全文获取类型
收费全文 | 1423篇 |
免费 | 67篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 25篇 |
综合类 | 1篇 |
化学工业 | 308篇 |
金属工艺 | 26篇 |
机械仪表 | 29篇 |
建筑科学 | 82篇 |
能源动力 | 42篇 |
轻工业 | 110篇 |
水利工程 | 7篇 |
石油天然气 | 2篇 |
无线电 | 189篇 |
一般工业技术 | 222篇 |
冶金工业 | 252篇 |
原子能技术 | 9篇 |
自动化技术 | 187篇 |
出版年
2023年 | 13篇 |
2022年 | 14篇 |
2021年 | 39篇 |
2020年 | 28篇 |
2019年 | 31篇 |
2018年 | 34篇 |
2017年 | 37篇 |
2016年 | 43篇 |
2015年 | 36篇 |
2014年 | 55篇 |
2013年 | 100篇 |
2012年 | 42篇 |
2011年 | 91篇 |
2010年 | 72篇 |
2009年 | 52篇 |
2008年 | 68篇 |
2007年 | 80篇 |
2006年 | 49篇 |
2005年 | 56篇 |
2004年 | 36篇 |
2003年 | 51篇 |
2002年 | 33篇 |
2001年 | 28篇 |
2000年 | 28篇 |
1999年 | 24篇 |
1998年 | 74篇 |
1997年 | 32篇 |
1996年 | 27篇 |
1995年 | 26篇 |
1994年 | 15篇 |
1993年 | 22篇 |
1992年 | 13篇 |
1991年 | 14篇 |
1990年 | 8篇 |
1989年 | 10篇 |
1988年 | 13篇 |
1987年 | 7篇 |
1986年 | 10篇 |
1985年 | 8篇 |
1984年 | 4篇 |
1983年 | 10篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1976年 | 7篇 |
1974年 | 3篇 |
1973年 | 3篇 |
1961年 | 2篇 |
排序方式: 共有1491条查询结果,搜索用时 15 毫秒
41.
Alexandre Ruellan Violette Ducruet Audrey Gratia Lidia Saelices Jimenez Alain Guinault Cyrille Sollogoub Guillaume Chollet Sandra Domenek 《Polymer International》2016,65(6):683-690
Polylactide (PLA) is the most used biodegradable and biobased food packaging polymer for rigid containers and films. However, its low ductility is a hurdle for increasing its applications in flexible food packaging. A solution is the use of additives. Palm oil deodorizer distillate (PODC) is revealed to be an excellent additive promoting PLA ductility. PODC is a by‐product of vegetable oil refining, which is available in stable quality and in sufficient amounts. Amorphous PLA/PODC blends had an elongation at break of around 130% and that of semi‐crystalline blends was still around 55% compared to the initial 5% of neat PLA. At the same time the PLA rigidity and high glass transition temperatures were kept. PODC was also a very efficient processing aid, allowing for film blow extrusion. The blends were stable in properties during six months without exudation. They complied with legal norms of Food Contact Materials (EU 10/2011) and induced no sensorial alteration of packed food. Therefore PODC is a very interesting alternative to common plasticizers for the production of flexible PLA packaging films. © 2016 Society of Chemical Industry 相似文献
42.
43.
A prominent problem in airline crew scheduling is the pairings or Tour-of-Duty planning problem. The objective is to determine a set of pairings (or Tours-of-Duty) for a crew group to minimise the planned cost of operating a schedule of flights. However, due to unforeseen events the
performance in operation can differ considerably from planning, sometimes causing significant additional recovery costs. In
recent years there has been a growing interest in robust crew scheduling. Here, the aim is to find solutions that are “cheap”
in terms of planned cost as well as being robust, meaning that they are less likely to be disrupted in case of delays. Taking
the stochastic nature of delays into account, Yen and Birge (Transp Sci 40:3–14, 2006) formulate the problem as a two-stage
stochastic integer programme and develop an algorithm to solve this problem. Based on the contradictory nature of the goals,
Ehrgott and Ryan (J Multi-Criteria Decis Anal 11:139–150, 2002) formulate a bi-objective set partitioning model and employ
elastic constraint scalarisation to enable the solution by set partitioning algorithms commercially used in crew scheduling
software. In this study, we compare the two solution approaches. We improve the algorithm of Yen and Birge (Transp Sci 40:3–14,
2006) and implement both methods with a commercial crew scheduling software. The results of both methods are compared with
respect to characteristics of robust solutions, such as the number of aircraft changes for crew. We also conduct experiments
to simulate the performance of the obtained solutions. All experiments are performed using actual schedule data from Air New
Zealand. 相似文献
44.
