全文获取类型
收费全文 | 728篇 |
免费 | 12篇 |
学科分类
农业科学 | 740篇 |
出版年
2024年 | 17篇 |
2023年 | 12篇 |
2022年 | 5篇 |
2021年 | 15篇 |
2020年 | 8篇 |
2019年 | 18篇 |
2018年 | 17篇 |
2017年 | 27篇 |
2016年 | 24篇 |
2015年 | 12篇 |
2014年 | 14篇 |
2013年 | 25篇 |
2012年 | 46篇 |
2011年 | 43篇 |
2010年 | 27篇 |
2009年 | 28篇 |
2008年 | 51篇 |
2007年 | 43篇 |
2006年 | 22篇 |
2005年 | 26篇 |
2004年 | 26篇 |
2003年 | 31篇 |
2002年 | 24篇 |
2001年 | 8篇 |
2000年 | 7篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 10篇 |
1988年 | 4篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 6篇 |
1972年 | 3篇 |
1971年 | 3篇 |
1969年 | 6篇 |
1967年 | 4篇 |
1964年 | 3篇 |
排序方式: 共有740条查询结果,搜索用时 15 毫秒
61.
Genevieve Patrick Andrea M. Tarnecki Nicole Rhody Ryan Schloesser Kevan Main Roy Yanong Ruth Francis‐Floyd 《Aquaculture Research》2019,50(12):3793-3801
Almaco jack (Seriola rivoliana Valenciennes) is an excellent candidate for aquaculture due to its fast growth rate and high market value. While S. rivoliana have adapted well to captivity, survival at early life stages can be improved to increase profitability during production. A wide range of variables cause larval mortalities but high bacterial loads in rearing tanks are often correlated with these losses. The aim of this study was to investigate the effect of egg disinfection on bacterial load and hatch rate of S. rivoliana. Disinfectants tested included formalin (F100 and F200; 100 and 200 mg/L, respectively, for 60 min), hydrogen peroxide (HPO; 300 mg/L for 10 min) and peracetic acid/hydrogen peroxide (PAA/HPO; 15.7 mg/L/39.6 mg/L for 1 min). Concentrations and contact times were determined based on current use in marine aquaculture and preliminary trials. Eggs treated with HPO and F100 had significantly higher hatch rates than the untreated control group. All treatments significantly decreased total Vibrio counts compared to untreated eggs; however, total bacterial counts were only decreased following treatments with PAA/HPO and F200. To prevent egg mortality due to bacterial overgrowth, consideration should be given to the use of surface disinfection using HPO or F100. Future studies should investigate the use of peracetic‐based products at lower doses. 相似文献
62.
Edery P Marcaillou C Sahbatou M Labalme A Chastang J Touraine R Tubacher E Senni F Bober MB Nampoothiri S Jouk PS Steichen E Berland S Toutain A Wise CA Sanlaville D Rousseau F Clerget-Darpoux F Leutenegger AL 《Science (New York, N.Y.)》2011,332(6026):240-243
The spliceosome, a ribonucleoprotein complex that includes proteins and small nuclear RNAs (snRNAs), catalyzes RNA splicing through intron excision and exon ligation to produce mature messenger RNAs, which, in turn serve as templates for protein translation. We identified four point mutations in the U4atac snRNA component of the minor spliceosome in patients with brain and bone malformations and unexplained postnatal death [microcephalic osteodysplastic primordial dwarfism type 1 (MOPD 1) or Taybi-Linder syndrome (TALS); Mendelian Inheritance in Man ID no. 210710]. Expression of a subgroup of genes, possibly linked to the disease phenotype, and minor intron splicing were affected in cell lines derived from TALS patients. Our findings demonstrate a crucial role of the minor spliceosome component U4atac snRNA in early human development and postnatal survival. 相似文献
63.
This article outlines the principal gastrointestinal protozoal diseases that have been recorded as affecting reptiles. It covers 9 genera of flagellates/amoebae, 1 ciliate genus, and 5 genera of coccidia, describing their pertinent anatomy and what is known about their epidemiology, including clinical presenting signs and intestinal pathological changes. The agents are initially discussed individually and, to avoid repetition, common information about diagnostics, treatment, and control is then presented. 相似文献
64.
José L. Chávez Francis J. Pierce Todd V. Elliott Robert G. Evans Yunseop Kim William M. Iversen 《Precision Agriculture》2010,11(1):11-26
Precision irrigation systems can have inherent errors that affect the accuracy of variable water application rates controllers,
as well as affect the controllers’ performance when evaluated on different continuous move irrigation systems configurations.
The objective of this study was to assess the performance of a remote irrigation monitoring and control system (RIMCS) installed
on two separate linear move (LM) irrigation systems. The RIMCS varies water application rates by pulsing nozzles controlled
by solenoids connected via relays to a single board computer (SBC) with wireless Ethernet connection to a remote server. The
system also monitors irrigation system flow, pressure, position and wireless field sensor networks. The system was installed
on a LM irrigation system in Prosser, Washington, USA and on a LM in the Nesson Valley of North Dakota, USA. For the LM at
Prosser, four pre-defined irrigation patterns were imposed and variable rates were applied as a percentage of the nozzle base
application rate. Each nozzle was pulsed across the span length and along the LM travel direction. For the LM at the Nesson
Valley, a quadratic pattern was imposed pulsing banks of nozzles along the LM travel direction. Standard catch can tests were
performed and the system performance was evaluated by comparing measured catch can water depths with pre-determined target
values. The RIMCS accuracy was found to be in the range of the LM uniform water depth application uniformity coefficients
of 88–96%. The RIMCS was successfully transferred to another LM in North Dakota as indicated by the relatively low variable
rate application errors of –8.8 ± 8.1% and −0.14 ± 6.7% for the two spans. 相似文献
65.
