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   504篇
  免费   57篇
  国内免费   1篇
林业   50篇
农学   19篇
基础科学   2篇
  94篇
综合类   43篇
农作物   43篇
水产渔业   82篇
畜牧兽医   172篇
园艺   7篇
植物保护   50篇
  2023年   4篇
  2022年   7篇
  2021年   8篇
  2020年   28篇
  2019年   32篇
  2018年   30篇
  2017年   32篇
  2016年   28篇
  2015年   21篇
  2014年   31篇
  2013年   45篇
  2012年   32篇
  2011年   32篇
  2010年   27篇
  2009年   21篇
  2008年   26篇
  2007年   15篇
  2006年   16篇
  2005年   19篇
  2004年   15篇
  2003年   8篇
  2002年   18篇
  2001年   5篇
  2000年   9篇
  1999年   9篇
  1997年   4篇
  1996年   2篇
  1995年   1篇
  1994年   1篇
  1993年   2篇
  1992年   2篇
  1991年   2篇
  1990年   1篇
  1989年   1篇
  1988年   4篇
  1986年   2篇
  1985年   1篇
  1984年   1篇
  1983年   2篇
  1982年   2篇
  1979年   1篇
  1978年   2篇
  1977年   3篇
  1975年   1篇
  1972年   1篇
  1971年   2篇
  1970年   1篇
  1968年   2篇
  1928年   1篇
  1926年   1篇
排序方式: 共有562条查询结果,搜索用时 46 毫秒
81.
Dromedary camels complaining from conception failure or abortion were investigated and their herders interviewed in Al Ahsa province, Kingdom of Saudi Arabia (KSA) during 2013 and 2015. The most important reproductive disorder according to the responders is uterine infection (60.2%) followed by obesity (22.3%) then physiological conditions (hormonal disturbances; 7.8%), adhesions (3.9%) and repeat breeders (2.9%). Of the camel herders, 78.6% reported previous occurrence of abortion in their herds and 46% reported abortion cases in the last season (2015/2016), while 21.4% reported no history of abortion. Most of the responders (97.1%) do not call a veterinarian for cases of abortion in their herds and 53.4% do not discard aborted materials. The majority of the herders (76.7%) deny that handling aborted materials or touching vaginal fluids can result in human infection, or replied they do not know. Uterine swab samples were collected and tested by PCR for seven potential pathogens and sera tested for antibodies against bovine viral diarrhea virus (BVDV) and Brucella. Five pathogens were identified in infected uterine samples, namely Coxiella burnetii (36%), Campylobacter spp. (27%), Brucella spp. (17%), Salmonella spp. (13%), and Chlamydia spp. (7%). Sero-prevalence of Brucella and BVDV was 8.2 and 29.1% in overall sera, respectively, and varies with regard to the region. The findings of the present study demonstrate that reproductive disorders dominated by uterine infections and abortions are widespread in dromedary camels in KSA.  相似文献   
82.
Animal rearing is the major occupation of most population of South Asian countries. Due to lack of resources and limited approach to modern medicine, most of the livestock raisers prefer to use plant-based traditional medicine also referred to as ethnoveterinary medicine (EVM). Indeed, the use of medicinal plants in South Asia dates back to several centuries with documented evidences. However, there is currently a dearth of documentation and compilation of use of medicinal plants for animal diseases in this part of the world. This review aims to provide an up-to-date compilation of common medicinal plants used for the treatment and/or management of common animal diseases in South Asian countries. Extensive literature search was conducted online and relevant data was retrieved from well-known scientific databases. A total of 276 plants belonging to 95 families have been documented to be in common use for managing 14 different categories of animal diseases. Solanaceae, Lamiaceae, Fabaceae, and Leguminosae were most common plant families in terms of their plant species used for EVM. Gastric diseases were commonly reported and accounted for 72 species of plants used for its treatment followed by the miscellaneous disorders category and skin diseases comprising of 65 and 39 plant species respectively. Herbs accounted for 46% of the total plant species, followed by trees (33%), and shrubs (18%). The EVM were applied through different routes of administration; oral administration accounted for 72% followed by topical application 27%, while burning of plant parts to create smoke around animals to repel insects was less common (1%). It is anticipated that the present review will stimulate further ethnoveterinary research among livestock disease management practices in South Asia.  相似文献   
83.
