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   4681篇
  免费   258篇
  国内免费   21篇
耳鼻咽喉   23篇
儿科学   130篇
妇产科学   111篇
基础医学   566篇
口腔科学   90篇
临床医学   451篇
内科学   847篇
皮肤病学   94篇
神经病学   589篇
特种医学   106篇
外科学   507篇
综合类   19篇
一般理论   4篇
预防医学   512篇
眼科学   125篇
药学   290篇
中国医学   4篇
肿瘤学   492篇
  2023年   45篇
  2022年   99篇
  2021年   178篇
  2020年   123篇
  2019年   158篇
  2018年   167篇
  2017年   121篇
  2016年   136篇
  2015年   136篇
  2014年   178篇
  2013年   233篇
  2012年   366篇
  2011年   346篇
  2010年   221篇
  2009年   220篇
  2008年   276篇
  2007年   314篇
  2006年   301篇
  2005年   252篇
  2004年   229篇
  2003年   239篇
  2002年   165篇
  2001年   40篇
  2000年   32篇
  1999年   29篇
  1998年   48篇
  1997年   38篇
  1996年   23篇
  1995年   26篇
  1994年   19篇
  1993年   21篇
  1992年   9篇
  1991年   18篇
  1990年   13篇
  1989年   12篇
  1988年   12篇
  1987年   9篇
  1986年   7篇
  1985年   9篇
  1984年   6篇
  1983年   8篇
  1982年   22篇
  1981年   9篇
  1980年   4篇
  1978年   7篇
  1976年   5篇
  1975年   4篇
  1974年   5篇
  1973年   3篇
  1969年   3篇
排序方式: 共有4960条查询结果,搜索用时 15 毫秒
71.

The study examined differences in Greek and Greek‐American diets and disease patterns related to migration within the Mediterranean and from the Mediterranean to the United States. Data reported here discuss changes in food patterns and health‐related characteristics of two populations, both originating from the Greek island of Chios, residing either in Athens, Greece, or urban centers in the United States. Food consumption and medical history questionnaires were mailed to 2652 Chians residing in Athens, New York, and the San Francisco Bay region of California. A total of 381 usable responses were obtained; 79% of both the Chian Greek and the Chian Greek American sample were first generation emigrants. Food consumption data were analyzed as monthly frequencies of 49 food items and categories using factor analysis and discriminate analysis. Associations between location of residence and disease prevalence were examined using maximum‐likelihood logit analysis; results were controlled for age, Body Mass Index, physical activity, smoking habit, and socio‐economic status. After controlling for these potential confounders, as well as for presence of the conditions of elevated serum cholesterol, hypertension, and diabetes, Chian American men were identified at higher risk for cardiovascular disease (CVD) than their Athenian counterparts (p < 0.06). This difference in risk for CVD may be related to more frequent use of oils and fats other than olive oil, and less frequent use of olive oil. Among women, diabetes exhibited a positive association with Chian women residing in Athens (p < 0.09), which may be explained by a less frequent use of foods rich in complex carbohydrates by Athenian women than by their American counterparts.  相似文献   
72.

