全文获取类型
收费全文 | 141532篇 |
免费 | 21056篇 |
国内免费 | 31468篇 |
专业分类
林业 | 16634篇 |
农学 | 18818篇 |
基础科学 | 13781篇 |
41027篇 | |
综合类 | 52123篇 |
农作物 | 10109篇 |
水产渔业 | 8674篇 |
畜牧兽医 | 17857篇 |
园艺 | 4535篇 |
植物保护 | 10498篇 |
出版年
2024年 | 1115篇 |
2023年 | 1736篇 |
2022年 | 3353篇 |
2021年 | 4210篇 |
2020年 | 5265篇 |
2019年 | 8464篇 |
2018年 | 7419篇 |
2017年 | 8724篇 |
2016年 | 9103篇 |
2015年 | 9935篇 |
2014年 | 9082篇 |
2013年 | 10362篇 |
2012年 | 10806篇 |
2011年 | 10341篇 |
2010年 | 9080篇 |
2009年 | 8448篇 |
2008年 | 7196篇 |
2007年 | 7501篇 |
2006年 | 6964篇 |
2005年 | 6672篇 |
2004年 | 4196篇 |
2003年 | 3639篇 |
2002年 | 3140篇 |
2001年 | 2908篇 |
2000年 | 2973篇 |
1999年 | 3569篇 |
1998年 | 3133篇 |
1997年 | 2811篇 |
1996年 | 2627篇 |
1995年 | 2530篇 |
1994年 | 2444篇 |
1993年 | 2118篇 |
1992年 | 1952篇 |
1991年 | 1676篇 |
1990年 | 1361篇 |
1989年 | 1186篇 |
1988年 | 960篇 |
1987年 | 666篇 |
1986年 | 538篇 |
1985年 | 309篇 |
1984年 | 255篇 |
1983年 | 237篇 |
1982年 | 240篇 |
1981年 | 270篇 |
1980年 | 211篇 |
1979年 | 171篇 |
1978年 | 146篇 |
1975年 | 118篇 |
1965年 | 142篇 |
1964年 | 148篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
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
62.
63.
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
64.
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
65.
选取 1998年若干衡量企业技术开发活动投入与产出水平方面的指标进行计算 ,通过与全国大中型工业企业对比分析 ,揭示林业大中型工业企业存在的差距 ,为林业工业企业和有关部门采取相应措施以改变其落后状况提供参考。 相似文献
66.
W W Chan K Y Chen H Liu L S Wu J H Lin 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2001,63(10):1057-1062
Since the International Society of Veterinary Acupuncture (IVAS) was founded in 1974, acupuncture (AP) has received greater acceptance by veterinary professionals throughout the world. This article introduces some important animal diseases that respond well to AP therapy. These include resuscitation of small animals, treatment of anoestrous gilts and sows, bovine reproductive disease, canine vertebral problems and equine backpain, etc. Conventional medicine considers these to be difficult cases to treat. Veterinarians have become more aware of the benefits of AP especially for those diseases, thanks to the efforts of experienced practitioners and scientists, and the many published reports on veterinary AP that have introduced some good indications for AP therapy in veterinary practice. Possible mechanisms behind the effectiveness of AP are discussed. This article aims to introduce veterinarians to good indications for AP to initiate their interest in the practice of AP. Although this is a rapidly expanding field, a long march must begin with one step. We wish this article to be the shoes for such a march. For more information on veterinary AP, contact IVAS , P.O. Box 1478, Longmont, CO.. 80502, USA (http://www.ivas.org), or your national veterinary acupuncture society (http://www.komvet.at/ ivadkom/vapsocs.htm). 相似文献
67.
68.
鸡的微卫星DNA标记与胴体性状的相关分析 总被引:4,自引:1,他引:3
测定了青脚麻鸡与隐性白鸡杂交后自交的F2代个体的全净堂重、全净堂率、脂肪宽带、腹脂重和腹脂率6个胴体性状,检测10个微卫星DNA标记,对标记基因型胴体性状值进行方差分析和多重比较,结果表明:MCW328对于10周龄体重和全净膛重两性状各基因型均有显著的差异(P<0.05);ADL292对于腹脂重性状各基因型有极显著的差异(P<0.01),对于腹脂率有显著的差异(P<0.05)。MCW328标记基因与控制10周龄体重和全净膛重QTL连锁,ADL292标记基因与控制腹脂重和腹脂率QTL连锁。 相似文献
69.
阔叶红松林的生物量和营养元素含量的研究 总被引:6,自引:0,他引:6
一、研究内容和方法我们于1985—1987年对小兴安岭阔叶红松林的生物量进行了研究。生物量的测定是在凉水自然保护区的阔叶红松林内进行的。林龄220年,组成8红2椴,林分平均高23.1m,平均直径37.4cm。其中红松平均高27.2m,平均直径45.2cm,密度622株/ha,针 相似文献
70.