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   824篇
  免费   15篇
林业   50篇
农学   33篇
基础科学   2篇
  107篇
综合类   41篇
农作物   25篇
水产渔业   81篇
畜牧兽医   448篇
园艺   8篇
植物保护   44篇
  2023年   5篇
  2022年   9篇
  2021年   19篇
  2020年   15篇
  2019年   11篇
  2018年   23篇
  2017年   11篇
  2016年   14篇
  2015年   15篇
  2014年   22篇
  2013年   70篇
  2012年   36篇
  2011年   30篇
  2010年   16篇
  2009年   22篇
  2008年   46篇
  2007年   49篇
  2006年   41篇
  2005年   39篇
  2004年   33篇
  2003年   38篇
  2002年   30篇
  2001年   32篇
  2000年   26篇
  1999年   21篇
  1998年   10篇
  1997年   6篇
  1996年   4篇
  1994年   6篇
  1992年   10篇
  1991年   7篇
  1990年   8篇
  1989年   9篇
  1988年   9篇
  1987年   12篇
  1986年   8篇
  1985年   11篇
  1984年   9篇
  1983年   5篇
  1982年   2篇
  1980年   2篇
  1979年   4篇
  1977年   5篇
  1976年   3篇
  1973年   6篇
  1972年   8篇
  1971年   2篇
  1970年   3篇
  1965年   6篇
  1964年   3篇
排序方式: 共有839条查询结果,搜索用时 31 毫秒
91.
The goal of this research was to identify mechanisms responsible for the spongy change induced in rats after repeated hexachlorophene (HCP) or cuprizone (CPZ) dosing. Rats were dosed with 35 mg/kg HCP for 5 days followed by drug withdrawal for 7 days suffered spongy changes to the white matter of the cerebrum, cerebellum, medulla oblongata, and spinal cord that were accompanied by degeneration of oligodendroglia. The severity of both lesions increased prominently on day 5; however, the spongy change decreased and degeneration of oligodendroglia reversed on day 12 (7 days after dosing ceased). On day 12, cerebral cortex oligodendroglia were stained strongly by anti-CNPase. Other rats were fed for 8 days with powdered chow containing 1% (w/w) CPZ, which was then withdrawn for 16 days. The rats exhibited the spongy change in the white matter of the cerebrum and cerebellum as well as oligodendroglial cell death from day 3. The severity of both lesions increased prominently on day 8. Cerebral cortex oligodendroglia were stained strongly by anti-CNPase on days 3 to 8 and decreased to the control levels by day 24 (16 days after dosing ceased). Electron microscopy revealed that oligodendroglia frequently displayed apoptotic morphology. These findings suggest that CNPase expression was induced in the course of restoration following HCP-induced insults to oligodendroglia and the myelin sheath, and in the course of demyelination by CPZ-induced damage to oligodendroglia. However, the role of CNPase on both courses is unclear.  相似文献   
92.
To establish a method to predict postpartum diseases using prepartum back fat thickness (BFT), the peripartum BFTs of 54 healthy multiparous cows before calving, which were diagnosed with postpartum displacement of the abomasum (DA), clinical ketosis or subclinical ketosis were compared with those of healthy cows from 8 weeks before the expected calving date to 8 weeks after calving. The peripartum BFTs of the cows with DA or clinical ketosis were significantly higher than those of healthy cows. The peripartum BFTs of the cows with subclinical ketosis were not significantly higher than those of the healthy cows.  相似文献   
93.
Tularemia is a zoonotic disease caused by Francisella tularensis. The distribution of the pathogen in Japan has not been studied well. In this study, seroprevalence of tularemia among wild black bears and hares in Japan was determined. Blood samples collected from 431 Japanese black bears (Ursus thibetanus japonicus) and 293 Japanese hares (Lepus brachurus) between 1998 and 2009 were examined for antibodies against F. tularensis by micro-agglutination test (MA) or enzyme-linked immunosorbent assay. By subsequent confirmatory tests using western blot (WB) and indirect immunofluorescence assay (IFA), eight sera from Japanese black bears were definitely shown to be seropositive. All of these eight bears were residents of the northeastern part of main-island of Japan, where human tularemia had been reported. On the other hand, no seropositive Japanese hares were found. These results suggest that Japanese black bears can serve as sentinel for tularemia surveillance and may help understand the distribution of F. tularensis throughout the country. This is the first report on detection of antibody to F. tularensis in black bears of Japan.  相似文献   
94.
Equine influenza A virus (EIV) of the H3N8 subtype is an important pathogen causing acute respiratory disease in horses. Peramivir is a selective inhibitor of the influenza virus neuraminidase (NA). The characteristics of peramivir are not only its capacity for parenteral administration, but also its strong affinity for NA and slow off-rate from the NA-peramivir complex, suggesting that it could lead to a prolonged inhibitory effect and thus allow a lower dosing frequency. The aims of this study were to evaluate the inhibitory efficacy of peramivir against the NA activities of EIV in vitro and the treatment efficacy of a single intravenous dose of peramivir in horses experimentally infected with EIV. Peramivir inhibited the activities of NA from the seven contemporary EIV strains in vitro, with 50% inhibitory concentrations ranging from 0.10 to 0.20nmol/L. Horses treated with a single IV dose of peramivir (3000mg/600mL/animal, 7.8-9.3mg/kg of bodyweight) showed significantly milder clinical signs (pyrexia, nasal discharge and cough) with a shorter duration than control horses injected with normal saline. Moreover, the mean duration of virus shedding for the horses treated with peramivir was significantly shorter than for the control horses. These findings suggested that a single IV administration of peramivir had good potential for the treatment of equine influenza, and may help to limit the spread of the disease in the horse population.  相似文献   
95.
