全文获取类型
收费全文 | 1834篇 |
免费 | 167篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 29篇 |
技术理论 | 1篇 |
综合类 | 5篇 |
化学工业 | 405篇 |
金属工艺 | 24篇 |
机械仪表 | 32篇 |
建筑科学 | 44篇 |
能源动力 | 54篇 |
轻工业 | 90篇 |
水利工程 | 6篇 |
石油天然气 | 1篇 |
无线电 | 402篇 |
一般工业技术 | 481篇 |
冶金工业 | 133篇 |
原子能技术 | 9篇 |
自动化技术 | 293篇 |
出版年
2023年 | 7篇 |
2022年 | 20篇 |
2021年 | 37篇 |
2020年 | 22篇 |
2019年 | 39篇 |
2018年 | 41篇 |
2017年 | 38篇 |
2016年 | 69篇 |
2015年 | 73篇 |
2014年 | 76篇 |
2013年 | 195篇 |
2012年 | 101篇 |
2011年 | 99篇 |
2010年 | 99篇 |
2009年 | 100篇 |
2008年 | 90篇 |
2007年 | 103篇 |
2006年 | 81篇 |
2005年 | 77篇 |
2004年 | 59篇 |
2003年 | 51篇 |
2002年 | 39篇 |
2001年 | 37篇 |
2000年 | 33篇 |
1999年 | 25篇 |
1998年 | 57篇 |
1997年 | 39篇 |
1996年 | 41篇 |
1995年 | 37篇 |
1994年 | 29篇 |
1993年 | 24篇 |
1992年 | 16篇 |
1991年 | 18篇 |
1990年 | 10篇 |
1989年 | 18篇 |
1988年 | 7篇 |
1987年 | 11篇 |
1986年 | 13篇 |
1985年 | 16篇 |
1984年 | 13篇 |
1983年 | 5篇 |
1981年 | 6篇 |
1980年 | 7篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 6篇 |
1976年 | 2篇 |
1975年 | 5篇 |
1974年 | 2篇 |
1973年 | 5篇 |
排序方式: 共有2009条查询结果,搜索用时 15 毫秒
71.
Jyh‐Chien Chen Kuppachari Rajendran Ya‐Hui Chang Sheng‐Wen Huang Yaw‐Tern Chern 《应用聚合物科学杂志》2011,120(6):3159-3170
Polypyrrole (PPy) and Polypyrrole‐ZnO (PPy‐ZnO) nanocomposites were electrodeposited on mild steel and its corrosion protection ability was studied by Tafel and Impedance techniques in 3.5% NaCl solution. Pure Polypyrrole film was not found to protect the mild steel perfectly but the coating with nano‐sized ZnO (PPy‐ZnO) has dramatically increased the corrosion resistance of mild steel. Electrochemical Impedance Spectroscopy (EIS) measurements indicated that the coating resistance (Rcoat) and corrosion resistance (Rcorr) values for the PPy‐ZnO nanocomposite coating was much higher than that of pure PPy coated electrode. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
72.
Tom P. Wyatt An‐Ting Chien Satish Kumar Donggang Yao 《Polymer Engineering and Science》2014,54(12):2839-2847
This article describes a new gel‐spinning process for making high‐strength poly(ethylene oxide) (PEO) fibers. The PEO gel‐spinning process was enabled through an oligomer/polymer blend in place of conventional organic solvents, and the gelation and solvent‐like properties were investigated. A 92/8 wt% poly(ethylene glycol)/PEO gel exhibited a melting temperature around 45°C and was highly stretchable at room temperature. Some salient features of a gel‐spun PEO fiber with a draw ratio of 60 are tensile strength at break = 0.66 ± 0.04 GPa, Young's modulus = 4.3 ± 0.1 GPa, and a toughness corresponding to 117 MJ/m3. These numbers are significantly higher than those previously reported. Wide‐angle x‐ray diffraction of the high‐strength fibers showed good molecular orientation along the fiber direction. The results also demonstrate the potential of further improvement of mechanical properties. POLYM. ENG. SCI., 54:2839–2847, 2014. © 2014 Society of Plastics Engineers 相似文献
73.
Illuminant chromaticity estimation is required in the fields of the tracking and recognition of human faces, compensation and detection of skin color, image reproduction, and color constancy. This article proposes a simple and effective method to estimate the illuminant chromaticity using highlights from the face region. We first select the candidate points through the detection of highlights around the leftmost pixel of the rg chromaticity space from the facial images under various illuminant conditions and then estimate the illuminant chromaticity by averaging the chromaticities of the candidate points. To enhance the illuminant chromaticity estimation accuracy, we propose a more elaborate estimation method, which effectively readjusts the candidate points of the highlight regions according to the conditions derived from two ethnic and three illuminant groups. The experiment results show that our proposed method reliably estimates the illuminant chromaticity under various color temperatures and illuminant directions. © 2012 Wiley Periodicals, Inc. Col Res Appl, 39, 188–199, 2014 相似文献
74.
Chun-Yen Lai Tzu-Chiao Chien Ting-Yi Lin Teng Ke Shih-Han Hsu Yun-Ju Lee Chien-ying Su Jeng-Tzong Sheu Ping-Hung Yeh 《Nanoscale research letters》2014,9(1):281
In this work, we have demonstrated that amorphous ZnO nanobranches (a-ZnO NBs) could spontaneously react from the crystalline ZnO NWs (c-ZnO NWs) at specific humid environment. The spontaneous reaction mechanism and result can be analyzed by humidity controlling and optical microscope (OM)/scanning electron microscope (SEM)/Kelvin probe force microscopy (KPFM)/transmission electron microscopy (TEM) system. We can make the c-ZnO NWs spontaneous reaction happen at different humid environments and suppress the a-ZnO NBs spontaneous reaction by oxygen/hydrogen plasma surface passivation. The hydrogen plasma surface treatment also can improve the UV sensing sensitivity more than twofold. This work provides the mechanism and methods of the a-ZnO NBs spontaneous growth and offers the passivation treatment for strengthening and enhancing ZnO-based nanodevice application in humid environment and UV light detection, respectively. 相似文献
75.
