全文获取类型
收费全文 | 80269篇 |
免费 | 8917篇 |
国内免费 | 4703篇 |
专业分类
电工技术 | 5891篇 |
技术理论 | 6篇 |
综合类 | 6630篇 |
化学工业 | 12782篇 |
金属工艺 | 4476篇 |
机械仪表 | 5098篇 |
建筑科学 | 6671篇 |
矿业工程 | 2383篇 |
能源动力 | 2580篇 |
轻工业 | 6891篇 |
水利工程 | 1782篇 |
石油天然气 | 3536篇 |
武器工业 | 1001篇 |
无线电 | 9433篇 |
一般工业技术 | 8965篇 |
冶金工业 | 2942篇 |
原子能技术 | 1116篇 |
自动化技术 | 11706篇 |
出版年
2024年 | 247篇 |
2023年 | 1596篇 |
2022年 | 3035篇 |
2021年 | 4382篇 |
2020年 | 3144篇 |
2019年 | 2575篇 |
2018年 | 2753篇 |
2017年 | 2976篇 |
2016年 | 2590篇 |
2015年 | 3815篇 |
2014年 | 4533篇 |
2013年 | 5243篇 |
2012年 | 5982篇 |
2011年 | 6126篇 |
2010年 | 5701篇 |
2009年 | 5406篇 |
2008年 | 5122篇 |
2007年 | 4462篇 |
2006年 | 4215篇 |
2005年 | 3426篇 |
2004年 | 2442篇 |
2003年 | 2015篇 |
2002年 | 2172篇 |
2001年 | 1895篇 |
2000年 | 1482篇 |
1999年 | 1374篇 |
1998年 | 965篇 |
1997年 | 816篇 |
1996年 | 747篇 |
1995年 | 573篇 |
1994年 | 513篇 |
1993年 | 355篇 |
1992年 | 294篇 |
1991年 | 220篇 |
1990年 | 158篇 |
1989年 | 144篇 |
1988年 | 89篇 |
1987年 | 63篇 |
1986年 | 54篇 |
1985年 | 32篇 |
1984年 | 24篇 |
1983年 | 18篇 |
1982年 | 21篇 |
1981年 | 15篇 |
1980年 | 28篇 |
1979年 | 13篇 |
1974年 | 3篇 |
1970年 | 2篇 |
1959年 | 10篇 |
1951年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
31.
33.
Science China Technological Sciences - Accurate modelling of lithium ion batteries is crucial for battery management in electric vehicles. Recent studies have revealed the fractional order nature... 相似文献
34.
董家埝银矿是豫西小秦岭矿集区南成矿带目前发现的唯一大型矿床。为了矿床深部勘查工作的顺利进行,了解有用元素在垂向上的变化规律,选用原生晕地球化学方法,通过典型矿床剖面的原生晕特征研究,实现对深部矿体变化趋势的判断。经计算,确定As、Sb、Ag、Au、Cu、Pb、Zn、Co和Mo等9种元素可作为指示元素,其中As和Sb为前缘晕指示元素,Ag、Au、Cu、Pb和Zn为近矿晕指示元素,Co和Mo为尾晕指示元素。分带指数和浓集指数2种方法计算得出的元素在分带序列上的位置总体趋势一致。用分带指数法确定的主矿体自上而下的原生晕轴向分带序列为Co-Mo-Cu-Au-Sb-Zn-Pb-Ag-As,出现"反分带"现象。结合原生晕地球化学参数变化特征、矿体剥蚀程度研究和理想模型,预测M1-I主矿体向深部仍有较大的延伸。研究成果可以为区域同类型矿化地质体深部的趋势判断和决策提供参考。 相似文献
35.
反应堆屏蔽计算中经常出现厚屏蔽、小探测器问题,常规蒙特卡罗方法难以有效解决。基于自动重要抽样(AIS)方法,本文提出了小探测器自动重要抽样(SDAIS)方法,并针对小探测器问题,优化了AIS方法的虚粒子赌分裂算法。该方法在自主开发的蒙特卡罗屏蔽程序MCShield上进行了实现。使用NUREG/CR-6115 PWR基准题验证该方法的正确性和计算效率。结果表明,SDAIS方法可有效地解决厚屏蔽小探测器问题,相比AIS方法及传统的重要性方法,计算效率提升1~2个量级。 相似文献
36.
