全文获取类型
收费全文 | 15731篇 |
免费 | 1254篇 |
国内免费 | 48篇 |
专业分类
电工技术 | 211篇 |
综合类 | 17篇 |
化学工业 | 3844篇 |
金属工艺 | 597篇 |
机械仪表 | 1017篇 |
建筑科学 | 269篇 |
矿业工程 | 2篇 |
能源动力 | 733篇 |
轻工业 | 1173篇 |
水利工程 | 43篇 |
石油天然气 | 17篇 |
武器工业 | 1篇 |
无线电 | 2966篇 |
一般工业技术 | 3463篇 |
冶金工业 | 898篇 |
原子能技术 | 237篇 |
自动化技术 | 1545篇 |
出版年
2024年 | 9篇 |
2023年 | 188篇 |
2022年 | 270篇 |
2021年 | 473篇 |
2020年 | 365篇 |
2019年 | 394篇 |
2018年 | 484篇 |
2017年 | 505篇 |
2016年 | 588篇 |
2015年 | 502篇 |
2014年 | 709篇 |
2013年 | 1027篇 |
2012年 | 1090篇 |
2011年 | 1293篇 |
2010年 | 930篇 |
2009年 | 962篇 |
2008年 | 900篇 |
2007年 | 681篇 |
2006年 | 630篇 |
2005年 | 546篇 |
2004年 | 506篇 |
2003年 | 483篇 |
2002年 | 456篇 |
2001年 | 364篇 |
2000年 | 356篇 |
1999年 | 344篇 |
1998年 | 453篇 |
1997年 | 279篇 |
1996年 | 222篇 |
1995年 | 148篇 |
1994年 | 148篇 |
1993年 | 111篇 |
1992年 | 90篇 |
1991年 | 77篇 |
1990年 | 70篇 |
1989年 | 68篇 |
1988年 | 42篇 |
1987年 | 48篇 |
1986年 | 32篇 |
1985年 | 22篇 |
1984年 | 26篇 |
1983年 | 26篇 |
1982年 | 13篇 |
1981年 | 21篇 |
1980年 | 12篇 |
1979年 | 7篇 |
1977年 | 18篇 |
1976年 | 21篇 |
1975年 | 6篇 |
1974年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
151.
Rheological and electrical properties of polycarbonate/multi-walled carbon nanotube composites 总被引:1,自引:0,他引:1
Rheological and electrical properties of the polycarbonate (PC)/multi-walled carbon nanotube (MWNT) were studied. The MWNT was funtoinalized by treating with the hydrogen peroxide (H2O2). The H2O2 treated MWNT was dried by thermal and freeze drying methods. From the morphological studies, the degree of entanglement of the MWNT was decreased after treating with the H2O2. For the H2O2 treated MWNT (thermal drying), the length of the MWNT was shortened compared that of the H2O2 treated MWNT (freeze drying). The rheological and electrical properties of the PC/MWNT (H2O2 treated) composites increased compared that of the PC/MWNT (untreated) composites. Also, the electrical conductivity showed higher value for the PC/MWNT (H2O2 treated, freeze drying) composites compared that of the PC/MWNT (H2O2 treated, thermal drying) composites. From the results of the morphological, rheological, and electrical properties of the PC/MWNT composites, it is suggested that the electrical and rheological properties of the PC/MWNT composites are affected by the MWNT-MWNT network structure, which is related with the MWNT morphologies such as the degree of aggregation and aspect ratio of the MWNT. 相似文献
152.
Summary The cyclopolymerization of 1,8-diethynylnaphthalene(DEN) and its copolymerization with diethyl dipropargylmalonate(DEDPM) were carried out by various transition metal catalysts. MoCl5-based catalyst was found to be very effective and gave almost a quantitative polymer yield. The resulting dark-brown homopolymer(PDEN) was partially soluble in chloroform, tetrahydrofuran, and dimethyl sulfoxide, whereas copolymer (1:1) with number avaerage molecular weight
of 2.1x104 by GPC showed good solubility in those solvents. The structure of the polymers was analysed by IR, NMR, and UV-VIS spectroscopies. From the spectral and solubility data, it is proposed that cyclized products with the conjugated system are formed. Room temperature conductivities of the I2-doped homo and copolymer were found to be about 7.5x10-3 and 5.1x10-3 S/cm, respectively. 相似文献
153.
Poly(amide imide)–epoxysilane (coupling agent) composites were reacted with silica, a condensation product of tetraethylorthosilicate (TEOS), by a sol–gel process and were then cast into films. After this procedure, the chemical characteristics and mechanical and thermal properties were measured. Fourier transform infrared showed that silica existed in the poly(amide imide) matrix. When a proper amount of silica was added to the poly(amide imide) matrix, the tensile strength, elongation, and toughness increased greatly. A poly(amide imide)/30 wt % epoxysilane composite with 20 wt % TEOS had the best mechanical properties. Thermogravimetric analysis under nitrogen and oxygen atmospheres indicated that the char contents increased with the amount of silica. The glass‐transition temperatures of the poly(amide imide)–silica nanocomposites were observed around 170–180°C with differential scanning calorimetry. This approach may be a new method for the low‐temperature thermal curing of poly(amide imide). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1780–1788, 2004 相似文献
154.
