首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   404篇
  免费   7篇
电工技术   3篇
化学工业   63篇
金属工艺   40篇
机械仪表   2篇
建筑科学   9篇
矿业工程   2篇
能源动力   5篇
轻工业   39篇
水利工程   1篇
无线电   8篇
一般工业技术   41篇
冶金工业   146篇
自动化技术   52篇
  2023年   2篇
  2022年   2篇
  2021年   1篇
  2020年   4篇
  2019年   3篇
  2018年   5篇
  2017年   3篇
  2016年   5篇
  2015年   1篇
  2014年   6篇
  2013年   23篇
  2012年   12篇
  2011年   26篇
  2010年   29篇
  2009年   19篇
  2008年   14篇
  2007年   20篇
  2006年   17篇
  2005年   16篇
  2004年   7篇
  2003年   12篇
  2002年   9篇
  2001年   11篇
  2000年   16篇
  1999年   9篇
  1998年   11篇
  1997年   11篇
  1996年   7篇
  1995年   16篇
  1994年   16篇
  1993年   7篇
  1992年   7篇
  1991年   6篇
  1990年   5篇
  1989年   3篇
  1988年   11篇
  1987年   4篇
  1986年   5篇
  1985年   8篇
  1984年   2篇
  1983年   2篇
  1982年   4篇
  1981年   2篇
  1980年   2篇
  1979年   3篇
  1978年   2篇
  1977年   2篇
  1976年   1篇
  1974年   1篇
  1970年   1篇
排序方式: 共有411条查询结果,搜索用时 15 毫秒
71.
This paper demonstrates the feasibility of using phase stepping and a multicore optical fiber to calculate an object's depth profile. An interference pattern is projected by an optical fiber onto the object. The distorted interference pattern containing the object information is captured by a CCD camera and processed using a phase step interferometry method. The phase step method is less computationally intensive compared to two-dimensional Fourier transform profilometry and provides more accuracy when measuring objects of high frequency spatial variations.  相似文献   
72.
This cross-sectional study provides population-referenced data on the restraints used and the extent of incorrect restraint use, among child vehicle passengers aged 0–12 years in NSW, Australia. A multistage stratified cluster sampling plan was used to randomly select vehicles from baby/child health clinics, pre-schools/day care centres, and primary schools across NSW to undergo detailed inspection of restraints used by child occupants within those vehicles. Overall, there were very high restraint usage rates (>99% of sampled children) but fewer than one quarter of children were using the correct size-appropriate restraints. Incorrect use (51.4%) was as common as inappropriate use (51.2%). Incorrect use was highest among users of dedicated child restraint systems (OR 16.0, 95% CI 6.9–36.0), and was more likely among those using size-appropriate restraints than those using inappropriate restraints (OR 1.8 95% CI 1.1–3.2); and among convertible restraints than those designed for a single mode of use (OR 1.5 95% CI 1.2–1.7). As incorrect use substantially reduces the protection from injury that is offered by child restraints, it is important that future strategies to reduce casualties among child occupants target both inappropriate and incorrect use.  相似文献   
73.
Objective: To determine the most effective ways to present human papillomavirus (HPV) vaccine risk and benefit information to mothers in Hispanic, African American, and White communities, to increase mothers’ intentions to vaccinate their daughters against HPV. Design: The study used a 3 × 2 between-subjects factorial design, involving 3 different risk presentation formats (graphical HPV statistics, nongraphical HPV statistics, or no-statistics control) and the presence or absence of rhetorical questions (RQ). Data were collected from a national sample of 471 mothers of girls ages 11–16. Main Outcome Variables: The primary outcome variable was mothers’ intention to vaccinate their daughters against HPV. Secondary outcomes included mothers’ self-reported message comprehension and perceptions of daughters’ vulnerability to HPV infection, infection severity, vaccine efficacy, and obstacles to immunization. Results and Conclusion: Results showed that both risk presentation format and RQs had an overall positive effect on mothers’ intention to vaccinate their daughters. However, the interventions appear to be more effective when used separately than when used in combination. Each of these interventions is brief and could easily be implemented by health care providers as well as in patient health communication literature. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
74.
