全文获取类型
收费全文 | 113220篇 |
免费 | 6108篇 |
国内免费 | 69篇 |
专业分类
林业 | 5571篇 |
农学 | 3809篇 |
基础科学 | 667篇 |
13535篇 | |
综合类 | 20247篇 |
农作物 | 4292篇 |
水产渔业 | 5619篇 |
畜牧兽医 | 56929篇 |
园艺 | 1383篇 |
植物保护 | 7345篇 |
出版年
2018年 | 1607篇 |
2017年 | 1735篇 |
2016年 | 1616篇 |
2015年 | 1417篇 |
2014年 | 1743篇 |
2013年 | 4109篇 |
2012年 | 3233篇 |
2011年 | 3791篇 |
2010年 | 2575篇 |
2009年 | 2678篇 |
2008年 | 3903篇 |
2007年 | 3640篇 |
2006年 | 3540篇 |
2005年 | 3249篇 |
2004年 | 3277篇 |
2003年 | 3202篇 |
2002年 | 3040篇 |
2001年 | 3539篇 |
2000年 | 3531篇 |
1999年 | 2856篇 |
1998年 | 1270篇 |
1997年 | 1188篇 |
1996年 | 1165篇 |
1995年 | 1296篇 |
1994年 | 1234篇 |
1993年 | 1163篇 |
1992年 | 2271篇 |
1991年 | 2276篇 |
1990年 | 2360篇 |
1989年 | 2254篇 |
1988年 | 2159篇 |
1987年 | 2067篇 |
1986年 | 2107篇 |
1985年 | 2084篇 |
1984年 | 1729篇 |
1983年 | 1569篇 |
1982年 | 992篇 |
1979年 | 1553篇 |
1978年 | 1255篇 |
1977年 | 1110篇 |
1976年 | 1083篇 |
1975年 | 1154篇 |
1974年 | 1375篇 |
1973年 | 1350篇 |
1972年 | 1391篇 |
1971年 | 1348篇 |
1970年 | 1259篇 |
1969年 | 1268篇 |
1967年 | 1098篇 |
1966年 | 991篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
The ultrastructure of sarcocysts of macro- and microscopic species of Sarcocystis was compared from naturally infected water buffalo from India. Grossly visible sarcocysts had walls consisting of cauliflower-like villar protrusions, typical of S. fusiformis. The sarcocyst wall of the microscopic species of Sarcocystis was 6.4 microns thick and consisted of tightly packed conical villar protrusions that were 9.6 microns long and 3.7 microns wide at the base. At approximately 3 microns above the base, the distal two-thirds of the villar protrusion became conical shaped and was bent laterally at an angle of 45 degrees to the sarcocyst surface. The granular layer beneath the villar protrusions was 0.9 microns thick. In S. levinei the granular layer was 1.9 microns thick, the villar protrusions were narrow and it had a highly undulating primary cyst wall. Whether the microscopic S. levinei-like sarcocysts of Indian and Malaysian water buffalo are distinct species of Sarcocystis will require further investigation. 相似文献
52.
A 3‐year‐old Burmese cat was presented with a history of nonresolving crusted and papular lesions of the face and prior treatment with prednisolone. Skin biopsies revealed typical pox lesions with hyperplasia and ulceration of the epidermis and eosinophilic cytoplasmic inclusion bodies in the epidermal cells. In the upper dermis there was prominent diffuse mast cell infiltration and mild neutrophilic and eosinophilic inflammation. Rare cytoplasmic inclusion bodies were also present in swollen endothelial cells of dermal venules, which showed no other degenerative changes. Histological diagnosis was confirmed by electron microscopic evidence of pox virus particles in inclusion bodies of epidermal cells. The lesions resolved within 6 weeks with systemic antibiotic therapy and supportive care. A 2‐year‐old domestic short‐haired cat was presented with multiple disseminated papular and ulcerative pox lesions with central eschar over the entire body. Histologically, large epidermal inclusion bodies (up to 6 μm in diameter) were present. Widespread haemorrhage and vascular wall necrosis was visible in the dermis and subcutis. Some subcutaneous vessels showed neutrophilic vasculitis. In addition to diffuse dermal neutrophilic and eosinophilic inflammation, a lymphohistiocytic panniculitis was also present. The cat died as a result of massive haemorrhage and lymphedema, despite supportive care. Funding: Self‐funded. 相似文献
53.
