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   217篇
  免费   38篇
  国内免费   2篇
  257篇
  2022年   2篇
  2021年   3篇
  2020年   6篇
  2019年   2篇
  2018年   6篇
  2016年   14篇
  2015年   14篇
  2014年   5篇
  2013年   16篇
  2012年   14篇
  2011年   15篇
  2010年   9篇
  2009年   8篇
  2008年   5篇
  2007年   6篇
  2006年   3篇
  2005年   5篇
  2004年   5篇
  2003年   6篇
  2001年   13篇
  2000年   5篇
  1999年   6篇
  1998年   4篇
  1997年   6篇
  1995年   9篇
  1994年   4篇
  1993年   6篇
  1992年   8篇
  1991年   4篇
  1990年   9篇
  1989年   1篇
  1988年   4篇
  1987年   4篇
  1986年   4篇
  1985年   6篇
  1984年   2篇
  1983年   1篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
  1979年   3篇
  1978年   1篇
  1976年   1篇
  1975年   1篇
  1974年   1篇
  1969年   1篇
  1967年   1篇
  1966年   1篇
  1928年   1篇
  1910年   1篇
排序方式: 共有257条查询结果,搜索用时 15 毫秒
251.
X-ray microanalysis has been used to detect chromium in the histochemical reaction product resulting from the reaction of noradrenaline with glutaraldehyde during fixation of the rat adrenal medulla and subsequent treatment with potassium dichromate. In unstained ultrathin sections, noradrenaline cells can be identified by their content of highly electron-dense storage granules, which enables individual granules to be analysed quantitatively to assess the amount of bound chromium within them. In young adult (4-month-old) rats the mean chromium content of noradrenaline-containing adrenal medullary granules was 443.6±50.7 mM/kg dry weight. In aged (24-month-old) animals the mean chromium content was 267.0±64.0 mM/kg dry weight which was significantly (P<0.01) lower then the value for the young adult rats. Some noradrenaline cells contained granule populations, which were markedly less electron dense than those in the young adults and this is reflected in the ranges of chromium values recorded between individual cells in the 24-month-old animals. There were also noradrenaline cells in the medulla of the aged animals, which contained highly electron-dense granules but these did not contain as much bound chromium as the highest values recorded in the young adult animals. The results are discussed in the context of the growth of the rat adrenal medulla throughout the lifespan and with respect to the effects of age on the integrity of storage granules.  相似文献   
252.
OBJECTIVE--To assess the need for formal psychotherapeutic intervention in children attending a children''s haemophilia clinic after some of them had been diagnosed as positive for HIV. DESIGN--Comparison of haemophiliac children with matched control groups of diabetic and healthy children. SETTING--The West of Scotland Children''s Haemophilia Centre, Glasgow. PATIENTS--43 Children aged 3 to 16 years with mild, moderate, and severe clotting disorders were matched with control groups of 46 diabetic children and 42 physically healthy children. INTERVENTIONS--Parents of children aged 3-5 years were interviewed with the behaviour screening questionnaire. Children aged 6 to 16 were assessed by parental and teacher report using standardised questionnaires and self report using a computerised depression inventory. All were scored numerically according to the presence of symptoms of emotional and behavioural problems. MAIN OUTCOME MEASURES--The groups were compared for mean scores on each rating device and for number of children achieving scores within the pathological range. RESULTS--In the 6-16 age group five haemophiliac children, five diabetic children, and three healthy children scored in the pathological range on the parent questionnaire, as did two, three, and five respectively on the teacher questionnaire and four, four, and eight on the depression inventory. There was no significant difference across the three groups. Analysis of mean scores similarly showed no significant difference across groups. In contrast, the single measure used for younger children showed an increase in behavioural difficulties among the diabetic children. CONCLUSION--Haemophiliac children attending the West of Scotland Centre were no more disturbed than their diabetic or healthy peers despite the identification of HIV infection within the clinic and the widespread adverse publicity associated with AIDS and HIV infection.  相似文献   
253.
In previous studies we identified an epididymal gene that exhibits homology to the cystatin family of cysteine protease inhibitors. The expression of this gene, termed CRES (cystatin-related epididymal and spermatogenic), was shown to be highly restricted to the proximal caput epididymal epithelium with less expression in the testis and no expression in the 24 other tissues examined. In this report, studies were carried out to examine CRES gene expression in the testis as well as to characterize the CRES protein in the testis and epididymis. In situ hybridization experiments revealed that within the testis CRES gene expression is stage-specific during spermatogenesis and is exclusively expressed by the round spermatids of Stages VII-VIII and the early elongating spermatids of Stages IX and X. Immunohistochemical studies demonstrated that CRES protein was transiently expressed in both the testis and epididymis. Within the testis the protein was localized to the elongating spermatids, whereas within the epididymis CRES protein was exclusively synthesized by the proximal caput epithelium and then secreted into the lumen. Surprisingly, the secreted CRES protein had completely disappeared from the epididymal lumen by the distal caput epididymidis. Western blot analysis of testicular and epididymal proteins showed that the CRES antibody specifically recognized a predominant 19 kDa CRES protein and a less abundant 14 kDa form. These observations suggest that the CRES protein performs a specialized role during sperm development and maturation. © 1995 Wiley-Liss, Inc.  相似文献   
254.
255.
Chemoenzymatic production of 1,5-dimethyl-2-piperidone   总被引:3,自引:0,他引:3  
A chemoenzymatic process for the preparation of 1,5-dimethyl-2-piperidone (1,5-DMPD) from 2-methylglutaronitrile (MGN) has been demonstrated. MGN was first hydrolyzed to 4-cyanopentanoic acid (4-CPA) ammonium salt using the nitrilase activity of immobilized Acidovorax facilis 72W cells. The hydrolysis reaction produced 4-CPA ammonium salt with greater than 98% regioselectivity at 100% conversion, and at concentrations of 170–210 g 4-CPA/l. Catalyst productivities of at least 1000 g 4-CPA/g dry cell weight (dcw) of immobilized cells were achieved by recycling the immobilized-cell catalyst in consecutive stirred-batch reactions. After recovery of the immobilized cell catalyst for reuse, the 4-CPA ammonium salt in the aqueous product mixture was directly converted to 1,5-DMPD by low-pressure catalytic hydrogenation in the presence of added methylamine.  相似文献   
256.
257.
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