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   1812篇
  免费   107篇
  国内免费   8篇
电工技术   28篇
综合类   10篇
化学工业   163篇
金属工艺   11篇
机械仪表   28篇
建筑科学   39篇
矿业工程   16篇
能源动力   22篇
轻工业   321篇
水利工程   7篇
石油天然气   6篇
武器工业   1篇
无线电   154篇
一般工业技术   192篇
冶金工业   762篇
原子能技术   33篇
自动化技术   134篇
  2022年   14篇
  2021年   16篇
  2020年   11篇
  2019年   17篇
  2018年   19篇
  2017年   13篇
  2016年   24篇
  2015年   18篇
  2014年   15篇
  2013年   62篇
  2012年   50篇
  2011年   64篇
  2010年   31篇
  2009年   34篇
  2008年   62篇
  2007年   62篇
  2006年   60篇
  2005年   66篇
  2004年   61篇
  2003年   50篇
  2002年   52篇
  2001年   35篇
  2000年   28篇
  1999年   40篇
  1998年   212篇
  1997年   119篇
  1996年   98篇
  1995年   47篇
  1994年   59篇
  1993年   67篇
  1992年   13篇
  1991年   27篇
  1990年   20篇
  1989年   24篇
  1988年   14篇
  1987年   16篇
  1986年   16篇
  1985年   19篇
  1984年   14篇
  1983年   18篇
  1982年   15篇
  1981年   15篇
  1980年   19篇
  1979年   14篇
  1978年   13篇
  1977年   28篇
  1976年   57篇
  1974年   12篇
  1971年   8篇
  1970年   10篇
排序方式: 共有1927条查询结果,搜索用时 31 毫秒
1.
2.
Fluorescent nanodiamonds (fNDs) containing nitrogen vacancy (NV) centers are promising candidates for quantum sensing in biological environments. This work describes the fabrication and implementation of electrospun poly lactic‐co‐glycolic acid (PLGA) nanofibers embedded with fNDs for optical quantum sensing in an environment, which recapitulates the nanoscale architecture and topography of the cell niche. A protocol that produces uniformly dispersed fNDs within electrospun nanofibers is demonstrated and the resulting fibers are characterized using fluorescent microscopy and scanning electron microscopy (SEM). Optically detected magnetic resonance (ODMR) and longitudinal spin relaxometry results for fNDs and embedded fNDs are compared. A new approach for fast detection of time varying magnetic fields external to the fND embedded nanofibers is demonstrated. ODMR spectra are successfully acquired from a culture of live differentiated neural stem cells functioning as a connected neural network grown on fND embedded nanofibers. This work advances the current state of the art in quantum sensing by providing a versatile sensing platform that can be tailored to produce physiological‐like cell niches to replicate biologically relevant growth environments and fast measurement protocols for the detection of co‐ordinated endogenous signals from clinically relevant populations of electrically active neuronal circuits.  相似文献   
3.
Beardless barb is a common fish species used in fermentation of fish paste Ka-pi-plaa. Autolytic profile of beardless barb muscle showed the maximum autolysis was at 50 °C, at both acidic and alkaline pH values. With augmentation concentration of NaCl, autolytic activity slightly decreased. Endogenous proteinases isolated from fish muscle in crude extract forms were also characterised. The acidic proteinases had optimum activity at pH 3.0 and 50°C, and they showed higher proteolytic activity than the alkaline proteinases which were optimally active at pH 9.0 and 50 °C. Proteinases in peak at pH 3.0 were inhibited by pepstatin A, but those in peak at pH 9.0 were highly inhibited by PMSF, TLCK and soybean trypsin inhibitor, suggesting that both aspartic and serine proteinases were existed in beardless barb muscle. The proteinases were stable in pH range of 2.0-5.0 but unstable at the temperatures higher than 40 °C. NaCl suppressed the proteolytic activity, ATP activated the proteinase activity, while CaCl2, MgCl2 and CoCl2 exhibited no influence on the activity. The results implied that cathepsin D is the predominant proteinase responsible for autolysis in beardless barb. The findings were useful to improve the processing and qualities of Ka-pi-plaa product using beardless barb as raw material.  相似文献   
4.
5.
The Psychiatric Assessment Schedule for Adults with Developmental Disability (PAS-ADD) is a semi-structured interview for use with respondents who have learning disability and for key informants. This report investigates the ability of the instrument to detect symptoms that had been found to exist during routine clinical assessment of the patients. Field trials involved 95 referred patients with learning disability and a key informant for each sample member. Clinical opinions of the referring psychiatrists were sought using a symptom checklist. Referrer checklist symptoms and PAS-ADD data were both factor analysed. Validity testing involved (a) computation of correlations between PAS-ADD factors and checklist data and (b) comparison of PAS-ADD and referrers' diagnoses. Results indicated good validity for the PAS-ADD in relation to psychotic symptoms and depressive symptoms. Anxiety symptom identification was not well validated, probably due to small numbers. Expansive mood identified by the referrers was not detected by the PAS-ADD because there is currently no corresponding section in the interview. Where the PAS-ADD produced a diagnosis (in 58 members of the sample), 44 were in agreement with the referrer. Probability of diagnosis by PAS-ADD increased with the number of relevant active symptoms identified by the referrer. The PAS-ADD has been shown in a previous report to have the sensitivity to detect mental disorders not known to psychiatric services. For psychotic and depressive conditions, our results showed that symptom detection was in good agreement with the information provided by the referring psychiatrists on their patients. The PAS-ADD needs a section on hypomania and further investigation of its detection of anxiety disorders.  相似文献   
6.
Renal cell carcinoma may metastasize to the head and neck region at different stages of its evolution. We present a case of an undiagnosed renal cell carcinoma presenting as an ear polyp, and discuss the difficulties of the diagnosis and the management of these tumours.  相似文献   
7.
8.
9.
Fetus-in-fetu is an unusual condition in which a vertebrate fetus is enclosed within the abdomen of another fetus. These occurrences are usually benign. This report describes an instance of malignant recurrence after resection of a fetus-in-fetu.  相似文献   
10.
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