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   651篇
  免费   16篇
  国内免费   3篇
林业   21篇
农学   14篇
基础科学   7篇
  50篇
综合类   148篇
农作物   8篇
水产渔业   70篇
畜牧兽医   249篇
园艺   3篇
植物保护   100篇
  2023年   7篇
  2022年   17篇
  2021年   19篇
  2020年   11篇
  2019年   8篇
  2018年   6篇
  2017年   9篇
  2016年   8篇
  2015年   9篇
  2014年   11篇
  2013年   23篇
  2012年   25篇
  2011年   18篇
  2010年   21篇
  2009年   27篇
  2008年   25篇
  2007年   30篇
  2006年   20篇
  2005年   12篇
  2004年   11篇
  2003年   7篇
  2002年   11篇
  2001年   7篇
  1999年   8篇
  1998年   13篇
  1997年   12篇
  1996年   20篇
  1995年   12篇
  1994年   11篇
  1993年   20篇
  1992年   12篇
  1991年   10篇
  1990年   12篇
  1989年   16篇
  1988年   8篇
  1987年   13篇
  1986年   7篇
  1985年   9篇
  1983年   6篇
  1982年   5篇
  1981年   11篇
  1980年   9篇
  1979年   8篇
  1978年   5篇
  1976年   6篇
  1970年   5篇
  1958年   6篇
  1954年   4篇
  1947年   4篇
  1945年   5篇
排序方式: 共有670条查询结果,搜索用时 31 毫秒
21.
A dorsal surgical approach to the perineal area and rectum was made on 10 healthy, adult dogs. The rectococcygeal muscle was incised and the levator ani and external sphincter muscles were separated to the level of the caudal rectal nerve. All dogs were clinically normal throughout a 3 week postoperative observation period.  相似文献   
22.
Five methods are described, which have proved to be useful in closed chest experimental and clinical cardiovascular research in small animals.  相似文献   
23.
The concentration and the heterogeneity of alpha-1-acid glycoprotein (alpha-1-AGP) and oxprenolol binding were determined in serum of healthy dogs and dogs with inflammatory disease. In inflammation, an increase in the mean alpha-1-AGP concentration from 0.47 to 2.85 g/l was accompanied by a reduction in the mean free oxprenolol fraction from 25% to 6%. alpha-1-AGP concentration and oxprenolol binding were inversely correlated. The heterogeneity of canine alpha-1-AGP remained essentially unchanged in dogs with inflammation and, in both these dogs and the controls, between five and seven forms with different isoelectric points and one single concanavalin A-reactive form were detected. It is concluded that in dogs, as in humans, oxprenolol binds to serum alpha-1-AGP. Changes in serum binding of oxprenolol during inflammation result from a change in the serum concentration of alpha-1-AGP rather than a change of molecular heterogeneity.  相似文献   
24.
25.
复方恩诺沙星可溶性粉对畜禽主要致病菌的体外抑菌效果   总被引:2,自引:1,他引:2  
采用纸片扩散法(K-B法)测定复方恩诺沙星可溶性粉对畜禽主要致病菌的敏感性,采用试管倍比稀释法测定复方恩诺沙星可溶性粉对畜禽主要致病菌的最小抑菌浓度(MIC)和最小杀菌浓度(MBC)。结果表明,病原性大肠埃希菌、绿脓杆菌、金黄色葡萄球菌、鸡巴氏杆菌、猪巴氏杆菌和链球菌对复方恩诺沙星可溶性粉敏感,复方恩诺沙星可溶性粉对畜禽主要致病菌的MIC为0.0279μg/mL~3.575μg/mL,MBC为0.055μg/mL~7.11μg/mL。  相似文献   
26.
AIMS: To determine the suitability of diets containing either approximately 85% fodder beet (Beta vulgaris L.) with barley straw or 65% fodder beet with pasture silage when fed to non-lactating dairy cows, by measuring intakes, digestibility, rumen function including microbial growth, and N excretion.

METHODS: Holstein-Friesian cows fitted with permanent rumen fistulae were fed either 65% fodder beet with pasture silage (Silage; n=8) or 85% fodder beet with barley (Hordeum vulgare L.) straw (Straw; n=8) in an indoor facility over a 9-day period, for measurement of intakes, digestibility, rumen function and urine production. The cows were adapted to the diets over 2 weeks before the indoor measurements. Feed was available for about 6 hours/day, as practiced commercially for wintering non-lactating cows.

RESULTS: Five cows fed the Straw diet had to be removed from the trial because of acute acidosis; four on Day 1 of the measurement period and one on Day 7. One cow allocated to the Silage diet refused to eat fodder beet bulbs and was also removed from the trial. Two cows fed the Silage diet were also treated for acidosis. DM intakes were lower with the Straw than Silage diets (6.4 (SE 0.4) vs. 8.3 (SE 0.5) kg/day) and organic matter (OM) digestibility was lower with the Straw than Silage diets (77 (SE 1) vs. 83 (SE 1) g/100g). The N content of the two diets was 1.14 and 1.75?g/100?g DM and there was a net loss of N by cows fed the Straw diet (?22.7 (SE 7) g/day). Rumen microbial N production was much lower in cows fed the Straw than the Silage diet (6.6 (SE 1.3) vs. 15.8 (SE 0.7) g microbial N/kg digestible OM intake). Concentrations of ammonia in rumen liquid collected on Days 5–6 were below detection limits (<0.1?mmol/L) in 36/48 (75%) samples collected from cows fed the Straw diet and in 27/48 (56%) cows fed the Silage diet. Mean urinary N excretion was lower in cows fed the Straw than the Silage diet (52.0 (SE 5.8) vs. 87.7 (SE 5.9) g/day).

CONCLUSION AND CLINICAL RELEVENCE: An over-wintering diet for dry cows comprising about 65% fodder beet with 35% pasture silage provided adequate nutrition, although there was some risk of acidosis. In contrast, the diet containing about 85% fodder beet with barley straw resulted in lower DM intakes, poor rumen function, negative N balance so that both nutrition and welfare were compromised.  相似文献   
27.
28.
29.
Abstract. The inland fishery in Sri Lanka (6–10°N; 79–82°E) is essentially a fishery confined to man-made lakes and is dominated by the introduced cichlid Sarotherodon mossambicus (Peters). Catch statistics of 20 such major reservoirs indicate that the yield of this species ranges from 64·0 to 918 kg per ha and accounts for between 56 and 99% of the total yield in individual reservoirs. The yield of S. mossambicus is closely related to the fishing pressure exerted. Catch/effort data from the individual reservoir fisheries when analysed collectively simulate changes in a single large fishery. In the fishery the relationship of yield to effort is described by the equation: Y = 4·OX – 53·8X ( r = 0·92; P < 0·001), where Y = yield in kg per ha per annum and X = number of craft-days per ha per annum, indicating that the reservoirs in Sri Lanka remain underfished. However, very high increases in fishing pressure in two reservoirs, for which data are available over a 5-year period, indicate that the increases have resulted in a significant decline in the catch per unit effort. The reasons for the success of the S. mossambicus fishery in individual reservoirs, and also simulation of features of a single large fishery in reservoirs, with widely different hydrological and limnological regimes, are discussed in qualitative terms. It is hypothesized that the abundance is determined by factors other than food availability. Fresh management strategies to optimize the fishery from the point of view of optimal fishing pressure permissible from the present analysis are suggested.  相似文献   
30.
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