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   196篇
  免费   16篇
林业   6篇
农学   9篇
  28篇
综合类   19篇
农作物   10篇
水产渔业   38篇
畜牧兽医   92篇
园艺   5篇
植物保护   5篇
  2021年   6篇
  2020年   3篇
  2019年   5篇
  2018年   1篇
  2017年   3篇
  2016年   9篇
  2015年   6篇
  2014年   4篇
  2013年   11篇
  2012年   7篇
  2011年   10篇
  2010年   4篇
  2009年   4篇
  2008年   6篇
  2007年   6篇
  2006年   2篇
  2005年   9篇
  2004年   5篇
  2003年   8篇
  2002年   7篇
  2001年   6篇
  2000年   8篇
  1999年   4篇
  1998年   4篇
  1997年   2篇
  1996年   6篇
  1995年   4篇
  1993年   2篇
  1992年   4篇
  1991年   2篇
  1990年   2篇
  1989年   3篇
  1988年   1篇
  1987年   7篇
  1986年   8篇
  1985年   4篇
  1984年   1篇
  1983年   4篇
  1982年   6篇
  1981年   1篇
  1980年   3篇
  1979年   2篇
  1978年   1篇
  1977年   3篇
  1976年   1篇
  1975年   1篇
  1972年   1篇
  1967年   1篇
  1943年   2篇
  1942年   1篇
排序方式: 共有212条查询结果,搜索用时 15 毫秒
1.
Corneal ulceration is a common ophthalmic condition in horses. It is frequently caused by trauma to the corneal surface, followed by secondary infection by commensal or pathogenic organisms including Streptococcus equi subspecies zooepidemicus, Pseudomonas aeruginosa and Staphylococcus spp. Emerging antimicrobial resistance amongst these organisms has raised the need for appropriate antimicrobial therapy selection, to optimise treatment efficacy while minimising further antimicrobial resistance. Medical records of 38 horses presented at the University Veterinary Teaching Hospital Camden for ulcerative keratitis between 2010 and 2020 were reviewed to identify those with positive bacterial cultures and antimicrobial susceptibility profiles (13/38). Common susceptibility patterns were identified and used to guide the empirical treatment of equine bacterial corneal ulcers. Pseudomonas spp. (64.3%), Streptococcus equi subspecies zooepidemicus (14.3%) and Actinobacillus spp. (14.3%) were most commonly identified. Susceptibility to amikacin, gentamicin and ciprofloxacin was observed in 100%, 66.7% and 85.7% Pseudomonas spp. isolates respectively. Resistance to polymyxin B and neomycin occurred in 85.7% and 71.4% of Pseudomonas spp., respectively. All Streptococcus equi subspecies zooepidemicus organisms in this study were susceptible to ceftiofur, cephalexin, penicillin and ampicillin, while they were all resistant to gentamicin, neomycin, enrofloxacin and marbofloxacin. Predominating in this study, Pseudomonas spp. maintained overall aminoglycoside susceptibility despite some emerging resistance, and good fluoroquinolone susceptibility. High resistance to Polymyxin B could have arisen from its common use as first-line therapy for bacterial corneal ulcers. Although further research is required, these new findings about predominant bacteria in equine corneal ulceration in the Camden region and their antimicrobial susceptibility patterns can be used to guide the empirical treatment of bacterial corneal ulcers in horses.  相似文献   
2.
  • 1. Giant clams have been a sustainable resource for millennia, but unregulated harvesting has led to local extinctions within the Indo‐Pacific region. Giant clam mariculture can produce large numbers of juveniles for restocking wild populations where natural recruitment is low or absent.
  • 2. Singapore is surrounded by more than 60 small islands, many with fringing reefs. These reefs, however, experience increased turbidity and sedimentation resulting from massive coastal development projects and regular dredging of shipping lanes.
  • 3. Seven reefs off Singapore's southern islands were surveyed (9670 m2) for giant clams. Also, an experiment was conducted to determine the growth of Tridacna squamosa reared in aquaria under three light treatments: ~50% ambient photosynthetically active radiation (PAR); ~25% ambient PAR; and ~12% ambient PAR. Finally, 144 clams (T. squamosa) were transplanted to four reefs around Singapore to study survival and growth in a heavily impacted environment.
