全文获取类型
收费全文 | 336篇 |
免费 | 41篇 |
国内免费 | 1篇 |
专业分类
林业 | 32篇 |
农学 | 15篇 |
基础科学 | 2篇 |
32篇 | |
综合类 | 22篇 |
农作物 | 15篇 |
水产渔业 | 32篇 |
畜牧兽医 | 200篇 |
园艺 | 6篇 |
植物保护 | 22篇 |
出版年
2023年 | 3篇 |
2022年 | 6篇 |
2021年 | 15篇 |
2020年 | 24篇 |
2019年 | 32篇 |
2018年 | 26篇 |
2017年 | 19篇 |
2016年 | 23篇 |
2015年 | 11篇 |
2014年 | 16篇 |
2013年 | 24篇 |
2012年 | 23篇 |
2011年 | 15篇 |
2010年 | 13篇 |
2009年 | 16篇 |
2008年 | 14篇 |
2007年 | 14篇 |
2006年 | 11篇 |
2005年 | 8篇 |
2004年 | 8篇 |
2003年 | 7篇 |
2002年 | 5篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 6篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有378条查询结果,搜索用时 15 毫秒
11.
Trawling for cephalopods off the Portuguese coast—Fleet dynamics and landings composition 总被引:1,自引:0,他引:1
Tereza Fonseca Aida Campos Manuel Afonso-Dias Paulo Fonseca Joo Pereira 《Fisheries Research》2008,92(2-3):180-188
Fleet dynamics was addressed for three cephalopod taxa of commercial interest, the squid Loligo vulgaris, the octopuses Octopus vulgaris and Eledone cirrhosa, and the cuttlefish Sepia officinalis, for 48 trawlers of the fish trawling fleet. Landing profiles (LP) were identified based on the species composition of the landings using hierarchical cluster analysis. Four out of a total of 12 different LP were related to cephalopods and other species associated with them.The effects on the landing proportions of a number of variables, year, season and vessel, are analysed for each of the species studied using generalized linear models (GLM). The factor “vessel”, including an ensemble of technical characteristics as well as the abilities of individual skippers, explained most of the model deviance, strongly reinforcing the existence of a fleet component dedicated to catch cephalopods. However, time also explains much of the variation found in the data.Seasonal alternation between landings of octopodidae and cuttlefish was observed within a small group of old trawlers operating mainly off the south coast, following the abundance cycles of these species. For a larger group of more modern trawlers, operating off the western coast, inter-annual shift between octopus and squid was found, together with a well marked seasonal pattern between the catches of cephalopods and horse mackerel.Spatial patterns of activity were identified using vessel monitoring system (VMS) data available for trawlers in Portugal, demonstrating the existence of cephalopod targeting strategies in Portuguese fish trawling activities. 相似文献
12.
A Répási JF Beckers J Sulon A Karen J Reiczigel O Szenci 《Reproduction in domestic animals》2005,40(5):436-442
Lactating dairy cows (n = 72) with a mature corpus luteum (CL) (diameter of > or = 17 mm) determined by ultrasonography and having a follicle with a diameter of > or = 10 mm were randomly assigned to four groups. Cows were treated with cloprostenol i.m. once or twice, or with dinoprost i.m. once or twice with an 8-h interval. The ovaries of each cow were scanned daily by transrectal ultrasonography to measure the changes in the areas of CL and the largest follicle and to determine the occurrence of ovulation. Oestrus was verified twice daily. In addition, blood sample was withdrawn from each cow daily for measuring progesterone (P4) concentrations. Significant decreases in the percentage changes relative to areas of CL and P4 concentrations or increases in the percentage changes in the area of the largest follicle on day 0 were detected in each group during the experiment. However, the type of the drug and the number of the treatments had no significant effect on those parameters. Cows ovulated with or without showing oestrus (group A) and cows exhibiting no oestrus and ovulation (group B) were also evaluated. In contrast to the mean area of the CL and the mean concentration of P4 on day 0, the mean area of the largest follicles between the two groups on day 0 differed significantly. Significant decreases in the percentage changes relative to the area of the CL and P4 concentration or increases in the percentage changes relative to the area of the largest follicle during the experiment were detected in both groups; however, there were no group differences. Treatment of dairy cows with two injections of prostaglandins (cloprostenol or dinoprost) at an 8-h interval resulted in more cows being observed in oestrus within 5 days after treatment and having significantly higher pregnancy rate than those treated with a single prostaglandin injection. 相似文献
13.
