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   368篇
  免费   46篇
电工技术   1篇
化学工业   210篇
机械仪表   5篇
建筑科学   11篇
能源动力   6篇
轻工业   74篇
水利工程   2篇
石油天然气   7篇
无线电   17篇
一般工业技术   39篇
冶金工业   20篇
自动化技术   22篇
  2023年   3篇
  2022年   45篇
  2021年   59篇
  2020年   13篇
  2019年   8篇
  2018年   13篇
  2017年   19篇
  2016年   17篇
  2015年   14篇
  2014年   20篇
  2013年   16篇
  2012年   18篇
  2011年   36篇
  2010年   18篇
  2009年   16篇
  2008年   17篇
  2007年   13篇
  2006年   12篇
  2005年   7篇
  2004年   7篇
  2003年   7篇
  2002年   5篇
  2001年   3篇
  2000年   2篇
  1999年   5篇
  1998年   3篇
  1997年   4篇
  1996年   4篇
  1995年   2篇
  1993年   2篇
  1992年   1篇
  1991年   1篇
  1989年   1篇
  1987年   1篇
  1981年   1篇
  1976年   1篇
排序方式: 共有414条查询结果,搜索用时 31 毫秒
21.
Prostate cancer (PCa) is globally the second most diagnosed cancer type and the most common cause of cancer-related deaths in men. Family history of PCa, hereditary breast and ovarian cancer (HBOC) and Lynch syndromes (LS), are among the most important risk factors compared to age, race, ethnicity and environmental factors for PCa development. Hereditary prostate cancer (HPCa) has the highest heritability of any major cancer in men. The proportion of PCa attributable to hereditary factors has been estimated in the range of 5–15%. To date, the genes more consistently associated to HPCa susceptibility include mismatch repair (MMR) genes (MLH1, MSH2, MSH6, and PMS2) and homologous recombination genes (BRCA1/2, ATM, PALB2, CHEK2). Additional genes are also recommended to be integrated into specific research, including HOXB13, BRP1 and NSB1. Importantly, BRCA1/BRCA2 and ATM mutated patients potentially benefit from Poly (ADP-ribose) polymerase PARP inhibitors, through a mechanism of synthetic lethality, causing selective tumor cell cytotoxicity in cell lines. Moreover, the detection of germline alterations in MMR genes has therapeutic implications, as it may help to predict immunotherapy benefits. Here, we discuss the current knowledge of the genetic basis for inherited predisposition to PCa, the potential target therapy, and the role of active surveillance as a management strategy for patients with low-risk PCa. Finally, the current PCa guideline recommendations are reviewed.  相似文献   
22.
23.
24.
The retinal pigmented epithelium (RPE) plays a pivotal role in retinal homeostasis. It is therefore an interesting target to fill the unmet medical need of different retinal diseases, including age-related macular degeneration and Stargardt disease. RPE replacement therapy may use different cellular sources: induced pluripotent stem cells or embryonic stem cells. Cells can be transferred as suspension on a patch with different surgical approaches. Results are promising although based on very limited samples. In this review, we summarize the current progress of RPE replacement and provide a comparative assessment of different published approaches which may become standard of care in the future.  相似文献   
25.
Lipophilic bioactive compounds in oils recovered from the seeds of eight pear (Pyrus communis L.) cultivars were studied. Oil yield in pear seeds ranged between 16.3 and 31.5 % (w/w) dw. The main fatty acids were palmitic acid (6.13–8.52 %), oleic acid (27.39–38.17 %) and linoleic acid (50.73–63.78 %), all three representing 96–99 % of the total detected fatty acids. The range of total tocochromanols was between 120.5 and 216.1 mg/100 g of oil. Independent of the cultivar, the γ‐tocopherol was the main tocochromanol and constituted approximately 88 %. The contents of the carotenoids and squalene were between 0.69–2.99 and 25.5–40.8 mg/100 g of oil, respectively. The β‐sitosterol constituted 83.4–87.6 % of total sterols contents, which ranged between 276.4 and 600.1 mg/100 g of oil. Three significant correlations were found between oil yield and total contents of sterols (r = ?0.893), tocochromanols (r = ?0.955) and carotenoids (r = ?0.685) in pear seed oils.  相似文献   
26.
Adamantylation of substituted benzenes with 1-bromo-adamantane was catalyzed by solid acids including acidic ion exchange and ionomer resins, HY zeolite, sulfated zirconia and supported superacids on HY zeolite and SiO2. Adamantylation generally takes place in excellent yield giving predominantly para products without formation of byproducts. The reactions did not require the usual workup of Friedel-Crafts reactions as catalysts were simply filtered of. Cross-linked polystyrene resin sulfonic acid (Amberlyst) was found particularly suitable as besides its high catalytic activity, high regioselectivity was observed with almost exclusive formation ofp-adamantylated benzenes. AMI, PM3 and MNDO semiempirical calculations of heats of formation showed that of all regioisomers, the para isomer is the most stable. The temperature dependence of adamantylation was also investigated allowing the optimization ofp-substituted product in high yield and excellent selectivity. Lack of isomerization of 1-p-tolyla-damantane using solid (Amberlyst, Nafion-H) and liquid acids (neat and modified trifluoromethanesulfonic acid) indicates absence of product isomerization, while the intramolecular rearrangement of the intermediate arenium complex is still possible.Catalysis by solid superacids, Part 30. For part 29, see ref.[1A].  相似文献   
27.
28.
29.
In this study, nanosized clay particles were introduced into wood fiber/plastic composites (WPCs) to improve their mechanical properties and flame retardancy, which are especially important in various automotive and construction applications. A high degree of exfoliation for nanoclay in the wood fiber/high density polyethylene (HDPE) composites was successfully achieved with the aid of maleated HDPE (PE‐g‐MAn), through a melt blending masterbatch process. The structures and morphologies of the composites were determined using X‐ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. This article presents the effects of clay content and degree of clay dispersion on the mechanical and physical properties and flame retardancy of wood fiber/HDPE composites that contained a small amount of clay, in the range of 3–5 wt %. We concluded that achieving a higher degree of dispersion for the nanosized clay particles is critical to enhance the mechanical properties and the flame retardancy of WPCs when small amounts of clay are used. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   
30.
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