全文获取类型
收费全文 | 222787篇 |
免费 | 12237篇 |
国内免费 | 153篇 |
专业分类
林业 | 9002篇 |
农学 | 7065篇 |
基础科学 | 1371篇 |
27546篇 | |
综合类 | 40018篇 |
农作物 | 8923篇 |
水产渔业 | 11045篇 |
畜牧兽医 | 112665篇 |
园艺 | 3023篇 |
植物保护 | 14519篇 |
出版年
2019年 | 2110篇 |
2018年 | 3122篇 |
2017年 | 3496篇 |
2016年 | 3190篇 |
2015年 | 2759篇 |
2014年 | 3395篇 |
2013年 | 8867篇 |
2012年 | 6380篇 |
2011年 | 7778篇 |
2010年 | 5097篇 |
2009年 | 5146篇 |
2008年 | 7563篇 |
2007年 | 7203篇 |
2006年 | 6845篇 |
2005年 | 6374篇 |
2004年 | 6076篇 |
2003年 | 6142篇 |
2002年 | 5695篇 |
2001年 | 6729篇 |
2000年 | 6676篇 |
1999年 | 5370篇 |
1998年 | 2399篇 |
1997年 | 2291篇 |
1996年 | 2100篇 |
1995年 | 2510篇 |
1994年 | 2251篇 |
1993年 | 2171篇 |
1992年 | 4415篇 |
1991年 | 4640篇 |
1990年 | 4427篇 |
1989年 | 4470篇 |
1988年 | 4065篇 |
1987年 | 4154篇 |
1986年 | 4309篇 |
1985年 | 4157篇 |
1984年 | 3402篇 |
1983年 | 3053篇 |
1982年 | 2136篇 |
1979年 | 3114篇 |
1978年 | 2532篇 |
1977年 | 2188篇 |
1976年 | 2209篇 |
1975年 | 2323篇 |
1974年 | 2769篇 |
1973年 | 2763篇 |
1972年 | 2613篇 |
1971年 | 2467篇 |
1970年 | 2375篇 |
1969年 | 2330篇 |
1967年 | 2034篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
991.
McKenna PB 《New Zealand veterinary journal》1989,37(4):146-147
The persistent anthelmintic effect of ivermectin as a topical treatment at 500 microg/kg was evaluated against induced infections of Ostertagia ostertagi, Trichostrongylus axei and Dictyocaulus vivparus in calves. The results showed a highly significant (P<0.001) anthelmintic activity for at least 14 days against O. ostertagi and T.axei (>99 per cent efficacies) and for at least 28 days (98 per cent efficacy) against D. viviparus. 相似文献
992.
A survey of anthelmintic resistance on ten goat farms was carried out. The criterion for resistance was a faecal egg count reduction (FECR) of <90 percent based on arithmetic means of 11 to 19 goats per group. It was found that nine of the ten farms harboured nematodes resistant to oxfendazole when used at 5mg/kg although on two of these, the FECR's were 89.2 percent and 89.8 percent. Post treatment larval cultures indicated Haemonchus, Ostertagia and Trichostrongylus were the resistant genera involved. On none of the ten farms was resistance to oral ivermectin at 0.2mg/kg detected. 相似文献
993.
1. The effects of feeding two fats with different degrees of saturation on skin tearing, carcase quality and body fat composition were examined in male and female chickens.
2. No differences in growth or efficiency of food utilisation were apparent on feeding the more saturated fat. Skin tearing was slightly reduced and carcase quality slightly improved on feeding the more saturated fat for 28 d.
3. Decreases in linoleic acid content in intra‐abdominal fat were apparent after 14 d feeding the diet containing saturated fat. These decreases were greater after feeding the saturated fat for 28 d. 相似文献
994.
S A Robertson 《Veterinary Clinics of North America: Small Animal Practice》1989,19(2):289-306
The body regulates pH closely to maintain homeostasis. The pH of blood can be represented by the Henderson-Hasselbalch equation: pH = pK + log [HCO3-]/PCO2 Thus, pH is a function of the ratio between bicarbonate ion concentration [HCO3-] and carbon dioxide tension (PCO2). There are four simple acid base disorders: (1) Metabolic acidosis, (2) respiratory acidosis, (3) metabolic alkalosis, and (4) respiratory alkalosis. Metabolic acidosis is the most common disorder encountered in clinical practice. The respiratory contribution to a change in pH can be determined by measuring PCO2 and the metabolic component by measuring the base excess. Unless it is desirable to know the oxygenation status of a patient, venous blood samples will usually be sufficient. Metabolic acidosis can result from an increase of acid in the body or by excess loss of bicarbonate. Measurement of the "anion-gap" [(Na+ + K+) - (Cl- + HCO3-)], may help to diagnose the cause of the metabolic acidosis. Treatment of all acid-base disorders must be aimed at diagnosis and correction of the underlying disease process. Specific treatment may be required when changes in pH are severe (pH less than 7.2 or pH greater than 7.6). Treatment of severe metabolic acidosis requires the use of sodium bicarbonate, but blood pH and gases should be monitored closely to avoid an "overshoot" alkalosis. Changes in pH may be accompanied by alterations in plasma potassium concentrations, and it is recommended that plasma potassium be monitored closely during treatment of acid-base disturbances. 相似文献
995.
The paper describes pathomorphological findings in two dogs and one cat with the intention to clarify whether these animals died by drowning. The investigations are supplemented by experimental results of water instillation into the lung to induce signs of emphysema aquosum post mortem. Additionally, histopathology of the skin lesions due to water exposition after death are demonstrated by systematic investigations of four different localizations for 10 days. Critical evaluation of the results and literature references in human forensic pathology indicate that post mortem findings as described in this paper, especially those of the so called "drowning lung" can be attributed to death by drowning. 相似文献
996.
An osteodystrophy with features of both rickets and fibrous osteodystrophy was diagnosed in growing pigs housed indoors and fed on a diet deficient in vitamin D. Affected pigs were severely lame and preferred to remain recumbent. At necropsy, the long bones had reduced breaking strength and in one five-month-old pig the articular surfaces of both proximal humeri were indented due to collapse of subchondral bone. Microscopic changes in the bones included prominent osteoclastic activity in the proximal metaphyses, variable myelofibrosis, trabecular microfractures, and focal thickening of the hypertrophic zone in some growth plates. Treatment consisted of an injection of Vitamin D3, addition of dicalcium phosphate to the diet for 18 days and long-term supplementation of the diet with fat-soluble vitamins. This is the first report of an osteodystrophic disease in pigs in New Zealand. 相似文献
997.
998.
999.
Blood platelets and bone marrow megakaryocytes from a dog with essential thrombocythemia were analyzed by transmission electron microscopy and compared with those of control dogs. Platelets varied in size and shape and contained enlarged and dilated open canalicular systems. Megakaryocytes were dysmorphic and had evidence of abnormal maturation, with large numbers of megakaryoblasts containing alpha granules and poorly organized and reduplicated demarcation membranes. The fewer, more mature megakaryocytes lacked normal cytoplasmic organization. Most notable was the absence of well-demarcated "platelet fields," due to the excessive and disorderly array of demarcation membranes. 相似文献
1000.