全文获取类型
收费全文 | 59993篇 |
免费 | 4271篇 |
国内免费 | 1570篇 |
专业分类
电工技术 | 3707篇 |
综合类 | 5901篇 |
化学工业 | 4096篇 |
金属工艺 | 1896篇 |
机械仪表 | 2276篇 |
建筑科学 | 11732篇 |
矿业工程 | 1585篇 |
能源动力 | 960篇 |
轻工业 | 13650篇 |
水利工程 | 3381篇 |
石油天然气 | 1899篇 |
武器工业 | 225篇 |
无线电 | 3169篇 |
一般工业技术 | 2983篇 |
冶金工业 | 3426篇 |
原子能技术 | 186篇 |
自动化技术 | 4762篇 |
出版年
2024年 | 321篇 |
2023年 | 828篇 |
2022年 | 1364篇 |
2021年 | 1768篇 |
2020年 | 1820篇 |
2019年 | 1483篇 |
2018年 | 1334篇 |
2017年 | 1620篇 |
2016年 | 1717篇 |
2015年 | 1937篇 |
2014年 | 4308篇 |
2013年 | 3354篇 |
2012年 | 4244篇 |
2011年 | 4517篇 |
2010年 | 3559篇 |
2009年 | 3790篇 |
2008年 | 3417篇 |
2007年 | 4055篇 |
2006年 | 3676篇 |
2005年 | 2962篇 |
2004年 | 2596篇 |
2003年 | 2311篇 |
2002年 | 2045篇 |
2001年 | 1485篇 |
2000年 | 1227篇 |
1999年 | 957篇 |
1998年 | 627篇 |
1997年 | 489篇 |
1996年 | 422篇 |
1995年 | 358篇 |
1994年 | 260篇 |
1993年 | 198篇 |
1992年 | 175篇 |
1991年 | 115篇 |
1990年 | 81篇 |
1989年 | 84篇 |
1988年 | 64篇 |
1987年 | 57篇 |
1986年 | 32篇 |
1985年 | 35篇 |
1984年 | 26篇 |
1983年 | 17篇 |
1982年 | 17篇 |
1981年 | 10篇 |
1980年 | 20篇 |
1978年 | 5篇 |
1977年 | 6篇 |
1965年 | 5篇 |
1964年 | 4篇 |
1959年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Anjali Awasthi Satyaveer S. Chauhan Hichem Omrani Ariyo Panahi 《Computers & Industrial Engineering》2011,61(3):637-646
Managing service quality is vital to retain customer satisfaction and augment revenues for any business organization. Often it is difficult to assess service quality due to lack of quantifiable measures and limited data. In this paper, we present a hybrid approach based on SERVQUAL and fuzzy TOPSIS for evaluating service quality of urban transportation systems. The proposed approach consists of three steps. The first step involves development of a SERVQUAL based questionnaire to collect data for measuring transportation service quality. The participants provide linguistic assessments to rate the service quality criteria and the alternatives. In step 2, the linguistic ratings are combined through fuzzy TOPSIS to generate an overall performance score for each alternative. The alternative with the highest score is finally chosen. In step 3, sensitivity analysis is conducted to evaluate the influence of criteria weights on the decision making process.The strength of the proposed approach is its practical applicability and ability to provide solution under partial or lack of quantitative information. An application of the proposed approach for evaluation of service quality of metro in Montreal is provided. 相似文献
992.
Godwin J. Udo 《Computers in human behavior》2011,27(3):1272-1283
Distance learning programs have been dramatically expanding in accordance with demand. Assessment of the quality of e-learning has become a strategic issue, one that is critical to program survival. In this study we propose a modified SERVQUAL instrument for assessing e-learning quality. The instrument consists of five dimensions: Assurance, Empathy, Responsiveness, Reliability, and Website Content. Data analysis from 203 e-learning students shows that four out of these five dimensions (except Reliability) play a significant role in perceived e-learning quality, which in turn affects learners’ satisfaction and future intentions to enroll in online courses. Managerial implications of the major findings are provided. 相似文献
993.
