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   1297篇
  免费   103篇
电工技术   4篇
综合类   4篇
化学工业   332篇
金属工艺   4篇
机械仪表   18篇
建筑科学   57篇
矿业工程   4篇
能源动力   17篇
轻工业   171篇
水利工程   20篇
石油天然气   2篇
武器工业   1篇
无线电   87篇
一般工业技术   182篇
冶金工业   345篇
原子能技术   1篇
自动化技术   151篇
  2023年   15篇
  2022年   56篇
  2021年   73篇
  2020年   28篇
  2019年   35篇
  2018年   37篇
  2017年   31篇
  2016年   56篇
  2015年   42篇
  2014年   55篇
  2013年   67篇
  2012年   66篇
  2011年   111篇
  2010年   92篇
  2009年   74篇
  2008年   70篇
  2007年   84篇
  2006年   48篇
  2005年   52篇
  2004年   50篇
  2003年   27篇
  2002年   26篇
  2001年   20篇
  2000年   18篇
  1999年   13篇
  1998年   12篇
  1997年   18篇
  1996年   12篇
  1995年   13篇
  1994年   12篇
  1993年   9篇
  1992年   5篇
  1991年   2篇
  1990年   5篇
  1989年   6篇
  1988年   9篇
  1987年   8篇
  1986年   6篇
  1985年   5篇
  1984年   4篇
  1983年   6篇
  1982年   2篇
  1981年   3篇
  1979年   3篇
  1975年   4篇
  1973年   2篇
  1964年   1篇
  1961年   1篇
  1960年   1篇
  1958年   1篇
排序方式: 共有1400条查询结果,搜索用时 15 毫秒
31.
Bone in diabetes mellitus is characterized by an altered microarchitecture caused by abnormal metabolism of bone cells. Together with diabetic neuropathy, this is associated with serious complications including impaired bone healing culminating in complicated fractures and dislocations, especially in the lower extremities, so-called Charcot neuroarthropathy (CN). The underlying mechanisms are not yet fully understood, and treatment of CN is challenging. Several in vitro and in vivo investigations have suggested positive effects on bone regeneration by modifying biomaterials with sulfated glycosaminoglycans (sGAG). Recent findings described a beneficial effect of sGAG for bone healing in diabetic animal models compared to healthy animals. We therefore aimed at studying the effects of low- and high-sulfated hyaluronan derivatives on osteoclast markers as well as gene expression patterns of osteoclasts and osteoblasts from patients with diabetic CN compared to non-diabetic patients with arthritis at the foot and ankle. Exposure to sulfated hyaluronan (sHA) derivatives reduced the exaggerated calcium phosphate resorption as well as the expression of genes associated with bone resorption in both groups, but more pronounced in patients with CN. Moreover, sHA derivatives reduced the release of pro-inflammatory cytokines in osteoclasts of patients with CN. The effects of sHA on osteoblasts differed only marginally between patients with CN and non-diabetic patients with arthritis. These results suggest balancing effects of sHA on osteoclastic bone resorption parameters in diabetes.  相似文献   
32.
High-risk human papillomaviruses (HPV) are important agents, responsible for a large percentage of the 745,000 cases of head and neck squamous cell carcinomas (HNSCC), which were identified worldwide in 2020. In addition to being virally induced, tobacco and heavy alcohol consumption are believed to cause DNA damage contributing to the high number of HNSCC cases. Gene expression and DNA methylation differ between HNSCC based on HPV status. We used publicly available gene expression and DNA methylation profiles from the Cancer Genome Atlas and compared HPV positive and HPV negative HNSCC groups. We used differential gene expression analysis, differential methylation analysis, and a combination of these two analyses to identify the differences. Differential expression analysis identified 1854 differentially expressed genes, including PCNA, TNFRSF14, TRAF1, TRAF2, BCL2, and BIRC3. SYCP2 was identified as one of the top deregulated genes in the differential methylation analysis and in the combined differential expression and methylation analyses. Additionally, pathway and ontology analyses identified the extracellular matrix and receptor interaction pathway as the most altered between HPV negative and HPV positive HNSCC groups. Combining gene expression and DNA methylation can help in elucidating the genes involved in HPV positive HNSCC tumorigenesis, such as SYCP2 and TAF7L.  相似文献   
33.
