全文获取类型
收费全文 | 354篇 |
免费 | 18篇 |
专业分类
林业 | 8篇 |
农学 | 84篇 |
基础科学 | 1篇 |
30篇 | |
综合类 | 11篇 |
农作物 | 19篇 |
水产渔业 | 3篇 |
畜牧兽医 | 191篇 |
园艺 | 8篇 |
植物保护 | 17篇 |
出版年
2022年 | 2篇 |
2021年 | 2篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2018年 | 12篇 |
2017年 | 9篇 |
2016年 | 12篇 |
2015年 | 9篇 |
2014年 | 9篇 |
2013年 | 38篇 |
2012年 | 19篇 |
2011年 | 16篇 |
2010年 | 13篇 |
2009年 | 8篇 |
2008年 | 9篇 |
2007年 | 10篇 |
2006年 | 5篇 |
2005年 | 7篇 |
2004年 | 5篇 |
2003年 | 5篇 |
2002年 | 6篇 |
2001年 | 9篇 |
2000年 | 14篇 |
1999年 | 10篇 |
1998年 | 5篇 |
1997年 | 10篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 11篇 |
1991年 | 11篇 |
1990年 | 8篇 |
1989年 | 7篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1970年 | 3篇 |
1967年 | 2篇 |
1936年 | 1篇 |
1915年 | 1篇 |
排序方式: 共有372条查询结果,搜索用时 15 毫秒
81.
82.
Investigations were conducted on several small neighbouring beef cattle and sheep farms that were found to be contaminated with polychlorinated biphenyls (PCBs). The residues detected contained about 62% w/w chlorine and soil concentrations ranged from 0.35 to 1.9 mg/kg. Beef cattle and sheep grazing the contaminated land had PCB concentrations in their fat of 0.3 to 1.7 mg/kg and 0.19 to 0.45 mg/kg, respectively. The concentration of PCBs in the caudal fat of cattle was 0.3 to 2 times the concentration of PCBs in the land they were grazing and was positively related to stocking rates. PCBs were present in milk fat from cattle at about the same concentration as in caudal fat, and lactation appeared to contribute to decontamination. Wool grease from sheep contained about 1 to 2 times the concentration of PCBs in subcutaneous fat. Calves of contaminated cows also became contaminated. The half-life for decontamination of PCBs in a group of 8 young female beef cattle was calculated at 13 months. PCBs were detected in pasture samples at concentrations ranging from less than 0.01 mg/kg to 0.12 mg/kg. However, PCBs were not detected in any sample of hay cut from these paddocks. In 4 sheep fed a sole ration of this hay, traces of PCBs were detected in their fat following 89 days of feeding. Grazing livestock for meat production on land contaminated with PCBs is not recommended because livestock readily acquire residues, and PCBs persist in soil and livestock for long periods. Grazing sheep for wool production on land contaminated with PCBs may be an option. 相似文献
83.
84.
85.
Acute echocardiographic effects of sotalol on ventricular systolic function in dogs with ventricular arrhythmias
下载免费PDF全文
![点击此处可从《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》网站下载免费的PDF全文](/ch/ext_images/free.gif)
86.
Molecular cloning and expression of FGF2 gene in pre‐implantation developmental stages of in vitro‐produced sheep embryos
下载免费PDF全文
![点击此处可从《Reproduction in domestic animals》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Early embryonic mortality is one of the main sources of reproductive loss in domestic ruminants including sheep. Fibroblast growth factor‐2 (FGF‐2) is a member of FGFs family that mediates trophoblast activities and regulates embryonic development in various species. In this study, we have cloned, characterized sheep FGF2 cDNA (KU316368) and studied the expression in sheep embryos. Ovaries of non‐pregnant sheep were collected from local abattoir and matured in culture medium at 38.5ºC, 5% CO2, 95% humidity for 22–24 hr. The matured oocytes were inseminated with capacitated spermatozoa in Brackett and Oliphant medium and resulted embryos were cultured in CO2 incubator for 6–7 days to complete the developmental stages from two cells to blastocyst stage. Total RNA was extracted from immature oocytes (n = 100), mature oocytes (n = 100) and different stages of embryos such as 2 cell (n = 50), 4 cell (n = 25), 8 cell (n = 12), 16 cell (n = 6), morula (n = 5) and blastocyst (n = 3). The total RNA isolated from the oocytes and embryos was reverse transcribed and subjected to real‐time polymerase chain reaction using sequence‐specific primers and SYBR green as the DNA dye. On sequence analysis, the nucleotide sequence of sheep FGF2 exhibited highest sequence similarity with cattle (100%) and least with rat and mouse (69.2%). At the deduced amino acid level, a highest degree of similarity was noticed with cattle, buffalo, goat, pig, camel and horse (100%) and lowest degree of identity with rat, human and mouse (98.2%). The FGF2 mRNA expression was higher in immature and mature oocytes and gradually decreases from 2‐cell stage of embryo to the blastocyst stage. More over a significant differences in FGF2 mRNA expression (p < .05) were observed between immature oocytes and all pre‐implantation stages of embryo. It can be concluded that FGF‐2 plays a significant role in pre‐implantation and early development of embryos in sheep. 相似文献
87.
