全文获取类型
收费全文 | 272篇 |
免费 | 16篇 |
专业分类
林业 | 24篇 |
农学 | 4篇 |
基础科学 | 2篇 |
57篇 | |
综合类 | 44篇 |
农作物 | 11篇 |
水产渔业 | 23篇 |
畜牧兽医 | 80篇 |
园艺 | 8篇 |
植物保护 | 35篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 5篇 |
2019年 | 11篇 |
2018年 | 6篇 |
2017年 | 6篇 |
2016年 | 7篇 |
2015年 | 5篇 |
2014年 | 3篇 |
2013年 | 8篇 |
2012年 | 17篇 |
2011年 | 26篇 |
2010年 | 13篇 |
2009年 | 14篇 |
2008年 | 13篇 |
2007年 | 18篇 |
2006年 | 17篇 |
2005年 | 18篇 |
2004年 | 16篇 |
2003年 | 12篇 |
2002年 | 18篇 |
2001年 | 1篇 |
2000年 | 3篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1957年 | 1篇 |
1944年 | 1篇 |
1941年 | 1篇 |
排序方式: 共有288条查询结果,搜索用时 250 毫秒
61.
Laurence E. D. SMITH 《农业科学与工程前沿(英文版)》2020,7(1):90-97
Farmers are the key agents who manage land and water. Agriculture Green Development (AGD) requires a transformation in farming from high resource consumption and environmental cost to sustainable intensification with high productivity, high resource use efficiency and low environmental risk. This paper analyzes the public policy challenge of AGD and makes the case for a location-sensitive policy mix made up of regulation, advice provision, voluntarism and targeted incentives. The public agricultural extension service in China is a key resource, but one that requires reorientation and reform with the aim of better balancing high farm productivity with environmental protection. 相似文献
62.
Paul C. Cleland F. Chris Baldock Pornchai Chamnanpood Laurence J. Gleeson 《Preventive veterinary medicine》1996,26(3-4):253-261
A study was undertaken in northern Thailand to identify factors which put some villages at higher risk of foot-and-mouth disease (FMD) outbreaks than others. The number of FMD outbreaks experienced in the previous 5 years and data on 145 putative risk factors were obtained by interview from 60 villages during 1991–1992. Univariable analyses identified 27 factors for further investigation using logistic regression. When villages were classified into three FMD frequency groups of zero to one, two to three or four or more outbreaks in the last 5 years, the important factors explaining the differences in risk were the total number of cattle and buffaloes purchased in the previous year, the number of neighbouring villages which shared a common water source and whether agriculture was the most important source of cash income for the village. These factors were also the most important variables in explaining the difference in risk when comparing villages with zero or one outbreak with those having four or more. We concluded that the greatest impact on reducing spread of FMD among villages would be obtained through the development of strategies to reduce the likelihood of introduction through livestock purchases and for villagers to take greater care when livestock are grazed with those from neighbouring villages and when sharing common water supplies. 相似文献
63.
Valentin Janvier Laurence Evrard Simona Cerri Alexandra Gougnard Valeria Busoni 《Veterinary radiology & ultrasound》2016,57(1):65-74
Ultrasonography and radiography are commonly used for staging of lymphoma in horses, however there is little published information on imaging characteristics for horses with confirmed disease. The purpose of this retrospective, case series study was to describe ultrasonographic and radiographic findings for a group of horses with a confirmed diagnosis of lymphoma. A total of 13 horses were sampled. Lymphadenopathy (8/13), peritoneal effusion (6/13), splenic (6/13), and hepatic (5/13) lesions were the most frequently identified. The predominant splenic and hepatic ultrasonographic lesions were hypoechoic nodules, organomegaly, and changes in echogenicity. Digestive tract lesions were detected in three horses and these included focal thickening and decreased echogenicity of the small (2/13) and large intestinal (2/13) wall. Thoracic lesions were predominantly pleural effusion (4/13), lymphadenopathy (4/13), and lung parenchymal changes (3/13). Enlarged lymph nodes were detected radiographically (4/13) and/or ultrasonographically (2/13) in the thorax and ultrasonographically in the abdomen (7/13) and in the caudal cervical region (4/13). Findings supported the use of abdominal and thoracic ultrasonography for lymphoma staging in horses. Ultrasound landmarks for localizing cecal and caudal deep cervical lymph nodes were also provided. 相似文献
64.
