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   2092篇
  免费   68篇
  国内免费   32篇
管理学   342篇
民族学   11篇
人才学   1篇
人口学   13篇
丛书文集   155篇
理论方法论   62篇
综合类   1358篇
社会学   84篇
统计学   166篇
  2024年   7篇
  2023年   24篇
  2022年   26篇
  2021年   50篇
  2020年   40篇
  2019年   32篇
  2018年   39篇
  2017年   50篇
  2016年   46篇
  2015年   71篇
  2014年   114篇
  2013年   147篇
  2012年   120篇
  2011年   150篇
  2010年   144篇
  2009年   119篇
  2008年   130篇
  2007年   118篇
  2006年   135篇
  2005年   132篇
  2004年   90篇
  2003年   86篇
  2002年   66篇
  2001年   73篇
  2000年   54篇
  1999年   23篇
  1998年   18篇
  1997年   20篇
  1996年   9篇
  1995年   13篇
  1994年   8篇
  1993年   3篇
  1992年   7篇
  1991年   9篇
  1990年   3篇
  1989年   3篇
  1988年   4篇
  1987年   4篇
  1986年   1篇
  1984年   1篇
  1983年   2篇
  1975年   1篇
排序方式: 共有2192条查询结果,搜索用时 0 毫秒
991.
In this article, we present a novel approach to clustering finite or infinite dimensional objects observed with different uncertainty levels. The novelty lies in using confidence sets rather than point estimates to obtain cluster membership and the number of clusters based on the distance between the confidence set estimates. The minimal and maximal distances between the confidence set estimates provide confidence intervals for the true distances between objects. The upper bounds of these confidence intervals can be used to minimize the within clustering variability and the lower bounds can be used to maximize the between clustering variability. We assign objects to the same cluster based on a min–max criterion and we separate clusters based on a max–min criterion. We illustrate our technique by clustering a large number of curves and evaluate our clustering procedure with a synthetic example and with a specific application.  相似文献   
992.
以可变模糊集理论为基础,提出一种新的区域城市化水平评价方法-可变模糊识别评价方法,详细论述了其建模过程。该方法能够科学、合理确定样本指标对各级指标标准区间的相对隶属度、相对隶属函数。并且能够通过变换模型及其参数,合理的给出样本的评价等级,评价结果的可信度较高。最后将该方法应用于江苏省城市化水平评价。结果表明,该方法计算简便,计算结果可靠,可以推广到我国其他地区的城市化水平评价和实现同一区域城市化进程的动态评价。  相似文献   
993.
In the literature a systematic method of obtaining a group testing design is not available at present. Weideman and Raghavarao (1987a, b) gave methods for the construction of non - adaptive hypergeometric group testing designs for identifying at most two defectives by using a dual method. In the present investigation we have developed a method of construction of group testing designs from (i) Hypercubic Designs for t ≡ 3 (mod 6) and (ii) Balanced Incomplete Block Designs for t ≡ 1 (mod 6) and t ≡ 3 (mod 6). These constructions are accomplished by the use of dual designs. The designs so constructed satisfy specified properties and attained an optimal bound as discussed by Weidman and Raghavarao (1987a,b). Here it is also shown that the condition for pairwise disjoint sets of BIBD for t ≡ 1 (mod 6) given by Weideman and Raghavarao (1987b) is not true for all such designs.  相似文献   
994.
A random vector X = (X 1,…,X n ) is negatively associated if and only if for every pair of partitions X 1 = (X π(1),…,X π(k)), X 2 = (X π(k+1),…,X π(n)) of X , P( X 1 ? A, X 2 ? B) ≤ P( X 1 ? A)P( X 2 ? B) whenever A and B are open upper sets and π is any permutation of {1,…,n}. In this paper, we develop some of concepts of negative dependence, which are weaker than negative association but stronger than negative orthant dependence by requiring the above inequality to hold only for some upper sets A and B and applying the arguments in Shaked.  相似文献   
995.
996.
