全文获取类型
收费全文 | 567篇 |
免费 | 32篇 |
国内免费 | 14篇 |
专业分类
林业 | 22篇 |
农学 | 15篇 |
基础科学 | 2篇 |
50篇 | |
综合类 | 183篇 |
农作物 | 24篇 |
水产渔业 | 26篇 |
畜牧兽医 | 265篇 |
园艺 | 12篇 |
植物保护 | 14篇 |
出版年
2024年 | 4篇 |
2023年 | 8篇 |
2022年 | 6篇 |
2021年 | 10篇 |
2020年 | 7篇 |
2019年 | 14篇 |
2018年 | 4篇 |
2017年 | 15篇 |
2016年 | 19篇 |
2015年 | 20篇 |
2014年 | 19篇 |
2013年 | 22篇 |
2012年 | 25篇 |
2011年 | 33篇 |
2010年 | 28篇 |
2009年 | 18篇 |
2008年 | 20篇 |
2007年 | 25篇 |
2006年 | 25篇 |
2005年 | 26篇 |
2004年 | 17篇 |
2003年 | 23篇 |
2002年 | 16篇 |
2001年 | 9篇 |
2000年 | 11篇 |
1999年 | 8篇 |
1998年 | 9篇 |
1997年 | 8篇 |
1996年 | 13篇 |
1994年 | 5篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 10篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1981年 | 3篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1971年 | 3篇 |
1970年 | 3篇 |
1943年 | 6篇 |
1902年 | 4篇 |
1888年 | 3篇 |
1887年 | 4篇 |
1886年 | 5篇 |
排序方式: 共有613条查询结果,搜索用时 31 毫秒
1.
2.
3.
4.
Chronic obstructive pulmonary disease: Usefulness of clinical signs, bronchoalveolar lavage, and lung biopsy as diagnostic and prognostic aids 总被引:2,自引:0,他引:2
下载免费PDF全文
![点击此处可从《The Canadian veterinary journal. La revue veterinaire canadienne》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Naylor JM Clark EG Clayton HM 《The Canadian veterinary journal. La revue veterinaire canadienne》1992,33(9):591-598
We examined 18 horses with clinical signs of chronic obstructive pulmonary disease (COPD) using physical examination, cytological and bacteriological evaluation of bronchoalveolar fluid, and percutaneous lung biopsy. In 16 cases, histological examination of lung tissue confirmed the diagnosis of COPD. Two horses were excluded: one had uncomplicated bacterial pneumonia and in the other a satisfactory lung biopsy could not be obtained. In horses with COPD, the most common historical complaint was coughing, which was reported in 88%. The most frequently detected abnormal finding on physical examination was abnormal lung sounds; these were detected in 69% of horses at rest and in 88% of horses breathing deeply into a bag. A novel finding was that 29% of horses had lung sounds that were quieter than would be expected for the degree of respiratory effort. Horses with COPD had increased percentages of neutrophils and decreased percentages of lymphocytes and macrophages in their bronchoalveolar lavage fluid. Bronchiolar neutrophil infiltration and peribronchiolar mast cell accumulation in lung biopsy tissue had the highest correlation with clinical condition. The severity of pathological changes in biopsies of lung did not predict whether the horse would die in the two to four year follow-up period. Horses that died in the follow-up period were more severely affected clinically at initial presentation than horses that were alive at the end of the follow-up period. 相似文献
5.
卵泡从原始卵泡发育为成熟卵泡,直至排卵、黄体发育等过程都受到精密的调控,产生大量的优势卵泡是绵羊产多羔及实现快速扩繁的关键因素。研究发现,相关信号通路和转录因子通过影响绵羊卵泡中卵母细胞、颗粒细胞的生长,进而调控卵泡的发育成熟,对这些信号通路进行深入了解,有助于探索卵泡发育的调控机制,早日实现绵羊高效繁育。Notch是卵泡发育过程中发挥重要作用的高度保守信号通路,PI3K/AKT/mTOR信号通路各成员都是广泛存在于细胞内的信号转导分子,在卵泡发育早期发挥了主要作用,还有间隙连接(gap junction,GJ)和跨带突触(transzonal projections,TZPs)等物理连接方式,在细胞间的交流通讯起到重要作用。作者详细介绍了Notch信号通路、PI3K/AKT/mTOR信号通路、间隙连接及跨带突触的结构功能在绵羊卵泡发育中的调控作用,为进一步探明绵羊卵泡发育的调控机制提供参考。 相似文献
6.
7.
