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   22223篇
  免费   2197篇
  国内免费   42篇
耳鼻咽喉   371篇
儿科学   636篇
妇产科学   362篇
基础医学   3202篇
口腔科学   581篇
临床医学   2234篇
内科学   4042篇
皮肤病学   282篇
神经病学   1704篇
特种医学   695篇
外科学   3321篇
综合类   528篇
一般理论   26篇
预防医学   2435篇
眼科学   659篇
药学   1431篇
中国医学   16篇
肿瘤学   1937篇
  2021年   295篇
  2020年   171篇
  2019年   262篇
  2018年   345篇
  2017年   265篇
  2016年   300篇
  2015年   329篇
  2014年   476篇
  2013年   702篇
  2012年   1022篇
  2011年   1006篇
  2010年   549篇
  2009年   493篇
  2008年   887篇
  2007年   995篇
  2006年   959篇
  2005年   982篇
  2004年   878篇
  2003年   884篇
  2002年   794篇
  2001年   754篇
  2000年   764篇
  1999年   671篇
  1998年   263篇
  1997年   245篇
  1996年   243篇
  1995年   213篇
  1994年   224篇
  1993年   200篇
  1992年   581篇
  1991年   514篇
  1990年   482篇
  1989年   503篇
  1988年   436篇
  1987年   423篇
  1986年   399篇
  1985年   386篇
  1984年   319篇
  1983年   259篇
  1982年   198篇
  1981年   210篇
  1979年   292篇
  1978年   260篇
  1977年   176篇
  1975年   187篇
  1974年   253篇
  1973年   195篇
  1972年   203篇
  1971年   169篇
  1969年   165篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
PurposeAlthough an adult model of patient-provider mutual exchange of information has been proposed, there is no guiding model for adolescents or measurement methodology. Our purpose was to develop a new scale of patient-provider interaction for adolescents accessing reproductive health care and at risk for sexually transmitted diseases (STDs) and human immunodeficiency virus (HIV), and assess the reliability and validity of the scale.MethodsThe Adolescent Patient-Provider Interaction Scale (APPIS) was developed from the Roter and Hall theory of doctor-patient relationships, previously validated adolescent satisfaction and communication scales, and focus group and individual elicitation interviews. To assess construct validity, the new nine-item APPIS was compared with the satisfaction scale used by the Young Adult Health Care Survey (YAHCS), and Kahn’s Provider Communication Scale. Pearson correlation coefficients were used to examine convergence across scales, and factor analysis of the APPIS was performed.ResultsThe study recruited 192 African American girls aged 17.9 ± 1.7 years (range 15–21 years) from three sites: a county STD clinic (n = 51), urban adolescent clinic (n = 99), and a family planning clinic (n = 42). Most participants (85%) rated their overall health care highly (≥ 7 on a 10-point scale); 49% felt that both the provider and patient were “in charge” of the visit, and 88% “strongly agreed” or “agreed” that there was an equal “exchange of information” during the visit. The APPIS showed good internal consistency (Cronbach alpha = .75), and moderate convergence with the six-item YAHCS scale (r = .57, p < .001) and seven-item Kahn scale (r = .48, p < .001). Three factors emerged from exploratory factor analyses, supporting our conceptualization of patient-provider interaction as being multi-dimensional.ConclusionsA new theory-based scale of adolescent patient-provider interaction compares favorably with previous scales of health care satisfaction and communication. The new APPIS may be useful for evaluating approaches to improve health care outcomes for adolescents at-risk for STDs and HIV.  相似文献   
52.
The cognitive dimension of mental energy can be assessed by tests of vigilance and choice reaction time. These behaviors are relatively simple cognitive functions and can be measured with precision and reliability if carefully designed and implemented tests are used. Because the concept of mental energy is still evolving, the selection of appropriate tests to assess it must be tentative. However, vigilance and choice reaction time seem to have the necessary psychometric properties for assessing mental energy, including construct, predictive content, and face validity. Tests of reaction time and vigilance are correlated with questionnaires that measure mood states corresponding to mental energy—such as sleepiness, fatigue, and alertness—in the expected manner and are of approximately equivalent sensitivity.  相似文献   
53.
54.
Apolipoprotein E (apoE, protein; APOE, gene) is the major lipid-transport protein in the brain and plays an important role in modulating the outcome and regenerative processes after acute brain injury. The aim of the present study was to determine if gene transfer of the epsilon3 form of APOE improves outcome in a murine model of transient focal cerebral ischaemia. Mice received an intrastriatal injection of vehicle, a second-generation adenoviral vector containing the green fluorescent protein gene (Ad-GFP) or a vector containing the APOE epsilon3 gene (Ad-APOE) 3 days before 60 mins focal ischaemia. Green fluorescent protein expression was observed in cells throughout the striatum and subcortical white matter indicating successful gene transfer and expression. ApoE levels in the brain were significantly increased after Ad-APOE compared with Ad-GFP or vehicle treatment. Ad-APOE treatment reduced the volume of ischaemic damage by 50% compared with Ad-GFP or vehicle treatment (13+/-3 versus 29+/-4 versus 27+/-5 mm(3)). The extent of postischaemic apoE immunoreactivity was enhanced in Ad-APOE compared with Ad-GFP or vehicle treated mice. These results show the ability of APOE gene transfer to markedly improve outcome after cerebral ischaemia and suggest that modulating apoE levels may be a potential strategy in human stroke therapy.  相似文献   
55.
