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   2649篇
  免费   118篇
  国内免费   15篇
耳鼻咽喉   14篇
儿科学   56篇
妇产科学   12篇
基础医学   334篇
口腔科学   97篇
临床医学   111篇
内科学   467篇
皮肤病学   32篇
神经病学   230篇
特种医学   95篇
外科学   623篇
综合类   18篇
预防医学   59篇
眼科学   31篇
药学   204篇
中国医学   11篇
肿瘤学   388篇
  2023年   11篇
  2022年   37篇
  2021年   57篇
  2020年   32篇
  2019年   26篇
  2018年   50篇
  2017年   26篇
  2016年   32篇
  2015年   43篇
  2014年   47篇
  2013年   56篇
  2012年   135篇
  2011年   137篇
  2010年   68篇
  2009年   83篇
  2008年   104篇
  2007年   124篇
  2006年   125篇
  2005年   141篇
  2004年   105篇
  2003年   98篇
  2002年   115篇
  2001年   100篇
  2000年   91篇
  1999年   103篇
  1998年   37篇
  1997年   36篇
  1996年   26篇
  1995年   12篇
  1994年   21篇
  1993年   14篇
  1992年   58篇
  1991年   74篇
  1990年   61篇
  1989年   78篇
  1988年   69篇
  1987年   43篇
  1986年   39篇
  1985年   40篇
  1984年   27篇
  1983年   25篇
  1982年   15篇
  1981年   7篇
  1980年   16篇
  1979年   30篇
  1978年   18篇
  1977年   15篇
  1974年   9篇
  1972年   10篇
  1971年   8篇
排序方式: 共有2782条查询结果,搜索用时 31 毫秒
11.
An accurate and reproducible colorimetric assay was established to determine the concentration of basic fibroblast growth factor (bFGF) or bFGF-like activity in culture media and biological fluids. Fetal bovine heart endothelial cell line ATCC CRL 1395 was used as the bFGF-dependent cell line. The proliferation-stimulating activity of bFGF was determined by measuring the amount of formazan formed by the mitochondrial enzymes from a tetrazolium salt, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), instead of counting the viable cell numbers or measuring the incorporation of [3H]-thymidine. The addition of 250 ng/mL of heparin to the culture medium resulted in about a tenfold increase in the proliferation-stimulating activity of bFGF and allowed the detection of as low as 10 pg/mL of bFGF. Heparin also resulted in much smaller inter- and intraassay variations. The bFGF concentrations determined by this colorimetric assay correlated well with those determined by both the [3H]-thymidine incorporation assay using BALB/c 3T3 fibroblast cells (r = 0.998) and the cell number count assay (r = 0.996). This assay can be adapted to quantify bFGF or bFGF-like activity in tissue culture media and biological fluids such as plasma and organ extracts.  相似文献   
12.
An animal model, using distraction force on adult rabbits, was developed to study the effects of nonweight-bearing on articular cartilage in a moving joint. Histologic evaluation was used to compare the morphology of chondrocytes, safranin O intensity, cartilage thickness, and structural changes between the test and contralateral joints. At 3 and 6 weeks, the chondrocytes in superficial and intermediate zones were round, with an increase in cellular volume density and mean cell volume and with less metachromasia; the safranin O intensity and cartilage thickness were the same as in the controls. In cartilage of the 9-week group, mean cell volume decreased with cell cloning in the superficial zone, while numerical density increased and mean matrix volume per cell decreased in the superficial and intermediate zones. The cartilage, with a 34% reduction in thickness and a 53–72% decrease in safranin O intensity from the superficial to the deep zone, had superficial fibrotic proliferation, suface erosion or depression, ard tidemark irregularity. Continuous distraction in a moving joint caused morphological changes in chondrocytes prior to degeneration of cartilage. These results support the hypothesis that the forces perceived by cells may dictate their shape and then stimulate alterations in cellular biochemistry and matrix metabolism.  相似文献   
13.