Joo Carlos de Moraes S Lucien Sguy Florent Tivet Rattan Lal Serge Bouzinac Paulo Rogrio Borszowskei Clever Briedis Josiane Burkner dos Santos Daiani da Cruz Hartman Clayton Giani Bertoloni Jadir Rosa Theodor Friedrich 《Land Degradation \u0026amp; Development》2015,26(6):531-543
The continuous use of plowing for grain production has been the principal cause of soil degradation. This project was formulated on the hypothesis that the intensification of cropping systems by increasing biomass‐C input and its biodiversity under no‐till (NT) drives soil restoration of degraded agro‐ecosystem. The present study conducted at subtropical [Ponta Grossa (PG) site] and tropical regions [Lucas do Rio Verde, MT (LRV) site] in Brazil aimed to (i) assess the impact of the continuous plow‐based conventional tillage (CT) on soil organic carbon (SOC) stock vis‐à‐vis native vegetation (NV) as baseline; (ii) compare SOC balance among CT, NT cropping systems, and NV; and (iii) evaluate the redistribution of SOC stock in soil profile in relation to soil resilience. The continuous CT decreased the SOC stock by 0·58 and 0·67 Mg C ha−1 y−1 in the 0‐ to 20‐cm depth at the PG and LRV sites, respectively, and the rate of SOC sequestration was 0·59 for the PG site and ranged from 0·48 to 1·30 Mg C ha−1 y−1 for the LRV site. The fraction of C input by crop residues converted into SOC stock was ~14·2% at the PG site and ~20·5% at the LRV site. The SOC resilience index ranged from 0·29 to 0·79, and it increased with the increase in the C input among the NT systems and the SOC sequestration rates at the LRV site. These data support the hypothesis that NT cropping systems with high C input have a large potential to reverse the process of soil degradation and SOC decline. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
8.
Kelling CL Hunsaker BD Steffen DJ Topliff CL Eskridge KM 《American journal of veterinary research》2007,68(7):788-796
OBJECTIVE: To evaluate protection resulting from use of a modified-live noncytopathic bovine viral diarrhea virus (BVDV) type 1 vaccine against systemic infection and clinical disease in calves challenged with type 2 BVDV. ANIMALS: 10 calves, 5 to 7 months of age. PROCEDURES: Calves were allocated (n = 5/group) to be nonvaccinated or vaccinated SC on day 0 with BVDV 1 (WRL strain). Calves in both groups were challenged intranasally with BVDV type 2 isolate 890 on day 21. Rectal temperatures and clinical signs of disease were recorded daily, and total and differential WBC and platelet counts were performed. Histologic examinations and immunohistochemical analyses to detect lesions and distribution of viral antigens, respectively, were performed. RESULTS: After challenge exposure to BVDV type 2, nonvaccinated calves developed high rectal temperatures, increased respiratory rates, viremia, leukopenia, lymphopenia, and infection of the thymus. Vaccinated calves did not develop high rectal temperatures or clinical signs of respiratory tract disease. Vaccinated calves appeared to be protected against systemic replication of virus in that they did not develop leukopenia, lymphopenia, viremia, or infection of target organs, and infectious virus was not detected in peripheral blood mononuclear cells or the thymus. CONCLUSIONS AND CLINICAL RELEVANCE: The modified-live BVDV type 1 vaccine protected against systemic infection and disease after experimental challenge exposure with BVDV type 2. The vaccine protected calves against infection and viremia and prevented infection of target lymphoid cells. 相似文献
9.
REASONS FOR PERFORMING STUDY: Previous studies have suggested that temporomandibular joint (TMJ) kinematics depend on the type of food being masticated, but accurate measurements of TMJ motion in horses chewing different feeds have not been published. HYPOTHESIS: The temporomandibular joint has a larger range of motion when horses chew hay compared to pellets. METHODS: An optical motion capture system was used to track skin markers on the skull and mandible of 7 horses as they chewed hay and pellets. A virtual marker was created on the midline between the mandibles at the level of the 4th premolar teeth to represent the overall motion of the mandible relative to the skull during the chewing cycle. RESULTS: Frequency of the chewing cycles was lower for hay than for pellets. Excursions of the virtual mandibular marker were significantly larger in all 3 directions when chewing hay compared to pellets. The mean velocity of the virtual mandibular marker during the chewing cycle was the same when chewing the 2 feeds. CONCLUSIONS: The range of mediolateral displacement of the mandible was sufficient to give full occlusal contact of the upper and lower dental arcades when chewing hay but not when chewing pellets. POTENTIAL RELEVANCE: These findings support the suggestion that horses receiving a diet high in concentrate feeds may require more frequent dental prophylactic examinations and treatments to avoid the development of dental irregularities associated with smaller mandibular excursions during chewing. 相似文献
10.
卫星降水产品在缺资料地区开展水文气象研究及径流模拟中发挥着至关重要的作用,然而卫星降水产品的精度可能会影响径流模拟效果。采用多种统计指标和VIC水文模型综合评估5种卫星降水产品(CMORPH-BLD、GSMaP_Gauge、CMFD、MSWEP和PERSIANN-CDR)在雅鲁藏布江流域的精度和拉萨河流域的水文模拟效果。结果表明:(1)CMORPH_BLD和GSMaP_Gauge在少雨季存在低估,CMFD在少雨季与观测值具有很好的一致性。MSWEP和PERSIANN-CDR在多雨季和少雨季存在高估。降水量方面,CMORPH-BLD和CMFD均较为接近观测值,其他降水产品存在不同程度的高估。(2)日尺度上,除CMFD外其他卫星降水数据与观测值具有较小的相关性(0.26~0.45),CMORPH-BLD和CMFD和观测值具有较好的一致性,CMFD和MSWEP探测小降水事件(0.1,0.5,1 mm/d)的能力优于GSMaP_Gauge。各卫星降水产品在探测强降水(2,5,10 mm/d)方面能力不足。日降水2 mm/d的降水阈值为各分类指数的变化点。(3)月尺度上,各降水产品与观测值具有很... 相似文献