Fifty avian (chicken) pathogenic Escherichia coli strains (APEC) isolated from individuals suffering from omphalitis, septicaemia and swollen head syndrome, and 30 strains isolated from healthy chickens were studied regarding their biological characteristics such as serogroups, haemolysin, colicin, cytotoxin, toxin and siderophore production, adhesion capacity to in vitro cultivated cells, and absorption of Congo red dye. Serotyping demonstrated that most of the omphalitis and normal strains were untypable, whereas most of the septicaemic strains were either untypable or rough. There was no prevalent serogroup among the pathogenic strains studied. The capacity for adhesion and invasion of in vitro cultured cells (HeLa, HEp-2, KPCC), as well as the agglutination of different types of red blood cells and the LD50 of each strain were also evaluated. No correlation was observed between the biological characteristics and pathogenicity, except that colicin was characteristically produced by swollen head syndrome E. coli strains. No correlation was found between adhesion or haemagglutination patterns and pathogenicity. Only six of the 50 strains revealed invasive capacity and the strain that best invaded the cell lines was the one with the lowest LD50.  相似文献   
96.
ABSTRACT

Understanding how maturity genes affect soybean yield formation will provide important information for crop management decisions. This study aimed to reveal how maturity genes E2 and E3 in the soybean cultivar ‘Enrei’ affect yields and yield formation in warm regions of Japan. ‘Enrei’ (e2e3) and three near-isogenic lines of ‘Enrei’ (e2E3, E2e3, and E2E3) were cultivated in 2016 and 2017 in Fukuyama, Japan (34°30′N, 133°23′E). Two sowing dates were set in each year (June sowing and July sowing). E2 extended the period from emergence to R1 and also the period from R1 to R7, whereas E3 extended only the period from emergence to R1. Interaction between E2 and E3 did not affect duration of the period from emergence to R1, but did affect the period from R1 to R7. Although seed yield did not differ between genotypes in the June sowings, the effects of E2 and E3 on seed yield in July sowing were both significant and interaction between E2 and E3 also observed. The total number of nodes increased in E3 genotypes in both sowing dates, especially in E2E3. Pod-set ratio was lower in E2 and E3 genotypes than in e2 and e3 genotypes in the June sowings, but did not differ between genotypes in the July sowings. The high yield of E2E3 genotypes in the July sowings was attributed to increased number of nodes and flower production while maintaining pod-set ratio. Appropriate choice of sowing date is suggested to be essential when using E3 genotypes.Abbreviations: HI: harvest index; NIL: near-isogenic line; RUE: radiation use efficiency; TDM: total above-ground dry matter; TRI: total solar radiation intercepted  相似文献   
97.
98.
99.
A five-month-old male beagle dog suddenly became moribund. Bloody fluid accumulated in the thoracic and abdominal cavities, and soft yellow flecks were floating in the thoracic fluid. The mediastinum and pericardium became dark reddish with villous thickening. Other parietal and pulmonary pleurae were rough, and the organs adhered to each other. Histologically, most mediastinal pleura formed papillary projections covered by a single layer of mesothelial cells. Many macrophages and neutrophils infiltrated the submesothelial connective tissue. At the mediastinum adjacent to the pericardium, cuboidal mesothelial cells proliferated solidly and formed a thick surface stratum. The flecks consisted of gram-negative filamentous or small bacillary (coccoid) bacteria. In the right posterior lobe of the lung, neutrophilic infiltration and a large encapsulated abscess including a bacterial colony were present. We diagnosed this case as “bacterial pleuritis with thickened mesothelial hyperplasia”. The cause of the pleuritis might be a chronic pleural infection spread via the lung abscess.  相似文献   
100.
This study aimed to develop a polymerase chain reaction (PCR)‐based sexing and effective semen collection methods for black‐headed and straw‐necked ibis species. However, most birds are not sexually dimorphic, that is, the sexes appear similar. Therefore, the gender should be determined before semen collection. DNA was extracted from the blood samples of 11 black‐headed and 4 straw‐necked ibis. The sex was determined after PCR amplification of the EE0.6 region of W‐chromosome. The PCR products were separated using gel electrophoresis. A single band indicated the presence of the EE0.6 region and that the individual was a female, while no band indicated that the individual was a male. Further, the single bands from seven specimens were amplified. Semen collection was performed by massage or a combination of massage with electro‐ejaculation and was attempted during all four seasons. The semen was successfully collected in March from male straw‐necked ibis using the massage method. Limited motility, viability and concentration of straw‐necked ibis sperm were observed. The sperm length was 180 μm and that of the nucleus was 30 μm with acrosome located at the tip of the nucleus. Thus, the PCR‐based sexing proved to be an accurate molecular sexing method for black‐headed and straw‐necked ibis. Furthermore, we successfully collected semen and observed the stained sperm nucleus and acrosome of the straw‐necked ibis sperm. We propose that the use of this PCR methodology can be applied as a routine method for sex determination and semen collection in ibis species for future ecological research. However, considering our limited success, further studies on semen collection method are required.  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