全文获取类型
收费全文 | 231507篇 |
免费 | 26565篇 |
国内免费 | 17801篇 |
专业分类
电工技术 | 16694篇 |
技术理论 | 18篇 |
综合类 | 26007篇 |
化学工业 | 27461篇 |
金属工艺 | 6090篇 |
机械仪表 | 12031篇 |
建筑科学 | 28037篇 |
矿业工程 | 10065篇 |
能源动力 | 11836篇 |
轻工业 | 11099篇 |
水利工程 | 26344篇 |
石油天然气 | 15265篇 |
武器工业 | 2484篇 |
无线电 | 12933篇 |
一般工业技术 | 17024篇 |
冶金工业 | 8869篇 |
原子能技术 | 2665篇 |
自动化技术 | 40951篇 |
出版年
2024年 | 1102篇 |
2023年 | 3302篇 |
2022年 | 6336篇 |
2021年 | 7468篇 |
2020年 | 8073篇 |
2019年 | 6840篇 |
2018年 | 6648篇 |
2017年 | 8051篇 |
2016年 | 9322篇 |
2015年 | 9440篇 |
2014年 | 14408篇 |
2013年 | 15232篇 |
2012年 | 17086篇 |
2011年 | 18036篇 |
2010年 | 13854篇 |
2009年 | 14328篇 |
2008年 | 13621篇 |
2007年 | 16230篇 |
2006年 | 14495篇 |
2005年 | 12862篇 |
2004年 | 10185篇 |
2003年 | 9075篇 |
2002年 | 7443篇 |
2001年 | 6067篇 |
2000年 | 5155篇 |
1999年 | 3954篇 |
1998年 | 3157篇 |
1997年 | 2569篇 |
1996年 | 2257篇 |
1995年 | 1984篇 |
1994年 | 1589篇 |
1993年 | 1156篇 |
1992年 | 927篇 |
1991年 | 730篇 |
1990年 | 571篇 |
1989年 | 521篇 |
1988年 | 341篇 |
1987年 | 269篇 |
1986年 | 210篇 |
1985年 | 201篇 |
1984年 | 202篇 |
1983年 | 109篇 |
1982年 | 101篇 |
1981年 | 50篇 |
1980年 | 73篇 |
1979年 | 66篇 |
1978年 | 19篇 |
1965年 | 17篇 |
1959年 | 22篇 |
1951年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
31.
Clip-art image segmentation is widely used as an essential step to solve many vision problems such as colorization and vectorization. Many of these applications not only demand accurate segmentation results, but also have little tolerance for time cost, which leads to the main challenge of this kind of segmentation. However, most existing segmentation techniques are found not sufficient for this purpose due to either their high computation cost or low accuracy. To address such issues, we propose a novel segmentation approach, ECISER, which is well-suited in this context. The basic idea of ECISER is to take advantage of the particular nature of cartoon images and connect image segmentation with aliased rasterization. Based on such relationship, a clip-art image can be quickly segmented into regions by re-rasterization of the original image and several other computationally efficient techniques developed in this paper. Experimental results show that our method achieves dramatic computational speedups over the current state-of-the-art approaches, while preserving almost the same quality of results. 相似文献
32.
Determining the factors influencing students’ intention to use m-learning in Jordan higher education
M-learning is characterized as a powerful element of learning and education for facilitating the learning experiences. With enhanced and rapid advancements in technologies of ICTs (Information and Communication Technologies) and mobile, numerous innovative services and applications are being developed. Therefore, it becomes significant to investigate the factors influencing the intentions of m-learning to be used among the students of higher education institution. This study examines the “Technology Acceptance Model” (TAM), “Theory of Reasoned Action” (TRA) and “Unified Theory of Acceptance and Use of Technology” (UTAUT). The study is based on a survey being conducted across diverse groups of students, belonging to different communities and universities. The survey questionnaire was utilized for collecting the relevant data from 250 respondents. The results analyzed yields the impact that the proposed model of m-learning is comprehensive to study in the institutions of higher education. 相似文献
33.
An engineered variant of the yeast Pichia pastoris was used to produce the potential malaria vaccine D1M1. This paper describes the implementation of an expanded bed adsorption chromatography step into a sequential cultivation process of the yeast in order to link protein expression, cell release, and product capture of the secreted protein in a fully automated plant. The process is operated with a semi-continuous strategy for an integrated production. Process improvements have been achieved using design of experiments. Resulting purities of product achieved up to 87% with recoveries of 51% in a single downstream operation. Furthermore, a multivariate analysis of historical batch data was used to develop a golden batch model for process monitoring. 相似文献
34.
35.
The eutectic 80Au/20Sn solder alloy is widely used in high power electronics and optoelectronics packaging. In this study, low cycle fatigue behavior of a eutectic 80Au/20Sn solder alloy is reported. The 80Au/20Sn solder shows a quasi-static fracture characteristic at high strain rates, and then gradually transforms from a transgranular fracture (dominated by fatigue damage) to intergranular fracture (dominated by creep damage) at low strain rates with increasing temperature. Coffin-Manson and Morrow models are proposed to evaluate the low cycle fatigue behavior of the 80Au/20Sn solder. Besides, the 80Au/20Sn solder has enhanced fatigue resistance compared to the 63Sn/37Pb solder. 相似文献
36.
