全文获取类型
收费全文 | 1557篇 |
免费 | 34篇 |
学科分类
工业技术 | 1591篇 |
出版年
2022年 | 8篇 |
2021年 | 9篇 |
2020年 | 9篇 |
2019年 | 11篇 |
2018年 | 17篇 |
2017年 | 12篇 |
2016年 | 19篇 |
2015年 | 26篇 |
2014年 | 29篇 |
2013年 | 91篇 |
2012年 | 46篇 |
2011年 | 71篇 |
2010年 | 50篇 |
2009年 | 75篇 |
2008年 | 57篇 |
2007年 | 64篇 |
2006年 | 72篇 |
2005年 | 67篇 |
2004年 | 65篇 |
2003年 | 48篇 |
2002年 | 54篇 |
2001年 | 46篇 |
2000年 | 34篇 |
1999年 | 33篇 |
1998年 | 45篇 |
1997年 | 43篇 |
1996年 | 42篇 |
1995年 | 28篇 |
1994年 | 30篇 |
1993年 | 29篇 |
1992年 | 31篇 |
1991年 | 12篇 |
1990年 | 28篇 |
1989年 | 12篇 |
1988年 | 10篇 |
1987年 | 15篇 |
1986年 | 18篇 |
1985年 | 24篇 |
1984年 | 25篇 |
1983年 | 22篇 |
1982年 | 16篇 |
1981年 | 13篇 |
1980年 | 12篇 |
1979年 | 15篇 |
1978年 | 11篇 |
1977年 | 13篇 |
1976年 | 23篇 |
1975年 | 10篇 |
1974年 | 10篇 |
1973年 | 11篇 |
排序方式: 共有1591条查询结果,搜索用时 31 毫秒
81.
Terry von Bibra 《e & i Elektrotechnik und Informationstechnik》2002,119(12):a4-a5
AktuellAktuelle Studie
Mobilfunktrends in ?sterreich 相似文献82.
Lansdown TC 《Accident; analysis and prevention》2002,34(5):655-662
This paper reports a study in which visual allocation and verbal reports were recorded to determine individual differences in drivers conducting in-vehicle tasks. Participants drove a simulated route whilst conducting pre-defined tasks using the in-vehicle entertainment system. Tasks of varying complexity were presented to the participants. Licensed (experienced) drivers made significantly more verbal reports relating to road signs and markings, vehicles, scenery in general and vehicle operations; than did unlicensed (novices). No significant difference was found between expert and novice drivers when reporting in-car entertainment system related utterances. Surprising gender differences were also found. Males drove faster, with greater variance, and made more utterances in identified categories. Females were found to make significantly less verbal reports during secondary task performance. The difference in results obtained between expert and novices may imply that novices need to use their attention capacity to focus on the skill of driving, whereas experts through experience, have automated this skill and can use their attention capacity to more effectively during primary tasks. Results suggest that expert drivers are not necessarily experts at undertaking secondary tasks. 相似文献
83.
A computationally fast method to determine values and their uncertainty for particulate system volume median diameter, volume fraction, and size distribution width is presented. These properties cannot be obtained for submicrometer particulate by diffraction-based methods. The technique relies on a least-mean-squares method applied over a prespecified size range and distribution width. Prespecifying the range significantly reduces the number of calculations required to determine the particulate parameters from experimental data, allowing the practical evaluation of large data sets. The solution method that was developed has significant advantages over ratio-style calculations that are more commonly performed, the primary of which is a simple method to determine errors in the measurement parameters. We evaluated the predicted performance for a specific experimental system for various levels of noise, with monodisperse and log-normal distributions, by analyzing synthetic data with the algorithm. Results were a quantitative statement of system accuracy. In addition, synthetic log-normal data evaluated with monodisperse models revealed significant and systematic errors in the predicted volume median diameter. These errors indicate that, in general, systems with a significant size distribution width must be analyzed with a model that includes this size distribution. Finally, calibrated polystyrene spheres were measured with an experimental system that used four simultaneous scattering measurements, and all diameters were within the reported uncertainty. 相似文献
84.
Lin Ming-Tzer El-Deiry Paul Chromik Richard R. Barbosa Nicholas Brown Walter L. Delph Terry J. Vinci Richard P. 《Microsystem Technologies》2006,12(10):1045-1051
A specially designed microtensile apparatus capable of carrying out a series of tests on microscale thin films for microelectromechanical system (MEMS) applications at room temperature and at temperature up to 400°C has been developed and tested, and is described here. Several MEMS-applicable thin films were measured with it, including thermally grown silicon dioxide, gold, and gold–vanadium. The silicon dioxide was tested at room temperature. Gold and gold–vanadium films were tested at room temperature and at 200 and 400°C. Examples of these results are presented.
相似文献85.
