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   1612181篇
  免费   107410篇
  国内免费   2997篇
耳鼻咽喉   22736篇
儿科学   50766篇
妇产科学   41822篇
基础医学   241716篇
口腔科学   44741篇
临床医学   142717篇
内科学   299879篇
皮肤病学   38154篇
神经病学   120490篇
特种医学   64148篇
外国民族医学   263篇
外科学   240970篇
综合类   29529篇
现状与发展   4篇
一般理论   397篇
预防医学   114469篇
眼科学   38085篇
药学   130060篇
  7篇
中国医学   4939篇
肿瘤学   96696篇
  2021年   14310篇
  2019年   13289篇
  2018年   18616篇
  2017年   14508篇
  2016年   16950篇
  2015年   20001篇
  2014年   26172篇
  2013年   37109篇
  2012年   51532篇
  2011年   54141篇
  2010年   31644篇
  2009年   29169篇
  2008年   48219篇
  2007年   50874篇
  2006年   50956篇
  2005年   48458篇
  2004年   46154篇
  2003年   43924篇
  2002年   42246篇
  2001年   79920篇
  2000年   82035篇
  1999年   67964篇
  1998年   17592篇
  1997年   15419篇
  1996年   15509篇
  1995年   14431篇
  1994年   13152篇
  1992年   50829篇
  1991年   49870篇
  1990年   49458篇
  1989年   47488篇
  1988年   43073篇
  1987年   42125篇
  1986年   39647篇
  1985年   37539篇
  1984年   27453篇
  1983年   23179篇
  1982年   12844篇
  1979年   25210篇
  1978年   17429篇
  1977年   15318篇
  1976年   13821篇
  1975年   15752篇
  1974年   18523篇
  1973年   17672篇
  1972年   17016篇
  1971年   16098篇
  1970年   14808篇
  1969年   14198篇
  1968年   12933篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
We report a 3-year-old girl with hereditary motor and sensory neuropathy type III with a decrease in unmyelinated fibers. There have been few reports of such cases. The present findings suggest the possibility that the primary lesion in this disease is in the axons. We consider that more attention should be paid to the changes in unmyelinated fibers and axons in further studies on this disease.  相似文献   
992.
Aseptic bone necrosis is a well known complication after corticosteroid treatment in adults and several hundred cases have been reported. Alterations in fat metabolism with vascular occlusion due to fat embolization, as well as microtraumata and osteoporosis are discussed as etiologic factors. In contrast, aseptic bone necrosis in relation to corticosteroid treatment is rare in children and adolescents. We therefore report 3 patients, aged from 10 to 18 years, suffering from severe aplastic anemia, meningeal relapse after acute lymphocytic leukemia and acute myelocytic leukemia respectively, who developed aseptic bone necrosis 6, 11, and 20 months following the onset of corticoid therapy. The patients survive from 28+ to 50+ months after diagnosis of their initial hematologic disease, as it can be expected today for increasing numbers of patients. We therefore believe, that aseptic bone necrosis may represent a serious therapy related complication and suggest that, diagnostic examination in patients with suspicious complaints of the hip, shoulder or knee should also exclude the possibility of a bone necrosis after leucemic relapse has been ruled out. Since radiological changes only develop several weeks to months after the onset of the clinical symptoms and because of the disabling consequences for patients, misdiagnosed at the beginning, a 99 technetium bone scan should be done as early as possible. Corticosteroids, despite their serious side effects are still being considered as a important part of hematologic therapy and are not being omitted in the near future, so that the earliest possible diagnosis of bone necrosis will remain of great importance.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
993.
Contact lens-induced corneal warpage   总被引:1,自引:0,他引:1  
  相似文献   
994.
The effect of ascorbate on the release of acetylcholine from the longitudinal muscle-myenteric plexus preparation of the guinea-pig isolated ileum has been investigated using a bioassay and an isotopic technique. Ascorbate at 5 mM increased the spontaneous output of acetylcholine and enhanced DMPP-induced output of acetylcholine, while iso-ascorbate, 5 mM, did not. Ascorbate did not influence either the spontaneous or the DMPP-induced release of acetylcholine from synaptosomes of the ileal myenteric plexus. These results suggest that ascorbate promotes acetylcholine release from intramural cholinergic nerves.  相似文献   
995.
'Trans' fatty acids are unsaturated acids with special structural features that occur naturally in dietary fats from animal and plant sources and in fats processed by catalytic hydrogenation. They are readily metabolized by the human body. Thus, although when consumed in the diet they are incorporated into body fat (including depot and milk fats), they are subject to rapid 'turnover'. In physical properties, trans monounsaturatedfatty acids are intermediate between cis-monounsaturated and saturated acids, and they tend to be treated either as saturated or cis-monounsaturated acids in metabolic pathways. The author argues in this article that any adverse effects on health or metabolism that may have been observed can be ascribed to an imbalance between the intake of trans and essential fatty acids. Such imbalances, could also occur with non-essential fatty acids other than trans fats. Normally, the amounts eaten in average diets would not pose serious problems and only when products have excessively high trans contents and make a significant contribution to the diet need trans acids be highlighted on labels.  相似文献   
996.
This study reports the purification and characterization of a high molecular weight human breast cancer-associated antigen identified by a previously described (1,2) murine monoclonal antibody, BCD-B4. Immunohistochemical analysis indicated that BCD-B4 recognizes an antigen expressed in an altered form on the human breast carcinoma cell line, BT-20, compared to the non-malignant human mammary epithelial cell line, HBL-100. Chemical treatments and enzymatic digestions suggested that the recognized moiety was a protein. The antigenic determinant was resistant to neuraminidase and periodate treatments but was sensitive to trypsin and proteinase K. The antigen was purified by affinity chromatography and its molecular weight, determined by SDS-PAGE analysis under non-reducing conditions, was proven to be 250 Kd. Under reducing conditions, the molecule dissociated into two polypeptides of 125 and 45 Kd, respectively. Both subunits could be isolated from normal HBL-100 and neoplastic BT-20 cellular protein extracts by affinity chromatography. The higher molecular weight subunit showed; however, qualitative and quantitative differences between the two cell lines: it was expressed in greater quantity on BT-20 cells and its molecular weight was 15 Kd higher. Both subunits could also be identified by immunoblots of BT-20 cells.  相似文献   
997.
To obtain more information on the biochemical background, of methyl mercury (MeHg) and triethyl lead (Et3Pb) toxicity, the doses which were needed to alter the cellular content of adenine nucleotides were compared to doses which induced morphological alterations. Three-week-old cultures of brain cells from new-born rat were incubated for 5-60 min. with 28, 16, and 8 X 10(-6) M MeHg or with 3 X 10(-6) M Et3Pb in the nutrition medium. MeHg at 28 and 16 X 10(-6) M simultaneously changed the cell shape and reduced both the cellular content of adenine nucleotides and the relative level of ATP. In cells treated with 16 X 10(-6) M MeHg, a cellular increase in inosine and hypoxanthine and an unaltered content of adenine nucleotides in the nutrition medium, points to an intracellular degradation of adenine nucleotides. Incubation with 8 X 10(-6) M MeHg during the first hour of incubation, did not change the content of adenine nucleotides, however, MeHg induced a slowly progressing degeneration of cellular extensions. 3 X 10(-6) M Et3Pb induced morphological alterations but no changes in cellular nucleotide levels. The results show that morphological alterations occur in MeHg and Et3Pb treated cultures at concentrations of the compounds which are too low to change the content and composition of cellular adenine nucleotides.  相似文献   
998.
999.
1000.
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