全文获取类型
收费全文 | 23675篇 |
免费 | 1688篇 |
国内免费 | 1732篇 |
专业分类
林业 | 2439篇 |
农学 | 1861篇 |
基础科学 | 2837篇 |
2535篇 | |
综合类 | 5936篇 |
农作物 | 1397篇 |
水产渔业 | 1460篇 |
畜牧兽医 | 6479篇 |
园艺 | 968篇 |
植物保护 | 1183篇 |
出版年
2024年 | 134篇 |
2023年 | 719篇 |
2022年 | 1646篇 |
2021年 | 1809篇 |
2020年 | 1605篇 |
2019年 | 1546篇 |
2018年 | 753篇 |
2017年 | 835篇 |
2016年 | 829篇 |
2015年 | 1221篇 |
2014年 | 1780篇 |
2013年 | 2346篇 |
2012年 | 2655篇 |
2011年 | 2138篇 |
2010年 | 1366篇 |
2009年 | 1211篇 |
2008年 | 556篇 |
2007年 | 826篇 |
2006年 | 740篇 |
2005年 | 329篇 |
2004年 | 231篇 |
2003年 | 191篇 |
2002年 | 163篇 |
2001年 | 173篇 |
2000年 | 153篇 |
1999年 | 132篇 |
1998年 | 92篇 |
1997年 | 75篇 |
1996年 | 78篇 |
1995年 | 50篇 |
1994年 | 42篇 |
1993年 | 40篇 |
1992年 | 25篇 |
1991年 | 42篇 |
1990年 | 39篇 |
1989年 | 37篇 |
1988年 | 23篇 |
1987年 | 25篇 |
1986年 | 19篇 |
1985年 | 23篇 |
1984年 | 27篇 |
1983年 | 22篇 |
1981年 | 20篇 |
1980年 | 19篇 |
1979年 | 26篇 |
1978年 | 17篇 |
1977年 | 18篇 |
1976年 | 19篇 |
1974年 | 19篇 |
1967年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 593 毫秒
131.
按照纳米材料在卷烟中的不同添加方式,即添加至滤棒、烟丝和其他卷烟材料中,综述了近年来纳米材料在卷烟减害方面的应用,可知今后纳米材料在卷烟中的应用前景十分广阔。 相似文献
132.
133.
以辽宁省某尾矿库为例,基于GIS技术,利用2010年的TM遥感影像及地形图,预测该尾矿库扩容后的生态影响。分析结果显示:尾矿库扩容工程对生态的影响主要体现在土地利用、植被、生态景观和地形地貌的变化4个方面。 相似文献
134.
B Genz J Gerszon Y Pollock B Gleeson R Shankar MJ Sellars RJ Moser 《Australian veterinary journal》2023,101(4):153-163
Rotaviruses (RV) have a high prevalence in piggeries worldwide and are one of the major pathogens causing severe diarrhoea in young pigs. RV species A, B, and C have been linked to piglet diarrhoea in Australian pig herds, but their genetic diversity has not been studied in detail. Based on sequencing of the structural viral protein 7 (VP7) RVA G genotypes G3, G4 and G5, and RVC types G1, G3, G5, and G6 have been identified in Australian piggeries in previous studies. Although occurrence of RVB was reported in Australia in 1988, no further genetic analysis has been conducted. To improve health management decisions in Australian pig herds, more information on RV prevalence and genetic diversity is needed. Here, 243 enteric samples collected from 20 pig farms within Eastern Australia were analysed for the presence of RV in different age groups using a novel PCR-based multiplex assay (Pork MultiPath™ enteric panel). RVA, RVB, and RVC were detected in 10, 14, and 14 farms, respectively. Further sequencing of VP7 in selected RV-positive samples revealed G genotypes G2, G5, G9 (RVA), G6, G8, G14, G16, G20 (RVB), and G1, G3, G5, G6 (RVC) present. RVA was only detected in young (<10 weeks old) pigs whereas RVB and RVC were also detected in older animals (>11 weeks old). Interestingly, RVB and RVC G-type occurrence differed between age groups. In conclusion, this study provides new insights on the prevalence and diversity of different RV species in pig herds of Eastern Australia whilst demonstrating the ability of the Pork MultiPath™ technology to accurately differentiate between these RV species. 相似文献
135.
