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   43980篇
  免费   4053篇
  国内免费   64篇
耳鼻咽喉   412篇
儿科学   1410篇
妇产科学   1066篇
基础医学   5419篇
口腔科学   851篇
临床医学   4691篇
内科学   8930篇
皮肤病学   548篇
神经病学   4158篇
特种医学   1534篇
外国民族医学   3篇
外科学   6443篇
综合类   887篇
一般理论   55篇
预防医学   4782篇
眼科学   756篇
药学   3024篇
中国医学   56篇
肿瘤学   3072篇
  2021年   547篇
  2020年   391篇
  2019年   773篇
  2018年   872篇
  2017年   598篇
  2016年   627篇
  2015年   739篇
  2014年   1123篇
  2013年   1693篇
  2012年   2345篇
  2011年   2396篇
  2010年   1403篇
  2009年   1253篇
  2008年   2214篇
  2007年   2399篇
  2006年   2323篇
  2005年   2261篇
  2004年   2137篇
  2003年   2048篇
  2002年   1959篇
  2001年   1074篇
  2000年   1125篇
  1999年   990篇
  1998年   489篇
  1997年   371篇
  1996年   413篇
  1995年   453篇
  1994年   388篇
  1993年   365篇
  1992年   775篇
  1991年   706篇
  1990年   683篇
  1989年   699篇
  1988年   598篇
  1987年   596篇
  1986年   591篇
  1985年   576篇
  1984年   504篇
  1983年   451篇
  1982年   347篇
  1981年   339篇
  1980年   270篇
  1979年   451篇
  1978年   352篇
  1976年   266篇
  1975年   276篇
  1974年   291篇
  1973年   333篇
  1972年   306篇
  1971年   273篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Purpose

To examine cross-sectional associations between food insecurity and 12-month eating disorders, mood disorders, and anxiety disorders among U.S. adults.

Methods

This study used data collected between 2001 and 2003 from 2914 participants in the National Comorbidity Survey-Replication, a nationally representative sample of U.S. adults (mean age = 44.9 years; 53.4% female). Twelve-month food insecurity was assessed with a modified version of the Short Form U.S. Household Food Security Scale. Twelve-month DSM-IV diagnoses of mental disorders were based on the World Health Organization Composite International Diagnostic Interview. Modified Poisson regression models were conducted, adjusting for age, sex, race/ethnicity, education, and income-to-poverty ratio.

Results

Food insecurity was experienced by 11.1% of participants. Food insecurity was associated with greater prevalence of bulimic-spectrum eating disorders (prevalence ratio [PR] = 3.81; 95% confidence interval [CI] 2.26–6.42), mood disorders (PR = 2.53; 95% CI 1.96–3.29), and anxiety disorders (PR = 1.69; 95% CI 1.39–2.07).

Conclusion

Results indicate that food insecurity is associated with a range of internalizing mental disorders, though these findings should be confirmed with contemporary data to reflect DSM-5 diagnostic updates and the economic effects of the COVID-19 pandemic. Findings from this study emphasize the need to expand food insecurity interventions and improve access to mental health services for food-insecure populations.

  相似文献   
2.
3.
4.
Background

There is evidence that prenatal stress and smoking during pregnancy both independently increase the risk of offspring psychopathology. Here we examine whether increased levels of self-reported stress is associated with increased smoking in a population of pregnant women, and whether prenatal smoking is associated with offspring psychiatric diagnoses independent of prenatal stress exposure.

Method

Using a longitudinal birth cohort, we used ordered logistic regressions to examine associations between maternal stress and smoking during pregnancy. We then used logistic regression analyses to examine associations between prenatal smoking and later offspring psychiatric disorders.

Results

A dose–response relationship was found between maternally reported stress and smoking during pregnancy. Pregnant women reporting severe stress were more likely to smoke compared to both the moderate stress and no stress groups, and those reporting moderate stress were significantly more likely to smoke compared to the no stress group. Smoking more than 5 cigarettes daily during pregnancy increased the risk of offspring personality disorder (OR 3.08, 95% CI 1.60–5.94) as well as developing any Axis 1 psychiatric disorder, inclusive of mood, anxiety and psychotic disorders (OR 1.45, 95% CI 1.04–2.04). After adjusting for parental psychiatric history and maternal self-reported stress during pregnancy, associations between smoking more than 5 cigarettes daily when pregnancy and offspring personality (OR 2.58 95% CI 1.32–5.06) disorder remained.

Conclusion

Exposure to cigarette smoking during gestation could impact a child’s mental health. Smoking during pregnancy is a prime target for preventative interventions as unlike most other environmental risk factors, it is very amenable to change.

