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   16023篇
  免费   955篇
  国内免费   88篇
耳鼻咽喉   100篇
儿科学   383篇
妇产科学   456篇
基础医学   1974篇
口腔科学   318篇
临床医学   1546篇
内科学   3713篇
皮肤病学   219篇
神经病学   1744篇
特种医学   700篇
外科学   2376篇
综合类   68篇
一般理论   6篇
预防医学   1107篇
眼科学   297篇
药学   898篇
中国医学   33篇
肿瘤学   1128篇
  2024年   23篇
  2023年   193篇
  2022年   288篇
  2021年   505篇
  2020年   387篇
  2019年   454篇
  2018年   536篇
  2017年   412篇
  2016年   504篇
  2015年   497篇
  2014年   675篇
  2013年   857篇
  2012年   1407篇
  2011年   1383篇
  2010年   727篇
  2009年   614篇
  2008年   1077篇
  2007年   1048篇
  2006年   923篇
  2005年   942篇
  2004年   811篇
  2003年   704篇
  2002年   632篇
  2001年   110篇
  2000年   82篇
  1999年   114篇
  1998年   137篇
  1997年   81篇
  1996年   93篇
  1995年   64篇
  1994年   51篇
  1993年   64篇
  1992年   66篇
  1991年   55篇
  1990年   45篇
  1989年   48篇
  1988年   42篇
  1987年   32篇
  1986年   35篇
  1985年   43篇
  1984年   31篇
  1983年   35篇
  1982年   17篇
  1981年   23篇
  1979年   17篇
  1972年   15篇
  1971年   20篇
  1970年   16篇
  1969年   15篇
  1968年   22篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
The acute effects of cyclosporin (CsA, 20 mg(kg i.v.) and rapamycin (RAPA, 5 mg(kg i.v.) on glomerular dynamics were separately investigated by renal micropuncture in two groups of intact rats (group CsA and RAPA, respectively) and compared with vehicle-treated rats, used as controls (group CON). Left kidney glomerular filtration rate (GFR) was decreased by CSA (-35% vs. CON, P<0.05), but was not affected by RAPA (-14% vs. CON, NS), whereas the single-nephron GFR (SNGFR) was significantly decreased in both groups (-40% in CsA, P<0.01 and -26% in RAPA, P<0.05 vs. CON). In both groups glomerular plasma flow (GPF) was significantly reduced vs. CON (CsA: -48%, and RAPA: -25%) due to the increase in both afferent (Ra) and efferent (Re) glomerular resistances: group CSA showed a prevalent rise in Re (+98% vs. CON, P<0.001) than in Ra (+66%, P<0.001); in group RAPA the increment was modest and similar in Ra and Re (+33 and +32%, respectively, NS versus CON). A further group of rats was studied in which L-Arginine (ARG), the precursor of nitric oxide (NO), was administered (2.5 mg/Kg/min iv) with RAPA (group ARG). ARG limited the rise in Ra and Re, thereby preserving GPF; nevertheless, SNGFR remained low (-26% vs. CON, P<0.05) due to the decrease in the effective filtration pressure (-26% vs. CON). These data demonstrate that: (1) CsA is nephrotoxic at immunosuppressive doses; (2) RAPA, even at huge doses, has marginal effects on renal and glomerular dynamics; (3) the ARG-NO pathway is only partially involved in the vasoconstriction of superficial nephrons after RAPA administration.  相似文献   
102.
Prognostic value of CD40 in adult soft tissue sarcomas.   总被引:4,自引:0,他引:4  
PURPOSE: The purpose is to evaluate the expression of CD40, a membrane protein predominantly expressed on B cells, dendritic cells, and macrophages, in a series of adult soft tissue sarcomas and to test its possible prognostic value. EXPERIMENTAL DESIGN: CD40 expression was studied by immunohistochemistry. Correlations with other baseline characteristics of patients and tumors were analyzed with chi(2) test. The prognostic value was studied with univariable and multivariable analysis adjusted by age, sex, tumor size, grade, location, and distant metastases. RESULTS: Eighty-two patients, between January 1994 and May 2001, were analyzed. Membrane or cytoplasmic staining for CD40 protein was absent in 30% of the tumors but present in <10% of cells in 22 (27%), in 10% to 50% in 23 (28%), and in >50% of cells in 12 (15%) tumors. There was no correlation between CD40 expression and age, sex, size, grade, and location of the primary tumor and distant metastases. With 61 patients (74.4%) progressed and 31 (37.8%) dead, CD40 expression was a significant prognostic factor for disease-free and overall survival at univariable and multivariable analysis. Patients with tumors expressing CD40 in >50% of cells had a dramatically unfavorable prognosis with median disease-free and overall survival of 7 and 17 months, respectively, and hazard ratios of relapse and death as compared with patients with CD40-negative tumors of 2.89 (95% confidence interval: 1.26-6.60) and 6.92 (95% confidence interval: 2.18-22.0), respectively. CONCLUSIONS: These data suggest that expression of CD40 protein in >50% of cells might indicate an unfavorable prognosis in adult soft tissue sarcomas.  相似文献   
103.
