全文获取类型
| 收费全文 | 3042篇 |
| 免费 | 50篇 |
| 国内免费 | 12篇 |
专业分类
| 电工技术 | 36篇 |
| 综合类 | 6篇 |
| 化学工业 | 298篇 |
| 金属工艺 | 49篇 |
| 机械仪表 | 40篇 |
| 建筑科学 | 53篇 |
| 矿业工程 | 5篇 |
| 能源动力 | 86篇 |
| 轻工业 | 126篇 |
| 水利工程 | 42篇 |
| 石油天然气 | 22篇 |
| 无线电 | 77篇 |
| 一般工业技术 | 217篇 |
| 冶金工业 | 1914篇 |
| 原子能技术 | 18篇 |
| 自动化技术 | 115篇 |
出版年
| 2024年 | 30篇 |
| 2023年 | 19篇 |
| 2022年 | 25篇 |
| 2021年 | 82篇 |
| 2020年 | 65篇 |
| 2019年 | 59篇 |
| 2018年 | 75篇 |
| 2017年 | 70篇 |
| 2016年 | 79篇 |
| 2015年 | 59篇 |
| 2014年 | 66篇 |
| 2013年 | 117篇 |
| 2012年 | 71篇 |
| 2011年 | 90篇 |
| 2010年 | 78篇 |
| 2009年 | 52篇 |
| 2008年 | 40篇 |
| 2007年 | 28篇 |
| 2006年 | 15篇 |
| 2005年 | 14篇 |
| 2004年 | 6篇 |
| 2003年 | 12篇 |
| 2002年 | 6篇 |
| 2001年 | 4篇 |
| 2000年 | 3篇 |
| 1999年 | 57篇 |
| 1998年 | 668篇 |
| 1997年 | 301篇 |
| 1996年 | 223篇 |
| 1995年 | 115篇 |
| 1994年 | 100篇 |
| 1993年 | 120篇 |
| 1992年 | 11篇 |
| 1991年 | 22篇 |
| 1990年 | 28篇 |
| 1989年 | 32篇 |
| 1988年 | 34篇 |
| 1987年 | 27篇 |
| 1986年 | 17篇 |
| 1985年 | 16篇 |
| 1984年 | 2篇 |
| 1983年 | 4篇 |
| 1982年 | 5篇 |
| 1981年 | 12篇 |
| 1980年 | 13篇 |
| 1978年 | 1篇 |
| 1977年 | 24篇 |
| 1976年 | 105篇 |
| 1956年 | 1篇 |
| 1955年 | 1篇 |
排序方式： 共有3104条查询结果，搜索用时 15 毫秒
991.
Yen‐Cheng Kung Nahid Hosseini Dumitru Dumcenco Georg E. Fantner Andras Kis 《Advanced Electronic Materials》2019,5(1)
Favorable mechanical and electrical properties motivate the use of 2D semiconductors in flexible electronic devices. One of the main challenges here is the absence of a practical doping strategy which should provide air‐stable, tunable doping levels in a process with a low thermal budget. Here, it is shown that SU8, an epoxy‐based photoresist, can be used for nondegenerate n‐type doping of monolayer MoS2. The doping level can be finely tuned via low‐temperature annealing. The doping method exhibits good ambient stability. The high degree of mechanical flexibility and low processing temperature also allows the integration of SU8 coating with flexible MoS2 FETs, where it can provide both controllable doping and act as an encapsulation layer. The demonstrated stability of the devices to bending and exposure to water confirms the attractiveness of using SU8 in flexible electronic devices based on 2D semiconductors in a simple, versatile and scalable approach. 相似文献
992.
993.