  相似文献   
5.
Evidence regarding cancer risk after borderline ovarian tumors (BOTs) is limited. We conducted a nationwide cohort study examining the incidence of nonovarian cancers in women with serous or mucinous BOTs compared with the general female population with up to 41 years of follow-up. Through the nationwide Pathology Registry, we identified nearly 5000 women with BOTs (2506 serous and 2493 mucinous) in Denmark, 1978 to 2018. We computed standardized incidence ratios (SIRs) with 95% confidence intervals (CIs) as relative risk estimates of specific nonovarian cancers. Compared with general female population rates, women with serous BOTs had increased rates of particularly malignant melanoma (SIR = 1.9; 95% CI: 1.3-2.6), thyroid cancer (SIR = 3.0; 95% CI: 1.4-5.4) and myeloid leukemia (SIR = 3.2; 95% CI: 1.5-5.8), and women with mucinous BOTs had elevated rates of lung cancer (SIR = 1.7; 95% CI: 1.3-2.1), pancreatic cancer (SIR = 1.9; 95% CI: 1.2-2.9) and myeloid leukemia (SIR = 2.3; 95% CI: 0.9-4.7). We found no convincing association with neither breast nor colorectal cancer in women with BOTs. This is the first large nationwide study showing that women with specific types of BOTs have increased risks of several nonovarian cancers, likely due to some shared risk factors or genetic characteristics.  相似文献   
6.
7.
8.
PurposeTo determine whether change in shoulder position between internal rotation (IR) and external rotation (ER) during magnetic resonance arthrography (MRA) affects previously defined capsular measurements and to determine the utility of rotation in the diagnosis of instability.MethodsA retrospective study was conducted of patients who received a shoulder MRA with humeral IR and ER views. Patients with an arthroscopically confirmed diagnosis of instability and those with clinically stable shoulders, no history of instability, and no MRA findings of instability were identified and compared. Humeral rotation, glenoid retroversion, humeral head subluxation, capsular length, and capsular area using axial sequences of IR and ER views were recorded. Analysis compared IR, ER, and Δ capsular measurements between groups using independent t tests and univariate and multivariate regression.ResultsThirty-one subjects who were diagnosed with instability were included, along with 28 control subjects. Capsular length, capsular area, and humeral subluxations were significantly greater with ER compared with IR views (P < .001, P < .001, P < .001). Patients with instability displayed greater ER capsular length (P = .0006) and ER capsular area (P = .005) relative to controls. Multivariate logistic regression identified age, weight, sex, ER capsular length, and retroversion to be significant predictors of instability. ER capsular length independently predicts instability with 86% sensitivity and 84% specificity. Interobserver reliability using the intraclass correlation coefficient was rated good or excellent on all measurements.ConclusionVariance in humeral rotation during shoulder MRA significantly affects capsular measurements. Rotational views increase the utility of capsular measurements when assessing for instability, particularly capsular length and capsular area. The implementation of ER positioning enhances the ability to examine capsular changes of the shoulder joint and can assist in the diagnosis of instability.Level of EvidenceIII, retrospective comparative study  相似文献   
9.
ObjectiveThis study evaluates the cost-effectiveness of maternal acellular pertussis (aP) immunization in low- and middle-income countries using a dynamic transmission model.MethodsWe developed a dynamic transmission model to simulate the impact of infant vaccination with whole-cell pertussis (wP) vaccine with and without maternal aP immunization. The model was calibrated to Brazilian surveillance data and then used to project health outcomes and costs under alternative strategies in Brazil, and, after adjusting model parameter values to reflect their conditions, in Nigeria and Bangladesh. The primary measure of cost-effectiveness is incremental cost (2014 USD) per disability-adjusted life-year (DALY).ResultsThe dynamic model shows that maternal aP immunization would be cost-effective in Brazil, a middle-income country, under the base-case assumptions, but would be very expensive at infant vaccination coverage in and above the threshold range necessary to eliminate the disease (90–95%). At 2007 infant coverage (DTP1 90%, DTP3 61% at 1 year of age), maternal immunization would cost < $4,000 per DALY averted. At high infant coverage, such as Brazil in 1996 (DTP1 94%, DTP3 74% at 1 year), cost/DALY increases to $1.27 million. When the model’s time horizon was extended from 2030 to 2100, cost/DALY increased under both infant coverage levels, but more steeply with high coverage. The results were moderately sensitive to discount rate, maternal vaccine price, and maternal aP coverage and were robust using the 100 best-fitting parameter sets. Scenarios representing low-income countries showed that maternal aP immunization could be cost-saving in countries with low infant coverage, such as Nigeria, but very expensive in countries, such as Bangladesh, with high infant coverage.ConclusionA dynamic model, which captures the herd immunity benefits of pertussis vaccination, shows that, in low- and middle-income countries, maternal aP immunization is cost-effective when infant vaccination coverage is moderate, even cost-saving when it is low, but not cost-effective when coverage levels pass 90–95%.  相似文献   
10.
Journal of Autism and Developmental Disorders - Restricted interests and repetitive behaviors (RRBs) are core symptoms of autism spectrum disorder (ASD), and commonly occur in...  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