全文获取类型
收费全文 | 168篇 |
免费 | 16篇 |
专业分类
林业 | 1篇 |
1篇 | |
综合类 | 29篇 |
农作物 | 3篇 |
水产渔业 | 2篇 |
畜牧兽医 | 142篇 |
植物保护 | 6篇 |
出版年
2020年 | 2篇 |
2019年 | 3篇 |
2018年 | 9篇 |
2017年 | 5篇 |
2016年 | 6篇 |
2015年 | 3篇 |
2014年 | 6篇 |
2013年 | 10篇 |
2012年 | 4篇 |
2011年 | 4篇 |
2010年 | 15篇 |
2009年 | 19篇 |
2008年 | 7篇 |
2007年 | 6篇 |
2006年 | 2篇 |
2005年 | 1篇 |
2004年 | 3篇 |
2003年 | 3篇 |
2001年 | 5篇 |
1999年 | 6篇 |
1998年 | 14篇 |
1997年 | 8篇 |
1996年 | 12篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 2篇 |
1988年 | 2篇 |
排序方式: 共有184条查询结果,搜索用时 0 毫秒
51.
JR Delaney DS Kelley MD Lilley DA Butterfield JA Baross WSD Wilcock RW Embley M Summit 《Science (New York, N.Y.)》1998,281(5374):222-230
Seafloor diking-eruptive events represent the irreducible, quantum events of upper oceanic crustal accretion. They record events by which a large portion of the oceanic crust has formed through geological history. Since 1993, the U.S. Navy's real-time Sound Surveillance System has allowed location of ongoing acoustic signatures of dike emplacement and basalt eruptions at ridge crests in the northeast Pacific. These diking-eruptive events trigger a sequence of related, rapidly evolving physical, chemical, and biological processes. Magmatic volatiles released during these events may provide nutrients for communities of subseafloor microorganisms, some of which thrive in high-temperature anaerobic environments. Many of the organisms identified from these systems are Archaea. If microorganisms can thrive in the water-saturated pores and cracks within deep, volcanically active portions of our planet, other hydrothermally active planets may harbor similar life forms. 相似文献
52.
根据目前拖网渔船在节能方面的需要,采用导管螺旋桨以改善渔船的推进性能,并对导管螺旋桨的设计和具体应用的优的缺点作初步的探讨。 相似文献
53.
54.
55.
The clinical, pathological and biochemical findings of a study of 30 Poll Hereford, Hereford, Poll Hereford cross or Hereford cross calves affected with branched chain ketoacid dehydrogenase (BCKAD) complex deficiency or maple syrup urine disease (MSUD) are presented. In breeding studies, 6 of 21 calves from obligate heterozygote matings were affected with MSUD, suggesting the disease is inherited in an autosomal recessive manner. Calves were clinically affected from birth, but there were variations in the subsequent course of progressive deterioration of central nervous system function. Concentrations of the branched chain amino acids and keto acids were elevated in pre-suckle plasma and cerebellar water content was higher in affected calves. Activity of BCKAD complex was minimal in fibroblasts cultured from an affected calf. Spongiform encephalopathy and elevated ratios of the branched to straight chain amino acids in formalin fixed cerebral tissue were found in a stillborn foetus and a 3-month-old Hereford calf. These findings suggest the disease occurs prenatally and that a delayed form may exist. 相似文献
56.
Background: The global network of eddy-covariance(EC) flux-towers has improved the understanding of the terrestrial carbon(C) cycle, however, the network has a relatively limited spatial extent compared to forest inventory data and plots. Developing methods to use inventory-based and EC flux measurements together with modeling approaches is necessary evaluate forest C dynamics across broad spatial extents.Methods: Changes in C stock change(ΔC) were computed based on repeated measurements of forest inventory plots and compared with separate measurements of cumulative net ecosystem productivity(ΣNEP) over four years(2003 – 2006) for Douglas-fir(Pseudotsuga menziesii var menziesii) dominated regeneration(HDF00), juvenile(HDF88and HDF90) and near-rotation(DF49) aged stands(6, 18, 20, 57 years old in 2006, respectively) in coastal British Columbia. ΔC was determined from forest inventory plot data alone, and in a hybrid approach using inventory data along with litter fall data and published decay equations to determine the change in detrital pools. These ΔC-based estimates were then compared with ΣNEP measured at an eddy-covariance flux-tower(EC-flux) and modelled by the Carbon Budget Model- Canadian Forest Sector(CBM-CFS3) using historic forest inventory and forest disturbance data.Footprint analysis was used with remote sensing, soils and topography data to evaluate how well the inventory plots represented the range of stand conditions within the area of the flux-tower footprint and to spatially scale the plot data to the area of the EC-flux and model based estimates.Results: The closest convergence among methods was for the juvenile stands while the largest divergences were for the regenerating clearcut, followed by the near-rotation stand. At the regenerating clearcut, footprint weighting of CBM-CFS3 ΣNEP increased convergence with EC flux ΣNEP, but not for ΔC. While spatial scaling and footprint weighting did not increase convergence for ΔC, they did provide confidence that the sample plots represented site conditions as measured by the EC tower.Conclusions: Methods to use inventory and EC flux measurements together with modeling approaches are necessary to understand forest C dynamics across broad spatial extents. Each approach has advantages and limitations that need to be considered for investigations at varying spatial and temporal scales. 相似文献
57.
