全文获取类型
收费全文 | 10730篇 |
免费 | 710篇 |
国内免费 | 860篇 |
专业分类
林业 | 963篇 |
农学 | 555篇 |
基础科学 | 314篇 |
830篇 | |
综合类 | 5538篇 |
农作物 | 935篇 |
水产渔业 | 463篇 |
畜牧兽医 | 1418篇 |
园艺 | 856篇 |
植物保护 | 428篇 |
出版年
2024年 | 50篇 |
2023年 | 188篇 |
2022年 | 464篇 |
2021年 | 441篇 |
2020年 | 420篇 |
2019年 | 461篇 |
2018年 | 299篇 |
2017年 | 506篇 |
2016年 | 344篇 |
2015年 | 533篇 |
2014年 | 566篇 |
2013年 | 638篇 |
2012年 | 936篇 |
2011年 | 913篇 |
2010年 | 915篇 |
2009年 | 831篇 |
2008年 | 803篇 |
2007年 | 720篇 |
2006年 | 602篇 |
2005年 | 496篇 |
2004年 | 312篇 |
2003年 | 162篇 |
2002年 | 229篇 |
2001年 | 204篇 |
2000年 | 174篇 |
1999年 | 51篇 |
1998年 | 5篇 |
1997年 | 10篇 |
1996年 | 1篇 |
1995年 | 2篇 |
1994年 | 1篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1981年 | 1篇 |
1956年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
101.
In component-based system regression testing, the dependence model of component-based system should be built in order to confirm the part which will be affected by modify. Since high reusability and high complexity, the existing dependence models may not be applicable to component-based systems, a hierarchical dependence model is proposed to describe component-based. Through the forward slicing of modified points in the model, the modified and affected parts can be gotten, then traverse these parts and get affected testing path, thereby regression testing examples can be chosen effectively, the efficiency of regression testing can be improred. 相似文献
102.
A Coptis Chinesis is the dry rhizoma of ranunculaceous Coptis Chinesis Franch or Coptis deltoidea C. 7. Cheng et Hisao, or Coptis teeta Wall. It is the traditional Chinese herb, which is used in the contagious diseases. In recent years, its new pharmacological actions have been reported, which are antitumour, hypoglycemic response, immunoloregulation, improving the functions of cardiovascular. The important pharmacological functions of Coptis Chinesis are hypoglycemic response, improving the functions of cardiovascular, antitumour. With the deeply researching of Coptis Chinesis pharmacology, and the continuous founding of pharmacological mechanism, new preparation will be widely applied in the clinic. 相似文献
103.
BIM Based on Intelligent Parametric Modeling Technology 总被引:1,自引:0,他引:1
In order to push the informationization process of the building industry,promote sustainable architectural design and enhance the competitiveness of China's building industry,the authors study BIM(Building Information Modeling) based on intelligent parametric modeling technology.BIM is a new technology in the field of computer aided architectural design,which contains not only geometric data but also the great amount of engineering data throughout the lifecycle of a building.The authors also compare BIM technology with 2D CAD technology,and demonstrate the advantages and characteristics of intelligent parametric modeling technology.BIM,which is based on intelligent parametric modeling technology,will certainly replace traditional computer aided architectural design and become a new driving force to push forward China's building industry in this Information Age. 相似文献
104.
105.
A developing method is given which based on object-oriented modeling techniques for management information systems.The modeling techniques,especially,from CDM to PDM conversion,make it possible that the method can be used for developing such management information systems which based on relational database.The result shows that it can raise the efficency of the system developing,improve the system tability,enhance the system maintenability. 相似文献
106.
The funneling effect of noise is the main difficulty in two way CATV modification works. This paper discusses the source of noise and interference, the mechanism to form noise funneling, the regularities of distribution, the characteristics of the spectrum, etc. The purpose is to find the way of reducing funnel noise. The invading noise has the greatest effect on the upstream of two way CATV system, which mainly comes from the indoor of the users. The increase of the number of cable modem will not obviously make greater funneling noise. The cable connectors are the main source of producing and invading noise in outdoor cable network, which is a threat to the safty of the whole upstream channel. 相似文献
107.
The techniques of sharing a channel in HFC are original with regard to those of Ethernet and Ring. In this paper, the analysis is stressed on the method of the upstream bandwidth allocation, the collision resolving, and the relationship among them, beginning with MAP management message. The MAP is a complex frame, in which the messages of ranging opportunity needed by the CM at the access beginning, bandwidth allocation contention, bandwidth allocation and collision detection are included. The access way for a user is explained after the frame format and functions of a MAP are illustrated. Finally, upstream bandwidth allocation, the cause of collision, algorithm and the process to solve the collision and so on are studied. 相似文献
108.
As a key resource, the knowledge management is becoming a research field interested by many researchers. In order to study the mathematics theory base of knowledge expression, in this paper, a knowledge expression model is given. In this model the knowledge system is expressed by multi-tuple, the single knowledge object is expressed by the tuple, a structural expression of knowledge is given using token as example and the application of the model in city water supply pipe network is presented in this paper. 相似文献
109.
On the assumption that the runoff on the catchment of each gully flows into the gully itself, in this paper, a model of surface storm-water runoff at urban gully is presented, which includes runoff sub-model and concentration sub-model.The runoff sub-model describes the rainfall event with instantaneous rainfall intensity, the runoff-generated event with runoff coefficient of integrative area and the runoff converged event with the principle of equal time of flowage.The concentration sub-model shows that the pollutant concentration event only changes with the runoff event at the gully.In this paper, the concrete form of the model for two gully inlets in Shapingba District of Chongqing is given.The model is calibrated with the data from the synchronized measurements of water quantity and quality at the two gully inlets obtained from July to September 2000.The relative error is calculated by comparing the model predictions with the field-measured results. 相似文献
110.