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   180篇
  免费   4篇
  国内免费   1篇
林业   23篇
农学   20篇
基础科学   8篇
  47篇
综合类   9篇
农作物   23篇
水产渔业   14篇
畜牧兽医   22篇
园艺   6篇
植物保护   13篇
  2023年   3篇
  2022年   7篇
  2021年   3篇
  2020年   4篇
  2019年   9篇
  2018年   10篇
  2017年   9篇
  2016年   6篇
  2015年   4篇
  2014年   5篇
  2013年   18篇
  2012年   11篇
  2011年   11篇
  2010年   16篇
  2009年   8篇
  2008年   12篇
  2007年   6篇
  2006年   7篇
  2005年   5篇
  2004年   1篇
  2003年   3篇
  2002年   1篇
  2001年   3篇
  1999年   1篇
  1998年   1篇
  1996年   4篇
  1994年   2篇
  1993年   2篇
  1992年   2篇
  1991年   1篇
  1988年   1篇
  1987年   1篇
  1986年   2篇
  1985年   1篇
  1984年   1篇
  1982年   1篇
  1981年   1篇
  1973年   1篇
  1965年   1篇
排序方式: 共有185条查询结果,搜索用时 0 毫秒
151.
This paper presents the results of the first survey for Prunus necrotic ringspot virus (PNRSV) on nectarine ( Prunus persica ) in India, where stone fruits are grown on a commercial scale. Using basic diagnostic techniques such as ELISA and RT-PCR, the occurrence of Prunus necrotic ringspot virus is reported for the first time on nectarine ( Prunus persica ) in India.  相似文献   
152.
Sapindus mukorossi Gaertn. (Sapindaceae) is commercially an important plant much valued for its fruits commonly known as soap nut as well as for the seed oil used as a feed-stock for biodiesel production. Molecular polymorphism, determined, using three single primer amplification reaction (SPAR) methods (RAPD, DAMD and ISSR) is used to assess the genetic variability in 69 accessions of S. mukorossi Gaertn., encompassing different geographical regions in India. Cumulative band data generated using the three SPAR methods resulted in 82.49% polymorphism across all genotypes of S. mukorossi Gaertn. UPGMA tree showed two major clusters that were in accordance with the geographical diversity. The intra-population genetic diversity (0.16), Shannon information index (0.24) and polymorphic loci (45.62%) were highest in AS population, while the corresponding lowest values were recorded in HP population. The inter-population average distance ranged from 0.05 (GA and HP) to 0.26 (AP and HP). Based on these distances, the UPGMA tree for the populations was computed, which showed the presence of two major clusters. Cluster I contained all the populations from Himachal Pradesh (HP) and Uttarakhand (GA and KU) and cluster II grouped the populations from North Eastern region (AS, AP, MG). The present study showed that SPAR methods are informative and useful to unravel the diversity among different populations of the soap nut plants and is a prelude for further utilization of promising and genetically divergent materials in the breeding programmes.  相似文献   
153.
Ammonia is a metabolite of aquatic organisms which might reach deleterious levels in intensive fish farms. The aim of the present study was to determine median lethal concentrations (96‐h LC50) of total ammonia nitrogen (TA‐N) on marbled spinefoot rabbitfish (Siganus rivulatus) and chronic effects of TA‐N on survival, growth and behaviour of juvenile rabbitfish over a 50 day period. In the first experiment, fish were exposed to 0, 2, 4, 6, 8, 10, 12, 14, 16, 18 and 20 mg L?1 TA‐N for 96 h and survival evaluated. In the second experiment, 12 fish were stocked per 50‐L tank and treated with one of 0, 2, 4, 6, 8, 10 and 12 mg L?1 TA‐N with three replicate tanks per treatment. Survival and growth were determined and histopathological alterations of gills due to chronic ammonia exposure were studied by light and electron microscopy. The 96‐h LC50 values were 16–18 mg L?1 TA‐N. In the chronic exposure experiment, fish reared in water with 0 mg L?1 TA‐N had 100% survival and had 50% weight increase in 50 days. Fish at 2 and 4 mg L?1 TA‐N all died whilst fish in 6, 8, 10 and 12 mg L?1 TA‐N survived and grew albeit less than in treatment 0 mg L?1. Gills from ammonia treated fish displayed severe histological and ultrastructural alterations including hyperplasia, hypertrophy and fusion of secondary lamellae, aneurysms and presence of pleomorphic altered cells. Chronic exposure to ammonia is deleterious to marbled spinefoot rabbitfish and low concentrations of ammonia appear to kill the fish in <50 days whilst fish can survive for more than 50 days at concentrations between 6 and 12 mg L?1 TA‐N.  相似文献   
154.