Kate Sanders Sally Fincher Dennis Bouvier Gary Lewandowski Briana Morrison Laurie Murphy Marian Petre Brad Richards Josh Tenenberg Lynda Thomas Richard Anderson Ruth Anderson Sue Fitzgerald Alicia Gutschow Susan Haller Raymond Lister Renée McCauley John McTaggart Christine Prasad Terry Scott Dermot Shinners-Kennedy Suzanne Westbrook Carol Zander 《Expert Systems》2005,22(3):121-128
Abstract: This paper presents a case study of the use of a repeated single‐criterion card sort with an unusually large, diverse participant group. The study, whose goal was to elicit novice programmers' knowledge of programming concepts, involved over 20 researchers from four continents and 276 participants drawn from 20 different institutions. In this paper we present the design of the study and the unexpected result that there were few discernible systematic differences in the population. The study was one of the activities of the National Science Foundation funded Bootstrapping Research in Computer Science Education project (2003). 相似文献
86.
The value of information technology (IT) to modern organizations is almost undeniable. However, the determination of that
value has been elusive in research and practice. We used a process-oriented research model developed using two streams of
IT research to examine the value of IT in business organizations. One stream is characterized by examining how IT and non-IT
variables affect other so-called IT success variables. The second stream is commonly referred to as IT business value, defined
as the contribution of IT to firm performance. The resulting research model is referred to in our paper as the IT business
success model. Data was collected from 225 top IS executives in fairly large organizations to empirically examine several
hypotheses derived from theory concerning the causal nature of the IT business success model. A set of measures for the IT
business success model was developed through an intense investigation of the IT literature. The measures were tested for validity
and reliability using confirmatory factor analysis. The hypotheses that resulted from past research and conceptually illustrated
in the research model were assessed using structural equation analysis. The implications of these findings and the limitations
of the study are discussed in an effort to contribute to building a process-oriented theory base for IT business success at
the organizational level of analysis. 相似文献
87.
The collection and reporting of communicable disease information has long been a problem for public health officials. In April 1998, the New Jersey Institute of Technology (NJIT), under contract to the New Jersey Department of Health and Senior Services (DHSS), began work on a "Electronic Laboratory Surveillance System" (ELS) to gather and report such data. The aim of ELS was to determine the extent/spread of problems and minimize consequences through rapid reporting and dissemination of critical information. ELS was completely redesigned to be more user friendly and incorporate new direct-access functions to enable better follow-up of communicable disease reports. This article looks at the evolution of the ELS from a limited system to one that can play a critical role in identifying and linking bioterrorism events 相似文献
88.
Ab initio calculations have been performed to determine the energetics of oxygen atoms adsorbed onto graphene planes and the possible reaction path extracting carbon atoms in the form of carbon monoxide. From the energetics it is confirmed that this reaction path will not significantly contribute to the gasification of well ordered carbonaceous chars. Modelling results which explore this limit are presented. 相似文献
89.
JA Beatty JJ Callanan A Terry O Jarrett JC Neil 《Canadian Metallurgical Quarterly》1998,72(1):767-771
We describe the histopathological, immunohistochemical, and molecular characterization of a lymphoma arising in a 7-year-old cat following experimental infection with feline immunodeficiency virus (FIV). The tumor was high grade and of B-cell lineage. The transformed cell had an immature phenotype (CD79a+, CD79b-, CD21-, immunoglobulin heavy and light chain negative), confirmed by antigen receptor gene analysis, which showed germ line configuration. Single-copy, clonally integrated FIV provirus was detected in tumor genomic DNA. FIV p24 antigen was not detected in tumor cells by immunostaining. This study provides the first evidence that the feline lentivirus may play a direct role in cell transformation under certain circumstances. 相似文献
90.
L. E. L. Rasmussen Terry D. Lee G. Doyle Daves Jr. Michael J. Schmidt 《Journal of chemical ecology》1993,19(10):2115-2128
In their natural ecosystems, the sexes of Asian elephants,Elephas maximus, live separately. For several weeks prior to ovulation, the urine and cervical mucus of female Asian elephants contain extractable chemical agents of low volatility that elicit a high frequency of flehmen responses from bull elephants as an integral part of mating. Subsequent to flehmen responses, male sexual arousal occurs and, if the female is available, mating results. During the course of our project to determine the agent(s) and describe the responses associated with female to male sexual communication, we have identified an unusual compound. This compound, apparently the sole component of the active fraction, was identified by mass, proton nuclear magnetic resonance, ultraviolet/visible, and infrared spectrometries as indolo-[2,1-b] quinazoline-6,12-dione (tryptanthrine). Exhaustive and repetitive bioassays established that pure authentic (synthetic) tryptanthrine was not the compound responsible for the bioresponse. Rather a coeluting minor component, also of low volatility, elicited the male bioresponse. 相似文献