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   468篇
  免费   14篇
耳鼻咽喉   3篇
儿科学   5篇
妇产科学   5篇
基础医学   50篇
口腔科学   2篇
临床医学   26篇
内科学   125篇
皮肤病学   2篇
神经病学   16篇
特种医学   98篇
外科学   58篇
综合类   1篇
预防医学   29篇
眼科学   4篇
药学   45篇
中国医学   2篇
肿瘤学   11篇
  2022年   4篇
  2021年   7篇
  2020年   2篇
  2019年   5篇
  2018年   3篇
  2017年   5篇
  2016年   3篇
  2015年   5篇
  2014年   9篇
  2013年   11篇
  2012年   35篇
  2011年   26篇
  2010年   17篇
  2009年   20篇
  2008年   19篇
  2007年   24篇
  2006年   25篇
  2005年   16篇
  2004年   15篇
  2003年   15篇
  2002年   17篇
  2001年   16篇
  2000年   25篇
  1999年   18篇
  1998年   2篇
  1997年   3篇
  1996年   9篇
  1995年   6篇
  1994年   3篇
  1993年   8篇
  1992年   5篇
  1991年   3篇
  1990年   12篇
  1989年   11篇
  1988年   8篇
  1987年   12篇
  1986年   8篇
  1985年   6篇
  1984年   5篇
  1983年   4篇
  1982年   3篇
  1981年   3篇
  1980年   2篇
  1979年   3篇
  1978年   3篇
  1977年   2篇
  1976年   3篇
  1975年   4篇
  1970年   4篇
  1969年   2篇
排序方式: 共有482条查询结果,搜索用时 15 毫秒
1.
2.
In many plants, osmotic stress induces a rapid accumulation of proline through de novo synthesis from glutamate. This response is thought to play a pivotal role in osmotic stress tolerance [Kishor, P. B. K., Hong, Z., Miao, G.-H., Hu, C.-A. A. and Verma, D. P. S. (1995) Plant Physiol. 108, 1387-1394]. During recovery from osmotic stress, accumulated proline is rapidly oxidized to glutamate and the first step of this process is catalyzed by proline oxidase. We have isolated a full-length cDNA from Arabidopsis thaliana, At-POX, which maps to a single locus on chromosome 3 and that encodes a predicted polypeptide of 499 amino acids showing significant similarity with proline oxidase sequences from Drosophila and Saccharomyces cerevisiae (55.5% and 45.1%, respectively). The predicted location of the encoded polypeptide is the inner mitochondrial membrane. RNA gel blot analysis revealed that At-POX mRNA levels declined rapidly upon osmotic stress and this decline preceded proline accumulation. On the other hand, At-POX mRNA levels rapidly increased during recovery. Free proline, exogenously added to plants, was found to be an effective inducer of At-POX expression; indeed, At-POX was highly expressed in flowers and mature seeds where the proline level is higher relative to other organs of Arabidopsis. Our results indicate that stress- and developmentally derived signals interact to determine proline homeostasis in Arabidopsis.  相似文献   
3.
Camurati-Engelmann disease, progressive diaphyseal dysplasia, or diaphyseal dysplasia Camurati-Engelmann is a rare, autosomal dominantly inherited bone disease, characterised by progressive cortical expansion and sclerosis mainly affecting the diaphyses of the long bones associated with cranial hyperostosis. The main clinical features are severe pain in the legs, muscular weakness, and a waddling gait. The underlying cause of this condition remains unknown.In order to localise the disease causing gene, we performed a linkage study in a large Jewish-Iraqi family with 18 affected subjects in four generations. A genome wide search with highly polymorphic markers showed linkage with several markers at chromosome 19q13. A maximum lod score of 4.9 (theta=0) was obtained with markers D19S425 (58.7 cM, 19q13.1) and D19S900 (67.1 cM, 19q13. 2). The disease causing gene is located in a candidate region of approximately 32 cM, flanked by markers D19S868 (55.9 cM, 19q13.1) and D19S571 (87.7 cM, 19q13.4).  相似文献   
4.
5.
The metabolism of [1,3-(13)C]glycerol-1,2,3-tris(methylsuccinate) and glycerol-1,2,3-tris(methyl[2,3-(13)C] succinate) was examined in hepatocytes prepared from hereditarily diabetic Goto-Kakizaki rats. Over 120 min incubation in the presence of one of the two (13)C-labelled esters (2.5 mM), the output of (13)C-enriched glucose averaged 57.1 +/- 18.5 and 54.1 +/- 22.7 nmol per 10(6) cells, when expressed as [1,3-(13)C]glycerol and [2,3-(13)C] succinate equivalent, respectively. In the case of [1,3-(13)C]glycerol-1,2,3-tris(methyl-succinate), the molecules of glucose were symmetrically labelled. In the case of glycerol-1,2,3-tris(methyl[2,3-(13)C] succinate), however, both the single-labelled and double-labelled isotopomers of glucose contained more (13)C atoms in their C(6)-C(5)-C(4) than C(1)-C(2)-C(3) moiety. These findings indicate that glycerol-1,2,3-tris(methylsuccinate), recently proposed as a novel insulinotropic tool for the treatment of non-insulin-dependent diabetes mellitus, is efficiently metabolized in hepatocytes from diabetic rats, the high rate of gluconeogenesis coinciding with channelling of D-glyceraldehyde-3-phosphate between glyceraldehyde-3-phosphate dehydrogenase and phosphofructoaldolase.  相似文献   
6.
