全文获取类型
收费全文 | 2345篇 |
免费 | 92篇 |
国内免费 | 29篇 |
专业分类
管理学 | 259篇 |
民族学 | 12篇 |
人口学 | 96篇 |
丛书文集 | 169篇 |
理论方法论 | 98篇 |
综合类 | 1151篇 |
社会学 | 146篇 |
统计学 | 535篇 |
出版年
2024年 | 3篇 |
2023年 | 19篇 |
2022年 | 26篇 |
2021年 | 43篇 |
2020年 | 55篇 |
2019年 | 40篇 |
2018年 | 60篇 |
2017年 | 85篇 |
2016年 | 87篇 |
2015年 | 86篇 |
2014年 | 141篇 |
2013年 | 251篇 |
2012年 | 175篇 |
2011年 | 157篇 |
2010年 | 164篇 |
2009年 | 111篇 |
2008年 | 106篇 |
2007年 | 148篇 |
2006年 | 133篇 |
2005年 | 122篇 |
2004年 | 94篇 |
2003年 | 82篇 |
2002年 | 54篇 |
2001年 | 62篇 |
2000年 | 45篇 |
1999年 | 32篇 |
1998年 | 15篇 |
1997年 | 15篇 |
1996年 | 7篇 |
1995年 | 14篇 |
1994年 | 7篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1983年 | 3篇 |
排序方式: 共有2466条查询结果,搜索用时 875 毫秒
1.
《Risk analysis》2018,38(9):1988-2009
Harbor seals in Iliamna Lake, Alaska, are a small, isolated population, and one of only two freshwater populations of harbor seals in the world, yet little is known about their abundance or risk for extinction. Bayesian hierarchical models were used to estimate abundance and trend of this population. Observational models were developed from aerial survey and harvest data, and they included effects for time of year and time of day on survey counts. Underlying models of abundance and trend were based on a Leslie matrix model that used prior information on vital rates from the literature. We developed three scenarios for variability in the priors and used them as part of a sensitivity analysis. The models were fitted using Markov chain Monte Carlo methods. The population production rate implied by the vital rate estimates was about 5% per year, very similar to the average annual harvest rate. After a period of growth in the 1980s, the population appears to be relatively stable at around 400 individuals. A population viability analysis assessing the risk of quasi‐extinction, defined as any reduction to 50 animals or below in the next 100 years, ranged from 1% to 3%, depending on the prior scenario. Although this is moderately low risk, it does not include genetic or catastrophic environmental events, which may have occurred to the population in the past, so our results should be applied cautiously. 相似文献
2.
Open innovation and absorptive capacity are two concepts based on the idea that companies can leverage the knowledge generated externally to improve their innovation performance. The aim of this paper is to analyse the joint effect of open innovation and absorptive capacity on a firm's radical innovation. Open innovation is expressed in terms of external search breadth and depth strategies and absorptive capacity is described by distinguishing between potential and realized absorptive capacity. In order to test our hypotheses, we carried out empirical research in firms operating in high-technology industries. The results indicate that internal routines and processes for absorbing external knowledge help explain radical innovation as they show a significant effect of potential and realized absorptive capacity. Also, there is a moderating effect of absorptive capacity on open innovation. Specifically, potential absorptive capacity exerts a positive effect on the relationship between external search breadth and depth and radical innovation. Realized absorptive capacity moderates the influence of external search breadth. These findings confirm the complementary nature of absorptive capacity and open innovation search strategies on radical innovation. 相似文献
3.
The widely used empirical Bayes (EB) and full Bayes (FB) methods for before–after safety assessment are sometimes limited because of the extensive data needs from additional reference sites. To address this issue, this study proposes a novel before–after safety evaluation methodology based on survival analysis and longitudinal data as an alternative to the EB/FB method. A Bayesian survival analysis (SARE) model with a random effect term to address the unobserved heterogeneity across sites is developed. The proposed survival analysis method is validated through a simulation study before its application. Subsequently, the SARE model is developed in a case study to evaluate the safety effectiveness of a recent red‐light‐running photo enforcement program in New Jersey. As demonstrated in the simulation and the case study, the survival analysis can provide valid estimates using only data from treated sites, and thus its results will not be affected by the selection of defective or insufficient reference sites. In addition, the proposed approach can take into account the censored data generated due to the transition from the before period to the after period, which has not been previously explored in the literature. Using individual crashes as units of analysis, survival analysis can incorporate longitudinal covariates such as the traffic volume and weather variation, and thus can explicitly account for the potential temporal heterogeneity. 相似文献
4.