The performance of the novel chitin metal silicate (CMS) co-precipitates as a single multifunctional excipient in tablet formulation using direct compression and wet granulation methods is evaluated. The neutral, acidic, and basic drugs Spironolactone (SPL), ibuprofen (IBU) and metronidazole (MET), respectively, were used as model drugs. Commercial Aldactone®, Fleximex® and Dumazole® tablets containing SPL, IBU and MET, respectively, and tablets made using Avicel® 200, were used in the study for comparison purposes. Tablets of acceptable crushing strength (>40 N) were obtained using CMS. The friability values for all tablets were well below the maximum 1% USP tolerance limit. CMS produced superdisintegrating tablets (disintegration time < 1 min) with the three model drugs. Regarding the dissolution rate, the sequence was as follow: CMS > Fleximex® > Avicel® 200, CMS > Avicel® 200 > Dumazole® and Aldactone® > Avicel® 200 > CMS for IBU, MET and SPL, respectively. Compressional properties of formulations were analyzed using density measurements and the compression Kawakita equation as assessment parameters. On the basis of DSC results, CMS co precipitates were found to be compatible with the tested drugs. Conclusively, the CMS co-precipitates have the potential to be used as filler, binder, and superdisintegrant, all-in-one, in the design of tablets by the direct compression as well as wet granulation methods.  相似文献   
84.
85.
  • ? Interpopulation variation in key functional traits of Pinus pinaster Ait. is well recognized. However, the relative importance of drought tolerance to explain this regional variation in the species remains elusive.
  • ? Here, we raise the question whether water availability constitutes a likely driver of regional variation in biomass allocation, growth and morphological traits of ten populations that cover the distribution range of P. pinaster. We carried out an experiment where seedlings of five families per population were submitted to two contrasting watering treatments.
  • ? The effects of water availability and population were significant for relative diameter and height growth rate, biomass allocation and number of lateral stems and dwarf shoots. Total dry mass significantly differed between watering treatments but it did not among populations. Populations could be clustered into four main groups. Root mass fraction explained most of the variation and significantly correlated to altitude but not to aridity.
  • ? The geographical pattern of genetic variation found in morphology and biomass allocation did not translate into population differences in drought tolerance or phenotypic plasticity to water availability, indicating that water availability is not a likely driver of the regional variation observed in the studied traits of P. pinaster at the seedling stage.
  •   相似文献   
    86.
    Chlamydophila pecorum found in the intestine and vaginal mucus of asymptomatic ruminants has also been associated with different pathological conditions in ruminants, swine and koalas. Some endangered species such as water buffalos and bandicoots have also been found to be infected by C. pecorum. The persistence of C. pecorum strains in the intestine and vaginal mucus of ruminants could cause long-term sub-clinical infection affecting the animal’s health. C. pecorum strains present many genetic and antigenic variations, but coding tandem repeats have recently been found in some C. pecorum genes, allowing C. pecorum strains isolated from sick animals to be differentiated from those isolated from asymptomatic animals. This review provides an update on C. pecorum infections in different animal hosts and the implications for animal health. The taxonomy, typing and genetic aspects of C. pecorum are also reviewed.  相似文献   
    87.
    Previously, the distribution of myoepithelial cells (mecs) in the salivary glands was studied by both immunohistochemistry, and transmission electron microscopy; however, little was elucidated concerning their morphological features, especially in goats. This study was performed to investigate the correlation between the cytoarchitecture of the mecs in goat major salivary glands (parotid, mandibular, and sublingual glands) and the nature of the saliva secretion. The cytoarchitectural features of the mecs were examined by scanning and transmission electron microscopy as well as immunohistochemically. The secretory endpieces in the parotid gland are of the pure serous type, but in both the mandibular and sublingual glands they are of the mixed type. In all studied glands, the intercalated ducts were covered by mecs which, unlike the large stellate cells that surrounded the secretory endpieces, were spindle-shaped with few cytoplasmic processes. Interestingly, the mecs were found to bulge on the basal surfaces of the serous acini and intercalated ducts in all glands and to be in close contact to the seromucous tubules surface in the mandibular and sublingual glands forming a continuous network around it. In conclusion, the differences in the degree of development of the mecs as well as the number of their cytoplasmic processes may be correlated with the nature of the secretion and the number of the secretory granules. Thus these observations may have some relevance in the diagnosis of atrophy and pathogenic conditions of these glands.  相似文献   
    88.
