全文获取类型
收费全文 | 10880篇 |
免费 | 265篇 |
国内免费 | 550篇 |
专业分类
系统科学 | 371篇 |
丛书文集 | 364篇 |
教育与普及 | 299篇 |
理论与方法论 | 32篇 |
现状及发展 | 75篇 |
研究方法 | 44篇 |
综合类 | 10506篇 |
自然研究 | 4篇 |
出版年
2024年 | 87篇 |
2023年 | 126篇 |
2022年 | 205篇 |
2021年 | 243篇 |
2020年 | 117篇 |
2019年 | 51篇 |
2018年 | 103篇 |
2017年 | 121篇 |
2016年 | 123篇 |
2015年 | 250篇 |
2014年 | 361篇 |
2013年 | 300篇 |
2012年 | 335篇 |
2011年 | 404篇 |
2010年 | 371篇 |
2009年 | 400篇 |
2008年 | 480篇 |
2007年 | 477篇 |
2006年 | 385篇 |
2005年 | 389篇 |
2004年 | 315篇 |
2003年 | 242篇 |
2002年 | 270篇 |
2001年 | 288篇 |
2000年 | 312篇 |
1999年 | 585篇 |
1998年 | 577篇 |
1997年 | 584篇 |
1996年 | 523篇 |
1995年 | 454篇 |
1994年 | 408篇 |
1993年 | 321篇 |
1992年 | 313篇 |
1991年 | 297篇 |
1990年 | 221篇 |
1989年 | 241篇 |
1988年 | 184篇 |
1987年 | 123篇 |
1986年 | 65篇 |
1985年 | 17篇 |
1984年 | 6篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1969年 | 4篇 |
1967年 | 2篇 |
1964年 | 1篇 |
1957年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Atomicity is necessary for reliable and secure electronic commerce transaction and to guarantee the participants' interests. An atomic and efficient e-cash (electronic cash) transaction protocol based on the classical e-cash scheme is presented. The delivery of digital goods is incorporated into the process of payment in the protocol. Apart from ensuring all three levels of atomicity, the novel protocol features high efficiency and practicability with unfavorable strong assumption removed. Furthermore, the proposed protocol provides non-repudiation proofs for any future disputes. At last, analysis of the atomicity and efficiency is illustrated. 相似文献
52.
For a class of generalized Feistel block ciphers,an explicit formula for the minimum numbers of linearly active S-boxes of any round r is presented. 相似文献
53.
采用有限元法计算了E型方杯的挠度及应力分布,并从应力差计算出了压敏电阻设置的最佳位置. 相似文献
54.
55.
56.
This paper proposes a unified clutter model incorporating the effects of range walk and array rotation for space-time adaptive processing (STAP) in airborne multi-channel early-warning radar. Based on this clutter model, STAP performance is then analyzed from the perspective of covariance matrix tapering (CMT). For STAP performance degradation due to array rotation, a determinate compensation method is proposed based on the CMT method. Numerical examples are provided to verify the analysis and the proposed compensation method. 相似文献
57.
<正> In this paper,an equivalency condition of nonsingularity in nonlinear semidefinite programming,which can be viewed as a generalization of the equivalency condition of nonsingularity for linearsemidefinite programming,is established under certain conditions of convexity. 相似文献
58.
Coordinated Bayesian optimal approach for the integrated decision between electronic countermeasure and firepower attack 下载免费PDF全文
The coordinated Bayesian optimization algorithm (CBOA) is proposed according to the characteristics of the function independence, conformity and supplementary between the electronic countermeasure (ECM) and the firepower attack systems. The selection criteria are combinations of probabilities of individual fitness and coordinated degree and can select choiceness individual to construct Bayesian network that manifest population evolution by producing the new chromosome. Thus the CBOA cannot only guarantee the effective pattern coordinated decision-making mechanism between the populations, but also maintain the population multiplicity, and enhance the algorithm performance. The simulation result confirms the algorithm validity. 相似文献
59.
<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
60.
车辆组合导航定位技术 总被引:14,自引:1,他引:14
介绍车辆导航定位及其组合导航定位技术.组合导航利用现代信息融合技术,实现对车辆组合导航的准确定位,具有全方位、全天候、自主式定位功能.着重研究了GPS/GLNOASS/MM和GPS/DR/MM三组合导航定位及跑车试验分析.跑车试验表明,车辆组合导航定位精度及可靠性比单独GPS导航定位有所提高,车辆运行效率和安全性大大改善,提高了通行能力,有效地缓解了交通拥挤状况,从而为实现交通管理"自动化"以及车辆行驶"智能化"提供了可靠的保证. 相似文献