全文获取类型
收费全文 | 98993篇 |
免费 | 19951篇 |
国内免费 | 28228篇 |
专业分类
林业 | 8950篇 |
农学 | 7711篇 |
基础科学 | 8387篇 |
39855篇 | |
综合类 | 32479篇 |
农作物 | 7367篇 |
水产渔业 | 8018篇 |
畜牧兽医 | 23308篇 |
园艺 | 2833篇 |
植物保护 | 8264篇 |
出版年
2024年 | 997篇 |
2023年 | 1108篇 |
2022年 | 1437篇 |
2021年 | 1442篇 |
2020年 | 3084篇 |
2019年 | 6629篇 |
2018年 | 6722篇 |
2017年 | 7603篇 |
2016年 | 8392篇 |
2015年 | 8187篇 |
2014年 | 7404篇 |
2013年 | 8398篇 |
2012年 | 8102篇 |
2011年 | 7206篇 |
2010年 | 5579篇 |
2009年 | 5073篇 |
2008年 | 4501篇 |
2007年 | 4531篇 |
2006年 | 3989篇 |
2005年 | 3596篇 |
2004年 | 3551篇 |
2003年 | 3312篇 |
2002年 | 2825篇 |
2001年 | 2588篇 |
2000年 | 2314篇 |
1999年 | 2130篇 |
1998年 | 1558篇 |
1997年 | 1563篇 |
1996年 | 1350篇 |
1995年 | 1452篇 |
1994年 | 1388篇 |
1993年 | 1151篇 |
1992年 | 1375篇 |
1991年 | 1313篇 |
1990年 | 1051篇 |
1989年 | 1037篇 |
1988年 | 943篇 |
1987年 | 824篇 |
1986年 | 774篇 |
1985年 | 619篇 |
1984年 | 550篇 |
1983年 | 498篇 |
1982年 | 441篇 |
1981年 | 425篇 |
1979年 | 548篇 |
1978年 | 428篇 |
1975年 | 430篇 |
1974年 | 435篇 |
1973年 | 416篇 |
1967年 | 409篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
A urinary bladder mass in a 12-year-old spayed female West Highland White Terrier was diagnosed after exploratory surgery and biopsy as a transitional cell carcinoma. Four months later the dog presented with an ulcerated plaque-like cutaneous lesion at the previous surgical incision site; concurrent inguinal lymphadenopathy and recurrence of the urinary bladder mass were identified. Transitional cell carcinoma was diagnosed at all 3 sites. Although a definitive relationship cannot be established between the initial surgery for urinary bladder mass and the resultant subcutaneous lesion, surgical implantation should be considered as a source for the neoplastic cells. 相似文献
22.
23.
提出了环泵泡沫比例混合器和泡沫压力比例混合器在相应灭火系统中的应用、安装和操作中应注意的问题,对两种泡沫比例混合器组成的系统进行了对比,认为环泵比例混合泡沫灭火系统采用正压进水,可以克服负压进水方式存在的缺陷,比较适合油库火灾的扑救;压力比例混合泡沫灭火系统灵活性、匹配性较差,适用于泡沫混合液流量相对不变的火灾扑救。 相似文献
24.
25.
The immunohistochemical detection of Mycoplasma bovis and bovine viral diarrhea virus in tissues of feedlot cattle with chronic, unresponsive respiratory disease and/or arthritis.
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)
D M Haines K M Martin E G Clark G K Jim E D Janzen 《The Canadian veterinary journal. La revue veterinaire canadienne》2001,42(11):857-860
The purpose of this study was to determine the frequency of selected pathogens in the tissues of a group of feedlot cattle with chronic disease (most often respiratory disease and/or arthritis). Samples of lung and joint tissues from 49 feedlot animals that had failed to respond to antibiotic therapy were tested by immunohistochemical staining for the antigens of Mycoplasma bovis, Haemophilus somnus, Pasteurella (Mannheimia) hemolytica, and bovine viral diarrhea virus (BVDV). Mycoplasma bovis was demonstrated in over 80% of cases, including in 45% of joints and 71% of lungs tested. Mycoplasma bovis was the only bacterial pathogen identified in the joints. Haemophilus somnus and Pasteurella (Mannheimia) haemolytica were found in 14% and 23% of cases, respectively, and were confined to the lungs in all instances. Infection with BVDV was demonstrated in over 40% of cases. Mycoplasma bovis and BVDV were the most common pathogens persisting in the tissues of these animals that had failed to respond to antibiotic therapy. 相似文献
26.
关于我国海水网箱养鱼发展现状与危机分析及可持续发展的探讨 总被引:3,自引:1,他引:2
我国海水网箱养鱼发展现状是以个体联合体生产经营为主体的低技术水平的数量规模化,众多传统港湾已形成了大范围的严重超负荷养殖状态,其对环境巨大的污染力引发鱼病猖獗和频受赤潮侵袭,已面临严峻的养殖环境危机。本文综合分析了我国海水网箱养鱼的发展现状与负面效应及其现状危机,并初步进行了危机根源和可持续发展的讨论分析。 相似文献
27.
SUMMARY: Aoshio is hypoxic milky blue-green seawater observed in some eutrophic bays. Previous studies have shown that colloidal sulfur causes the coloration and that the source of aoshio water is attributed to coastal anoxic bottom water. Occurrences of aoshio have been reported in limited areas of coastal seawater, although hypoxic transparent water seems rather universal. Promotion in auto-oxidation of sulfide by metal ions in seawater was investigated to explain the occurrences of aoshio. Artificial seawater containing 10 μM metal ion was assayed for the sulfide oxidation rate. The velocity constant which represents the oxidation rate within the initial 30 min and the amount of reacted sulfide in 2 h were determined by oxygen monitoring and sulfide quantification, respectively. Fe2+ and Cu2+ enhanced the initial 30 min reaction. Fe2+ , Fe3+ and Ni2+ increased the amount of reacted sulfide in 2 h, forming whitish turbid water. Seawater from a suspected source of aoshio water was also assayed for the auto-oxidation rate of sulfide. The oxidation rate in water from 12 m depth was 13–19 times higher than the artificial seawater without an addition of heavy metal ions. More than 15% of the oxidation rate in 12 m deep seawater was explained by dissolved iron in the seawater. 相似文献
28.
29.
30.