全文获取类型
收费全文 | 8383篇 |
免费 | 129篇 |
国内免费 | 7篇 |
专业分类
教育 | 6140篇 |
科学研究 | 500篇 |
各国文化 | 161篇 |
体育 | 694篇 |
综合类 | 3篇 |
文化理论 | 128篇 |
信息传播 | 893篇 |
出版年
2022年 | 50篇 |
2021年 | 76篇 |
2020年 | 149篇 |
2019年 | 211篇 |
2018年 | 287篇 |
2017年 | 307篇 |
2016年 | 292篇 |
2015年 | 220篇 |
2014年 | 239篇 |
2013年 | 1830篇 |
2012年 | 227篇 |
2011年 | 228篇 |
2010年 | 208篇 |
2009年 | 181篇 |
2008年 | 278篇 |
2007年 | 209篇 |
2006年 | 207篇 |
2005年 | 192篇 |
2004年 | 150篇 |
2003年 | 182篇 |
2002年 | 163篇 |
2001年 | 132篇 |
2000年 | 116篇 |
1999年 | 112篇 |
1998年 | 105篇 |
1997年 | 108篇 |
1996年 | 115篇 |
1995年 | 122篇 |
1994年 | 116篇 |
1993年 | 92篇 |
1992年 | 110篇 |
1991年 | 105篇 |
1990年 | 101篇 |
1989年 | 91篇 |
1988年 | 84篇 |
1987年 | 70篇 |
1986年 | 65篇 |
1985年 | 72篇 |
1984年 | 60篇 |
1983年 | 75篇 |
1982年 | 73篇 |
1981年 | 78篇 |
1980年 | 82篇 |
1979年 | 74篇 |
1978年 | 54篇 |
1977年 | 44篇 |
1976年 | 52篇 |
1975年 | 43篇 |
1974年 | 40篇 |
1971年 | 29篇 |
排序方式: 共有8519条查询结果,搜索用时 0 毫秒
91.
Niall Rooney David Patterson Mykola Galushka Vladimir Dobrynin 《Information processing & management》2006
Contextual document clustering is a novel approach which uses information theoretic measures to cluster semantically related documents bound together by an implicit set of concepts or themes of narrow specificity. It facilitates cluster-based retrieval by assessing the similarity between a query and the cluster themes’ probability distribution. In this paper, we assess a relevance feedback mechanism, based on query refinement, that modifies the query’s probability distribution using a small number of documents that have been judged relevant to the query. We demonstrate that by providing only one relevance judgment, a performance improvement of 33% was obtained. 相似文献
92.
David Nicholas Paul Huntington Hamid R. Jamali Anthony Watkinson 《Information processing & management》2006
The article employs deep log analysis (DLA) techniques, a more sophisticated form of transaction log analysis, to demonstrate what usage data can disclose about information seeking behaviour of virtual scholars – academics, and researchers. DLA works with the raw server log data, not the processed, pre-defined and selective data provided by journal publishers. It can generate types of analysis that are not generally available via proprietary web logging software because the software filters out relevant data and makes unhelpful assumptions about the meaning of the data. DLA also enables usage data to be associated with search/navigational and/or user demographic data, hence the name ‘deep’. In this connection the usage of two digital journal libraries, those of EmeraldInsight, and Blackwell Synergy are investigated. The information seeking behaviour of nearly three million users is analyzed in respect to the extent to which they penetrate the site, the number of visits made, as well as the type of items and content they view. The users are broken down by occupation, place of work, type of subscriber (“Big Deal”, non-subscriber, etc.), geographical location, type of university (old and new), referrer link used, and number of items viewed in a session. 相似文献
93.
采用核心自我评价量表、工作投入量表、心理授权量表和不匹配感知量表对16家企业447名新生代员工进行调查,通过层级回归分析新生代员工核心自我评价与工作投入的关系,以及考察心理授权与过度教育在此关系中发挥的作用。结果表明:(1)新生代员工核心自我评价对工作投入有显著正向影响;(2)心理授权在核心自我评价和工作投入关系中有着部分中介效应;(3)过度教育对心理授权中介效应的调节作用成立,对过度教育的高感知不仅削弱了核心自我评价与心理授权的正向关系,也进而弱化了心理授权对工作投入的积极作用。 相似文献
94.
95.
96.
