全文获取类型
收费全文 | 20608篇 |
免费 | 167篇 |
国内免费 | 198篇 |
专业分类
林业 | 1067篇 |
农学 | 439篇 |
基础科学 | 552篇 |
2085篇 | |
综合类 | 6487篇 |
农作物 | 715篇 |
水产渔业 | 231篇 |
畜牧兽医 | 7988篇 |
园艺 | 568篇 |
植物保护 | 841篇 |
出版年
2024年 | 94篇 |
2023年 | 336篇 |
2022年 | 348篇 |
2021年 | 438篇 |
2020年 | 316篇 |
2019年 | 381篇 |
2018年 | 513篇 |
2017年 | 160篇 |
2016年 | 401篇 |
2015年 | 427篇 |
2014年 | 543篇 |
2013年 | 543篇 |
2012年 | 1724篇 |
2011年 | 1804篇 |
2010年 | 760篇 |
2009年 | 560篇 |
2008年 | 1296篇 |
2007年 | 1251篇 |
2006年 | 1061篇 |
2005年 | 987篇 |
2004年 | 891篇 |
2003年 | 832篇 |
2002年 | 766篇 |
2001年 | 552篇 |
2000年 | 558篇 |
1999年 | 259篇 |
1998年 | 60篇 |
1995年 | 56篇 |
1994年 | 69篇 |
1993年 | 112篇 |
1992年 | 113篇 |
1991年 | 109篇 |
1990年 | 120篇 |
1989年 | 105篇 |
1988年 | 220篇 |
1987年 | 171篇 |
1986年 | 157篇 |
1985年 | 148篇 |
1984年 | 128篇 |
1983年 | 117篇 |
1982年 | 129篇 |
1981年 | 138篇 |
1980年 | 111篇 |
1979年 | 86篇 |
1978年 | 76篇 |
1977年 | 59篇 |
1974年 | 51篇 |
1973年 | 61篇 |
1972年 | 55篇 |
1957年 | 69篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
The study was carried out to assess the economic burden of trypanosomosis in three villages of the Metekel zone in 2009. The
disease was found to cause substantial economic losses through cattle mortality, drug purchase, and draft power loss of infected
oxen. The farmers in the area were spending a significantly (p < 0.05) higher amount of money for the treatment of trypanosomosis than all other diseases combined. The overall mortality
rate of cattle due to trypanosomosis was 4.4%. The mortality was significantly higher (p < 0.05) in an area where trypanosomosis prevalence was also higher. Many of the farmers prioritized losses of draft power
as the most important impact of the disease. The overall prevalence of the disease was 12.1%. The disease burden was significantly
(p < 0.05) higher in the rainy season than at other times of the year. In general, farmers had good knowledge on the signs and
seasonality of trypanosomosis. Thus, tsetse suppression activities that involve the local community can be an important tool
towards minimizing the economic burden of the disease in the area. 相似文献
992.
Leitner G Merin U Krifucks O Blum S Rivas AL Silanikove N 《Veterinary immunology and immunopathology》2012,147(3-4):202-210
The effects of mammary gland bacterial infection and stage of lactation on leukocyte infiltration into the mammary gland were compared among cows, goats and sheep. Animals were at two stages of lactation: mid or late. In mid-lactation animals, bacterial-free glands and coagulase negative Staphylococcus (CNS)-infected glands were compared. In late lactation only uninfected glands were studied. Of mid-lactation bacteria-free animals, goats had the highest number of leukocytes and % polymorphonuclears (PMNs), whereas sheep had the lowest and leukocytes number in cows were intermediate between sheep and goats. Based on %PMN, two cell clusters were found in sheep, which overlapped with the parallel cell clusters of cows and goats, but with a slightly higher number of leukocytes in each cell cluster. At late lactation, goats had higher values for %PMN and leukocyte numbers in comparison to cows, which had a similar cellular profile to sheep. The cellular immune response to CNS infection was similar for the three animal species, although the number of cells was different, while the basal cell level at mid-lactation and especially at the end of lactation was species specific. 相似文献
993.
994.
基于多重RT-PCR技术检测新疆甜瓜主栽区3种病毒病及其分布 总被引:5,自引:0,他引:5
采用同源克隆的方法,从新疆感染病毒病的甜瓜中克隆获得WMV、CMV、ZYMV 3种病毒CP蛋白基因的部分片段。并基于单重RT-PCR扩增条件,采用单因素分析法,优化所获得多重RT-PCR的反应体系,利用多重PT-PCR体系对48份供试样品检测。结果表明,多重RT-PCR的检测结果与单重RT-PCR结果一致,说明构建的多重RT-PCR体系具有一定准确性和稳定性,可以用于WMV、CMV、ZYMV 3种病毒的快速检测、病源鉴定、阳性筛选等研究。通过分析甜瓜主要种植区病毒病的多重RT-PCR检测结果,初步得出新疆甜瓜主栽区3种病毒的分布现状与侵染形式,从而为病毒病的防治工作提供依据,以期对新疆瓜果生产中病毒防治,田间检测,流行病学调查以及抗病毒病甜瓜育种等研究提供相应的理论基础与依据。 相似文献
995.
