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   8326篇
  免费   393篇
  国内免费   68篇
林业   1319篇
农学   216篇
基础科学   65篇
  1355篇
综合类   769篇
农作物   250篇
水产渔业   382篇
畜牧兽医   3709篇
园艺   221篇
植物保护   501篇
  2023年   55篇
  2022年   81篇
  2021年   112篇
  2020年   136篇
  2019年   80篇
  2018年   229篇
  2017年   184篇
  2016年   216篇
  2015年   193篇
  2014年   166篇
  2013年   430篇
  2012年   399篇
  2011年   386篇
  2010年   243篇
  2009年   167篇
  2008年   322篇
  2007年   374篇
  2006年   330篇
  2005年   274篇
  2004年   268篇
  2003年   239篇
  2002年   229篇
  2001年   161篇
  2000年   156篇
  1999年   125篇
  1992年   95篇
  1991年   113篇
  1990年   129篇
  1989年   141篇
  1988年   118篇
  1987年   101篇
  1986年   104篇
  1985年   98篇
  1984年   94篇
  1983年   79篇
  1982年   50篇
  1979年   102篇
  1978年   74篇
  1977年   65篇
  1976年   51篇
  1975年   70篇
  1974年   91篇
  1973年   96篇
  1972年   73篇
  1971年   84篇
  1970年   78篇
  1969年   86篇
  1968年   68篇
  1967年   65篇
  1965年   56篇
排序方式: 共有8787条查询结果,搜索用时 15 毫秒
131.
The use of live animals for educational purposes is an old practice that is still employed in teaching and research institutions. However, there are several objections to this practice, whether for ethical or humanitarian reasons. Surgical techniques teaching using anatomical pieces and/or preserved cadavers promotes greater learning efficiency, provides exercise repetition and increases the confidence and satisfaction of the students when compared to the use of live animals. The current work aimed to analyse the feasibility of using fresh swine urinary bladder and small intestines (jejunum), obtained from slaughterhouses, fixed in 99.8% ethyl alcohol (EA) and preserved in sodium chloride hypersaturated solution (SCHS) at 30%, for 7, 14 and 21 days, as an alternative method for surgical skills training (SST). Swine viscera, fixed in EA and preserved in SCHS, presented a realistic appearance, absence of odour and maintained the viable morphological characteristics during the performance of the operative techniques. Preservation solutions had low cost, were easy to acquire and did not offers risks to human health. Therefore, urinary bladders and small intestines fixed in 99.8% EA for 30 days and maintained in 30% SCHS at different periods were demonstrated as a good viable option as a preservation method for surgical skills training.  相似文献   
132.
133.
134.
Between 2000 and 2004 a disease occurred in an aviary in Germany affecting various bird species belonging to the order Passeriformes including Collared Grosbeaks (Mycerobas affinis), Eurasian Bullfinches (Pyrrhula pyrrhula griseiventris), Brown Bullfinches (Pyrrhula nipalensis), Grey-headed bullfinches (Pyrrhula erythaca) and Yellow-bellied Tits (Periparus venustulus).The major clinical signs included increased mortality of fledglings and young birds, as well as feather disorders and feather loss in adult birds. In addition, adult Eurasian Bullfinches showed in one year a disease course, in which the major symptom was inflammation of the skin beginning on the basis of the beak and spreading over the head occurring a few days before death. Bacteriological and parasitological investigations did not reveal any consistent findings. Using a newly developed polymerase chain reaction protocol, DNA of the recently discovered finch polyomavirus (FPyV) was demonstrated in several affected birds. Because of the consistent detection of FPyV-DNA and the similarity of the symptoms with those observed during infection with the closely related avian polyomavirus in other bird species, an etiological role of FPyV in the observed disease is assumed.  相似文献   
135.
