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   7753篇
  免费   688篇
  国内免费   107篇
系统科学   1153篇
丛书文集   94篇
教育与普及   73篇
理论与方法论   292篇
现状及发展   877篇
研究方法   7篇
综合类   6051篇
自然研究   1篇
  2024年   14篇
  2023年   24篇
  2022年   30篇
  2021年   43篇
  2020年   23篇
  2019年   14篇
  2018年   745篇
  2017年   756篇
  2016年   458篇
  2015年   87篇
  2014年   65篇
  2013年   69篇
  2012年   329篇
  2011年   1030篇
  2010年   892篇
  2009年   544篇
  2008年   608篇
  2007年   887篇
  2006年   100篇
  2005年   143篇
  2004年   206篇
  2003年   220篇
  2002年   125篇
  2001年   76篇
  2000年   85篇
  1999年   122篇
  1998年   94篇
  1997年   112篇
  1996年   101篇
  1995年   87篇
  1994年   100篇
  1993年   77篇
  1992年   58篇
  1991年   61篇
  1990年   56篇
  1989年   36篇
  1988年   34篇
  1987年   22篇
  1986年   7篇
  1985年   4篇
  1984年   1篇
  1978年   2篇
  1967年   1篇
排序方式: 共有8548条查询结果,搜索用时 15 毫秒
981.
运用文献资料法与资料分析法对哈尼族磨秋传统体育项目进行全面、系统、科学的介绍,并根据不同的风俗习惯、地域特征、社会生活形态等呈现出磨秋多姿多彩的局面.从发展的角度全面考察了哈尼族磨秋的历史变迁,并提出了传承保护哈尼族磨秋的一些措施:扩大宣传、通过学校体育教育推广磨秋传统体育,重视哈尼族磨秋运动的基础理论研究,建立哈尼族传统体育文化研究基地.  相似文献   
982.
983.
A dragonfly wing consists of membranes and both longitudinal and cross veins. We observed the microstructure cross-section at several locations in the dragonfly wing using environmental scanning electron microscopy (ESEM). The organic nature of the junction between the vein and the membrane was clearly identifiable. The membrane was divided into two layers, the upper epidermis and the lower epidermis. These layers extend around the sandwich structure vein, and combine with the adjacent membrane at a symmetrical location along the vein. Thus, we defined this as an organic junction between the vein and the membranes. The organic junction is able to form a tight corrugation angle, which dramatically increases both the warping rigidity and the strength of the wing, but not the torsional rigidity. The torsional deformation is primarily controlled by the microstructure of the longitudinal veins, and is based on the relative rotation angle between the epidermal layer and the inner layer of the vein that forms the zigzag section.  相似文献   
984.
We give a “direction for use” of the scale relativity theory and apply it to an example of spontaneous multiscale integration including four embedded levels of organization (intracellular, cell, tissue and organism-like levels). We conclude by an update of our analysis of the arctic sea ice melting.  相似文献   
985.
Modeling a business to match its customer perceived (and customer desired) outcomes, remains an on-going task. This paper considers shows how a service value networks (SVNs) approach may be engaged to model, and deliver, understanding of the front-end business and its direct engagement with its immediate (or front-end) customers. These front-end customers may be either: (1) its off-line, in-store customers - engaging directly with the business sales staff (or representative), or-(2) its on-line, virtual customers - engaging with the business via internet or remote access. In this situation, both the business, and the customer draw upon their respective viewpoints, and both sides influence the interaction. External to these business and customer influences are additional factors that capture the immediate and broader global effects - termed environmental effects. These three business-customer engagement areas of influence are captured by a SVN SEM approach.
Without a business-customer encounter of some kind the likelihood of a services business, and a prospecting customer, successfully engaging in an exchange process is reduced. This exchange may be a physical, and/or services exchange, and/or an information and/or ideas exchange. To the business, this encounter is, in effect, a trade, and as a result, the business targets acquiring an economic exchange that will ultimately deliver a net positive economic outcome. To the customer, external and internal information feeds, servicing, perceived value, and satisfaction, are key encounter drivers. SVNs offers a new way to understand the business-customer encounter, and to then utilize this acquired knowledge to either: (1) build a strategic management model, or (2) reengineer its business networks, and to then create a re-positioned, more customer-aligned business operation - one that is capable of delivering win - win, competitive business-customer solutions.  相似文献   
986.
本文在分析市区水资源的基础上,着探讨了水资源开发利用存在的问题及解决途径。  相似文献   
987.
本文介绍了傢具CAD真实感图形处理中的一些方法。由于采用了改进的消隐算法、合理的光照模型和纹理模型、产生的图形真实感强,图形生成效率高,对提高傢具CAD系统的整体效益具有重要作用。  相似文献   
988.
1. Introduction The Capacitated Arc Routing Problem(CARP) is defined on an undirected network inwhich a fleet of identical vehicles with limitedcapacity is based at a depot node. Each edge hasa non-negative traversal cost and can betraversed any number…  相似文献   
989.
Einstein’s early calculations of gravitational lensing, contained in a scratch notebook and dated to the spring of 1912, are reexamined. A hitherto unknown letter by Einstein suggests that he entertained the idea of explaining the phenomenon of new stars by gravitational lensing in the fall of 1915 much more seriously than was previously assumed. A reexamination of the relevant calculations by Einstein shows that, indeed, at least some of them most likely date from early October 1915. But in support of earlier historical interpretation of Einstein’s notes, it is argued that the appearance of Nova Geminorum 1912 (DN Gem) in March 1912 may, in fact, provide a relevant context and motivation for Einstein’s lensing calculations on the occasion of his first meeting with Erwin Freundlich during a visit in Berlin in April 1912. We also comment on the significance of Einstein’s consideration of gravitational lensing in the fall of 1915 for the reconstruction of Einstein’s final steps in his path towards general relativity.  相似文献   
990.
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