全文获取类型
收费全文 | 61469篇 |
免费 | 4952篇 |
国内免费 | 2702篇 |
学科分类
工业技术 | 69123篇 |
出版年
2024年 | 117篇 |
2023年 | 956篇 |
2022年 | 1460篇 |
2021年 | 2361篇 |
2020年 | 1825篇 |
2019年 | 1620篇 |
2018年 | 1843篇 |
2017年 | 2037篇 |
2016年 | 1827篇 |
2015年 | 2366篇 |
2014年 | 3009篇 |
2013年 | 3493篇 |
2012年 | 3704篇 |
2011年 | 4045篇 |
2010年 | 3697篇 |
2009年 | 3314篇 |
2008年 | 3277篇 |
2007年 | 3232篇 |
2006年 | 3219篇 |
2005年 | 2792篇 |
2004年 | 2050篇 |
2003年 | 2155篇 |
2002年 | 2487篇 |
2001年 | 2086篇 |
2000年 | 1616篇 |
1999年 | 1707篇 |
1998年 | 1252篇 |
1997年 | 1071篇 |
1996年 | 1099篇 |
1995年 | 846篇 |
1994年 | 626篇 |
1993年 | 466篇 |
1992年 | 361篇 |
1991年 | 272篇 |
1990年 | 205篇 |
1989年 | 165篇 |
1988年 | 152篇 |
1987年 | 86篇 |
1986年 | 69篇 |
1985年 | 37篇 |
1984年 | 30篇 |
1983年 | 23篇 |
1982年 | 24篇 |
1981年 | 13篇 |
1980年 | 21篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1974年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 406 毫秒
31.
为优化液相法一步制备磷酸铁锂(LiFePO4)技术,以七水合硫酸亚铁、磷酸二氢铵、一水合氢氧化锂为原料,通过添加十二烷基苯磺酸钠(SDBS)作为表面活性剂,采用液相水热法合成技术,一步合成了LiFePO4正极材料。研究了水热法一步合成技术对LiFePO4材料的组成、结构、形貌、粒度等的影响,通过电感耦合等离子体发射光谱仪(ICP-OES)、X射线衍射仪(XRD)、扫描电镜(SEM)、粒度分析仪等对材料进行了表征分析,并测试了材料的电化学性能。研究结果表明,合成得到的LiFePO4材料为微米级球形颗粒形貌的正交晶系非化学计量比的Li1.02Fe0.994PO4材料。电化学性能测试结果表明,在0.1C倍率下首次充、放电比容量分别为162.0、159.9 mA·h/g,库伦效率达到98.7%、倍率性能(以1C/0.1C保持率计)为92.3%,0.1C倍率循环100次容量保持率为96.4%,展现出良好的电化学性能。 相似文献
32.
Yude Ji Yanping Guo Yuejuan Liu Yun Tian 《International Journal of Adaptive Control and Signal Processing》2020,34(3):283-297
This article focuses on the consensus problem of leader-following fractional-order multi-agent systems (MASs) with general linear and Lipschitz nonlinear dynamics. First, the distributed adaptive protocols for linear and nonlinear fractional-order MASs are constructed, respectively. We allow the control coupling gains to be time varying for each agent. Moreover, the adaptive modification schemes for the control gain are designed, which renders smaller control gains and thus requires smaller amplitude on the control input without sacrificing consensus convergence. Second, based on fractional-order Lyapunov stability theorem and Barbalat's lemma, two novel sufficient conditions in terms of linear matrix inequalities are provided to ensure that the leader-following consensus can be obtained in the case for any undirected connected communication graph. Furthermore, we show that the proposed algorithm also works for consensus of agents with intrinsic Lipschitz nonlinear dynamics. As a result, the proposed framework requires no global information and thus can be implemented in a fully distributed manner. Finally, the numerical simulations are given to demonstrate the effectiveness of obtained the theoretical results. 相似文献
33.
为进一步摸清国家核应急医学救援分队能力建设现状,国家核应急响应技术支持中心建立了评估指标体系、评分标准,对依托苏州大学附属第二医院(核工业总医院)设立的国家核应急医学救援分队开展能力评估。评估重点包括政策法规、组织机构、预案方案、指挥控制、应急设施与装备、应急响应行动和培训演练等7项一级指标。通过评估,摸清了现状,查找了问题,同时对救援方案、物资装备配备及管理、培训演练等国家核应急医学救援分队能力建设以及核应急能力评估等工作提出改进建议。 相似文献
34.
Weikang Dong Ruishi Qi Tiansheng Liu Yi Li Ning Li Ze Hua Zirui Gao Shuyuan Zhang Kaihui Liu Jiandong Guo Peng Gao 《Advanced materials (Deerfield Beach, Fla.)》2020,32(46):2002014
Hyperbolic phonon polaritons (HPhPs) in orthorhombic-phase molybdenum trioxide (α-MoO3) show in-plane hyperbolicity, great wavelength compression, and ultralong lifetime, therefore holding great potential in nanophotonic applications. However, its polaritonic response in the far-infrared (FIR) range remains unexplored due to challenges in experimental characterization. Here, monochromated electron energy loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM) is used to probe HPhPs in α-MoO3 in both mid-infrared (MIR) and FIR frequencies and correlate their behaviors with microstructures and orientations. It is found that low structural symmetry leads to various phonon modes and multiple Reststrahlen bands (RBs) over a broad spectral range (over 70 meV) and in different directions (55–63 meV and 119–125 meV along the b-axis, 68–106 meV along the c-axis, and 101–121 meV along the a-axis). These HPhPs can be selectively excited by controlling the direction of swift electrons. These findings provide new opportunities in nanophotonic and optoelectronic applications, such as directed light propagation, hyperlenses, and heat transfer. 相似文献
35.
Yong Xu Yun Li Songlin Li Francis Balestra Gerard Ghibaudo Wenwu Li Yen‐Fu Lin Huabin Sun Jing Wan Xinran Wang Yufeng Guo Yi Shi Yong‐Young Noh 《Advanced functional materials》2020,30(20)
Unreliable mobility values, and particularly greatly overestimated values and severely distorted temperature dependences, have recently hampered the development of the organic transistor field. Given that organic field‐effect transistors (OFETs) have been routinely used to evaluate mobility, precise parameter extraction using the electrical properties of OFETs is thus of primary importance. This review examines the origins of the various mobilities that must be determined for OFET applications, the relevant extraction methods, and the data selection limitations, which help in avoiding conceptual errors during mobility extraction. For increased precision, the review also discusses device fabrication considerations, calibration of both the specific gate‐dielectric capacitance and the threshold voltage, the contact effects, and the bias and temperature dependences, which must actually be handled with great care but have mostly been overlooked to date. This review serves as a systematic overview of the OFET mobility extraction process to ensure high precision and will also aid in improving future research. 相似文献
36.
以钴粉/镍箔为复合中间层,采用800,900和1 000 ℃等三种连接温度,加压10 MPa并保温120 min的工艺条件,对钨/钢真空扩散连接. 研究了接头的微观组织、成分分布、力学性能及断口特征. 结果表明,连接温度为800 ℃和900 ℃时,钨/中间层界面金属间化合物生成很少,对应接头抗剪强度分别为186 MPa和172 MPa,断口均位于钨母材中近界面的位置,为典型解理断裂形貌;当连接温度升至1 000 ℃时,钨/中间层界面生成厚度小于2 μm的连续金属间化合物层,接头抗剪强度降至115 MPa,断裂也发生在钨母材中近界面的位置,断口大部分区域为沿晶断裂特征. 相似文献
37.
38.
39.
40.