OBJECTIVE: To describe the clinical symptoms of 10 cases of superficial nonhealing corneal ulcers in horses and to evaluate the results of grid keratotomy in these patients. DESIGN: Retrospective study. ANIMALS: Ten horses with superficial nonhealing corneal ulceration in one eye. PROCEDURE: The signalment, history and clinical symptoms are reported of 10 patients with superficial nonhealing corneal ulcers during the period from August 2003 to February 2005. Grid keratotomy was performed in all cases. In addition, the surgical procedure of grid keratotomy and response to therapy are described. RESULTS: Horses generally responded well to grid keratotomy (eight cases healed after one grid keratotomy and one horse healed after a second grid keratotomy; one case was not available for follow-up). Only 2/10 had discomfort after treatment and only 2/9 had some degree of scarring after treatment. The healing time, which was known in seven cases, averaged 8.4 days (+/- SD 4). CONCLUSIONS AND CLINICAL RELEVANCE: Grid keratotomy is an appropriate option for treatment of superficial nonhealing corneal ulcers in horses. The procedure is simple to perform. It generally induces a rapid and uncomplicated healing of the cornea. Only in a limited number of cases does a small amount of scarring occur.  相似文献   
136.
We aimed to investigate the ratio of accompanying diseases in cows suffering from clinical hypocalcaemia and their influence on cure rate. In five veterinary practices in different regions of Germany, all recumbent cows around parturition were included in the study for a period of 1 year. After recording the case history a clinical examination was done and a serum sample was taken to measure the concentrations of calcium and phosphorus magnesium, beta-hydroxybutyrate, total bilirubin, cholesterol, urea, and the activities of ASAT, CK, and GLDH. Only cows with hypocalcaemia entered the statistical analysis. Hypocalcaemia was the major cause of recumbency in cows of the second lactation or elder. Muscle damage was the second frequent diagnose in recumbent cows and the major concomitant disease in hypocalcaemic cows. The overall cure rate was between 89.4% and 94.8%. Calcium and phosphorus concentrations did not have an influence on cure rate. Non-cured cows had higher serum activities of CK (p<0.043) and ASAT (p<0.006). Nevertheless, the activities of CK and ASAT were no good predictors of treatment failure because of their low specificity and the high cure rate of the cows in the five practices.  相似文献   
137.
Paratuberculosis (Johne's disease) is one of the most important diseases in ruminants today. Its contribution is worldwide and the disease is causing severe financial losses among cattle producers in some countries [Hasanova, L., Pavlik, I., 2006. Economic impact of paratuberculosis in dairy cattle herds: a review. Vet. Med.-Czech. 51, 193–211]. Paratuberculosis is untreatable; diagnosis limited to the early stages of the infection and control of the disease is difficult. The prevalence of serologically positive Austrian cattle farms rose significantly to 19.0% during the past years [Baumgartner, W., Damoser, J., Khol, J.L., 2005. Comparison of two studies concerning the prevalence of bovine paratuberculosis (Johne's disease) in Austrian cattle in the years 1995–1997 and 2002/2003 (Article in German with extended English summary). Vet. Med. Austria/Wien. Tierärztl. Mschr. 92, 274–277]. Based on these findings clinical paratuberculosis in ruminants was declared a notifiable disease in Austria in April 2006.

A survey of the current situation in Austria, the most important parts of the new compulsory measures and their practical implementation and impacts are presented in this short communication.  相似文献   

138.
Contagious bovine pleuropneumonia (CBPP), caused by Mycoplasma mycoides var. mycoides small colony (MmmSC), is one of the most important diseases of cattle in Africa. The role of innate or acquired cell mediated and humoral immunity in conferring protection against MmmSC infection has not yet been elucidated. On the other hand, the pathological lesions caused by the aetiological agent have been considered indicative of an immunopathological process. In this study ten na?ve cattle were exposed to in-contact infection with animals infected by intubation with a strain of MmmSC. Clinical signs, antibody response, IFNgamma release and pathological changes at necropsy were analysed and compared with the events following in-contact infection of an equal number of animals kept under daily treatment with cyclosporine for the entire observation period of 84 days. Cyclosporine is a suppressor of the immune response related to the T-cell system. Under the conditions of the experiment, cyclosporine appeared to condition the pathogenesis of CBPP by delaying the events that follow infection, bringing further support to the possibility that the immune response may have an impact on the disease outcome.  相似文献   
139.
140.
Journal of Plant Diseases and Protection - The root-knot nematodes (Meloidogyne spp.) are significant pathogens that affect the yield and fruit quality in pepper cultivars (Capsicum spp.)....  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