全文获取类型
收费全文 | 810篇 |
免费 | 115篇 |
国内免费 | 1篇 |
专业分类
林业 | 55篇 |
农学 | 41篇 |
基础科学 | 10篇 |
112篇 | |
综合类 | 67篇 |
农作物 | 33篇 |
水产渔业 | 83篇 |
畜牧兽医 | 482篇 |
园艺 | 8篇 |
植物保护 | 35篇 |
出版年
2023年 | 8篇 |
2022年 | 15篇 |
2021年 | 28篇 |
2020年 | 21篇 |
2019年 | 37篇 |
2018年 | 44篇 |
2017年 | 34篇 |
2016年 | 27篇 |
2015年 | 31篇 |
2014年 | 41篇 |
2013年 | 54篇 |
2012年 | 43篇 |
2011年 | 48篇 |
2010年 | 38篇 |
2009年 | 25篇 |
2008年 | 35篇 |
2007年 | 24篇 |
2006年 | 29篇 |
2005年 | 31篇 |
2004年 | 20篇 |
2003年 | 18篇 |
2002年 | 18篇 |
2001年 | 19篇 |
2000年 | 22篇 |
1999年 | 20篇 |
1998年 | 17篇 |
1997年 | 11篇 |
1996年 | 9篇 |
1995年 | 12篇 |
1994年 | 9篇 |
1993年 | 4篇 |
1992年 | 10篇 |
1991年 | 6篇 |
1990年 | 8篇 |
1989年 | 10篇 |
1988年 | 6篇 |
1987年 | 11篇 |
1986年 | 8篇 |
1985年 | 11篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1980年 | 5篇 |
1979年 | 7篇 |
1977年 | 4篇 |
1975年 | 8篇 |
1974年 | 8篇 |
1973年 | 4篇 |
1972年 | 3篇 |
1970年 | 2篇 |
1968年 | 5篇 |
排序方式: 共有926条查询结果,搜索用时 15 毫秒
151.
152.
Adam M. Strom DVM MS Tanya C. Garcia MS Karl Jandrey DVM MAS Diplomate ACVECC Michael L. Huber DVM MS Diplomate ACVS Susan M. Stover DVM PhD Diplomate ACVS 《Veterinary surgery : VS》2010,39(7):824-828
Objective: To compare the bending structural stiffness and bending strength of thick and thin 2.4 mm limited contact dynamic compression plates (2.4 LC‐DCP), 2.0 mm LC‐DCP (2.0 LC‐DCP), and 2.0 dynamic compression plates (2.0 DCP). Study Design: In vitro mechanical study. Methods: Two thicknesses of 2.4 LC‐DCP, 2.0 LC‐DCP, and 2.0 DCP stainless‐steel plates were tested in 4‐point bending. Data were collected during bending until implants plastically deformed. Bending structural stiffness and bending strength were determined from load displacement curves. Mechanical properties were compared between plates and the effects of plate type, size, and thickness on stiffness and strength were assessed using ANOVA. Results: The thick 2.4 LC‐DCP implant was the stiffest and strongest; the thin 2.0 DCP implant was most compliant and weakest. Larger sized plates, thicker plates, and limited contact design of plates enhanced stiffness and strength. For the plates studied, plate size had a larger effect than plate type or thickness on stiffness and strength. Conclusion: Increasing the size (width) and thickness of plates increases both the bending structural stiffness and strength. For the plates studied, LC‐DCP implants were stiffer and stronger than DCP implants. Clinical Relevance: Plate bending structural stiffness and strength can be most effectively enhanced by using a larger sized plate, but gains can also be achieved by using a thicker plate and/or an LC‐DCP instead of a DCP implant when possible. 相似文献
153.
Agroforestry systems have been recognized as areas with high conservation potential, and there is a need to quickly assess
the biodiversity and tree stocking density available in these systems. However, it is not clear if the commonly used fixed
area plot is most efficient for sampling such landscapes, or if a different method could provide equivalent data with less
effort. Thus, a field and simulation-based study was carried out to compare the efficiency and accuracy of a variable area
transect versus the fixed area square plot. Field efficiency tests were carried out in three habitat types, robusta coffee
plantations, arabica coffee plantations and a privately owned forest fragment, in Kodagu, southern India. A simulation study
of bias, precision and accuracy of the two methods for tree density estimation also was carried out using various spatial
distribution patterns and densities. The variable area transect was significantly more efficient per unit effort in the field
than the fixed area square plot. In the simulation tests both methods performed equally well under random spatial distribution.
