全文获取类型
收费全文 | 54888篇 |
免费 | 5290篇 |
国内免费 | 2355篇 |
专业分类
电工技术 | 2524篇 |
技术理论 | 2篇 |
综合类 | 2899篇 |
化学工业 | 11946篇 |
金属工艺 | 7290篇 |
机械仪表 | 2926篇 |
建筑科学 | 2310篇 |
矿业工程 | 1459篇 |
能源动力 | 8525篇 |
轻工业 | 3425篇 |
水利工程 | 476篇 |
石油天然气 | 1484篇 |
武器工业 | 448篇 |
无线电 | 4180篇 |
一般工业技术 | 6668篇 |
冶金工业 | 3072篇 |
原子能技术 | 496篇 |
自动化技术 | 2403篇 |
出版年
2024年 | 209篇 |
2023年 | 998篇 |
2022年 | 2179篇 |
2021年 | 2887篇 |
2020年 | 2204篇 |
2019年 | 1848篇 |
2018年 | 1602篇 |
2017年 | 2087篇 |
2016年 | 1960篇 |
2015年 | 1957篇 |
2014年 | 3161篇 |
2013年 | 3286篇 |
2012年 | 3802篇 |
2011年 | 4671篇 |
2010年 | 3388篇 |
2009年 | 3224篇 |
2008年 | 2943篇 |
2007年 | 3235篇 |
2006年 | 2964篇 |
2005年 | 2389篇 |
2004年 | 1976篇 |
2003年 | 1735篇 |
2002年 | 1567篇 |
2001年 | 1261篇 |
2000年 | 984篇 |
1999年 | 764篇 |
1998年 | 619篇 |
1997年 | 495篇 |
1996年 | 410篇 |
1995年 | 316篇 |
1994年 | 303篇 |
1993年 | 220篇 |
1992年 | 191篇 |
1991年 | 137篇 |
1990年 | 104篇 |
1989年 | 111篇 |
1988年 | 65篇 |
1987年 | 34篇 |
1986年 | 34篇 |
1985年 | 40篇 |
1984年 | 33篇 |
1983年 | 20篇 |
1982年 | 27篇 |
1981年 | 20篇 |
1980年 | 20篇 |
1979年 | 11篇 |
1976年 | 7篇 |
1975年 | 8篇 |
1974年 | 4篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
92.
The smoke suppression of rigid polyurethane foam (RPUF) modified by melamine was investigated based on three sections: the condensed phase, the carbon layer, and the gas phase. In the condensed phase, the results of thermogravimetry, X‐ray photoelectron spectroscopy (XPS) N1S spectrum, and Fourier transform infrared spectroscopy indicated that melamine could suppress the degradation of RPUF by reacting with the aromatic hydrocarbons. It also reduced the smoke generation because the volatilizable aromatic hydrocarbons were the principal smoke precursors in a fire. In the carbon layer, the decrease from 38.50% to 24.76% of the inner layer oxygen content identified by XPS full‐spectrum and C1S spectrum indicated that melamine could prevent oxygen from transferring into the inner foam by the formation of an enhanced surface carbon layer, and the enhanced carbon layer could also block the release of smoke precursors. In the gas phase, the content of total aromatic hydrocarbons declined to 59.12% according to pyrolysis gaseous chromatography mass spectroscopy and indicated that melamine could reduce the smoke precursors. The results of smoke density chamber and cone calorimeter tests revealed that the addition of the melamine could decrease the smoke density of burning RPUF. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
93.
Joshua C. Price Simon J. Levett Valentin Radu David A. Simpson Aina Mogas Barcons Christopher F. Adams Melissa L. Mather 《Small (Weinheim an der Bergstrasse, Germany)》2019,15(22)
Fluorescent nanodiamonds (fNDs) containing nitrogen vacancy (NV) centers are promising candidates for quantum sensing in biological environments. This work describes the fabrication and implementation of electrospun poly lactic‐co‐glycolic acid (PLGA) nanofibers embedded with fNDs for optical quantum sensing in an environment, which recapitulates the nanoscale architecture and topography of the cell niche. A protocol that produces uniformly dispersed fNDs within electrospun nanofibers is demonstrated and the resulting fibers are characterized using fluorescent microscopy and scanning electron microscopy (SEM). Optically detected magnetic resonance (ODMR) and longitudinal spin relaxometry results for fNDs and embedded fNDs are compared. A new approach for fast detection of time varying magnetic fields external to the fND embedded nanofibers is demonstrated. ODMR spectra are successfully acquired from a culture of live differentiated neural stem cells functioning as a connected neural network grown on fND embedded nanofibers. This work advances the current state of the art in quantum sensing by providing a versatile sensing platform that can be tailored to produce physiological‐like cell niches to replicate biologically relevant growth environments and fast measurement protocols for the detection of co‐ordinated endogenous signals from clinically relevant populations of electrically active neuronal circuits. 相似文献
94.
Andrea Bedon Jean Paul Viricelle Mathilde Rieu Simone Mascotto Antonella Glisenti 《International Journal of Hydrogen Energy》2021,46(27):14735-14747
In this contribution brownmillerite-based nanocomposite cathode for Single-Chamber Solid Oxide Fuel Cells is developed. These cells can be very attractive especially for small and cheap devices because of the absence of seals. The efficiency of SC-SOFCs is strictly connected to the selectivity of anode and cathode, the bottleneck for this technology. The development of a cathode inert in fuel oxidation is particularly challenging. Our strategy is to start from a catalytically un-active support (CFA = Ca2FeAl0.95Mg0.05O5) and induce the formation of iron oxide based nanoparticles, expected to activate oxygen. Symmetric (CFA + FeOx/CGO/CFA + FeOx) and complete cells (CFA + FeOx/CGO/Ni-CGO) are studied in air and methane/oxygen 2:1 mixture. The Area Specific Resistance of CFA + FeOx is less than 1/3 that of CFA. The high selectivity allows to reach an efficiency of 25%; power still needs to be increased but we demonstrated the possibility to develop selective low cost electrodes. The effect of air, methane/oxygen exposure and the heat treatments were carefully investigated. 相似文献
95.
96.
CO2激光治疗皮肤基底细胞癌14例临床观察 总被引:4,自引:0,他引:4
目的 :探求一种简单 ,安全 ,效果好的基底细胞癌的治疗方法。方法 :对 1 4例基底细胞癌患者在局麻下用CO2 激光行基底细胞癌切除术或切除 +气化术。结果 :患者术中、术后出血少 ,伤口恢复快 ,愈合良好 ,疤痕表浅 ,随访未见复发。结论 :CO2 激光用于治疗基底细胞癌效果良好 ,无明显副作用 ,操作简单值得推广。 相似文献
97.
用矾土作为主原料,选择适当结合剂和添加剂,引入微粉技术,采用真空炼泥等工艺手段,研制成低水分抗热震高铝可塑料。该制品用作热媒加热炉衬里,显示出良好的耐高温和耐热冲击性能。 相似文献
98.
99.
100.