Water‐soluble single‐walled carbon nanotube‐polyacetylene [SWNT‐PA, SWNT‐P(2EPy‐MeTf)] nanocomposites have been synthesized by using the surface initiated “grafting‐from” method. The FT‐IR spectra confirmed the formation of an amide bond between the functionalized SWNTs and the initiator, 4‐(2‐Aminoethyl) pyridine, to polymerize N‐Methyl‐2‐ethynlypyridinium triflate (2EPy‐MeTf). UV‐vis spectroscopy indicated that the degree of polymerization of P(2EPy‐MeTf) in the SWNT‐polyacetylene composites is 15, based on the Lewis‐Calvin equation. The SWNT‐polyacetylene composites have been characterized by TGA, AFM, and TEM. From TGA analysis, the loading of SWNTs in the SWNT grafted ionic polyacetylenes is estimated to be 22%. AFM and TEM images clearly showed that the nanotube is wrapped with the PA. The SWNT‐polyacetylene composites displayed high water solubility (8 mg/ml). The room temperature electrical conductivity of the doped SWNT‐polyacetylene composites was found to be in the range of 10−3 to 10−4 S/cm, an order of magnitude of increase over neat P(2EPy‐MeTf) and a two order of magnitude increase over Dendrimer‐polyacetylen composites. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers  相似文献   
75.
We demonstrate that oral delivery of self-assembled nanostructured nanoparticles consisting of 5-fluorouracil (5-FU) lipid prodrugs results in a highly effective, target-activated, chemotherapeutic agent, and offers significantly enhanced efficacy over a commercially available alternative that does not self-assemble. The lipid prodrug nanoparticles have been found to significantly slow the growth of a highly aggressive mouse 4T1 breast tumour, and essentially halt the growth of a human MDA-MB-231 breast tumour in mouse xenografts. Systemic toxicity is avoided as prodrug activation requires a three-step, enzymatic conversion to 5-FU, with the third step occurring preferentially at the tumour site. Additionally, differences in the lipid prodrug chemical structure and internal nanostructure of the nanoparticle dictate the enzymatic conversion rate and can be used to control sustained release profiles. Thus, we have developed novel oral nanomedicines that combine sustained release properties with target-selective activation.  相似文献   
76.
Cognitive and sensorimotor predictors of mortality were examined in the Australian Longitudinal Study of Ageing, controlling for demographic and health variables. A stratified random sample of 1,947 males and females aged 70 and older were interviewed, and 1,500 were assessed on measures of health, memory, verbal ability, processing speed, vision, hearing, and grip strength in 1992 and 1994. Analyses of incident rate ratios for mortality over 4- and 6-year periods were conducted using Cox hierarchical regression analyses. Results showed that poor performance on nearly all cognitive variables was associated with mortality, but many of these effects were explained by measures of self-rated health and disease. Significant decline in hearing and cognitive performance also predicted mortality as did incomplete data at Wave 1. Results suggest that poor cognitive performance and cognitive decline in very old adults reflect both biological aging and disease processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
77.
A simple solution-based approach for depositing CIGS (Cu-In-Ga-Se/S) absorber layers is discussed, with an emphasis on film characterization, interfacial properties and integration into photovoltaic devices. The process involves incorporating all metal and chalcogenide components into a single hydrazine-based solution, spin coating a precursor film, and heat treating in an inert atmosphere, to form the desired CIGS film with up to micron-scaled film thickness and grain size. PV devices (glass/Mo/CIGS/CdS/i-ZnO/ITO) employing the spin-coated CIGS and using processing temperatures below 500 °C have yielded power conversion efficiencies of up to 10% (AM 1.5 illumination), without the need for a post-CIGS-deposition treatment in a gaseous Se source or a cyanide-based bath etch. Short-duration low-temperature (T < 200 °C) oxygen treatment of completed devices is shown to have a positive impact on the performance of initially underperforming cells, thereby enabling better performance in devices prepared at temperatures below 500 °C.  相似文献   
78.
79.
80.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号