首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   72篇
  免费   2篇
林业   6篇
农学   10篇
  5篇
综合类   8篇
农作物   15篇
水产渔业   4篇
畜牧兽医   20篇
园艺   1篇
植物保护   5篇
  2023年   1篇
  2022年   1篇
  2021年   1篇
  2020年   4篇
  2019年   3篇
  2018年   2篇
  2017年   6篇
  2016年   3篇
  2015年   5篇
  2014年   2篇
  2013年   5篇
  2012年   2篇
  2011年   8篇
  2010年   5篇
  2009年   1篇
  2008年   8篇
  2007年   5篇
  2005年   1篇
  2004年   1篇
  2000年   1篇
  1999年   1篇
  1996年   1篇
  1992年   1篇
  1991年   1篇
  1990年   2篇
  1987年   2篇
  1981年   1篇
排序方式: 共有74条查询结果,搜索用时 46 毫秒
31.
A 10-year old Lhasa Apso dog was presented for an acute history of exercise intolerance and hind limb weakness. High grade second degree atrioventricular block with an atrial rate of 200 beats per minute, ventricular rate of 40 beats per minute and an intermittent ventricular escape rhythm, was diagnosed on electrocardiograph. A transdiaphragmatic, unipolar, epicardial pacemaker was implanted without immediate surgical complications. Severe vomiting was noted 12 h post-operatively. Abdominal ultrasound and a barium study supported a diagnosis of pyloric outflow obstruction and exploratory abdominal surgery was performed. The pyloric outflow tract appeared normal and no other causes of an outflow obstruction were identified. The epicardial generator was repositioned from the right to the left abdominal wall. Pyloric cell pacing was presumed to be the cause for the pyloric obstruction and severe vomiting, and this was thought to be due to close proximity of the pacemaker generator to the pylorus situated in the right abdominal wall. Repositioning of the pulse generator to the left abdominal wall resulted in resolution of vomiting.  相似文献   
32.
More accurate estimation of crop evapotranspiration(ET_c)in a regional scale has always been one of the most important challenges.Temporal and spatial monitoring of ET_(c )using satellite images can help to enhance accuracy of estimations.In this study,the(ET_c)_(rice) maps were produced by using statistical/experimental methods based on crop coefficient(K_c)maps derived from vegetation index(Ⅵ).K_c was estimated using four methods,including linear relationship between K_c and Ⅵ(K_c-Ⅵ),calibrated model of K_c-Ⅵ,linear relationship between K_(cb)(the basal crop coefficient)and Ⅵ(K_(cb)-Ⅵ),and calibrated model of K_(cb)-Ⅵ.The results showed that calibrated model of K_c-Ⅵ had a better performance compared to the other methods,with normalized root mean square errors(NRMSE),mean absolute error and root mean square error being 5.7%,0.05 mm/d and 0.06mm/d,respectively.(ET_c)_(rice) maps were produced by using calibrated model of K_c-Ⅵ and reference evapotranspiration(ET_0)from FAO Penman-Monteith method.The NRMSE was 21.3%for using FAO Penman-Monteith method.Therefore,calibrated K_c-Ⅵ model in combining with ET_0 based on the Landsat 7 ETM+images could be provided a good estimation of(ET_c)_(rice) in regional scale,and can be applied to estimate water requirement due to the free and facilitate access.  相似文献   
33.
The effect of the administration of beneficial lactic acid bacteria (LAB): Lactococcus lactis CRL 1584, L. lactis CRL 1827, Enterococcus gallinarum CRL 1826 and combined CRL 1584+ CRL 1826 on the development of bullfrog embryos from the hatching stage until 31 days (tadpole) was evaluated. In vitro assays indicated that 103, 106 and 109 CFU mL?1 single LAB strains remained viable until 24 h in 10% Ringer. Around 109 CFU mL?1 LAB (individually and combined) were used in an experimental design built to evaluate their effect when administrated at different intervals (three 7‐day cycles with 5‐day rest periods in between) to embryos until day 31. The highest potentially beneficial population (LAB) numbers were detected in the LAB‐treated groups. All the LAB‐treatments increased it and were significantly higher than the controls. Although the highest, potentially pathogenic, population (Red‐Leg Syndrome‐RLS‐related pathogens) numbers were detected in the control and the lowest in the CRL 1584+ CRL 1826‐treated group, they did not differ significantly. Stereoscopic studies showed no malformations in any LAB‐treated group and all the specimens reached the same stage of their biological cycle with a survival >94%. The histological structure of target organs for RLS‐associated pathogens (intestine and skin) and stomach was not affected and the spleen was developed. Only the LAB‐treated groups showed microorganisms associated with the intestinal mucus, without inflammatory reaction in the lamina propria. This is the first report on the evaluation of the absence of adverse effects after LAB administration to bullfrog embryos using indigenous microorganisms.  相似文献   
34.
