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   1130471篇
  免费   77607篇
  国内免费   3080篇
耳鼻咽喉   15801篇
儿科学   35680篇
妇产科学   30628篇
基础医学   160676篇
口腔科学   30609篇
临床医学   101128篇
内科学   214133篇
皮肤病学   25444篇
神经病学   84958篇
特种医学   45320篇
外国民族医学   207篇
外科学   170657篇
综合类   25715篇
现状与发展   8篇
一般理论   274篇
预防医学   77684篇
眼科学   25792篇
药学   90976篇
  27篇
中国医学   4437篇
肿瘤学   71004篇
  2021年   9611篇
  2019年   9285篇
  2018年   13170篇
  2017年   10339篇
  2016年   11575篇
  2015年   13476篇
  2014年   18023篇
  2013年   25428篇
  2012年   35098篇
  2011年   36710篇
  2010年   21794篇
  2009年   20298篇
  2008年   33285篇
  2007年   35378篇
  2006年   35862篇
  2005年   33940篇
  2004年   32366篇
  2003年   31077篇
  2002年   29725篇
  2001年   61429篇
  2000年   62641篇
  1999年   51923篇
  1998年   12931篇
  1997年   11403篇
  1996年   11384篇
  1995年   10648篇
  1994年   9649篇
  1993年   9065篇
  1992年   38295篇
  1991年   36691篇
  1990年   36141篇
  1989年   34627篇
  1988年   31176篇
  1987年   30312篇
  1986年   28486篇
  1985年   26684篇
  1984年   19361篇
  1983年   16271篇
  1982年   8913篇
  1979年   17195篇
  1978年   11537篇
  1977年   10312篇
  1976年   8924篇
  1975年   10151篇
  1974年   11732篇
  1973年   11343篇
  1972年   10819篇
  1971年   10154篇
  1970年   9296篇
  1969年   8967篇
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
131.
132.
Capillary malformation–arteriovenous malformation syndrome (CM‐AVM) is an autosomal dominant disorder caused by RASA1 mutations. The prevalence and phenotypic spectrum are unknown. Evaluation of patients with multiple CMs is challenging because associated AVMs can be life threatening. The objective of this study was to describe the clinical characteristics of children presenting with features of CM‐AVM to an academic pediatric dermatology practice. After institutional review board approval was received, a retrospective chart review was performed of patients presenting between 2009 and 2012 with features of CM‐AVM. We report nine cases. Presenting symptoms ranged from extensive vascular stains and cardiac failure to CMs noted incidentally during routine skin examination. All demonstrated multiple CMs, two had Parkes Weber syndrome, and two had multiple infantile hemangiomas. Seven patients had family histories of multiple CMs; three had family histories of large, atypical CMs. Six had personal or family histories of AVMs. Genetic evaluation was recommended for all and was pursued by six families; four RASA1 mutations were identified, including one de novo. Consultations with neurology, cardiology, and orthopedics were recommended. Most patients (89%) have not required treatment to date. CM‐AVM is an underrecognized condition with a wide clinical spectrum that often presents in childhood. Further evaluation may be indicated in patients with multiple CMs. This study is limited by its small and retrospective nature.  相似文献   
133.
134.
135.
136.
137.
138.

Objectives

Short successive periods of skeletal muscle disuse have been suggested to substantially contribute to the observed loss of skeletal muscle mass over the life span. Hospitalization of older individuals due to acute illness, injury, or major surgery generally results in a mean hospital stay of 5 to 7 days, during which the level of physical activity is strongly reduced. We hypothesized that hospitalization following elective total hip arthroplasty is accompanied by substantial leg muscle atrophy in older men and women.

Design and participants

Twenty-six older patients (75 ± 1 years) undergoing elective total hip arthroplasty participated in this observational study.

Measurements

On hospital admission and on the day of discharge, computed tomographic (CT) scans were performed to assess muscle cross-sectional area (CSA) of both legs. During surgery and on the day of hospital discharge, a skeletal muscle biopsy was taken from the m. vastus lateralis of the operated leg to assess muscle fiber type–specific CSA.

