全文获取类型
收费全文 | 39072篇 |
免费 | 65篇 |
国内免费 | 106篇 |
专业分类
系统科学 | 191篇 |
丛书文集 | 779篇 |
教育与普及 | 99篇 |
理论与方法论 | 234篇 |
现状及发展 | 17232篇 |
研究方法 | 1550篇 |
综合类 | 18645篇 |
自然研究 | 513篇 |
出版年
2013年 | 247篇 |
2012年 | 527篇 |
2011年 | 1071篇 |
2010年 | 237篇 |
2008年 | 660篇 |
2007年 | 681篇 |
2006年 | 714篇 |
2005年 | 727篇 |
2004年 | 641篇 |
2003年 | 697篇 |
2002年 | 671篇 |
2001年 | 1156篇 |
2000年 | 1061篇 |
1999年 | 733篇 |
1992年 | 700篇 |
1991年 | 559篇 |
1990年 | 606篇 |
1989年 | 596篇 |
1988年 | 600篇 |
1987年 | 616篇 |
1986年 | 584篇 |
1985年 | 738篇 |
1984年 | 584篇 |
1983年 | 495篇 |
1982年 | 448篇 |
1981年 | 434篇 |
1980年 | 574篇 |
1979年 | 1214篇 |
1978年 | 1034篇 |
1977年 | 1021篇 |
1976年 | 757篇 |
1975年 | 825篇 |
1974年 | 1131篇 |
1973年 | 1012篇 |
1972年 | 1066篇 |
1971年 | 1259篇 |
1970年 | 1638篇 |
1969年 | 1260篇 |
1968年 | 1213篇 |
1967年 | 1242篇 |
1966年 | 1060篇 |
1965年 | 756篇 |
1964年 | 193篇 |
1959年 | 446篇 |
1958年 | 683篇 |
1957年 | 541篇 |
1956年 | 455篇 |
1955年 | 396篇 |
1954年 | 424篇 |
1948年 | 269篇 |
排序方式: 共有10000条查询结果,搜索用时 11 毫秒
281.
Douglas A. Wilson Victoria Raish Alison Carr-Chellman 《Systemic Practice and Action Research》2017,30(3):277-293
The paper explores cinematic films as a pedagogical tool to promote critical thinking and student discussions in a doctoral-level learning, design, and technology seminar course at a major U.S. research university. These discussions focused on systemic change and systemic thinking concepts. The authors offer evidence from the literature that supports films’ power as a visual metaphor and neurocognitive stimulator to promote development of new perspectives in graduate students on case studies through articulation, reflection, and explanation of their thought processes on change and diffusion of innovation. There are theoretical, political, social, and technological issues that create tensions during any systemic change effort. The goal of using film in this seminar is to equip students with the requisite skills, theoretical frameworks, and interpersonal experiences needed to address these issues within organizations and communities. The change expected from systemic thinking is for students to think more deeply about the interconnectedness of systems and the importance of bottom-up change efforts that consider the perspective of all stakeholders. 相似文献
282.
Learning organisation literature has widely discussed the connections between “double-loop” learning and its significance to organisational performance, but paying little attention to tools and systems that can operationalise “double-loop” learning in organisations. This paper investigates the impact of applying a systems approach for service operations design, expressed as the Vanguard Method (Seddon, Freedom from command and control: a better way to make the work work, 2003), in order to activate “double-loop” learning in service organisations. Two case studies were conducted in the banking mortgage operations and adults’ social care services in the UK, using the dimensions of the learning organisation questionnaire (DLOQ), semi-structured interviews, observations, and documents. The findings of the cross-case analysis support the link of applying the Vanguard Method with operationalising “double-loop” learning through three main factors, namely systematic-operations improvement, organisational capacity development, and outside-in mode of work; that are all embedded into the seven dimensions of the DLOQ. The value of this paper is the introduction of a service operations design tool that can activate “double-loop” learning performance in the fast changing knowledge era. It also provides an impetus for service organisations to creatively influence employees’ competencies to effectively improve internal systems. 相似文献
283.
Automatic patent document summarization for collaborative knowledge systems and services 总被引:1,自引:0,他引:1
Engineering and research teams often develop new products and technologies by referring to inventions described in patent
databases. Efficient patent analysis builds R&D knowledge, reduces new product development time, increases market success,
and reduces potential patent infringement. Thus, it is beneficial to automatically and systematically extract information
from patent documents in order to improve knowledge sharing and collaboration among R&D team members. In this research, patents
are summarized using a combined ontology based and TF-IDF concept clustering approach. The ontology captures the general knowledge
and core meaning of patents in a given domain. Then, the proposed methodology extracts, clusters, and integrates the content
of a patent to derive a summary and a cluster tree diagram of key terms. Patents from the International Patent Classification
(IPC) codes B25C, B25D, B25F (categories for power hand tools) and B24B, C09G and H011 (categories for chemical mechanical
polishing) are used as case studies to evaluate the compression ratio, retention ratio, and classification accuracy of the
summarization results. The evaluation uses statistics to represent the summary generation and its compression ratio, the ontology
based keyword extraction retention ratio, and the summary classification accuracy. The results show that the ontology based
approach yields about the same compression ratio as previous non-ontology based research but yields on average an 11% improvement
for the retention ratio and a 14% improvement for classification accuracy. 相似文献
284.
