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排序方式: 共有1599条查询结果,搜索用时 15 毫秒
91.
晋陕蒙接壤区土地退化及其治理预测 总被引:1,自引:0,他引:1
本文土地退化主要有水土流失、风蚀沙化、草场退化、此生盐渍化、土壤贫瘠化5种类型。根据土地综合评价值计算,16个县土地退化总面积21955.25km2,所造成的经济损失十分巨大。为此,提出了重点治理区和一般治理区的治理预测,其中包括治理目标、治理重点、治理措施和治理投资。 相似文献
92.
[目的/意义]构建数学模型研究网络话题传播规律建模和预测问题,为深入研究网络话题传播规律提供理论参考。[方法/过程]定性分析网络话题传播的大数据特征、可量化性、可度量周期性、可预测性等特征,通过分析网络话题传播机理,构建网络话题传播规律的常态模型和衍生模型,提出划分网络话题传播阶段的一般方法,并据此研究网络话题传播趋势预测方法。[结论/结果]通过"雾霾"微博话题数据开展实证分析,能够较好地划分传播阶段并预测传播趋势,由此,根据本文构建的数学模型研究网络话题传播规律是可行的。 相似文献
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95.
从期刊引文分析看经济学学科内部和学科间的知识交流 总被引:1,自引:0,他引:1
本文用通俗易懂的方法向一般读者介绍引文分析在经济学等方面的应用,读者可以从中了解引文的意义,认识经济学中两个重要领域在学科内和学科间知识交流中的作用。同时了解经济学与其相邻的商学学科和基本社会学科等九个学科之间知识交流的类型。 相似文献
96.
高浓度污染气象条件分析和预报 总被引:4,自引:0,他引:4
CAPPS预报系统对一、二级空气质量预报效果较好,但高浓度污染预报能力较差.从天气系统和气象条件入手,分析了高浓度污染日的成因,提出将气象条件判别方法、天气学方法和CAPPS等几种预报方法的结果进行集成预报,可以有效地提高高浓度污染预报能力。 相似文献
97.
The study examined the predictive value of adolescents’ personality trait ratings by different groups of informants in explaining academic achievement [grade point average (GPA)] while controlling for students’ sex and their mothers’ education. The Inventory of Child/Adolescent Individual Differences was employed as a measure of students’ personality traits at the end of elementary schooling (mean age = 14.7 years) and two years later when the participants attended secondary schools. The trait ratings were obtained through self‐, maternal and peer reports at both measurement occasions. They explained substantial portions of unique variance in the students’ GPA concurrently, and over time. Ratings by each of the three groups of informants had an incremental validity over one another in predicting school grades. Among personality variables, conscientiousness and low extraversion were consistently predictive of GPA. 相似文献
98.
近几年,国家对具有战略地位的职业教育重视程度日益凸显,为了避免“技工荒”,增加劳动技术含量,许多企业也对职业教育倾注了少有的热情。随着各种投入的不断加大,各项保障性法规的相继出台,使人们感觉到冰封已久的职业教育终于迎来了蓬勃发展的春天。然而由于各地政府对职业教育重要性认识的差异、职业教育院校本身的专业结构、培养人才模式等方面存在的偏差,以及农村职业教育和农村劳动力培训面临的诸多困境,致使职业教育的发展步履艰难,任重而道远。 相似文献
99.
Yu Zhang Min Wang Florian Gottwalt Morteza Saberi Elizabeth Chang 《Journal of Informetrics》2019,13(2):616-634
As the volume of scientific articles has grown rapidly over the last decades, evaluating their impact becomes critical for tracing valuable and significant research output. Many studies have proposed various ranking methods to estimate the prestige of academic papers using bibliometric methods. However, the weight of the links in bibliometric networks has been rarely considered for article ranking in existing literature. Such incomplete investigation in bibliometric methods could lead to biased ranking results. Therefore, a novel scientific article ranking algorithm, W-Rank, is introduced in this study proposing a weighting scheme. The scheme assigns weight to the links of citation network and authorship network by measuring citation relevance and author contribution. Combining the weighted bibliometric networks and a propagation algorithm, W-Rank is able to obtain article ranking results that are more reasonable than existing PageRank-based methods. Experiments are conducted on both arXiv hep-th and Microsoft Academic Graph datasets to verify the W-Rank and compare it with three renowned article ranking algorithms. Experimental results prove that the proposed weighting scheme assists the W-Rank in obtaining ranking results of higher accuracy and, in certain perspectives, outperforming the other algorithms. 相似文献
100.
《Journal of Informetrics》2019,13(2):738-750
An aspect of citation behavior, which has received longstanding attention in research, is how articles’ received citations evolve as time passes since their publication (i.e., citation ageing). Citation ageing has been studied mainly by the formulation and fit of mathematical models of diverse complexity. Commonly, these models restrict the shape of citation ageing functions and explicitly take into account factors known to influence citation ageing. An alternative—and less studied—approach is to estimate citation ageing functions using data-driven strategies. However, research following the latter approach has not been consistent in taking into account those factors known to influence citation ageing. In this article, we propose a model-free approach for estimating citation ageing functions which combines quantile regression with a non-parametric specification able to capture citation inflation. The proposed strategy allows taking into account field of research effects, impact level effects, citation inflation effects and skewness in the distribution of cites effects. To test our methodology, we collected a large dataset consisting of more than five million citations to 59,707 research articles spanning 12 dissimilar fields of research and, with this data in hand, tested the proposed strategy. 相似文献