In object substitution masking (OSM) a sparse, temporally trailing 4-dot mask impairs target identification, even though it has different contours from, and does not spatially overlap with the target. Here, we demonstrate a previously unknown characteristic of OSM: Observers show reduced masking at prolonged (e.g., 640 ms) relative to intermediate mask durations (e.g., 240 ms). We propose that with prolonged exposure, the mask's visual representation is consolidated, which allows processing of the lingering target icon to be reinitiated, thereby improving performance. Our findings suggest that when the visual system is confronted with 2 temporally contiguous stimuli, although one may initially gain access to consciousness above the other, the “losing” stimulus is not irreversibly lost to awareness. (PsycINFO Database Record (c) 2011 APA, all rights reserved)  相似文献   
34.
35.
36.
37.
Nitrogenated porous carbon materials, made by coating the pore surface with nitrogen functional groups from the pyrolysis of hexamine, were characterized and tested for supercapacitor applications. From X-ray photoelectron spectroscopy, the nitrogen content of the nitrogenated carbon sample was found to be 14?wt%. Electrochemical properties from potentiostatic and galvanostatic measurements, and open circuit voltage (OCV) were used to evaluate the effect of nitrogen in porous carbon electrodes. The nitrogenated carbon exhibits pseudocapacitive behavior and an increase in capacitance that is almost double that of plain porous carbon. The cyclic stability is also improved, as the sample retains its high capacitance even after extensive cycling. Also, the nitrogenated carbon shows battery-like characteristics with an initial OCV of ca. 0.4?V, and an OCV of ca. 0.3?V after cycling.  相似文献   
38.
In the field of humidity quantities, the first CIPM key comparison, CCT-K6 is at its end. The corresponding European regional key comparison, EUROMET.T-K6, was completed in early 2008, about 4?years after the starting initial measurements in the project. In total, 24 NMIs from different countries took part in the comparison. This number includes 22 EURAMET countries, and Russia and South Africa. The comparison covered the dew-point temperature range from ?50?°C to +20?°C. It was carried out in three parallel loops, each with two chilled mirror hygrometers as transfer standards in each loop. The comparison scheme was designed to ensure high quality results with evenly spread workload for the participants. It is shown that the standard uncertainty due to the long-term instability was smaller than 0.008?°C in all loops. The standard uncertainties due to links between the loops were found to be smaller than 0.025?°C at ?50?°C and 0.010?°C elsewhere. Conclusions on the equivalence of the dew-point temperature standards are drawn on the basis of calculated bilateral degrees of equivalence and deviations from the EURAMET comparison reference values (ERV). Taking into account 16 different primary dew-point realizations and 8 secondary realizations, the results demonstrate the equivalence of a large number of laboratories at an uncertainty level that is better than achieved in other multilateral comparisons so far in the humidity field.  相似文献   
39.
During the second half of the 20th century several American multidisciplinary social science ?disaster research groups“ conducted numerous field studies after earthquakes, factory explosions and “racial riots”, both inside and outside of the United States. Their aim was to investigate the reactions and behavior of individuals, organizations and communities to disasters. All of these groups were either promoted or at least partly founded by different branches of the US military. This article will analyze the groups’ studies and findings on the question of disasters’ psychological effects. The main focus will be on the stance the scientists took on the diagnosis of psychological trauma—especially Post Traumatic Stress Disorder (PTSD)—and the post disaster therapeutic interventions that became widespread in the 1970s and early 1980s. The disaster researchers questioned the need for, as well as the effectiveness and efficiency of “disaster mental health”. At the same time they advocated early ideas of resilience, which later became one of the most important concepts in disaster management and beyond.  相似文献   
40.
The purpose of this study was to investigate the influence of exposure to others’ drink driving during adolescence on self-reported driving under the influence (DUI) of alcohol in young adulthood. Data were drawn from 1956 participants with a driving license enrolled in the International Youth Development Study from Victoria, Australia. During 2003 and 2004, adolescents in Grades 7, 9 and 10 (aged 12–17) completed questionnaires examining whether they had ridden in a vehicle with a driver who had been drinking, as well as other demographic, individual, peer and family risk factors for DUI. In 2010, the same participants (aged 18–24) then reported on their own DUI behaviour. 18% of young adults with a driving license reported DUI in the past 12 months. Exposure to others’ drink driving during adolescence was associated with an increased likelihood of DUI as a young adult (OR = 2.13, 95% CI 1.68–2.69). This association remained after accounting for the effects of other potential confounding factors from the individual, peer and family domains (OR = 1.62, 95% CI 1.23–2.13). Observing the drink driving behaviours of others during adolescence may increase the likelihood of DUI as a young adult. Strategies to reduce youth exposure to drink driving are warranted.  相似文献   
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