全文获取类型
收费全文 | 38056篇 |
免费 | 3163篇 |
国内免费 | 1915篇 |
专业分类
电工技术 | 2219篇 |
技术理论 | 4篇 |
综合类 | 4371篇 |
化学工业 | 7061篇 |
金属工艺 | 2571篇 |
机械仪表 | 1538篇 |
建筑科学 | 3450篇 |
矿业工程 | 1597篇 |
能源动力 | 1338篇 |
轻工业 | 4233篇 |
水利工程 | 1255篇 |
石油天然气 | 2106篇 |
武器工业 | 223篇 |
无线电 | 1842篇 |
一般工业技术 | 3569篇 |
冶金工业 | 2663篇 |
原子能技术 | 425篇 |
自动化技术 | 2669篇 |
出版年
2024年 | 76篇 |
2023年 | 345篇 |
2022年 | 709篇 |
2021年 | 948篇 |
2020年 | 1023篇 |
2019年 | 889篇 |
2018年 | 804篇 |
2017年 | 1024篇 |
2016年 | 1134篇 |
2015年 | 1234篇 |
2014年 | 2289篇 |
2013年 | 2285篇 |
2012年 | 2901篇 |
2011年 | 3098篇 |
2010年 | 2217篇 |
2009年 | 2289篇 |
2008年 | 1969篇 |
2007年 | 2503篇 |
2006年 | 2375篇 |
2005年 | 2024篇 |
2004年 | 1759篇 |
2003年 | 1531篇 |
2002年 | 1312篇 |
2001年 | 1119篇 |
2000年 | 963篇 |
1999年 | 813篇 |
1998年 | 568篇 |
1997年 | 538篇 |
1996年 | 454篇 |
1995年 | 403篇 |
1994年 | 341篇 |
1993年 | 231篇 |
1992年 | 196篇 |
1991年 | 175篇 |
1990年 | 143篇 |
1989年 | 114篇 |
1988年 | 101篇 |
1987年 | 49篇 |
1986年 | 26篇 |
1985年 | 27篇 |
1984年 | 28篇 |
1983年 | 19篇 |
1982年 | 26篇 |
1981年 | 9篇 |
1980年 | 6篇 |
1979年 | 10篇 |
1959年 | 7篇 |
1957年 | 3篇 |
1955年 | 5篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
2.
Jia Dai Xiang Cheng Xiaofeng Li Zhisheng Wang Yufeng Wang Jing Zheng Jun Liu Jiawei Chen Changjin Wu Jinyao Tang 《Advanced functional materials》2021,31(48):2106204
Synthetic active matters are perfect model systems for non-equilibrium thermodynamics and of great potential for novel biomedical and environmental applications. However, most applications are limited by the complicated and low-yield preparation, while a scalable synthesis for highly functional microswimmers is highly desired. In this paper, an all-solution synthesis method is developed where the gold-loaded titania-silica nanotree can be produced as a multi-functional self-propulsion microswimmer. By applying light, heat, and electric field, the Janus nanotree demonstrated multi-mode self-propulsion, including photochemical self-electrophoresis by UV and visible light radiation, thermophoresis by near-infrared light radiation, and induced-charge electrophoresis under AC electric field. Due to the scalable synthesis, the Janus nanotree is further demonstrated as a high-efficiency, low-cost, active adsorbent for water decontamination, where the toxic mercury ions can be reclaimed with enhanced efficiency. 相似文献
3.
本文分析了乌兰矿投产前期采矿现状及存在的主要问题,针对该矿所处蒙古国经济落后、投资风险大的现实状况,为避免生产中断、规避投资风险,早日回收前期投资考虑,采取了双斜坡道开拓、全尾胶结充填、高端壁空场嗣后充填采矿、多中段组合式连续开采等系列技术应对方案。大大降低了一次性投资规模及投资风险,前期投资得以快速回笼的同时,矿山产能也充分释放,确保了矿山的持续稳定,取得了较好的经济和社会效益。为海外地下近地表矿体开采矿山规避投资风险提供了很好的技术方案借鉴。 相似文献
4.
