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   2447篇
  免费   271篇
  国内免费   31篇
化学   267篇
力学   52篇
综合类   100篇
数学   1957篇
物理学   373篇
  2024年   2篇
  2023年   13篇
  2022年   68篇
  2021年   62篇
  2020年   48篇
  2019年   60篇
  2018年   48篇
  2017年   86篇
  2016年   99篇
  2015年   106篇
  2014年   203篇
  2013年   200篇
  2012年   141篇
  2011年   170篇
  2010年   165篇
  2009年   187篇
  2008年   182篇
  2007年   215篇
  2006年   120篇
  2005年   89篇
  2004年   92篇
  2003年   59篇
  2002年   43篇
  2001年   43篇
  2000年   42篇
  1999年   25篇
  1998年   21篇
  1997年   20篇
  1996年   17篇
  1995年   9篇
  1994年   19篇
  1993年   10篇
  1992年   16篇
  1991年   8篇
  1990年   8篇
  1989年   2篇
  1988年   17篇
  1987年   3篇
  1986年   5篇
  1985年   7篇
  1984年   2篇
  1983年   3篇
  1982年   5篇
  1981年   5篇
  1980年   1篇
  1979年   2篇
  1977年   1篇
排序方式: 共有2749条查询结果,搜索用时 15 毫秒
71.
6S现场管理的方法已经在多个领域得以运用并取得较好的效果。结合计量检测实验室的特点,从整理、整顿、清扫、清洁、素养、安全6各方面讨论了6S现场管理在计量检测实验室中的应用。该管理模式可以提高工作效率,降低物品遗失率,减少寻找物品的时间等,提高计量检测质量。  相似文献   
72.
研究生助教是对研究生自身能力的培养和锻炼,同时也补充了本科教学教师资源。提高本科教学的质量,需要加强对研究生助教的培训、指导、管理和考评,也需要加强课程教学的统一规范管理,加强对学生学习的督促和引导。本文探讨了基础化学实验研究生助教的教学经验,并对今后实验教学管理以及研究生助教的培养等提出一些思考和建议。  相似文献   
73.
张卫华 《力学学报》2021,53(1):96-104
高速铁路的出现,使得轮轨交通技术达到更高的层次.速度提升不仅对列车的牵引动力与动力学性能提出更高要求.而且,列车与线路、气流等运行环境的耦合作用加剧,并直接影响到了列车的运行品质和安全性.在高速列车发展初期,研究关注的是如何保证高速列车能高速、平稳和安全运行.随着运行速度的提高,系统间耦合加强,服役模拟也越来越受到重视...  相似文献   
74.
本文研究了在需求随价格变化及物品易变质的条件下,当供应商给予数量折扣时的库存问题。证明了当供应商给予数量折扣时,零售商的需求量是增大的,并给出了供应商给予数量折扣时零售商的订货量和订货周期的计算方法。对物品变质率和需求价格敏感系数对零售商的订货量、订货周期、出售价格和单位时间利润的影响进行了数值分析,并给出了数值算例。  相似文献   
75.
In participating life insurance, management decisions regarding the asset composition can substantially impact the value of a policy from the policyholders’ perspective as well as the insurer’s risk situation. Due to the long-term guarantees often embedded in these contracts, life insurers typically invest a considerable portion of their capital in long-term assets such as corporate and government bonds. Besides interest rate risk, the value of these bond investments is thus particularly influenced by credit risk. Thus, the aim of this paper is to examine the impact of market risk associated with the asset composition on fair valuation and risk assessment with focus on credit risk and its interaction with equity risk and interest rate risk. Our analysis emphasizes that the consideration of credit risk associated with bonds has a strong impact on the fair valuation and risk measurement in the context of participating life insurance contracts, even in case of higher grade bond exposures.  相似文献   
76.
The aim of this paper is to analyse the operational response of a Synchronised Supply Chain (SSC). To do so, first a new mathematical model of a SSC is presented. An exhaustive Latin Square design of experiments is adopted in order to perform a boundary variation analysis of the main three parameters of the periodic review smoothing (SR) order-up-to policy: i.e., lead time, demand smoothing forecasting factor, and proportional controller of the replenishment rule. The model is then evaluated under a variety of performance measures based on internal process benefits and customer benefits. The main results of the analysis are: (I) SSC responds to violent changes in demand by resolving bullwhip effect and by creating stability in inventories under different parameter settings and (II) in a SSC, long production–distribution lead times could significantly affect customer service level. Both results have important consequences for the design and operation of supply chains.  相似文献   
77.
We analyze the optimal investment strategy of a firm that can complete a project either in one stage at a single freely chosen time point or in incremental steps at distinct time points. The presence of economies of scale gives rise to the following trade-off: lumpy investment has a lower total cost, but stepwise investment gives more flexibility by letting the firm choose the timing individually for each stage. Our main question is how uncertainty in market development affects this trade-off. The answer is unambiguous and in contrast with a conventional real-options intuition: higher uncertainty makes the single-stage investment more attractive relative to the more flexible stepwise investment strategy.  相似文献   
78.
为了更好地解决决策者具有(严格)凸性偏好结构下的多目标决策问题,一般目标空间为有界凸域的情形常常可以转化为目标空间为有界闭凸区域的情形,首先分析了切割平面及该平面上偏好最优点与被切割平面分割成的为有界闭凸区域的目标空间或目标空间的子集的两个部分之间的关系;然后分析并指出了对于包含全局偏好最优目标方案点的为有界闭凸域的目标空间及其子集(准最优目标集),在确定了切割平面上的偏好最优点后,通过适当地选取供决策者与切割平面的偏好最优点进行比较判断的目标方案点,经过一次比较就可以确定一个新的范围更小的包含全局偏好最优目标方案点的目标空间的有界闭凸子区域(准最优目标集).为获取切割平面上的偏好最优点,提出了改进的坐标轮换法.在这些结论和方法的基础上,提出了决策者具有(严格)凸性偏好结构下的一类交互式多目标决策方法,要求决策者提供较易的偏好性息,决策效能较好.  相似文献   
79.
We investigate scaling and memory effects in return intervals between price volatilities above a certain threshold q for the Japanese stock market using daily and intraday data sets. We find that the distribution of return intervals can be approximated by a scaling function that depends only on the ratio between the return interval τ and its mean 〈τ〉. We also find memory effects such that a large (or small) return interval follows a large (or small) interval by investigating the conditional distribution and mean return interval. The results are similar to previous studies of other markets and indicate that similar statistical features appear in different financial markets. We also compare our results between the period before and after the big crash at the end of 1989. We find that scaling and memory effects of the return intervals show similar features although the statistical properties of the returns are different.  相似文献   
80.
 Maintaining a high quality of research and development (R&D) is fundamental for the competitiveness of European industry. The development of new technologies and the improvement of existing technologies, products, production processes, measurement instrumentation and methods as well as basic research is essential. The objective of the workshop on "Quality Management in Analytical Chemical Research and Development" was to bring together experts from the academic world, industrial and institutional laboratories and also accreditation bodies to discuss the actual state of the art in the field of quality management in R&D, and to set up milestones for further activities. Furthermore, an important objective was to present the EURACHEM/CITAC Guide 2. The paper outlines the programme of the workshop and summarises the round-table discussions and expert recommendations. Most of the contributions to the round-table discussions will be published as full papers in a forthcoming issue of Accreditation and Quality Assurance. The workshop was organised by the Institut für Chemo- und Biosensorik (ICB), Münster, with the financial support of the SMT-Programme of the European Commission (Contract No.: SMT4-CT98-6534).  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