Recent evidence implicates fiber type proportions as playing a role in meat eating quality, and in pigs it has been suggested that the slow oxidative fibers contribute to both juiciness and tenderness. The fiber distribution in pigs is different from that found in most other species, in which the various types of skeletal muscle fiber are distributed in a "checkerboard" pattern, because in pigs the slow oxidative fibers have a clustered distribution. The initial processes leading to fiber clustering are likely to occur during myogenesis, but the precise mechanistic aetiology of this patterning and whether the slow oxidative fiber clusters occur in a random or ordered fashion is unknown. In the present study longissimus thoracis muscle from Large White crossbred pigs was sampled at the 10th rib, 48 h postmortem. Transverse cryo-sections were cut and histochemically stained to allow the identification of the main muscle fiber types: slow oxidative, fast glycolytic, and fast oxidative glycolytic. Images of the sections were captured and analyzed using point processes and Voronoi Tesselations to examine the randomness and spatial distribution of the clusters of slow oxidative fibers found in pig longissimus thoracis muscle. The results showed that an assumption of complete spatial randomness can be rejected and that a mathematical model incorporating a minimum distance of 1.7 to 2.0 microm between cluster centers produced fiber patterns similar to those observed in the original transverse sections of the muscle. In addition, if it assumed that the central fiber in each cluster is derived from primary myoblast progenitors, these results suggest that there may be some degree of repulsion between the primary fibers during the initial stages of cluster formation. The mechanistic basis of such repulsion is not clear, but it is speculated that secreted factors, such as sonic hedgehog or myostatin may play a role. 相似文献
14.
The recent upgrade in IVP technology seen in cattle can be adapted to embryo production in small ruminants to overcome limitations exhibited by surgical procedures on preserving the reproductive potential of donors and the efficiency of embryo production. The aim of the present study was to assess the current procedures used in cattle for the production of IVP embryos in goats and sheep based on laparoscopic-aided ovum pick-up (LOPU) supplied oocytes. Sexually matured goat and sheep donors were treated during the breeding season with FSH and subjected to laparoscopic-guided follicular puncture under general anaesthesia. The collected cumulus-oocyte complexes were matured in medium 199 and fertilized by frozen-thawed spermatozoa using Talp medium supplemented with heparin and oestrus-sheep serum. Cleaved ova were either cultured in sheep in vitro fertilization medium plus amino acids or transferred to sheep oviducts. Blastocyst rate, hatching rate and development rate up to term were used as markers of embryo function. The results obtained for goat and sheep involving 30 and 35 donors respectively (10 and 9 LOPU sessions) were 81.2% and 85.2% of oocyte collection rate; 88.3% and 98.6% oocyte incubation rate; 85.6% and 76.0% fertilization rate; 82.4% and 93.4% of cleavage rate; 50.0% and 61.5% IVP blastocyst rate; 42.1% and 45.5% blastocyst rate in oviducts; 73.0% and 66.7% embryo survival up to term, respectively. The results are comparable to those obtained in small ruminants and in bovines suggesting that requirements for embryo production and development are similar. 相似文献
15.
Electro-acupuncture and Chinese herbs for treatment of cervical intervertebral disk disease in a dog
Ayne Murata Hayashi Júlia Maria Matera Tatiana Soares da Silva Ana Carolina Brand?o de Campos Fonseca Pinto Sílvia Renata Gaido Cortopassi 《Journal of veterinary science (Suw?n-si, Korea)》2007,8(1):95-98
A non-ambulatory dog with tetraparesis following a pain episode that had evolved over 2 months was submitted for medical treatment and diagnosed with intervertebral disk disease at C3-C4 and dorsal extradural compression at C1-C2 and C3-C4 using myelography and computed tomography. The dog experienced ambulation recovery after 15 days of treatment with only electroacupuncture and Chinese herbal medicine, with marked improvement occurring after only 10 treatments. Six months of follow-up demonstrated that the dog was stable and had no recurrence of symptoms. Therefore, it was concluded that the combination of electroacupuncture and Chinese herbal medicine was responsible for motor rehabilitation. 相似文献
16.
