全文获取类型
收费全文 | 35596篇 |
免费 | 1739篇 |
国内免费 | 119篇 |
专业分类
电工技术 | 475篇 |
综合类 | 235篇 |
化学工业 | 6919篇 |
金属工艺 | 714篇 |
机械仪表 | 773篇 |
建筑科学 | 1249篇 |
矿业工程 | 103篇 |
能源动力 | 1251篇 |
轻工业 | 4942篇 |
水利工程 | 313篇 |
石油天然气 | 184篇 |
武器工业 | 6篇 |
无线电 | 2772篇 |
一般工业技术 | 5343篇 |
冶金工业 | 6563篇 |
原子能技术 | 294篇 |
自动化技术 | 5318篇 |
出版年
2024年 | 63篇 |
2023年 | 201篇 |
2022年 | 587篇 |
2021年 | 1119篇 |
2020年 | 739篇 |
2019年 | 874篇 |
2018年 | 1007篇 |
2017年 | 1030篇 |
2016年 | 1043篇 |
2015年 | 811篇 |
2014年 | 1181篇 |
2013年 | 2035篇 |
2012年 | 1760篇 |
2011年 | 2173篇 |
2010年 | 1569篇 |
2009年 | 1658篇 |
2008年 | 1515篇 |
2007年 | 1326篇 |
2006年 | 1067篇 |
2005年 | 1052篇 |
2004年 | 1101篇 |
2003年 | 955篇 |
2002年 | 932篇 |
2001年 | 766篇 |
2000年 | 625篇 |
1999年 | 590篇 |
1998年 | 2138篇 |
1997年 | 1398篇 |
1996年 | 984篇 |
1995年 | 657篇 |
1994年 | 517篇 |
1993年 | 581篇 |
1992年 | 242篇 |
1991年 | 315篇 |
1990年 | 254篇 |
1989年 | 206篇 |
1988年 | 226篇 |
1987年 | 176篇 |
1986年 | 174篇 |
1985年 | 202篇 |
1984年 | 150篇 |
1983年 | 104篇 |
1982年 | 130篇 |
1981年 | 124篇 |
1980年 | 130篇 |
1979年 | 97篇 |
1978年 | 80篇 |
1977年 | 143篇 |
1976年 | 243篇 |
1975年 | 91篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
91.
A. P. J. Voncken A. F. J. Hammen A. T. A. M. de Waele 《Journal of Low Temperature Physics》1996,102(3-4):335-348
In this paper we describe the effect of the vicinity of a liquid3He-vacuum interface on the behavior of a vibrating wire viscometer. It was found that in the fluid near the liquid interface the quality factor is lower than in the bulk liquid. We further report on the observation of a doubling of the resonance peak of the wire in a saturated3He-4He mixture. The frequencies and amplitudes of the two peaks strongly depend on the distance between the phase boundary and the vibrating wire; the temperature and the velocity of the phase boundary have no significant influence on the peak frequencies. The observed peak doubling is attributed to the coupling of the vibrating wire with a standing second-sound wave in the dilute phase where the volume of the dilute phase can be regarded as a resonating cavity for second sound. 相似文献
92.
93.
94.
Maribel Plascencia‐Jatomea Miguel A Olvera‐Novoa Jos Luis Arredondo‐Figueroa George M Hall Keiko Shirai 《Journal of the science of food and agriculture》2002,82(7):753-759
This study provides information on the use of shrimp head silage protein hydrolysate (SPH) as an alternative protein source for tilapia feeding. Six diets (28% protein, 12% lipid) were prepared where fishmeal protein was replaced at levels of 0 (control), 10, 15, 20, 25 and 30% with the hydrolysate. The diets were supplied to Nile tilapia fry (338 mg initial weight) stocked in plastic recirculating 20 l tanks (10 animals per tank), with three replicates per treatment. After an 8 week experimental period, fish fed the diets containing 10 and 15% SPH showed significantly better performance in terms of final body weight, weight gain (%), mean daily weight gain (mg day?1), specific growth ratio and feed conversion ratio than those fed the control diet (fishmeal as protein source) and higher‐SPH diets. It is concluded that shrimp head hydrolysate is a promising alternative protein source for tilapia feeding, improving growth ratio at dietary inclusion levels as high as 15%. In addition, the diets with added shrimp silage protein were well accepted by the fish, which avidly consumed the feed during the experiment. © 2002 Society of Chemical Industry 相似文献
95.
