全文获取类型
收费全文 | 8827篇 |
免费 | 471篇 |
国内免费 | 24篇 |
专业分类
电工技术 | 123篇 |
综合类 | 15篇 |
化学工业 | 1704篇 |
金属工艺 | 279篇 |
机械仪表 | 397篇 |
建筑科学 | 178篇 |
矿业工程 | 2篇 |
能源动力 | 362篇 |
轻工业 | 626篇 |
水利工程 | 35篇 |
石油天然气 | 15篇 |
无线电 | 1820篇 |
一般工业技术 | 1736篇 |
冶金工业 | 764篇 |
原子能技术 | 95篇 |
自动化技术 | 1171篇 |
出版年
2023年 | 76篇 |
2022年 | 114篇 |
2021年 | 212篇 |
2020年 | 123篇 |
2019年 | 165篇 |
2018年 | 226篇 |
2017年 | 199篇 |
2016年 | 252篇 |
2015年 | 207篇 |
2014年 | 335篇 |
2013年 | 656篇 |
2012年 | 524篇 |
2011年 | 639篇 |
2010年 | 448篇 |
2009年 | 530篇 |
2008年 | 482篇 |
2007年 | 414篇 |
2006年 | 329篇 |
2005年 | 322篇 |
2004年 | 247篇 |
2003年 | 251篇 |
2002年 | 233篇 |
2001年 | 182篇 |
2000年 | 174篇 |
1999年 | 163篇 |
1998年 | 352篇 |
1997年 | 220篇 |
1996年 | 176篇 |
1995年 | 156篇 |
1994年 | 117篇 |
1993年 | 119篇 |
1992年 | 91篇 |
1991年 | 84篇 |
1990年 | 58篇 |
1989年 | 50篇 |
1988年 | 44篇 |
1987年 | 39篇 |
1986年 | 29篇 |
1985年 | 32篇 |
1984年 | 38篇 |
1983年 | 24篇 |
1982年 | 30篇 |
1981年 | 23篇 |
1980年 | 23篇 |
1979年 | 10篇 |
1977年 | 15篇 |
1976年 | 21篇 |
1975年 | 14篇 |
1974年 | 7篇 |
1973年 | 10篇 |
排序方式: 共有9322条查询结果,搜索用时 31 毫秒
91.
Using chloroform/dimethylformamide (CF/DMF) co-solvent, electrospinning of poly[(R)-3-hydroxybutyrate] (PHB) solutions was carried out at ambient temperature. The effects of the applied voltage (V), flow-rate (Q), and solution viscoelastic properties on the Taylor cone, electrified jet, and fiber morphology were investigated. In addition, the electric field developed by the needle-plate electrode configuration was calculated using a finite element analysis to reveal the tip-to-collector (H) effect. Among the processing parameters (V, Q and H), it was found that Q played a key role in determining the jet diameter (dj) and electrospun fiber diameter (df), and scaling laws existed between them, i.e., dj-Q0.61 and df-Q0.33. The diameter reduction ratios of Do/dj (Do is the needle diameter) and dj/df were measured as 50-120 and 5-10, respectively; it suggested that major jet stretching took place in the straight electrified jet region, and further chain orientation could be gained by the subsequent process of jet whipping. By changing PHB concentrations from 5 to 15 wt%, the solution viscosity (ηo) was increased from 100 to 4900 cP, whereas the surface tension and solution conductivity remained unchanged; it provided a good model solution to exclusively reveal the ηo effect on the electrospinning process. Our results showed that the ηo-dependence of dj and df also followed simple scaling laws: dj-ηo0.06, and df-ηo0.39, with a prefactor depending on the processing variables, mainly the flow-rate. Regardless of the PHB concentrations used, the obtained PHB fibers showed a similar crystallinity fraction of ca. 0.63 and possession of major α-crystals together with a small amount of β-crystals with zigzag chain conformation. 相似文献
92.
Han‐Lang Wu Chen‐Chi M. Ma Chun‐Chieh Lin Yie‐Chan Chiu Chih‐Yuan Chen Chin‐Lung Chiang 《应用聚合物科学杂志》2008,107(5):3236-3243
Poly(arylene ether benzonitrile) (PAEBN) was synthesized with 2,6‐dichlorobenzonitrile and biphenol. PAEBNs with various molecular weights (MWs), 1,640,000 and 185,000 g/mol, were synthesized by control of the stoichiometry of the monomers and were blended with sulfonated poly(ether ether ketone) (SPEEK). The effects of MW on the water uptake, swelling, methanol permeability, and proton conductivity of the SPEEK/PAEBN blend membranes were investigated. The molecular mobility of the SPEEK/PAEBN blends was also examined in this study. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
93.
Distributed active storage architectures are designed to offload user-level processing to the peripheral from the host servers.
In this paper, we report preliminary investigation on performance and fault recovery designs, as impacted by emerging storage
interconnect protocols and state-of-the-art storage devices. Empirical results obtained using validated device-level and interconnect
data demonstrate the significance of the said parameters on the overall system performance and reliability. 相似文献
94.