Background  

Prosthetic joint infection is an uncommon but serious complication of total knee arthroplasty (TKA). Control of infection after TKA is not always possible, and the resolution of infection may require an above-knee amputation (AKA).  相似文献   
73.
74.
Hepatitis B virus and hepatitis C virus infections in children   总被引:3,自引:0,他引:3  
PURPOSE OF REVIEW: To analyse the most relevant recent information on efficacy, duration and coverage of anti-hepatitis B virus vaccination; correlates of mother-to-child hepatitis C virus transmission; the natural history and outcomes of hepatitis B and C virus infections in children; the efficacy and safety of specific therapies. RECENT FINDINGS: Insufficient hepatitis B virus vaccine coverage and incomplete or delayed vaccine cycles need improvement in many countries. Hepatitis B virus mutants may explain some fulminant hepatitis in perinatally infected infants and vaccine failures. No interventions to prevent vertical hepatitis C virus transmission have been identified. Spontaneous clearance of hepatitis B is lower in children than in adults, while the rates appear to be similar for hepatitis C. The disease progression is slower for both infections in childhood. Several studies support the efficacy and safety of interferons and lamivudine in chronic hepatitis B or of interferons and ribavirin in chronic hepatitis C in children, but the optimal therapy remains unclear. SUMMARY: There are doubts as to the long-term persistence of anti-hepatitis B immunization in low-endemicity areas. Routine hepatitis C virus testing in pregnancy is not recommended as there are no available prophylactic measures. Although hepatitis B and C virus infections are usually asymptomatic or with mild manifestations in childhood, concerns around their long-term clinical impact suggest the need for early treatment. Children should preferably be treated in the context of targeted trials for a better understanding of the efficacy and tolerance of drugs currently used in adults.  相似文献   
75.
BACKGROUND: Most patients with hypertension require more than one agent to control blood pressure (BP). The purpose of this study was to assess the efficacy and safety of the angiotensin II receptor blocker olmesartan medoxomil in combination with hydrochlorothiazide (HCTZ). METHODS: This was a randomized, double-blind, factorial design study. After a placebo run-in period, eligible patients (n = 502) with a baseline mean seated diastolic blood pressure (SeDBP) of 100 to 115 mm Hg were randomized to one of 12 groups: placebo, olmesartan medoxomil monotherapy (10, 20, or 40 mg/day, HCTZ monotherapy (12.5 or 25 mg/day), or one of six groups of olmesartan medoxomil/HCTZ combination therapy. The primary endpoint was the change in mean trough SeDBP from baseline at week 8. Statistical analyses were conducted to determine whether at least one combination produced a larger reduction in SeDBP at week 8 than the individual corresponding component doses, but did not compare BP reductions with different combination doses. RESULTS: Olmesartan medoxomil plus HCTZ produced greater reductions in both SeDBP and seated systolic blood pressure (SeSBP) at week 8 than did monotherapy with either component. All olmesartan medoxomil/HCTZ combinations significantly reduced SeDBP and SeSBP compared with placebo in a dose-dependent manner. Reductions from baseline in mean trough SeSBP/SeDBP were 3.3/8.2 mm Hg, 20.1/16.4 mm Hg, and 26.8/21.9 mm Hg with placebo, olmesartan medoxomil/HCTZ 20/12.5 mg, and olmesartan medoxomil/HCTZ 40/25 mg, respectively. All treatments were well tolerated. CONCLUSIONS: Olmesartan medoxomil/HCTZ combination therapy produced BP reductions of up to 26.8/21.9 mm Hg and was well tolerated.  相似文献   
76.
77.
One of the obstacles to AIDS vaccine development is the variability of HIV-1 within individuals and within infected populations, enabling viral escape from highly specific vaccine induced immune responses. An understanding of the different immune mechanisms capable of inhibiting HIV infection may be of benefit in the eventual design of vaccines effective against HIV-1 variants. To study this we first compared the immune responses induced in Rhesus monkeys by using two different immunization strategies based on the same vaccine strain of HIV-1. We then utilized a chimeric simian/HIV that expressed the envelope of a dual tropic HIV-1 escape variant isolated from a later time point from the same patient from which the vaccine strain was isolated. Upon challenge, one vaccine group was completely protected from infection, whereas all of the other vaccinees and controls became infected. Protected macaques developed highest titers of heterologous neutralizing antibodies, and consistently elevated HIV-1-specific T helper responses. Furthermore, only protected animals had markedly increased concentrations of RANTES, macrophage inflammatory proteins 1α and 1β produced by circulating CD8+ T cells. These results suggest that vaccine strategies that induce multiple effector mechanisms in concert with β-chemokines may be desired in the generation of protective immune responses by HIV-1 vaccines.  相似文献   
78.
Objective: Placental anomalies visualized at midgestation by MRI are shown to be related to pregnancy outcome. We performed a prospective cohort study to investigate the influence of placental pathologies diagnosed with fetal MRI on long-term neurodevelopmental outcome.

Methods: In our hospital-based, cross-sectional study, all fetal MRI examinations of pregnancies with vascular placental pathology (i.e. infarction with/without hemorrhage, subchorionic thrombi/hemorrhages, intervillous thrombi/hemorrhages or retroplacental hematoma) between 2003 and 2007 were included. The extent of the pathology was expressed as the percentage of abnormality related to the whole placental volume. Pathohistological reports were correlated to MRI findings. Infants were prospectively investigated using Bayley developmental scales at the age of 2–3.5 years. Impairment was categorized as a Bayley scale two SDs below normal (<85 points).

Results: There were 31 singletons and 25 offspring of multiple pregnancies included in the analyses. Impairment rates were 32.2% in singletons and 32.0% in multiple births. No correlation between neuro/motordevelopmental outcome at 2–3.5 years and the type, extent or gestational week at the time of diagnoses of placental vascular pathologies was found.

Conclusion: The long-term outcome of children with vascular placental pathologies on fetal MRI was associated with a high impairment rate after 2–3.5 years, both on motor- and neurodevelopmental Bayley scales. Neurological impairment did not correlate with the extent of placental involvement, intrauterine growth restriction, gestational age at birth or multiple state.  相似文献   

79.