Detection and seroprevalence of morbillivirus and other paramyxoviruses in geriatric cats with and without evidence of azotemic chronic kidney disease 下载免费PDF全文
65.
Jonathan N. King Mike Martin Valrie Chetboul Luca Ferasin Anne T. French Günther Strehlau Wolfgang Seewald Sarah G. W. Smith Simon T. Swift Susan L. Roberts Andrea M. Harvey Christopher J. L. Little Sarah M. A. Caney Kerry E. Simpson Andrew H. Sparkes Eleanor J. Mardell Eric Bomassi Claude Muller John P. Sauvage Armelle Diqulou Matthias A. Schneider Laurence J. Brown David D. Clarke Jean‐Francois Rousselot 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2019,33(6):2559-2571
66.
Nondestructive estimation of wood chemical composition of sections of radial wood strips by diffuse reflectance near infrared spectroscopy 总被引:2,自引:1,他引:2
P. David Jones Laurence R. Schimleck Gary F. Peter Richard F. Daniels Alexander Clark III 《Wood Science and Technology》2006,40(8):709-720
The use of calibrated near infrared (NIR) spectroscopy for predicting the chemical composition of Pinus taeda L. (loblolly pine) wood samples is investigated. Seventeen P. taeda radial strips, representing seven different sites were selected and NIR spectra were obtained from the radial longitudinal face of each strip. The spectra were obtained in 12.5 mm sections from pre-determined positions that represented juvenile wood (close to pith), transition wood (zone between juvenile and mature wood), and mature wood (close to bark). For these sections, cellulose, hemicellulose, lignin (acid soluble and insoluble), arabinan, galactan, glucan, mannan, and xylan contents were determined by standard analytical chemistry methods. Calibrations were developed for each chemical constituent using the NIR spectra, wood chemistry data and partial least squares (PLS) regression. Relationships were variable with the best results being obtained for cellulose, glucan, xylan, mannan, and lignin. Prediction errors were high and may be a consequence of the diverse origins of the samples in the test set. Further research with a larger number of samples is required to determine if prediction errors can be reduced. 相似文献
67.
Red spruce (Picea rubens Sarg.) trees growing at high elevation in the northeastern United States have experienced decline in recent years but seedlings have proved to be relatively tolerant of a wide range of environmental stresses in controlled studies. One possible reason for the wide tolerance to stress in seedlings is their inherently large pool of carbohydrate reserves, which is available for maintenance during and regrowth after periods of stress. We tested for the effects of foliar N and exposure to ozone on foliar carbohydrate reserves of 20-year-old naturally regenerated saplings. The trees were maintained in native soil in 360-l containers for 5 years before the experiment. The year before the experiment, trees were fertilized with N,P,K to provide a population of trees from N deficient to N sufficient. As foliar N decreased below 0.9%, length of current-year shoots and specific needle area of current-year needles declined. Foliar N concentration was correlated with foliar sugar and starch concentrations, but relationships varied with time of year. Before bud break, foliar carbohydrates and N, in general, were positively correlated, and date of bud break was delayed in N-deficient trees. During active growth, foliar soluble sugars and N were positively correlated, but starch concentrations were negatively correlated with N. By late September, neither starch nor sugar concentration was correlated with N concentration. Ozone and foliar N concentrations did not interact to change foliar carbohydrate concentrations or shoot and needle growth in this relatively short-term study. 相似文献
68.