B.P.A. Fonseca MS A.L.G. Alves PhD J.L.M. Nicoletti PhD A. Thomassian PhD C.A. Hussni PhD S. Mikail DVM 《Journal of Equine Veterinary Science》2006,26(11):507-516
The object of the current study was to evaluate the efficacy of thermography and ultrasonography in the diagnosis of thoracolumbar lesions in Quarter Horse athletes and associate the different types of lesions found with the athletic modality practiced. Twenty-four horses were admitted to the Surgery Service for Large Animals of the Veterinary and Animal Science Faculty, UNESP, Botucatu, Brazil, with complaints of back problems. All the horses were submitted for physical examinations to confirm the existence of thoracolumbar alterations and then for thermography and ultrasonography. Thermography was used to map the lesioned areas of this region and ultrasonography for lesion characterization. The lesions found were supraspinous desmitis, interspinous desmitis, dorsal intervertebral osteoarthritis, and impingement of the spinous processes or kissing spines. The existence of a relation between the type of event practiced by the horse and the type of lesion found was determined. In horses that competed in the barrel race, a predominance of lesions in the thoracic caudal, thoracolumbar, and cranial lumbar regions occurred, with intervertebral osteoarthritis and interspinous desmitis being the most common. In cutting horses, most of the lesions were observed in the caudal lumbar region, whereas horses competing in reining showed a preferential location for lesions in the middle lumbar, with a predominance of supraspinous desmitis and myositis. Thermography associated with ultrasonography was shown to be efficient in the diagnosis of the thoracolumbar lesions of these horses. 相似文献
17.
18.
Denise R. Freitas Leorges M. Fonseca Fernando N. Souza Cristiane V. G. Ladeira Soraia A. Diniz João Paulo A. Haddad Diêgo S. Ferreira Mônica M. O. P. Cerqueira 《Animal Science Journal》2015,86(5):553-556
Casein (CN) micelles are colloidal aggregates of protein dispersed in milk, the importance of which in the dairy industry is related to functionality and yield in dairy products. The objective of this work was to investigate the correlation of milk CN micelles diameter from Holstein and Zebu crossbreds with milk composition (protein, fat, lactose, total and nonfat solids and milk urea nitrogen), somatic cell count (SCC), age, lactation stage and production. Average casein micelles diameters of milk samples obtained from 200 cows were measured using photon correlation spectroscopy and multiple regression analysis was used to find relationship between variables. CN micelle diameter, SCC and nonfat solids were different between animals with different Holstein crossbreed ratios, which suggests influence of genetic factors, mammary gland health and milk composition. Overall, results indicate the potential use of CN micelle diameter as a tool to select animals to produce milk more suitable to cheese production. 相似文献
19.
Primo Anacláudia Alves Araújo Maria Diana Melo Silva Karla da Fonseca Silva Ludmyla Araújo Pereira Graziella de Andrade Carvalho Fernandes Francisco Éden Paiva Pompeu Roberto Cláudio Fernandes Franco Natale William de Souza Henrique Antunes 《Agroforestry Systems》2021,95(8):1459-1464
Agroforestry Systems - The use of native trees in agroecosystems is a promising way to increase litter deposition and nutrient cycling and foster the recovery of degraded areas, especially in... 相似文献
20.
An Erratum has been published for this article in Aquatic Conservation: Marine and Freshwater Ecosystems 12(2), 2002 577
- 1. This research extends techniques of predictive mapping from their application in terrestrial environments to marine landscapes by investigating the relationship between seagrass and hydrodynamics in Core Sound, North Carolina, USA.
- 2. An empirically derived logistic multiple regression model and a Boolean logic suitability model were used to produce several predictive map products, including: susceptibility of seagrasses to storms, probability of seagrass cover, and suitability of areas for restoration of seagrasses. A visual comparison between these maps and conventional seagrass polygon maps allows for a discussion of ‘field’ versus ‘object’ mapping, and the ramifications for management based on different cartographic techniques.
- 3. The predictive method used here showed that only a small portion (19%) of the seagrass bed in the study area would be expected to have a high probability of seagrass coverage. The majority of the seagrass habitat in the study area was predicted to have less than 50% probability of seagrass cover. In addition, 16% of the nearly 2000 ha of seagrass within the study area were predicted to be highly susceptible to acute storm events. Moreover, using a conservative set of site selection criteria, only 7% of the study area encompassed by seagrass habitat was predicted to have a high probability of successful restoration if injured.
- 4. This method provides for an inexpensive way to scale‐up from high‐resolution data to a coarser scale that is often required for conservation and management.