全文获取类型
收费全文 | 54008篇 |
免费 | 1567篇 |
国内免费 | 407篇 |
专业分类
电工技术 | 360篇 |
综合类 | 903篇 |
化学工业 | 12658篇 |
金属工艺 | 1358篇 |
机械仪表 | 795篇 |
建筑科学 | 8160篇 |
矿业工程 | 1086篇 |
能源动力 | 7136篇 |
轻工业 | 3417篇 |
水利工程 | 2192篇 |
石油天然气 | 600篇 |
武器工业 | 8篇 |
无线电 | 1033篇 |
一般工业技术 | 9558篇 |
冶金工业 | 815篇 |
原子能技术 | 401篇 |
自动化技术 | 5502篇 |
出版年
2024年 | 57篇 |
2023年 | 1235篇 |
2022年 | 892篇 |
2021年 | 1225篇 |
2020年 | 2005篇 |
2019年 | 2046篇 |
2018年 | 1512篇 |
2017年 | 2055篇 |
2016年 | 2802篇 |
2015年 | 2433篇 |
2014年 | 3365篇 |
2013年 | 3931篇 |
2012年 | 2501篇 |
2011年 | 3227篇 |
2010年 | 2868篇 |
2009年 | 2943篇 |
2008年 | 1791篇 |
2007年 | 2705篇 |
2006年 | 2473篇 |
2005年 | 1888篇 |
2004年 | 1310篇 |
2003年 | 1298篇 |
2002年 | 1417篇 |
2001年 | 1156篇 |
2000年 | 661篇 |
1999年 | 796篇 |
1998年 | 476篇 |
1997年 | 271篇 |
1996年 | 417篇 |
1995年 | 308篇 |
1994年 | 224篇 |
1993年 | 205篇 |
1992年 | 175篇 |
1991年 | 162篇 |
1990年 | 157篇 |
1989年 | 147篇 |
1988年 | 353篇 |
1987年 | 787篇 |
1986年 | 715篇 |
1985年 | 215篇 |
1984年 | 136篇 |
1983年 | 133篇 |
1982年 | 103篇 |
1981年 | 92篇 |
1980年 | 68篇 |
1979年 | 94篇 |
1978年 | 66篇 |
1977年 | 18篇 |
1976年 | 37篇 |
1975年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
The biological decolorization of two industrial, spent textile reactive dyebaths was investigated using a suspended-growth, halophilic mixed culture fed with glucose. Dyebath I contained mainly Reactive Blue 19 (RB19), an anthraquinone dye, whereas dyebath II contained mainly Reactive Blue 21 (RB21), a phthalocyanine dye. Batch assays under anaerobic conditions with the two neutralized dyebaths resulted in 87 and 37% extent of decolorization for dyebaths I and II, respectively. The rate of glucose utilization and the extent of acetate production were impacted in the presence of each dyebath as compared to the control culture. However, dyebath decolorization occurred despite moderate culture inhibition. Reuse of a biologically renovated RB19-containing dyebath in the dyeing process resulted in reproducible but not identical cotton fabric shades as compared to a standard dyeing (i.e., control) using fresh water. This difference is attributed to a variable degree of RB19 aggregation during the dyeing process and is not related to the efficiency of the biodecolorization process. Further improvement of the redyeing efficiency will lead to the development of an in-plant, closed-loop decolorization system resulting in significant water conservation and minimization of textile pollutants such as salt and dyes. 相似文献
83.
《Journal of the European Ceramic Society》2005,25(9):1629-1636
Ultimate tensile strength of five different continuous fiber-reinforced ceramic matrix composites (CMCs), including SiCf/BSAS (two dimensional (2D), 2 types), SiCf/MAS (2D), SiCf/SiC (2D), and Cf/SiC (2D, 2 types), was determined as a function of test rate at 1100–1200 °C in air. All five CMCs exhibited a significant dependency of ultimate tensile strength on test rate such that the ultimate tensile strength decreased with decreasing test rate. The dependency of ultimate tensile strength on test rate, the applicability of preload technique, and the predictability of life from one loading configuration (constant stress-rate loading) to another (constant stress loading) all suggested that the overall, phenomenological delayed failure of the CMCs would be governed by a power-law type of slow crack growth. 相似文献
84.
Catherine J. Harrison Yann A. Le Gouellec Robert C. Cheng Amy E. Childress 《Canadian Metallurgical Quarterly》2007,133(11):1004-1014
A dual-staged nanofiltration process is being evaluated as an alternative to reverse osmosis for seawater desalination. The primary goal of this system is to reduce energy consumption while producing potable water at an acceptable recovery rate. Investigation of this system at the bench-scale level focused on membrane surface characterization, ion rejection (including boron, bromide, and iodide rejection), and flux decline. Results from this study showed that two commercially available nanofiltration membranes can effectively desalinate seawater. Although fouling was apparent—and resulted in approximately 20% flux decline over 3 days—a critical flux was not identifiable. Operation of the system at different cross-flow velocities revealed the significance of hydrodynamic conditions on the polarization modulus, and hence on membrane performance. 相似文献
85.
