全文获取类型
收费全文 | 107585篇 |
免费 | 13655篇 |
国内免费 | 9121篇 |
专业分类
电工技术 | 9924篇 |
综合类 | 10927篇 |
化学工业 | 13286篇 |
金属工艺 | 7453篇 |
机械仪表 | 7492篇 |
建筑科学 | 8304篇 |
矿业工程 | 3934篇 |
能源动力 | 2794篇 |
轻工业 | 11736篇 |
水利工程 | 3807篇 |
石油天然气 | 4092篇 |
武器工业 | 1608篇 |
无线电 | 12009篇 |
一般工业技术 | 9830篇 |
冶金工业 | 4982篇 |
原子能技术 | 2108篇 |
自动化技术 | 16075篇 |
出版年
2024年 | 686篇 |
2023年 | 1927篇 |
2022年 | 4678篇 |
2021年 | 6120篇 |
2020年 | 4291篇 |
2019年 | 3154篇 |
2018年 | 3272篇 |
2017年 | 3759篇 |
2016年 | 3228篇 |
2015年 | 5124篇 |
2014年 | 6185篇 |
2013年 | 7244篇 |
2012年 | 8875篇 |
2011年 | 9330篇 |
2010年 | 8955篇 |
2009年 | 8254篇 |
2008年 | 8465篇 |
2007年 | 7890篇 |
2006年 | 6788篇 |
2005年 | 5564篇 |
2004年 | 3899篇 |
2003年 | 2753篇 |
2002年 | 2715篇 |
2001年 | 2425篇 |
2000年 | 1757篇 |
1999年 | 767篇 |
1998年 | 503篇 |
1997年 | 316篇 |
1996年 | 247篇 |
1995年 | 181篇 |
1994年 | 145篇 |
1993年 | 142篇 |
1992年 | 72篇 |
1991年 | 73篇 |
1990年 | 64篇 |
1989年 | 83篇 |
1988年 | 37篇 |
1987年 | 32篇 |
1986年 | 38篇 |
1985年 | 20篇 |
1984年 | 8篇 |
1983年 | 10篇 |
1982年 | 14篇 |
1981年 | 24篇 |
1980年 | 40篇 |
1979年 | 23篇 |
1977年 | 43篇 |
1976年 | 81篇 |
1959年 | 21篇 |
1951年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
2.
急性下壁心肌梗死是一种病发急、进展快、致死率高的心脏疾病,该文提出一种新颖的基于形态特征提取的BiLSTM神经网络分类的急性下壁心肌梗死辅助诊断算法,可大幅度提高医生对急性下壁心肌梗死疾病的诊断效率并有助于及时确诊.算法包括:对胸痛中心数据库心拍信号进行降噪及心拍分割;根据临床心内科医学诊断指南提取了12导联波形距离特征和分导联波形幅值特征;依据提取的特征搭建LSTM与BiLSTM神经网络进行心拍的分类识别;使用PTB公开数据库和胸痛中心数据库多临床中心进行交叉验证.实验结果表明,加入胸痛中心真实临床数据后,基于形态特征提取BiLSTM神经网络的急性下壁心肌梗死辅助诊断算法准确率达到99.72%,精度达到99.53%,灵敏度达到100.00%,同时F1-Score达到99.76.该算法比其他现有算法准确率提高至少1%,该项研究具有非常重要的临床应用价值. 相似文献
3.
Yixuan ZHOU Huajie WANG Yi YU Yihang CHEN Rui KE Min XU Chijie XIAO Zhanhui WANG Jiquan LI Xuru DUAN Minyou YE 《等离子体科学和技术》2021,23(7):75105-52
In this article, we present the optical design of a novel diagnostic on the HL-2 A tokamak, i.e. the20-channel edge Lyman-alpha beam emission spectroscopy, which is a promising solution for edge density turbulence research on tokamaks, as it offers the possibility of density fluctuation measurement with a 3.3 mm spatial resolution while maintains a high temporal resolution of1 μs. The optical path, including the reflective collection optics, the high-dispersion spectrometer, and the linear detector array, is carefully optimized to obtain a good image quality and a high throughput. The maximum root mean square radius of the collection optics is 64 μm.The detected photon flux is estimated to be about 10~(11) photons/s/channel. 相似文献
4.
为解决电镀砂轮磨削加工中容屑空间不足的问题,采用点胶微粘接的方法制备了磨料有序排布的电镀砂轮,分析了磨料粘接效果和镀层力学性能。通过SEM分析了磨料/镀层/导电胶的结合界面,并进行了干磨削试验。研究结果表明,直径约为磨料粒径40%的胶点可粘接住磨料,单个胶点上粘接多颗磨料的占比小于6%;双脉冲电镀工艺制备的镀层显微硬度大于500HV,表层残余应力小于100MPa,磨料/镀层/导电胶之间的界面贴合紧密,无明显缺陷;砂轮在磨削时没有出现磨料脱落现象。 相似文献
6.