在新型二次电池产业的发展中,氢镍电池市场不断萎缩,锂离子电池市场正处于黄金时代。通过对日本和中国新型二次电池产业发展历程分析,我国主要针对低端市场,高端市场为日本占据,并从日本发展经验中提出了可供我国锂离子电动车电池发展的借鉴之处。 相似文献
37.
Xiaoyan Qiu Yongqiang Zhang Haitao Wu Rui Yang Jun Yang Rongjuan Liu Yong Liu Zhiping Zhou Tongfan Hao Yijing Nie 《Polymer International》2019,68(2):218-224
The crystallization of capped ultrathin polymer films is closely dependent on film thickness and interfacial interaction. Using dynamic Monte Carlo simulations, the crystallization behaviors of polymer films confined between two substrates were investigated. The crystallization rate of confined polymers is reduced with high interfacial interactions. Above a critical strength of interfacial interaction, polymer crystallization in the thin film is inhibited within the simulation time scales. An increase in film thickness leads to a rise in critical interfacial interaction. In thicker films, the chains have more space to change conformation to form crystal stems. In addition, there are fewer absorbed segments in confined chains for the thicker films, and thus the chains have stronger ability to adjust their conformation. Therefore an increase in film thickness can cause a reduction in the entropic barrier required for the formation of crystals and thus an increase in the critical interfacial interaction. © 2018 Society of Chemical Industry 相似文献
38.
Wenshu Chen Jiajun Gu Yongping Du Fang Song Fanxing Bu Jinghan Li Yang Yuan Ruichun Luo Qinglei Liu Di Zhang 《Advanced functional materials》2020,30(25)
Large‐scale production of hydrogen from water‐alkali electrolyzers is impeded by the sluggish kinetics of hydrogen evolution reaction (HER) electrocatalysts. The hybridization of an acid‐active HER catalyst with a cocatalyst at the nanoscale helps boost HER kinetics in alkaline media. Here, it is demonstrated that 1T–MoS2 nanosheet edges (instead of basal planes) decorated by metal hydroxides form highly active / heterostructures, which significantly enhance HER performance in alkaline media. Featured with rich / sites, the fabricated 1T–MoS2 QS/Ni(OH)2 hybrid (quantum sized 1T–MoS2 sheets decorated with Ni(OH)2 via interface engineering) only requires overpotentials of 57 and 112 mV to drive HER current densities of 10 and 100 mA cm?2, respectively, and has a low Tafel slope of 30 mV dec?1 in 1 m KOH. So far, this is the best performance for MoS2‐based electrocatalysts and the 1T–MoS2 QS/Ni(OH)2 hybrid is among the best‐performing non‐Pt alkaline HER electrocatalysts known. The HER process is durable for 100 h at current densities up to 500 mA cm?2. This work not only provides an active, cost‐effective, and robust alkaline HER electrocatalyst, but also demonstrates a design strategy for preparing high‐performance catalysts based on edge‐rich 2D quantum sheets for other catalytic reactions. 相似文献
39.
Requirements Engineering - In software reuse, the reuse of UML class diagram produced in design phase has received more attention due to the important influence on the following developing process.... 相似文献
40.
Rui ZHAO Weikai LI Tian WANG Ke ZHAN Zheng YANG Ya YAN Bin ZHAO Junhe YANG 《材料科学前沿(英文版)》2020,14(2):188
Effective thermal management of electronic integrated devices with high powder density has become a serious issue, which requires materials with high thermal conductivity (TC). In order to solve the problem of weak bonding between graphite and Cu, a novel Cu/graphite film/Cu sandwich composite (Cu/GF/Cu composite) with ultrahigh TC was fabricated by electro-deposition. The micro-riveting structure was introduced to enhance the bonding strength between graphite film and deposited Cu layers by preparing a rectangular array of micro-holes on the graphite film before electro-deposition. TC and mechanical properties of the composites with different graphite volume fractions and current densities were investigated. The results showed that the TC enhancement generated by the micro-riveting structure for Cu/GF/Cu composites at low graphite content was more effective than that at high graphite content, and the strong texture orientation of deposited Cu resulted in high TC. Under the optimizing preparing condition, the highest in-plane TC reached 824.3 W·m−1·K−1, while the ultimate tensile strength of this composite was about four times higher than that of the graphite film. 相似文献