<正>乌克兰优质大粒大樱桃,是我国山东省寿光市1997年从乌克兰引进的优质果树,其寿命可达80 年,经济效益为20年。树的根、茎、枝叶、果实均可做药材,此树在我区5月下旬成熟,大棚栽培4月中旬5月初成熟,果甘甜,果实光亮美观,成为人们珍贵的礼品。果实可生吃,也可以加工成罐头,同时还是加工冷饮的高级原料。 相似文献
996.
按照农业部农产品质量安全中心“武汉会议”精神,新疆维吾尔自治区畜牧厅确定的工作重点和工作目标是:紧紧围绕畜产品质量安全管理和“无公害食品行动计划”的实施,依托各级畜牧行政主管部门,充分发挥各级承办机构职能作用,进一步加大无公害畜产品认定工作的宣传和推动力度;按照“统一规范,简便高效”原则,以产地认定为基础,以产品认证为核心,积极推荐认证产品,全面加快无公害畜产品认定规模;建立健全无公害畜产品认定工作体系,形成全区统一的运转有效的工作机制,与全国一盘棋。进一步增强无公害农产品认证标志的社会知名度和市场影响力,为推进畜产品质量安全水平的全面提高发挥积极作用。 相似文献
997.
OBJECTIVE: To compare blood lipid concentrations and lipoprotein patterns for captive and wild American black bears (Ursus americanus). ANIMALS: 7 captive and 9 wild adult (> or = 4 years old) black bears. PROCEDURE: Blood was collected from 2 groups of captive black bears (groups A and B) and 1 group of wild black bears (group C). Blood triglyceride (TG) and cholesterol concentrations were compared among groups. Plasma lipoproteins were isolated by use of a self-generating gradient of iodixanol, and lipoprotein patterns were compared between groups A and B. RESULTS: Captive bears (mean +/- SD, 187.8 +/- 44.4 kg) weighed significantly more than wild bears (mean, 104.8 +/- 41.4 kg), but mean body weight did not differ between groups A and B. Mean blood TG concentrations for groups B (216.8 +/- 16.0 mg/dL) and C (190.7 +/- 34.0 mg/dL) were significantly higher than that of group A (103.9 +/- 25.3 mg/dL). Mean blood cholesterol concentration was also significantly higher for group B (227.8 +/- 8.2 mg/dL) than for groups A (171.7 +/- 35.5 mg/dL) or C (190.8 +/- 26.8 mg/dL). Mean very-low-density lipoprotein TG and low-density lipoprotein cholesterol concentrations were 2- and 3-fold higher, respectively, for group B, compared with concentrations for group A. CONCLUSIONS AND CLINICAL RELEVANCE: Blood lipid concentrations vary significantly among populations of black bears. Plasma lipoprotein patterns of captive bears differed significantly between colonies and may have reflected differences in diet or management practices. 相似文献
998.
Traceability is of particular importance for those persons who suffer allergy or intolerance to some food component(s) and need a strict avoidance of the allergenic food. In this paper, methodologies are described to fingerprint the presence of allergenic species such as carrot, tomato, and celery by DNA detection. Three DNA extraction methods were applied on vegetables and foods containing or not containing the allergens, and the results were compared and discussed. Fast SYBR Green DNA melting curve temperature analyses and duplex PCR assays with internal control have been developed for detection of these allergenic vegetables and have been tested on commercial foods. Spiking food experiments were also performed, assessing that limits of detection (LOD) of 1 mg/kg for carrot and tomato DNA and 10 mg/kg for celery DNA have been reached. 相似文献
999.
以从新疆塔克拉玛干沙漠中分离纯化的3株藻种为研究对象,研究温度和不同培养基对这3个品系生长的影响,并采用扫描电镜图和光学显微镜结合的方法对其形态进行初步鉴定,进一步采用18S r DNA基因数据对其进行分子鉴定。结果可以看出,Y1在20~30℃环境中都能生长,30℃生长最佳,最佳培养基为BG11培养基;Y2和Y3在改良型TAP培养基中生长最佳,它们的最适生长温度分别为25~30℃和30℃。利用Gen Bank中绿藻门不同科属种类序列的18S核糖体RNA,结合Olmos的文献,设计18S r DNA特异性引物进行PCR扩增。测序后经Blast对比、系统发育树及遗传距离分析,结合扫描电镜图和光学显微镜结果得知Y1为丝藻属、Y2为衣藻、Y3为绿球藻。 相似文献
1000.
再氧化对土壤的通气性变异的影响 总被引:1,自引:0,他引:1
The interplay between soil physical parameters during the recovery from anoxic stresses (reoxidation) is largely unrecognized. This study was conducted to characterise the soil aeration status and derive correlations between variable aeration factors during reoxidation. Surface layers (0-30 cm) of three soil types, Haplic Phaeozem, Mollic Gleysol, and Eutric Cambisol (FAO soil group), were selected for analysis. The moisture content was determined for a range of pF values (0, 1.5, 2.2, 2.7, and 3.2), corresponding to the available water for microorganisms and plant roots. The variability of a number of soil aeration parameters, such as water potential (pF), air-filled porosity (Eg), oxygen diffusion rate (ODR), and redox potential (Eh), were investigated. These parameters were found to be interrelated in most cases. There were significant (P < 0.001) negative correlations of pF, Eg, and ODR with Eh. A decrease in water content as a consequence of soil reoxidation was manifested by an increase in the values of aeration factors in the soil environment. These results contributed to understanding of soil redox processes during recovery from flooding and might be useful for development of agricultural techniques aiming at soil reoxidation and soil fertility optimisation. 相似文献