However, under simulated aggregated distribution both methods were positively biased (square plot up to 12% at low density,
variable area transect 9–12% at all densities), and under simulated regular distribution the variable area transect was slightly
negatively biased (−5 to −7% at medium to high density). The variable area transect thus can be recommended over the square
plot for rapid assessment of tree diversity and density, when the vegetation is expected to be randomly dispersed. 相似文献
154.
Ostreid herpesvirus 1 detection and relationship with Crassostrea gigas spat mortality in France between 1998 and 2006 总被引:1,自引:0,他引:1
Garcia C Thébault A Dégremont L Arzul I Miossec L Robert M Chollet B François C Joly JP Ferrand S Kerdudou N Renault T 《Veterinary research》2011,42(1):73
ABSTRACT: Since its molecular characterisation, Ostreid herpesvirus 1 (OsHV-1) has been regularly detected in Crassostrea gigas in France. Although its pathogenicity was demonstrated on larval stages, its involvement during mortality outbreaks at the juvenile stage was highly suspected but not evidenced. To investigate mortality outbreaks, the French National Network for Surveillance and Monitoring of Mollusc Health (REPAMO) carried out two surveys in juvenile C. gigas. The first survey lasted from 1998 to 2006 and was an epidemiological inquiry occurring when oyster farmers reported mortality outbreaks. The second survey, a longitudinal one, was set up in 1998 to complete the network observations on OsHV-1. Data analysis showed a specific pattern of mortality outbreaks associated with OsHV-1 detection. Ostreid herpesvirus 1 detection mainly appeared during the summer, suggesting the influence of the seawater temperature on its occurrence. It mostly presented a patchy distribution in the field in contrast to the nursery. Significant relationship between OsHV-1 detection and spat mortality was found, preferentially in sheltered and closed environments. The longitudinal survey confirmed most of the network observations. Although subsequent works particularly epidemiological surveys would be useful to confirm the causal link between the detection of OsHV-1 and the mortality outbreaks in juvenile C. gigas, the role of OsHV-1 in oyster mortality is progressing. 相似文献
155.
Garcia DA Froes TR Vilani RG Guérios SD Obladen A 《The Journal of small animal practice》2011,52(9):484-490
Objectives : To assess the accuracy of intestinal ultrasound for diagnosis of intestinal obstruction in dogs and cats. Methods : A prospective clinical study was performed. Inclusion criteria were dogs and cats with clinical signs suggestive of gastrointestinal obstruction. Animals with no obstruction detected on ultrasound were excluded if they could not be monitored for 48 hours to confirm absence of obstruction. Sonographic diagnosis of small intestinal obstruction was based on identification of at least two findings suggestive of intestinal obstruction. Results : Ninety‐two patients suspected of having intestinal obstruction were included. Correct diagnosis of intestinal obstruction was made in 21 cases (23%), and in 68 (74%) this diagnosis was excluded. Interpretation of the images on prospective analysis had sensitivity, positive predictive, specificity and negative predictive values of 100%, 87.5%, 95.8% and 100%, respectively. Clinical Significance : Ultrasonography is an excellent method for investigation of animals with gastrointestinal disorders, and is particularly useful for excluding obstructive processes. 相似文献
156.
Can the protozoan parasite Bonamia ostreae infect larvae of flat oysters Ostrea edulis? 总被引:1,自引:0,他引:1
Arzul I Langlade A Chollet B Robert M Ferrand S Omnes E Lerond S Couraleau Y Joly JP François C Garcia C 《Veterinary parasitology》2011,179(1-3):69-76
Bonamia ostreae is an intracellular protistan parasite affecting flat oysters Ostrea edulis. It can be detected in juveniles but mortalities mainly affect oysters which are more than 2 years old. The parasite is usually observed inside haemocytes and sometimes free, notably in gill epithelia suggesting a parasite release through this organ. However, the infective form and ways of entry and release remain undetermined. Flat oysters incubate their larvae in their pallial cavity for 8-10 days before releasing them into the water column. Flat oysters in Bay of Quiberon in South Brittany (France) are known to be infected with B. ostreae since 1979 and is the most important area in France for O. edulis spat collection. Flat oysters incubating larvae were sampled in this area during summertime between 2007 and 2009. Both adults and larvae were preserved and assayed by PCR and in situ hybridisation (ISH). PCR tests revealed the presence of parasite DNA in some adults and larvae. Specific labelling could be detected by ISH in gills, digestive system, gonad and mantle in adults and in the epithelium surrounding the visceral cavity of some larvae. Our results demonstrate that larvae can be infected with B. ostreae. Larvae might thus contribute to the spread of the parasite during their planktonic life. In addition, their transfer for aquaculture purpose should be controlled especially when they are exported from infected zones. 相似文献
157.
