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   572篇
  免费   29篇
  国内免费   2篇
林业   32篇
农学   15篇
基础科学   3篇
  42篇
综合类   129篇
农作物   7篇
水产渔业   9篇
畜牧兽医   341篇
园艺   9篇
植物保护   16篇
  2020年   8篇
  2019年   5篇
  2018年   12篇
  2017年   10篇
  2016年   13篇
  2015年   12篇
  2014年   10篇
  2013年   36篇
  2012年   17篇
  2011年   17篇
  2010年   10篇
  2009年   15篇
  2008年   17篇
  2007年   13篇
  2006年   11篇
  2005年   19篇
  2004年   15篇
  2003年   14篇
  2002年   21篇
  2001年   23篇
  2000年   9篇
  1999年   10篇
  1998年   6篇
  1997年   5篇
  1996年   8篇
  1995年   5篇
  1993年   6篇
  1992年   10篇
  1991年   12篇
  1990年   11篇
  1989年   19篇
  1988年   7篇
  1987年   15篇
  1986年   9篇
  1985年   6篇
  1984年   6篇
  1983年   7篇
  1982年   5篇
  1979年   5篇
  1978年   6篇
  1977年   4篇
  1976年   7篇
  1974年   6篇
  1973年   8篇
  1972年   5篇
  1971年   7篇
  1970年   6篇
  1969年   4篇
  1895年   6篇
  1886年   5篇
排序方式: 共有603条查询结果,搜索用时 18 毫秒
61.
62.
Changes in composition during the maturation of Western Schley pecans [Carya illinoinensis(Wangenh.) K. Koch] grown in Australia were investigated. Pecans of different maturity levels were collected at monthly intervals between March and June in 1999 and 2000 and analyzed for the concentrations of moisture, total lipid, sucrose, raffinose, protein, and the minerals aluminum, boron, calcium, copper, iron, potassium, magnesium, manganese, sodium, phosphorus, sulfur, and zinc. Moisture, total lipid, and calcium contents changed significantly (p < 0.05) with harvest time and maturity, whereas the other components did not. Western Schley pecans grown in Australia should be harvested after the shuck has opened and it is either green or brown in color to maximize total lipid content and quality. This occurred after May 11 in 1999 and after May 17 in 2000.  相似文献   
63.
The influence of acidification on otters (Lutra lutra) was assessed in three regions of Scotland. A total of 72 stretches of 1000 m of riverbank were searched for all signs of otters on three occasions. Water chemistry was determined and habitat was assessed for its suitability to otters. A further series of water samples were collected after a period of very heavy rain in midwinter; conductivity and pH were measured and total Al was determined on a filtered, acidified sample. Otters were recorded at all sites. There were highly significant correlations between use by otters of stretches (measured in terms of marking intensity) and both pH and conductivity, with pH accounting for the greatest proportion of variation in otter signs in a stepwise multiple regression. The relation between otter signs and water quality was greatest in Galloway, the region with significantly more acid waters. There were significantly fewer signs of otters in stretches with minimum pH thought to be detrimental to fish populations for two regions, Galloway and Sutherland.  相似文献   
64.
Radioactivity was determined in samples of otter (Lutra lutra) faeces (scats) collected from various regions of Great Britain in 1986 and 1987, following the Chernobyl nuclear reactor accident, and compared with a sample of scats collected in 1985 from central Wales. Samples of scats were also collected from the seashore adjacent to the Dounreay nuclear power station, northern Scotland, and compared with a control site, 40 to 60 km distant. Samples collected in 1986 from central Wales, Galloway and northern Scotland all contained significantly higher amounts of radioactivity than the 1985 sample from central Wales, with Galloway (mean 13 000 Bq kg?1 dry weight) having significantly more radioactivity than other regions. A sample collected in central Wales in January 1987 had returned to the 1985 level of radioactivity, but a sample from Galloway in January 1987 remained high; this difference in response may be related to the acidic nature of Galloway rivers. No significant differences were found between samples collected from near Dounreay and the control site, though fallout from Chernobyl may have masked the effects of local discharges of radioactivity. The significance of the results to otter populations is discussed.  相似文献   
65.
The objective of this study was to determine the agreement between cardiac output measured by central (cranial vena cava) versus peripheral (cephalic vein) venous injection of lithium chloride for lithium-dilution cardiac output (LiDCO) determination in the dog. Five dogs (2 males, 3 females), anesthetized with halothane, were used. With each dog, 12 alternating central and peripheral LiDCO measurements were made, resulting in 10 paired comparisons. A total of 50 comparisons were obtained, the cardiac output measurements ranging from 1.11 to 2.76 L/min. The LiDCO measurement from the cephalic vein was similar to that obtained from the recommended central venous site: the difference between the central and cephalic vein determinations for all measurements was 0.098 ± 0.336 L/min (mean ± 2 standard deviations). Linear regression analysis demonstrated a slope of 1.050 (95% confidence interval 0.904 to 1.196) and a y intercept of 0.005 (r = 0.902). Therefore, although the central venous site is recommended by the manufacturer, the cephalic vein can be used instead in the dog, eliminating the need for central venous catheterization and thus reducing time and expense.  相似文献   
66.
67.
Nosocomial infection control programs of various types have been implemented in human hospitals since the staphylococcal pandemic of the 1950s. The prevalence of hospital infections is expected to increase in veterinary medicine with the advent of sophisticated invasive monitoring techniques, lengthier patient hospital stays, and the widespread use of antimicrobial agents. In order to monitor and control nosocomial infection outbreaks, the hospital staff must make strategic measures a priority. We propose the establishment of a nosocomial infection control committee, especially at the larger teaching and referral centers, to oversee such activities as hospital and personnel hygiene protocols, patient handling, antisepsis of surgical and critical care instruments, and surveillance. We have described a hospital pharmacy antibiotic restriction policy similar to those used with success in several human hospitals. It is apparent that the careless use of antibiotics adds significantly to the emergence of resistant hospital microflora and predisposes hospitalized patients to nosocomial infections. Judicious use of antibiotics not only helps to curtail such risks and lower health costs but encourages the clinician to fully evaluate his or her therapeutic rationale. As with any new program, continued staff education is the paramount requirement for its success.  相似文献   
68.
Two cases of bilateral atresia of the nasolacrimal orifice are described. The presenting sign was a persistent ocular discharge, clear in the one case and purulent in the other. Treatment by the creation of a fistula between the distal extremity of the blind ending duct and the nasal cavity was successful in both cases.  相似文献   
69.
70.
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