S.K. Lee D.‐H. Hwang B.‐J. Jung N.S. Cho J. Lee J.‐D. Lee H.‐K. Shim 《Advanced functional materials》2005,15(10):1647-1655
By using Ni0‐mediated polymerization, we have systematically synthesized a series of fluorene‐based copolymers composed of blue‐, green‐, and red‐light‐emitting comonomers with a view to producing polymers with white‐light emission. 2,7‐Dibromo‐9,9‐dihexylfluorene, {4‐(2‐[2,5‐dibromo‐4‐{2‐(4‐diphenylamino‐phenyl)‐vinyl}‐phenyl]‐vinyl)‐phenyl}‐diphenylamine (DTPA), and 2‐{2‐(2‐[4‐{bis(4‐bromo‐phenyl)amino}‐phenyl]‐vinyl)‐6‐tert‐butyl‐pyran‐4‐ylidene}‐malononitrile (TPDCM) were used as the blue‐, green‐, and red‐light‐emitting comonomers, respectively. It was found that the emission spectra of the resulting copolymers could easily be tuned by varying their DTPA and TPDCM content. Thus with the appropriate red/green/blue (RGB) unit ratio, we were able to obtain white‐light emission from these copolymers. A white‐light‐emitting diode using the polyfluorene copolymer containing 3 % green‐emitting DTPA and 2 % red‐emitting TPDCM (PG3R2) with a structure of indium tin oxide/poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonic acid)/PG3R2/Ca/Al was found to exhibit a maximum brightness of 820 cd m–2 at 11 V with Commission Internationale de L'Eclairage (CIE) coordinates of (0.33,0.35), which are close to the standard CIE coordinates for white‐light emission (0.33,0.33). 相似文献
95.
Bang-Ning Hwang Shih-Chi Chang Hsiao-Cheng Yu Che-Wei Chang 《The International Journal of Advanced Manufacturing Technology》2008,36(7-8):825-832
Taiwan Semiconductor Manufacturing Company (TSMC) is the largest semiconductor foundry in the world. Advanced Semiconductor Engineering Inc. (ASE) is the world’s leader in semiconductor assembly and testing. From 1998 to 2004, the two companies completed electronic integration of 11 key business processes through the Internet. The result is a seamless interface between TSMC, ASE and their joint customers. They can now obtain accurate, timely information on their product status and respond appropriately when needed. While the direct economic benefits are estimated to be around US$ 10 million through productivity increase over a total investment of about US$ 2 million, the indirect benefits of this initiative could be on the order of US $100 million if the joint customers’ benefits are considered. In collaboration with the RosettaNet organization, TSMC and ASE leveraged their pioneering experiences to define three data exchange standards which can then be widely adopted in the semiconductor industry. This case study is a demonstration of how two leading companies in their respective fields can join forces to make a difference in creating value for the entire semiconductor industry, which in turn benefits society at large. With the momentum continuing to build and the sphere of influence continuing to expand, it is anticipated that TSMC, ASE and the entire sector will upgrade their competitiveness in terms of cost, quality, responsiveness and customer orientation. 相似文献
96.
R. M. Hwang K. C. Cha 《The International Journal of Advanced Manufacturing Technology》2008,37(11-12):1093-1104
Learning and prediction capability of the backpropagation neural network (BPNN) have been used to build the prediction model for the structural stability of a surface grinder. The Lagrange energy method is applied to derive the dynamic equation of the lumped parameter model of the surface grinder. The major factors influencing the structural stability of the system can be determined after the ratio of kinetic energy of the sub-structure and the ratio of potential energy of the sub-structure interface are obtained. An orthogonal rotatable central composite design is adopted to dispose the treatment combinations of the major factors. The BPNN model is constructed by the treatment combinations of the training patterns and verified by the treatment combinations of the test patterns. In this paper, a 3-layer BPNN model with a 10-neuron hidden layer which converged after 4,072 learning cycles is selected to predict the structural stability of a surface grinder within the planned ranges. The percentage residuals of both training patterns and test patterns are all within 3.41%, thus the prediction accuracy of the BPNN model is excellent so that the engineering demands are well satisfied. 相似文献
97.
Hong Kong is known as a migrant city because its population was sourced from mainland China, and because there has always been outflows of people to overseas countries, especially from the mid-1980s to mid-1990s. Emigration to mainland China has become a significant recent trend. This article discusses this phenomenon in the theoretical contexts of migration and trans-border residential development. It contends that the trend will intensify more quickly than other cross-border movements because the two systems are separated by a political border within one country, and because there are common cultural ties and rapid economic integration. 相似文献
98.
PE McAndrew A Frostholm JE Evans D Zdilar D Goldowitz IM Chiu AH Burghes A Rotter 《Canadian Metallurgical Quarterly》1998,391(4):444-455
99.
Luk Chiu Li Jagdish Parasrampuria Ron Levans Kurt G. Van Scoik 《Drug development and industrial pharmacy》1994,20(13):2079-2090
The moisture-uptake kinetics of a hygroscopic powder, sodium heparin contained in a cylindrical container, was determined using a novel moisture-uptake measuring device under a constant convective air flow. The amount of moisture uptake increased with the increase in the relative humidity of the air. The effect of powder-bed height on the total amount of moisture uptake was found to be significant only at the highest relative humidity (75%) evaluated in this study. However, the percent of weight increase of the powder as a result of moisture uptake decreases as the height of the powder bed increases. The results of this study are explained by the dynamic nature of the moisture-uptake process associated with the instrument. 相似文献
100.
A new multifunction filter using minimum components is presented. This filter which possesses single input and four outputs can simultaneously generate second-order highpass, bandpass, and lowpass filtering functions at individual output terminals. The filter has the following merits; it uses only two grounded capacitors which makes it suitable for integrated circuit implementation, no matching condition is required, offering multifunction outputs and has low passive and active sensitivities. Experimental results agree very well with the theoretical result 相似文献