This paper proposes a model to allocate photovoltaic unit (PVU) and distribution static compensator (DSTATCOM) that incorporate the operation effect of PVU in sizing and sitting problem. The model is based on the dynamic assessment of PVU production and the effect of it on placement of PVU and DSTATCOM. Geographical conditions are interfered in placement problem of PVU and DSTATCOM simultaneously. The model is verified in a multi‐objective form. The multi‐objective problem is formulated based on voltage stability, liability, power loss and total cost of PVU and DSTATCOM. This problem is solved by employing optimization technique and the results of optimization processes are tested in different scenarios. Uncertainty in network loads is an inevitable task that should be considered in network planning. Uncertainty in the presented model has been defined as a set of divided parts in the presented model. The proposed model has been evaluated on two test system, 33‐bus and 69‐bus. The obtained results indicate that the presented model can be employed to study the intermittent behavior of PVU in placement problem. 相似文献
994.
Amirhossein Moghanian Mohammadamin Zohourfazeli Mahzad Haji Mahdi Tajer Zahra Miri SeyedMohammad Hosseini Ali Rashvand 《Ceramics International》2021,47(17):23762-23769
In the present study, structure of zirconium-containing bioactive glass (58S-BG (Zr-BG)) with optimal fixed Zr content (5 mol.%) was modified by incorporation of strontium (Sr). These Zr and Sr-containing BGs (ZS-BGs) were synthesized by sol-gel method and substitution of Ca with modifier ions (Sr content = 0, 3, 6, 9, and 12 mol.%). The results obtained from characterization by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-transform infrared (FTIR), and energy-dispersive X-ray spectroscopy (EDS) techniques from surface of all the ZS-BGs revealed formation of hydroxyapatite (HA) after 7 days of immersion in the simulated body fluid (SBF) solution. Evaluation of changes in the SBF solution, by monitoring pH variations and ions? concentration, was in agreement with the results of morphological and structural investigations. The in-vitro biological function of synthesized BGs was studied through (MTT) assay and alkaline phosphatase (ALP) activity analysis. The results showed that all the specimens significantly stimulated proliferation and viability of MC3T3 osteoblast-like cells. Furthermore, antibacterial studies confirmed less resistance of methicillin-resistant Staphylococcus aureus (MRSA) bacteria against ZS-BGs. Eventually, the results of in-vitro bio-analysis were clarified and confirmed by two cell staining techniques of Live/Dead and Dapi/Actin. This confirmation was achieved by observing the increased quantity of live cells and their nuclei as well as the decreased number of dead cells after co-culturing with all ZS-BGs. 相似文献
995.
Beam‐to‐column connections are of great significance as they noticeably influence the mechanical behavior of structures at ambient and elevated temperatures. Observations from full‐scale fire tests confirm that connections play an important role on the resistance time of structural components in fire. Because of the high cost of elevated temperature tests, adequate experimental data on a broad range of connections are not available. One type of such connections is the I‐beam‐to‐circular tubular leg connections in offshore oil/gas platform topsides. Considering the high risk of fire events in offshore oil/gas platforms, our study focuses on the structural behavior of this type of connection at elevated temperatures. Eleven small‐scale experimental tests were conducted on a uniplanar welded steel I‐beam‐to‐tubular chord connection with external diaphragms to investigate their fire resistance capacity. Local strengthening and partial thermal insulating were separately introduced to the connection components. The results show that the external diaphragms play a considerably more important role on the connection fire response as compared with that for the vertical stiffeners. It is also found that the degradations in the connections' stiffness at elevated temperature might be closely correlated with the classical thermomechanical data on steel material. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
996.
The objective of this article is to assess the mechanical performance of PLA‐based materials under exposure of an organic liquid. In evaluating new opportunities of PLA‐based material, it is important to understand not only the chemical resistance of the material but also the potential route for degradation, which affect the mechanical behavior of the product during its service time. Degradation of PLA material with amount of sorption should be carefully controlled in order to maintain its mechanical performance in response to various loading condition. Distribution of the absorbed liquid within the package is firstly evaluated by identifying the characteristics of the mass transport. Gravimetric analysis is employed to investigate the liquid sorption mechanism and the induced expansion over a particular period. The profile of absorbed liquid content is numerically obtained and verified with the analytic solution. The changes in mechanical performances were investigated by measuring the properties of specimens containing saturated liquid content. It is found that at low temperature, the kinetics of liquid sorption follows the Fick's law but at higher temperature, it showed a deviation from the Fickian curve. The experiment results also confirm progressive decrease of the modulus and strength by increasing of fluid content inside the material. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43250. 相似文献
997.