Eileen Souza 《Information Systems Management》1991,8(1):17-24
Computer-aided software engineering ( CASE) is changing the way IS professionals develop information systems. This article demonstrates how traditional systems development methods are changing with automation, describes a new six-phase software development methodology— the CASE life cycle— designed to maximize the effective use of CASE technologies, and discusses how, organizations can make the transition to this new methodology. 相似文献
96.
Classical parameter-extraction programs rely on the minimisation of the relative current deviation. However, since, especially for analogue applications, the slope of the IDS/VDS curve in the saturation region is at least equally important, a new fit strategy has been developed. This new fit strategy extracts a parameter set which optimises the current residual as well as the slope residual at every point. 相似文献
97.
From visual data exploration to visual data mining: a survey 总被引:8,自引:0,他引:8
Ferreira de Oliveira M.C. Levkowitz H. 《IEEE transactions on visualization and computer graphics》2003,9(3):378-394
We survey work on the different uses of graphical mapping and interaction techniques for visual data mining of large data sets represented as table data. Basic terminology related to data mining, data sets, and visualization is introduced. Previous work on information visualization is reviewed in light of different categorizations of techniques and systems. The role of interaction techniques is discussed, in addition to work addressing the question of selecting and evaluating visualization techniques. We review some representative work on the use of information visualization techniques in the context of mining data. This includes both visual data exploration and visually expressing the outcome of specific mining algorithms. We also review recent innovative approaches that attempt to integrate visualization into the DM/KDD process, using it to enhance user interaction and comprehension. 相似文献
98.
Norris Fran H.; Murphy Arthur D.; Baker Charlene K.; Perilla Julia L.; Rodriguez Francisco Gutiérrez; Rodriguez José de Jesús Gutiérrez 《Canadian Metallurgical Quarterly》2003,112(4):646
Prevalence rates of trauma and posttraumatic stress disorder (PTSD) were estimated from a probability sample of 2,509 adults from 4 cities in Mexico. PTSD was assessed according to Diagnostic and Statistical Manual of Mental Disorders (American Psychiatric Association, 1994) criteria using the Composite International Diagnostic Interview (CIDI; WHO, 1997). Lifetime prevalence of exposure and PTSD were 76% and 11.2%, respectively. Risk for PTSD was highest in Oaxaca (the poorest city), persons of lower socioeconomic status, and women. Conditional risk for PTSD was highest following sexual violence, but nonsexual violence and traumatic bereavement had greater overall impact because of their frequency. Of lifetime cases, 62% became chronic; only 42% received medical or professional care. The research demonstrates the importance of expanding the epidemiologic research base on trauma to include developing countries around the world. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
99.
The thermal and mechanical properties and the morphologies of blends of poly(propylene) (PP) and an ethylene–(vinyl alcohol) copolymer (EVOH) and of blends of PP/EVOH/ethylene–(methacrylic acid)–Zn2+ ionomer were studied to establish the influence of the ionomer addition on the compatibilization of PP/EVOH blends and on their properties. The oxygen transmission rate (O2TR) values of the blends were measured as well. PP and EVOH are initially incompatible as was determined by tensile tests and scanning electronic microscopy. Addition of the ionomer Zn2+ led to good compatibility and mechanical behaviour was improved in all blends. The mechanical properties on extruded films were studied for 90/10 and 80/20 w/w PP/EVOH blends compatibilized with 10 % of ionomer Zn2+. These experiments have shown that the tensile properties are better than in the injection‐moulded samples. The stretching during the extrusion improved the compatibility of the blends, diminishing the size of EVOH domains and enhancing their distribution in the PP matrix. As was to be expected, the EVOH improved the oxygen permeation of the films, even in compatibilized blends. Copyright © 2004 Society of Chemical Industry 相似文献
100.
Two types of composite were prepared, based on a thermoplastic polymer, polyvinylidene fluoride (PVDF), and an elastomer, ethylene‐propylene‐diene terpolymer (EPDM), respectively. We obtained both series by addition of an inorganic proton‐conducting antimonic acid derivative (HSb) and polystyrene crosslinked with a small percentage of divinylbenzene (PS‐co‐DVB). From these composites, membranes were obtained and subjected to a heterogeneous‐phase sulfonation reaction with chlorosulfonic acid. All experimental materials were characterized from a morphological and electrical point of view, by means of techniques such as differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), non‐isothermal crystallization and complex impedance analysis. Copyright © 2005 Society of Chemical Industry 相似文献