风力发电技术经济分析及对策 总被引:2,自引:0,他引:2
介绍了中、美等6个国家的电力构成以及世界风能资源的分布,并对世界风能资源经济效益进行了分析,阐述了风力发电的前景,指出了我国风电产业存在的问题,并提出发展我国风电产业的建议:研发大型风电机组,强化环保法规及给予风电产业以优惠政策. 相似文献
5.
龙之辉 《西南石油大学学报(社会科学版)》2008,17(3):114-118
本文通过对压井循环过程的分析,建立了常规压井循环应满足的基本关系,并通过对基本关系的分析,提出了实际压井循环排量应取压井循环允许的最大排量,并给出了求取实际压井循环排量的方法和实例,最后对循环排气时的环空安全问题提出了考查办法。 相似文献
6.
根据先前的研究 ,从企业核心能力的角度阐述了自知识能力的本质特征 ,即动态的特征、宽泛的特征、深层次的特征。分析了扼杀企业自知识能力的因素 ,包括企业文化因素、组织结构设计因素、分析性思维因素、策略性决策因素、激励性体系因素等五个方面。在此基础上提出了提升企业自知识能力的对策。 相似文献
7.
以核心竞争力为导向的企业并购策略研究 总被引:4,自引:0,他引:4
陈云华 《四川大学学报(哲学社会科学版)》2004,(2):20-23
对在市场经济条件下企业核心竞争力形成的途径之一———并购进行研究。从并购企业的目标选择到具体实现并购以及并购后的整合等进行分析,指出并购是公司构筑核心竞争力的必由之路。 相似文献
8.
技术创新是制造企业发展的原动力和核心竞争力.培养员工的创新精神,营造有利于创新的企业文化环境,制定符合制造企业发展要求的创新策略,建立鼓励创新的管理机制和创新能力评价体系是提高制造企业创新能力的关键. 相似文献
9.
在市场竞争日益激烈的今天,企业核心竞争力的培育无疑成为众多企业关注的焦点。本文运用比较分析方法论述了宗申集团的核心竞争力创新模式。在借鉴与分析海尔集团核心竞争力的基础上,对宗申集团的创新模式提出了几点建议。 相似文献
10.
Kenichi Ozaki 《Researches on Population Ecology》1993,35(2):273-284
Summary The number of larvae reaching maturity within the gall ofAdelges japonicus was positively related to gall volume, and the relationship between the number of mature larvae and gall volume did not change
with different densities of colonized larvae.
The population changes in the bud galls ofA. japonicus were surveyed by collecting the galls, which did not suffer predation or parasitism within the galls, from young artificial
plantations ofPicea jezoensis over two years. In the year when the density of colonized larvae was high, they suffered a 42% mortality within the galls,
whereas mortality was nearly zero in the low density year. The numbers of larvae per gall were positively correlated with
gall volume. The regression lines of the number of colonized larvae on gall volume did not differ significantly in the regression
coefficients between the two years, whereas the intercept was significantly higher in the year when the density of colonized
larvae was higher. However, different within-gall mortality nullified this difference, and the regression lines of the number
of mature larvae on gall volume had no significant difference both in the regression coefficients and the intercepts. This
suggests that the number of mature larvae per gall was limited by available resources within the gall which were positively
related to gall volume. In 25% of the galls in which mature larvae inhabited, the space within the galls were completely filled
by the larvae, indicating that space was one of the limiting resources. Gall volume also affected the number of adults that
emerged from the gall and the potential number of their progeny. 相似文献