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   1330862篇
  免费   95894篇
  国内免费   2898篇
耳鼻咽喉   19739篇
儿科学   40202篇
妇产科学   38654篇
基础医学   186800篇
口腔科学   39768篇
临床医学   112211篇
内科学   261074篇
皮肤病学   30164篇
神经病学   106241篇
特种医学   53643篇
外国民族医学   435篇
外科学   207798篇
综合类   31009篇
现状与发展   6篇
一般理论   436篇
预防医学   91689篇
眼科学   31311篇
药学   99993篇
  2篇
中国医学   2987篇
肿瘤学   75492篇
  2018年   11745篇
  2015年   11873篇
  2014年   16688篇
  2013年   25242篇
  2012年   32999篇
  2011年   34872篇
  2010年   20731篇
  2009年   20226篇
  2008年   33574篇
  2007年   36678篇
  2006年   37261篇
  2005年   36017篇
  2004年   35092篇
  2003年   34066篇
  2002年   33591篇
  2001年   63617篇
  2000年   65325篇
  1999年   55387篇
  1998年   14653篇
  1997年   13460篇
  1996年   12938篇
  1995年   12221篇
  1994年   11468篇
  1992年   42702篇
  1991年   41268篇
  1990年   40530篇
  1989年   39523篇
  1988年   36926篇
  1987年   36390篇
  1986年   34871篇
  1985年   33092篇
  1984年   24783篇
  1983年   20982篇
  1982年   12605篇
  1981年   11503篇
  1980年   10710篇
  1979年   23863篇
  1978年   17016篇
  1977年   14759篇
  1976年   13331篇
  1975年   15220篇
  1974年   18042篇
  1973年   17535篇
  1972年   16792篇
  1971年   15697篇
  1970年   14876篇
  1969年   14322篇
  1968年   13439篇
  1967年   11990篇
  1966年   11241篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
113.

Background

Observational studies of the relative effectiveness of influenza vaccines are essential for public health decision making. Their estimates, however, are subject to bias due to unmeasured confounders. Instrumental variable (IV) methods can control for observed and unobserved confounders.

Methods

We used linked electronic medical record databases in the Veterans Health Administration (VHA) as well as Medicare administrative files to examine the relative vaccine effectiveness (rVE) of high-dose influenza vaccine (HD) versus standard-dose influenza vaccines (SD) in preventing hospitalizations among VHA-enrolled Veterans ≥65?years of age during 5 influenza seasons (2010–2011 through 2014–2015). Using multivariable IV Poisson regression modeling to address unmeasured confounding and bias, we analyzed the data by each season and through longitudinal analysis of all five seasons.

Findings

We included 3,638,924 person–influenza seasons of observation where 158,636 (4%) were among HD vaccine recipients and 3,480,288 (96%) were among SD vaccine recipients. Of the 1,728,562 Veterans, 1,702,824 (98.5%) were male and 1,299,412 (75%) were non-Hispanic white. Based on the longitudinal analysis of all five seasons, the IV-adjusted rVE estimate of HD vs. SD was 10% (95% CI, 8–12%) against all-cause hospitalization; 18% (95% CI, 15–21%) against cardiorespiratory-associated hospitalization; and 14% (95% CI, 6–22%) against influenza/pneumonia-associated hospitalization. The findings by season were similar.

Interpretation

Our analysis of VHA clinical data collected from approximately 1.7 million Veterans 65?years and older during five seasons demonstrates that high-dose influenza vaccine is more effective than standard-dose influenza vaccines in preventing influenza- or pneumonia-associated hospitalizations, cardiorespiratory hospitalizations, and all-cause hospitalizations.  相似文献   
114.
Choledochal cysts (CDCs) and biliary atresia (BA) are rare pediatric hepatobiliary anomalies that require surgical intervention due to increased risk of malignancy and liver failure, respectively. The underlying disease and operative procedures place patients at risk for long‐term complications, which may continue to affect them into adulthood. Lack of a transitional care model in the health‐care system potentiates the challenges they will face following aging out of their pediatric providers' care. We sought to elucidate the long‐term complications and challenges patients with CDCs and BA face, review the current literature regarding transitioning care, and propose guidelines aiding adult providers in continued care and surveillance of these patients. A literature review was performed to assess short‐term and long‐term complications after surgery and the current standards for transitioning care in patients with a history of CDCs and BA. While transitional programs exist for patients with other gastrointestinal diseases, there are few that focus on CDCs or BA. Generally, authors encourage medical record transmission from pediatric to adult providers, ensuring accuracy of information and compliance with treatment plans. Patients with CDCs are at risk for developing biliary malignancies, cholangitis, and anastomotic strictures after resection. Patients with BA develop progressive liver failure, necessitating transplantation. There are no consensus guidelines regarding timing of follow up for these patients. Based on the best available evidence, we propose a schema for long‐term surveillance.  相似文献   
115.
116.
117.
PurposeThe aim of this study was to determine how female age at the end of the reproductive spectrum effects success of natural cycle intrauterine insemination (IUI) or IUI in combination with ovarian stimulation.MethodsWe performed a retrospective cohort study of women 43 years of age and older at the time of IUI in a single academic fertility center between January 2011 and March 2018. Primary outcomes were both pregnancies and live births per cycle of IUI. Data are presented as percentage or mean ± SD. Fisher exact and chi-squared analyses were performed.ResultsThere were 9334 IUI cycles conducted during the study period. Of these cycles, 325 IUIs (3.5%) were for women aged 43 years and over at the time of insemination (43.6 ± 0.8, range 43 to 47 years). Analysis of these 325 IUI cycles revealed 5 biochemical pregnancies (1.5%) and only 1 live birth (0.3%). The pregnancy rate did not differ between IUIs using donor sperm (N = 1/49, 2.0%) compared to IUIs with partner sperm (N = 4/276, 1.4%). The pregnancy rate did not differ between IUIs with gonadotropins (N = 2/211, 0.9%), clomiphene or letrozole (N = 2/78, 2.6%), or natural cycle (N = 1/36, 2.8%).ConclusionsThe use of intrauterine inseminations in women 43 years of age and older is an ineffective treatment strategy. This is irrespective of the use of ovarian stimulation or donor sperm. Costly gonadotropin injections did not increase the chance of pregnancy nor did oral medication when compared to natural cycle IUIs.  相似文献   
118.
119.
120.
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