全文获取类型
收费全文 | 16219篇 |
免费 | 983篇 |
国内免费 | 1397篇 |
专业分类
林业 | 2015篇 |
农学 | 1112篇 |
基础科学 | 684篇 |
2293篇 | |
综合类 | 7646篇 |
农作物 | 445篇 |
水产渔业 | 938篇 |
畜牧兽医 | 2306篇 |
园艺 | 409篇 |
植物保护 | 751篇 |
出版年
2024年 | 100篇 |
2023年 | 332篇 |
2022年 | 494篇 |
2021年 | 557篇 |
2020年 | 547篇 |
2019年 | 700篇 |
2018年 | 361篇 |
2017年 | 611篇 |
2016年 | 742篇 |
2015年 | 682篇 |
2014年 | 884篇 |
2013年 | 880篇 |
2012年 | 1281篇 |
2011年 | 1361篇 |
2010年 | 1095篇 |
2009年 | 1109篇 |
2008年 | 1011篇 |
2007年 | 1143篇 |
2006年 | 885篇 |
2005年 | 735篇 |
2004年 | 519篇 |
2003年 | 403篇 |
2002年 | 334篇 |
2001年 | 256篇 |
2000年 | 250篇 |
1999年 | 202篇 |
1998年 | 158篇 |
1997年 | 134篇 |
1996年 | 126篇 |
1995年 | 126篇 |
1994年 | 121篇 |
1993年 | 100篇 |
1992年 | 70篇 |
1991年 | 88篇 |
1990年 | 56篇 |
1989年 | 59篇 |
1988年 | 33篇 |
1987年 | 18篇 |
1986年 | 9篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1956年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
91.
92.
为研究不同剂量25羟基维生素D3[25(OH)VD3]对断奶前犊牛血液水平、抗氧化能力和免疫功能的影响,选取18 头健康状况良好的新生荷斯坦犊牛,随机分成3 组,每组6 头进行为期56 天的饲养试验。分为对照组[不添加25(OH)VD3]、低剂量组[25(OH)VD3添加量6 000 IU/头·天]和高剂量组[25(OH)VD3添加量12 000 IU/头·天]。结果表明,与对照组相比,随着25(OH)VD3添加剂量增加,血浆生长激素、胰岛素样生长因子-1、过氧化氢酶、超氧化物歧化酶、总抗氧化能力以及免疫球蛋白G(IgG)含量显著增加(P<0.05),而丙二醛含量随剂量增加而存在降低趋势(P=0.079)。与对照组和低剂量组相比,高剂量组血浆免疫球蛋白A(IgA)含量有增加趋势(P=0.059)。综上所述,断奶前犊牛饲喂高剂量25(OH)VD3有利于促进体内生长激素和胰岛素样生长因子-1分泌,可提高犊牛抗氧化能力,增强免疫功能。 相似文献
93.
结合对广州白云山风景名胜区规划和建设的调研和观察结果,从布局、功能、配套设施、生态结构4个方面加以分析,试图总结并归纳城市风景类风景名胜区规划建设的特点和内在规律,为相关风景区规划与建设提供参考。 相似文献
94.
食用菌在京郊都市生态循环农业中的应用 总被引:3,自引:0,他引:3
食用菌产业主要利用农林业生产中的秸秆、枝杈等副产品,生产口味鲜美、营养丰富的食用菌,为农民创造了可观的经济收入;同时减少了秸秆的剩余量,降低了焚烧秸秆对环境的污染;食用菌采收后的菌渣还可生产出大量的有机肥,有利地促进了有机农业的发展。近年来,食用菌产业在京郊广泛推广,在工厂化栽培、农民散户栽培的基础上,依据北京地区气候特点,开展了反季节栽培、林下仿生栽培等各种新模式。着重介绍了食用菌产业在生态循环农业中的作用,目前京郊食用菌产业的基本情况,并以通州区、昌平区为例,介绍京郊食用菌工厂化栽培、反季节栽培与林下仿生栽培模式。 相似文献
95.
从环境保护的角度出发,重点论述了微生物在这一领域的应用现状与发展前景,指出微生物将会在21世纪的环境保护领域中发挥重要作用。 相似文献
96.
