 |
2011年 | 32篇 |
2010年 | 26篇 |
2009年 | 17篇 |
2008年 | 16篇 |
2007年 | 22篇 |
2006年 | 9篇 |
2005年 | 8篇 |
2004年 | 11篇 |
2003年 | 7篇 |
2002年 | 3篇 |
2001年 | 8篇 |
2000年 | 4篇 |
1999年 | 1篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 7篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
排序方式: 共有394条查询结果,搜索用时 15 毫秒
41.
PB Fernandes KO Marques FR de Araujo Neto DP de Oliveira NA Hurtado‐Lugo RR Aspilcueta‐Borquis H Tonhati 《Reproduction in domestic animals》2016,51(3):428-434
Because of the importance of reproduction in stock breeding systems, it is necessary to find selection criteria that increase reproductive efficiency. The aim of this study was to estimate genetic parameters for the probability of conception on first service (PROB) in Murrah heifers, and its association with other traits of economic interest [age at first calving (AFC), service period, calving interval and milk yield at 270 days], with the purpose of evaluating their use as selection criteria. Reproductive information and first lactation records of 1200 Murrah heifers were used to perform two‐trait analyses between PROB and the other characteristics. Bayesian inference was used to estimate the variance components, considering PROB as threshold and the other as linear factors. The results demonstrate that this trait has heritability of 0.15, indicating the possibility of a genetic gain by using it for selection. With respect to the genetic correlation estimates, the only high‐magnitude association was with AFC (?0.899), which is the current criterion indicating sexual precocity of females. In the light of the parameters estimated, the first‐service pregnancy rate is an alternative for indication of sexual precocity, although presenting a smaller genetic gain than the current standard AFC. Nevertheless, additional research should be conducted regarding this trait to assess the economic importance of its use in dairy buffalo production systems. 相似文献
42.
Effects on erosion of two post-fire management practices: clear-cutting versus non-intervention 总被引:1,自引:0,他引:1
The different erosion responses derived from two contrasting post-fire management approaches were evaluated: the clear-cutting and immediate removal of the burnt trees and; the non-intervention, that is, leaving the vegetation untouched and the burnt trees standing. Erosion rates were obtained from 200 m2 experimental plots, large enough to include the complete processes of rill and inter-rill erosion. Erosion rates of the clear-cut plot were very similar to those of the non-modified plot. Part of the burnt trees was still economically usable. The trees left in situ gradually decayed and were tumbled by the wind; the fire risk incremented. The opening of timber track networks without conservation measures was one of the most important erosion problems associated with clear-cutting. The complementary practice of brushwood dike-construction would need a preliminary study before being applied. 相似文献
43.
Mohammad Redwanur Rahman Md. Asaduzzaman Md. Mahiuddin Zahangir SM Rashadul Islam Sk Ahmad‐Al Nahid Durin Akter Jahan Yahia Mahmud Mohammed Nurul Absar Khan 《Aquaculture Research》2020,51(6):2555-2572
Soft‐shell crab, a newly moulted crab having non‐calcified and hydrated soft exoskeleton, farming has been increasing tremendously in recent years throughout the world due to its high market price and consumer preferences. However, high aggressiveness and cannibalistic behaviour of mud crab limit its culture to an individual chamber system which ultimately makes the soft‐shell mud crab farming space and labour‐intensive. Therefore, the aim of this study was to improve the efficiency of soft‐shell crab production by autotomy of the claw and/or walking legs to reduce the moulting duration and intensify the culture system through double stocking in the existing individual chamber culture system. To achieve our objectives, a series of experiment were conducted at both indoor and on‐farm levels by removing the claw and/or walking legs of Scylla olivacea for two consecutive moulting cycles. Results showed that both claw ablation significantly (p < .01) shortened the moulting duration and increased the carapace width, weight gain, specific growth rate, feeding efficiency and yield parameter compared to the non‐ablated crabs more prominently at 1st moulting than the 2nd moulting in both indoor and on‐farm trials. Ablation of all walking legs while keeping the claw intact did not significantly influence (p > .05) the moulting duration and carapace width, but significantly (p < .01) improved the specific growth rate, weight gain, feeding efficiency and yield parameters at 1st moulting compared to the non‐ablation and unilateral three walking leg ablation groups. However, ablation of all appendages (both claw and walking legs) showed significant (p < .01) improvements of carapace width, weight gain, specific growth rate, feeding efficiency and yield parameters, and shortened the moulting duration up to 23 days from 34 days during 1st moulting and up to 27 days from 40 days at 2nd moulting. The survivals of different autotomized mud crabs were statistically non‐significant (p > .05) to the non‐autotomized crabs in various indoor and on‐farm trials. Besides improving the production performances, ablation of bilateral claw and all appendages allowed to double the stocking density in the existing individual chamber‐based soft‐shell crab farming that enhanced the production about threefold higher than the existing individual chamber‐based culture system. Finally, our results suggest that autotomy could be a promising technology for the commercial farming of soft‐shell mud crab in near future. 相似文献
44.