Mohammad Mirzaei Sayed Alireza Hassani Najafabadi Majid Abdouss Saman Azodi‐Deilami Ebadullah Asadi Mohammad Reza Milani Hosseini Majid Piramoon 《应用聚合物科学杂志》2013,128(3):1557-1562
A polyacrylate tetracycline (TC) selective microporous molecularly imprinted polymer was prepared in three different porogenic solvents (chloroform, acetonitrile, and methanol) via precipitation polymerization, using methacrylic acid monomer, ethylene glycol dimethacrylate crosslinker, and TC as template. In all three solvents this method produced microporous particles in the scale range (200–400 nm), simply, quickly, cleanly, and in good yield. The effect of polarity of porogenic solvents on binding capacity was investigated. The imprinted polymer prepared in chloroform gave much higher binding capacity (KD = 198.6) for TC than the polymers prepared in acetonitrile (KD = 133.2) or methanol (KD = 104.7). The selectivity of imprinted polymers was evaluated by rebinding other structurally similar compounds. The results clearly indicated that the imprinted acrylate polymer exhibits an excellent selectivity toward TC, and has better ability to control the release of TC than the non‐imprinted polymer.© 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013 相似文献
998.
Palladium nanoparticles (Pd‐NPs)/polyaniline (PAni)/titanium (Ti) catalysts were prepared using electroless deposition of Pd‐NPs on PAni matrixes coated on Ti substrate. PAni/Ti electrodes were synthesized by electro‐polymerization of aniline on Ti. The morphology of Pd‐NPs on PAni/Ti electrodes were characterized by scanning electron microscopy technique and results indicated that Pd‐NPs were uniformly dispersed on the surface of PAni film. The electro‐catalytic properties of Pd‐NPs/PAni/Ti catalysts toward oxidation of hydrazine were investigated by different electrochemical methods and results showed that Pd‐NPs/PAni/Ti catalysts have high electrochemical activity. In addition, the mechanism of hydrazine electrochemical oxidation catalyzed by Pd‐NPs/PAni/Ti was investigated. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
999.
A simple and nonconventional electrospinning technique was employed for producing aligned polyacrylonitrile (PAN) nanofibers. A thermal zone was placed between syringe needles and collector in the electrospinning set up to obtain aligned and heat treated nanofibers. Suitable temperatures for heat treat process of PAN nanofibers was determined using differential scanning spectroscopy (DSC) technique. The influence of treatment temperature was investigated on morphology, internal structure and mechanical properties of collected PAN nanofibers. The average fiber diameter measured from SEM images exhibited decreasing trend at higher temperatures. FTIR spectra indicated no considerable difference between chemical structure of untreated and treated PAN nanofibers. Crystallization degree of PAN nanofibers calculated from WAXD patterns showed relatively low change with treatment temperature. Tenacity values of nanofiber bundles increased with increasing temperature while the extension values had an inverse trend. However, the modulus did not show a regular manner, but treated nanofibers had more modulus than untreated ones. The stress and modulus of PAN nanofibers increased to 112.9 MPa and 7.25 GPa at 270°C, respectively. Nanofibers treated at the highest temperature had the largest amount of crystallinity and strength. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
1000.
In this research, the ability of multilayer perceptron neural networks to estimate vapour–liquid equilibrium data have been studied. Four typical binary refrigerant systems containing R227ea have been investigated in a large range of temperatures and pressures. The systems are categorised into four groups, based on their different deviations from the Raoult's law. The networks with one hidden layer consisted of five neurons are developed as the optimal structure. For these binary systems, uncertainties in the artificial neural networks (ANNs) estimations were not more than 1.03%. In addition, the abilities of ANNs are shown by comparisons with Margules, van Laar, and some other correlations. 相似文献