全文获取类型
收费全文 | 113136篇 |
免费 | 6982篇 |
国内免费 | 8529篇 |
专业分类
林业 | 11137篇 |
农学 | 7190篇 |
基础科学 | 8048篇 |
29509篇 | |
综合类 | 48295篇 |
农作物 | 4618篇 |
水产渔业 | 2152篇 |
畜牧兽医 | 9242篇 |
园艺 | 2729篇 |
植物保护 | 5727篇 |
出版年
2024年 | 726篇 |
2023年 | 2568篇 |
2022年 | 3715篇 |
2021年 | 4113篇 |
2020年 | 4080篇 |
2019年 | 4716篇 |
2018年 | 3031篇 |
2017年 | 4888篇 |
2016年 | 5966篇 |
2015年 | 4648篇 |
2014年 | 6163篇 |
2013年 | 6874篇 |
2012年 | 9504篇 |
2011年 | 8385篇 |
2010年 | 6584篇 |
2009年 | 6690篇 |
2008年 | 5835篇 |
2007年 | 6667篇 |
2006年 | 5655篇 |
2005年 | 4583篇 |
2004年 | 3598篇 |
2003年 | 3136篇 |
2002年 | 2339篇 |
2001年 | 2175篇 |
2000年 | 1914篇 |
1999年 | 1496篇 |
1998年 | 1216篇 |
1997年 | 1137篇 |
1996年 | 979篇 |
1995年 | 1013篇 |
1994年 | 883篇 |
1993年 | 718篇 |
1992年 | 600篇 |
1991年 | 541篇 |
1990年 | 421篇 |
1989年 | 357篇 |
1988年 | 253篇 |
1987年 | 175篇 |
1986年 | 97篇 |
1985年 | 46篇 |
1984年 | 34篇 |
1983年 | 11篇 |
1982年 | 27篇 |
1981年 | 19篇 |
1980年 | 14篇 |
1979年 | 11篇 |
1978年 | 10篇 |
1962年 | 10篇 |
1956年 | 8篇 |
1955年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
In this paper, the historical reasons of formation of the village inside the city are analyzed. It is indicated that such situation for the villages inside the city are the result of joint action of both the villagers and the government. The foundation of villages inside the city laid on the simple compensation for farmers in confiscating the rural land and lack of intelligence aids. In this paper, the ideas and measures for their reconstruction are put forward based on consideration of the reasons of their formation and difficulties in the reconstruction. 相似文献
993.
Critical information system in Interact is in face of increasingly security problems. More attention has been focused on the survivability of information system, which is the capability of system to continue its mission even in the presence of damage to the system. The authors first introduce the definition of survivability. According to four function properties of survivability, which are Resistance, Recognition, Recovery, and Adaption, the authors design a model of survivable system structure and then explain survivability requirement, survivability strategy in this model. Additionally, they provide possible technical solutions for the survivability of systems, categorized by different aspects of our survivability strategy. 相似文献
994.
The activation of black soil (analog the lignite) by electro-hydraulic impulse is proposed. The abundant insoluble nitrogen, phosphorus, potassium and other organic elements in black soil are activated as the green fertilizer by this way. The new method is provided for activating sludge produced by treating wastewater. For several kinds of black soil, the experiment result indicates that electro-hydraulic impulse increases the percentage of absorbable nitrogen by 1 to 4 times and the percentage of insoluble organic elements by 4 times, which is a valuable reference to sludge treatment. 相似文献
995.
In this paper, the selection of type, function and technological requirements of EMCS for Shenzhen Underground has been introduced.Based on the investigation for EMCS's worldwide applications and the analysis of practice in Shenzhen Underground, the comparison and selection of PLC and DDC have been done completely.At the same time,the introduction of EMCS is organized by the center level, station level and the spot level. 相似文献
996.
It is difficult to measure the geometric quantity of small parts in finishing, assembling and measuring, because it's easy to break the workpieces' surface and alter their position by means of traditional contact measuring methods.There are some non contact measurers, such as,light feeler pin and interference microscope etc., because of it's high price and strict working conditions,so it's difficult to promote them in widely use. Precision measurement system based on machine vision has the advantages of non contact measuring as well as high performance and low price. Some problems, such as light source, algorithm of edge fitting, auto focusing,are discussed. 相似文献
997.
ZHOU Hua-jun 《保鲜与加工》2001,(5):1
Hydrodynamic models have been widely applied to river and coastal engineering projects. Understanding the hydrodynamic process is a prerequisite to modeling the pollution and sediment transport process. Hydrodynamic models of varying degrees of complexity should be selected appropriately according to the object of study, physical properties of the flow domain and hydrodynamic features. The essential procedure of hydrodynamic simulation is described in this paper. The main problems such as selection of model dimension in physical space, choice of variables, boundary conditions, initialization, design of computational grid, model resolution, parameterization of smaller scale fluctuations and sub-grid scale processes, model calibration and verification are investigated. 相似文献
998.
This peper commentaried some of our country comparatively well-known enterprise informationization estimate theory,point out,there is existing the question of informationization estimates,that the achievement can't guarantee "appropriate informationization" establishing and enterprise informationization sustainable development,It propose the three-dimensional enterprise informationization estimate the theory and method,that includes information-based level,information-based quality and information-based development potentiality. 相似文献
999.
1000.
Employing the standpoint of irrational investors in the behavior finance, the authors study the relation on the irrational behavior of medium and small Investors and underpricing of IPO in our country. The paper premises that a revenue-maximizing issuer will be regarded as the target function, and the rational institutional investors can be delegated the task of holding the stocks in the after-market for resale to the irrational medium and small investors--thereby extracting surplus from them, finally the issuer can maximize their expected revenue. We model the process mentioned above and find that the high underpricing of IPO in our country has the direct relation with numerous the irrational medium and small investors existing in our country who cause the underpricing. 相似文献