全文获取类型
收费全文 | 1768篇 |
免费 | 157篇 |
国内免费 | 113篇 |
专业分类
林业 | 214篇 |
农学 | 148篇 |
基础科学 | 69篇 |
126篇 | |
综合类 | 904篇 |
农作物 | 27篇 |
水产渔业 | 102篇 |
畜牧兽医 | 369篇 |
园艺 | 39篇 |
植物保护 | 40篇 |
出版年
2024年 | 6篇 |
2023年 | 50篇 |
2022年 | 57篇 |
2021年 | 57篇 |
2020年 | 83篇 |
2019年 | 97篇 |
2018年 | 30篇 |
2017年 | 77篇 |
2016年 | 105篇 |
2015年 | 78篇 |
2014年 | 113篇 |
2013年 | 102篇 |
2012年 | 151篇 |
2011年 | 140篇 |
2010年 | 125篇 |
2009年 | 104篇 |
2008年 | 103篇 |
2007年 | 105篇 |
2006年 | 85篇 |
2005年 | 86篇 |
2004年 | 57篇 |
2003年 | 52篇 |
2002年 | 38篇 |
2001年 | 26篇 |
2000年 | 20篇 |
1999年 | 11篇 |
1998年 | 11篇 |
1997年 | 15篇 |
1996年 | 10篇 |
1995年 | 10篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 9篇 |
1990年 | 7篇 |
1989年 | 5篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1985年 | 1篇 |
排序方式: 共有2038条查询结果,搜索用时 15 毫秒
931.
932.
933.
周莺 《农业图书情报学刊》2006,18(5):117-118
立足探寻中国优秀传统文化精髓,紧密联系当前医学高职学生人文素养缺乏的实际,阐述了优秀传统文化对医学生道德水准的规范作用。人格培养的净化作用,文化品味的提升作用。同时就图书馆如何弘扬优秀传统文化提出了具体的对策。 相似文献
934.
Gustavo A. Castellanos‐Galindo Jaime R. Cantera Silvana Espinosa Luz Marina Mejía‐Ladino 《水产资源保护:海洋与淡水生态系统》2011,21(1):37-48
- 1. The loss of marine biodiversity in tropical regions of the world is a major threat to human welfare. Multiple anthropogenic drivers are responsible for this situation, with complex scenarios for coastal areas in third‐world countries, where economic development often competes with conservation plans.
- 2. The International Union for the Conservation of Nature (IUCN) Red List of Threatened Species is an influential tool for setting conservation priorities at local and regional levels. The application of IUCN criteria for assessing extinction risk, however, continues to represent a major challenge in data‐poor situations present in many tropical megadiverse countries.
- 3. To overcome these difficulties, three different data sources on invertebrates and fishes present in an estuarine system representative of the tropical eastern Pacific (TEP) region (Bahía Málaga, Colombia) have been used to establish their relative local extinction risk and correlate this information with the existing IUCN Red List categories. Data sources included (1) IUCN global and national listings, (2) traditional ecological knowledge (TEK), and (3) grey literature, scientific and natural history observations.
- 4. In total, 46 threatened species were evaluated after combining the three data sources. Only 17 species were previously identified as threatened by IUCN global and national listings, whereas the remaining 29 species were classified under a threatened category after evaluating TEK, grey literature and scientific information. Some of these species are seriously threatened within the estuary because of overharvesting and habitat destruction.
- 5. Despite most of the species identified having large geographical ranges in the TEP, they may face the same threats throughout their ranges. The approach provides a useful tool to assess species extinction risk in tropical regions where resource exploitation and habitat degradation advance rapidly, making the setting of conservation priorities an urgent task. Copyright © 2011 John Wiley & Sons, Ltd.
935.
Jun Hayakawa Tomohiko Kawamura Toyomitu Horii Yoshiro Watanabe 《Fisheries Science》2007,73(2):371-377
ABSTRACT: The settlement of larval top shell Turbo ( Batillus ) cornutus in response to seven macroalgal and three benthic diatom species was examined in the laboratory. The percentages of larval settlement differed significantly among algal species, and were significantly higher on two red algal species ( Marginisporum crassissima , an articulated coralline alga, and Gelidium elegans , an agarophyte) than on the green algae, brown algae and benthic diatoms tested. Marginisporum crassissima induced larval settlement most strongly throughout the experiments. The percentage of larval settlement on a crustose coralline alga (unidentified species), which is known as a suitable substratum for abalone larvae, was much lower than on M. crassissima and G. elegans , which have morphologically complex growth forms . The percentage of settled individuals on ethanol-killed M. crassissima was much lower than on intact M. crassissima . The results indicate that physical structure is unlikely to be the main inducer of settlement; therefore, settlement of top shell larvae seems to be strongly induced by chemicals from the two red algal species. The specific distribution of juvenile top shell in the field may be at least partly determined by the strong induction of larval settlement by articulated coralline and gelidiacean algae. 相似文献
936.
Weekly variations in density of juvenile yellowfin goby Acanthogobius flavimanus with a variety of environmental variables (e.g. water temperature, salinity and transparency, and prey density) were investigated
on a tidal mudflat within the Tama River estuary, central Japan, from March to July 2001. Metamorphosing newly settled juveniles
occurred from mid-March to late May. Metamorphosed benthich juveniles first appeared in late March, the density sharply increasing
to a peak (67.0 ind./m2) in early May but rapidly decreasing to less than 10% of that two weeks later. No consistent relationships were apparent
between short-term variations in fish density by developmental stages and water temperature, or salinity. In contrast, a weak
negative relation was found between juvenile density and water transparency. Further, benthic juvenile density was positively
related to short-term fluctuations of errant polychaetes, which is one of the main prey items. 相似文献
937.
Takashi Yokota Reiji Masuda Hiroyuki Takeuchi Tatsuo Tsuzaki Nobuaki Arai 《Fisheries Science》2007,73(3):500-511
ABSTRACT: To determine characteristics which may reflect the behavioral quality of red tilefish Branchiostegus japonicus after release, five wild and four hatchery-reared fish were observed in a laboratory and in the sea. The diel activity of the fish was recorded on video tape for 2 days in a tank, where the light condition was regulated to vary periodically over 24 h. The individuals were then released in Maizuru Bay and tracked using acoustic telemetry. Four wild individuals became most active at dawn during a day in the tank, and settled near the release area to stay for 28–104 days after release in Maizuru Bay. In contrast, one wild and four hatchery-reared individuals were not active at dawn, and then did not settle in Maizuru Bay after release. Among the four settled wild individuals, the more active a fish had been in the tank, the more distant the individual moved from the release point until its settlement. The diel activity pattern should be a factor deciding whether red tilefish would settle nearby after release, and the relative amount of activity during rearing is probably related to the degree of dispersion within the release area. 相似文献
938.
939.
中草药饲料抗菌保健剂的研究与应用 总被引:2,自引:0,他引:2
中草药饲料抗菌保健剂是一类十分重要的绿色饲料添加剂。它涵盖了中草药饲料抗微生物剂、免疫增强剂和抗应激剂等内容。研究表明,许多中草药本身就具有良好的体外抑菌能力,与西药不同的是,中草药饲料抗菌保健剂无残留、无耐药性,其作用机理不仅仅在于对病原微生物的抑杀作用,更重要的是对机体抗病修复能力的调整,即调动机体的应激能力、提高机体免疫功能和抗病防御机能,从而达到提高动物生产性能和饲料利用效率的目的。 相似文献
940.