全文获取类型
收费全文 | 235700篇 |
免费 | 14794篇 |
国内免费 | 648篇 |
专业分类
林业 | 23180篇 |
农学 | 13927篇 |
基础科学 | 2941篇 |
41524篇 | |
综合类 | 19300篇 |
农作物 | 16905篇 |
水产渔业 | 16363篇 |
畜牧兽医 | 87301篇 |
园艺 | 6255篇 |
植物保护 | 23446篇 |
出版年
2021年 | 2429篇 |
2020年 | 2851篇 |
2019年 | 3646篇 |
2018年 | 3917篇 |
2017年 | 4232篇 |
2016年 | 4727篇 |
2015年 | 4256篇 |
2014年 | 5639篇 |
2013年 | 16249篇 |
2012年 | 5753篇 |
2011年 | 7541篇 |
2010年 | 7131篇 |
2009年 | 7740篇 |
2008年 | 6893篇 |
2007年 | 5886篇 |
2006年 | 6605篇 |
2005年 | 5803篇 |
2004年 | 5711篇 |
2003年 | 5525篇 |
2002年 | 4866篇 |
2001年 | 5276篇 |
2000年 | 4919篇 |
1999年 | 4809篇 |
1998年 | 4076篇 |
1997年 | 4135篇 |
1996年 | 3879篇 |
1995年 | 4440篇 |
1994年 | 3821篇 |
1993年 | 3517篇 |
1992年 | 3929篇 |
1991年 | 4147篇 |
1990年 | 3743篇 |
1989年 | 3764篇 |
1988年 | 3337篇 |
1987年 | 3346篇 |
1986年 | 3299篇 |
1985年 | 3671篇 |
1984年 | 3446篇 |
1983年 | 3294篇 |
1982年 | 2760篇 |
1981年 | 2689篇 |
1980年 | 2690篇 |
1979年 | 2980篇 |
1978年 | 2706篇 |
1977年 | 2560篇 |
1976年 | 2410篇 |
1975年 | 2214篇 |
1974年 | 2353篇 |
1973年 | 2271篇 |
1972年 | 1994篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
981.
To assess respiratory function in dogs with tick paralysis, respiratory measurements were recorded on 14 dogs experimentally infested with Ixodes holocyclus. There was a progressive fall in respiratory rate with no change in tidal volume, which resulted in a significant fall in minute respiratory volume in the latter stages of the disease. The fall in respiratory rate was possibly central in origin and was accompanied by an increased alveolar-arterial oxygen tension difference, probably caused by pulmonary congestion and oedema. The "grunting" respiration seen in tick paralysis was due to closure of the vocal cords during expiration and could represent an attempt to re-expand collapsed parts of the lung. 相似文献
982.
983.
Thromboembolic meningoencephalitis (TEME) caused by Huemophilus somnus infection was diagnosed for the first time in New Zealand in an eight month old bull calf. Clinical signs included pyrexia, excessive salivation, recumbency, opisthotonus and rigidity of the front legs. Multiple red, malacic foci (1-10 mm in diameter) were visible grossly on the surface of the cerebrum and cerebellum, and were scattered throughout the brain parenchyma. Histologically these lesions consisted of focal haemorrhage, necrosis and neutrophilic infiltration. Fibrin thrombi and colonies of gram negative bacteria were present in many small blood vessels within necrotic foci. An organism with the morphological and biochemical characteristics of Haemophilus somnus was cultured from the brain. Although TEME is an important disease of feedlot cattle in North America and Europe it is relatively uncommon in cattle grazing pasture and is therefore unlikely to become a major problem in New Zealand. 相似文献
984.
985.
986.
987.
Outbreaks of infection due to a parapoxvirus were reported on eight New Zealand deer farms. Scabby lesions were seen variably on the muzzle, lips, face, ears and neck of red deer (Cervus elaphus) with morbidity rates reaching 100%. On three farms multifocal lesions were also present on the velvet. Deaths were reported on two properties where the lesions were extensive and secondary bacterial infections had occurred. On one of these farms multifactorial disease was suspected. Poxvirus particles were seen by negative contrast electron microscopy in scab material from all eight properties. Morphologically the deer virus resembled a parapoxvirus, but restriction endonuclease analysis showed its DNA fragment patterns were distinct from those of orf (contagious ecthyma) virus. 相似文献
988.
Clark RG Henderson HV Hoggard GK Ellison RS Young BJ 《New Zealand veterinary journal》1987,35(8):126-133
Blood samples from 433 periparturient recumbent cows submitted by veterinary practitioners to Ruakura Animal Health Laboratory during 1983 and 1984 were analysed and results related to whether cows recovered, died or were euthanased. Generally cows were sampled only once and the time varied from 15 minutes to 20 days after becoming recumbent. During 1983 serum calcium, magnesium, phosphorus, creatine phosphokinase (CK), aspartate amino transferase (AST), glutamate dehydrogenase (GDH), gamma glutamyl transferase (GGT) were analysed. In 1984 serum urea, creatinine, fibrinogen and haematological examination (haemoglobin, haematocrit, total and differential white cell counts) were added to the panel. Overall 39% of cows recovered, 30% died and 32% were destroyed. Precalving cows had 111% more deaths and 7% less survivors than postcalving recumbent cows (P<0.1). There was little difference (3%) in euthanasia prevalence. Tests that were most useful in predicting a lack of recovery were serum urea and muscle enzymes. Using these tests and duration of recumbency when sampled a model was produced to predict the probability of recovery from 254 cases. 相似文献
989.
McKenna PB 《New Zealand veterinary journal》1987,35(6):94-97
A new approach to the interpretation of faecal egg counts using a simple "formula", is described. It is suggested that adoption of this procedure may enable the likely level and frequency distribution of strongyle worm burdens (Nematodirus excluded) in young sheep flocks to be estimated. The potential relevance of this information to the diagnosis of gastrointestinal parasitism is discussed. 相似文献
990.
Gossett KA Root CR Cleghorn B Church GE Turk JR Turk MA 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》1987,16(4):97-101
Hookworm infected dogs had higher blood basophil counts than hookworm negative dogs. Dogs with occult heartworm infection (i.e., without microfilaremia) had higher blood neutrophil counts than heartworm negative dogs. The percentage of eosinophils in peripheral lymph nodes was higher in heartworm infected, microfilaremic dogs than in both occult infected dogs and heartworm negative dogs. Heartworm or intestinal parasitic infection had no other significant effects on hematologic parameters or peripheral lymph node cytology. 相似文献