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   4269篇
  免费   186篇
  国内免费   2篇
电工技术   37篇
综合类   6篇
化学工业   943篇
金属工艺   39篇
机械仪表   74篇
建筑科学   341篇
矿业工程   12篇
能源动力   124篇
轻工业   466篇
水利工程   46篇
石油天然气   12篇
武器工业   1篇
无线电   274篇
一般工业技术   679篇
冶金工业   499篇
原子能技术   19篇
自动化技术   885篇
  2023年   28篇
  2022年   37篇
  2021年   62篇
  2020年   53篇
  2019年   76篇
  2018年   92篇
  2017年   87篇
  2016年   109篇
  2015年   72篇
  2014年   141篇
  2013年   309篇
  2012年   192篇
  2011年   291篇
  2010年   212篇
  2009年   211篇
  2008年   221篇
  2007年   225篇
  2006年   177篇
  2005年   173篇
  2004年   132篇
  2003年   105篇
  2002年   116篇
  2001年   67篇
  2000年   78篇
  1999年   81篇
  1998年   82篇
  1997年   73篇
  1996年   86篇
  1995年   54篇
  1994年   53篇
  1993年   51篇
  1992年   47篇
  1991年   35篇
  1990年   35篇
  1989年   43篇
  1988年   35篇
  1987年   40篇
  1986年   36篇
  1985年   40篇
  1984年   55篇
  1983年   43篇
  1982年   39篇
  1981年   35篇
  1980年   37篇
  1979年   23篇
  1978年   27篇
  1977年   23篇
  1976年   29篇
  1975年   25篇
  1973年   13篇
排序方式: 共有4457条查询结果,搜索用时 15 毫秒
991.
Increased hemodialysis frequency can make fluid overload easier to treat, although most patients are still treated thrice weekly. Chronic fluid overload is associated with left ventricular hypertrophy and elevated serum cardiac biomarkers, recognized as mortality risk factors. Serum cardiac troponin T (cTnT), N‐terminal prohormone brain natriuretic peptide (NT‐proBNP), left ventricular mass index by cardiac magnetic imaging, and ambulatory blood pressure was measured in 30 thrice weekly hemodiafiltration patients. Time‐averaged fluid overload (TAFO) was quantified by bioimpedance spectroscopy. In the study group, left ventricular hypertrophy was found to be 26% by cardiac magnetic resonance. Ambulatory blood pressure was 130 mmHg (112–151) requiring a low equivalent dose of medication of 0.25 units (0–1). Significantly, lower levels of left ventricular mass index (P < 0.05) were associated in those patients with TAFO <1 L or NT‐proBNP <1200 pg/mL or cTnT <0.1 ug/L. In the subgroups, 16 patients had normal cTnT (<0.03 ug/L), 16 patients had NT‐proBNP <400 pg/mL, and 20 patients had TAFO <1 L. Nine patients had both cTnT <0.03 ug/L and NT‐proBNP <400 pg/mL. Normally hydrated thrice‐weekly hemodiafiltration patients can have cardiac biomarker and TAFO levels indistinguishable from the normal healthy population. Obtaining TAFO by bioimpedance monitoring can offer a practical alternative to serum cardiac biomarkers.  相似文献   
992.
993.
Oestrogenic isoflavones (e.g. daidzein) present in soy‐based foods are likely to be important in food functionality. Biotransformation of daidzein during fermentation‐based soy‐containing food manufacture forms three trihydroxy metabolites, 6‐ortho‐hydroxydaidzein (6‐OHD), 8‐ortho‐hydroxydaidzein (8‐OHD) and 3′‐ortho‐hydroxydaidzein (3′‐OHD) which alters the oestrogenicity of the final food product. We report that Escherichia coli (a key component of the gut microbiome) metabolism converts 8‐OHD to 6‐OHD with a likely concomitant increase in oestrogenicity. This means that the functionality of 8‐OHD‐containing soy‐based foods is altered by gut microbiome metabolism. This change in oestrogenicity‐based food functionality might have benefits for postmenopausal women, while being a feminising health risk for males and could add to the risk of oestrogen‐mediated precocious puberty in girls.  相似文献   
994.
The effects of microfluidisation of milk at different pressures, prior to heat treatment, on structural and sensory properties of low-fat stirred yoghurt, were investigated. Low-fat yoghurts prepared from microfluidised milk were compared with low-fat (1.5%) and full-fat (3.5%) control yoghurts made with homogenised (20/5 MPa) milk. The microstructure of low-fat yoghurts prepared with microfluidised milk consisted of smaller and more uniform fat globules, well incorporated into more interconnected fat-protein gel networks, compared with those of control yoghurts. This modification in microstructure caused significant changes in gel particle size, sensory profile and rheological behaviour. Microfluidisation increased the gel particle size, gel strength and viscosity; marked beneficial effects were found at higher pressures (50–150 MPa). Microfluidising milk at 50–150 MPa increased the gel strength by 171–195% and viscosity by 98–103%, creating low-fat yoghurts with creaminess and desirable texture properties similar to, or better than, full-fat conventional yoghurt.  相似文献   
995.
Post-occupancy evaluation - where are you?   总被引:4,自引:0,他引:4  
  相似文献   
996.
Over the last decades, satellite remote sensing has proved to be a valuable and effective tool for monitoring physical and biological ocean processes. However there are cases where data from one remote sensor alone cannot be interpreted unambiguously. In these situations the combination of data from different sensors can help to understand the observed processes due to the combined benefits of the various strengths and advantages of individual instruments. This paper illustrates the potential of synergy between synthetic aperture radar data and data from thermal and optical satellite sensors. Different aspects of oceanic and atmospheric fronts, eddies, upwelling, internal waves and surface films are imaged by the sensors and combined data give a broader picture of the physical processes involved. While the strengths of synergy are demonstrated in several examples, more frequent coincidence of data from existing and future sensors will be necessary before the benefits of synergy occur on an operational basis.  相似文献   
997.
998.
999.
1000.
Aldo-keto reductases (AKRs) oxidize structurally diverse PAH trans -dihydrodiols to yield reactive and redox active o -quinones. This study examined the ability of AKR1C2 and AKR1C4 to oxidize PAH trans -dihydrodiols of the benz[ a ]anthracene series. The enzymes oxidized 100% of the racemic trans -dihydrodiols and the highest utilization ratios were observed for the more potent proximate carcinogens 7,12-dimethylbenz[ a ]anthracene-3,4-diol (DMBA-3,4-diol) and 7-methylbenz[ a ]anthracene-3,4-diol (7-MBA-3,4-diol). Human multiple tissue expression array analysis revealed high expression of AKR1C isoforms in the human lung carcinoma cell line A549. Both Western blot analysis using AKR1C9 antisera and enzymatic assays using 1-acenapthanol as substrate confirmed the presence of active AKR1C enzymes in A549 cells. To determine the importance of AKR1C-mediated trans -dihydrodiol oxidation in A549 cells, DMBA-3,4-diol was incubated with cell lysates in the presence of 2-mercaptoethanol. Liquid chromatography/mass spectrometric analysis identified peaks that corresponded to the synthetically prepared mono- and bis -thioether conjugates of DMBA-3,4-dione confirming the ability of these cells to oxidize DMBA-3,4-diol to the corresponding o -quinone. Together, these studies demonstrate the importance of human AKR1Cs in PAH activation and their possible role in lung cancer.  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