全文获取类型
收费全文 | 20919篇 |
免费 | 4413篇 |
国内免费 | 105篇 |
专业分类
财政金融 | 2101篇 |
工业经济 | 2238篇 |
计划管理 | 3531篇 |
经济学 | 5030篇 |
综合类 | 1751篇 |
运输经济 | 148篇 |
旅游经济 | 97篇 |
贸易经济 | 4534篇 |
农业经济 | 3222篇 |
经济概况 | 2769篇 |
信息产业经济 | 2篇 |
邮电经济 | 14篇 |
出版年
2024年 | 141篇 |
2023年 | 482篇 |
2022年 | 469篇 |
2021年 | 545篇 |
2020年 | 759篇 |
2019年 | 1121篇 |
2018年 | 885篇 |
2017年 | 991篇 |
2016年 | 869篇 |
2015年 | 948篇 |
2014年 | 1226篇 |
2013年 | 1523篇 |
2012年 | 1919篇 |
2011年 | 2126篇 |
2010年 | 1844篇 |
2009年 | 1466篇 |
2008年 | 1343篇 |
2007年 | 1210篇 |
2006年 | 1204篇 |
2005年 | 1105篇 |
2004年 | 751篇 |
2003年 | 480篇 |
2002年 | 341篇 |
2001年 | 297篇 |
2000年 | 170篇 |
1999年 | 188篇 |
1998年 | 97篇 |
1997年 | 102篇 |
1996年 | 73篇 |
1995年 | 40篇 |
1994年 | 53篇 |
1993年 | 79篇 |
1992年 | 91篇 |
1991年 | 105篇 |
1990年 | 42篇 |
1989年 | 50篇 |
1988年 | 47篇 |
1987年 | 30篇 |
1985年 | 25篇 |
1984年 | 21篇 |
1983年 | 15篇 |
1982年 | 24篇 |
1979年 | 10篇 |
1978年 | 10篇 |
1976年 | 11篇 |
1975年 | 10篇 |
1973年 | 9篇 |
1972年 | 8篇 |
1969年 | 9篇 |
1963年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
南方丘陵区新增耕地质量空间特征研究*——以江西省宜春市为例 总被引:2,自引:0,他引:2
[目的]粮食安全的根本是在耕地,关键在于耕地质量。目前新增耕地主要源于土地开发项目、城乡建设用地增减挂钩土地复垦项目等,这些新增耕地需要对其开展耕地质量等别评定工作,了解新增耕地的质量状况,分析其空间特征,这对落实国家耕地保护制度、开展农村土地整治工作等具有重要作用。[方法]文章以南方典型丘陵区域——江西省宜春市作为研究区域,在新增耕地质量评价的基础上,运用地统计学、景观生态学、Arcgis空间分析技术和典型相关分析方法,研究宜春市新增耕地质量的空间特征,掌握耕地质量等别的分布规律,了解耕地质量的影响因素,为制定合理的耕地资源利用与保护政策提供依据。[结果](1)Moran′s I值结果表明宜春市2014年新增耕地利用质量在空间分布上的空间自相关性最强,而耕地自然质量空间自相关性最弱。(2)景观破碎度指数结果表明优、高等别的新增耕地质量破碎度大于中、低等别的; 多样性指数结果表明新增耕地质量多样性指数比较大; 优势度指数结果表明新增耕地质量等别优势度指数比较小,与多样性指数结果相呼应; 均匀度指数结果表明,新增耕地质量等别均匀度指数相差不大,新增耕地质量等别比较均匀。(3)质心结果表明2013—2014年间宜春市新增耕地质量的格局整体上是向西南方向变化。[结论]宜春市新增耕地质量不高; 新增耕地的利用水平差异性较小,自然本底状况差异较大; 新增耕地质量等别类型多,各质量等别类型耕地均有增加,耕地质量参差不齐,较高等地的新增耕地相对低等地而言更破碎化; 新增耕地的开发格局向着西南方向移动; 该研究为南方丘陵区的新增耕地保护提供了一定的参考依据。 相似文献
2.
3.
传统粒子滤波(PF)直接采用状态转移先验分布作为重要性密度函数来近似后验概率密度函数,使得后验概率密度函数未包含量测信息。针对此问题,提出了一种改进高阶容积粒子滤波(CPF)的系统状态估计算法。算法采用七阶正交容积卡尔曼滤波(7th-CQKF)对PF的粒子进行传递,使得先验分布更新阶段融入最新量测信息;通过7th-CQKF设计重要性密度函数,提高对状态后验概率密度的逼近程度;通过反比例函数计算粒子权重,突出大噪声粒子与小噪声粒子权重差别,提高粒子有效性。仿真结果表明,改进高阶容积粒子滤波的估计精度高于容积粒子滤波(CPF)。 相似文献
4.
5.