45.
Raissa Rachel Salustriano da Silva-Matos Gabriel Barbosa da Silva Jr Adenaelson de Souza Marques Maciel Lima Monteiro Josy Anteveli Osajima 《Archives of Agronomy and Soil Science》2016,62(3):445-455
The identification of alternative substrates suitable for seedling production is very important, while boron nutrition is also relevant due to plant requirement and its difficult management. Thus, four experiments were carried out from October 2012 to April 2013 to evaluate the effect of substrates using decomposed buriti (Mauritia vinifera Mart.) stem (DBS) and boron fertilizing for seedling production of yellow passion fruit (Passiflora edulis Sims). The experimental design was completely randomized in factorial scheme 6 × 2 + 1, referring to the substrates [S1: DBS, S2: soil and sand 1:1 (20%) + DBS (80%), S3: soil and sand 1:1 (40%) + DBS (60%), S4: soil and sand 1:1 (60%) + DBS (40%), S5: soil and sand 1:1 (80%) + DBS (20%), S6: commercial substrate (additional treatment) and S7: soil, sand and manure 1:1:2] with and without boron. The seedling emergence, emergence rate, plant height, stem diameter, root length, root volume and dry mass of roots and shoots were recorded. The substrates S2 (without B fertilizing) and S4 (B fertilized with 0.5 mg dm?3) produced seedlings with more than 3.0 g of shoot dry mass and at least 30 cm in height, and can be used for production of high-quality yellow passion fruit seedlings. 相似文献
46.
Nuno Figueiredo Corina Carranca Henrique Trindade José Pereira Piebiep Goufo João Coutinho Paula Marques Rosa Maricato Amarilis de Varennes 《Paddy and Water Environment》2015,13(4):313-324
The present field experiment was conducted during two consecutive cropping seasons in central Portugal to study the effects of simultaneous elevation of carbon dioxide concentration ([CO2]) (550 μmol mol?1) and air temperature (+2–3 °C) on japonica rice (Oryza sativa L. “Ariete”) yield, crop duration, and SPAD-values across the seasons compared with the open-field condition. Open-top chambers were used in the field to assess the effect of elevated air temperature alone or the combined effect of elevated air temperature and atmospheric [CO2]. Open-field condition was assessed with randomized plots under ambient air temperature and actual atmospheric [CO2] (average 382 μmol mol?1). Results obtained showed that the rice “Ariete” had a moderate high yielding under open-field condition, but was susceptible to air temperature rise of +2–3 °C under controlled conditions resulting in reduction of grain yield. The combined increase of atmospheric [CO2] with elevated air temperature compensated for the negative effect of temperature rise alone and crop yield was higher than in the open-field. SPAD-readings at reproductive stage explained by more than 60 % variation the straw dry matter, but this finding requires further studies for consolidation. It can be concluded that potential increase in air temperature may limit rice yield in the near future under Mediterranean areas where climate change scenario poses a serious threat, but long term field experiments are required. 相似文献
47.
Saulo da Luz e Silva Paulo Roberto Leme Soraia Marques Putrino Anglica Simone Cravo Pereira Amaury Camilo Valinote Jos Carlos Machado Nogueira Filho Dante Pazzanese Duarte Lanna 《Livestock Science》2009,122(2-3):290-295
The purpose of this work was to evaluate the fatty acid composition of the Longissimus muscle from carcasses of Nellore steers fed diets with calcium salts of fatty acids (CSFA) and high moisture corn. Forty eight steers were fed during 70 days four diets containing dry corn (DC), high moisture corn (HM), dry corn plus CSFA (DC-CSFA) or high moisture corn plus CSFA (HM-CSFA). Fatty acid composition of the Longissimus muscle was determined by gas chromatography. Corn type had no effect on the ether extract percentage and in the content of the majority of the fatty acids, although steers fed HMC showed higher levels of polyunsaturated fatty acids and polyunsaturated/saturated ratio. Feeding CSFA increased ether extract percentage but had no effect on total of saturated, unsaturated and saturated: unsaturated ratio. Both high moisture corn and calcium salts of fatty acids increased CLA (cis9, trans11) and total CLA concentrations in intramuscular fat. 相似文献
48.
