全文获取类型
收费全文 | 895篇 |
免费 | 85篇 |
国内免费 | 17篇 |
专业分类
化学 | 90篇 |
力学 | 11篇 |
综合类 | 25篇 |
数学 | 696篇 |
物理学 | 175篇 |
出版年
2023年 | 3篇 |
2022年 | 16篇 |
2021年 | 43篇 |
2020年 | 16篇 |
2019年 | 24篇 |
2018年 | 24篇 |
2017年 | 26篇 |
2016年 | 29篇 |
2015年 | 26篇 |
2014年 | 39篇 |
2013年 | 101篇 |
2012年 | 67篇 |
2011年 | 49篇 |
2010年 | 61篇 |
2009年 | 59篇 |
2008年 | 61篇 |
2007年 | 81篇 |
2006年 | 31篇 |
2005年 | 49篇 |
2004年 | 37篇 |
2003年 | 25篇 |
2002年 | 18篇 |
2001年 | 13篇 |
2000年 | 17篇 |
1999年 | 15篇 |
1998年 | 9篇 |
1997年 | 8篇 |
1996年 | 9篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1987年 | 1篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有997条查询结果,搜索用时 37 毫秒
851.
本文在[1]的基础上,进一步讨论在有消费的情况下如何根据市场需求来安排生产,并使之有最快的年增长率。 相似文献
852.
853.
本文在(1),(2)的基础上,进一步研究在消费系数逐年有变的情况下,如何根据市场需求来安排生产,并使之有最佳的年增长速率,本文最后还讨论了当消费系数为随机变量时,如何确定投入产综和产出产综的概率分布。 相似文献
854.
Michael J. North Charles M. Macal James St. Aubin Prakash Thimmapuram Mark Bragen June Hahn James Karr Nancy Brigham Mark E. Lacy Delaine Hampton 《Complexity》2010,15(5):37-47
Consumer markets have been studied in great depth, and many techniques have been used to represent them. These have included regression‐based models, logit models, and theoretical market‐level models, such as the NBD‐Dirichlet approach. Although many important contributions and insights have resulted from studies that relied on these models, there is still a need for a model that could more holistically represent the interdependencies of the decisions made by consumers, retailers, and manufacturers. When the need is for a model that could be used repeatedly over time to support decisions in an industrial setting, it is particularly critical. Although some existing methods can, in principle, represent such complex interdependencies, their capabilities might be outstripped if they had to be used for industrial applications, because of the details this type of modeling requires. However, a complementary method—agent‐based modeling—shows promise for addressing these issues. Agent‐based models use business‐driven rules for individuals (e.g., individual consumer rules for buying items, individual retailer rules for stocking items, or individual firm rules for advertizing items) to determine holistic, system‐level outcomes (e.g., to determine if brand X's market share is increasing). We applied agent‐based modeling to develop a multi‐scale consumer market model. We then conducted calibration, verification, and validation tests of this model. The model was successfully applied by Procter & Gamble to several challenging business problems. In these situations, it directly influenced managerial decision making and produced substantial cost savings. © 2010 Wiley Periodicals, Inc. Complexity, 2010 相似文献
855.
The interactions between investors and investments are of significant importance to understand the dynamics of financial markets. An evolutionary model is proposed to investigate the dynamic behaviors of investors and investments in a market ecology. The investors are divided into two groups, active ones and passive ones, distinguished by different selection capabilities based on the partial information, while the investments are simply categorized as good ones and bad ones. Without external influence, the system consisting of both investors and investments can self-organize to a quasi-stationary state according to their own strategies associating with the gains of market information. The model suggests that the partial information asymmetry of investors and various qualities of investments commonly give rise to a diverse dynamic behavior of the system by quantifying the fraction of active investors and of good investment at the quasi-stationary state. 相似文献
856.