Complications following free tissue transfer have been well established in the literature. Common and rare causes of free flap failure must be addressed by the treating surgeon when microvascular patency is threatened. With the evolution and prevalence of microsurgery, ‘rare’ causes of free flap failure will become increasingly frequent. A high index of suspicion must be established in patients with multiple failed operative interventions. A case of recurrent free flap failure secondary to heparin-induced thrombocytopenia is presented in a patient with a history of squamous cell carcinoma of the floor of the mouth, and a long-standing history of alcohol and tobacco consumption.  相似文献   
56.
57.
Analysis of epidermal growth factor receptor (EGFr) and estrogen receptor (ER) was performed on tumor samples from 231 patients with operable breast cancer followed for up to 6 years after surgery. The median duration of follow-up in patients still alive at the time of analysis was 45 months. Thirty-five percent of patients (82) had tumors greater than 10 fmol/mg of 125I-EGF binding (EGFr+) and 47% (109) had cystolic ER concentration greater than 5 fmol/mg (ER+), with a marked inverse relationship between EGFr and ER (P less than .00001). EGFr was second only to axillary-node status as a prognostic marker for all patients in terms of both relapse-free and overall survival in univariate analysis (P less than .001, log-rank EGFr + v EGFr-). For patients with histologically negative axillary nodes, EGFr was superior to ER in predicting relapse and survival (P less than .01 and P less than .005, respectively, compared to P less than .1 and P less than .1, log-rank). In a multivariate (Cox model) analysis, only EGFr--out of EGFr, ER, size, and grade--was predictive for either relapse-free or overall survival for patients with node-negative disease (P = .052 and P = .026, respectively). One hundred eighty-seven case patients in the series were assessed for neu expression immunochemically, and 31 were positive. There was a highly significant increased risk of relapse and death in the positive group. In patients with otherwise good prognostic markers (ER+, node-negative, well-differentiated tumors), neu expression predicted for significantly worsened overall survival.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
58.
59.
The efficiency of the direct detection of Mycoplasma pneumoniae in respiratory exudates by an antigen capture, indirect enzyme immunoassay (Ag-EIA), has been compared with its detection with a cDNA probe ('Gen-Probe assay') directed against the specific ribosomal RNA sequences of the organism ('Mycoplasma pneumoniae Rapid Diagnostic System', Gen-Probe, San Diego, California). Both assays showed excellent specificity against a range of mycoplasma species suspended in negative nasopharyngeal aspirates; only M. pneumoniae and M. genitalium reacted. In experiments with graded doses of viable M. pneumoniae cells suspended in negative nasopharyngeal aspirate, the Gen-Probe assay was more sensitive than Ag-EIA; detection limits were respectively 2 X 10(3) c.f.u./ml (3.2 X 10(5) genomes) and 2.5 X 10(4) c.f.u./ml (4 X 10(6) genomes); detection levels 10-100 times less sensitive than culture. The two assays were also tested on nasopharyngeal aspirates or sputum specimens from 90 patients with respiratory infection; 67 of these were culture- or seronegative for M. pneumoniae and 23 were culture- or seropositive. Ag-EIA detected 21 (91%) of the latter but the Gen-Probe assay detected only 5 (22%). Both assays were negative with the 67 culture-/sero-negatives; there were no Gen-Probe assay positive/Ag-EIA negatives. Overall, it is concluded that although Ag-EIA and the Gen-Probe assay are effective substitutes for culture as a diagnostic procedure, there is a significant problem with samples which are culture-negative and from patients who have good serological evidence of current infection. Possible reasons for the disparity between the two assays are advanced.  相似文献   
60.
Cerebral ischemia induces the expression of a number of proteins that may have an important influence on cellular injury. The purpose of this study was to compare the regional effects of hypoxia-ischemia on the expression of the proto-oncogene, c-fos, and the heat shock protein-70 (HSP-70) gene in developing brain. Unilateral hypoxia-ischemia was produced in the brain of immature rats (7, 15, and 23 days after birth) using a combination of carotid artery ligation and systemic hypoxia (8% O2). After recovery for 2 and 24 h, the regional expression of c-fos and HSP-70 mRNA was determined using in situ hybridization. Littermates were permitted to recover for 1 week for assessment of histologic injury. Hypoxia-ischemia increased the expression of both c-fos and HSP-70 mRNA, but the topography of expression varied with the age of the animal as well as the mRNA species. In the 7-day-old group, expression of c-fos at 2 h increased in multiple regions of the ipsilateral hemisphere in nearly one-half of the animals, while HSP-70 mRNA was not expressed until 24 h and, then, predominantly in the hippocampus. In 15- and 23-day-old rats, expression of c-fos was increased at 2 h in the entorhinal cortex and in the dendritic field of the upper blade of the hippocampal dentate gyrus, while HSP-70 mRNA was prominently expressed in neocortex and the cell layers of the hippocampus. Interestingly, the strong expression of HSP-70 mRNA in dentate granule cells did not occur in the innermost layer of cells.(ABSTRACT TRUNCATED AT 250 WORDS)  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