全文获取类型
收费全文 | 1647篇 |
免费 | 191篇 |
国内免费 | 13篇 |
专业分类
财政金融 | 88篇 |
工业经济 | 99篇 |
计划管理 | 765篇 |
经济学 | 111篇 |
综合类 | 103篇 |
运输经济 | 69篇 |
旅游经济 | 14篇 |
贸易经济 | 447篇 |
农业经济 | 54篇 |
经济概况 | 100篇 |
信息产业经济 | 1篇 |
出版年
2024年 | 2篇 |
2023年 | 38篇 |
2022年 | 31篇 |
2021年 | 46篇 |
2020年 | 82篇 |
2019年 | 48篇 |
2018年 | 47篇 |
2017年 | 48篇 |
2016年 | 63篇 |
2015年 | 89篇 |
2014年 | 146篇 |
2013年 | 122篇 |
2012年 | 148篇 |
2011年 | 153篇 |
2010年 | 126篇 |
2009年 | 71篇 |
2008年 | 123篇 |
2007年 | 134篇 |
2006年 | 93篇 |
2005年 | 76篇 |
2004年 | 49篇 |
2003年 | 32篇 |
2002年 | 23篇 |
2001年 | 17篇 |
2000年 | 12篇 |
1999年 | 8篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 3篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1986年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有1851条查询结果,搜索用时 46 毫秒
1.
Predicting consumption behavior is very important for adjusting supplier production plans and enterprise marketing activities. Conventional statistical methods are unable to accurately predict green consumption behavior because it is characterized by multivariate nonlinear interactions. The paper proposes an optimized fruit fly algorithm (FOA) and extreme learning machine (ELM) model for consumption behavior prediction. First, to address the problem of uneven search direction of FOA leading to insufficient search ability and low efficiency, the paper proposes a sector search mechanism instead of a random search mechanism to improve the global search ability and convergence speed of FOA. Second, to address the issue that the initial weights and hidden layer bias values of the ELM are randomly generated, which affects the learning efficiency and generalization of the ELM, the paper uses an improved FOA to optimize the weights and bias values of ELM for improving the prediction accuracy. Taking the green vegetable consumption behavior of Beijing residents as an example, the results show the optimization of the initial weight and threshold of ELM by the GA, PSO, FOA, and SFOA, the prediction accuracy of the GA-ELM, PSO-ELM, FOA-ELM, and SFOA-ELM models all surpass those of ELM. Compared with BPNN, GRNN, ELM, GA-ELM, PSO-ELM, and FOA-ELM models, the RMSE value of SFOA-ELM was decreased by 9.45%, 8.40%, 11.89%, 5.84%, 2.22%, and 2.69%, respectively. These findings demonstrate the effectiveness of the SFOA-ELM model in green consumption behavior prediction and provide new ideas for the accurate prediction of consumption behaviors of other green products with similar characteristics. 相似文献
2.
3.
《International Journal of Forecasting》2021,37(4):1399-1425
Dynamic factor models have been the main “big data” tool used by empirical macroeconomists during the last 30 years. In this context, Kalman filter and smoothing (KFS) procedures can cope with missing data, mixed frequency data, time-varying parameters, non-linearities, non-stationarity, and many other characteristics often observed in real systems of economic variables. The main contribution of this paper is to provide a comprehensive updated summary of the literature on latent common factors extracted using KFS procedures in the context of dynamic factor models, pointing out their potential limitations. Signal extraction and parameter estimation issues are separately analyzed. Identification issues are also tackled in both stationary and non-stationary models. Finally, empirical applications are surveyed in both cases. This survey is relevant to researchers and practitioners interested not only in the theory of KFS procedures for factor extraction in dynamic factor models but also in their empirical application in macroeconomics and finance. 相似文献
4.
维护方式选择是维护管理中的重要工作之一,合理的维护方式既能达到保障设备的稳定运行,又能同时兼顾其它各个方面的要求。由于对维护方式的评价涉及多个部门、人员和属性,有些指标只是一个模糊的概念,因而采用模糊多属性群决策的方法对维护方式进行优先抉择。本文结合A公司的设备维护方式选择问题,尝试使用模糊多属性群决策折衷算法求解最佳的维护方式。 相似文献
5.
