全文获取类型
收费全文 | 75264篇 |
免费 | 3057篇 |
国内免费 | 4179篇 |
专业分类
系统科学 | 3734篇 |
丛书文集 | 2162篇 |
教育与普及 | 1654篇 |
理论与方法论 | 331篇 |
现状及发展 | 522篇 |
研究方法 | 210篇 |
综合类 | 73880篇 |
自然研究 | 7篇 |
出版年
2024年 | 370篇 |
2023年 | 795篇 |
2022年 | 1328篇 |
2021年 | 1454篇 |
2020年 | 1127篇 |
2019年 | 632篇 |
2018年 | 793篇 |
2017年 | 1002篇 |
2016年 | 1130篇 |
2015年 | 2060篇 |
2014年 | 2872篇 |
2013年 | 2873篇 |
2012年 | 3276篇 |
2011年 | 3654篇 |
2010年 | 3660篇 |
2009年 | 3824篇 |
2008年 | 4142篇 |
2007年 | 4149篇 |
2006年 | 3409篇 |
2005年 | 3141篇 |
2004年 | 2648篇 |
2003年 | 2625篇 |
2002年 | 3171篇 |
2001年 | 3094篇 |
2000年 | 2471篇 |
1999年 | 3229篇 |
1998年 | 2484篇 |
1997年 | 2521篇 |
1996年 | 2339篇 |
1995年 | 1991篇 |
1994年 | 1866篇 |
1993年 | 1614篇 |
1992年 | 1414篇 |
1991年 | 1210篇 |
1990年 | 1111篇 |
1989年 | 1018篇 |
1988年 | 797篇 |
1987年 | 565篇 |
1986年 | 304篇 |
1985年 | 140篇 |
1984年 | 26篇 |
1983年 | 14篇 |
1982年 | 17篇 |
1981年 | 15篇 |
1980年 | 9篇 |
1978年 | 12篇 |
1973年 | 9篇 |
1972年 | 12篇 |
1970年 | 10篇 |
1967年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
Since brain tumors endanger people‘s living quality and even their lives, the accuracy of classification becomes more important. Conventional classifying techniques are used to deal with thosedatasets with characters and numbers. It is difficult, however, to apply them to datasets that include brain images and medical history (alphanumeric data), especially to guarantee the accuracy.For these datasets, this paper combines the knowledge of medical field and improves the traditional decision tree. The new classification algorithm with the direction of the medical knowledge not only adds the interaction with the doctors, but also enhances the quality of classification. The algorithm has been used on real brain CT images and a precious rule has been gained from the experiments. This oaoer shows that the ahzorithm works well for real CT data. 相似文献
982.
Service and information resources are two kinds of major shared resources in virtual enterprises, where, service resources include third party‘s service resources and enterprise‘s legacy service resources, and information resources include database resources and file resources. Since service and information resources have distributed, autonomic, remotely bound as well as some other similar characteristics, an implementation mechanism on managing shared resources based on UDDI are presented. XML instances are used to describe resources authorization information, WSDLbased special XML instance represents information resource metadata, and these XML instancesare referenced by tModel for realizing the purpose of managing shared resources metadata based on UDDI. 相似文献
983.
罗威 《广西民族大学学报》2003,(3)
树立公共关系观念是高校管理主动适应社会主义市场经济发展的迫切需要。公共关系观念的核心是珍视信誉。高校管理必须把握公关形象的客观性、综合性、吸引性、相对性、竞争性等特征 ,遵循方向性、整体性、教育性、激励性、动态性、效益性、双向沟通等原则 ,从而树立良好的高校公关形象。 相似文献
984.
MA Zhibang LI Hongchun XIA Ming KU Tehlung PENG Zicheng Chen Yushu Zhang Zhaofeng 《科学通报(英文版)》2003,48(4)
The Mg/Sr ratio in a stalagmite, which is directly proportional to DMg/Ca, the solid-liquid distribution coefficient of Mg, is proposed as a geochemical thermometer to estimate paleotemperature changes. The paleotemperature changein eastern Beijing over the past 3000 years has been reconstructed by using this thermometer in the stalagmite ZFFS-1 from Jingdong Cave. The records can be divided into two periods: 3000-2000 aBP, cool and wet, the air temperature averaging 9.8℃; and 2000 aBP-present, hot and dry, the air temperature being 1℃ higher than the mean value (11.7℃) of the past 3000 years. During 500-200 aBP, the air temperature was about 1.2℃ lower than that of the present, corresponding to the Little Ice Age in Europe. Like δ18O and δ13C, Mg/Sr (or DMg/Ca) reflects an obviously warming trend of the past 200 years. These results are supported by historic records. 相似文献
985.
Based on the five-year long dynamic tracking and investigation of the peasant households of the Lishu village, the influences by small town construction on the economy and employment of the original peasant households are discussed. On the one hand, small town construction plays a positive role in adjustment of the industrial structure of the original peasant households and in the transfer of their employment towards non-agricultural industries. On the other hand the economic growth of the original peasant households is not so well sustainable, and is so fluctuating. Moreover,the unbalance of income distribution of the said households has been furthered, and small town construction has made the existing labor surplus of the original peasant households more serious, particularly the women labor surplus. 相似文献
986.
The Lattice-Boltzmann method is an effective tool for solving fluid mechanics problems, but there isn’t still a good scheme
to determinate some parameters in Boltzmann equations. In this paper, a technique using evolutionary algorithm to automatically
model Boltzmann equations is introduced. Numerical simulation shows that the designed scheme is fast and efficient.
Biography: Chen Ju-hua ( 1963-), male, Associate professor, research direction: Lattice-Boltzmann method, evolutionary algorithm. 相似文献
987.
Seven novel solid complexes of the first-row transitional metal with L-α-histidine were synthesized, and their compositions were determined. The constant-volume combustion energies of the complexes were measured by a precision rotation bomb calorimeter. The standard molar enthalpies of combustion and the standard molar enthalpies of formation were calculated. The results indicated that the plots of the standard enthalpies of formation against the atomic number of the metal show a regularity of zigzag. 相似文献
988.
论FDI对西部制度变迁的影响及对策 总被引:5,自引:0,他引:5
本文首先对我国西部地区利用FDI的现状进行了描述 ,然后运用回归分析的方法分析了FDI和制度变迁的关系 ,指出FDI是影响区域制度变迁的重要因素 ,FDI在区域分布上的不均衡严重制约着西部地区制度变迁的进程。西部地区应该加快体制改革的步伐 ,改善投资环境 ,吸引FDI ,进而通过FDI带动西部地区制度变迁的进程 ,最终形成FDI和制度变迁相互推动、相互促进的良性循环。 相似文献
989.
中小企业理论述评——兼论西部实施中小企业战略的可行性 总被引:2,自引:0,他引:2
本文从缝隙生存、交易成本和创业理论角度对中小企业存在合理性进行阐述 ,兼论西部实施中小企业战略的可行性 相似文献
990.
软件开发和科研项目有很多相似之处 ,目前软件开发实践中已经形成了很多行之有效的管理方法 ,而科研管理在这方面还比较欠缺。本文介绍了软件开发中两种最重要的方法 -项目管理和过程管理 ,并分析了这两种方法在科研管理中应用的可行性和作用 相似文献