S.?StamatiadisEmail author C.?Christofides C.?Tsadilas V.?Samaras J.?S.?Schepers D.?Francis 《Precision Agriculture》2005,6(4):399-411
Bare soil reflectance from airborne imagery or laboratory spectrometers has been used to infer soil properties such as soil texture, organic matter, water content, salinity and crop residue cover. However, the relation of soil properties to reflectance data often varies with soil type and conditions and surface reflectance may not be representative of the conditions in the root zone. The objectives of this study were to assess the soil reflectance data obtained by ground-based sensors and to model soil properties in the root zone as a function of surface soil reflectance and plant response. Ground-based sensors were used to simultaneously monitor soil and canopy reflectance in the visible and near-infrared (VNIR) along six rows and in two growth stages in a 7 ha cotton field. The reflectance data were compared to soil properties, leaf nutrients and biomass measured at 33 sampling positions along the rows. Brightness values of the blue and green bands of soil reflectance were better correlated to soil water content, particulate organic matter and extractable potassium and phosphorus, while those in the red and NIR bands were correlated to soil carbonate content, total nitrogen, electrical conductivity and foliar nutrients. The correlation of red soil reflectance with canopy reflectance was significant and indicated an indirect inverse relationship between soil fertility and plant stress. The integration of surface soil reflectance and plant response variables in a multiple regression model did not substantially improve the prediction of soil properties in the root zone. However, crop nutrient status explained a significant portion of the spatial variability of soil properties related to nitrification processes when soil reflectance did not. The implication of these findings to agricultural management is discussed. 相似文献
66.
Loss of genetic diversity due to fishing pressure 总被引:1,自引:0,他引:1
Loss of genetic diversity in the orange roughy, Hoplostethus atlanticus, caught off New Zealand, was measured by gel electrophoresis of nine polymorphic enzyme loci. There has been a significant reduction in genetic diversity on three spawning sites over the past 6 years, during which time the virgin biomass has been reduced by 70%. It is suggested that fishing activities which concentrate on spawning populations differentially remove the older and more heterozygous individuals from the virgin stock. Commercial fishing activities may have had significant genetic effects on fish stocks without reducing them to near-extinction levels. 相似文献
67.
Epidemiological features of clinical mastitis in dry cows from a three year prospective study are described. Two hundred and seventy-three herds in England and Wales participated in the first year (1980) and 209 and 159 of them continued in the study in the subsequent two years. Clinical mastitis was recorded in 1.5 per cent of cows during the dry period in each of the three years. These cases represented between 3.6 and 4.2 per cent of samples from all clinical cases examined. The incidence of clinical mastitis in dry cows increased during the winter housing period (October to March), a peak occurring at the end of this period. A secondary peak in incidence was recorded in August. Streptococcus uberis was the predominant pathogen. Variations in the monthly incidences of cases associated with the major mastitis pathogens were observed. A greater proportion of cases which occurred during the dry period exhibited systemic signs than of cases which occurred during lactation, with the exception of cases associated with Escherichia coli. The risk of clinical mastitis was apparently higher during the last 30 days of the dry period than during the earlier stages of the dry period. 相似文献
68.
69.
Wakshlag JJ Cooper BJ Wakshlag RR Kallfelz FA Barr SC Nydam DV Dimauro S 《American journal of veterinary research》2004,65(4):480-484
OBJECTIVE: To perform respiratory chain enzymatic activity assays on canine skeletal muscle biopsy specimens and establish reference range values of skeletal muscle enzyme activities for dogs. SAMPLE POPULATION: Biopsy specimens from the vastus lateralis muscle were obtained from 24 dogs (8 sexually intact males and 14 sexually intact females) ranging from 15 months to 6 years of age. PROCEDURE: Mean values of citrate synthase, cytochrome-c oxidase, succinate dehydrogenase, succinate dehydrogenase-cytochrome-c reductase, nicotinamide adenine dinucleotide (NADH) dehydrogenase, and NADH dehydrogenase-cytochrome-c reductase activities were established by use of 6 standard spectrophotometric assays for respiratory chain enzyme analysis. RESULTS: Compared with published data for skeletal muscle enzyme activities in humans, skeletal muscle enzyme activities in dogs were 2- to 4-fold higher. Additionally, citrate synthase activity, a marker for mitochondrial volume, was positively correlated with age in dogs, suggesting that mitochondrial volume increases with age, although no apparent change in respiratory chain enzymatic activity with an increase in age was found. CONCLUSIONS AND CLINICAL RELEVANCE: Reference range values for skeletal muscle enzyme activities of dogs are needed to accurately interpret results of respiratory chain enzymatic activity assays. During investigation of metabolic myopathies, if skeletal muscle biopsy specimens are evaluated for respiratory chain enzyme kinetics, they should be performed and evaluated in concert with skeletal muscle biopsy specimens from clinically normal animals of the same species. 相似文献
70.
Jason Spendelow;Clare Cripwell;Rebecca Stott;Kathryn Francis;Jenny Powell;Kate Cavanagh;Ruth Corbett; 《Veterinary Medicine and Science》2024,10(4):e1547
Veterinary professionals experience higher psychological distress and lower wellbeing compared with the general population. Identifying workplace stressors is key to understanding and alleviating these difficulties. 相似文献