全文获取类型
收费全文 | 8215篇 |
免费 | 278篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 99篇 |
综合类 | 13篇 |
化学工业 | 1739篇 |
金属工艺 | 177篇 |
机械仪表 | 162篇 |
建筑科学 | 445篇 |
矿业工程 | 14篇 |
能源动力 | 202篇 |
轻工业 | 621篇 |
水利工程 | 50篇 |
石油天然气 | 18篇 |
武器工业 | 2篇 |
无线电 | 518篇 |
一般工业技术 | 1368篇 |
冶金工业 | 1580篇 |
原子能技术 | 60篇 |
自动化技术 | 1435篇 |
出版年
2022年 | 74篇 |
2021年 | 141篇 |
2020年 | 111篇 |
2019年 | 149篇 |
2018年 | 140篇 |
2017年 | 117篇 |
2016年 | 161篇 |
2015年 | 153篇 |
2014年 | 190篇 |
2013年 | 477篇 |
2012年 | 333篇 |
2011年 | 474篇 |
2010年 | 365篇 |
2009年 | 333篇 |
2008年 | 426篇 |
2007年 | 389篇 |
2006年 | 332篇 |
2005年 | 266篇 |
2004年 | 245篇 |
2003年 | 232篇 |
2002年 | 235篇 |
2001年 | 136篇 |
2000年 | 111篇 |
1999年 | 133篇 |
1998年 | 173篇 |
1997年 | 131篇 |
1996年 | 149篇 |
1995年 | 145篇 |
1994年 | 122篇 |
1993年 | 121篇 |
1992年 | 113篇 |
1991年 | 84篇 |
1990年 | 95篇 |
1989年 | 111篇 |
1988年 | 77篇 |
1987年 | 80篇 |
1986年 | 93篇 |
1985年 | 100篇 |
1984年 | 89篇 |
1983年 | 107篇 |
1982年 | 96篇 |
1981年 | 91篇 |
1980年 | 83篇 |
1979年 | 87篇 |
1978年 | 69篇 |
1977年 | 73篇 |
1976年 | 79篇 |
1975年 | 71篇 |
1974年 | 50篇 |
1973年 | 56篇 |
排序方式: 共有8503条查询结果,搜索用时 15 毫秒
111.
Supercritical Carbon Dioxide (SC CO2) is used as a reaction/processing medium in the fabrication of fiber‐reinforced composite materials. SC CO2 allows resin (reactive monomer), to penetrate inside the fibers themselves, partitioning into the amorphous regions of the fiber. The crystal structure then templates polymerization of matrix within the fiber. This process produces a composite that exhibits ultralong‐range order from the nanoscale reinforcement of crystals to the macroscale fiber reinforcement of matrix. In addition, SC CO2 lowers resin viscosity and aids in wetting out Nylon 6,6 fiber reinforcement in a process similar to reaction injection molding (RIM) or resin transfer molding (RTM). This article will discuss the fabrication technique in detail, including process parameters and the structure of resulting composites and morphology of modified fibers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1600–1607, 2003 相似文献
112.
Thermal stability of composite phase change material microcapsules incorporated with silver nano-particles 总被引:3,自引:0,他引:3
This paper reports a study on the thermal stability of phase change material microcapsules that are incorporated with silver nano-particles (Ag-NPs). The novel microcapsules were fabricated by the technique of in situ polymerization, with aminoplast as the wall and phase change material bromo-hexadecane (PCM BrC16) as the core. Thermal gravimetry (TG) analysis was applied to measure the thermal stability of these microcapsules and surface morphology of the microcapsules was observed by means of scanning electron microscopy (SEM) after an application of curing treatment at 130 °C. Comparing with conventional phase change material microcapsules (PCMMs), nano-composite phase change material microcapsules (NCPCMMs) have higher thermal stability. This can be attributed to nano-composite structure of the microcapsules, in which metal Ag-NPs distributed on the surface to increase wall toughness and strength. The possible reinforcement mechanisms of the nano-composite structure are explored. 相似文献
113.
Specimens of two engineerig plastics i.e., poly(ether imide), PEI, and poly(2,6-dimethyl- 1,4-phenylene ether), PPE, were injection molded employing a 40t Van Dorn injection molding machine and industrial practices. The mold and melt temperatures and the injection speed were varied in a limited range which furnished acceptable samples. The density, birefringence, residual stress distributions, flexure and tensile properties, and crack development of the injection molded specimens were studied. Vacuum compression molded samples were also prepared to investigate the role played by the cooling rate in shaping microstructural distributions. The results revealed significant differences in the development of microstructure of the molded specimens of the two resins, which was related to rheology and molding conditions on one hand and to development of cracks and ultimate properties on the other hand. 相似文献
114.
