全文获取类型
收费全文 | 4636篇 |
免费 | 435篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 49篇 |
综合类 | 6篇 |
化学工业 | 1367篇 |
金属工艺 | 72篇 |
机械仪表 | 104篇 |
建筑科学 | 201篇 |
矿业工程 | 14篇 |
能源动力 | 123篇 |
轻工业 | 542篇 |
水利工程 | 34篇 |
石油天然气 | 12篇 |
无线电 | 492篇 |
一般工业技术 | 811篇 |
冶金工业 | 576篇 |
原子能技术 | 49篇 |
自动化技术 | 629篇 |
出版年
2022年 | 43篇 |
2021年 | 52篇 |
2020年 | 63篇 |
2019年 | 103篇 |
2018年 | 123篇 |
2017年 | 130篇 |
2016年 | 163篇 |
2015年 | 141篇 |
2014年 | 203篇 |
2013年 | 315篇 |
2012年 | 223篇 |
2011年 | 254篇 |
2010年 | 226篇 |
2009年 | 217篇 |
2008年 | 237篇 |
2007年 | 181篇 |
2006年 | 193篇 |
2005年 | 156篇 |
2004年 | 147篇 |
2003年 | 136篇 |
2002年 | 130篇 |
2001年 | 98篇 |
2000年 | 108篇 |
1999年 | 73篇 |
1998年 | 92篇 |
1997年 | 76篇 |
1996年 | 84篇 |
1995年 | 64篇 |
1994年 | 76篇 |
1993年 | 62篇 |
1992年 | 53篇 |
1991年 | 35篇 |
1990年 | 56篇 |
1989年 | 50篇 |
1988年 | 31篇 |
1987年 | 37篇 |
1986年 | 33篇 |
1985年 | 45篇 |
1984年 | 49篇 |
1983年 | 43篇 |
1982年 | 39篇 |
1981年 | 37篇 |
1980年 | 34篇 |
1979年 | 46篇 |
1978年 | 17篇 |
1977年 | 42篇 |
1976年 | 31篇 |
1975年 | 23篇 |
1974年 | 23篇 |
1973年 | 24篇 |
排序方式: 共有5081条查询结果,搜索用时 0 毫秒
21.
Bourque Paul; Blanchard Louis; Saulnier Jo?l; Vézina Jean 《Canadian Metallurgical Quarterly》1992,24(1):118
Studied the relationship among age, physical health status, and psychic and somatic symptoms of depression among elderly adults. Human Ss: 318 male and female Canadian older adults (aged 65–102 yrs). Information on sociodemographic factors and health status was obtained using the Older American Research Scale, French version, by R. Lefran?ois et al (1988). A French version by P. Bourque and D. Beaudette (1982) of the Beck Depression Inventory was also used. The results were evaluated according to each S's sex, age, institutionalized residence status, and health status. Statistical tests were used. (English abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
22.
Forster Jean L.; Jeffery Robert W.; Schmid Thomas L.; Kramer F. Matthew 《Canadian Metallurgical Quarterly》1988,7(6):515
Evaluated the feasibility and effectiveness of a program for weight gain prevention (WGP) in normal adults. 219 Ss were randomized to either WGP treatment or no treatment for 12 mo. The treatment group received monthly newsletters relating to weight management, participated in a financial incentive system, and were offered an optional 4-session education course in the 6th mo of the program. Results demonstrate high interest in WGP among Ss who were not objectively overweight. Participation, as measured by return of postcards sent with each newsletter, was approximately 75%. Results after 1 yr show a net weight loss of 1.8 lb in the group receiving the program compared with controls. 82% of participants maintained or lost weight, compared with 56% of controls. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
23.
Auguste Commeyras Hlne Collet Laurent Boiteau Jacques Taillades Odile Vandenabeele‐Trambouze Herv Cottet Jean‐Philippe Biron Raphaël Plasson Louis Mion Olivier Lagrille Herv Martin Franck Selsis Michel Dobrijevic 《Polymer International》2002,51(7):661-665
Addressing the still open question of the prebiotic origin of sequential macromolecules (peptides, nucleic acids) on the primitive Earth, we describe a molecular engine (the primary pump), which works at ambient temperature and continuously generates, elongates and complexifies sequential peptides. This new scenario is based on a cyclic reaction sequence, whose keystep is the activation of amino acids into their N‐carboxyanhydrides (NCA) through nitrosation by NOx. This process could have taken place on tidal beaches; it requires a buffered ocean, emerged land and a nitrosating atmosphere. With the help of geochemical studies and computer simulations of atmosphere photochemistry, we show that the primitive Earth during the Hadean may have satisfied all these requirements. © 2001 Society of Chemical Industry. 相似文献
24.
