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   1872篇
  免费   8篇
林业   17篇
农学   881篇
  90篇
综合类   318篇
农作物   20篇
水产渔业   7篇
畜牧兽医   509篇
园艺   1篇
植物保护   37篇
  2012年   77篇
  2011年   99篇
  2010年   11篇
  2009年   10篇
  2008年   84篇
  2007年   85篇
  2006年   148篇
  2005年   155篇
  2004年   192篇
  2003年   254篇
  2002年   244篇
  2001年   107篇
  2000年   63篇
  1999年   30篇
  1998年   27篇
  1997年   26篇
  1996年   19篇
  1995年   26篇
  1994年   34篇
  1993年   36篇
  1992年   9篇
  1991年   9篇
  1990年   7篇
  1989年   16篇
  1988年   3篇
  1987年   3篇
  1985年   4篇
  1984年   5篇
  1983年   3篇
  1981年   3篇
  1976年   3篇
  1970年   5篇
  1963年   3篇
  1959年   4篇
  1958年   4篇
  1957年   3篇
  1956年   2篇
  1955年   5篇
  1954年   7篇
  1953年   4篇
  1948年   4篇
  1945年   2篇
  1941年   2篇
  1931年   2篇
  1929年   2篇
  1928年   3篇
  1927年   2篇
  1924年   3篇
  1922年   2篇
  1921年   2篇
排序方式: 共有1880条查询结果,搜索用时 672 毫秒
31.
Lytic lesions occurring in conjunction with plasma cell sarcoma (multiple myeloma) have rarely been reported in cats.

A plasma cell sarcoma was diagnosed in a 13 year old castrated male Siamese cat with hind limb paresis resulting from osteolysis of the second lumbar vertebra. Serum electrophoresis showed a monoclonal gammopathy. A uniform population of plasma cells was found in and around the second lumbar vertebra and in the bone marrow of the femora, humeri, pelvis and the fifth lumbar vertebra. The neoplastic cells were identified as IgA and kappa chain specific by direct immunofluorescence.

  相似文献   
32.
33.
This prospective study evaluated transdermal amlodipine for the control of hypertension in six cats. Cats were treated with oral amlodipine until blood pressures decreased to <180 mm Hg. They were maintained on this dose for 7 days and then administered identical doses of transdermal amlodipine for 7 days. Oral amlodipine decreased pressure by a median of 73 mm Hg, which subsequently increased by 20 mm Hg after 7 days of transdermal amlodipine. Plasma concentrations of amlodipine were measured after oral and transdermal dosing. Additional studies are needed to determine dosing, pharmacokinetics, and efficacy.  相似文献   
34.
The repellent effects of the essential oil of Lavendula angustifolia on adults of Hyalomma marginatum rufipes was studied at concentrations of 5, 10 and 20% v/v. A suitable tick climbing bioassay based on the questing behaviour of ticks was used to test for repellency. High percentage repellency (range 70-100) was shown at all concentrations of the essential oil of L. angustifolia, although at 5% v/v it only persisted for the first 40 minutes compared with 120 minutes at other concentrations (10 and 20% v/v). The repellent strength of L. angustifolia compared well (P > 0.05) with that of DEET (N,N-diethyl-m-toluamide), a commercial reference repellent, for the 2-hour period of the study.  相似文献   
35.
36.
37.
BACKGROUND: Systemic hypertension is an important problem in older cats associated with kidney disease and hypokalaemia, suggesting that excessive activity of the renin-angiotensin-aldosterone system might contribute to the hypertensive state. Fluctuations in plasma renin activity and plasma aldosterone concentrations complicate the interpretation of these assays. OBJECTIVES: The aim of this study was to determine whether measurement of urinary aldosterone excretion in cats aided the investigation of hypertension. METHODS: Urine concentrations of free (ethyl acetate extract) and 18-glucuronidated aldosterone (acid hydrolysis before extraction) were measured by radioimmunoassay in normal, normotensive and hypertensive azotaemic cats (n=11 per group). Urine samples from 11 healthy human volunteers and eight normal dogs were also analysed for comparison. Urinary aldosterone concentration was corrected for the urinary creatinine concentration. RESULTS: Cats excreted 7.3 times less free aldosterone than human beings, and no free aldosterone was detected in dog urine. Acid hydrolysis led to large increases in aldosterone recovery from both human beings and dog but not feline urine. No significant effect of hypertension or azotaemia on feline urinary aldosterone concentration was found. CLINICAL SIGNIFICANCE: Measurement of aldosterone in feline urine using the available methodology has limited or no utility in investigating feline hypertension.  相似文献   
38.
39.
40.
有人报道玉米籽粒增产的平均36%都与环境改变有关。Wu等人证实,温带玉米的遗传改良是由其基因型对环境胁迫有较好耐性引起的;他们指出杂种优势可赋予胁迫耐性。Russell等人阐述了玉米产量改良与基因型耐高密度能力的关系。很多人报道了优  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