Although partner support represents a significant source of help amongst people (Beach, Fincham, Katz, & Bradbury, 1996; Cutrona, 1996), few valid and reliable measures of couple support are available. The current study presents the elaboration and validation of the “Questionnaire de soutien conjugal” (QSC), a brief measure evaluating given and received support within conjugal relationship. A sample of 270 French-Canadian couples completed the QSC and a short version of the Dyadic Adjustment Scale (Spanier, 1976; Sabourin, Valois, & Lussier, 2005). One year later, 160 couples agreed to complete the same measures again. Exploratory Factor Analyses supported the two-factor structure of the measure (provided support and received support); those factors predicted current and future couple satisfaction. QSC scales also showed good internal consistency as well as good test–retest reliability after a 1-year period. These findings reveal satisfactory psychometric properties and justify the QSC's use in clinical settings and research protocols. Strengths, limitations, and recommendations for futures research are discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
45.
Xizu Wang Jian Wei Ho Qingyi Yang Hoi Lam Tam Gui Xin Li Kok Wai Cheah Furong Zhu 《Organic Electronics》2011,12(11):1943-1947
In this work, Ag nanoparticles were modified by an ultra-thin plasma-polymerized fluorocarbon film (CFX) to form a composite CFX-modified Ag nanoparticles/indium tin oxide (ITO) anode for application in organic photovoltaic (OPV) devices. A CFX-modified Ag nanoparticles/ITO anode exhibited a superior surface work function of 5.4 eV suited for application in OPV devices. The performance of zinc phthalocyanine:fullerene-based OPV devices showed a significant improvement when the structural identical cells are made with the CFX-modified Ag nanoparticles/ITO. This work yielded a promising power conversion efficiency of 3.5 ± 0.1%, notably higher than that with a bare ITO anode (2.7 ± 0.1%). 相似文献
46.
Cracks in glass under triaxial conditions 总被引:1,自引:0,他引:1
Audrey Ougier-Simonin Jérôme Fortin Alexandre Schubnel 《International Journal of Engineering Science》2011,49(1):105-121
This experimental work documents the mechanical evolution of synthetic glass (SON68) under compressive triaxial stresses (hydrostatic and deviatoric conditions). The experimental setup enabled to monitor and vary independently confining pressure (range: [0, 50] MPa) and axial stress (up to 680 MPa) at room temperature. An optimized set of sensors allowed us to perform measurements during the experiments of: (i) axial and radial deformation, (ii) P- and S-elastic wave velocities, and (iii) acoustic emissions. In addition, in some samples, initial crack densities up to a value of 0.24 were introduced by thermal cracking. We compare the original synthetic glass data set to results obtained in the same experimental conditions on thermally cracked glass and on a basaltic rock with similar petrophysical properties (porosity, chemistry).Stress-strain data depict original linear elastic glass properties even up to an axial stress of 680 MPa (under 15 MPa confining pressure). A strong strength decrease (370 MPa at 15 MPa confining pressure) is observed for thermally cracked samples. Elastic wave velocity data highlight that cracks are mostly closed at a confining pressure of ∼30 MPa. The basaltic rock seems to correspond to an intermediate state between an original and a thermally treated glass. In all samples, damage was accompanied by dynamic crack propagation, producing large magnitude acoustic emissions. Thanks to a continuous recorder, we could locate a number of acoustic emissions in order to image the microcracking pattern evolution prior to failure. 相似文献
47.
The evolution of mobile telecommunication networks and access bandwidth has enabled operators to deliver IPTV services for mobile customers; however, the existing mobile charging solutions are not effectively addressing the billing requirements of multimedia streams. This paper develops a quality‐based charging solution for 3GPP wireless networks with the aim of providing a fair pricing solution for multimedia services. An appropriate business model is selected and a streaming proxy‐based charging architecture is developed based on the quality of the multimedia service. The proposed algorithms are theoretically evaluated by the derivation of the formulas of the distribution and the expected value of the price discount. A testbed is built and the findings are evaluated and compared with traditional charging functions. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
48.