G. Margaritondo 《Progress in Surface Science》1997,56(4):311-346
For decades, techniques based on synchrotron light sources have played a central role in solid interface research. This role has been recently enhanced by two factors: the commissioning of the third generation of sources, characterized by unprecedented levels of brightness, and the first utilization cases of another class of photon sources related to synchrotron facilities, the free electron lasers (FEL's). This review will first present some relevant examples of how the new facilities are changing the scene of interface research, most notably in the domain of spectromicroscopy. We will specifically illustrate how the crucial problem of the lateral fluctuations of interface properties is being attacked with both synchrotron-light and FEL techniques. Then, we will argue that the present applications are only marginally exploiting the amazing capabilities of the new sources. The main case to illustrate this point is coherence-sharpened x-ray imaging, a very promising and spectacular technique developed for medical radiology, which could find extremely interesting applications in interface research. 相似文献
857.
R. Rial-Otero 《Talanta》2007,71(2):503-514
Nowadays the control of pesticides in honey is an issue of primary health importance as consequence of the increasing content of these chemicals in the aforementioned matrix. This poisoning has led to the worldwide increasing loss of bees since 1995. From Europe to Canada, scientist, beekeepers and chemical companies disagree about the reasons that have led to colony losses higher than 50% in some areas. This problem has become a public health issue due to the high honey worldwide consumption. The presence of pesticides in honey has been directly related to bees’ mortality by some researchers through pesticide presence in (1) pollen, (2) honeycomb walls, (3) own bees and (4) honey. In this work we describe the actual state-of-the-art for pesticides determination in honey along with a review in this subject focused on sample treatments and instrumentation. Finally, future trends are also commented. 相似文献
858.
The accreditation of laboratories has emphasized the use of interlaboratory comparisons as a tool to monitor the comparability
and accuracy of results laboratories produce. An interlaboratory comparison for water laboratories was organized among European
Cooperation for Accreditation (EA) member countries; 30 laboratories, 7 of which were not accredited, from 14 European countries
participated in this intercomparison. All the laboratories were chosen by the appropriate national accreditation bodies, with
the instruction to select as participants those laboratories which act as national reference laboratories in this field. About
90% of the data collected was considered satisfactory after statistical treatment. Non-accredited laboratories performed as
well as accredited laboratories. The laboratories were asked to take corrective action and report the corrections to the accreditation
bodies. A great variation in the reported uncertainties of the results was observed. There seems to be a need to organize
EA interlaboratory comparisons for national reference laboratories analysing water. It is obvious that even reference laboratories need training in how to estimate the uncertainty of results.
Received: 22 July 1998 · Accepted: 21 September 1998 相似文献
859.
Biosensors for environmental monitoring A global perspective 总被引:2,自引:0,他引:2
The intention of this article is to reflect the advances and describe the trends on biosensors for environmental applications. Biosensors are useful analytical tools for environmental monitoring, capable of providing results in real time, simple to use, portable and cost-effective. Some examples of biosensors in advanced stage of development, which have been applied to real samples, as well as of commercial devices, are given. Biosensors designed for measurement of either specific chemicals or their biological effects, such as toxicity biosensors and endocrine effect biosensors, are discussed. This overview also addresses the support provided by public institutions for biosensor research in the USA, Japan and, especially, in Europe. Future prospects of biosensor technology, with special emphasis in the development of new sensing elements, are foreseen. 相似文献
860.
Luiz Flávio Autran Monteiro Gomes Luı´s Alberto Duncan Rangel 《European Journal of Operational Research》2009
This article presents an evaluation study of residential properties carried out together with real estate agents in the city of Volta Redonda, Brazil. The study aimed to define a reference value for the rents of these properties using the TODIM method of Multicriteria Decision Aiding. By applying this method to the ordering of properties with different characteristics, a ranking of all the properties was obtained and, as a result of this, diverse ranges of rental values for the properties under analysis. The study was complemented by an analysis of the sensitivity of the numerical results obtained. 相似文献