全文获取类型
收费全文 | 15268篇 |
免费 | 878篇 |
国内免费 | 712篇 |
专业分类
系统科学 | 1545篇 |
丛书文集 | 252篇 |
教育与普及 | 197篇 |
理论与方法论 | 310篇 |
现状及发展 | 914篇 |
研究方法 | 38篇 |
综合类 | 13600篇 |
自然研究 | 2篇 |
出版年
2024年 | 41篇 |
2023年 | 72篇 |
2022年 | 182篇 |
2021年 | 177篇 |
2020年 | 127篇 |
2019年 | 72篇 |
2018年 | 819篇 |
2017年 | 838篇 |
2016年 | 566篇 |
2015年 | 310篇 |
2014年 | 384篇 |
2013年 | 371篇 |
2012年 | 659篇 |
2011年 | 1376篇 |
2010年 | 1233篇 |
2009年 | 937篇 |
2008年 | 1090篇 |
2007年 | 1292篇 |
2006年 | 464篇 |
2005年 | 499篇 |
2004年 | 495篇 |
2003年 | 547篇 |
2002年 | 664篇 |
2001年 | 574篇 |
2000年 | 391篇 |
1999年 | 455篇 |
1998年 | 263篇 |
1997年 | 277篇 |
1996年 | 275篇 |
1995年 | 221篇 |
1994年 | 226篇 |
1993年 | 201篇 |
1992年 | 171篇 |
1991年 | 140篇 |
1990年 | 124篇 |
1989年 | 115篇 |
1988年 | 106篇 |
1987年 | 59篇 |
1986年 | 31篇 |
1985年 | 8篇 |
1984年 | 4篇 |
1967年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Design of an anti-jamming GPS receiver based on orthogonal projection method 总被引:2,自引:0,他引:2 下载免费PDF全文
Code delay and Doppler shifted frequency could not be captured by using the conventional GPS receiver in strong interference environments because the received GPS signals which traveled a long distance are very weak. An anti-jamming GPS receiver is proposed. The interferences in the received signals are cancelled by using subspace projecting technique, and the resulting interference-free signals are processed by a weight vector which maximizes the signal-to-noise ratio. Simulation is conducted, and the resu... 相似文献
92.
Lijie Zhang Jianguo Huang Yong Jin Yunshan Hou Min Jiang Qunfei Zhang .College of Marine Northwestern Polytechnical University Xi’an P.R.China .Yichang Testing Technique Research Institute Yichang 《系统工程与电子技术(英文版)》2010,21(2):186-190
A new monostatic army system taking advantage of diverse waveforms to improve the performance of underwater target localization is proposed.Unlike the coherent signals between different elements in common active array,the transmitted signals from different elements here are spatially orthogonal waveforms which allow for array processing in the transit mode and result in an extension of array aperture.The mathematical derivation of Capon estimator for this sonar system is described in detail.And the performance of this orthogonal-waveform based sonar is analyzed and compared with that of its phased-array counterpart by water tank experiments.Experimental results show that this sonar system could achieve 12 dB-15 dB additional array gain over its phased-array counterpart,which means a doubling of maximum detection range.Moreover,the angular resolution is significantly improved at lower SNR. 相似文献
93.
<正>Autocorrelation is prevalent in continuous production processes,such as the processes in the chemical and pharmaceutical industries.With the development of measurement technology and data acquisition technology,sampling frequency is getting higher and the existence of autocorrelation cannot be ignored.This paper analyzes five estimation schemes of process capability for autocorrelated data.Comparisons among these schemes are discussed for small sample and large sample.In conclusion,this paper gives a procedure of process capability analysis for autocorrelated data. 相似文献
94.
Patent documents are unique external sources of information that reveal the core technology underlying new inventions.Patents also serve as a strategic data source that can be mined to discover state-of-the-art technical development and subsequently help guide R&D investments.This research incorporates an ontology schema to extract and represent patent concepts.A clustering algorithm with non-exhaustive overlaps is proposed to overcome deficiencies with exhaustive clustering methods used in patent mining and technology discovery.The non-exhaustive clustering approach allows for the clustering of patent documents with overlapping technical findings and claims,a feature that enables the grouping of patents that define related key innovations.Legal advisors can use this approach to study potential cases of patent infringement or devise strategies to avoid litigation.The case study demonstrates the use of non-exhaustive overlaps algorithm by clustering US and Japan radio frequency identification (RFID) patents and by analyzing the legal implications of automated discovery of patent infringement. 相似文献
95.
The relationship between tacit knowledge and informal networks has not been fully explored.Tacit knowledge cannot be well managed directly,because it is deeply embedded in individual actions and experiences.This study proposes an approach to managing informal networks as a new middle way to facilitate the sharing and transferring of tacit knowledge,owing to the fact that tacit knowledge is mostly shared and transferred through informal networks.To support the idea of the approach,an empirical case study of applying the approach to management of a large scientific project is also included.Our findings suggest that informal networks play essential roles for management of tacit knowledge,and thus good management of informal networks can lead to efficient sharing and transferring of tacit knowledge. 相似文献
96.
Power-Based Arbitrary Decisional Actions in the Resolution of MIS Project Issues: A Project Manager's Action Research Perspective 总被引:1,自引:0,他引:1
As a management information systems (MIS) project manager and an action researcher, the author examined, over time, the influence on information system development (ISD) of the informal sociopolitical organizational actions. The paper reports two cases of action research findings concerning the effect on ISD project implementation processes of power-based arbitrary decisional actions in bureaucratic environments. The research focused on the relationship of such unilateral actions to the interconnected subprocesses of deliberate and conscious attempts by the ISD project members to define and resolve system implementation issues. A suggested conceptual framework for the issue-resolution processes (IRP's) and obstacle-coping processes (OCP's) is based on the author's IRP/OCP-related behavioral constructs and theoretical models dealing with soft-systems issues, especially appreciative system theory and soft-systems methodology, and innovative flexible, "complementarist" (Sinn, 1998) or pluralist problem-solving approaches. 相似文献
97.
Red Qingsheng 《系统工程与电子技术(英文版)》2000,11(3)
1. INTSODUCTIONThe common illteger programming (lP) is a mathematical model which is designed to find aset of non-negative variables to medmize (or minimize) a nonlinear objective function whilesatisfying a set of constraints under integer restrictions of variables. An lP model with somevariables reqllired to be real is a mixed integer programming (MIP).The history of solving lP/MIP problems is not very old. According to reference [1], ageneral method for solvillg such problems may not… 相似文献
98.
99.
确定事例特征权值的方法研究 总被引:7,自引:0,他引:7
吴良刚 《系统工程理论与实践》2000,20(10):89-92
针对事例特征权值的确定问题 ,提出了 Delphi和 AHP相结合的权值确定方法 ,以及二次规划模型权值确定法和信用统计权值确定法 .这些方法在事例特征权值的确定中 ,有助于减少主观性 ,增加客观性 . 相似文献
100.
优序法在管理成果评价中的应用 总被引:4,自引:0,他引:4
在对管理成果进行评价时 ,首先要建立指标体系 ,而在这些指标当中有的可以定量描述 ,有的只能定性来描述 ,所以在评价时应当将定性和定量指标进行综合考虑。优序法就是通过对多目标决策问题进行两两相对比较 ,最后给出全部方案的优序排序。此方法应用简单 ,既能处理定量问题 ,又能处理定性问题。在建立管理成果指标体系的基础上 ,利用优序法 ,给出了管理成果评价方法。 相似文献