Physical Stability of Octenyl Succinate–Modified Polysaccharides and Whey Proteins for Potential Use as Bioactive Carriers in Food Systems 下载免费PDF全文
The high cost and potential toxicity of biodegradable polymers like poly(lactic‐co‐glycolic)acid (PLGA) has increased the interest in natural and modified biopolymers as bioactive carriers. This study characterized the physical stability (water sorption and state transition behavior) of selected starch and proteins: octenyl succinate–modified depolymerized waxy corn starch (DWxCn), waxy rice starch (DWxRc), phytoglycogen, whey protein concentrate (80%, WPC), whey protein isolate (WPI), and α‐lactalbumin (α‐L) to determine their potential as carriers of bioactive compounds under different environmental conditions. After enzyme modification and particle size characterization, glass transition temperature and moisture isotherms were used to characterize the systems. DWxCn and DWxRc had increased water sorption compared to native starch. The level of octenyl succinate anhydrate (OSA) modification (3% and 7%) did not reduce the water sorption of the DWxCn and phytoglycogen samples. The Guggenheim–Andersen–de Boer model indicated that native waxy corn had significantly (P < 0.05) higher water monolayer capacity followed by 3%‐OSA‐modified DWxCn, WPI, 3%‐OSA‐modified DWxRc, α‐L, and native phytoglycogen. WPC had significantly lower water monolayer capacity. All Tg values matched with the solid‐like appearance of the biopolymers. Native polysaccharides and whey proteins had higher glass transition temperature (Tg) values. On the other hand, depolymerized waxy starches at 7%‐OSA modification had a “melted” appearance when exposed to environments with high relative humidity (above 70%) after 10 days at 23 °C. The use of depolymerized and OSA‐modified polysaccharides blended with proteins created more stable blends of biopolymers. Hence, this biopolymer would be suitable for materials exposed to high humidity environments in food applications. 相似文献
37.
Large lectures are the predominant way of teaching first-year students at universities in Norway. However, this forum for education is seldom discussed as a context for a formative feedback practice. The purpose of this sequential mixed methods study was to address whether and how a student-response system can open for a formative feedback practice in lectures and thereby support students' ability to monitor their own learning, as well as supply insight into how students engage with the feedback in their course work. The context for the study was large lectures (150–200 students) in a qualitative method course for first-year psychology students. Findings from the survey (n = 149) showed a positive correlation between the extent to which students report that they use clickers to monitor their own learning, and the extent to which they report that they used the feedback in their own course work. However, findings indicate that students valued the process of monitoring their own learning during the lectures to a greater extent than they actually used the feedback in their course work. Findings from interviews (n = 6) illustrated various ways students applied feedback in their course work. 相似文献
38.
A double optimal projection method that involves projections for intra-cluster and inter-cluster dimensionality reduction are proposed for video fingerprinting. The video is initially set as a graph with frames as its vertices in a high-dimensional space. A similarity measure that can compute the weights of the edges is then proposed. Subsequently, the video frames are partitioned into different clusters based on the graph model. Double optimal projection is used to explore the optimal mapping points in a low-dimensional space to reduce the video dimensions. The statistics and geometrical fingerprints are generated to determine whether a query video is copied from one of the videos in the database. During matching, the video can be roughly matched by utilizing the statistics fingerprint. Further matching is thereafter performed in the corresponding group using geometrical fingerprints. Experimental results show the good performance of the proposed video fingerprinting method in robustness and discrimination. 相似文献
39.
为解决21000工作面采空区及顶板涌水问题,根据工作面出水点的不同情况,采取了集水器导水、老塘设挡水堰截水、挖排水沟疏水等多项治水措施,经统计排水量达33~42m3/h,有效控制了水情,确保了工作面正常生产。 相似文献
40.
《Food Control》2015
The aim of this study was to evaluate the dietary exposure to fumonisin B1 (FB1) through determination of residual FB1 in hair and corn products consumed by 56 volunteers from Pirassununga and Erval Velho, Brazil. Data from FB1 analyses in corn products and a Food Frequency Questionnaire (FFQ) were used for estimating the mean probable daily intake (PDIM) for FB1. FB1 was detected in 4 human hair samples (7.2%), at a mean level of 21.3 ± 12.1 ng g−1. The mean FB1 level found in corn products was 360.4 ± 555.1 μg kg−1. The PDIM value of FB1 in volunteers was 159 ± 47 ng kg−1 body weight day−1 which represents 7.9% of the provisional maximum tolerable daily intake (PMTDI) recommended for fumonisins. The FB1 levels found in human hair samples from each volunteer were associated with their individual PDI of FB1, indicating that exposure to FB1 in the sample studied do not represent a health concern. This is the first report on the incidence of FB1 in individual human hair in Brazil. 相似文献