Jun-Bin Ko Sung Wook Lee Dong Eun Kim Young Un Kim Gang Li Seung Goo Lee Tae-Sun Chang Dojin Kim Yong Lak Joo 《Journal of Porous Materials》2006,13(3):325-330
(1 − x)SiO2-(x)ZrO2 (x = 0.1, 0.2) composite fiber mats were prepared by electrospinning their sol-gel precursors of zirconium acetate and tetraethyl
orthosilicate (TEOS) without using a polymer binder. The electrospun composite fibers were characterized by powder X-ray diffraction
(XRD), scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FT-IR) and mercury porosimetry. The composite
fibers having a tetragonal crystalline ZrO2 were obtained by calcining the electrospun composite fibers at high temperatures. The results show that the structure and
crystallization of ZrO2 in the composite fibers can be controlled by sintering temperature, while the porosity and morphology of the fiber mats did
not depend on the sintering temperature. 相似文献
155.
Sung-Yong Cho Seung-Shik Park Seung-Jai Kim Tae-Young Kim 《Korean Journal of Chemical Engineering》2006,23(4):638-644
Adsorption and desorption characteristics of the 2-methyl-4-chlorophenoxyacetic acid (MCPA) from aqueous solution onto the
activated carbon (GAC, F-400) were studied. Adsorption equilibrium capacities of the MCPA increased with decreasing pH and
temperature of the solution. Adsorption equilibrium of the MCPA could be represented by the Sips equation. The internal diffusion
coefficients were determined by comparing the experimental concentration decay curves with those predicted from surface diffusion
model and pore diffusion model. The adsorption model based on the linear driving force approximation (LDFA) was used for simulating
the adsorption behavior of the MCPA in a fixed bed. Over ninety five percent desorption of the MCPA could be obtained using
distilled water. 相似文献
156.
157.
Examining the Effects of Conformal Terrain Features in Advanced Head‐Up Displays on Flight Performance and Pilot Situation Awareness 下载免费PDF全文
Synthetic vision systems (SVS) render terrain features for pilots through cockpit displays using a GPS database and three‐dimensional graphical models. Enhanced vision systems (EVS) present infrared imagery of terrain using a forward‐looking sensor in the nose of an aircraft. The ultimate goal of SVS and EVS technologies is to support pilots in achieving safety under low‐visibility and night conditions comparable to clear, day conditions. This study assessed pilot performance and situation awareness (SA) effects of SVS and EVS imagery in an advanced head‐up display (HUD) during a simulated landing approach under instrument meteorological conditions. Videos of the landing with various HUD configurations were presented to eight pilots with a superimposed tracking task. The independent variables included four HUD feature configurations (baseline [no terrain imagery], SVS, EVS, and a combination of SVS and EVS), two visibility conditions, and four legs of the flight. Results indicated that SVS increased overall SA but degraded flight path control performance because of visual confusion with other display features. EVS increased flight path control accuracy but decreased system (aircraft) awareness because of visual distractions. The combination of SVS and EVS generated offsetting effects. Display configurations did not affect pilot spatial awareness. Flight performance was not different among phases of the approach, but levels and types of pilot SA did vary from leg to leg. These results are applicable to development of adaptive HUD features to support pilot performance. They support the use of multidimensional measures of SA for insight on pilot information processing with advanced aviation displays. © 2012 Wiley Periodicals, Inc. 相似文献
158.
159.
Seong-Youl Bae Du-Hyon Cho Hee-Taik Kim Hidehiro Kumazawa 《Korean Journal of Chemical Engineering》1994,11(2):127-130
Sorption equilibria and permeation rates for oxygen and carbon dioxide in polycarbonate membrane were measured at different
temperature between 30 and 60°C and at pressures up to 2.5 MPa. The pressure dependence of mean permeability coefficient to
oxygen obeyed the conventional dual-mode mobility model, whereas that to carbon dioxide followed a modified dual-mode mobility
model with concentration-dependent diffusivities, as that of polystyrene to the same gas did. 相似文献
160.
Young-Ho Lee Shin-Guk Kim Tae-Yong Kuc Jong-Koo Park Sang-Hoon Ji Yong-Seon Moon Young-Jo Cho 《International Journal of Control, Automation and Systems》2014,12(2):390-398
A virtual target tracking approach is proposed for kinematic control of mobile robot. In the controller, linear and angular velocity inputs are generated by using the local data of robot position and orientation along with the estimated velocity of target object. Applying the proposed approach to a cooperative robot group with arbitrary number of multiple mobile robots, it is possible to create various robot formations for cooperative navigation and tracking of moving object. The developed controller is shown to be stable and convergent through theoretical proof and a series of experiments. 相似文献