全文获取类型
收费全文 | 9207篇 |
免费 | 780篇 |
国内免费 | 70篇 |
专业分类
化学 | 315篇 |
晶体学 | 3篇 |
力学 | 40篇 |
综合类 | 133篇 |
数学 | 2109篇 |
物理学 | 436篇 |
无线电 | 7021篇 |
出版年
2024年 | 16篇 |
2023年 | 96篇 |
2022年 | 166篇 |
2021年 | 281篇 |
2020年 | 270篇 |
2019年 | 164篇 |
2018年 | 133篇 |
2017年 | 270篇 |
2016年 | 411篇 |
2015年 | 426篇 |
2014年 | 810篇 |
2013年 | 636篇 |
2012年 | 707篇 |
2011年 | 656篇 |
2010年 | 486篇 |
2009年 | 499篇 |
2008年 | 513篇 |
2007年 | 612篇 |
2006年 | 516篇 |
2005年 | 449篇 |
2004年 | 413篇 |
2003年 | 378篇 |
2002年 | 251篇 |
2001年 | 204篇 |
2000年 | 148篇 |
1999年 | 116篇 |
1998年 | 81篇 |
1997年 | 69篇 |
1996年 | 59篇 |
1995年 | 36篇 |
1994年 | 45篇 |
1993年 | 25篇 |
1992年 | 18篇 |
1991年 | 17篇 |
1990年 | 10篇 |
1989年 | 6篇 |
1988年 | 23篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1977年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
171.
从播控管理系统的需求分析入手,构建了系统各功能模块,建立数据库,对系统登录、用户权限管理、播控资源管理等模块做了分析与设计。系统对播控信息数据进行统一管理,完成了信息的收集、统计、汇总和分析等功能,实现了对电视播控事务科学、高效的管理。 相似文献
172.
情感语声合成技术对于人机交互具有重要的意义。面对儿童情感语声合成所需汉语语声数据资源缺乏以及模型训练时长较长等问题,该文提出利用迁移学习实现汉语儿童情感语声合成的方法。首先基于汉语语声数据库训练深度学习模型实现中文语声端到端合成模型,再使用高质量大样本的中文情感语料库完成情感语声合成模型,最后利用自行采样的小样本汉语儿童情感语料对模型进行迁移学习实现低资源的语声合成。客观实验结果中梅尔倒谱失真指标为4.91,主观听辨实验指标分别为3.61和4.17。通过实验对比表明,该文的方法在情感语声合成技术的应用上具有良好的性能表现,并且优于现有先进的低资源情感语声合成方法。 相似文献
173.
Yiming Liu Stuart W. Bunting Shiming Luo Kunzheng Cai Qiangqiang Yang 《Natural Resource Modeling》2019,32(1)
Inappropriate development and overexploitation have seriously degraded aquatic resources in China. Stakeholders identified three fish stock enhancement and biodiversity conservation scenarios for the Beijiang River: S1, increased fish restocking; S2, no fishing season and habitat conservation; and S3, strict pollution control. Potential impacts of these actions on the livelihoods of fishers were evaluated using applied economic modeling. Baseline costs and benefits came from logbooks from 30 fishers and a survey of 90 households in three villages. The financial net benefit for a household was US$1583 (¥11,160) annually, representing a 142% and 387% return on capital and operating costs, respectively. Larger catches associated with S1 and S2 generated a net benefit of US$1651 and US$1822, respectively. Strict pollution control resulting in higher catches (+20%) and lower operating costs (?20%) would increase the net benefit by 15.9% to US$1835 annually. Pollution control would benefit other resource users and is a prerequisite for ecological restoration. Recommendations for Resource Managers
- Stringent pollution control measures are essential to conserve aquatic biodiversity and enhance the livelihoods of fishers but will require considerable public and private sector investment.
- Enhanced fish stocks in the Beijiang River could benefit poor livelihoods but may not be sufficient to lift households out of poverty, aged fishers require government assistance to diversify their livelihoods, access alternative urban employment, and survive with dignity.
- Adopting the economic modeling approach presented here could enable responsible authorities to simultaneously evaluate fish stock enhancement and biodiversity conservation options.
- Broader application of the approach presented here could help ensure small‐scale inland fisheries are managed sustainably and aquatic ecosystems are restored and protected by 2020, in line with Target 6 of the United Nations’ Convention on Biological Diversity Strategic Plan for Biodiversity.