86.
《Advanced Powder Technology》2007,18(4):467-483
The rates of alkoxylation and rehydroxylation reactions were investigated on silica surfaces preheated at various temperatures. The effect of preheating temperature was examined for both reactions. The initial rate of reaction was analyzed and discussed as a representative reactivity of the silica surface. For the alkoxylation reaction, the apparent rate of reactions on the total active sites was analyzed by measuring the alkoxyl groups formed on the surface. The rate of the alkoxylation reaction increased with the preheating temperature, which could be attributed to the increase in the number of reactive siloxane bridges. It was shown that the preheating treatment caused the compensation effect for the surface alkoxylation reactions. An analysis for the state of the activated complex in the reaction was proposed to discuss the kinetic characteristics. For the rehydroxylation reaction, the rate of reaction forming hydroxyls from siloxane bridges was measured. The rate of rehydroxylation decreased with increasing the preheating temperature. For both the alkoxylation and rehydroxylation, the reactivity of siloxane bridges decreased with increasing the preheating temperature. 相似文献
87.
B Neppolian H C Choi S Sakthivel Banumathi Arabindoo V Murugesan 《Journal of hazardous materials》2002,89(2-3):303-317
The photocatalytic degradation of three commercial textile dyes with different structure has been investigated using TiO(2) (Degussa P25) photocatalyst in aqueous solution under solar irradiation. Experiments were conducted to optimise various parameters viz. amount of catalyst, concentration of dye, pH and solar light intensity. Degradation of all the dyes were examined by using chemical oxygen demand (COD) method. The degradation efficiency of the three dyes is as follows: Reactive Yellow 17(RY17) > Reactive Red 2(RR2) > Reactive Blue 4 (RB4), respectively. The experimental results indicate that TiO(2) (Degussa P25) is the best catalyst in comparison with other commercial photocatalysts such as, TiO(2) (Merck), ZnO, ZrO(2), WO(3) and CdS. Though the UV irradiation can efficiently degrade the dyes, naturally abundant solar irradiation is also very effective in the mineralisation of dyes. The comparison between thin-film coating and aqueous slurry method reveals that slurry method is more efficient than coating but the problems of leaching and the requirement of separation can be avoided by using coating technique. These observations indicate that all the three dyes could be degraded completely at different time intervals. Hence, it may be a viable technique for the safe disposal of textile wastewater into the water streams. 相似文献
88.
Motoharu Fujigaki In Hong Yang Yoshiharu Morimoto Eung Kyo Han 《NDT & E International》1996,29(4):197-203
There is no good method to measure the shape and the strain distributions of a structure changing with time. We have previously proposed the Fourier transform grid method (FTGM) to measure the three-dimensional shape and surface strain distributions of stationary objects by analysing the two-dimensional grating images recorded with two cameras. In the stereoscopic method, it is very important to determine the accurate geometric parameters of the camera system. In this paper, the positions and the directions of cameras are accurately determined using the FTGM applied to images of a reference object on which a two-dimensional grating is drawn. Applications for analysing shape and strain distributions of vibrating rubber plates and a moving human skin are shown. 相似文献
89.
《Automation in Construction》2005,14(1):71-84
This paper presents an interactive speech and gesture recognition-based, immersive Augmented Reality (AR) model designed to visualize and interact with buildings and their thermal environments. The paper introduces a Human–Building Interaction (HBI) model that allows for the efficient exploration of Computational Fluid Dynamics (CFD) data sets in real time. This model includes four components: wireless sensor data, CFD analysis, Human–Computer Interaction (HCI), and AR visualization. The sensor data component tracks temperature and velocity changes that occur within a room and updates the boundary conditions for simulation. The CFD analysis component performs simulation with the new boundary conditions, and the post-processed data are exported as Virtual Reality Modeling Language (VRML) models. The HCI component consists of a library of gesture recognition tasks. These tasks update and process data for the AR visualization component. The AR visualization component aids in tracking the user's movement in real time and poses graphical information onto the Head-Mounted Device (HMD), allowing the user to visualize CFD data sets that are superimposed on to the actual scene. 相似文献
90.
A mathematical model was developed to describe the removal of volatile organic compounds from drinking water in aeration basins. The model was used to simulate removal under a range of expected treatment conditions using the Continuous Systems Modeling Program. Results indicated that temperature and air-to-water ratio are the major factors influencing the removal of chloroform from water in an aeration basin. Bubble diameter was a lesser factor while liquid residence time had the smallest effect of the variables examined. 相似文献