    This study was conducted to evaluate the effects of dietary taurine on growth performance and feed utilization of Nile tilapia (Oreochromis niloticus) larvae. Four plant protein‐based, isonitrogenous (400 g kg?1 protein), isoenergetic (19 MJ kg?1) diets supplemented with four taurine concentrations (0.0, 5.0, 10.0 and 15.0 g kg?1; designated as T0, T0.5, T1 and T1.5, respectively) were prepared. The diets were fed to triplicate groups of fish larvae (0.024 g average body weight), to apparent satiation, three times per day for 60 days. Larval growth rates and feed utilization efficiency were significantly improved with increasing supplemental taurine up to 10 g kg?1 and decreased with further taurine supplementation. The quadratic regression analyses indicated that the maximum larval performance occurred at about 9.7 g kg?1 of total dietary taurine. Fish survival was significantly lower at 15 g kg?1 dietary taurine than at other taurine levels. Body protein significantly increased, while body moisture and ash decreased, with increasing dietary taurine up to 10 g kg?1 and decreased with further taurine supplementation to 15 g kg?1. Body lipid was not significantly affected by dietary taurine concentration. A number of body amino acids (tryptophan, arginine, histidine, leucine, isoleucine, valine, alanine, glycine, threonine and taurine) significantly increased with increasing supplemental taurine up to 10 g kg?1 and then decreased with further increase in dietary taurine levels. The rest of body amino acids were not significantly affected by dietary taurine. The present results suggest that about 9.7 g kg?1 dietary taurine is required for optimum performance of Nile tilapia larvae fed soybean meal‐based diets.  相似文献   
    89.
    We determined the effects of petroleum spray oil (PSO) (Caltex Canopy®) on oviposition responses of Helicoverpa armigera Hubner and Ostrinia nubilalis Hubner adults, and larval survival of the pest moths on cotton and maize plants in the laboratory. Application of 2% (v/v) of the PSO deterred H. armigera oviposition. Increasing the rate from 2 to 5% (v/v) did not significantly reduce the number of eggs laid by H. armigera on the treated plants. In contrast, the minimum rate at which the oil could deter oviposition of O. nubilalis on maize plants was 5% (v/v). Increasing the rate from 5 to 10% (v/v) did not significantly reduce the number of eggs laid per plant. However, a reduction in the rate of the PSO from 5 to 3% (v/v) resulted in a 73.9% increase in oviposition activity on the maize plants. In wind tunnel bioassay tests, all mated H. armigera females tested could detect and settle on plants treated with water but with plants treated with PSO at various times, only 50% of tested females settled on the plants 4?–?5 days after treatment (DAT) and none on the plants 0?–?2 DAT. A solid phase micro-extraction (SPME) test to determine the effect of the PSO on volatiles released by the cotton plants showed that the quantity of volatiles released by the cotton plants treated with PSO was lower than for water treated plants. This indicates that the PSO sprays may be suppressing or masking the leaf surface volatiles of the cotton plants, thereby deterring oviposition of H. armigera. Larval survival data show that PSO sprays can cause direct mortality of first, second and third instar O. nubilalis larvae. PSOs may have the potential to be integrated into pest management programme targeting H. armigera and O. nubilalis on cotton and maize crops, respectively.  相似文献   
    90.
    Knowledge of relationships among the cultivated and wild species of Cerasus, a subgenus of Prunus L., is important for recognizing gene pools, identifying pitfalls in germplasm collections and developing effective conservation and management strategies. In this study, morphological characterization of wild Cerasus subgenus species naturally growing in Iran, including P. avium L. (mazzard), P. mahaleb L., P. brachypetala Boiss., P. incana Pall., P. yazdiana Mozaff., P. microcarpa Boiss. subsp. microcarpa, P. microcarpa Boiss. subsp. diffusa and P. pseudoprostrata Pojark. and three commercial species, sweet cherry (P. avium L.), sour cherry (P. cerasus L.) and duke cherry (P. × gondouinii Rehd.) was investigated. Twenty-nine variables were recorded in 95 accessions of these species to detect similarities among them. All studied characteristics were showing a high degree of variability, but it was highly pronounced for plant height, leaf characters especially for dimensions and pubescence as well as for petiole and peduncle length. The majority of significant correlation coefficients were found in the characteristics representing plant size and growth habit with leaf size. Principal component analysis was performed for phenotypical diversity determination and grouping of species. Characters with high discriminating values were those related to growth habit, height, compactness, trunk diameter, leaf dimensions, petiole length, leaf tip and serration, flower color, peduncle length, fruit shape and stone shape. Based on the cluster analysis, species included in two main clusters, first those with large structure (sweet, sour and duke cherries, mazzard and mahaleb), second the other species with small structure which might be potentially suitable for rootstock breeding programs. Scatter plot using two first factors also confirmed the grouping by cluster analysis. The conservation of the highly diverse native populations of Iranian wild Cerasus species is recommended.  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