OBJECTIVE:

to test a theoretical model based on the Parent-Based Expansion of the Theory of Planned Behavior examining relation between selected parental, teenager and cultural variables and Latino teenagers'' intentions to engage in sexual behavior.

METHOD:

a cross-sectional correlational design based on a secondary data analysis of 130 Latino parent and teenager dyads.

RESULTS:

regression and path analysis procedures were used to test seven hypotheses and the results demonstrated partial support for the model. Parent familism and knowledge about sex were significantly associated with parents'' attitudes toward sexual communication with their teenagers. Parent Latino acculturation was negatively associated with parents'' self-efficacy toward sexual communication with their teenagers and positevely associated with parents'' subjective norms toward sexual communication with their teenagers. Teenager knowledge about sex was significantly associated with higher levels of teenagers'' attitudes and subjective norms about sexual communication with parents. Only the predictor of teenagers'' attitudes toward having sex in the next 3 months was significantly associated with teenagers'' intentions to have sex in the next 3 months.

CONCLUSION:

the results of this study provide important information to guide future research that can inform development of interventions to prevent risky teenager sexual behavior among Latinos.  相似文献   
80.
Objectives. We set out to assess the occurrence of new depression and anxiety diagnoses in women 3 years after they sought an abortion.Methods. We conducted semiannual telephone interviews of 956 women who sought abortions from 30 US facilities. Adjusted multivariable discrete-time logistic survival models examined whether the study group (women who obtained abortions just under a facility’s gestational age limit, who were denied abortions and carried to term, who were denied abortions and did not carry to term, and who received first-trimester abortions) predicted depression or anxiety onset during seven 6-month time intervals.Results. The 3-year cumulative probability of professionally diagnosed depression was 9% to 14%; for anxiety it was 10% to 15%, with no study group differences. Women in the first-trimester group and women denied abortions who did not give birth had greater odds of new self-diagnosed anxiety than did women who obtained abortions just under facility gestational limits.Conclusions. Among women seeking abortions near facility gestational limits, those who obtained abortions were at no greater mental health risk than were women who carried an unwanted pregnancy to term.There has been much interest in understanding the effects of abortion, one of the most commonly performed surgical procedures,1,2 on women’s mental health outcomes. Leading reviews on this topic have found no evidence of mental health harm from an abortion,3–6 with the exception of 1 review7 which has been critically refuted.5,8–11 These reviews have called for more research of women seeking abortion beyond the first trimester, longitudinal studies, studies that control for preexisting mental health conditions, and studies that compare women who have had an abortion to women who want an abortion but are unable to get one.3–5Most of the few longitudinal studies available have been conducted outside of the United States. A Danish population-based cohort study assessed the onset of a first psychiatric event before and up to 12 months after a first-trimester abortion and found no increased risk of mental disorders after abortion.12 A Norwegian study followed 120 women for 5 years and compared the psychological response of women who had first-trimester abortions to women who had miscarriages,13 finding no differences in depression or anxiety between the 2 groups.13 Fergusson et al. published a series of articles based on a longitudinal study conducted in New Zealand that suggested that abortion is associated with an increased risk of mental health problems.14,15 These studies, however, have a number of shortcomings that have been discussed elsewhere and may not be generalizable to the US setting.4 One of the few longitudinal US studies is a secondary analysis of the National Comorbidity Survey that compared the mental health outcomes of women who obtained abortions to women who gave birth.16 In this study, the predictive effect of abortion on mental health conditions disappeared when analyses controlled for mental health history.16In this article, we report on the first 3 years of a 5-year longitudinal study, the Turnaway Study, which was specifically designed to examine the psychological consequences of undergoing or being denied an abortion in the United States. Previous findings from the Turnaway Study have demonstrated that most women seeking abortions for financial-, timing-, or partner-related reasons17 commonly express feelings of relief after the abortion and feel that abortion was the right decision.18 The mental health symptom trajectories of women who sought an abortion differed little from those who were denied one; however, both improved over time.19 Our previous analysis19 assessed self-reported mental health symptoms at 5 discrete points in time over 2 years (potentially missing symptoms of anxiety and depression that may have occurred in between interview dates or after 2 years), and it did not assess women’s severity of symptoms or other circumstances that may have led to a clinical diagnosis of depression or anxiety. This study further contributes to the literature by assessing diagnoses of new depression and anxiety disorders that may have occurred in women at any point up to 3 years after having sought an abortion.  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