全文获取类型
收费全文 | 1429篇 |
免费 | 61篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 23篇 |
综合类 | 6篇 |
化学工业 | 302篇 |
金属工艺 | 69篇 |
机械仪表 | 16篇 |
建筑科学 | 57篇 |
矿业工程 | 9篇 |
能源动力 | 52篇 |
轻工业 | 92篇 |
水利工程 | 14篇 |
石油天然气 | 5篇 |
无线电 | 194篇 |
一般工业技术 | 270篇 |
冶金工业 | 197篇 |
原子能技术 | 5篇 |
自动化技术 | 180篇 |
出版年
2022年 | 17篇 |
2021年 | 22篇 |
2020年 | 21篇 |
2019年 | 24篇 |
2018年 | 25篇 |
2017年 | 28篇 |
2016年 | 29篇 |
2015年 | 17篇 |
2014年 | 52篇 |
2013年 | 104篇 |
2012年 | 70篇 |
2011年 | 78篇 |
2010年 | 44篇 |
2009年 | 40篇 |
2008年 | 74篇 |
2007年 | 63篇 |
2006年 | 56篇 |
2005年 | 59篇 |
2004年 | 38篇 |
2003年 | 45篇 |
2002年 | 36篇 |
2001年 | 23篇 |
2000年 | 26篇 |
1999年 | 16篇 |
1998年 | 30篇 |
1997年 | 18篇 |
1996年 | 24篇 |
1995年 | 12篇 |
1994年 | 18篇 |
1993年 | 19篇 |
1992年 | 11篇 |
1991年 | 20篇 |
1990年 | 22篇 |
1989年 | 18篇 |
1988年 | 12篇 |
1987年 | 11篇 |
1986年 | 17篇 |
1985年 | 14篇 |
1984年 | 10篇 |
1982年 | 12篇 |
1980年 | 17篇 |
1979年 | 9篇 |
1976年 | 10篇 |
1975年 | 10篇 |
1973年 | 19篇 |
1972年 | 17篇 |
1971年 | 11篇 |
1969年 | 9篇 |
1961年 | 10篇 |
1959年 | 9篇 |
排序方式: 共有1491条查询结果,搜索用时 31 毫秒
91.
Mujtaba H. Jaffery Leo Shead Jason L. Forshaw Vaios J. Lappas 《International journal of control》2013,86(12):2189-2202
A new linear model predictive control (MPC) algorithm in a state-space framework is presented based on the fusion of two past MPC control laws: steady-state optimal MPC (SSOMPC) and Laguerre optimal MPC (LOMPC). The new controller, SSLOMPC, is demonstrated to have improved feasibility, tracking performance and computation time than its predecessors. This is verified in both simulation and practical experimentation on a quadrotor unmanned air vehicle in an indoor motion-capture testbed. The performance of the control law is experimentally compared with proportional-integral-derivative (PID) and linear quadratic regulator (LQR) controllers in an unconstrained square manoeuvre. The use of soft control output and hard control input constraints is also examined in single and dual constrained manoeuvres. 相似文献
92.
93.
94.
M. Pfeiffer A. Beyer B. Plnnigs A. Nollau T. Fritz K. Leo D. Schlettwein S. Hiller D. Whrle 《Solar Energy Materials & Solar Cells》2000,63(1):83
We present a systematic study on doping of vanadyl- and zinc-pathalocyanine by a fully fluorinated form of tetracyano-quinodimethane as an example of controlled doping of thin organic films by cosublimation of matrix and dopant. The films are characterized in situ by temperature dependent Seebeck and conductivity measurements. We observe a drastic increase of conductivity and a corresponding shift of the Fermi level towards the valence states with increasing dopant concentration. We thus conclude that doping has the potential of both reducing the series resistance and increasing the photovoltage of organic solar cells. As a first step to exploit this potential, we present two different ways of preparing diodes with rectification ratios in excess of 104 using doped phthalocyanines. By adding an undoped interlayer between the contact and the doped layer, we have produced diodes which work already in the strict absence of oxygen and are stable in air. To increase the efficiency of charge carrier generation in photovoltaic cells, we need to use photoactive donor–acceptor-heterojunctions. We present here first examples of pn- and pin-type heterojunctions combining p-doped and nominally undoped layers. 相似文献
95.