Jianli LiuAuthor Vitae Baoqi ZuoAuthor Vitae Xianyi ZengAuthor Vitae Philippe VromanAuthor Vitae Besoa RabenasoloAuthor Vitae 《Neurocomputing》2011,74(17):2813-2823
This work is dedicated to develop an algorithm for the visual quality recognition of nonwoven materials, in which image analysis and neural network are involved in feature extraction and pattern recognition stage, respectively. During the feature extraction stage, each image is decomposed into four levels using the 9-7 bi-orthogonal wavelet base. Then the wavelet coefficients in each subband are independently modeled by the generalized Gaussian density (GGD) model to calculate the scale and shape parameters with maximum likelihood (ML) estimator as texture features. While for the recognition stage, the robust Bayesian neural network is employed to classify the 625 nonwoven samples into five visual quality grades, i.e., 125 samples for each grade. Finally, we carry out the outlier detection of the training set using the outlier probability and select the most suitable model structure and parameters from 40 Bayesian neural networks using the Occam's razor. When 18 relevant textural features are extracted for each sample based on the GGD model, the average recognition accuracy of the test set arranges from 88% to 98.4% according to the different number of the hidden neurons in the Bayesian neural network. 相似文献
994.
A novel humid electronic nose combined with an electronic tongue for assessing deterioration of wine 总被引:2,自引:0,他引:2
Luis Gil-SánchezAuthor Vitae Juan SotoAuthor Vitae Ramón Martínez-MáñezAuthor Vitae Eduardo Garcia-BreijoAuthor Vitae Javier IbáñezAuthor Vitae Eduard LlobetAuthor Vitae 《Sensors and actuators. A, Physical》2011,171(2):152-158
We report herein the use of a combined system for the analysis of the spoilage of wine when in contact with air. The system consists of a potentiometric electronic tongue and a humid electronic nose. The potentiometric electronic tongue was built with thick-film serigraphic techniques using commercially available resistances and conductors for hybrid electronic circuits; i.e. Ag, Au, Cu, Ru, AgCl, and C. The humid electronic nose was designed in order to detect vapours that emanate from the wine and are apprehended by a moist environment. The humid nose was constructed using a piece of thin cloth sewn, damped with distilled water, forming five hollows of the right size to introduce the electrodes. In this particular case four electrodes were used for the humid electronic nose: a glass electrode, aluminium (Al), graphite and platinum (Pt) wires and an Ag-AgCl reference electrode. The humid electronic nose together with the potentiometric electronic tongue were used for the evaluation of the evolution in the course of time of wine samples. Additionally to the analysis performed by the tongue and nose, the spoilage of the wines was followed via a simple determination of the titratable (total) acidity. 相似文献
995.
基于Web的亚热带水果产品质量安全追溯系统关键技术研究 总被引:5,自引:0,他引:5
徐龙琴 《计算机工程与设计》2011,32(4):1174-1177,1189
为了实现对亚热带水果"从果园到餐桌"全方位的跟踪和追溯,分析了水果产品生产流程并确定了影响其质量的关键点,以产品生产批次作为"身份标识",采用UCC/EAN-128编码方式结合流程编码、RFID和二维码等编码技术进行了追溯编码,并采用任务与角色相结合的权限分配策略,构建了一个多层次多用户权限动态管理的亚热带水果生产加工全过程的质量跟踪与追溯系统,为生产者、质检部门和消费者提供一个集产品生产加工诸环节的信息交流平台,并以网络、语音、短信、触摸屏向公众提供追溯查询和防伪服务,具有应用推广价值。 相似文献
996.