Microstructure and characterization of electrospun poly(vinyl alcohol) nanofiber scaffolds filled with graphene nanosheets 下载免费PDF全文
Graphene nanosheets (GNSs) have attracted significant scientific attention because of their remarkable features, including exceptional electron transport, excellent mechanical properties, high surface area, and antibacterial functions. Poly(vinyl alcohol) (PVA) solutions filled with GNSs were prepared for electrospinning, and their spinnability was correlated with their solution properties. The effects of GNS addition on solution rheology and conductivity were investigated. The as‐spun fibers were characterized via scanning electron microscopy (SEM), transmission electron microscopy (TEM), wide‐angle X‐ray diffraction (WAXD), and differential scanning calorimetry (DSC). The results revealed the effects of GNS on the microstructure, morphology, and crystallization properties of PVA/GNS composite nanofibers. The addition of GNSs in PVA solution increased the viscosity and conductivity of the solution. The electrospun fiber diameter of the PVA/GNS composite nanofiber was smaller than that of neat PVA nanofiber. GNSs were not only embedded at the fibers but also formed protrusions on the fibers. In addition, the crystallinity of PVA/GNS fiber decreased with higher GNS content. The possible application of PVA/GNS fibers in tissue engineering was also evaluated. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41891. 相似文献
76.
Wen‐Chin Tseng Yao‐Chi Shu Jen‐Chieh Lu Han‐Shian Shie Chien‐Chung Chen 《大分子材料与工程》2012,297(2):115-122
Large pieces of paper‐thin PLLA membranes are prepared and characterized as single‐layered hollow fibrous assemblies with an extremely high degree of fiber alignment. The diameter of the electrospun hollow fibers is in the range of some tens of micrometers with a wall thickness of a few micrometers. They are best described as 2D arrays of highly aligned microtubes. The mechanical properties of the membranes are studied. A processing map is constructed using the applied electric field strength and the concentration (viscosity) of the electrospinning dope. The influence of factors such as the field strength and weight and viscosity of the jetted solutions is discussed. The results will help in the future fabrication of highly anisotropic scaffolds for tissue engineering applications.
77.
78.
The thermal conductivity of graphene nanoribbons (GNRs) functionalized by the chemical attachment of methyl and phenyl groups at random positions is calculated using reverse nonequilibrium molecular dynamics. The GNRs exhibit a rapid drop in thermal conductivity with increasing degree of functionalization; a functional group coverage regime of as little as 1.25% of GNR atoms reduces the thermal conductivity by about 50%. The thermal conductivity of nanoribbons with zigzag edges is more sensitive in the degree of functionalization than nanoribbons with armchair edges. The simulation results indicate that the rapid drop in thermal conductivity is a consequence of the higher angular momentum of functional groups, which rotate the unsupported sp3 bonds and thus reduce the phonon mean free paths. 相似文献
79.
Thien Vuong Nguyen Phi Hung Dao Tuan Anh Nguyen Viet Hung Dang Minh Nguyet Ha Thi Thuy Trang Nguyen Quoc Trung Vu Ngọc Linh Nguyen Tran Chien Dang Phuong Nguyen-Tri Dai Lam Tran Le Trong Lu 《应用聚合物科学杂志》2020,137(37):49116
This work aims to clarify the photocatalytic degradation mechanism and heat reflectance recovery performance of waterborne acrylic polymer/ZnO nanocomposite coating. To fabricate the nanocomposite coating, ZnO nanoparticles (nano-ZnO) were dispersed into acrylic polymer matrix at the various concentrations from 1 to 6% (by total weight of resin solids). The photocatalytic degradation of nanocomposite coating under ultraviolet (UV) light irradiation has been investigated by monitoring its weight loss and chemical/microstructural/morphological changes. As the topcoat layer, its heat reflectance recovery has been evaluated under UV/condensation exposure by using an artificial dirty mixture of 85 wt% nanoclay, 10 wt% silica particles (1–5 μm), 1 wt% carbon black, and 2 wt% engine oil. After 108-cycle UV/condensation exposure, infrared spectra and weight loss analysis indicated that the maximal degradation for nanocomposite coating is observed at 1 wt% nano-ZnO. On the other hand, after 96 hr of UV light exposure, the nanocomposite coating with1 wt% nano-ZnO could restore effectively the reflective index of solar-heat reflectance coating (from 58.45 to 80.78%). Finally, the photodegradation mechanism of this waterborne acrylic polymer coating has been proposed as the UV-induced formation of CC CO conjugated double bonds. As a result, its self-cleaning phenomenon can be achieved as the recovery of heat reflectance. 相似文献
80.
The hydrodynamic characteristics and mass transfers of halide quaternary salts between two immiscible phases in a stirred membrane permeation cell were investigated. The concentration of quaternary salt, temperature, solvent and the four kinds of halide quaternary salts were evaluated to achieve the extractive optimum condition. The diffusivity, overall mass‐transfer coefficients and individual mass‐transfer coefficients were determined and correlated in terms of the conventional Sh‐Re‐Sc relationship. The transfer time of quaternary salts across the membrane and the thickness of the hydrodynamic diffusion boundary layer were determined as well, so as to characterize the extractive phenomenon of quaternary salts between the two phases that is useful in phase‐transfer catalysis. 相似文献