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   1275篇
  免费   95篇
  国内免费   1篇
林业   57篇
农学   13篇
基础科学   13篇
  130篇
综合类   194篇
农作物   50篇
水产渔业   53篇
畜牧兽医   729篇
园艺   14篇
植物保护   118篇
  2019年   22篇
  2018年   13篇
  2017年   21篇
  2016年   18篇
  2015年   13篇
  2014年   13篇
  2013年   72篇
  2012年   35篇
  2011年   45篇
  2010年   30篇
  2009年   25篇
  2008年   36篇
  2007年   48篇
  2006年   33篇
  2005年   44篇
  2004年   41篇
  2003年   32篇
  2002年   43篇
  2001年   30篇
  2000年   47篇
  1999年   29篇
  1998年   24篇
  1997年   22篇
  1996年   18篇
  1995年   23篇
  1994年   15篇
  1993年   21篇
  1992年   28篇
  1991年   27篇
  1990年   29篇
  1989年   28篇
  1988年   24篇
  1987年   19篇
  1986年   13篇
  1985年   19篇
  1984年   14篇
  1983年   19篇
  1982年   16篇
  1981年   12篇
  1979年   22篇
  1978年   13篇
  1976年   12篇
  1975年   11篇
  1974年   11篇
  1973年   14篇
  1972年   16篇
  1971年   15篇
  1970年   10篇
  1967年   15篇
  1938年   10篇
排序方式: 共有1371条查询结果,搜索用时 62 毫秒
41.
Thirty-one Friesian calves in Morocco susceptible to tropical theileriosis were protected against a lethal sporozoite challenge by prior infection with lymphoblastoid cell lines infected and transformed in vitro by a Moroccan stock of Theileria annulata. The challenge infection of cryopreserved sporozoites killed all four susceptible control calves within 20 days. Four schizont-infected cell cultures at Passage 3 were inoculated at four different doses, 10(8), 10(6), 10(4) and 10(2), into pairs of calves. The recipient animals showed great variation in severity of disease symptoms, which did not show a linear correlation with the cell dose inoculated. The most severe disease symptoms were recorded, prior to challenge, in the 10(2) cell dose recipients; one animal died of acute theileriosis and another had to be treated. One of the four cell lines used was more virulent than the other three. Two years after the completion of this experiment, immunised animals have shown normal productivity traits.  相似文献   
42.
1. Yellow follicle numbers and production of defective egg shells were greater in the early part of the laying period in conventionally-reared turkeys photostimulated at 24 rather than 30 weeks of age. 2. The number of yellow follicles declined with age and were similar in both groups at 40 weeks of age. 3. At 55 weeks of age more birds photostimulated at 24 weeks were out of lay and birds in lay had fewer yellow follicles and more atresia compared with turkeys photostimulated at 30 weeks of age. 4. The numbers of white follicles in the 1 to less than 2 mm size were similar in the two groups at each age. The proportion of white follicles which were atretic was negatively related to the number of yellow follicles, particularly in follicles 5 to less than 8 mm diameter.  相似文献   
43.
44.
45.
46.
Particle track etching   总被引:1,自引:0,他引:1  
  相似文献   
47.
Calf bone marrow cells cultured in a semi-solid medium of 0.8% methyl cellulose produced colonies of granulocytic cells and macrophages by seven days. A prerequisite for colony growth was the presence of serum obtained from a calf three hours after intravenous injection of endotoxin. Three morphological types of colonies were seen but cell types within these types of colonies did not differ. Cultured cells were identified by morphological and cytochemical characteristics.

Optimum growth occurred when serum from endotoxin stimulated calves and fetal calf serum were present in a volumetric ratio of 7:3. Inhibition of colony growth occurred when endotoxin-stimulated serum was present at greater than optimum concentration. Normal calf serum, fetal calf serum, mouse L-cell conditioned medium and bovine urine did not stimulate significant colony growth when 8.0 x 104 marrow cells were cultured.

There was a linear relationhip between the number of marrow cells in the cultures and the number of colonies produced. Colony forming efficiency ranged from 13 to 59 colonies per 105 cells plated.

The behaviour of calf colony forming units in suspension culture was similar to that reported for mouse colony forming units.

  相似文献   
48.
49.
The effects of soil temperature and soil moisture content on the rate of degradation of propyzamide in five soils were examined under controlled laboratory conditions. Half-lives in soils incubated at field capacity varied from 23 to 42 days at 25°C and from 63 to 112 days at 15°C. The variation in half-life at 25°C and 50% of field capacity was from 56 to 94 days. When the laboratory data were used in conjunction with the relevant meteorological records and soil properties in a computer simulation program, predicted degradation curves for propyzamide in four of the soils in micro-plots were in close agreement with those observed. Use of the program to predict residues of propyzamide in the fifth soil at crop maturity in a series of field experiments concerned with continuity of lettuce production gave values fairly close to those observed when appropriate corrections were made for initial recoveries.  相似文献   
50.
OBJECTIVE: To determine clinical, radiographic, and scintigraphic abnormalities in and treatment and outcome of horses with trauma-induced osteomyelitis of the proximal aspect of the radius. DESIGN: Retrospective study. ANIMALS: 5 horses. PROCEDURE: Data collected from the medical records included signalment; history; horse use; degree of lameness; radiographic, ultrasonographic, and scintigraphic findings; treatment; and outcome. RESULTS: Duration of lameness prior to referral ranged from 14 to 60 days. Mean severity of lameness was grade 3 of 5, and all horses had a single limb affected. All horses had signs of pain during elbow joint manipulation and digital palpation over the lateral aspect of the proximal end of the radius. Radiographic lesions consisted of periosteal proliferation, osteolysis, and subchondral bone lysis. Scintigraphy in 3 horses revealed intense pharmaceutical uptake diffusely involving the proximal end of the radius. Two horses had sepsis of the elbow joint. All horses were treated with antimicrobials long-term; 1 horse was also treated by local perfusion of the radial medullary cavity through an indwelling cannulated screw. At follow-up, all horses had returned to their previous function. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that osteomyelitis of the proximal end of the radius can result from a traumatic injury to the antebrachium. Because lesions may be an extension of septic arthritis, a thorough examination of the wound area and elbow joint is recommended. Prolonged systemic antimicrobial treatment can result in a successful outcome.  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