《Socio》2019
We study a location-allocation-routing problem for distribution of the injured in a disaster response scenario, considering a three-type transportation network with separate links. A circle-based approach to estimate the impacts of the disaster is presented. After formulating relations for computing the percentage of the injured, the destruction percentage and the damage-dependent travel times, the problem is formulated as an integer nonlinear program. We utilize a genetic algorithm and a discrete version of the imperialist competitive algorithm for solving large problems. An empirical study focused on earthquakes in Tabriz, Iran, illustrates applicability of the proposed model and performance of the proposed algorithms. 相似文献
6.
量子算法和量子计算机对装备保障信息网络的认证方案已构成严重的潜在威胁。针对当前装备保障信息网络身份认证方案无法抵抗量子计算机攻击、认证效率相对较低的问题,引入格理论的本原格抽样算法和双峰高斯抽样技术,提出了装备保障信息网络在量子环境下安全且快速的身份认证方案,给出了方案的正确性、安全性的理论证明以及方案运行效率的比较分析。结果表明,基于随机预言机证明模型,该方案在小整数解问题困难性假设下达到了适应性选择身份和选择消息攻击的存在性不可伪造性;在保证安全的前提下,新方案在私钥提取阶段和身份认证阶段的运行效率均高于已有的几个同类格基身份认证方案。这为提高我国装备保障信息网络安全认证能力提供了新的思路和方法。 相似文献
7.
针对脉冲噪声下恒模算法(Constant Modulus Algorithm,CMA)失败的问题,通过分析脉冲噪声的影响,提出了一种基于最小均方(Least Mean Square,LMS)准则的对数型恒模算法(Logarithmic-type CMA,LT-CMA)。LT-CMA利用对数函数的非线性变换特性自适应地抑制强脉冲噪声对误差函数的影响,并且利用l2-范数进行信号归一化处理以增强算法的稳健性。仿真结果表明,所提出的LT-CMA可以适应于高斯噪声环境和脉冲噪声环境;与经典自适应均衡算法相比,在收敛速度和稳健性两方面上,所提出的LT-CMA都有显著的提升。 相似文献
8.
Ulrik Kihlbom 《Journal of Risk Research》2018,21(2):222-235
A conceptual truth about risks is that they involve a possible and future adverse effect or a negative value of some kind. The genetic risks that individuals may face in the health care setting differ in some crucial respects to other kind of risks. The aims of this paper are to analyse the notion of value in the context of genetic risk in the setting of health care, and to suggest a conception of the evaluative aspect of genetic risk that is fruitful for genetic risk information. Two influential and relevant approaches to value, preferentialism and the capability approach, are discussed in the light of certain distinctive features of genetic risk and a third, a sensibility theory of value is suggested. According to this view, the concept of risk is a so-called ‘thick’ evaluative concept that has both a world-guiding function as well as an action-guiding or normative function. It is argued that this provides a more promising way to think about genetic risks in the clinical setting. 相似文献
9.
10.
We first employ β-conditional convergence and log t regression tests based on nonlinear time-varying factor model and club clustering algorithm to analyze the convergence characteristics of the development level of Internet finance in 335 prefecture-level cities in China. The result of log t regression test illustrates that there is no convergence as a whole in the development level of China's Internet finance. However, seven convergence clubs and a divergent group have been formed, and the development level and growth rate of Internet finance among these convergence clubs have shown obvious differences. Moreover, we also employ the Ordered Probit to explore the formation mechanism of the convergence clubs. The results reveal that the regions with a higher level of economic development, traditional financial development, economic openness and Internet development are more inclined to converge in a club with a higher Internet finance development level. Alternatively, the regions that are interfered with more by the government or that have a lower degree of marketization, tend to converge in a club with a lower level. Finally, according to the conclusions, we propose corresponding policy recommendations for promoting the regional coordinated development of China's Internet finance. 相似文献