A. I. D. C. Marques J. Tattersall D. J. Shaw E. Welsh 《The Journal of small animal practice》2009,50(4):162-166
O bjectives : The objective of this study was to evaluate the relationship between the volume of fluid being produced at the time of thoracostomy drain removal and the time to hospital discharge in dogs and cats.
M ethods : Records of 101 dogs and 26 cats with thoracostomy drains were reviewed. Three subgroups were created according to the reason for thoracostomy drain placement: P (postsurgical), A (air) and F (fluid). A generalised linear model with Poisson Errors was performed to test the relationship between the volume of fluid produced at the time of thoracostomy drain removal and the time to discharge. The volume of fluid produced and the time to discharge were compared between species and subgroups.
R esults : No significant relationship was found between the volume of fluid produced at the time of thoracostomy drain removal and the time to discharge in either species or between the time to discharge and the reason for thoracostomy drain placement. Animals with a volume of fluid higher than 2 ml/kg/day at the time of thoracostomy drain removal did not have increased hospitalisation times.
C linical S ignificance : Thoracostomy drain can be removed, without clinical compromise, when the volume of fluid produced exceeds 2 ml/kg/day. However, other clinical parameters must be taken into consideration. 相似文献
M ethods : Records of 101 dogs and 26 cats with thoracostomy drains were reviewed. Three subgroups were created according to the reason for thoracostomy drain placement: P (postsurgical), A (air) and F (fluid). A generalised linear model with Poisson Errors was performed to test the relationship between the volume of fluid produced at the time of thoracostomy drain removal and the time to discharge. The volume of fluid produced and the time to discharge were compared between species and subgroups.
R esults : No significant relationship was found between the volume of fluid produced at the time of thoracostomy drain removal and the time to discharge in either species or between the time to discharge and the reason for thoracostomy drain placement. Animals with a volume of fluid higher than 2 ml/kg/day at the time of thoracostomy drain removal did not have increased hospitalisation times.
C linical S ignificance : Thoracostomy drain can be removed, without clinical compromise, when the volume of fluid produced exceeds 2 ml/kg/day. However, other clinical parameters must be taken into consideration. 相似文献
49.
A. I. de Castro Marques F. Hipwell D. A. Yool 《The Journal of small animal practice》2009,50(11):619-623
A seven-year-old miniature dachshund was presented with a large contaminated bite wound centred on the left costal arch. Survey radiographs revealed a pneumomediastinum, a mid-body fracture of the left 11th rib and luxation of the xiphisternum. The compromised skin, ribs, xiphisternum, diaphragm and abdominal wall were surgically debrided. This resulted in a large combined thoracic and abdominal wall defect. The thoracic cavity was closed by diaphragmatic advancement. The abdominal wall defect was partially closed by advancing local abdominal musculature. A cranial abdominal mid-line defect remained and was repaired using two sheets of lyophilised porcine small-intestinal submucosa. Dehiscence of the skin exposing the SIS graft was seen but the abdominal repair remained intact. Eighteen months after the initial injury, the dog remained clinically well and no associated complications were reported. 相似文献
50.
David Borchers Tiago Marques Thorvaldur Gunnlaugsson Peter Jupp 《Journal of Agricultural, Biological & Environmental Statistics》2010,15(3):346-361
Distance sampling methods assume that distances are known but in practice there are often errors in measuring them. These
can have substantial impact on the bias and precision of distance sampling estimators. In this paper we develop methods that
accommodate both systematic and stochastic measurement errors. We use the methods to estimate detection probability in two
surveys with substantial measurement error. The first is a shipboard line transect survey in the North Sea in which information
on measurement error comes from photographically measured distances to a subset of detections. The second is an aerial cue-counting
survey off Iceland in which information on measurement error comes from pairs of independently estimated distances to a subset
of detections. Different methods are required for measurement error estimation in the two cases. We investigate by simulation
the properties of the new estimators and compare them to conventional estimators. They are found to perform better than conventional
estimators in the presence of measurement error, more so in the case of cue-counting and point transect estimators than line
transect estimators. An appendix on the asymptotic distributions of conditional and full likelihood estimators is available
online. 相似文献