全文获取类型
收费全文 | 9259篇 |
免费 | 598篇 |
国内免费 | 928篇 |
专业分类
林业 | 1084篇 |
农学 | 631篇 |
基础科学 | 485篇 |
2017篇 | |
综合类 | 3672篇 |
农作物 | 278篇 |
水产渔业 | 905篇 |
畜牧兽医 | 857篇 |
园艺 | 158篇 |
植物保护 | 698篇 |
出版年
2024年 | 108篇 |
2023年 | 252篇 |
2022年 | 313篇 |
2021年 | 363篇 |
2020年 | 422篇 |
2019年 | 501篇 |
2018年 | 288篇 |
2017年 | 448篇 |
2016年 | 496篇 |
2015年 | 401篇 |
2014年 | 510篇 |
2013年 | 570篇 |
2012年 | 750篇 |
2011年 | 692篇 |
2010年 | 549篇 |
2009年 | 584篇 |
2008年 | 468篇 |
2007年 | 576篇 |
2006年 | 419篇 |
2005年 | 368篇 |
2004年 | 283篇 |
2003年 | 215篇 |
2002年 | 198篇 |
2001年 | 143篇 |
2000年 | 140篇 |
1999年 | 99篇 |
1998年 | 87篇 |
1997年 | 78篇 |
1996年 | 61篇 |
1995年 | 78篇 |
1994年 | 71篇 |
1993年 | 50篇 |
1992年 | 44篇 |
1991年 | 45篇 |
1990年 | 26篇 |
1989年 | 34篇 |
1988年 | 16篇 |
1987年 | 17篇 |
1986年 | 3篇 |
1984年 | 3篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1962年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
《保鲜与加工》1997,(6):116-121
A review on environment-monitoring biosensors is presented.During recent years,various environment-monitoring biosensors are fast developed.They are applied to various areas,such as aquatic environment,atmosphere environment et al.The developing trend of environment_monitoring biosensors is also discussed. 相似文献
52.
According to the new requirement of sustainable development in the new stage, this paper puts forward the definition of the safeguarding capacity of regional sustainable development and uses some statistical methods of frequency statistics and principal component analysis to construct the index system of safeguarding capacity. Then it takes the data of the Three Gorges reservoir area for example to make empirical analysis, and provides efficient measurement tools to further measure the regional sustainability together with its safeguarding capacity, and therefore helps the government and the relevant organizations to establish more scientific policies of sustainable development. 相似文献
53.
54.
The externality of surrounding is introduced into the 2-capital of economical increasing models, which includes human factors, to explore the influences of circumstances contradiction on the human capital formation. The normal and special nash equilibrium of environmental and human capital is presented through a limited boundary model of overlapping generations. The character of equilibrium trail and its economical meaning are examined. The study on the model shows that laissez faire economy will be either stagnant,growing,or collapsing in the long-run,depending on the returns of the learning technology with respect to the two kinds of capital,the initial state of economy,and the relative price of the environmental and consumption goods. 相似文献
55.
In accordance with the deficient elongation of the Stretching-bending Rectifier, as well as the severe wear and slipping of V-belt , the driving system velocity ratio of rectifier and the calculation formula of the theoretical elongation are deduced, which are based on the analysis of its structure and reeling principle. The carrying capacity of the driving system is also analyzed and it reaches the main reason for the elongation of the stretching-bending rectifier that cannot reach request, which is caused by the step less torsion of fixed output of the continuously variable transmission. The improvement measure which can be achieved by increasing the stiffness of the spring to increase the output torsion of the continuously variable transmission is proposed. Thus it makes the actual coefficient of elongation,which can satisfiy the producing request. 相似文献
56.
Yao Jiafei 《保鲜与加工》1994,(2)
This paper discusses the model for lifting capacity of the crane and optimal con-trol of eliminating swing in lifting process. One half loop control method is presented, which is onlyto examine and measure the trolley speed for eleiminating swing.The fact shows this methOd is sim-ple and practicle for enginceering. 相似文献
57.
Gao Shixian 《保鲜与加工》1988,(3)
The problem of fuzzy evaluation of environmental pollution is importantboth in environment science and in environmental protection.Usual evaluationmethods have their own characteristics.This paper puts forward a mathematicalmodel of fuzzy evaluation method in grades by means of systematic analysisfor environmental pollution.At the same time,it assigns weighted values byordering based on paired comparison. 相似文献
58.
石油污染土壤降解与土壤的环境关系 总被引:4,自引:0,他引:4
阐述了石油污染土壤的降解与土壤环境的关系;提出如何消除石油污染土壤降解的环境限制因子,为微生物降解石油提供最理想环境,是有效治理石油污染的关键. 相似文献
59.
本文以西南岩溶地区清镇市为例,采用生态足迹的理论和模型对2005年清镇市区域生态足迹状况进行了测算和分析,并与不同区域进行比较。结果表明:①清镇市2005年的人均生态足迹为2.5440hm2,超过了它的人均生态承载力;②清镇市2005年人均生态赤字为2.1240hm2,表明清镇市处于一种不可持续的发展状态;③清镇市2005年万元GDP生态足迹为2.8139hm2,高于中国西部的平均水平,资源利用为粗放消耗型。针对清镇市生态赤字的状况,提出了缓解该市生态压力、提高生态承载力的建议。 相似文献
60.
农村小水电站机组增容改造的方法 总被引:2,自引:1,他引:2
我国在20世纪70年代兴建的小水电站已运行了几十年,随着新技术与新材料的应用,对老电站进行增容改造,提高电站的调峰能力是提高电站和县电网经济效益的关键措施之一。介绍了机组增容改造的方法和实际应用中应注意的问题。 相似文献