The objective of this clinical study was to report the prevalence of ocular disorders in a large population of horses from the Indian army. Both eyes of 500 horses were examined using a direct ophthalmoscope and by a transillumination procedure. Intraocular pressures were measured in several study horses. Fluorescein dye, Schirmer tear test, and menace testing were performed when indicated. Corneal culture swabs were collected from horses affected with corneal ulcers found on ophthalmoscopic examination. A total of 100 horses were found to be affected with some form of ocular disorder. The eye problems recorded were congenital eye lid disorders (2%) and included a subcutaneous cyst in the lower eye lid and slit in upper eye lid; conjunctivitis (12%); chronic interstitial keratitis (30%); a parasite in the anterior chamber (1%), which was however not removed for genus and species identification; phthisis bulbi (1%); uveitis (24%); glaucoma (13%); cataracts (3%); unilateral retinal hemorrhage (1%); luxation of cataractous lens (3%); posterior synechia (2%); and corneal ulceration (8%). Pseudomonas spp was the most common bacteria identified in horses affected with corneal ulceration. Vision-threatening ocular disorders are high in Indian army horses; this is a cause of major concern for the rider and the horse and, therefore, it is important to include ocular examination in horses as part of a routine and complete physical examination.  相似文献   
155.
The Timorese River Buffalo (Bubalus bubalis) plays a major role in the East Timor economy, as it is an important source of animal protein in human nutrition. They are widely spread throughout the country and are in direct contact with the populations. In spite of this proximity, information on their microbiota is scarce. This work aimed at characterizing the skin microbiota of the East Timorese River Buffalo and its antimicrobial resistance profile. Skin swab samples were taken from 46 animals in surveys conducted in three farms located in “Suco de Nairete”, Lospalos district, during July and August 2006. Bacteria were isolated and identified according to conventional microbiological procedures. A total of 456 isolates were obtained, including Gram-positive (n = 243) and Gram-negative (n = 213) bacteria. Due to their importance as potential pathogens and as vehicles for antimicrobial resistance transmission, Gram-positive cocci (n = 27) and bacilli (n = 77) isolates were further characterized, and their antimicrobial resistance profile determined by the disk diffusion method according to the Clinical and Laboratory Standards Institute guidelines. This study shows the high bacterial diversity of B. bubalis skin microbiota, representing an important first step towards understanding its importance and epidemiologic role in animal health. It also points out the potential role of these animals as vectors of antimicrobial resistant bacteria dissemination and the importance of antimicrobial resistance monitoring in developing countries.  相似文献   
156.
The goal of this study was to characterise chemical and histochemical properties of five dipterocarp timber wood species (Dipterocarpus kerrii, Hopea plagata, Parashorea malaanoman, Shorea almon, and Shorea contorta) differing in wood service life and utilisation. Wood of H. plagata, the most durable species, contained the lowest concentrations of nitrogen and ligno-protein, the highest C/N ratio and the lowest lignin concentration per dry mass but the highest lignin and extractive concentrations per wood density. FTIR spectroscopic studies of wood and isolated lignins of D. kerrii and H. plagata revealed differences compared to P. malaanoman and Shorea sp., which are species with short service life. Lignins of the Shorea/Parashorea species had a higher G/S ratio than those of H. plagata and D. kerrii. This was also evident from histochemical staining. Principle component analysis of FTIR spectra identified differences in both lignin composition and ligno-protein content as major source of variation.  相似文献   
157.