Animal studies have indicated that technetium-99m l,l-ethylenedicysteine (99mTc-l,l-EC) may be a promising tracer agent for renal function studies. We have performed a paired study with 99mTc-mercaptoacetyltriglycine (99mTc-MAG3) and 99mTc-l,l-EC in six male volunteers. In both cases, iodine-131-labelled o-iodohippurate was co-injected as an internal biological standard. The analog images between 0 and 30 min p.i. were of identical diagnostic value for both tracer agents. The two renograms were similar in all volunteers. The mean 1-h plasma clearance for 99mTc-MAG3 and 99 mTc-l,l-EC was significantly different, respectively 382.9 ± 17.1 ml/min per 1.73 m2 versus 460.2 ± 47.7 ml/min per 1.73 m2 (P<0.003). The urinary excretion after 30 min p.i. was 69.4% ± 5.6% of the injected dose for 99mTc-MAG3 versus 66.5% ± 2.5% for 99mTc-l,l-EC (P>0.05) and after 60 min p.i. respectively 83.1% ± 3.9% versus 79.8 % ± 4.3 % (P > 0.05). 99mTc-l,l-EC has a very low plasma protein binding (31% ± 6.8%) as compared to 99mTc-MAG3 (88% ± 5.2%) and a larger volume of distribution. Although the exact mechanism responsible for the high plasma clearance of 99mTc-l,l-EC is not yet fully known, we conclude that this new agent merits further clinical evaluation in patients to establish its value as a renal radiopharmaceutical. Correspondence to: A. Verbruggen  相似文献   
7.
Bioassay-guided fractionation of the dichloromethane extracts of the roots and the bark of Zanthoxylum usambarense led to the isolation of two physiologically active compounds, i.e. canthin-6-one 1 (fungicide) and pellitorine 4 (insecticide). Together with oxychelerythrine 2, norchelerythrine 3, (+)-sesamin 5 and (+)-piperitol-3,3-dimethylallyl ether 6, they were isolated for the first time from this plant.  相似文献   
8.
9.
OBJECTIVES—(1)To analyse the in situ expression of adhesion molecules in rheumatoid nodules. (2) To compare the endothelial expression of adhesion molecules in synovial tissue and subcutaneous nodules obtained from the same patients. (3) To compare the expression of adhesion molecules and activation markers on T cell lines from nodules and synovium.
METHODS—(1) Immunohistochemical analysis by APAAP technique of E selectin, CD44, ICAM-1, PECAM-1, and VCAM-1 was performed on 10 rheumatoid nodules from seven patients with rheumatoid arthritis (RA); nodules and synovium were simultaneously analysed from three patients. (2) T cell lines were generated from RA nodules (n=7) and synovium (n=7) by interleukin 2 expansion, and subsequently characterised by flow cytometry for surface expression of αEβ7, α4β7, CD44, L selectin, LFA-1a, PECAM-1, and CD30.
RESULTS—(1) In rheumatoid nodules, the palisading layer strongly stains for ICAM-1 and PECAM-1, but less pronounced for CD44. VCAM-1 staining was usually negative. ICAM-1 is upregulated in the vessels surrounding the central zone of fibrinoid necrosis. The immunohistological picture in different nodules derived from the same patient was similar. (2) The endothelial expression of adhesion molecules is comparable in RA nodules and synovium on an individual level, except for E selectin, which is overexpressed in nodule endothelium. (3) T cell lines from nodules and synovium display similar adhesion molecule profiles. However, the expression of CD30, a T cell activation marker linked with Th2 subsets, is higher in nodules compared with synovium.
CONCLUSION—These data support a recirculation hypothesis of T cells between articular and extra-articular manifestations in RA, although the activation state of the T cells in each of these localisations may differ.

Keywords: T cells; adhesion molecules; rheumatoid nodules; rheumatoid synovium  相似文献   
10.
The cathepsin K inhibitor odanacatib (ODN), currently in phase 3 development for postmenopausal osteoporosis, has a novel mechanism of action that reduces bone resorption while maintaining bone formation. In phase 2 studies, odanacatib increased areal bone mineral density (aBMD) at the lumbar spine and total hip progressively over 5 years. To determine the effects of ODN on cortical and trabecular bone and estimate changes in bone strength, we conducted a randomized, double‐blind, placebo‐controlled trial, using both quantitative computed tomography (QCT) and high‐resolution peripheral (HR‐p)QCT. In previously published results, odanacatib was superior to placebo with respect to increases in trabecular volumetric BMD (vBMD) and estimated compressive strength at the spine, and integral and trabecular vBMD and estimated strength at the hip. Here, we report the results of HR‐pQCT assessment. A total of 214 postmenopausal women (mean age 64.0 ± 6.8 years and baseline lumbar spine T‐score –1.81 ± 0.83) were randomized to oral ODN 50 mg or placebo, weekly for 2 years. With ODN, significant increases from baseline in total vBMD occurred at the distal radius and tibia. Treatment differences from placebo were also significant (3.84% and 2.63% for radius and tibia, respectively). At both sites, significant differences from placebo were also found in trabecular vBMD, cortical vBMD, cortical thickness, cortical area, and strength (failure load) estimated using finite element analysis of HR‐pQCT scans (treatment differences at radius and tibia = 2.64% and 2.66%). At the distal radius, odanacatib significantly improved trabecular thickness and bone volume/total volume (BV/TV) versus placebo. At a more proximal radial site, odanacatib attenuated the increase in cortical porosity found with placebo (treatment difference = –7.7%, p = 0.066). At the distal tibia, odanacatib significantly improved trabecular number, separation, and BV/TV versus placebo. Safety and tolerability were similar between treatment groups. In conclusion, odanacatib increased cortical and trabecular density, cortical thickness, aspects of trabecular microarchitecture, and estimated strength at the distal radius and distal tibia compared with placebo. © 2014 American Society for Bone and Mineral Research  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