P. W. Griffiths M. di Leo P. Cartwright P. C. Eames P. Yianoulis G. Leftheriotis B. Norton 《Solar Energy》1998,63(4):243-249
An indium-based seal augmented with an adhesive, developed to maintain a vacuum between two sheets of glass, avoids the high temperatures required to produce a seal in evacuated glazings to date. An experimentally-validated three-dimensional transient model has been used to predict heat transfer for an indium/adhesive sealed 1 m2 area evacuated window with a highly insulating frame. An overall heat loss coefficient of 0.9 W m−2 K−1, with a midplane value of 0.36 W m−2 K−1, can be achieved with 0.72 visible transmittance for two 6 mm panes separated by 0.2 mm diameter pillars 40 mm apart. The conduction through a 3 mm edge-seal was 1.14 W m−2 K−1. Detailed three-dimensional isothermal contour plots through the system are presented. 相似文献
96.
97.
Adams Gerald R.; Ryan Bruce A.; Ketsetzis Maria; Keating Leo 《Canadian Metallurgical Quarterly》2000,14(2):237
This study examined the associations among family processes (cohesion, control, and conflict), school-focused parent–child interactions (support and pressure about achievement), and the child's own characteristics (assertiveness, frustration tolerance, intellectual effectiveness, and self-esteem) as correlates of rule compliance and peer sociability in the classroom. The sample consisted of 161 Grade 4 and 151 Grade 7 children. Family processes and parent-child interactions about school issues were associated with children's personal characteristics, which, in turn, predicted children's rule compliance and peer sociability. Some differences were found between the 4th- and 7th-grade samples; however, many variables consistently predicted the same outcomes across grades. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
98.
Concentrations of ergosterol as low as 1.2 mM are effective in satisfying the essential high specificity microrequirement
for C5,6 unsaturated sterol in yeast. In a sterol auxotroph supplemented with saturated sterol (cholestanol), aqueous extracts
of yeast provide a growth factor that eliminates the ergosterol microrequirement. The factor is easily differentiated from
ergosterol by solubility, thermostability, and thin layer and liquid chromatography and is functional at levels equivalent
to those of vitamins, hormones and pheromones. 相似文献
99.
Cerri G. De Leo R. Primiani V.M. Russo P. 《IEEE transactions on instrumentation and measurement》2008,57(2):242-247
This paper presents two test benches for the characterization of a plasma column used as a radiating element. In particular, the main parameters to be quantified are the efficiency of the plasma antenna, the turn-on time of the column, and the conductivity of the plasma. The first two parameters are evaluated by measuring the field radiated by the plasma antenna compared with that of an equivalent copper antenna. For the conductivity, a reflectometric technique is used, wherein the plasma column is inserted inside a waveguide. The accuracy of the method is limited by the ill-conditioned relationship between the reflection coefficient and the plasma conductivity; nevertheless, it is sufficient to subdivide the range of the conductivity values into three regions (i.e., low, medium, and high conductivities) to determine the best operating conditions of the antenna. 相似文献
100.
Janarthanan Supramaniam Darren Yi Sern Low See Kiat Wong Loh Teng Hern Tan Bey Fen Leo Bey Hing Goh Dazylah Darji Fatimah Rubaizah Mohd Rasdi Kok Gan Chan Learn Han Lee Siah Ying Tang 《International journal of molecular sciences》2021,22(11)
Cellulose nanofibers (CNF) isolated from plant biomass have attracted considerable interests in polymer engineering. The limitations associated with CNF-based nanocomposites are often linked to the time-consuming preparation methods and lack of desired surface functionalities. Herein, we demonstrate the feasibility of preparing a multifunctional CNF-zinc oxide (CNF-ZnO) nanocomposite with dual antibacterial and reinforcing properties via a facile and efficient ultrasound route. We characterized and examined the antibacterial and mechanical reinforcement performances of our ultrasonically induced nanocomposite. Based on our electron microscopy analyses, the ZnO deposited onto the nanofibrous network had a flake-like morphology with particle sizes ranging between 21 to 34 nm. pH levels between 8–10 led to the formation of ultrafine ZnO particles with a uniform size distribution. The resultant CNF-ZnO composite showed improved thermal stability compared to pure CNF. The composite showed potent inhibitory activities against Gram-positive (methicillin-resistant Staphylococcus aureus (MRSA)) and Gram-negative Salmonella typhi (S. typhi) bacteria. A CNF-ZnO-reinforced natural rubber (NR/CNF-ZnO) composite film, which was produced via latex mixing and casting methods, exhibited up to 42% improvement in tensile strength compared with the neat NR. The findings of this study suggest that ultrasonically-synthesized palm CNF-ZnO nanocomposites could find potential applications in the biomedical field and in the development of high strength rubber composites. 相似文献