通过问卷调查的方式,调查了孟加拉国曼尼普尔部落对民族药用植物的利用。发现有26个科29个属32种药用植物用于治疗37种疾病。结果表明:所调查的32种植物中,多利用其地上部分(86%),而地下部分的利用相对较少(14%)。在植物药用制备中,叶片的使用最高(17个种),接下来依次是树皮、果实、根/地下茎、整个植株、种子和花。在32个植物种中,用于治疗痢疾的物种有10个,治疗发烧和风湿病的物种各5个,治疗哮喘、便秘、创伤和皮肤病的各4个物种,低烧病、咳嗽、腹泻各3种。32个物种中,72%的药用植物都能治疗至少一种疾病:75%口服使用,9%外服用,16%口服和外服结合使用。本研究突出了民族植物研究的潜力和迫切需求获取药用植物在人类健康利用的健康医疗实践知识。  相似文献   
158.
Circadian rhythms are daily oscillations of multiple biological processes directed by endogenous clocks. The circadian timing system comprises peripheral oscillators located in most tissues of the body and a central pacemaker located in the suprachiasmatic nucleus (SCN) of the hypothalamus. Circadian genes and the proteins produced by these genes constitute the molecular components of the circadian oscillator which form positive/negative feedback loops and generate circadian rhythms. The circadian regulation extends beyond clock genes to involve various clock-controlled genes (CCGs) including various cell cycle genes. Aberrant expression of circadian clock genes could have important consequences on the transactivation of downstream targets that control the cell cycle and on the ability of cells to undergo apoptosis. This may lead to genomic instability and accelerated cellular proliferation potentially promoting carcinogenesis. Different lines of evidence in mice and humans suggest that cancer may be a circadian-related disorder. The genetic or functional disruption of the molecular circadian clock has been found in various cancers including breast, ovarian, endometrial, prostate and hematological cancers. The acquisition of current data in circadian clock mechanism may help chronotherapy, which takes into consideration the biological time to improve treatments by devising new therapeutic approaches for treating circadian-related disorders, especially cancer.  相似文献   
159.
Grain and stover yield are key traits for the improvement of rabi sorghum varieties and hybrids in India. Large genotype-by-environment interactions (GEI) were identified for both grain and stover yield based on 10 years’ data available from the All India Coordinated Sorghum Improvement Program (AICSIP) experiments conducted from 1986/87 to 1996/97. From the estimates of the genotypic, GEI and residual components of variance for the four traits, a multi-environment testing strategy based on 15–20 locations, 2–3 years, and two replicates per trial would be required to achieve estimates of repeatability of approximately 0.70 for grain yield, 0.45 for stover yield, 0.70 for flowering time, and 0.85 for plant height.  相似文献   
160.
The ammonia flux from a green manured field was measured at a site in southern Italy. The green manure was provided by ploughing in about 66 and 78 t ha−1 of broad beans at the flowering stage during the spring in 1995 and 1996. The NH3 flux was estimated by means of the micrometeorological simplified aerodynamic method with the ammonia concentration measured at two levels above soil surface. Ammonia concentration was measured over a 2–3 h sampling period by trapping air NH3 in a H2SO4 solution and analysing this sample in the laboratory with the colorimetric method using the Nessler solution. About 70% of the total amount of ammonia was emitted in the first two days immediately after manuring. The NH3 flux was regulated by the same mechanism as the water vapour transport. Seventy percent of the daily ammonia was emitted around noon. The ammonia emission stopped during rainy and cold days and started again as soon as solar radiation, soil and air temperature increased, following plant decomposition. The total amount of ammonia emitted in the experimental period (28 days in 1995 and 18 days in 1996) was about 13 kg ha−1 for both years.  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