IS researchers have normally assumed that satisfaction is the key factor influencing IS customers’ reuse of services; however, a focus on customer satisfaction does not always guarantee customer retention. We synthesized customer satisfaction and dissatisfaction models from prior service quality research to provide a comprehensive model predicting the behavioral intentions of customers to reuse IS services. Five research hypotheses were empirically tested by using a field study of 263 users of an IS service department. Our findings placed IS service quality in a causal network leading to IS service reuse and highlighted the relative importance that service quality value played in predicting behavioral intention to reuse the service. 相似文献
997.
Pricing schemes for digital content with DRM mechanisms 总被引:1,自引:0,他引:1
In this paper, utilizing game-theoretic model, we examine the impact of collaborative structure, content quality, and network environment on the development of pricing scheme and DRM protection policy of digital content. DRM protection level decreases and pirating activities becomes relatively tolerable as the content provider and platform provider operate collaboratively. Depending on the market structure, higher content quality may strengthen or weaken the adoption of DRM. However, it would seem that, as the network environment becomes more decentralized and uncontrolled, weaker DRM protection should be a better strategy. 相似文献
998.
Increasingly powerful computers and increased emphasis on evidence based decision making are creating a demand for merging
and integrating data from different sources into a single data set. The demand for data is outstripping our ability to ensure
data integrity, and sometimes analysis is performed on data that are not appropriate for the purposes they are used for. Here
we describe problems that arise when data from different sources are merged, and we suggest that one way to add context to
data so that users can make informed decisions about their ontological context is through ontology-based metadata. Examples
of the problem are taken from health data with emphasis on difficulties in standardizing Emergency Room wait times. We describe
eight fields that can be used to capture contextual metadata. These fields are captured using ethnographic methods from users
and database stewards who frequently understand precisely how context and institutional usage have shaped interpretation of
semantic fields. We argue that attaching a portable archive of ontological context to travel with data—based on information
from users and developers—is a means of ensuring that data are integrated and compared in multiple contexts with greater integrity
and more robust results.
相似文献
Nadine SchuurmanEmail: |
999.
John Moses 《Software Quality Journal》2009,17(2):203-213
Most external software quality attributes are conceptually subjective. For example, maintainability is an external software
quality attribute, and it is subjective because interpersonally agreed definitions for the attribute include the phrase ‘the
ease with which maintenance tasks can be performed’. Subjectivity clearly makes measurement of the attributes and validation
of prediction systems for the attributes problematic. In fact, in spite of the definitions, few statistically valid attempts
at determining the predictive capability of prediction systems for external quality attributes have been published. When validations
have been attempted, one approach used is to ask experts to indicate if the values provided by the prediction system informally
agree with the experts’ intuition. These attempts are undertaken without determining, independently of the prediction system,
whether the experts are capable of direct consistent measurement of the attribute. Hence, a statistically valid and unbiased
estimate of the predictive capability of the prediction system cannot be obtained (because the experts’ measurement process
is not independent of the prediction system’s values). In this paper, it is argued that the problem of subjective measurement
of quality attributes should not be ignored if quality is to be introduced into software in a controlled way. Further, it
is argued that direct measurement of quality attributes should be encouraged and that in fact such measurement can be quantified
to establish consistency using an existing approach. However, the approach needs to be made more accessible to promote its
use. In so doing, it would be possible to decide whether consistent independent estimates of the true values of software quality attributes can be assigned and prediction systems for quality attributes developed.
相似文献
John MosesEmail: |
1000.
在光学遥感图像融合方法中,最小二乘法常被用于求解多光谱图像拟合低分辨率全色图像的线性回归系数,但是回归系数常常出现负数,导致其物理意义不明确。针对这种实际情况,提出了基于约束最小二乘的低分辨率全色图像构造方法。通过IKONOS-2全色与多光谱图像的融合实验,结果表明:该方法所求得的回归系数具有明确物理意义,符合实际情况,并且与光谱响应函数法、最小二乘法相比,其融合质量基本保持一致,并且由于该方法不需要先验知识,故其实用性较强。 相似文献