AB Caselles A Miro‐Moran A Morillo Rodriguez JM Gallardo Bolaños C Ortega‐Ferrusola GM Salido FJ Peña JA Tapia IM Aparicio 《Reproduction in domestic animals》2014,49(2):254-262
Apoptosis in the testis is required to ensure an efficient spermatogenesis. However, sometimes, defective germ cells that are marked for elimination during this process escape elimination in the testes, giving rise to ejaculates with increased percentages of abnormal and apoptotic spermatozoa and a high percentage of apoptotic bodies. Apoptosis markers in the ejaculate have been associated with low fertility, either in animals or humans. Therefore, the goal of this study was to investigate whether fresh equine semen contains apoptotic bodies [initially named Merocyanine 540 (M540) bodies] and to study the relationship between the quantity of these bodies and cell concentration, the volume of ejaculate, viability and motility. Moreover, we also studied whether the presence apoptotic bodies in fresh semen was related to the resistance of the stallion spermatozoa to being incubated at 37°C or being frozen and thawed. Fresh equine semen was stained with fluorescent dyes such as M540 and Annexin‐V. Active Caspase 3 was studied in fresh semen through Western blotting and immunofluorescence with a specific antibody. Sperm kinematics was assessed in fresh, incubated and thawed samples using computer‐assisted semen analysis, and viability was evaluated with the LIVE/DEAD Sperm Viability Kit. Overall, our results demonstrate for the first time the presence of apoptotic bodies in equine semen. The quantity of apoptotic bodies was highly variable among stallions and was positively correlated with Caspase 3 activity in fresh samples and negatively correlated with the viability and motility of stallion spermatozoa after the cryopreservation process. 相似文献
58.
JM Baldrighi MF Sá Filho EOS Batista RNVR Lopes JA Visintin PS Baruselli MEOA Assumpção 《Reproduction in domestic animals》2014,49(6):1015-1020
This study was performed to evaluate plasma concentrations of anti‐Mullerian hormone (AMH) and the ovarian antral follicle population (AFP) in different genetic groups. Cyclic heifers (13 Bubalus bubalis [Murrah]; 15 Bos taurus [Holstein] and 10 Bos indicus [Gyr]) were maintained under the same management and were synchronized with two doses of 150 μg IM d‐cloprostenol administered 14 days apart. After the second d‐cloprostenol treatment, heifers had their ovaries scanned daily by ultrasound to define the day of ovulation. On the same day, the AFP was determined and a plasma sample was collected to measure AMH. Murrah heifers had less AFP (25.6 ± 2.1 follicles; p = 0.01) and plasma AMH concentration (0.18 ± 0.03 ng/ml; p < 0.001) than Gyr (60.0 ± 12.2 follicles and 0.60 ± 0.12 ng/ml of AMH); however, data were similar when compared to Holstein (35.9 ± 6.8 follicles and 0.24 ± 0.06 ng/ml of AMH) heifers. Regardless of genetic background, there was a positive relationship between the AFP and plasmatic AMH concentration (Murrah [r = 0.62; p < 0.01], Holstein [r = 0.66; p < 0.001] and Gyr [r = 0.88; p < 0.001]). Also, when heifers were classified according to high‐ or low‐AMH concentration based on the average within each genetic group, high‐AMH heifers had greater (p < 0.0001) AFP than low‐AMH heifers. In conclusion, both Murrah and Holstein heifers presented lower plasma AMH concentration and AFP when compared to Gyr. 相似文献
59.
60.
Evaluation of an Immunochromatographic Test to the Diagnosis of Canine Brucellosis Caused by Brucella canis 下载免费PDF全文
LB Keid JA Diniz TMFS Oliveira HL Ferreira RM Soares 《Reproduction in domestic animals》2015,50(6):939-944
This study evaluated the performance of an immunochromatographic test (ICT) for the diagnosis of canine brucellosis caused by Brucella canis, comparing its results with that of the rapid slide agglutination test with and without the use of 2‐mercaptoethanol and the agar gel immunodiffusion test (AGID). The microbiological culture, PCR and clinical examination were used as reference. According to the results obtained in clinical examination, blood culture, culture of semen and vaginal swab and PCR in blood, semen and vaginal swab, a total of 102 dogs were divided into three groups: B. canis‐infected dogs (Group 1), B. canis‐non‐infected dogs (Group 2) and dogs with suspected brucellosis (Group 3). The diagnostic sensitivity of RSAT, 2ME‐RSAT, AGID and ICT in Group 1 was, respectively, 75%, 37.5%, 27.8% and 89.58%. The diagnostic specificity of RSAT, 2ME‐RSAT, AGID and ICT in Group 2 was, respectively, 91%, 100%, 100%, and 100%. In dogs with suspected brucellosis, 9.67% were RSAT positive, none was positive by 2ME‐RSAT, 3.22% were AGID positive and 6.45% were ICT positive. The main drawback concerning canine brucellosis diagnosis is the lack of a highly sensitive serological assay to be used as a screening test to the rapid identification of infected animals. The ICT showed a high diagnostic specificity and a diagnostic sensitivity value greater than that observed in the RSAT, 2ME‐RSAT and AGID. However, 10.41% of infected dogs had negative results by ICT. These dogs were positive by microbiological culture and/or PCR, indicating active infection and consequently a higher potential of spreading Brucella. Although rapid and simple to perform, the ICT lacked sensitivity to be used as a screening test. 相似文献