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   705212篇
  免费   50017篇
  国内免费   1296篇
耳鼻咽喉   9169篇
儿科学   23267篇
妇产科学   17611篇
基础医学   110467篇
口腔科学   20035篇
临床医学   63813篇
内科学   134263篇
皮肤病学   16161篇
神经病学   49495篇
特种医学   25753篇
外国民族医学   76篇
外科学   104558篇
综合类   14859篇
现状与发展   2篇
一般理论   160篇
预防医学   51492篇
眼科学   16298篇
药学   54034篇
  3篇
中国医学   2356篇
肿瘤学   42653篇
  2019年   5453篇
  2018年   7889篇
  2017年   6116篇
  2016年   6835篇
  2015年   7569篇
  2014年   10287篇
  2013年   15445篇
  2012年   20567篇
  2011年   21545篇
  2010年   12765篇
  2009年   11973篇
  2008年   20054篇
  2007年   21582篇
  2006年   21956篇
  2005年   20486篇
  2004年   20042篇
  2003年   18982篇
  2002年   18496篇
  2001年   36360篇
  2000年   36926篇
  1999年   30411篇
  1998年   7884篇
  1997年   6668篇
  1996年   6979篇
  1995年   6632篇
  1994年   6114篇
  1993年   5597篇
  1992年   23000篇
  1991年   22949篇
  1990年   22336篇
  1989年   22097篇
  1988年   20050篇
  1987年   19438篇
  1986年   18482篇
  1985年   17325篇
  1984年   12706篇
  1983年   10748篇
  1982年   5932篇
  1979年   11525篇
  1978年   8133篇
  1977年   6838篇
  1976年   6602篇
  1975年   7271篇
  1974年   8510篇
  1973年   8145篇
  1972年   7659篇
  1971年   7135篇
  1970年   6878篇
  1969年   6307篇
  1968年   5787篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Synthetic amorphous silica (SAS) in its nanosized form is now used in food applications although the potential risks for human health have not been evaluated. In this study, genotoxicity and oxidative DNA damage of two pyrogenic (NM‐202 and 203) and two precipitated (NM‐200 and ‐201) nanosized SAS were investigated in vivo in rats following oral exposure. Male Sprague Dawley rats were exposed to 5, 10, or 20 mg/kg b.w./day for three days by gavage. DNA strand breaks and oxidative DNA damage were investigated in seven tissues (blood, bone marrow from femur, liver, spleen, kidney, duodenum, and colon) with the alkaline and the (Fpg)‐modified comet assays, respectively. Concomitantly, chromosomal damage was investigated in bone marrow and in colon with the micronucleus assay. Additionally, malondialdehyde (MDA), a lipid peroxidation marker, was measured in plasma. When required, a histopathological examination was also conducted. The results showed neither obvious DNA strand breaks nor oxidative damage with the comet assay, irrespective of the dose and the organ investigated. Similarly, no increases in chromosome damage in bone marrow or lipid peroxidation in plasma were detected. However, although the response was not dose‐dependent, a weak increase in the percentage of micronucleated cells was observed in the colon of rats treated with the two pyrogenic SAS at the lowest dose (5 mg/kg b.w./day). Additional data are required to confirm this result, considering in particular, the role of agglomeration/aggregation of SAS NMs in their uptake by intestinal cells. Environ. Mol. Mutagen. 56:218–227, 2015. © 2014 Wiley Periodicals, Inc.  相似文献   
92.

Background

A history of childhood maltreatment and psychopathology are common in adults with obesity.

Objectives

To report childhood maltreatment and to evaluate associations between severity and type of childhood maltreatment and lifetime history of psychopathology among adults with severe obesity awaiting bariatric surgery.

Setting

Four clinical centers of the Longitudinal Assessment of Bariatric Surgery Research Consortium.

Methods

The Childhood Trauma Questionnaire, which assesses presence/severity (i.e., none, mild, moderate, severe) of physical abuse, mental abuse, physical neglect, mental neglect, and sexual abuse, was completed by 302 female and 66 male bariatric surgery patients. Presurgery lifetime history of psychopathology and suicidal ideation/behavior were assessed with the Structured Clinical Interview for DSM-IV and the Suicidal Behavioral Questionnaire-Revised, respectively. Presurgery lifetime history of antidepressant use was self-reported.

Results

Two thirds (66.6%) of females and 47.0% of males reported at least 1 form of childhood trauma; 42.4% and 24.2%, respectively, at greater than or equal to moderate severity. Among women, presence/greater severity of childhood mental or physical abuse or neglect was associated with a higher risk of history of psychopathology (i.e., major depressive disorder, posttraumatic stress disorder, other anxiety disorder, alcohol use disorder, binge eating disorder), suicidal ideation/behavior and antidepressant use (P for all ≤ .02). These associations were independent of age, race, education, body mass index, and childhood sexual abuse. Childhood sexual abuse was independently associated with a history of suicidal ideation/behavior and antidepressant use only (P for both ≤ .05). Statistical power was limited to evaluate these associations among men.

Conclusion

Among women with obesity, presence/severity of childhood trauma was positively associated with relatively common psychiatric disorders.  相似文献   
93.
94.
95.
96.
97.
FGFR–TACC, found in different tumor types, is characterized by the fusion of a member of fibroblast grown factor receptor (FGFR) tyrosine kinase (TK) family to a member of the transforming acidic coiled-coil (TACC) proteins. Because chromosome numerical alterations, hallmarks of FGFR–TACC fusions are present in many hematological disorders and there are no data on the prevalence, we studied a series of patients with acute myeloid leukemia and myelodysplastic syndrome who presented numerical alterations using cytogenetic traditional analysis. None of the analyzed samples showed FGFR3–TACC3 gene fusion, so screening for this mutation at diagnosis is not recommended.  相似文献   
98.
99.
100.
Traditionally, major complications and unanticipated admission/readmission rates were used to assess outcome after day surgery. However, in view of the relative absence of major complications the quality of recovery (QOR) should be considered one of the principal endpoints after day surgery. In our study, the level of QOR is defined by a combination of the Global Surgical Recovery (GSR) Index and the Quality of Life (QOL).The aim of this study was to analyze prevalence and predictors of QOR after day surgery on the fourth postoperative day.Elective patients scheduled for day surgery from November 2008 to April 2010 were enrolled in a prospective cohort study. Outcome parameters were measured by using questionnaire packages at 2 time points: 1 week preoperatively and 4 days postoperatively. Primary outcome parameter is the QOR and is defined as good if the GSR index >80% as well as the postoperative QOL is unchanged or improved as compared with baseline. QOR is defined as poor if both the GSR index ≤80% and if the postoperative QOL is decreased as compared with baseline. QOR is defined as intermediate in all other cases. Three logistic regression analyses were performed to determine predictors for poor QOR after day surgery.A total of 1118 patients were included. A good QOR was noted in 17.3% of patients, an intermediate QOR in 34.8%, and a poor QOR in 47.8% 4 days after day surgery. The best predictor for poor QOR after day surgery was type of surgery. Other predictors were younger age, work status, and longer duration of surgery. A history of previous surgery, expected pain (by the patient) and high long-term surgical fear were significant predictors of poor QOR in only 1 of 3 prediction models.The QOR at home 4 days after day surgery was poor in the majority of patients and showed a significant procedure-specific variation. Patients at risk for poor QOR can be identified during the preoperative period based on type of surgery, age, work status, and the duration of the surgery.  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