Kamalesh Kumar Giacomo Boesso Rishtee Batra Jun Yao 《Business Strategy and the Environment》2021,30(5):2354-2366
Drawing upon the research in institutional theory and comparative capitalism, the present study investigates how cross-national differences in the political, business, and economic institutional contexts of the United States, Italy, and Japan are associated with the ways in which companies in each of these countries prioritize and engage in their stakeholder engagement activities (SEAs). Using Porter and Kramer's framework, which classifies corporate social responsibility (CSR) activities as falling into four categories (good citizenship, mitigating harm from value chain, transforming value chain activities, and strategic philanthropy), we investigate how companies in the United States, Japan, and Italy prioritize and engage in these four SEAs. An analysis of data collected from 340 companies across these countries reveals that while companies in each of these three countries undertake the four types of SEAs, the prioritization and prevalence of the four types of SEAs vary from one country to the other, in ways that align with the prevailing institutional contexts of each country. The results contribute to a more nuanced understanding of why and how companies' approaches to CSR differ across countries. From a practitioner's perspective, the findings highlight the cultural specificity of CSR, implying that despite the global nature of CSR, the implementation of CSR needs to be tailored to a country's context. 相似文献
6.
This paper develops a platform‐based influencing factors model which considers value perception, risk prevention measure, non‐default experience, trust and incentive gap, to better examine the impact of platforms on investors’ satisfaction and lending intention based on the Chinese market. The results reveal that the first four factors positively influence the satisfaction of the investors, while the incentive gap has a negative impact, and there is a positive association between investors’ satisfaction and lending intention. Some specific features of China’s online lending market are identified, which provides valuable insights for online lending platforms and the government. 相似文献
7.
Jing Wang Vangelis Tsiligiris Robert Hartley 《Accounting Education: An International Journal》2019,28(3):221-238
This paper evaluates ways of instilling project management skills into accounting-based learning by the use of an iterative A3 planner to plan, monitor and review assignment progress. The application of an A3 planner to facilitate a project-based learning (PBL) group assignment in undergraduate accounting education has been critically evaluated in terms of both the student and tutor experience. The study uses a mix of qualitative and quantitative data. Quantitative data assisting exploration of perceptions were collected through 100 undergraduate students. A series of focus group discussions were carried out to investigate students’ engagement and tutors’ teaching experiences regarding the adoption of the A3 planner. The results suggest that the A3 planner promotes active planning and effective management of a PBL group assignment. It makes students’ thought processes more visible thereby facilitating and enhancing the tutoring/mentoring process. Moreover a more interactive and transparent approach by doing assignment via the use of an iterative A3 planner has ensured more feedback points and action based efficiency in the doing approach for learners. 相似文献
8.
Day-Yang Liu Hsin-Hsin Yao Wen-Min Lu Cheng-Hsien Lin 《Managerial and Decision Economics》2020,41(6):1020-1032
In this study, an epsilon-based network data envelopment analysis is employed to construct assessment mechanisms for government performance. Moreover, performance indicators of two dimensions of tax collection efficiency and financial effectiveness are measured. We propose a vector autoregression model in which all economic variables are regarded as dependent variables to address the disadvantages of traditional regression model. The conclusions are as follows: (a) measures of tax collection efficiency deteriorated, whereas those of financial effectiveness improved. (b) In an impulse response analysis of the model, an increase in government-published land values produced significantly increased tax collection efficiency. 相似文献
9.
Luby变换(Luby Transform,LT)码作为信道编码应用于电力线通信(Power Line Communication,PLC),可实现电信号的可靠传输。度分布对LT码编译码性能的影响至关重要。为了得到更优的度分布,首先调整二进制指数分布(Binary Exponential Distribution,BED)中的度数比例,获得一种译码性能更优的改进的二进制指数分布(Improved BED,IBED)。然后,根据IBED在冗余度较小时译码成功率高,而冗余度增大后鲁棒孤子分布(Robust Soliton Distribution,RSD)的译码性能表现更佳的特点,通过求和归一化的方式将IBED与RSD两种度分布的优势进行有机结合,提出一种新型二进制鲁棒孤子分布(Binary RSD,BRSD)。仿真结果表明,与其他方法及传统的RSD相比,采用新度分布进行LT编码,可明显降低译码开销,并节约编译码耗时。将新型度分布应用于基于LT码的PLC系统中,能有效地抑制PLC信道中各种噪声对电信号的干扰,并提高通信效率。 相似文献
10.
ABSTRACTThe escalating U.S.–China trade conflicts have increasingly shadowed the outlook of the world economy. The Trump administration aims to achieve its strategic goals including reducing current account deficits, promoting the U.S. manufacturing sector, and curbing Chinese high-tech industries by waging the trade war against China. This paper argues that the current account deficits and the declining manufacturing sector in the U.S. are mainly driven by its internal structural factors, such as low saving rates, high labor costs, and rising service sector, rather than by the import competition from China. Moreover, the trade war further deteriorates the U.S. current account deficits and erode its comparative advantage, and it forces China to invest more in technological innovation and human capital, and thus promote its progress in high-tech industries. Thus, the U.S. will not be able to achieve its strategical goals and eventually lose the trade war. 相似文献