As anaerobic sampling and culture techniques improved, the documented prevalence of anaerobic bacteria in periodontal disease has increased. The anaerobic bacteria have become more well-known in humans and consequently in dogs, since this species is a major model in periodontal studies. A review of the literature related to anaerobic flora is described. 相似文献
54.
55.
56.
C. P. Verschueren P. J. Selman J. J. M. de Vijlder J. A. Mol 《Domestic animal endocrinology》1991,8(4):509-519
Canine thyroglobulin (cTg) has been isolated and purified. It has similar electrophoretic patterns as Tg from other mammalian species. The main fraction had a MW of 660,000, whereas also fractions of a MW of approximately 1,300,000 (dimer) and 330,000 (subunit) were present. The iodine content was 0.8 to 1.0 % (w/w). cTg did not cross-react with antibodies against human Tg to a degree that would allow the use of a radioimmunoassay for human Tg for the determination of cTg in serum or plasma. Therefore a polyclonal antiserum was raised against cTg and a homologous radioimmunoassay was developed, which was sensitive (0.4 μg/l) and specific (cross-reactivity in cTg assay of human Tg, goat Tg, T4, T3, and DIT < 0.01 %).
Plasma Tg levels in normal dogs of both sexes and aged 3–15 years amounted to 192 ± 73 μg/l (mean ± SD, n=30). There was no relation between plasma Tg and T4 levels. 相似文献
57.
J.A. Díez P. Hernaiz M.J. Muñoz A. de la Torre A. Vallejo 《Soil Use and Management》2004,20(4):444-450
Abstract. The repeated application of pig slurry to agricultural soils may result in an accumulation of salts and a risk of aquifer pollution due to nitrate leaching and salinization. Under Mediterranean conditions, a field experiment on a sandy loam soil (Typic Xerofluvent) was performed with maize (Zea mays) in 1998, 1999 and 2001 to study the effects of applying optimal (P1) and excessive rates (P3) of pig slurry on soil salinization, nitrate leaching and groundwater pollution. The rate of pig slurry was established considering the optimal N rate for maize in this soil (170, 162 and 176 kg N ha?1 for 1998, 1999 and 2001, respectively). Pig slurry treatments were compared to an optimal N rate supplied as urea (U) and a control treatment without N fertilizer (P0). The composition of the slurries showed great variability between years. Mean NO3? leaching losses from 1998 to 2001 were 329, 215, 173 and 78 kg N ha?1 for P3, P1, U and P0 treatments, respectively. The amount of total dissolved salts (TDS) added to the soil in slurry application between 1998 and 2001 was 2019 kg TDS ha?1 for the P1 treatment and 6058 kg TDS ha?1 for the P3 treatment. As a consequence, the electrical conductivity (EC) of the slurry‐treated soils was greater than that of the control soil. The EC correlated significantly with the sodium concentration of the soil solution. Over the entire experimental period, 2653, 2202 and 2110 kg Na ha?1 entered the aquifer from the P3, P1 and P0 treatments, respectively. The P3 treatment did not significantly increase grain production in 1999 and 2001 compared with that achieved with the optimal N rate treatment (P1). This behaviour shows the importance of establishing application guidelines for pig slurry that will reduce the risk of soil and groundwater pollution. 相似文献
58.
The fertility of male coypu sperm following seminal vesicle extirpation was investigated using the penetration test into the egg of Syrian golden hamster (Mesocricetus auratus). Ejaculates were obtained from five males by means of electro-ejaculation under halothane narcosis. The results of the zona-free hamster eggs (ZFHE) penetration test showed that the ejaculates of all the surgically treated coypu males were fertile and that ZFHE value fluctuated from 54 to 76.6%. The results obtained in experiments with natural mating revealed that the extirpation of male coypu seminal vesicles did not affect their fertility. In total 47 foetuses were found post mortem in ten coypu females covered by surgically treated males, which on average represented 4.7 foetuses per female. 相似文献
59.
60.