Ruiz Maria Luiza Owatari Marco Shizuo Yamashita Marcela Maya Ferrarezi José Victor Saffadi Garcia Patricia Cardoso Lucas Martins Maurício Laterça Mouriño José Luiz Pedreira 《Tropical animal health and production》2020,52(1):167-176
Tropical Animal Health and Production - The aims of this study were to evaluate the inclusion of different concentrations of Lactobacillus plantarum in Nile tilapia diet and to verify histological... 相似文献
158.
The effect of potassium (K)‐calcium (Ca) ratios on the cation nutrition of Vitis vinifera L. cv. Négrette was investigated on grafted vines grown hydroponically to gain a deeper insight into the origin of the lack of acidity of some wines. Four nutrient solutions were investigated for long duration experiments: a balanced K‐Ca nutrient solution (K=3.9 meq L‐1 ; Ca=4.8 meq L‐1) used as a reference, a low K (K=0.3 meq L‐1; Ca=8.4 meq L‐1) and a high K (K=7.1 meq L‐1; Ca=1.6 meq L‐1) nutrient solutions. Besides, the reference nutrient solution was enriched with Ca (K=3.9 meq L‐1; Ca=13.8 meq L‐1) so as to simulate the possible effects of liming. The experiments showed that, in spite of low K requirements, the high K storage capacity of cultivar Négrette might account for the low acidity of the wines. However, a strong Ca‐K antagonism was characterized: the Ca enrichment of the reference nutrient solution resulted in a 30% decrease in the K concentration of leaf blades and petioles. Liming can thus limit K uptake by the plant and contribute to increased acidity of the wines issued from cultivars grown in acid soils. 相似文献
159.
Efficient plant protection is of fundamental importance in order to warrant food security. Here, we present arguments that a coordinate approach in plant protection is urgently required, taking advantage of a broad mix of measures, including modern synthetic chemistries, capable of protecting plants from adverse organisms.
相似文献160.
Ribeiro MG Takai S Guazzelli A Lara GH da Silva AV Fernandes MC Condas LA Siqueira AK Salerno T 《Research in veterinary science》2011,91(3):478-481
The virulence genes and plasmid profiles of 23 Rhodococcus equi isolates from 258 lymph nodes from domestic pigs (129 nodes with lesions and 129 without lesions) and 120 lymph nodes from slaughtered wild boars (60 nodes with lesions and 60 without) were characterized. R. equi was obtained from 19 lymph nodes of domestic pigs, 17 with, and two without lesions, and from four lymph nodes with lesions, from wild boars. The 23 isolates were tested for the presence of vapA and vapB genes, responsible for the 15–17 and 20 kDa virulence-associated proteins, respectively, by PCR in order to characterize as virulent (VapA), intermediately virulent (VapB) and avirulent. Plasmid DNAs were isolated and analyzed by digestion with restriction endonucleases to estimate size and compare their polymorphisms. Of the 19 domestic pigs strains, seven (36.8%) were avirulent and 12 (63.2%) were intermediately virulent, with the intermediately virulent isolates being plasmid types 8 (8 isolates), 10 (2 isolates), 1 (1 isolate) and 29 (1 isolate). The plasmid type of four strains isolated from wild boars was also intermediately virulent type 8. None of the domestic pigs and wild boar isolates showed the vapA gene. These findings demonstrate a high occurrence of plasmid type 8 in isolates from pigs and wild boars, and the similarity of plasmid types in the domestic pigs, wild boars and human isolates in Brazil. 相似文献