Effects of dietary supplementation of Tribulus terrestris (TT) and 17α‐methyl testosterone (MT) on growth performance and reproductive efficiency of male Nile tilapia, Oreochromis niloticus (N = 75, initial weight 60 ± 3.251 g), were evaluated. Five experimental treatments in triplicate were fed on basal diet (30% crude protein) (control group, CG), basal diet containing 60 mg MT (MT group) and basal diet containing 250, 500 and 750 mg/kg diet TT (TT250, TT500 and TT750 groups), respectively, for consecutive 45 days. Results revealed that the fish received TT in diet showed better growth performance (final body weight, weight gain, feed conversion ratio, specific growth rate, testes weight and gonadosomatic index) compared with MT and CG (p < .05), as well as for haemoglobin content and red blood cell count (p < .05). The highest level of testosterone, 11‐keto testosterone, sperm concentration and vitality was recorded in TT750 followed by TT500, TT250 and MT groups, while the lowest value was recorded in the CG (p < .05). The highest seminiferous tubule diameter was recorded in TT750 followed by TT500, TT250 and CG, while the lowest diameter was recorded in the MT group (p < .05). Fish received TT showed normal dilated seminiferous tubule filled with large amount of free sperms within their lumen in a dose related effect. In conclusion, male Nile tilapia dietary supplementation with different inclusions of Tribulus terrestris extract specially 500 and 750 mg/kg diet improves growth performance, health condition, semen quality and reproductive efficiency without any harmful effect on water quality.  相似文献   
35.
The potential impact on aquatic ecosystems of supplementing the diets of beef cattle with selenium (Se) was studied on 4 northern California ranches. All study sites included an area of concentrated use by cattle that had diets supplemented with Se. In each case, a stream flowed through the site and provided a control sampling area upstream and a treated sampling area downstream. Specimens of water, sediment, algae, aquatic plants, aquatic invertebrates, and fish were analyzed fluorometrically for total Se content. Significant differences in Se concentration were not found between specimens from upstream control areas and those from downstream areas subjected to use by Se-treated cattle. Evidence was not found that Se supplementation in cattle at maximal permitted concentrations caused Se accumulation in associated aquatic ecosystems.  相似文献   
36.
37.
In recent years, considerable interest has been focused on the use of physiological parameters as selection criteria in salt tolerance ranking. Eighteen bread wheat (Triticum aestivum L.) landraces from the west area of the Urmia Saline Lake were grown in a greenhouse in the Department of Plant Biology and Halophytes Biotechnology Center, Azarbaijan University of Tarbiyat Moallem, Tabriz, Iran to study the effects of increasing levels of sodium chloride (NaCl) (control, 75, and 150 mM) on the plant leaves. The experimental design was factorial with a randomized complete block with three replications. The results showed salinity caused an obvious decrease in growth of all landraces. Physiological parameters such as lipid peroxidation, hydrogen peroxide (H2O2) content, and cell membrane injury increased with increasing salinity levels with different degrees among the landraces. Salt stress increased the sodium (Na+) accumulation coupled with a decrease in leaf potassium (K+) depending on salinity levels. The analysis of variance showed significant effects of salinity, landraces and their interactions in all studied parameters. The landraces were ranked for salt tolerance indexes, and cluster group ranking ordered landraces from tolerant to sensitive and their properties for salt stress tolerance are open for further research.  相似文献   
38.
The present work was carried out to describe morphological features of the tongue and laryngeal entrance of the Common pheasantPhasianus colchicus, using light and scanning electron microscopy. The lingual apex was taper-shaped with a shallow median sulcus. A V-shaped papillary crest with 15–20 caudally directed conical papillae was located between the radix and corpus linguae. The second row of papillae consisting of three caudolaterally directed conical papillae was arranged caudal to the main papillary crest. The mons laryngealis was equipped caudally with a double-layer of large conical papillae as pharyngeal crest, and few small conical papillae were seen around the glottis. Scanning electron microscope (SEM) observation showed that the apex linguae and corpus were covered with compact filiform papillae, while the radix linguae were free of papillae. Numerous openings of salivary gland can be seen on the radix linguae and mons laryngealis at higher magnification. On histological sections, all parts of the tongue and mons laryngealis were covered with a keratinised stratified squamous epithelium. The keratinised layer became thinner rostro-caudally. The simple alveolar salivary glands were distributed in the submucosa from the apex linguae to the radix linguae as well as the mons laryngealis. PAS staining revealed mucin-secreting activity of this glands. According to the findings, although the tongue and laryngeal entrance of the Common pheasant is characteristics of a galliform bird, it has some features similar to passeriformes and falconiformes.  相似文献   
39.
Vakil A  Engheta N 《Science (New York, N.Y.)》2011,332(6035):1291-1294
Metamaterials and transformation optics play substantial roles in various branches of optical science and engineering by providing schemes to tailor electromagnetic fields into desired spatial patterns. We report a theoretical study showing that by designing and manipulating spatially inhomogeneous, nonuniform conductivity patterns across a flake of graphene, one can have this material as a one-atom-thick platform for infrared metamaterials and transformation optical devices. Varying the graphene chemical potential by using static electric field yields a way to tune the graphene conductivity in the terahertz and infrared frequencies. Such degree of freedom provides the prospect of having different "patches" with different conductivities on a single flake of graphene. Numerous photonic functions and metamaterial concepts can be expected to follow from such a platform.  相似文献   
40.
Curtis et al. (Research Articles, 2 March 2007, p. 1243) claimed discovery of a human neuronal migratory stream to the olfactory bulb along a putative lateral ventricular extension. However, high levels of proliferation reported with proliferating cell nuclear antigen were not confirmed using different markers, neuronal chain migration was not demonstrated, and no serial reconstruction shows a true ventricular extension.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号