全文获取类型
收费全文 | 83481篇 |
免费 | 9567篇 |
国内免费 | 5048篇 |
专业分类
电工技术 | 7348篇 |
技术理论 | 8篇 |
综合类 | 7045篇 |
化学工业 | 11744篇 |
金属工艺 | 5050篇 |
机械仪表 | 5525篇 |
建筑科学 | 6781篇 |
矿业工程 | 3138篇 |
能源动力 | 2544篇 |
轻工业 | 6157篇 |
水利工程 | 2326篇 |
石油天然气 | 4000篇 |
武器工业 | 1077篇 |
无线电 | 9462篇 |
一般工业技术 | 8674篇 |
冶金工业 | 3380篇 |
原子能技术 | 1201篇 |
自动化技术 | 12636篇 |
出版年
2024年 | 364篇 |
2023年 | 1563篇 |
2022年 | 3288篇 |
2021年 | 4529篇 |
2020年 | 3360篇 |
2019年 | 2506篇 |
2018年 | 2802篇 |
2017年 | 3010篇 |
2016年 | 2757篇 |
2015年 | 4058篇 |
2014年 | 4927篇 |
2013年 | 5847篇 |
2012年 | 6706篇 |
2011年 | 7083篇 |
2010年 | 6103篇 |
2009年 | 5783篇 |
2008年 | 5643篇 |
2007年 | 5248篇 |
2006年 | 4761篇 |
2005年 | 3935篇 |
2004年 | 2735篇 |
2003年 | 1899篇 |
2002年 | 1768篇 |
2001年 | 1428篇 |
2000年 | 1291篇 |
1999年 | 999篇 |
1998年 | 712篇 |
1997年 | 566篇 |
1996年 | 584篇 |
1995年 | 410篇 |
1994年 | 341篇 |
1993年 | 246篇 |
1992年 | 214篇 |
1991年 | 122篇 |
1990年 | 106篇 |
1989年 | 85篇 |
1988年 | 76篇 |
1987年 | 47篇 |
1986年 | 35篇 |
1985年 | 31篇 |
1984年 | 15篇 |
1983年 | 16篇 |
1982年 | 15篇 |
1981年 | 12篇 |
1980年 | 16篇 |
1979年 | 12篇 |
1976年 | 9篇 |
1975年 | 3篇 |
1959年 | 11篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 189 毫秒
41.
42.
Zehu Xie Na Peng Tingting Liu Xing Cheng Wuquan Ye Runtian Zheng Jundong Zhang Haoxiang Yu Jie Shu 《Ceramics International》2019,45(9):11812-11818
Here, LiY(WO4)2 nanotubes are prepared via a feasible electrospinning technique. This new anode material shows excellent electrochemical properties. The capacity loss of LiY(WO4)2 nanotubes is as low as 6.9% after 156 cycles, while bulk LiY(WO4)2 presents the capacity loss higher than 55.0%. Even after 600 long-life cycles, the capacity loss of the nanotubes is only 9%. It can be seen that the hollow structure with a rough surface and a porous morphology contributes to the improvement of electrochemical performance. Furthermore, online X-ray diffraction (XRD) method is firstly applied to understand the lithium ions insertion/extraction mechanism of LiY(WO4)2 nanotubes. It can be concluded that it is an asymmetrical two-phase reaction. A phase transformation from LiY(WO4)2 to Li3Y(WO4)2 can be obviously seen from the in situ XRD during discharge process. While Li2Y(WO4)2 appears as an intermediate phase with a reverse charge reaction. In addition, in situ XRD also demonstrates that LiY(WO4)2 nanotubes have surprised electrochemical reversibility. All the above results indicate that LiY(WO4)2 nanotubes can be expected to be anode candidate for rechargeable lithium ion batteries (LIBs). 相似文献
43.
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
44.
45.
段潇乐 《湖南工业职业技术学院学报》2015,(1):82-84
本研究检测了直接和间接两种修正性反馈与国内高职理科学生写作水平的关系。本实验持续五周,将150名学习者分为直接反馈组、间接反馈组及控制组,共安排了一次预先测试,,一次即时后测和一次延时后测,并分别对各组进行考察,结果显示两个实验组进步显著,且直接反馈效果最明显。 相似文献
46.
47.
通过分析攀长钢能源管理存在的不足和困难,从强化员工节能意识、合理组织生产、优化生产工艺、充分使用循环水、完善计量器具、加强余热利用及优化能源管理机制等方面入手提出节能改进措施,具有一定的现实意义。 相似文献
48.
Donghai Xu Peng Feng Yang Wang Wanpeng Yang Yu Wang Shaoyan Sun 《American Institute of Chemical Engineers》2022,68(2):e17472
Corrosion and salt deposition problems severely restrict the industrialization of supercritical water oxidation. Transpiring wall reactor can effectively weaken these two problems by a protective water film. In this work, methanol was selected as organic matter, and the influences of vital structural parameters on water film properties and organic matter removal were studied via numerical simulation. The results indicate that higher than 99% of methanol conversion could be obtained and hardly affected by transpiration water layer, transpiring wall porosity and inner diameter. Increasing layer and porosity reduced reactor center temperature, but inner diameter's influence was lower relatively. Water film temperature reduced but coverage rate raised as layer, porosity, and inner diameter increased. Notably, the whole reactor was in supercritical state and coverage rate was only approximately 85% in the case of one layer. Increasing reactor length affected slightly the volume of the upper supercritical zone but enlarged the subcritical zone. 相似文献
49.
The capture of particles by charged droplets was simulated by considering the electrostatic interactions of droplet-droplet and droplet-particle. The results indicate that the electrostatic repulsion between droplets leads to a dynamic accumulation mode of particles. However, the droplet spacing has an insignificant effect on the capture efficiency when the electrostatic deposition predominates. The increase of droplet charge remarkably improves the capture efficiency, in which the capture of fine particles accounts for the largest proportion. Compared to the droplet charge, the droplet size shows a limited improvement in the capture efficiency. Reducing the droplet velocity prolongs the capture time instead of enhancing the capture capacity per unit time, thereby improving capture efficiency. 相似文献
50.
Crystallographic characteristics and microwave dielectric properties of Ni-modified MgTa2O6 ceramics
Liang Shi Xueying Wang Rui Peng Gang Wang Cheng Liu Xiaolei Shi Dainan Zhang Huaiwu Zhang 《Ceramics International》2021,47(16):22514-22521
Ni2+ modified MgTa2O6 ceramics with a trirutile phase and space group P42/mnm were obtained. The correlations between crystallographic characteristics and microwave dielectric performance of MgTa2O6 ceramics were systematically studied based on the chemistry bond theory (PVL theory) for the first time. The results indicate that the introduction of Ni2+ causes a change in polarizability and the Mg–O bond ionicity, which contributes to the variation of dielectric constant. Moreover, the lattice energy, and packing fraction, full width at half maximum of the Raman peak of Ta–O bond, as the quantitative characterization of crystallographic parameters, regulate the dielectric loss of MgTa2O6 ceramics in GHz frequency band. In addition, the study of sintering behavior shows that the densification and micromorphology are the crucial factors affecting the microwave dielectric performance. Typically, Ni2+ doping on the A-site of MgTa2O6 can effectively promote the Q × f values to 173,000 GHz (at 7.43 GHz), which ensures its applicability in 5G communication technology. 相似文献