  • 4. A total of 23 adult clams from three species were found during the survey, representing a mean density of 0.24 per 100 m2. Most clams were found at Raffles Lighthouse, Singapore's ‘best’ reef. No juvenile clams were encountered. In the aquarium experiment, clam growth was significantly different among the three light treatments, with growth greatest in the ~50% ambient PAR treatment. Of the 144 transplanted clams, 116 (80.6%) were recovered after 7 months. All specimens had increased in size, with growth rates among reefs ranging from 3.3 mm month?1 (SD=1.3 mm) to 4.8 mm month?1 (SD=1.6 mm).
  • 5. Results suggest that, despite high levels of sedimentation and turbidity on Singapore's reefs, giant clams can survive and grow well. Restocking efforts using maricultured clams may be effective in enhancing the dwindling local populations. It is not clear, however, whether a self‐sustaining community can be established as high sedimentation may hinder larval settlement and survival.
Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   
3.
The screening for insecticidal principles from several Chinese medicinal herbs showed that the root bark of Dictamnus dasycarpus possessed significant feeding deterrence against two stored-product insects (Tribolium castaneum and Sitophilus zeamais). From the methanol extract, two feeding deterrents were isolated by bioassay-guided fractionation. The compounds were identified as fraxinellone and dictamnine from their spectroscopic data. Fraxinellone was demonstrated to possess feeding deterrent activity against adults and larvae of T. castaneum as well as S. zeamais adults with EC50 values of 36.4, 29.1, and 71.2 ppm, respectively. Dictamnine was shown to have feeding deterrent activity against adults and larvae of T. castaneum as well as S. zeamais adults with EC50 values of 57.6, 47.9, and 91.7 ppm, respectively.  相似文献   
4.
本文对比研究了棕仁粕、豆柏、花生粕的基础营养及体外胃蛋白酶消化性,通过在实验饲料中添加2%、6%、10%的棕仁粕制备了四份等氮等能的饲料,初步评价了添加棕仁粕对罗非鱼生长、体组分以及血清学参数的影响.结果表明:棕仁柏作为蛋白水平相对略低,纤维含量较高的植物蛋白替代源,其体外胃蛋白酶消化率与豆粕和花生粕无明显差异,可以作为膳食饲料组分适量的添加到水产动物饲料中,而不会影响罗非鱼的正常生长;在罗非鱼养殖实验中,添加2%棕仁粕的饲料组,罗非鱼的增重率,饲料系数,蛋白利用率、鱼体的蛋白组分以及血清学参数与对照组相比无显著差异(P>0.05),添加至6%~10%后,罗飞鱼的生长表现开始下降,饲料系数开始上升,鱼体蛋白组分下降(P<0.05).作为棕仁粕在水产养殖领域的初步探索性应用研究,研究认为棕仁粕是可以用于水产饲料的成分使用的,添加比例不宜超过6%.  相似文献   
5.
Six New Zealand topsoils of widely different origins and properties were subjected to 6m HC1 hydrolysis and the distribution of N fractions and amino acids were determined qualitatively and quantitatively.Of the total-N in the soils studied 83–91%, was hydrolysable with 6m HCl. The largest proportion of the hydrolysable N was α-amino acid N (38– 42%). followed by hydrolysable-unknown N (HUN) (14–24%), and NH4+-N (14–22%). A significant proportion (25–50%) of the HUN fraction was accounted for by the non α-amino acid-N. Oxidative (3% H2O2) hydrolysis released N-phenoxy amino acid-N and possibly N-compounds which were complexed with phenols and sugars. All soils had a similar amino-acid composition with a predominance of acidic amino-acids.  相似文献   
6.
Interleukin-1beta (IL-1beta) was isolated from LPS-stimulated brushtail possum alveolar macrophages using PCR primers based on conserved regions of mammalian IL-1beta. The complete cDNA was cloned by 5' and 3' rapid amplification of cDNA ends (RACE). The predicted protein of 269 amino acids shared 4346% identity with several mammalian IL-1beta proteins. Constructs were made to express the mature IL-1beta in Escherichia coli and two recombinant IL-1beta proteins, rpIL-1beta1 and rpIL-1beta2, which differed in length by four amino acids at the N-terminus, were produced. Both proteins induced a weak proliferative response in a possum thymocyte assay. Possums injected intravenously with 100 microg of rpIL-1beta1 or rpIL-1beta2 showed profound changes in body temperature and numbers of circulating leukocytes. A sharp decrease in temperature occurred within 2 h of administration followed by an elevation of temperature peaking at 24 h. The smaller rpIL-1beta1 protein had a greater effect on temperature than rpIL-1beta2. Both rpIL-1beta proteins caused a marked decrease in number of neutrophils and lymphocytes at 2-6 h after injection. At 24 h after injection, neutrophil and lymphocyte numbers were elevated 6.0-fold and 2.6-fold, respectively in the possums injected with rpIL-1beta1 and 3.9-fold and 1.5-fold, respectively in the possums injected with rpIL-1beta2. Fibrinogen levels were elevated at 24 and 72 h after injection with both proteins. In comparison, neither recombinant bovine IL-1beta (rbIL-1beta) nor PBS had significant effects on body temperature or blood haematology. The studies have shown that the two recombinant forms of IL-1beta were biologically active in possums and that the IL-1beta with four fewer amino acids at the N-terminus was the more active.  相似文献   
7.