7.
Peng Li Haibin Jiang Ariel Barr Zhichu Ren Rui Gao Hua Wang Weiwei Fan Meifang Zhu Guiyin Xu Ju Li 《Advanced functional materials》2021,31(51):2105845
Mercury, lead, and cadmium are among the most toxic and carcinogenic heavy metal ions (HMIs), posing serious threats to the sustainability of aquatic ecosystems and public health. There is an urgent need to remove these ions from water by a cheap but green process. Traditional methods have insufficient removal efficiency and reusability. Structurally robust, large surface-area adsorbents functionalized with high-selectivity affinity to HMIs are attractive filter materials. Here, an adsorbent prepared by vulcanization of polyacrylonitrile (PAN), a nitrogen-rich polymer, is reported, giving rise to PAN-S nanoparticles with cyclic π-conjugated backbone and electronic conductivity. PAN-S can be coated on ultra-robust melamine (ML) foam by simple dipping and drying. In agreement with hard/soft acid/base theory, N- and S-containing soft Lewis bases have strong binding to Hg2+, Pb2+, Cu2+, and Cd2+, with extraordinary capture efficiency and performance stability. Furthermore, the used filters, when collected and electrochemically biased in a recycling bath, can release the HMIs into the bath and electrodeposit on the counter-electrode as metallic Hg0, Pb0, Cu0, and Cd0, and the PAN-S@ML filter can then be reused at least 6 times as new. The electronically conductive PAN-S@ML filter can be fabricated cheaply and holds promise for scale-up applications. 相似文献
8.
Chaozhong Sun Xiaoying Guo Rui Ji Changzheng Hu Laijun Liu Liang Fang Zhenxiang Cheng Nengneng Luo 《Ceramics International》2021,47(4):5038-5043
The triboelectric effect has recently demonstrated its great potential in environmental remediation and even new energy applications for triggering a number of catalytic reactions by utilizing trivial mechanical energy. In this study, Ba4Nd2Fe2Nb8O30 (BNFN) submicron powders were used to degrade organic dyes via the tribocatalytic effect. Under the frictional excitation of three PTFE stirring rods in a 5 mg/L RhB dye solution, BNFN demonstrates a high tribocatalytic degradation efficiency of 97% in 2 h. Hydroxyl radicals (?OH) and superoxide radicals (?O2-) were also detected during the catalysis process, which proves that triboelectric energy stimulates BNFN to generate electron-hole pairs. The tribocatalysis of tungsten bronze BNFN submicron powders provides a novel and efficient method for the degradation of wastewater dye by utilizing trivial mechanical energy. 相似文献
9.
Jieyi Yu Xianguo Liu Rui Su Xuefeng Zhang Xinglong Dong 《Ceramics International》2021,47(17):23950-23957
Increasing the dielectric loss capacity plays an important role in enhancing the electromagnetic absorption performance of materials. It remains a challenge to simultaneously introduce multiple types of dielectric losses in the material. In this work, we show that the atomic and interfacial dipole polarizations can be simultaneously enhanced by substituting N species into both carbon coating layers and bulk TiC lattices of a core-shell TiC@C material. Additionally, substitution of N species results more exposed TiC(111) facets and refines the TiC grain sizes in the bulk material, which is beneficial for enhancing the scattering of the external electromagnetic waves. The maximum reflection loss of the N substituted TiC@C material is measured as ?47.1 dB with an effective absorbing bandwidth of 4.83 GHz at 1.9 mm, which illustrates a valuable way to further tuning the electromagnetic absorption performance of this type of materials. 相似文献
10.
在公交时间表下给定起始和目标站点,路径规划查询返回一组到达时间早和换乘次数少的帕雷托最优路径.现有的索引方法需要大量运行时内存.本文提出主存空间高效的索引方法(a-)PAINT.(a-)PAINT对每个站点v预计算一组标签,使得对于从站点s到站点d的查询可以通过匹配s和d相关的标签高效地生成查询结果的一条路径.PAINT对任意查询返回最优路径.a-PAINT只需要很小的预处理开销,但可能返回多一趟换乘的次优路径.用真实的公交时间表与模拟查询测试,PAINT具有合理的预处理开销.a-PAINT需要更少量的预处理开销,在大规模公交网络下准确率达90%. 相似文献