全文获取类型
收费全文 | 1128篇 |
免费 | 5篇 |
国内免费 | 7篇 |
专业分类
系统科学 | 16篇 |
丛书文集 | 1篇 |
教育与普及 | 6篇 |
理论与方法论 | 16篇 |
现状及发展 | 118篇 |
研究方法 | 201篇 |
综合类 | 657篇 |
自然研究 | 125篇 |
出版年
2018年 | 2篇 |
2017年 | 5篇 |
2016年 | 10篇 |
2015年 | 7篇 |
2014年 | 15篇 |
2013年 | 15篇 |
2012年 | 93篇 |
2011年 | 236篇 |
2010年 | 39篇 |
2009年 | 5篇 |
2008年 | 92篇 |
2007年 | 98篇 |
2006年 | 96篇 |
2005年 | 85篇 |
2004年 | 92篇 |
2003年 | 75篇 |
2002年 | 78篇 |
2001年 | 5篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1978年 | 5篇 |
1976年 | 3篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 5篇 |
1971年 | 4篇 |
1970年 | 4篇 |
1969年 | 5篇 |
1968年 | 2篇 |
1967年 | 2篇 |
1966年 | 1篇 |
1965年 | 1篇 |
1964年 | 1篇 |
1958年 | 1篇 |
1948年 | 1篇 |
1946年 | 2篇 |
排序方式: 共有1140条查询结果,搜索用时 31 毫秒
1.
2.
The universal acceptance of atomism in physics and chemistry in the early 20th century went along with an altered view on the epistemic status of microphysical conjectures. Contrary to the prevalent understanding during the 19th century, on the new view unobservable objects could be ‘discovered’. It is argued in the present paper that this shift can be connected to the implicit integration of elements of meta-empirical theory assessment into the concept of theory confirmation. 相似文献
3.
This paper examines the forecast accuracy of an unrestricted vector autoregressive (VAR) model for GDP, relative to a comparable vector error correction model (VECM) that recognizes that the data are characterized by co‐integration. In addition, an alternative forecast method, intercept correction, is considered for further comparison. Recursive out‐of‐sample forecasts are generated for both models and forecast techniques. The generated forecasts for each model are objectively evaluated by a selection of evaluation measures and equal accuracy tests. The result shows that the VECM consistently outperforms the VAR models. Further, intercept correction enhances the forecast accuracy when applied to the VECM, whereas there is no such indication when applied to the VAR model. For certain forecast horizons there is a significant difference in forecast ability between the intercept corrected VECM compared to the VAR model. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
4.
5.
6.
This paper, which presents an annotated checklist of the ‘lower Nymphalidae’ (Libytheinae, Danainae, Satyrinae, Charaxinae), is the fourth in a series on the butterfly fauna of Mount Kilimanjaro. Four genera of lower Nymphalidae (Danaus, Amauris, Bicyclus, Charaxes), with a total of 11 included species, are known or believed to occur within the main forest zone, from c. 1800 to 2800 m. Of these, only three species of Charaxes (Charaxes berkeleyi, Charaxes ansorgei, Charaxes xiphares) may be restricted locally to this primary forest. The lower slopes fauna, below 1800 m, is considerably richer, with a total of 11 genera and 41 species listed (8 species of which extend into the forest zone). Possible additional species, dubious earlier records, problems with African subspecies of Danaus chrysippus, a need for more work on certain Satyrinae, and classification of the genus Charaxes are discussed. An identification key to the subfamilies of Nymphalidae, and the 19 genera of Libytheinae, Danainae, Satyrinae, Charaxinae that occur in Tanzania, together with a key to the adults of all the species of these four subfamilies considered to occur or have occurred on Kilimanjaro, with 206 colour images, are included as online Supplementary Information. 相似文献
7.
正Published online:14 March 2014óScience China Press and Springer-Verlag Berlin Heidelberg 2014Erratum to:Chin.Sci.Bull.(2014)59(5–6):528–532DOI 10.1007/s11434-013-0060-1In the original publication of this paper,the first name and the last name of the first author has been documented 相似文献
8.
Treed Avalanche Forecasting: Mitigating Avalanche Danger Utilizing Bayesian Additive Regression Trees 下载免费PDF全文
Little Cottonwood Canyon Highway is a dead‐end, two‐lane road leading to Utah's Alta and Snowbird ski resorts. It is the only road access to these resorts and is heavily traveled during the ski season. Professional avalanche forecasters monitor this road throughout the ski season in order to make road closure decisions in the face of avalanche danger. Forecasters at the Utah Department of Transportation (UDOT) avalanche guard station at Alta have maintained an extensive daily winter database on explanatory variables relating to avalanche prediction. Whether or not an avalanche crosses the road is modeled in this paper via Bayesian additive tree methods. Utilizing daily winter data from 1995 to 2011, results show that using Bayesian tree analysis outperforms traditional statistical methods in terms of realized misclassification costs that take into consideration asymmetric losses arising from two types of error. Closing the road when an avalanche does not occur is an error harmful to resort owners, and not closing the road when one does may result in injury or death. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
9.
Stephen Richard Alfred John Timothy Lambert Jr 《Systemic Practice and Action Research》2012,25(4):323-354
This is an exploratory case study of a management issue that confronts filmmakers: how do they select locations for their films? The outcome of those decisions can have vast and immediate effects upon the profitability of a film. This is a sometimes shadowy, but significant industry with a major economic impact. For systems theory advocates, students, and explorers, this study demonstrates that investigative, immersive action research techniques can be used to explore what are otherwise hidden, somewhat cloistered business organizations and industry structures that are ordinarily closed to outsiders. The soft-system of this industry that is rooted upon trust, loyalty, alliances, relationships, and other non-financial bonds influence its decisions, and its institutional performance. While this research is focused upon a fragment of the overall film industry worldwide, and is thus limited in the universality of the propositions that subsequently emerge, this study can serve as a springboard for research into other soft systems, from which new knowledge of managerial perspectives can emerge. 相似文献
10.
Richard B. Watson 《Systemic Practice and Action Research》2012,25(5):441-456
Soft systems methodology (SSM) is now 40?years old. Another decade has passed since Checkland??s thirty year retrospective on the methodology, published in 2000. It can now be described as an old methodology. But it has adapted and changed over the years and is still very much alive, although the days are long gone when it was mainly developed and practised by its founders at the University of Lancaster. Interestingly, considering that many applications of SSM over the years have been to information systems, it was developed before the age of personal computers and the Internet. The way SSM is viewed has changed over the years as it has been applied to various types of problem situation. Every use of SSM will potentially hold methodological lessons in addition to those about the situation of concern; these may include SSMs framework of ideas, processes and way of use. How is SSM going to change in the future? This will depend in part on the types of problem situation to which it is applied. This paper examines some problem situations associated with emerging technologies in the information age to which SSM has not yet been much applied. These include computer simulation and virtual reality, ubiquitous computing and the design of cities, Information Technology Service Management and the design of enterprise information architectures. Some of the different worldviews associated with these problem situations which could be explored using SSM are noted. 相似文献