Double-chambered right ventricle (DCRV) is possibly an emerging congenital cardiac anomaly in dogs. The defect causes clinical and pathophysiologic signs similar to those of congenital pulmonic stenosis in dogs but has distinct diagnostic features, breed predilections, and implications for treatment. The defect is often associated with clinical signs early in life. Surgical correction of DCRV can be undertaken with the aid of cardiopulmonary bypass and offers the prospect of an improved clinical outcome.  相似文献   
8.
Abstract: The cytologic and histologic features of 2 intracranial and 2 spinal (extramedullary cervical) canine meningiomas were compared. Cerebrospinal fluid analysis in 2 cases revealed mild, mixed cell pleocytosis, primarily composed of small lymphocytes and monocytoid cells, with a moderate increase in total protein concentration. Cytologic features suggestive of meningioma included cells with both epithelial and mes-enchymal characteristics and a tendency towards cell clustering. Tumor location also was useful in making a diagnosis. The 4 meningiomas differed histologically from one another, and included angioblastic, psam-momatous, meningotheliomatous, and microcystic anaplastic types, which conformed to a classification scheme for human meningiomas. The classification scheme could not be applied to cytologic specimens.  相似文献   
9.
Objective: To determine the frequency of the systemic inflammatory response syndrome (SIRS) in canine pyometra and to evaluate the relationship between C‐reactive protein (CRP), tumor necrosis factor α (TNFα), interleukin‐6 (IL‐6), and SIRS. Design: Prospective clinical study. Setting: Veterinary teaching hospital. Animals: Fifty‐three clinical cases of canine pyometra and 19 healthy control bitches. Interventions: Upon admission to the veterinary hospital, history and physical examination findings, including previously defined clinical SIRS parameters, were documented. Blood samples were obtained for hematology and biochemical tests and for CRP, TNFα, and IL‐6 analysis. The diagnosis of pyometra was confirmed by histopathology of the uterus after ovariohysterectomy. After surgery, clinical SIRS parameters, length of hospitalization, and mortality were recorded. Measurements and main results: Pyometra dogs were grouped as SIRS positive (30/53; 57%) or SIRS negative (23/53; 43%). Logistic regression showed that CRP was the only parameter that significantly related to SIRS apart from the clinical criteria that define this syndrome. The mortality rate was low (2/53; 3.8%), and conclusions regarding association with SIRS could not be drawn. A positive SIRS status, high plasma CRP concentration, and high body temperature were variables that related to increased morbidity reflected by the length of hospitalization. Conclusions: SIRS was seen in 57% of canine pyometra cases and a positive SIRS status showed a positive association with prolonged hospitalization. The mortality rate was low (3.3%) among SIRS positive dogs, indicating that progression to multiple organ dysfunction syndrome (MODS) rarely occurs in surgically treated cases of pyometra. CRP was associated with SIRS and with prolonged hospitalization. Further studies of plasma CRP may be warranted in canine intensive care cases susceptible to development of SIRS and MODS.  相似文献   
10.
K.M Goh  W.A Pullar 《Geoderma》1977,18(4):265-278
Tephra samples from Whakatane Ash and Rotoma Ash in central North Island of New Zealand were subject to a wide range of chemical treatments in order to isolate different components of soil organic matter for radiocarbon dating. These samples were radiocarbon-dated before and after treatments and were then compared with radiocarbon dates derived from charcoal in the same tephra formation.Tephra deposits when dated as whole samples without prior chemical treatments, yielded unreliable radiocarbon dates. The reliability was improved by chemical treatments, particularly those involving acid hydrolysis with 6 M HCl or 72% H2SO4. Improvement, however, was less using the classical humus extraction and fractionation procedure.  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