BACKGROUND AND PURPOSE: Interstitial implants for brachytherapy boost in the breast conserving therapy of breast cancer can be performed in two ways; implants during the tumor excision (per-operative implants) or after the external beam therapy (delayed interstitial implants). Differences in cosmetic outcome were investigated. PATIENTS AND METHODS: Cosmetic results in 47 patients having a per-operative implant were compared to 123 patients having a delayed interstitial implant in a matched case-control study. Cosmesis was scored on a four-point-scale varying from 0 (excellent) to 3 (poor). RESULTS: After mean follow-up of 63 months, three observers found no difference in cosmetic outcome between the two groups after adjustment for variables found to be related with cosmesis (difference in mean score 0.50, P=0.26). Implant volume at 100% isodose was not found to differ (P=0.084) between the per-operative group (mean 102 cm3, S.D. 34 cm3) and the delayed group (mean 93 cm3, S.D. 29 cm3). CONCLUSIONS: Performing per-operative implants has not led to smaller implants. The method of performing brachytherapy does not result in marked differences in cosmetic outcome.  相似文献   
104.
PURPOSE: p27(Kip1) is a member of the Cip1/Kip1 family of cyclin-dependent kinase inhibitors and is a potential tumor suppressor gene. Low levels of p27 are associated with poor prognosis in a variety of gynecological tumors, including breast, ovarian, and cervical carcinomas. The role of p27 in endometrial cancer remains controversial. EXPERIMENTAL DESIGN: In the present study, p27 protein expression was investigated by immunohistochemistry in a series of 217 endometrial adenocarcinomas and, where present, in synchronous normal endometrium, simple and complex hyperplasia (with or without atypia), and cystic atrophy. The relationship between p27 expression and clinical outcome was also evaluated. RESULTS: Immunohistochemical analysis revealed a significant loss of p27 expression from normal (33%) through hyperplastic endometrium (50%) to endometrial adenocarcinomas (71%; P 相似文献   
105.
We studied variability in doxorubicin pharmacokinetics in 24 patients with abnormal liver biochemistry tests. Blood samples were collected after the first cycle of single-agent doxorubicin given as an i.v. bolus and plasma levels were measured by high-performance liquid chromatography. The relationship between doxorubicin clearance (dose/AUC) and liver biochemistry tests (AST, bilirubin, albumin, alkaline phosphatase and indocyanine green clearance) was investigated. Patients with a raised bilirubin level had reduced doxorubicin clearance, but there was no clear relationship between the extent of this elevation and the reduction in doxorubicin clearance. Doxorubicin clearance was lower in patients with an isolated increase in AST than in those with normal liver biochemistry, but this difference was not statistically significant. Nevertheless, there was a significant correlation between reduced doxorubicin clearance and both raised serum AST levels and low indocyanine green clearance. These pharmacokinetic data suggest that current dose reductions based solely on the extent to which bilirubin is elevated may not be optimal. Received: 20 October 1997 / Accepted: 20 January 1998  相似文献   
106.
107.
Specific language impairment is sometimes thought to be associated with concurrent difficulties in the area of social and behavioral development (N. Botting and G. Conti-Ramsden, 2000; D. P. Cantwell and L. Baker, 1987; M. Fujiki, B. Brinton, and C. Todd, 1996; S. Redmond and M. Rice, 1998). The present study follows a group of 242 children, initially studied at age 7 years when they attended language units in England, and assesses their social and behavioral status at age 11 years. In total, 64% of the children were found to have scores on the Rutter behavioral questionnaire (M. Rutter, 1967) of 9 or above (clinical threshold); 34% scored over the threshold for the Strengths and Difficulties questionnaire (R. Goodman, 1997); and 39% scored below average on the Peer Competence subscale of the Harter Perceived Competence Scale (S. Harter and R. Pike, 1984). On further analysis, these generalized difficulties were characterized mainly by poor social competence. In addition, 36% of the cohort were at risk of being regular targets for victimization compared to 12% of a comparison sample of typically developing peers. Few associations were found between social outcome and other measures, including nonverbal intelligence, overall linguistic skill, gender, and longitudinal measures taken previously. Importantly, however, pragmatic language difficulties measured on the Children's Communication Checklist (D. V. M. Bishop, 1998) were most strongly related to poor social outcome and to expressive language related to victimization.  相似文献   
108.
The optometric profession in the UK has a major role in the detection, assessment and management of ocular anomalies in children between 5 and 16 years of age. The role complements a variety of associated screening services provided across several health care sectors. The review examines the evidence-base for the content, provision and efficacy of these screening services in terms of the prevalence of anomalies such as refractive error, amblyopia, binocular vision and colour vision and considers the consequences of their curtailment. Vision screening must focus on pre-school children if the aim of the screening is to detect and treat conditions that may lead to amblyopia, whereas if the aim is to detect and correct significant refractive errors (not likely to lead to amblyopia) then it would be expedient for the optometric profession to act as the major provider of refractive (and colour vision) screening at 5-6 years of age. Myopia is the refractive error most likely to develop during primary school presenting typically between 8 and 12 years of age, thus screening at entry to secondary school is warranted. Given the inevitable restriction on resources for health care, establishing screening at 5 and 11 years of age, with exclusion of any subsequent screening, is the preferred option.  相似文献   
109.
110.
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