Ngoc Kim Pham Do Trung Nguyen Bang Tam Thi Dao Kieu Hanh Thi Ta Vinh Cao Tran Van Hieu Nguyen Sang Sub Kim Shinya Maenosono Thang Bach Phan 《Journal of Electronic Materials》2014,43(7):2747-2753
We have investigated the switching behavior of as-deposited CrO x and post-annealed CrO y films by use of a variety of electrodes (top electrode Ag, Ti; bottom electrode Pt, fluorine tin oxide (FTO)). Resistance switching is highly dependent on electrode material and post-annealing treatment. Among Pt devices, I–V hysteresis was observed for the Ag/CrO x /Pt device only; no resistance switching was observed for Ag/CrO y /Pt, Ti/CrO x /Pt, and Ti/CrO y /Pt devices. Among FTO devices, I–V hysteresis was observed for the Ag/CrO x /FTO device whereas I–V hysteresis with the opposite switching direction was observed for Ag/CrO y /FTO, Ti/CrO x /FTO, and Ti/CrO y /FTO devices. The direction of switching depends not only on electrode material but also on post-annealing treatment, which affects the density of grain boundaries. Thus, the density of grain boundaries determines the type of charge carrier involved in the switching process. For as-deposited CrO x films with a high density of grain boundaries Ag filament paths mediated by electrochemical redox reaction were observed, irrespective of bottom electrode material (Pt or FTO). Post-annealed CrO y films with a low density of grain boundaries suppressed electrochemical redox reaction in the Ag/CrO y /Pt device but promoted short-range movement of O2? ions through the bottom interface, resulting in resistance switching in the Ag/CrO y /FTO device. Electrochemical redox reaction-controlled resistance switching occurred solely in oxides with a high density of grain boundaries or dislocations. 相似文献
49.
Phuong Dinh Tam Hoang Sy Hong Nguyen Van Hieu 《Journal of Experimental Nanoscience》2014,9(7):652-660
A novel, portable, electrical detection system was constructed for DNA sensor application to detect DNA hybridisation. The read-out circuit consists of an analogue circuit and a digital circuit. The analogue circuit with an IC MAX038 generates a sine wave with a constant frequency (10?kHz), which serves as the input for the DNA sensor. The DNA sensor consists of active and reference sensors. DNA hybridisation between the DNA probe and the target sequences causes changes in the conductance of the conductive membrane (DNA/MWCNTs) on the sensor surface, which lead to changes in the amplitude of the sine wave from the sensor output compared with that of the reference signal output (input sine wave). We used a digital circuit with a microprocessor (PIC33FJ256MC710) to determine the change in the amplitude of the sine wave signal of the sensor. From these digital data, the difference in the amplitudes of the active and reference sensors was calculated and displayed on the liquid crystal display. Measurement results show that the portable electrical detection system can detect DNA target concentrations as low as 0.16?µM. The detection of the amplified polymerase chain reaction sample and the reproducibility of the DNA sensor results were also determined using the designed readout circuit. The proposed electrical detection system is suitable for DNA sensor application. 相似文献
50.
V. Senthilkumar ;Le C. Tam ;Yong Soo Kim ;Yumin Sim ;Maeng-Je Seong ;Joon. I. Jang 《Nano Research》2014,(12):1759-1768
There has been growing research interest in the use of molybdenum disulfide in the fields of optoelectronics and energy harvesting devices, by virtue of its indirect-to-direct band gap tunability. However, obtaining large area thin films of MoS2 for future device applications still remains a challenge. In the present study, the amounts of the precursors (S and MOO3) were varied systematically in order to optimize the growth of highly crystalline and large area MoS2 layers by the chemical vapor deposition method. Careful control of the amounts of precursors was found to the key factor in the synthesis of large area highly crystalline flakes. The thickness of the layers was confirmed by Raman spectroscopy and atomic force microscopy. The optical properties and chemical composition were studied by photoluminescence (PL) and X-ray photoelectron spectroscopy. The emergence of strong direct excitonic emissions at 1.82 eV (A-exciton, with a normalized PL intensity of -55 × 10^3) and 1.98 eV (B-exciton, with a normalized PL intensity of -5 × 10^3) of the sample at room temperature clearly indicates the high luminescence quantum efficiency. The mobility of the films was found to be 0.09 cm^2/(V.s) at room temperature. This study provides a method for the controlled synthesis of high-quality two-dimensional (2D) transition metal dichalcogenide materials, useful for applications in nanodevices, optoelectronics and solar energv conversion. 相似文献