BACKGROUND: Increased rates of overweight/obesity have been reported in recent years in developed countries. This population study of healthy subjects evaluated the changes in overweight/obesity prevalence in 2003, compared with 1993, and determined the association of age, sex and leisure-time activity with body mass index (BMI), fat-free mass index (FFMI) and fat mass index (FMI). DESIGN: Two transversal samples of convenience. PARTICIPANTS: Healthy volunteers (1993, n = 802; 2003, n = 1631). METHODS: Fat-free mass was determined using the bioelectrical impedance multiple regression equation. Multivariable linear regression, including confounding variables (age, sex, leisure-time activity), was used to model the body composition evolution between the 1993 and the 2003 subjects. RESULTS: BMI and FMI were higher in 2003 than in 1993, P < 0.001. FFMI was not higher in 2003 than in 1993, P = 0.38. More subjects were overweight/obese in 2003 than in 1993 (27.5 versus 17.2%, chi-square P < 0.001), and had a high FFMI (30.2 versus 21.8%, chi-square P < 0.001) and high FMI (28.0 versus 20.3%, chi-square P < 0.001). Multivariate linear regressions showed that leisure-time activity was negatively, and sex, age and inclusion year were positively associated with BMI, FFMI and FMI (the exception was a negative association with sex) (P < 0.001). CONCLUSION: Overweight prevalence increased between 1993 and 2003 in a Swiss city, and was associated with a higher fat mass. This observation remained statistically significant after adjustment for age, sex and leisure-time activity. 相似文献
69.
Martínez-Alvarez O Guimas L Delannoy C Fouchereau-Peron M 《Journal of agricultural and food chemistry》2007,55(14):5469-5475
Fish protein hydrolysates (FPH) may have potential as bioactive components in functional foods as nutraceuticals. This study focused on the identification of calcitonin gene-related peptide (CGRP) molecules in FPH. CGRP is a neuropeptide belonging to the calcitonin/CGRP family and is known as potent arterial and venous vasodilator in humans. Hydrolysates of industrial origin were prepared from siki (Centroscymnus coelolepsis) heads and were analyzed for the presence of CGRP-like molecules using specific radioimmunoassays and radioreceptorassays. The biological activity of the CGRP-related molecules was assessed by their ability to stimulate the adenylate cyclase activity in rat liver membranes. They were finally purified using gel exclusion chromatography and high-performance liquid chromatography (HPLC). These molecules presented a molecular weight around 1500-2500 Da and were obtained with a purification factor of 79. The incorporation of FPH with CGRP-like molecules in functional foods could lead to the development of new useful products for health and nutrition markets. 相似文献
70.
Laurence Vaissayre Morgane Ardisson Christiane Borries Sylvain Santoni Jacques David Pierre Roumet 《Euphytica》2012,185(1):61-75
Genetic maps published for elite durum wheat (Triticum turgidum durum Desf.), were mainly related to Italian and North American pools. To provide additional information dedicated to durum elite pool,
a recombinant inbred population (217 RILs) derived form 2 French commercial varieties (Ixos and Primadur), has been mapped
with 529 loci (98 AFLPs, 67 SSRs, 1 ISBP and 363 DArTs). Genetic map spanned a total of 2,082 cM (5.7 cM/marker on average).
Recombination rate variation over the genome was documented through the analysis of six segregating populations representing
a total of 48 RILs × 6, issued from an half diallel design based on four elite lines—Neodur, Ixos, Lloyd and Primadur—including
the 2 previous genitors. Each set of three genetically connected populations (48 RILs × 3) was used to build the consensus
parental maps for each genitor. To construct the four consensus parental maps, marker ordering was determined on 217 RILs
map which was an extended population of the most polymorphic cross (Ixos × Primadur). Sizeable, recombination rate variation
has been observed between the four parental maps both at the marker pair scale and at the linkage group scale. Two of the
parents, Lloyd and Primadur, had strong, opposite effects increasing and decreasing, respectively the recombination rate.
Additional studies are proposed to increase our understanding of this variation, with the identification of environmental
or genetic factors affecting recombination rate. 相似文献