全文获取类型
收费全文 | 7661篇 |
免费 | 335篇 |
国内免费 | 93篇 |
专业分类
管理学 | 433篇 |
劳动科学 | 10篇 |
民族学 | 137篇 |
人才学 | 1篇 |
人口学 | 161篇 |
丛书文集 | 1466篇 |
理论方法论 | 394篇 |
综合类 | 4685篇 |
社会学 | 307篇 |
统计学 | 495篇 |
出版年
2024年 | 12篇 |
2023年 | 44篇 |
2022年 | 137篇 |
2021年 | 154篇 |
2020年 | 136篇 |
2019年 | 104篇 |
2018年 | 102篇 |
2017年 | 176篇 |
2016年 | 153篇 |
2015年 | 248篇 |
2014年 | 322篇 |
2013年 | 429篇 |
2012年 | 357篇 |
2011年 | 521篇 |
2010年 | 526篇 |
2009年 | 538篇 |
2008年 | 503篇 |
2007年 | 546篇 |
2006年 | 528篇 |
2005年 | 458篇 |
2004年 | 294篇 |
2003年 | 340篇 |
2002年 | 416篇 |
2001年 | 347篇 |
2000年 | 206篇 |
1999年 | 99篇 |
1998年 | 66篇 |
1997年 | 52篇 |
1996年 | 54篇 |
1995年 | 54篇 |
1994年 | 34篇 |
1993年 | 34篇 |
1992年 | 22篇 |
1991年 | 25篇 |
1990年 | 14篇 |
1989年 | 10篇 |
1988年 | 9篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1974年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有8089条查询结果,搜索用时 15 毫秒
111.
提出了由于信息化社会、Internet、Intranet和多媒体技术的出现,从而要求卫星通信向多体制、多功能发展。文中着重分析了具有独特优点的激光通信在宽带卫星通信和星际链路中的现实商用前景。 相似文献
112.
对半导体激光器进行光学准直是空间光通信系统必须进行的重要工作。文中简述了准直通常使用的方法,测试了使用单透镜对一种35mW半导体激光器的准直结果,准直效率约为60%,准直后的发射角为04~075mrad。 相似文献
113.
114.
通过对美国西部开发和中国西部开发的对比及借鉴美国西部的经济开发策略,对中国西部的经济发展提出了采取“梯度转移”与有条件的“增长极核发展”相结合的经济发展战略模式的建议。 相似文献
115.
116.
品牌资产及其测量中的概念解析 总被引:18,自引:0,他引:18
品牌资产(品牌权益)是近年来营销领域中研究的热点问题,然而对于其基本概念的曲解却阻碍了对这个重要问题的进一步研究。本文针对品牌资产涉及的几个概念(品牌资产、品牌权益、品牌价值)及其相互关系加以解释,并将主要的品牌资产的测量方法进行分类,目的是澄清人们对于品牌资产基本概念的模糊认识,为进一步深入研究指明方向。 相似文献
117.
品牌延伸:资产价值转移与理论模型创建 总被引:5,自引:1,他引:5
本文通过对品牌延伸(Brand Extension)的研究综述和实证研究,提出决定品牌延伸的三大因子,并在此基础上构成品牌资产价值(Brand Asset Value),进而研究其在品牌延伸过程中的价值转移,从而构成了评估品牌延伸成败的标准,最终将各种因子和评估标准进行整合,提出了品牌延伸的理论模型。 相似文献
118.
Optimization Model and Algorithm for Crew Management During Airline Irregular Operations 总被引:4,自引:0,他引:4
Airline irregular operations have long been a realm where human experience and judgement are the most important tools to utilize. Crew management during irregular operations is usually the bottleneck of the whole system-recovering process due to complicated crew schedules and restrictive crew legalities as well as the size and scope of the hub-and-spoke networks adopted by major carriers. A system-wide multi-commodity integer network flow model and a heuristic search algorithm for the above purpose are presented and discussed in this paper. The computational experiences show that the algorithm is efficient enough to solve problems of realistic size and also has the flexibility to accommodate practical business requirements. 相似文献
119.
Compliance Versus Risk in Assessing Occupational Exposures 总被引:1,自引:0,他引:1
Rogelio Tornero-Velez Elaine Symanski Hans Kromhout Rong C. Yu Stephen M. Rappaport 《Risk analysis》1997,17(3):279-292
Assessments of occupational exposures to chemicals are generally based upon the practice of compliance testing in which the probability of compliance is related to the exceedance [γ, the likelihood that any measurement would exceed an occupational exposure limit (OEL)] and the number of measurements obtained. On the other hand, workers’ chronic health risks generally depend upon cumulative lifetime exposures which are not directly related to the probability of compliance. In this paper we define the probability of “overexposure” (θ) as the likelihood that individual risk (a function of cumulative exposure) exceeds the risk inherent in the OEL (a function of the OEL and duration of exposure). We regard θ as a relevant measure of individual risk for chemicals, such as carcinogens, which produce chronic effects after long-term exposures but not necessarily for acutely-toxic substances which can produce effects relatively quickly. We apply a random-effects model to data from 179 groups of workers, exposed to a variety of chemical agents, and obtain parameter estimates for the group mean exposure and the within- and between-worker components of variance. These estimates are then combined with OELs to generate estimates of γ and θ. We show that compliance testing can significantly underestimate the health risk when sample sizes are small. That is, there can be large probabilities of compliance with typical sample sizes, despite the fact that large proportions of the working population have individual risks greater than the risk inherent in the OEL. We demonstrate further that, because the relationship between θ and γ depends upon the within- and between-worker components of variance, it cannot be assumed a priori that exceedance is a conservative surrogate for overexposure. Thus, we conclude that assessment practices which focus upon either compliance or exceedance are problematic and recommend that employers evaluate exposures relative to the probabilities of overexposure. 相似文献
120.
Power assignment for wireless ad hoc networks is to assign a power for each wireless node such that the induced communication
graph has some required properties. Recently research efforts have focused on finding the minimum power assignment to guarantee
the connectivity or fault-tolerance of the network. In this paper, we study a new problem of finding the power assignment such that the induced communication graph is a spanner for the original communication graph when all nodes have the maximum power. Here, a spanner means that the length of the
shortest path in the induced communication graph is at most a constant times of the length of the shortest path in the original
communication graph. Polynomial time algorithm is given to minimize the maximum assigned power with spanner property. The
algorithm also works for any other property that can be tested in polynomial time and is monotone. We then give a polynomial time approximation method to minimize the total transmission radius of all nodes. Finally, we
propose two heuristics and conduct extensive simulations to study their performance when we aim to minimize the total assigned
power of all nodes.
The author is partially supported by NSF CCR-0311174. 相似文献