In most of flexible production schemes, the flexible manufacturing cells (FMCs) are more economical and feasible. So, an important task is to establish the correct reliability analysis model for the FMCs. However, with the increasing of system complexity, some reliability analysis modes can hardly describe the actual situation. Besides, due to the lack of test-data and field-data during the design stage of FMC' system, the reliability modeling will be more complicated. In order to deal with the deficient data and the uncertainty occurred from analysis and judgment, this article analyzes the reliability of FMCs system through the method of fuzzy fault tree, which is based on triangular fuzzy membership. At last, a practical example is illustrated. The reliability analysis model indicates that it can offer a diagnostic tool for FMCs system and improve the efficiency of operation and production in FMCs system.  相似文献   
997.
Over a few decades, regression model has received considerable attention and has been shown to be successful when applied together with other models. One of the most successful models is the sample selection model or the selectivity model. However, uncertainties and ambiguities do exist in the models, particularly the relationship between the endogenous and exogenous variables. Therefore, it will disrupt the ability and effectiveness of the model proceeded to give the estimated value that can explain the actual situation of a phenomenon. These are the questions and problems that are yet to be explored and the main aim of this study. A new framework for estimation of the sample selection model using the concept of fuzzy modelling is introduced. In this approach, a flexible fuzzy concept hybrid with the parametric sample selection model is known as fuzzy parametric sample selection model (FPSSM). The elements of vagueness and uncertainty in the models are represented in the model construction, as a way of increasing the available information to produce a more accurate model. This led to the development of the convergence theorem presented in the form of triangular fuzzy numbers to be used in the model. Consistency is an indicator of effectiveness of the developed models and justified using Monte Carlo simulation. Consistency and efficiency of the proposed model are considered in this study. In order to achieve that condition, a Monte Carlo simulation is used. Hence, the error terms of FPSSM are assumed to follow the normal and the chi-square distributions. Simulation results show that FPSSM is consistent and efficient when its distributions are normal. Instead, the FPSSM by chi-square distribution is found to be inconsistent.  相似文献   
998.
为了克服测井解释中通常采用的最大隶属原则进行决策分析导致信息丢失所引起的判别结果的偏差,将模糊数学中的非对称贴近度分析法与神经网络结合起来,充分利用各分量信息建立了一种基于模糊贴近度的神经网络识别法。通过临盘油田实际资料解释表明,在储层识别中采用该方法可大大改善解释效果。  相似文献   
999.
位于阿根廷中西部地区的库约盆地和内乌肯盆地是南美次安第斯盆地群南段的两个较独特的弧后前陆盆地。俯冲角度的变化导致二者岩石圈及冲断带构造的不同。两个盆地经历了相似的4 个盆地演化阶段:基底、裂谷期、后裂谷沉降期、前陆期。库约盆地发育一个已证实的含油气系统,以上三叠统富有机质湖相泥岩为主力烃源岩,主要以三叠系河流相砂砾岩为储层,盖层为三叠系层内盖层和白垩系区域盖层,圈闭形成和油气生成高峰在新近纪。内乌肯盆地发育1 个已证实的和3 个推测的含油气系统,除裂谷期上三叠统源岩外,其余下—中侏罗统、凡兰吟阶—巴列姆阶、提塘阶—凡兰吟阶的源岩均发育在裂谷后沉降单元内,储层范围从二叠系至新生界,最富产层为上侏罗统—下白垩统砂岩和灰岩储层,油气系统关键时刻为晚白垩世—新近纪。海陆相沉积环境的不同造成烃源岩质量的巨大差异,直接体现在其成藏组合中赋存悬殊的油气资源量;各阶段中相对独立的构造–沉积环境造成了油气地质特征与勘探潜力的差异。  相似文献   
1000.
本文重点研究从IPv4向IPv6过渡的策略,分析了当前三种比较成熟的技术:双协议栈技术、隧道技术和网络地址协议转换技术,并提出GRE隧道的原理模型,研究如何实现部门内部与校园主机服务器的隧道连接,进而完成IPv4向IPv6的过渡.  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