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   29398篇
  免费   1563篇
  国内免费   94篇
耳鼻咽喉   360篇
儿科学   1042篇
妇产科学   885篇
基础医学   3967篇
口腔科学   894篇
临床医学   2756篇
内科学   6281篇
皮肤病学   606篇
神经病学   2802篇
特种医学   1002篇
外科学   3711篇
综合类   160篇
一般理论   9篇
预防医学   2266篇
眼科学   619篇
药学   2081篇
中国医学   88篇
肿瘤学   1526篇
  2023年   223篇
  2022年   164篇
  2021年   668篇
  2020年   464篇
  2019年   626篇
  2018年   887篇
  2017年   690篇
  2016年   741篇
  2015年   762篇
  2014年   983篇
  2013年   1380篇
  2012年   2036篇
  2011年   2020篇
  2010年   1038篇
  2009年   960篇
  2008年   1655篇
  2007年   1779篇
  2006年   1715篇
  2005年   1793篇
  2004年   1608篇
  2003年   1607篇
  2002年   1529篇
  2001年   636篇
  2000年   610篇
  1999年   518篇
  1998年   179篇
  1997年   137篇
  1996年   133篇
  1995年   145篇
  1994年   131篇
  1993年   98篇
  1992年   296篇
  1991年   251篇
  1990年   208篇
  1989年   231篇
  1988年   176篇
  1987年   199篇
  1986年   181篇
  1985年   164篇
  1984年   99篇
  1983年   91篇
  1982年   67篇
  1981年   64篇
  1979年   111篇
  1978年   70篇
  1977年   81篇
  1975年   71篇
  1974年   77篇
  1973年   65篇
  1972年   60篇
排序方式: 共有10000条查询结果,搜索用时 21 毫秒
1.
The aim of this safety study in mice was to determine in vivo toxicity and biodistribution potential of a single and multiple doses of L-glutamic acid-g-p(HEMA) polymeric nanoparticles as a drug delivery system. The single dose did not cause any lethal effect, and its acute oral LD50 was >2.000 mg/kg body weight (bw). Multiple doses (25, 50, or 100 mg/kg bw) given over 28 days resulted in no significant differences in body and relative organ weights compared to control. These results are supported by biochemical and histological findings. Moreover, nanoparticle exposure did not result in statistically significant differences in micronucleus counts in bone marrow cells compared to control. Nanoparticle distribution was time-dependent, and they reached the organs and even bone marrow by hour 6, as established by ex vivo imaging with the IVIS® spectrum imaging system. In conclusion, L-glutamic acid-g-p(HEMA) polymeric nanoparticles appear biocompatible and have a potential use as a drug delivery system.KEY WORDS: biocompatibility, blood biochemistry, genotoxicity, histology, in vivo toxicity, micronucleus test, polymers  相似文献   
2.
3.
4.

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   
5.
Obesity is a risk factor for colorectal cancer. Yet, some research indicates that weight-reducing bariatric surgery also increases colorectal cancer risk. Our study was undertaken because current evidence examining bariatric surgery and risk of colorectal cancer is limited and inconsistent. This population-based cohort study included adults with a documented obesity diagnosis in Denmark, Finland, Iceland, Norway or Sweden in 1980–2015. The incidence of colorectal cancer in participants with obesity who had and had not undergone bariatric surgery was compared to the incidence in the corresponding background population by calculating standardized incidence ratios (SIR) with 95% confidence intervals (CI). Additionally, operated and nonoperated participants with obesity were compared using multivariable Cox regression, providing hazard ratios (HR) with 95% CIs adjusted for confounders. Among 502,772 cohort participants with an obesity diagnosis, 49,931(9.9%) underwent bariatric surgery. The overall SIR of colon cancer was increased after bariatric surgery (SIR 1.56; 95% CI 1.28–1.88), with higher SIRs ≥10 years postsurgery. The overall HR of colon cancer in operated compared to nonoperated participants was 1.13 (95% CI 0.92–1.39) and 1.55 (95% CI 1.04–2.31) 10–14 years after bariatric surgery. Bariatric surgery did not significantly increase the risk of rectal cancer (SIR 1.14, 95% CI 0.83–1.52; HR 1.08, 95% CI 0.79–1.49), but the risk estimates increased with longer follow-up periods. Our study suggests that bariatric surgery is associated with an increased risk of colon cancer, while the support for an increased risk of rectal cancer was weaker.  相似文献   
6.
7.
8.
IntroductionThe aim of this study was to compare the distribution and frequency of forensic medical events in a refugee group with that of the general population, and thus, extrapolate the problems encountered in the immigrant population.MethodsThose cases admitted to the emergency department (ED) for any reason that required a forensic examination between January 2016 and June 2018 were investigated retrospectively.ResultsA total of 310 refugees were admitted to the ED for forensic medical events. The most common nations of origin of the refugees were Iraq (n = 167), Syria (n = 65), and Afghanistan (n = 28). The median age of the refugees was 24 years old (interquartile range = 17–33). With regard to forensics, the most common reasons for the refugees to present to the ED were motor vehicle accidents 27.4%, assaults 25.8%, employment and industrial accidents 16.1%, and suicide attempts 10.3%. Other than suicide attempts, all of the forensic presentations were more common in the males. The outcomes of the refugee group were as follows: 92.3% were discharged, 5.8% were admitted to the hospital, 1% were admitted to the intensive care unit (ICU), and 1% were transferred. Suicide attempts were the most common reasons for the ICU admissions, while the most common reasons for the hospital admissions were orthopedic injuries.ConclusionIn general, the forensic event frequency in the refugee group was lower (p = 0.001); however, this was a single center study, and there could have been unrecorded cases due to an inability to access healthcare assistance, so these results may not be reliable.  相似文献   
9.
10.
Bundesgesundheitsblatt - Gesundheitsforschung - Gesundheitsschutz - Regulierungswissenschaftliche Organisationen wie das Bundesinstitut für Risikobewertung (BfR) sehen sich in ihrer...  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