生态系统服务功能是生态系统与生态过程所形成及所维持的人类赖以生存的自然环境条件与效用,对其服务价值进行货币化评价,可以推动自然资源可持续利用,促进区域生态环境保护。以达里诺尔湖湿地为研究对象,结合达里诺尔湖湿地生态系统的结构、特征及其生态过程特点,通过资料搜集与实地调研,运用资源经济学理论和方法,对达里诺尔湖湿地生态系统服务价值进行了划分。构建了达里诺尔湖湿地生态系统服务价值评价指标体系,并对其进行了价值评价。评价结果显示达里诺尔湖湿地的服务价值为93.70×104万元,其中直接使用价值为2.19×104万元,占比为2.36%,间接使用价值为91.51×104万元,占比为97.66%。各项生态系统服务功能中以调节空气湿度价值最大,为82.76×104万元,占总服务价值的88.32%。 相似文献
97.
98.
Modern cities use straightened and concrete watercourses with simple greening for riparian zones, which has been criticised for insensitivity to natural system integrity and cultural identity. This increases the challenge to urban ecologists, landscape designers and managers to conceive innovative and effective design solutions that do not jeopardise hydraulic efficiency yet are culturally acceptable to local communities. This paper introduces the field of local ecological knowledge (LEK) as rich sources of inspiration and design solutions to meet this challenge. LEK refers to knowledge and practices of various local cultures about the relationship of living beings (including humans) with their environments. Wepropose a pragmatic framework that integrates LEK with modern landscape design. It includes steps: (1) investigate existing practices, skills andmeasures relating to LEK; (2) explore how and whereLEKcan inspire or integrate withdesign. Here we propose three aspects for integration in accordance with the nature of landscaping process: overall structure, component and maintenance.(3)evaluate and test the integration in terms of its acceptability by local communities. Taking the riparian revegetation project of Hanfeng Lake Urban Wetland Park (Chongqing Municipality) as an example, we illustrate the utility of this framework. 11 local common practices relating to LEK were identified. According to thethree aspects for integration, alternative design solutions were offered. The survey showed that LEK based designwas more highly valued than other conventional ways in terms of useracceptance. We conclude that LEK provides actionable ecologically sound and culturally desirablesolutions for urbanlandscape. We also recognise that LEK evolveswith changing environments and new harmonious and dynamic human-nature relationships arecontinually re-forming. The process of acquisition and application of LEK could encourage multidisciplinary and synthetic approaches to urban ecosystems. Such adaptability and interdisciplinary engagementare crucial totoday’schanging and complexurban environments. 相似文献
99.
《东北农业大学学报(英文版)》2016,(2):82-88
Along with the rapid advance of industrialization and urbanization process, fostering new agricultural business entities become inevitable for agricultural transformation and the construction of agricultural modernization in China. The status of the new agricultural business entities determines the level of modern agricultural development. In recent years, new agricultural business entities have grew rapidly. However, there are still many problems including the difficulties in financing loans, inadequate agricultural insurance system, bad implementation of agricultural subsidies, jagged agricultural talents and so on. In order to foster new agricultural business entities, countermeasures should be carried out to ensure financial support, perfect the agricultural insurance, strengthen the level of agricultural subsidies, strive to develop the degree of specialization agricultural operators and so on. 相似文献
100.
The assay was aimed to study the effect of Hedyotis diffusa Willd superfines powder on immune function. Three groups of mice were gavaged with the drugs at doses of 1.75,1.25 and 0.75 g/kg once a day for 7 consecutive days, repectively. The mice of control group were administered with the same volume of saline.At the last time, mice were injected into the muscle with Newcastle disease vaccine,and get peripheral blood on days 7, 14 and 21 after the medicine administration. The enhancement of innate immune responses were evaluated by using CCK-8 method, hemagglutination inhibition test, macrophage phagocytic function test and organ coefficient method. The levels of lymphocytes proliferative capacity, serum antibody, peritoneal macrophage phagocytosis and the indexes of immune organs in mice were extremely significantly enhanced (P<0.01). Hedyotis diffusa dWilld superfines powder could extremely significantly regulate the immunity function of mice (P<0.01). 相似文献