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   988篇
  免费   88篇
林业   68篇
农学   32篇
基础科学   7篇
  248篇
综合类   42篇
农作物   41篇
水产渔业   90篇
畜牧兽医   468篇
园艺   10篇
植物保护   70篇
  2024年   2篇
  2023年   5篇
  2022年   12篇
  2021年   11篇
  2020年   8篇
  2019年   10篇
  2018年   50篇
  2017年   43篇
  2016年   43篇
  2015年   49篇
  2014年   33篇
  2013年   66篇
  2012年   80篇
  2011年   65篇
  2010年   47篇
  2009年   46篇
  2008年   59篇
  2007年   56篇
  2006年   48篇
  2005年   63篇
  2004年   44篇
  2003年   45篇
  2002年   29篇
  2001年   31篇
  2000年   25篇
  1999年   33篇
  1998年   10篇
  1997年   6篇
  1996年   11篇
  1995年   5篇
  1994年   5篇
  1993年   6篇
  1992年   8篇
  1991年   3篇
  1990年   4篇
  1989年   1篇
  1988年   7篇
  1987年   2篇
  1985年   2篇
  1984年   1篇
  1983年   1篇
  1936年   1篇
排序方式: 共有1076条查询结果,搜索用时 15 毫秒
991.
992.
Different insecticides have been tested for the control of the olive bark beetle, Phloeotribus scarabaeoides Bern. This scolytid can be managed at two points in its biological cycle: in pruned logs, where it excavates reproduction galleries, or in living trees, after emergence from the logs, where it digs feeding galleries. In mortality laboratory bioassays, the efficiency of organophosphorus insecticides has been ranked as follows: chlorpyrifos + dimethoate < formothion < methidathion. Formothion and methidathion, the two most efficient, were sprayed on olive logs together with a pyrethroid insecticide, deltamethrin, and a formulation which combined an organophosphorus (fenitrothion) and a pyrethroid (cypermethrin) insecticide. Deltamethrin inhibited the excavation of new reproduction galleries and induced a repellent effect on the olive pest. In contrast, none of the organophosphorus insecticides or the combination, fenitrothion + cypermethrin, were able to control the olive bark beetle. In olive trees, deltamethrin controlled this olive pest without showing the repellent effect observed for logs. Ethylene, a plant hormone, has been reported as an attractant for the olive bark beetle. The use of dispensers which released ethylene increased the number of P. scarabaeoides approaching the treated olive trees, thus favouring its use in a lure-and-trap control system.  相似文献   
993.
Chronic hypertrophic pyloric gastropathy in 14 dogs   总被引:1,自引:0,他引:1  
SUMMARY Ten mate and 4 female dogs with chronic hypertrophic pyloric gastropathy were seen at the Sydney University Veterinary Teaching Hospital in the period 1982–88. The most commonly affected breeds were the Shihtzu and Maltese. The mean age was 8.2 yr and the mean body weight 6.5 kg. The most common clinical signs were vomiting, weight loss, polydipsia and depression. Hypokalaemia was present in 11 of 12 dogs examined and hypochloraemia in 10 of 11 dogs examined. Five of the six dogs that had blood gases measured were found to have a metabolic alkalosis. Surgery was performed on 13 dogs; pyloromyotomy 7, pyloroplasty 4, gastroduodenostomy 2. There was a recurrence of symptoms in one pyloromyotomy dog, and fatal ulceration and perforation of the cardia occurred in one pyloroplasty case. The remaining 11 dogs had a mean known symptom-free survival time of 20 mo. This study confirms the preponderance of affected males, identifies electrolyte and blood gas disturbances as significant complications of chronic hypertrophic pyloric gastropathy, and suggests that relatively minor surgery (pyloromyotomy) may have a place in the treatment of a selected subgroup of cases.  相似文献   
994.
A simple method for multi-residue analysis of pesticides by low-pressure gas chromatography-tandem mass spectrometry (LP-GC-MS-MS) has been validated in compost samples. The pesticide residues were extracted from the lyophilised samples with organic solvent by stirring. No sample clean-up was required prior to the analysis. The method was applied to determine the fate of two organochlorine pesticides (lindane and endosulfan) and two organophosphates (malathion and chlorpyrifos-methyl) during the composting process in the reactor of a pilot plant. Malathion, chlorpyrifos-methyl and lindane residues almost fully disappeared after 8 days of maturation in the reactor, while endosulfan residues were only partially degraded. Alongside this, a study of natural disappearance of the pesticides was carried out in the laboratory and a characteristic time profile was traced for each pesticide class.  相似文献   
995.
996.
Ulcerative enteritis is found in a wide range of avian hosts but has not been described in psittacine birds. This case report describes ulcerative enteritis in four lories (two Trichoglossus sp. and two Eos sp.) that were found dead without any previous sign of disease. Macroscopically, all four birds showed good body condition. The only remarkable finding was a moderate dilatation of the small intestine with the presence of multiple yellow foci. Histologically, multiple ulcers extended into the submucosa and were filled with necrotic debris; bacteria and fibrin were observed in the intestinal mucosa. The liver and spleen exhibited a multifocal fibrinoid necrosis associated with a very moderate inflammatory reaction. Microbiological isolation revealed colonies of Clostridium colinum and Clostridium perfringens in the intestinal tract of the investigated birds.  相似文献   
997.
The pharmacokinetics of marbofloxacin was investigated after intravenous (IV) and intramuscular (IM) administration, both at a dose rate of 5 mg/kg BW, in six clinically healthy domestic ostriches. Plasma concentrations of marbofloxacin was determined by a HPLC/UV method. The high volume of distribution (3.22+/-0.98 L/kg) suggests good tissue penetration. Marbofloxacin presented a high clearance value (2.19+/-0.27 L/kgh), explaining the low AUC values (2.32+/-0.30 microgh/mL and 2.25+/-0.70 microgh/mL, after IV and IM administration, respectively) and a short half life and mean residence time (t(1/2 beta)=1.47+/-0.31 h and 1.96+/-0.35 h; MRT=1.46+/-0.02 h and 2.11+/-0.30 h, IV and IM, respectively). The absorption of marbofloxacin after IM administration was rapid and complete (C(max)=1.13+/-0.29 microg/mL; T(max)=0.36+/-0.071 h; MAT=0.66+/-0.22 h and F (%)=95.03+/-16.89).  相似文献   
998.
999.
In this work more than 600 sera obtained from three different sources (parous ewes and directed immunizations with whole blood or leucocytes) were tested for cytotoxic antilymphocyte antibodies. A high incidence of cytotoxic antibodies in pregnancy-stimulated animals was confirmed. For the sake of comparison, a comprehensive review of other studies in sheep and other species was performed. There are several different reasons that could explain the differences found between these studies, among them the time of sampling and the cytotoxic assay procedures. Moreover, antibodies were also found in non-pregnant females which may imply that pregnancy is not the only stimulus for antibody production and environmental factors, such as molecular mimicry between infectious agents and lymphocyte antigens, could be the reason for their appearance. In the case of alloimmunizations with leucocytes or whole blood the results were very close to those obtained in goats. Taking into account the Strength Index, the immunization sera were of higher quality. Our results support the methodology of Nesse and Larsen since one injection of whole blood of the lamb is an easy procedure that produces alloantisera with a high value for major histocompatibility complex Class I antigens typing.  相似文献   
1000.
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