Meropenem (MEPM, SM-7338), a novel parenteral carbapenem antibiotic, was examined for its effect on intestinal flora in children. Seven children with infectious diseases (3 male and 4 female children of age's ranging from 4 months to 8 years and 9 months weighing from 7.3 to 23.0 kg) were treated with MEPM at doses ranging 10.3 to 40.5 mg/kg 3 or 4 times a day for 6 to 12 days. Before, during and after the treatment, identities and numbers of various bacteria contained in 1 g of feces were determined and fecal beta-lactamase activity and Clostridium difficile D-1 antigen were also assayed. Changes in fecal flora during MEPM treatment was somewhat different depending on cases. Regarding Enterobacteriaceae among aerobes, all of 7 cases exhibited moderate or pronounced reductions in Escherichia coli. Some of the cases exhibited the tendency to increase in Klebsiella oxytoca. Enterobacter cloacae and Citrobacter freundii. E. coli which was reduced during the treatment increased rapidly after the treatment in 5 out of 7 cases, and the initial bacterial counts were restored. Diverse strains were observed within the genus Enterococcus, while the overall bacterial counts of this genus exhibited the tendency to increase during the treatment. As a result, no significant change in total aerobe count was observed in any case except 1 case where Enterococcus count was somewhat reduced. Among anaerobes, major bacteria such as Bacteroides, Bifidobacterium, Eubacterium and Peptococcaceae exhibited tendencies to decrease in some cases during the antibiotic treatment. Two infants and 1 child exhibited significant decreases in total anaerobe counts. In most of the cases, such changes in major anaerobes were transient and bacterial counts recovered to their initial values rapidly after completion of the treatment. In no cases, glucose non-fermentative Gram-negative bacilli or fungus became predominant. Although C. difficile D-1 antigen was observed in 4 cases, its changes had no relationship with characteristics of feces. C. difficile was not detected in any of the cases. MEPM was detected in feces in 4 cases being treatment, in concentrations ranging from 0.35 to 66.0 micrograms/g. Fecal MEPM levels were very low except in 1 case in which beta-lactamase was negative. From these results, effects of MEPM on intestinal flora in children were relatively minor compared to other new beta-lactam drugs. However, a care should be taken to minimize diarrhea and bacterial turnover when a prolonged use of the antibiotic, was practiced because of potential significant effects on intestinal flora.  相似文献   
14.
15.
16.
In the present study, the authors analysed the serial angiographical findings progressing to brain death and their relation to the intracranial pressure (ICP) and the cerebral perfusion pressure (CPP). Seventy two patients, from four to eighty four years old (fourty six males and twenty six females) admitted in the Department of Emergency Medicine, University of Tokyo Hospital during the period from January, 1981 to April, 1986, were studied. Their underlying diseases were supratentorial primary brain lesions except two cases with asphyxias which progressed to brain death. ICP was continuously measured and CPP was calculated as the pressure gradient between the mean arterial blood pressure (MAP) and ICP. The direct carotid angiography was performed to follow the cerebral circulation. Fourty five patients were subjected to barbiturate (pentobarbital sodium) therapy. The degree of the intracranial filling staged as "Non-filling", "Siphon-filling", "Partial-filling", "Delayed-filling", "All-filling" correlated significantly with ICP and CPP. These relationships, however, disappeared once ICP exceeded MAP. When "Non-filling" angiogram was obtained, clinical signs had already showed brain death. On the other hand, minimal flow ("Siphon-filling", "Partial-filling", "Delayed-filling") were still demonstrated in six brain death cases while ICP was approaching its "peak" value. This study showed that clinical diagnosis of brain death preceded the Non-filling phenomenon, suggesting that, for the demonstration of the cerebral circulatory arrest, the angiograms should be performed after the clinical diagnosis of brain death was established and CPP became zero. The evaluation of the extremely slow and minimal filling is still a matter of discussion.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
17.
18.
Extirpated specimens of a squamous cell carcinoma from a human thigh were transplanted to the subcutaneous tissue of nude mice. Fourteen days later, the transplanted tumor masses were, again, extirpated from the nude mice. The transplanted chimera of the squamous cell carcinoma as seen with the electron microscope resembled the tumor cells before transplantation. It is concluded that ultrastructural investigation of transplanted chimera from squamous cell carcinoma cases may be useful for examining the site of action and clinical effects of anticancer drugs on this kind of tumor.  相似文献   
19.
20.
AIMS: To investigate the localisation of Helicobacter pylori antigens and the expression of human heat shock proteins (HSP) in stomachs affected by MALT lymphoma. METHODS: Surgically resected stomachs from 24 patients with MALT lymphoma were immunostained with anti-H pylori rabbit antibodies (ORP-1 and ORP-2) and anti-human HSP60 mouse monoclonal antibodies (mAb) (LK-1 and LK-2). RESULTS: Follicular dendritic cells of germinal centres in the stomachs affected by MALT lymphoma were immunostained with anti-H pylori polyclonal antibodies and with anti-human HSP60 mAb, as were the epithelial cells. None of the lymph node samples reacted. CONCLUSIONS: Human HSP60, which cross reacts with anti-H pylori polyclonal antibodies, is often expressed on follicular dendritic cells in gastric MALT lymphoma tissues and may be aetiologically relevant to lymphomagenesis of MALT lymphoma.  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