Catherine Belanger Catherine T. Gunther-Harrington Satoko Nishimura Maureen S. Oldach Samantha L. Fousse Lance C. Visser Joshua A. Stern 《Journal of Veterinary Cardiology》2018,20(2):115-122
Objectives
We aimed to evaluate safety and efficacy of high-pressure balloon valvuloplasty (HPBVP) for treatment of canine severe pulmonary valve stenosis (PS). A secondary aim was to provide pre-procedure predictors of success.Animals
Twenty-five dogs.Methods
Prospective observational study. Dogs with severe PS (echocardiographically derived trans-pulmonary peak/maximum pressure gradient (EDPG) ≥80 mmHg) were recruited. All dogs underwent echocardiography before and 20–24hrs after HPBVP using a high-pressure balloon with rated burst pressures ranging from 12 to 18 ATM. Procedural success was defined as a post-HPBVP EDPG reduction of ≥50% or reduction into at least the moderate category of PS (50–79 mmHg). Optimal result was defined as a post-procedural EDPG ≤30 mmHg.Results
Initial median (IQR) EDPG for all dogs was 96 (88, 127) mmHg with a post-operative median of 48 (36, 65) mmHg. The median EDPG reduction provided by HPBVP was 63% (39, 68); procedural success rate was 92% (23 dogs). Optimal results were achieved in 56% (14 dogs). There were no significant correlations between EDPG reduction and valve morphology (Type A and Type B) or severity of right ventricular hypertrophy. Pulmonary valve annulus diameter was the only echocardiographic variable that was significantly correlated to EDPG reduction (p = 0.02; r = ?0.46). No dog experienced any anesthetic or surgical complications, and all patients survived the procedure.Conclusions
In this cohort of 25 dogs with severe PS, HPBVP was safe and effective. The procedural success rate and high number of optimal results achieved with HPBVP suggest future randomized controlled trials comparing HPBVP to conventional valvuloplasty are warranted. 相似文献88.
Reason for performing study: The role of matrix metalloproteases (MMPs) and the timeline of proteolysis during laminitis development are incompletely understood. Objectives: To determine the temporal progression of selected MMPs and protease regulators during laminitis development. Methods: Five clinically normal Standardbred horses received, via nasogastric intubation, an oligofructose (OF) bolus (10 g/kg bwt). Laminitis induction proceeded for 48 h followed by euthanasia. Lamellar biopsies were obtained prior to dosing and at intervals during the treatment period for analysis (12, 18, 24, 30 and 36 h and at 48 h following euthanasia). Tissue samples were analysed by real‐time PCR, zymography and western blotting. Results: Activation of proMMP‐2 occurs either simultaneously or at least 12 h following lamellar basement membrane (BM) damage, while no activation of proMMP‐9 is seen during OF laminitis induction. Aggrecanase gene expression increased initially at 12–18 h post OF dosing, similar to BM changes. Gene expression of TIMP‐2, a MMP regulator, decreases during laminitis development. Conclusions: The MMP‐2/MT1‐MMP complex may not play a major role in initiating lamellar BM damage. Aggrecanase and TIMP‐2 gene expression appear related to BM lamellar changes. Potential relevance: MMPs, historically thought to cause laminitis, do not appear to play an initiating role in the lamellar lesion. Other host derived proteases and degradation of alternative lamellar matrix components need to be considered. 相似文献
89.
MJ Lancaster JS Nimmo C Lenghaus IJ Gill RD Crawford RT Badman JL Samuel CJ Werner C Button N Kvalheim 《Australian veterinary journal》2009,87(12):476-479
Objective To document an ovine disease attributed to the consumption of Lythrum hyssopifolia (lesser loosestrife). Procedures Historical and histological review of field and experimental cases. Results 1–20% mortality occurred in sheep flocks grazing paddocks where L. hyssopifolia was the predominant green vegetation. Well‐documented disease outbreaks occurred in summer on nine farms across Victoria between 1974 and 2002. Liver damage occurred in all nine outbreaks, with kidney damage in at least eight. Hepatocyte necrosis was usually zonal to midzonal (zone 2) in the liver samples from four farms and periacinar (zone 3) in those from three farms, but some livers showed only single‐cell necrosis. Multinucleate hepatocytes near necrotic areas were a feature in six cases. Proximal tubular epithelium appeared to be the primary renal target and brown granules were often present in renal tubules. Biochemical and histological evidence of liver and kidney damage was obtained from two sheep experimentally pen‐fed harvested L. hyssopifolia. Conclusion Chemicals in L. hyssopifolia are toxic to ovine hepatocytes and renal tubular epithelial cells. 相似文献
90.
This study tests a rapid, user-friendly method for assessing changes in erosion risk, which yields information to aid policy development and decision-making for sustainable natural resources management. There is currently a lack of timely, up-to-date and current information to support policy development on sustainable natural resources management in Uganda. The study was carried out in the Ngenge watershed, a typical catchment in the Ugandan Highlands, characterised by deforestation in favour of subsistence agriculture without adequate soil and water conservation measures. The watershed is experiencing soil erosion, sedimentation and flooding problems which are threatening agricultural productivity and food security. Sustainable management of environmental resources is needed to ensure a livelihood for the rural population which is dependent on the land. Historical erosion risk was evaluated in three steps using multi-temporal satellite data. First, current erosion risk was assessed by combining slope and vegetation cover during periods of high intensity rainfall. The data used for the assessment was obtained from public (free) satellite images. Erosion risk was then linked to land use and finally to the change in vegetation cover over the years 1980-2000. The analysis of erosion risk using rainfall, slope and NDVI (Normalised Difference Vegetative Index) as a proxy for vegetation cover gives an indication of the current erosion risk in the area. The results of historical vegetation cover change analysis indicate an overall increase in areas under erosion risk in the study area from 1980 to 2000. This method of erosion risk mapping provides a quick and straightforward means for identifying priority areas for interventions for soil and water resource management. Considering that resources are limited, the interventions to be appropriate have to be focused mainly on areas affected by degradation. 相似文献