There is a growing emphasis in many countries on matters such as participation in e-government, e-democracy, the provision of forums for online debate, and so on. A critical issue in all of these cases is one of encouraging engagement across a broad spectrum of potentially interested parties and stakeholders. In this paper, we use an ethnographic study of an online event, designed to encourage debate, to explore some critical issues in how the mechanisms productive of debate have shifted in company with the Web 2.0 phenomenon. By contrasting this with a prior study of how players managed their gameplay in a multiplayer pervasive game, we focus upon how different ways of constructing games and events can have serious implications for their ordinary everyday reportability in routine face-to-face interactions. We conclude that designing for reportability should be an active consideration when designing the resources for online debate and consider some ways in which that might be accomplished. 相似文献
115.
We present a wearable input system which enables interaction through 3D handwriting recognition. Users can write text in the air as if they were using an imaginary blackboard. The handwriting gestures are captured wirelessly by motion sensors applying accelerometers and gyroscopes which are attached to the back of the hand. We propose a two-stage approach for spotting and recognition of handwriting gestures. The spotting stage uses a support vector machine to identify those data segments which contain handwriting. The recognition stage uses hidden Markov models (HMMs) to generate a text representation from the motion sensor data. Individual characters are modeled by HMMs and concatenated to word models. Our system can continuously recognize arbitrary sentences, based on a freely definable vocabulary. A statistical language model is used to enhance recognition performance and to restrict the search space. We show that continuous gesture recognition with inertial sensors is feasible for gesture vocabularies that are several orders of magnitude larger than traditional vocabularies for known systems. In a first experiment, we evaluate the spotting algorithm on a realistic data set including everyday activities. In a second experiment, we report the results from a nine-user experiment on handwritten sentence recognition. Finally, we evaluate the end-to-end system on a small but realistic data set. 相似文献
116.
Steam reforming of isobutane on a 0.5% Pt–Ce0.8Gd0.2O1.9 catalyst was carried out from 300 to 700 °C under integral conditions with a gas hourly space velocity (GHSV) of 12,000 h−1. The major products were H2, CO2, CO and CH4. The other products produced were ethane, ethylene, propane and propylene with a total molar composition of less than 1.5%.
A complete conversion of isobutane was achieved at 700 °C, Kinetic data was obtained by changing the partial pressure of the
reactants and the temperature under differential conditions with a GHSV of 55,400 h−1. This was done after observing stable isobutane steam reforming for 160 h and under conditions where the mass transfer limitations
were insignificant. An empirical Langmuir–Hinshelwood type model that best fit the kinetic data available was developed. 相似文献
117.
Improvement of WAXD patterns from aligned glassy polymers by a numerical desmearing technique is reported. This gives a fibre type diffraction pattern that can be more easily interpreted than radial or cylindrical distribution functions. Application to atactic and quenched isotactic polystyrene shows that the molecular conformations that are found are in agreement with those deduced from i.r. and n.m.r. spectroscopy. For isotactic polystyrene there is significant agreement between the fibre pattern of the aligned glassy polymer and that of the drawn crystalline polymer. 相似文献
118.
Although enterprise systems (ES) are ubiquitous, many firms report less than stellar payoffs from these costly investments, with underutilization often attributed to failures in the implementation process. Unfortunately, research has not provided sufficient insights into these failures, in part because it has focused on actual usage, as opposed to proficient usage, as the benchmark for successful implementation. Moreover, research has not generally examined how the adoption process unfolds over time, thus overlooking potential underlying mechanisms that may help explain how adopters achieve proficiency. To begin addressing these shortcomings, we study how adopters’ pre-adoption expectations, enacted over time, can influence their post-adoption proficiency, by shaping how and why they spend time using the system during the adoption period. We analyzed time-lagged survey data from 153 financial analysts, required to adopt new ES-based software, at a multinational bank. We found that adopters who hold pre-adoption expectations reflecting greater internal and external motives to adopt the system as well as systematically integrate it into their work routines are more apt to use the system in ways that enhance their cumulative knowledge of it, and subsequently develop higher levels of proficiency post-adoption. Moreover, greater organizational support enhanced the impact of adopters’ expectations on proficiency, except when their actual use is low in which case organizational support had an adverse effect. 相似文献
119.
The catalytic activity and selectivity of three PdO-MoO3/-Al2O3 catalysts containing about 2% Pd and 2% Mo were studied for the reduction of NO by h2 in the presence of varying amounts of oxygen at temperatures from 50 to 550 °C. The results are compared with those for PdO/-Al2O3, PdO-MoO3/-Al2O3 containing 2% Pd and 20% Mo, and a commercial Pt-Rh catalyst. In the absence of oxygen, the conversion of NO to N2 and N2O is higher on the three catalysts than it is on PdO/-Al2O3 at 500 and 550 °C. In the presence of oxygen, the yields of N2 and N2O are generally lower on two of the PdO-MoO3/-Al2O3 catalysts than on PdO/-Al2O3. 相似文献
120.
The solubility of CO2 in triethylene glycol monomethyl ether (TEGMME) has been measured at 40, 70 and 100°C at pressures up to 8.8 MPa. The results were correlated with the Peng-Robinson (1976) equation of state. The interaction parameters and Henry's constants were derived. 相似文献