Results

An average of 5.6 ± 0.3 days of hospitalization resulted in a significant decline in quadriceps (?3.4% ± 1.0%) and thigh muscle CSA (?4.2% ± 1.1%) in the nonoperated leg (P < .05). Edema resulted in a 10.3% ± 1.7% increase in leg CSA in the operated leg (P < .05). At hospital admission, muscle fiber CSA was smaller in the type II vs type I fibers (3326 ± 253 μm2 vs 4075 ± 279 μm2, respectively; P < .05). During hospitalization, type I and II muscle fiber CSA tended to increase, likely due to edema in the operated leg (P = .10).

Conclusions

Six days of hospitalization following elective total hip arthroplasty leads to substantial leg muscle atrophy in older patients. Effective intervention strategies are warranted to prevent the loss of muscle mass induced by short periods of muscle disuse during hospitalization.  相似文献   
139.

Background

Treatment of advanced anal squamous cell cancer (SCC) is usually with the combination of cisplatin and 5-fluorouracil, which is associated with heterogeneous responses across patients and significant toxicity. We examined the safety and efficacy of a modified schedule, FOLFCIS (leucovorin, fluorouracil, and cisplatin), and performed an integrated clinical and genomic analysis of anal SCC.

Patients and Methods

We reviewed all patients with advanced anal SCC receiving first-line FOLFCIS chemotherapy – essentially a FOLFOX (leucovorin, fluorouracil, and oxaliplatin) schedule with cisplatin substituted for oxaliplatin – in our institution between 2007 and 2017, and performed deep sequencing to identify genomic markers of response and key genomic drivers.

Results

Fifty-three patients with advanced anal SCC (48 metastatic; 5 unresectable, locally advanced) received first-line FOLFCIS during this period; all were platinum-naive. The response rate was 48% (95% confidence interval [CI], 32.6%-63%). With a median follow-up of 41.6 months, progression-free survival and overall survival were 7.1 months (95% CI, 4.4-8.6 months) and 22.1 months (95% CI, 16.9-28.1 months), respectively. Among all patients with advanced anal SCC that underwent sequencing during the study period, the most frequent genomic alterations consisted of chromosome 3q amplification (51%) and mutations in PIK3CA (29%) and KMT2D (22%). No genomic alteration correlated with response to platinum-containing treatment. Although there were few cases, patients with human papillomavirus-negative anal SCC did not appear to benefit from FOLFCIS, and all harbored distinct genomic profiles with TP53, TERT promoter, and CDKN2A mutations.

Conclusions

FOLFCIS appears effective and safe as first-line chemotherapy in patients with advanced anal SCC and represents an alternative treatment option for these patients.  相似文献   
140.
ABSTRACT

Objectives: The present study investigated the relationships of enculturation and depressive symptoms with health risk behavior engagement in Mexican-American college students and examined how these relationships differed by gender. Previous research has noted consistent gender differences in health risk behavior (e.g. alcohol use, substance use, and risky sexual behavior) among Latina/os, and emphasized the role of U.S. acculturation in this difference. Research examining the role of heritage cultural retention (i.e. enculturation), and including the added influence of mental health variables, such as depressive symptoms, is currently lacking. This study sought to address this gap.

Design: A large sample (N?=?677) of Mexican-American college students from four universities (located in New York, California, Florida, and Texas) completed an online questionnaire assessing health risk behaviors and corresponding variables.

Results: We found that males who endorsed more behavioral enculturation and depressive symptoms were more likely to engage in health risk behavior than all others in the sample. Contrary to previous literature, no relationship was found between behavioral enculturation and health risk behavior in females.

Conclusion: The current study found behavioral enculturation to be associated with depressive symptoms, and in turn with health risk behaviors among the males in our sample. Additional research will be needed to identify the mechanism underlying the relationship between enculturation and depressive symptoms as well as between depressive symptoms and risky behavior.  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