希腊式酸奶加工中HACCP体系的建立 总被引:1,自引:0,他引:1
本文依据HACCP体系的基本原则,对希腊式酸奶加工过程进行危害分析(HA),并确定了加工中的关键控制点(CCP),同时制定了相应的控制限值和监控措施,以期通过这些措施提高希腊式酸奶生产管理水平和产品的质量水平。 相似文献
136.
在综述国内外生物质材料产业发展状况的基础上,对福建省生物质新材料的研究进展与发展进行了分析,提出了福建省生物质新材料产业发展在市场培育、区域创新系统的构建、金融服务平台建设、产业集群和高新技术产业园区建设、政府支持和公共服务职能等方面的对策与措施。 相似文献
137.
138.
Interest in planting urban food trees (UFTs) in public spaces is growing in popularity as a form of urban greening and a potential food source. Currently there is minimal research on the governance and policy aspects of integrating food trees into cities. To fill this gap, we investigated the characteristics of UFT site governance and how it compares to current urban forest governance. Semi-structured interviews were conducted with relevant municipal officials in Calgary, Edmonton, Toronto and Victoria about their perspectives and involvement with UFT sites in their city. A scan of policy documents was completed to supplement the interviews. The interviews were analyzed using a deductive coding framework based on the Policy Arrangement Approach. We found that key actors at the UFT sites were local organizations and site champions, with minimal municipal engagement. Most site resources provided by municipalities were in-kind. There are also basic knowledge gaps about how to care for UFTs. Currently municipal by-laws prohibit the harvesting and removal of plant material, and are at odds with the purpose of UFT sites, with few municipalities fully integrating UFTs in policies. The primary discussion around UFTs centre concerns for public health and safety, management, and use of public space with limited discussions of benefits. This research demonstrates the value of co-governance models to support UFTs, while a shift in focus from risks to benefits could encourage additional resources and policy integration. Further, including UFTs into policy would also support foraging and food tree maintenance in public spaces, and more fully reflect the plurality of urban forest engagement. 相似文献
139.
In this paper the results of the first comprehensive study on perception of and satisfaction with urban forests and green space in seven Southeast European cities are presented. The aims of the paper are to analyse 1) citizen perceptions of the current state of urban forests and green space in their cities, 2) to what extent current urban forests and green space meet their needs and how this can be improved. A cross-sectional study was conducted by using a common face-to-face survey questionnaire. Respondents were selected based on census data though a stratified sampling procedure by taking into account age, gender and city district (n = 384 in each city). The results showed that citizens genuinely care for urban forests and green space in their cities, but are not satisfied with their current state. The respondents found issues related to misbehaviour of other users, the presence and quality of facilities, as well as the presence and quality of management or maintenance the most pressing. There were more statistically significant differences than similarities between cities. Socioeconomic variables explained perceptions only to some extent. Citizens were very supportive of educational campaigns about the importance of urban forests and green space as well as of better enforcement of the existing regulations though having more community wardens that were expected to tackle current unsatisfactory situations. Urban planning and urban forest and green space management in these cities are facing many problems characteristic for post-socialist countries. Study findings are expected to contribute to decision making in urban planning and natural resource management. 相似文献
140.
文章从文化的角度,对中国古典园林所蕴含的哲学思想及审美情趣进行了阐述,探讨了中国传统文化对园林艺术的影响并分析中国传统园林中意境形成的原因及表现方法,可以获得对其更深的认识,以期给现代设计师以启发和思考,从传统文化中汲取精华走一条中国特色的设计之路. 相似文献