Ying Xing Zhibin Shao Jun Ge Jiawei Luo Jinhua Wang Zengwei Zhu Jun Liu Yong Wang Zhiying Zhao Jiaqiang Yan David Mandrus Binghai Yan Xiong-Jun Liu Minghu Pan Jian Wang 《国家科学评论(英文版)》2020,7(3):579
The search for unconventional superconductivity in Weyl semimetal materials is currently an exciting pursuit, since such superconducting phases could potentially be topologically non-trivial and host exotic Majorana modes. The layered material TaIrTe4 is a newly predicted time-reversal invariant type II Weyl semimetal with the minimum number of Weyl points. Here, we report the discovery of surface superconductivity in Weyl semimetal TaIrTe4. Our scanning tunneling microscopy/spectroscopy (STM/STS) visualizes Fermi arc surface states of TaIrTe4 that are consistent with the previous angle-resolved photoemission spectroscopy results. By a systematic study based on STS at ultralow temperature, we observe uniform superconducting gaps on the sample surface. The superconductivity is further confirmed by electrical transport measurements at ultralow temperature, with an onset transition temperature (Tc) up to 1.54 K being observed. The normalized upper critical field h*(T/Tc) behavior and the stability of the superconductivity against the ferromagnet indicate that the discovered superconductivity is unconventional with the p-wave pairing. The systematic STS, and thickness- and angular-dependent transport measurements reveal that the detected superconductivity is quasi-1D and occurs in the surface states. The discovery of the surface superconductivity in TaIrTe4 provides a new novel platform to explore topological superconductivity and Majorana modes. 相似文献
97.
Dong-Dong Wu Cui-Ping Yang Ming-Shan Wang Kun-Zhe Dong Da-Wei Yan Zi-Qian Hao Song-Qing Fan Shu-Zhou Chu Qiu-Shuo Shen Li-Ping Jiang Yan Li Lin Zeng He-Qun Liu Hai-Bing Xie Yun-Fei Ma Xiao-Yan Kong Shu-Li Yang Xin-Xing Dong Ali Esmailizadeh David M Irwin Xiao Xiao Ming Li Yang Dong Wen Wang Peng Shi Hai-Peng Li Yue-Hui Ma Xiao Gou Yong-Bin Chen Ya-Ping Zhang 《国家科学评论(英文版)》2020,7(6):952
Abundant and diverse domestic mammals living on the Tibetan Plateau provide useful materials for investigating adaptive evolution and genetic convergence. Here, we used 327 genomes from horses, sheep, goats, cattle, pigs and dogs living at both high and low altitudes, including 73 genomes generated for this study, to disentangle the genetic mechanisms underlying local adaptation of domestic mammals. Although molecular convergence is comparatively rare at the DNA sequence level, we found convergent signature of positive selection at the gene level, particularly the EPAS1 gene in these Tibetan domestic mammals. We also reported a potential function in response to hypoxia for the gene C10orf67, which underwent positive selection in three of the domestic mammals. Our data provide an insight into adaptive evolution of high-altitude domestic mammals, and should facilitate the search for additional novel genes involved in the hypoxia response pathway. 相似文献
98.
99.
This study aims to examine the relationships between managerial learning as a facet of knowledge absorption (KA), firm innovation as a facet of knowledge exploitation (KE), and performance of small firms (i.e., firms with fewer than 50 employees). It builds on the knowledge-based view of the firm and the upper echelons theory to describe the effects of KA on KE, and that of KE on firm performance, in the small-firm context. Using survey data of 1441 small firms in New Zealand, the study applies a partial least squares approach to structural equation modelling to test the main hypotheses of the study. The main findings show the positive and significant effects of three types of managerial learning, namely, practice-based, proximal, and distal learning, on innovation and on innovation in firm performance. However, the curvilinear relationships suggest rather that the effects are finite and, potentially, confounded by factors unaccounted for in the models. 相似文献
100.
Thanh Tin Tang Nick Craswell David Hawking Kathy Griffiths Helen Christensen 《Information Retrieval》2006,9(2):207-225
When searching for health information, results quality can be judged against available scientific evidence: Do search engines return advice consistent with evidence based medicine? We compared the performance of domain-specific health and depression search engines against a general-purpose engine (Google) on both relevance of results and quality of advice. Over 101 queries, to which the term ‘depression’ was added if not already present, Google returned more relevant results than those of the domain-specific engines. However, over the 50 treatment-related queries, Google returned 70 pages recommending for or against a well studied treatment, of which 19 strongly disagreed with the scientific evidence. A domain-specific index of 4 sites selected by domain experts was only wrong in 5 of 50 recommendations. Analysis suggests a tension between relevance and quality. Indexing more pages can give a greater number of relevant results, but selective inclusion can give better quality. 相似文献