为了建立适用于书画打印宣纸印刷质量的预测模型,本研究测量了14种书画打印宣纸的粗糙度、白度、不透明度、定量、光泽度和针对宣纸特别设定的帘纹深浅以及帘纹疏密度等表面物理参量,并在相同条件下,使用喷墨打印设备输出并测量印品色度值,利用总变差模型构建去除帘纹色差的测定方法,得到与人眼视觉特征相符的色差。运用GRNN广义回归神经网络结合书画打印宣纸表面物理参量与宣纸去帘纹后的色差值,建立预测模型。结果表明,该模型能够在仅测量书画打印宣纸表面物理参量的情况下,便能较为准确地预测书画打印宣纸印刷质量,为书画打印宣纸印刷前的选纸工作提供指导依据。 相似文献
5.
Somnath Karmakar 《Polycyclic Aromatic Compounds》2019,39(2):159-171
Eigensolutions of {X( = C,B,N),Y( = C,B,N)}-cyclacene graphs with next nearest neighbor (nnn) interactions have been obtained in analytical forms by adapting n-fold rotational symmetry followed by two-fold rotational symmetry (or a plane of symmetry). Expressions of eigensolution indicate the subspectral relationship among such cyclacenes with an even number of hexagonal rings e.g., eigenvalues of {X,Y}-di-cyclacene are found in the eigenspectra of all such even cyclacenes. Total π-electron energies and highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO–LUMO) gaps are calculated using the analytical expressions obtained and are found to vary negligibly with the variation of nnn interactions in such cyclacenes. Total π-electron energy is found to increase due to increase in restriction intensity of nnn interactions, whereas the HOMO–LUMO gap of polyacenecs having the even number of hexagonal rings and with one electron at each site (atom) decreases with increase in the restriction intensity since such systems contain degenerate half-filled HOMO (bonding or nonbonding) that are much more vulnerable for perturbations imposed through nnn interactions. 相似文献
6.
7.
Most real-world vehicle nodes can be structured into an interconnected network of vehicles. Through structuring these services and vehicle device interactions into multiple types, such internet of vehicles becomes multidimensional heterogeneous overlay networks. The heterogeneousness of the overlays makes it difficult for the overlay networks to coordinate with each other to improve their performance. Therefore, it poses an interesting but critical challenge to the effective analysis of heterogeneous virtual vehicular networks. A variety of virtual vehicular networks can be easily deployed onto the native network by applying the concept of SDN (Software Defined Networking). These virtual networks reflect their heterogeneousness due to their different performance goals, and they compete for the same physical resources of the underlying network, so that a sub-optimal performance of the virtual networks may be achieved. Therefore, we propose a Deep Reinforcement Learning (DRL) approach to make the virtual networks cooperate with each other through the SDN controller. A cooperative solution based on the asymmetric Nash bargaining is proposed for co-existing virtual networks to improve their performance. Moreover, the Markov Chain model and DRL resolution are introduced to leverage the heterogeneous performance goals of virtual networks. The implementation of the approach is introduced, and simulation results confirm the performance improvement of the latency sensitive, loss-rate sensitive and throughput sensitive heterogeneous vehicular networks using our cooperative solution. 相似文献
8.
9.
一个完整枪支(弹药)库室的安全防范由管理要求、物防要求、技防要求及人防要求完美的结合而成,其中技防要求是需要根据枪支(弹药)库室现场实体情况采取的一项电子技术手段,是起到安全预报警的最佳方式。本文就枪支(弹药)库室安全防范在技防要求方面按现行GA 1016-2012标准在检测中存在的问题做一些探讨、建议,以期为需要枪支(弹药)库室的建设单位、施工单位提供参考。 相似文献
10.
本文提出了将智能全站仪这种精密测量仪器广泛应用于田赛项目测量中,并结合其他科技元素用于解决田赛项目中跳远、投掷等项目的测量及数据管理问题,实现实时、自动、准确地裁定和报告比赛成绩。 相似文献