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   1498篇
  免费   99篇
  国内免费   1篇
林业   94篇
农学   43篇
基础科学   4篇
  286篇
综合类   148篇
农作物   66篇
水产渔业   122篇
畜牧兽医   682篇
园艺   31篇
植物保护   122篇
  2023年   9篇
  2022年   12篇
  2021年   28篇
  2020年   52篇
  2019年   69篇
  2018年   43篇
  2017年   32篇
  2016年   44篇
  2015年   37篇
  2014年   53篇
  2013年   83篇
  2012年   86篇
  2011年   128篇
  2010年   63篇
  2009年   41篇
  2008年   96篇
  2007年   106篇
  2006年   105篇
  2005年   93篇
  2004年   91篇
  2003年   89篇
  2002年   70篇
  2001年   14篇
  2000年   13篇
  1999年   14篇
  1998年   11篇
  1997年   7篇
  1996年   12篇
  1995年   5篇
  1994年   8篇
  1993年   7篇
  1992年   4篇
  1991年   4篇
  1989年   5篇
  1987年   5篇
  1985年   5篇
  1984年   3篇
  1983年   5篇
  1982年   3篇
  1981年   7篇
  1980年   4篇
  1978年   4篇
  1974年   2篇
  1973年   4篇
  1971年   2篇
  1970年   2篇
  1969年   2篇
  1968年   2篇
  1966年   2篇
  1960年   2篇
排序方式: 共有1598条查询结果,搜索用时 10 毫秒
161.
OBJECTIVE : To report outcomes after cellophane banding of single congenital portosystemic shunts in dogs and cats. STUDY DESIGN : Retrospective study of sequential cases. ANIMALS : One hundred and six dogs and five cats. METHODS : Medical records were reviewed for breed, sex, age at surgery, shunt anatomy, results of pre- and postoperative biochemical analysis, development of postligation neurologic dysfunction, portal hypertension or other serious complications, and the owners' perception of their animal's response to surgery. RESULTS : Ninety-five dogs and all 5 cats had extrahepatic shunts. Eleven dogs had intrahepatic shunts. Six dogs (5.5%) died as a result of surgery from portal hypertension (2 dogs), postligation neurologic dysfunction (2), splenic hemorrhage (1) and suspected narcotic overdose (1). Serious complications were more common in dogs with intrahepatic shunts than those with extrahepatic shunts (P=.002). Postligation neurologic dysfunction necessitated treatment in 10 dogs and 1 cat; 8 dogs and the cat survived. Clinical signs attributed to portosystemic shunting resolved or were substantially attenuated in all survivors. Postoperative serum bile acid concentrations or results of ammonia tolerance testing were available for 88 animals; 74 (84%) were normal and 14 (16%) were abnormal. Multiple acquired shunts were documented in two animals. CONCLUSIONS : Cellophane banding is a safe and effective alternative to other methods of attenuation. CLINICAL RELEVANCE : Slow occlusion of portosystemic shunts using a variety of methods is being evaluated world wide. Cellophane banding is a relatively simple procedure with comparable safety and efficacy to previously reported techniques.  相似文献   
162.
163.
164.
165.
Solutions obtained by heating carrot roots in water (stocks) are widely used in the food industry, but little information is available regarding the metabolites (intermediates and products of metabolism) found in the stock. The effect of treatment temperature and duration on the sugar composition of stocks was investigated directly by quantitative (1)H NMR spectroscopy, to understand the extraction mechanism when processing at 100 degrees C. Stocks prepared at three different temperatures (50, 75, and 100 degrees C) were investigated for up to 36 h. Three sugars (sucrose, glucose, and fructose) were detected and quantified. The concentrations of these three sugars reached a maximum after 9 h when the temperature of treatment was 50 or 75 degrees C. At 100 degrees C, the sucrose concentration reached a maximum after 3 h, whereas the concentration of glucose and fructose was still increasing at that time. Comparison of the kinetic composition of these carrot stocks with that of model sugar solutions leads to the proposal that the changes in stock composition result from sugar diffusion, sucrose hydrolysis, and hydroxymethylfurfural (HMF) formation.  相似文献   
166.
Fusarium subglutinans causes maize ear rot and contaminates grain with the mycotoxin moniliformin. Previous DNA sequence analysis divided F. subglutinans from maize into two cryptic species, designated groups 1 and 2. Here, it was determined whether the two groups differ in the agriculturally important traits of virulence on maize and moniliformin production in planta. Thirty-seven strains from U.S. maize were assigned to groups 1 and 2 by DNA sequence analysis. In field tests, all strains were highly virulent on maize inbred B73 and four maize hybrids. In planta, 82% of group 1 strains and 25% of group 2 strains produced high levels (100-1500 microg/g) of moniliformin. All group 2 strains from more northern states produced little or no moniliformin (0-5 microg/g). These data indicate that moniliformin production is highly variable in F. subglutinans from U.S. maize and that production may not be required for the fungus to cause maize ear rot.  相似文献   
167.
