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   1235篇
  免费   79篇
林业   48篇
农学   36篇
基础科学   9篇
  159篇
综合类   128篇
农作物   37篇
水产渔业   93篇
畜牧兽医   737篇
园艺   19篇
植物保护   48篇
  2023年   17篇
  2022年   16篇
  2021年   41篇
  2020年   30篇
  2019年   36篇
  2018年   33篇
  2017年   24篇
  2016年   37篇
  2015年   29篇
  2014年   30篇
  2013年   62篇
  2012年   47篇
  2011年   75篇
  2010年   36篇
  2009年   39篇
  2008年   58篇
  2007年   66篇
  2006年   56篇
  2005年   60篇
  2004年   53篇
  2003年   45篇
  2002年   38篇
  2001年   21篇
  2000年   26篇
  1999年   12篇
  1998年   13篇
  1997年   10篇
  1996年   8篇
  1995年   8篇
  1993年   10篇
  1992年   12篇
  1991年   11篇
  1990年   16篇
  1989年   10篇
  1988年   16篇
  1987年   18篇
  1986年   15篇
  1985年   15篇
  1984年   10篇
  1983年   12篇
  1980年   8篇
  1979年   12篇
  1978年   16篇
  1977年   9篇
  1976年   8篇
  1975年   8篇
  1973年   14篇
  1970年   9篇
  1967年   6篇
  1966年   7篇
排序方式: 共有1314条查询结果,搜索用时 283 毫秒
121.
We investigated the extent of visitation of underground sites during late summer and autumn (‘swarming’) by bats. Bats were captured at eight cave, mine and tunnel sites in southern England over 6 years (1995-2000). A total of 3077 bats representing 11 of Britain's 16 species was caught. Myotis bats predominated in autumn. At some sites these are rarely seen during winter hibernation counts. Myotis nattereri and M. daubentonii were most common. However, species composition changed seasonally. At one site, M. brandtii dominated early in the season and at all sites peak activity of M. daubentonii was earlier than in M. nattereri. Relatively high numbers of internationally vulnerable species such as M. bechsteinii and Barbastella barbastellus were recorded. There was a strong male bias in captures of swarming species. Swarming probably has an important reproductive function, most males are reproductively active at this time and such sites may be important for outbreeding. Due to this and the large number of individuals and species concerned, the conservation of ‘swarming sites’ is vitally important. Clearly swarming sites merit special consideration in conservation management strategies for cave-dwelling bats.  相似文献   
122.
123.
Outer membrane-peptidoglycan complex from Brucella abortus was separated from cytoplasmic membrane and cytosol by either sucrose density gradient fractionation or differential (rate) centrifugation of surface labeled cells disrupted by sonication without the use of detergents. The outer membrane-peptidoglycan complex had a buoyant density of 1.22 gm/ml and contained 67 labeled SDS-soluble proteins when examined by SDS-PAGE. Included were four major bands exhibiting molecular masses of 88k, 40k, 35.7k and 26k daltons corresponding to previously described group 1, 2 and 3 outer membrane proteins. Lysozyme treatment of outer membrane-peptidoglycan complex increased its buoyant density to 1.25 gm/ml and released eight additional peptidoglycan-linked proteins.  相似文献   
124.
A foal born 3 weeks prematurely was treated for respiratory distress, using a combination of oxygen therapy and mechanical ventilatory assistance. Clinical response and arterial blood gas tensions were monitored regularly. Continuous positive-airway pressure and intermittent positive-pressure ventilation administered via a nasotracheal tube were effective in improving arterial oxygenation and ventilatory function.  相似文献   
125.
SUMMARY A 19-month-old pony gelding was presented with chronic renal failure, after deteriorating progressively during the preceding 3 months. There was pronounced azotaemia, hyponatraemia and hypochloraemia, but plasma calcium and phosphorus levels were normal. At autopsy both kidneys were small and nodular and were characterised by collapsed segments of cortex and medulla interspersed with areas of pale tissue. The latter showed glomerular immaturity associated with a range of degenerative processes involving the glomeruli and tubules. The condition bore many similarities to that of renal cortical dysplasia in other species.  相似文献   
126.
127.
Six healthy adult mares were given a single IV injection of trimethoprim (TMP)-sulfadiazine (SDZ) at a dosage rate of 2.5 mg of TMP/kg of body weight and 12.5 mg of SDZ/kg. Serum, synovial, peritoneal, and urine TMP-SDZ concentrations were measured serially over a 48-hour period. The highest measured mean concentrations of TMP and SDZ were found in the first (0.5 hour) sample of serum, synovial fluid, and peritoneal fluid. The mean peak concentrations of TMP and SDZ averaged 4.37 micrograms/ml and 21.81 micrograms/ml for serum, 2.95 micrograms/ml and 15.31 micrograms/ml for synovial fluid, and 3.88 micrograms/ml and 19.52 micrograms/ml for peritoneal fluid, respectively. Urine concentrations of the drugs were relatively high and peaked early. The elimination rate for TMP and SDZ averaged 0.41 and 0.26 hour-1, while the elimination half-life was 1.91 and 2.71 hours, respectively, and the volume of distribution averaged 0.59 and 0.52 L/kg, respectively.  相似文献   
128.
Two adult male labrador dogs had short clinical histories of congestive cardiac failure lasting only six weeks. Cardiac function deteriorated rapidly in both dogs, in spite of symptomatic treatment with cardiac glycoside, diuretic and p-adrenergic blocker. Necropsies revealed ascites and pulmonary congestion, but no macroscopic evidence of valvular or myocardial disease adequate to account for the cardiac dysfunction. Both dogs had extensive stenosis of extramural coronary arteries. This unusual vascular lesion comprised fibroelastic intimal thickening, discontinuity of internal elastic lamella and focal atrophy of medial smooth muscle. It seems likely that cardiac failure in these dogs was associated with myocardial underperfusion caused by extensive non-thrombotic, non-atherogenic stenosis of extramural coronary arteries.  相似文献   
129.
A four-year-old shire mare with haematuria, colic, terminal weight loss and an abdominal mass had a large unilateral renal adenocarcinoma. Clinical signs were monitored for 11 months. Increased serum copper concentrations were measured on two occasions. Hypercupraemia is discussed as a possible paraneoplastic change.  相似文献   
130.
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