全文获取类型
| 收费全文 | 5345篇 |
| 免费 | 2047篇 |
| 国内免费 | 26篇 |
专业分类
| 林业 | 839篇 |
| 农学 | 215篇 |
| 基础科学 | 156篇 |
| 1037篇 | |
| 综合类 | 1651篇 |
| 农作物 | 176篇 |
| 水产渔业 | 103篇 |
| 畜牧兽医 | 2794篇 |
| 园艺 | 58篇 |
| 植物保护 | 389篇 |
出版年
| 2025年 | 105篇 |
| 2024年 | 235篇 |
| 2023年 | 242篇 |
| 2022年 | 266篇 |
| 2021年 | 267篇 |
| 2020年 | 249篇 |
| 2019年 | 325篇 |
| 2018年 | 192篇 |
| 2017年 | 246篇 |
| 2016年 | 323篇 |
| 2015年 | 250篇 |
| 2014年 | 285篇 |
| 2013年 | 294篇 |
| 2012年 | 410篇 |
| 2011年 | 426篇 |
| 2010年 | 298篇 |
| 2009年 | 316篇 |
| 2008年 | 324篇 |
| 2007年 | 339篇 |
| 2006年 | 297篇 |
| 2005年 | 262篇 |
| 2004年 | 218篇 |
| 2003年 | 193篇 |
| 2002年 | 152篇 |
| 2001年 | 127篇 |
| 2000年 | 124篇 |
| 1999年 | 97篇 |
| 1998年 | 77篇 |
| 1997年 | 94篇 |
| 1996年 | 76篇 |
| 1995年 | 56篇 |
| 1994年 | 58篇 |
| 1993年 | 48篇 |
| 1992年 | 38篇 |
| 1991年 | 37篇 |
| 1990年 | 21篇 |
| 1989年 | 16篇 |
| 1988年 | 18篇 |
| 1987年 | 5篇 |
| 1986年 | 2篇 |
| 1985年 | 1篇 |
| 1984年 | 3篇 |
| 1981年 | 1篇 |
| 1979年 | 1篇 |
| 1978年 | 1篇 |
| 1976年 | 1篇 |
| 1973年 | 1篇 |
| 1956年 | 1篇 |
排序方式： 共有7418条查询结果，搜索用时 0 毫秒
181.
根据《农牧厅关于基本草原划定试点工作实施方案》的要求,都兰县2009～2010年开展基本草原划定试点工作,完成了野外调查、核实,内业整理、制图,政府公告、基本草原保护标志设立等工作。对试点工作加以总结,以期对全省基本草原划定工作提供借鉴。 相似文献
182.
甘孜州退化草地生态系统综合治理对策研究 总被引：5，自引：0，他引：5
介绍了甘孜州草地生态系统现状,在分析草地退化原因和危害的基础上,提出了综合治理退化草地生态系统的措施。 相似文献
183.
Swidiq Mugerwa 《Grassland Science》2015,61(2):75-82
Located in central Uganda, the grasslands of Nakasongola face devastation of herbaceous vegetation by subterranean termites. Reduction in the preferred food of termites (plant litter), and loss of their natural predators and parasites are known to be major factors contributing to the damage imposed by termites on grassland vegetation. This review analyzes the situation with respect to termites in the area to draw the attention of ecologists, conservationists, policy makers and farmers, to the current and future threats of subterranean termites to the functioning and sustainability of this ecosystem. The suppressive effect of anthropogenic activities on termites' food resources, populations of natural enemies and the resultant escalation in termite populations is discussed. I hypothesize that tree cutting, overgrazing and overhunting are reducing the food resources and predator populations and, consequently, are enhancing the current destructive behavior of termites in the rangelands of Uganda. It is suggested that intervention for sustainable management of termites in the area should consider restoring their natural food sources and predators to reestablish the ecological equilibrium between termites and other components of the ecosystem. 相似文献
184.
185.
