首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   32098篇
  免费   783篇
  国内免费   6篇
财政金融   4486篇
工业经济   1754篇
计划管理   4297篇
经济学   5889篇
综合类   281篇
运输经济   192篇
旅游经济   368篇
贸易经济   4130篇
农业经济   1263篇
经济概况   2988篇
水利工程   7161篇
信息产业经济   4篇
邮电经济   74篇
  2021年   256篇
  2020年   387篇
  2019年   578篇
  2018年   739篇
  2017年   744篇
  2016年   783篇
  2015年   503篇
  2014年   781篇
  2013年   2951篇
  2012年   1235篇
  2011年   1183篇
  2010年   887篇
  2009年   967篇
  2008年   1050篇
  2007年   1100篇
  2006年   1061篇
  2005年   914篇
  2004年   866篇
  2003年   599篇
  2002年   549篇
  2001年   647篇
  2000年   554篇
  1999年   529篇
  1998年   576篇
  1997年   537篇
  1996年   529篇
  1995年   458篇
  1994年   480篇
  1993年   459篇
  1992年   481篇
  1991年   484篇
  1990年   460篇
  1989年   367篇
  1988年   387篇
  1987年   371篇
  1986年   340篇
  1985年   477篇
  1984年   461篇
  1983年   431篇
  1982年   405篇
  1981年   403篇
  1980年   430篇
  1979年   420篇
  1978年   373篇
  1977年   306篇
  1976年   327篇
  1975年   283篇
  1974年   265篇
  1973年   278篇
  1972年   201篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
83.
84.
85.
The historic focus of new products research has been on the ability of new products to enhance the profitability and competitive position of the innovating firm. In this article, Timothy Devinney shows that there exists an overlooked and potentially significant side effect associated with new product innovations: financial risk changes. He reports that significant financial risk changes occurred in approximately 50% of the new product announcements he examined. The magnitude of these financial risk changes translates into overestimates or underestimates of the firm's cost of capital by 17% to 18% and is strongly and positively related to the size of the firm and the firm's new product innovation activity.  相似文献   
86.
87.
Summary A sequential testing procedure called 2-SPRT for the meanμ of the negative binomial distribution with known exponentk is presented. For any fixedμ 0(μ 1<μ 0<μ 2), the 2-SPRT provides an asymptotic solution to the modified Kiefer-Weiss problem. Determination ofμ 0 such that the test provides an approximate solution to the Kiefer-Weiss problem is described. The behavior of the 2-SPRT and the Sequential Probability Ratio Test is investigated using Monte Carlo methods. The error probabilities and the average sample numbers are compared. All the computations were carried out on the Alabama Supercomputer.  相似文献   
88.
A two-dimensional cross-section finite difference model is presented to simulate density dependent leachate migration in leaky aquifers. Unlike existing models, a new approach is adopted to couple the groundwater-flow equation and the hydrodynamic dispersion equation with the elimination of the intermediate step of calculating velocities. The concept of the reference density is employed, permitting increased accuracy (over pressure-based models) in the representation of the transport process. The model is then used to study the effect of several hydraulic and transport parameters on the flow pattern and plume migration which are found to be very sensitive to most of these parameters. Equiconcentration and equipotential lines are overlapped to provide a better understanding of the coupling effect.  相似文献   
89.
Dr. M. Riedel 《Metrika》1992,39(1):209-217
Summary In this note we characterize all linear transformations of random vectors which are invariant for a given parametric covariance family. Two one-dimensional covariance families are discussed in detail.  相似文献   
90.
An automatic self‐correction scheme is presented for online adjustment of stream‐flow forecasts during simulation of river systems with regulating structures, when actual flow data for interior points are available in real time. Another scheme is presented which allows for the modelling of channel losses due to physical effects such as evapotranspiration, bank storage and diversions. A previously developed river simulation/reservoir management model has been modified to include both schemes. The model is particularly useful for real‐time, short‐term flood forecasting and reservoir operation. The model application is made to the Lower Colorado River in Texas.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号