A 4-year-old, late-term pregnant Himalayan queen was diagnosed with biventricular congestive heart failure characterized by pleural effusion and pulmonary edema. A cesarean section was performed, resulting in the birth of four live kittens, with one surviving to discharge. Congestive heart failure resolved rapidly following surgery. The queen remained asymptomatic for 9 years postoperatively. Volume expansion secondary to pregnancy was thought to result in cardiovascular volume overload and subsequent congestive heart failure.  相似文献   
168.
We propose a new process using a vapor phase bioreactor (VPB) to simultaneously (i) delignify sugar-cane bagasse, a residue of sugar production that can be recycled in paper industry, and (ii) produce laccase, an enzyme usable to bleach paper pulp. Ethanol vapor, used as laccase inducer, was blown up through a VPB packed with bagasse and inoculated with Pycnoporus cinnabarinusss3, a laccase-hyperproducing fungal strain. After 28 days, the laccase activity in the ethanol-treated bagasse was 80-fold higher (80 U g(ds)(-)(1)) and the bagasse delignification percentage was 12-fold (12%) higher than in the reference samples produced in the absence of ethanol, corresponding to a high overall pulp yield of 96.1%. In the presence of ethanol, the total soluble phenols amount was 2.5-fold (3 mg FA g(ds)(-)(1)) higher than that without ethanol. Six monomeric phenols were detected: p-coumaric (4-hydroxyphenyl-2-propenoic), ferulic (4-hydroxy-3-methoxyphenyl-2-propenoic), syringic (4-hydroxy-3,5-dimethoxybenzoic), vanillic (4-hydroxy-3-methoxybenzoic) and 4-hydroxybenzoic acids, and 2-methoxyhydroquinone. Higher concentrations of phenolic compounds were observed when ethanol vapor was added, confirming a more efficient bagasse delignification. After 28 days, the fungal-treated bagasse (with ethanol addition) was pulped and refined. For a freeness of 81 mL CSF, this processing required 50% less energy than with untreated bagasse (without inoculation and ethanol addition), which indicated a significant potential economy for the pulp and paper industry. Handsheets were made from pulp obtained after fungal-treated and untreated bagasse. Comparison of bagasse-pulp characteristics for freeness of 35 and 181 mL CSF showed an average increment by 35% for tensile index and breaking strength and length. VPB allowed a simultaneous production of laccase (90 U g(ds)(-)(1), after pressing of the bagasse) that improved the overall profitability of the process.  相似文献   
169.
OBJECTIVES: To examine the association between education level and food purchasing behaviour and the contribution of dietary knowledge to this relationship; and the association between household income and purchasing behaviour and the contribution made by subjective perceptions about the cost of healthy food.DESIGN AND SETTING: The study was conducted in Brisbane City (Australia) in 2000. The sample was selected using a stratified two-stage cluster design. Data were collected by face-to-face interview from residents of private dwellings (n=1003), and the response rate was 66.4%. Dietary knowledge was measured using a 20-item index that assessed general knowledge about food, nutrition, health and their interrelationships. Food-cost concern was measured using a three-item scale derived from principal components analysis (alpha=0.647). Food purchasing was measured using a 16-item index that reflected a household's purchase of grocery items that were consistent (or otherwise) with dietary guideline recommendations. Associations among the variables were analysed using linear regression with adjustment for age and sex.RESULTS: Significant associations were found between education, household income and food purchasing behaviour. Food shoppers with low levels of education, and those residing in low-income households, were least likely to purchase foods that were comparatively high in fibre and low in fat, salt and sugar. Socio-economic differences in dietary knowledge represented part of the pathway through which educational attainment exerts an influence on diet; and food purchasing differences by household income were related to diet in part via food-cost concern.CONCLUSIONS: Our findings suggest that socio-economic differences in food purchasing behaviour may contribute to the relationship between socio-economic position and food and nutrient intakes, and, by extension, to socio-economic health inequalities for diet-related disease. Further, socio-economic differences in dietary knowledge and concerns about the cost of healthy food play an important role in these relationships and hence should form the focus of future health promotion efforts directed at reducing health inequalities and encouraging the general population to improve their diets.  相似文献   
170.
CASE DESCRIPTION-A 12-week-old female English Springer Spaniel was evaluated for lethargy, vomiting, and pyrexia 1 week after treatment of patent ductus arteriosus (PDA) via coil occlusion. CLINICAL FINDINGS-Test results were consistent with septicemia, and the assumption was made that the PDA occlusion coils were infected. Radiography revealed partial migration of the coil mass into the pulmonary artery and signs of congestive heart failure. TREATMENT AND OUTCOME-After successful treatment of the septicemia and heart failure, surgical removal of the coils and resection of the PDA were undertaken. Although the coil that embolized to the pulmonary vasculature was left in place, the dog's clinical signs resolved. CLINICAL RELEVANCE-This case highlights the fact that as PDA coil occlusion devices become more widely used in dogs, practitioners must be prepared to treat implant infections aggressively, with both medical and surgical interventions if necessary.  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