André Girard Pierre Dominique Lansard Bernard Liau Anne Marie Mongeon Jean Luc Thibault 《电信纪事》1991,46(5-6):335-350
Classical hierarchical routing in telephone networks is extended to a wider class called out-of-chain routing in such a way that some useful properties of hierarchical routing are retained. This new routing pattern offers more potential paths than the fixed hierarchical one and can be introduced as a dynamic routing where the fixed alternate sequences change at some predetermined instants during the day. The effect of this new routing pattern on the network performances is examined. The main topic of this paper is to present heuristic methods used to optimise such routings in large networks. We show on artificial networks that the throughput of a given network can be significantly improved by suitable routing choices. We demonstrate that the integration of routing changes within a multihour dimensioning process is possible but the lack of realistic data does not permit at this time to quantify the value of routing optimization on real networks. 相似文献
25.
To disperse nano-sized γ-alumina powders in non-polar solvents, the surface of γ-alumina has to be modified with unsaturated oleic acid, which forms aluminum-oleate on the surface. This changes the surface characteristics of γ-alumina powders from hydrophilic to hydrophobic in nature. A colloidally stable γ-alumina non-polar suspension is obtained when a critical amount of aluminum-oleate compound is formed on the surface. This is also evidenced by the results of adsorption and theoretical calculation of potential energies, which confirm the colloidal stability of organic γ-alumina suspension caused by the steric repulsion mechanism. 相似文献
26.
27.
28.
Sarrazin Jean-Christophe; Giraudo Marie-Dominique; Pailhous Jean; Bootsma Reinoud J. 《Canadian Metallurgical Quarterly》2004,30(3):411
In 3 experiments, the authors studied the organization of spatiotemporal information in memory. Stimuli consisted of configurations of dots, presented sequentially. The stimuli were either proportional, with interdot distances corresponding to interdot durations, or not proportional, with interdol distances not corresponding to interdot durations. After a learning phase, participants reproduced the spatial (Experiment 1), temporal (Experiment 2), or spatial and temporal (Experiment 3) characteristics of the target 60 times in succession. In the nonproportional conditions, effects of variable interdot durations or distances on the reproduction of, respectively, constant distances (tau effect) or durations (kappa effect) were observed, whereas no such effects were observed when variable distances or durations were to be produced. Tau and kappa effects influenced the accuracy but not the variability of responses. The results are discussed in light of the distinction between properties of the stabilized mental image and the process of stabilization. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
29.
A cost-effective system for the contactless characterisation of microresonators vibrating in out-of-plane mode is presented. The system provides swept-frequency excitation to the microresonator, detects the mechanical vibrations by a single-point triangulator made by a laser diode and a four-quadrant detector, and exploits synchronous undersampling of the readout signal to derive the frequency response of the microresonator. The system has been prototyped and tested using a piezoelectric bimorph cantilever as the resonator. A displacement resolution of around 100 nm has been obtained in the frequency range of up to some tens of kilohertz. 相似文献
30.
Sumathy Arumuganathar Scott Irvine Jean R. McEwan Suwan N. Jayasinghe 《应用聚合物科学杂志》2008,107(2):1215-1225
In a recent discovery, coaxial electrospinning was explored to encapsulate living organisms within a continuous bio‐polymeric microthread from which active biological scaffolds were fabricated (Townsend‐Nicholson and Jayasinghe, Biomacromolecules 2006, 7, 3364). The cells were demonstrated to have gone through all expected cellular activity without their viability being compromised. These biologically active threads and scaffolds have direct and tremendous applicability from regenerative to therapeutic medicine. Currently these post‐processed cells as composite threads and scaffolds are being investigated in‐depth at a cellular level to establish if the processing methodology has any affect on the cellular make‐up. We now demonstrate a competing non‐electric field driven approach for fabricating composite threads and scaffolds influenced only by a differential pressure. We refer to this novel composite thread to scaffold fabrication methodology as coaxial aerodynamically assisted bio‐threading (CAABT). Our investigations firstly, demonstrate that this technique can process handle living organisms without biologically perturbing them in anyway. Secondly the process is elucidated as possessing the ability to form composite active threads from which biologically viable scaffolds are formed. Finally our study employs florescent activated cell sorting (FACScan), a method by which the cellular dynamics and viability are quantified on control and threaded cellular samples at two prescribed time points. In parallel with FACScan, optical comparison of cellular morphology at three time points within a period of three weeks is carried out to photographically observe any changes in the post‐processed cellular phenotype. Our developmental investigations into this novel aerodynamically assisted threading methodology has unearthed a unique biomicrofabrication approach, which joins cell electrospinning in the cell threading to scaffold fabrication endeavor. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献