A. Johansen M. Höglind 《Acta Agriculturae Scandinavica, Section A - Animal Sciences》2013,63(3):148-158
Abstract Herbage intake (HI), milk production and sward utilization of Norwegian Red Cattle dairy cows in mid-lactation, rotationally grazing grass/white clover swards at low, medium and high allowances (HA), were examined in three experiments (I, II and III). The daily target allowances per cow were 18 and 36 kg DM in Experiment I and 12, 18, and 24 kg DM in Experiments II and III. The cows were grazing in groups of seven (Experiments II and III) to ten (I) individuals. The proportions of white clover in the swards averaged 12%, 40% and 46% in Experiments I, II and III, respectively. In addition to pasture, the cows were fed concentrate mixtures in varying amounts (0–6.8 kg) with the highest amounts offered to the highest yielding cows. HI was estimated using the n-alkane technique. No effect of HA on HI was obtained in Experiment I. In Experiment II, and for II and III combined, there was a significant positive effect of HA on HI. The average increase in HI was 0.24 kg DM per extra kg DM on offer. The utilization of the sward (measured at 3 cm above ground level) decreased from 72% at the lowest HA to 51% at the highest HA in Experiment II and III. HA did not affect milk yield or milk composition significantly (P>0.05). 相似文献
186.
Koji Nakagami Masayuki Hojito Shiro Itano Kazunori Kohyama Tomoko Miyaji Aya Nishiwaki Shoji Matsuura Michio Tsutsumi Shunpei Kano 《Grassland Science》2009,55(2):96-103
To evaluate the carbon (C) sequestration function of grassland soils in Japan, soil C stocks were measured in 24 grasslands (3–43‐year‐old pastures) across 14 livestock farms nationwide. Soil C stocks varied among soil types, and the values in the upper 25 and 50 cm were higher in Andosols (mean, 12.4 and 19.3 kg m−2, respectively) than in Brown Forest soils (7.5 and 13.7 kg m−2) and other soil types (5.5 and 7.5 kg m−2). At the same time, C stocks varied among pastures within each soil type. Compared to data from the published work on the C content shortly after pasture establishment, aged pastures had decreasing C concentrations as the soil depth increased, suggesting substantial C accumulation in the top soil layers during pasture aging. This C accumulation caused grassland soils to store as much C as adjacent forest soils. Although the C stocks in the grassland soils were not statistically different from those in the adjacent native forest soils, some grassland areas stored greater amounts of C than the forests, indicating a possibility of increasing soil C stocks through improved grassland management. 相似文献
187.
188.
研究了一元溶剂、二元溶剂、三元溶剂对西瓜番茄红素提取效率的影响,应用正交试验优化了超声波辅助混合溶剂提取西瓜番茄红素工艺。结果表明,一元溶剂中石油醚、乙酸乙酯对西瓜番茄红素的提取效果较好;二元混合溶剂中,乙酸乙酯-丙酮(7∶1)的提取效果最好;三元混合溶剂中乙酸乙酯∶丙酮∶甲醇(7∶1∶1)的提取效果最好;提取西瓜番茄红素的最佳溶剂是体积比为7∶1的乙酸乙酯-丙酮混合溶剂。超声波提取西瓜番茄红素的最佳工艺为超声波功率225 W,超声温度50℃,超声时间20 min,料液比为1∶5(g∶m L)。 相似文献
189.
在混合所有制二级学院办学体制机制下,教工党员先锋作用的发挥对改革至关重要。本文以朋朋宠物科技学院为例,从教工党员先锋作用发挥的模式创建、具体途径和举措、改革的成效等方面,进行了全面的论述。 相似文献
190.
In Europe, the decline in agriculture in traditional mountain farming areas has caused abandonment, or irregular grazing, of less accessible pastures. In the Italian Alps, we studied plant diversity, forage value and trophic traits in six large‐scale heterogeneously grazed Nardus pastures, in their central and peripheral parts, and across the montane, lower and upper subalpine zones. Seventy cover‐abundance floristic relevés were performed in randomly located permanent plots, half at the pasture edge (M‐plots) and half in their central part (C‐plots). Plant diversity varied significantly with respect to the distance from the edge, being higher in M‐plots because of shrub invasion as a consequence of reduced cattle pressure. Nardus cover was slightly higher in C‐plots and negatively related to plant diversity. Forage value was lower in M‐plots and negatively correlated with the cover of Nardus and woody species, implying that different grazing pressure was negatively influencing sward productivity. Differences in trophic traits of swards between C‐ and M‐plots existed mostly as trends. Forage value significantly decreased in the lower subalpine and montane pastures, which are further grazed in late summer. Heterogeneous grazing management was therefore exerting positive effects on plant diversity and negative effects on forage value. Results are discussed in the context of future management recommendations. 相似文献