调节大豆籽粒生育的生理生态因素 总被引:1,自引:0,他引:1
大豆籽粒是生殖生长时期植株光合产物主要存储库,鼓粒灌浆期籽粒的生长发育以及干物质积累的过程直接影响大豆的产量。因此,研究大豆籽粒的生长发育及其影响因素对提高产量至关重要。影响大豆籽粒生长发育的因素很多,从源库的改变、外界温度、光照、水分供应以及二氧化碳的浓度的影响,酶活性、内源物质含量的调节以及植物激素的调控等方面予以综述。参64。 相似文献
285.
从人工生命到人工社会--复杂社会系统研究的现状和展望 总被引:28,自引:10,他引:28
介绍了人工社会研究工作的内容、方法及其思想基础,并对其应用和未来趋势进行展望。文中简述了社会学研究的历史阶段、主要问题和困难,人工生命和人工社会方法的有效性,并着重描述了Epstein和Axtell的工作,以及相应的涌现方法在复杂社会系统研究中的中心作用。本文还讨论了目前对人工社会方法的各种批判意见及其回应。 相似文献
286.
This article uses data from the 1971 and 2001 Censuses, the 1999-2003 Labour Force Survey and the 1977 to 2002 International Passenger Survey to investigate the migration processes contributing to the age structure and ageing of the UK's overseas-born population. Overall almost half of recent decades' immigrants to the UK emigrate again within five years of arrival, but with large variation by overseas country of birth. Between half and two thirds of the immigrants born in the continental European Union, North America and Oceania emigrate again within five years, while 15 per cent of those born in the Indian subcontinent do so. Significant cumulative emigration more than five years after arrival is seen among earlier immigrants from the Indian subcontinent, the Caribbean Commonwealth and Europe. Large country-of-origin variations in the ratio of pension-age population to working-age population primarily reflect the country composition of immigration streams 30 or more years before. 相似文献
287.
FROM MANUFACTURING SCHEDULING TO SUPPLY CHAIN COORDINATION:THE CONTROL OF COMPLEXITY AND UNCERTAINTY
Peter B.LUH 《系统科学与系统工程学报(英文版)》2003,12(3):279-297
With time-based competition and rapid technology advancements, effective manufacturingscheduling and supply chain coordination are critical to quickly respond to changing marketconditions. These problems, however, are difficult in view of inherent complexity and variousuncertainties involved. Based on a series of results by the authors, decomposition and coordination byusing Lagrangian relaxation is identified in this paper as an effective way to control complexity anduncertainty.A manufacturing scheduling problem is first formulated within the job shop context withuncertain order arrivals, processing times, due dates, and part priorities as a separable optimizationproblem. A solution methodology that combines Lagrangian relaxation, stochastic dynamicprogramming, and heuristics is developed. Method improvements to effectively solve large problemsare also highlighted. To extend manufacturing scheduling within a factory to coordinate autonomicmembers across chains of suppliers, a decentralized supply chai 相似文献
288.
This paper analyzes a discrete-time multiple vacations finite-buffer queueing system with batch renewal input in which inter-arrival time of batches are arbitrarily distributed.Service and vacation times are mutually independent and geometrically distributed.The server takes vacations when the system does not have any waiting jobs at a service completion epoch or a vacation completion epoch.The system is analyzed under the assumptions of late arrival system with delayed access and early arrival system.Using the supplementary variable and the imbedded Markov chain techniques, the authors obtain the queue-length distributions at pre-arrival,arbitrary and outside observer’s observation epochs for partial-batch rejection policy.The blocking probability of the first-,an arbitrary-and the last-job in a batch have been discussed.The analysis of actual waiting-time distributions measured in slots of the first-,an arbitrary- and the last-job in an accepted batch,and other performance measures along with some numerical results have also been investigated. 相似文献
289.
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
290.
This article describes the first results from the recent revision to The ONS classification of local and health authorities of Great Britain to allow for boundary changes. For each local and health authority of Great Britain as at April 1999 it presents 'most similar' authorities as measured by a selection of 37 socioeconomic and demographic variables from the 1991 Census. These results will assist local and health authorities in identifying other appropriate authorities for comparative studies. A second article, to be published in Population Trends 99, will present the results of the analysis to identify groups of authorities in a hierarchy of new Clusters, Groups and Families for the revised classification. 相似文献