全文获取类型
收费全文 | 981篇 |
免费 | 10篇 |
国内免费 | 34篇 |
专业分类
系统科学 | 20篇 |
丛书文集 | 2篇 |
教育与普及 | 3篇 |
理论与方法论 | 12篇 |
现状及发展 | 206篇 |
研究方法 | 131篇 |
综合类 | 625篇 |
自然研究 | 26篇 |
出版年
2021年 | 4篇 |
2020年 | 5篇 |
2019年 | 5篇 |
2018年 | 14篇 |
2017年 | 12篇 |
2016年 | 8篇 |
2015年 | 13篇 |
2014年 | 18篇 |
2013年 | 18篇 |
2012年 | 67篇 |
2011年 | 95篇 |
2010年 | 37篇 |
2009年 | 24篇 |
2008年 | 52篇 |
2007年 | 66篇 |
2006年 | 52篇 |
2005年 | 63篇 |
2004年 | 39篇 |
2003年 | 64篇 |
2002年 | 53篇 |
2001年 | 40篇 |
2000年 | 42篇 |
1999年 | 20篇 |
1996年 | 4篇 |
1992年 | 10篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 10篇 |
1988年 | 9篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1985年 | 9篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1977年 | 10篇 |
1976年 | 5篇 |
1975年 | 9篇 |
1974年 | 5篇 |
1973年 | 9篇 |
1972年 | 3篇 |
1971年 | 9篇 |
1970年 | 9篇 |
1969年 | 7篇 |
1968年 | 5篇 |
1967年 | 7篇 |
1966年 | 5篇 |
1965年 | 7篇 |
排序方式: 共有1025条查询结果,搜索用时 15 毫秒
111.
A number of IDSs have been proposed for a networked or distributed environment. A modified D-IDS using federated peer-to-peer architecture, MCR (Multicast Reflector) and modified shaker protocol were proposed. The suggested scheme can be implemented easily and performs the information sharing between low-level IDS agents. As all users within a group monitor each other's, the common control server can perform detect intrusions with less cost and support the detection of the inside intruders. 相似文献
112.
Tool wear, chatter vibration, chip breaking and built-up edge are main phenomena to be monitored in modern manufacturing processes, which are considered as important factors to the quality of products.They are closely related to the cutting parameters, which are to be selected in manufacturing process.However, it is very difficult to measure directly the cutting quality based on on-line monitoring.In this study, the relationship between the cutting parameters and cutting quality is analyzed.A Radical Basis Function (RBF) neural network based on-line quality recognition scheme is also presented, which monitors the level of surface roughness.The experimental results reveal that the RBF neural network has a high prediction success rate. 相似文献
113.
By adopting majority rule within a renormalization group approach, we can show that the strength of inter-group interaction in a social system either grows or shrinks monotonically with increasing group size, depending on the initial coupling strength of individuals in the group. This contrasts with the findings of previous studies in which the strength of the interaction grows with group size regardless of the initial strength. Our approach clearly demonstrates that the phenomena of crowd psychology, such as an extreme anti-reaction between different ethnic or ideological groups, could be a consequence of the many-particle nature of social systems when the initial strength of the interaction is larger than a critical value. The effect of neutral opinion holders is critically examined using the spin-one Ising model. The critical size of the population of neutral opinion holders, that can prevent crowd polarization, depends on the block spin rule. 相似文献
114.
Herbert K.H. Lee 《Journal of Classification》2007,24(1):53-70
Feedforward neural networks are a popular tool for classification, offering a method for fully flexible modeling. This paper
looks at the underlying probability model, so as to understand statistically what is going on in order to facilitate an intelligent
choice of prior for a fully Bayesian analysis. The parameters turn out to be difficult or impossible to interpret, and yet
a coherent prior requires a quantification of this inherent uncertainty. Several approaches are discussed, including flat
priors, Jeffreys priors and reference priors. 相似文献
115.
立成表是古历中推算日、月、五星运动时,为简化计算所造的表.元代<授时历>是中国古代历法的巅峰之作,可惜<元史*历志>中没有收录它的立成表部分.在韩国保存有署名王恂的<授时历立成>奎章阁本1册.该文对这册立成表的内容进行了分析和研究,证明它确是在元代所做,其刊行时间为朝鲜世宗时代,具有珍贵的史料价值;而且,其中出现的四暗星内容对于<授时历>本身的历法内容是一个重要的补充. 相似文献
116.
R. E. Lee Jr E. H. Bryant J. G. Baust 《Cellular and molecular life sciences : CMLS》1985,41(9):1191-1192
Summary After 7 days of space flight house flies,Musca domestica, exhibited similar longevity, but a reduction in reproductive output as compared to earthbound controls. This reduction was not observed in later generations. These data suggest that space flight directly alters the rate of ovarian development, but that this effect is not genetically transmitted.Acknowledgment. We thank Todd E. Nelson, student participant in the Space Shuttle Student Involvement Project, John T. Jackson, NASA/Johnson Space Center, and James R. Peterson, Honeywell, Inc. for providing us with the flies and information related to the in-flight experiments. 相似文献
117.
Organization of microtubules in dendrites and axons is determined by a short hydrophobic zipper in microtubule-associated proteins MAP2 and tau 总被引:35,自引:0,他引:35
Here we report that the microtubule-associated proteins MAP2 and tau share two separable functional domains. One is the microtubule-binding site which serves to nucleate microtubule assembly; the second is a short C-terminal alpha-helical sequence which can crosslink microtubules by means of a hydrophobic zipper interaction into dense stable parallel arrays characteristic of axons or dendrites. Thus, interactions between molecules of a single type are capable of drastically reorganizing microtubules and completely suppressing their dynamic properties. 相似文献
118.
Quay crane and yard truck scheduling are two important subproblems in container terminal operations which have been studied separately in previous research. This paper proposes a new problem for the integrated quay crane and yard truck scheduling for inbound containers. The problem is formulated as a mixed integer programming (MIP) model. Due to the intractability, a genetic algorithm (GA) and a modified Johnson's Rule-based heuristic algorithm (MJRHA) are used for the problem solution. In addition, two closed form lower bounds are given to evaluate the solution accuracy. Computational experiments show that the solution algorithm can efficiently handle the scheduling problem and that the integrated methods are very useful. 相似文献
119.
A model is developed for convex-set valued data,which are the Minkowski sum of aconvex parameter set and a convex noise set.This model is generalized to include location and scaleparameters.A further generalization results in a model for convex sets which is analogous to aone-way analysis of variance models.In each case,estimators of the parameters are given which,under certain conditions,are shown to be consistent.Data generated from the model and theestimators are studied.An outlier detection method is examined. 相似文献
120.