174.
The performance of active queue management (AQM) is measured in terms of throughput, delay, queue size, and loss rate. We have carried out the optimized performance measure of throughput for AQM scheme random early detection (RED) using full factorial design (FDD) technique that is a new approach of performance analysis particularly for congestion control algorithms. We have considered the input factors, viz, buffer size, maximum threshold, and the number of file transfer protocol (FTP) sources for the evaluation of RED that can be used for other AQM schemes, viz, adaptive RED, three‐section RED (TRED), and adaptive queue management with random dropping (AQMRD). The effect of each input factor as well as their interactions are evaluated using factorial design technique that results to obtain the nonlinear equation for performance measure in terms of input factors buffer size, maximum threshold, and the number of FTP sources. Finally, we show the contour plots for variation of performance measure throughput (steady state) from minimum to maximum values with respect to the different setting of input parameters. 相似文献
175.
Edwin van der Werf Yonky Indrajaya Frits Mohren Ekko C. van Ierland 《Natural Resource Modeling》2019,32(4)
Using insights from the forest ecology literature, we analyze the effect of injured trees on stand composition and carbon stored in above‐ground biomass and the implications for forest management decisions. Results from a Faustmann model with data for a tropical forest on Kalimantan show that up to 50% of the basal area of the stand before harvest can consist of injured trees. Considering injured trees leads to an increase in the amount of carbon in above‐ground biomass of up to 165%. These effects are larger under reduced impact logging than under conventional logging. The effects on land expectation value and cutting cycle are relatively small. The results suggest that considering injured trees in models for tropical forest management is important for the correct assessment of the potential of financial programs to store carbon and conserve forest ecosystem services in managed tropical forests, such as reducing emissions from deforestation and forest degradation and payment for ecosystem services. Recommendations for Resource Managers
- Considering the role of injured trees is important for managing tropical forests
- These trees can cover up to 50% of basal area and contain more than 50% of the carbon stored in above‐ground biomass
- Reduced impact logging leads to a larger basal area of injured trees and more carbon stored in injured trees than conventional logging
- Injured trees play an important role when assessing the potential for carbon storage in the context of payment for forest ecosystem services.
176.
一种通信距离最小化的虚拟机分配算法 总被引:1,自引:0,他引:1
为了解决云资源分配过程中虚拟机通信距离较大,造成用户计算任务完成时间延长问题,提出一种最短通信距离的虚拟机分配算法.云资源管理器能够根据用户指定的虚拟机条件,将计算任务分割到合适的数据中心及其内部服务器,大大缩短了虚拟机之间的通信距离.仿真实验表明,与现有的贪婪算法和随机方法相比,提出的方法通信量更少,执行速度更快. 相似文献
177.
178.
计算机技术在企业经济管理中的应用探析 总被引:1,自引:0,他引:1
随着科学技术的发展,计算机技术现在已经广泛的应用在各行各业中,在企业办公、广告设计等领域中的应用,大大的提升了工作效果以及工作质量。在企业经济管理中,计算机技术具有有重要的意义和优势,为此本文针对企业的经济管理现状、计算机技术在企业经济管理中应用的意义、优势等内容进行分析,通过对当前企业经济管理存在的问题、现状等进行研究,结合计算机技术的应用优势,得出计算机技术在企业经济管理中的应用策略,希望可以全面准确的提升企业经济管理质量,并广泛的应用计算机技术。 相似文献
179.
我国正迈入快速城市化建设过程中,运用GIS技术手段来解决城市规划过程中的城市化建设进程信息整合管理,对于提高城市规划信息整合效率、避免重复建设、重叠规划、一库多建等城市规划问题有着积极意义。 相似文献
180.
随着医院信息化建设步伐的逐渐加快,HIS、LIS以及PACS等信息管理系统在医院内部各个科室的业务开展和管理中得到了非常广泛的应用。医院的信息化管理程度也在逐步深化,从而让医院内部各项业务对于信息化的依赖程度越来越高。医院信息系统的安全和稳定在很大程度上决定了医院内部各项业务是否可以正常开展,因此我们必须要做好这项工作。本文结合笔者实际工作经验,就医院信息系统(HIS)的安全管理策略提出了几点建议。 相似文献