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   3749篇
  免费   198篇
  国内免费   2篇
耳鼻咽喉   157篇
儿科学   215篇
妇产科学   36篇
基础医学   372篇
口腔科学   153篇
临床医学   342篇
内科学   660篇
皮肤病学   42篇
神经病学   531篇
特种医学   66篇
外科学   485篇
综合类   19篇
一般理论   4篇
预防医学   288篇
眼科学   70篇
药学   172篇
中国医学   1篇
肿瘤学   336篇
  2023年   16篇
  2022年   33篇
  2021年   53篇
  2020年   39篇
  2019年   48篇
  2018年   73篇
  2017年   51篇
  2016年   89篇
  2015年   70篇
  2014年   89篇
  2013年   198篇
  2012年   204篇
  2011年   221篇
  2010年   125篇
  2009年   144篇
  2008年   227篇
  2007年   242篇
  2006年   206篇
  2005年   255篇
  2004年   252篇
  2003年   224篇
  2002年   218篇
  2001年   36篇
  2000年   34篇
  1999年   42篇
  1998年   58篇
  1997年   48篇
  1996年   36篇
  1995年   43篇
  1994年   40篇
  1993年   42篇
  1992年   44篇
  1991年   31篇
  1990年   26篇
  1989年   16篇
  1988年   17篇
  1987年   14篇
  1986年   25篇
  1985年   25篇
  1984年   20篇
  1983年   39篇
  1982年   44篇
  1981年   15篇
  1980年   26篇
  1979年   16篇
  1978年   19篇
  1977年   15篇
  1976年   15篇
  1975年   12篇
  1972年   10篇
排序方式: 共有3949条查询结果,搜索用时 15 毫秒
91.
92.
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   
93.
94.
95.
Conclusion The present findings show that all four types of histamine receptors (H1R, H2R, H3R, and H4R) are present in the inner ear, thus supporting the hypothesis that histamine plays a physiological role in the inner ear. Objective To analyse the presence of histamine receptors in the normal mouse inner ear. Methods CBA/J mice were used in this study. The localization of H1R, H2R, H3R, and H4R in the inner ear, i.e. cochlea, vestibular end organs, vestibular ganglion, and endolymphatic sac, was studied by real-time PCR and immunohistochemistry. Results The mRNA for each receptor sub-type was detected in the inner ear. In the immunohistochemical study, the organ of Corti, spiral ganglion, vestibular ganglion, vestibular sensory epithelium, and endolymphatic sac cells showed an immunofluorescent reaction to all histamine receptors.  相似文献   
96.
BACKGROUND: Versican, an extracellular matrix proteoglycan, has been noted to be expressed in several malignant tumours and has been suggested to play an important role in cancer development and tumour growth. AIMS: To investigate whether the versican expression level in the peritumoural stromal tissue of primary oral squamous cell carcinoma (OSCC) predicts relapse-free or disease-specific survival. Also, to study the associations between versican expression and several other clinicopathological variables, as well as tumour cell proliferation. METHODS: Immunohistochemistry was used to study the expression of versican and tumour cell proliferative activity in 139 OSCCs. All pertinent clinical data were collected retrospectively from the hospital records. RESULTS: In this cohort, versican expression did not correlate with the clinicopathological factors or tumour cell proliferation. In univariate analyses, higher risk for disease recurrence was associated with higher stromal versican expression score (p = 0.02), positive neck node status (p = 0.02), lower Karnofsky performance status (p = 0.03) and higher tumour cell proliferation index (p = 0.04). Increased disease-specific risk of death was associated with high stromal versican expression score (p = 0.005) higher T class (p = 0.002), positive neck node status (p<0.001), higher stage (p<0.001), poorer histological differentiation (p = 0.005), worse general condition of the patient (p = 0.049) and increased tumour cell proliferative index (p = 0.02). In multivariate disease-specific survival analysis, high stromal versican expression score (p = 0.048), poorer histological differentiation (p = 0.047) and higher stage (p = 0.002) independently predicted poorer disease outcome. CONCLUSIONS: In this cohort, increased stromal versican expression correlated with both increased risk for disease recurrence and shortened survival. High stromal versican expression may thus be considered an independent and adverse prognostic marker in OSCC.  相似文献   
97.
OBJECTIVE: To assess the extent and style of implementation of the Hypertension Guideline (HT Guideline) in Finnish primary health centres, and to identify a scale of contrasting implementation styles in the health centres (with the two ends of the scale being referred to as information implementers or disseminators respectively). DESIGN: A cross-sectional study. Development of a questionnaire and criteria for assessing the extent and style of implementation of the HT Guideline. SETTING: Primary healthcare. SUBJECTS: All head physicians and senior nursing officers in Finnish health centres (n =290). MAIN OUTCOME MEASURES: The extent of adoption of the HT Guideline in health centres and the characteristics associated with the implementation style. RESULTS: Responses were received from 410 senior medical staff (246 senior nursing officers and 164 head physicians) representing altogether 264 health centres (91%) in Finland. The HT Guideline had been introduced into clinical practice in most health centres (89%). The style of implementation varied widely between health centres: at opposite ends of the implementation scale were 21 implementer health centres, which used multiple implementation channels, and 23 disseminator health centres, which used few or no implementation channels. The implementers had typically larger population bases and had organized services around the family doctor system, while the disseminators were smaller and had organized services according to a traditional model (appointments could be with any doctor in the surgery). CONCLUSION: The Finnish HT Guideline has become well known in most health centres since being introduced into clinical practice. However, the style of implementation varies markedly between health centres.  相似文献   
98.
BACKGROUND: Whole-grain rye and wheat cereals contain high amounts of alkylresorcinols (ARs), phenolic lipids. ARs can be quantified in plasma. Two recently identified urinary AR metabolites, 3,5-dihydroxyphenylbenzoic acid (DHBA) and 3-(3,5-dihydroxyphenyl)-1-propanoic acid (DHPPA), may be useful as biomarkers of intake of whole-grain rye and wheat. METHODS: We evaluated 4 pretreatment protocols for quantifying urinary DHBA and DHPPA using HPLC coupled with a coulometric electrode array detector. Syringic acid was used as the internal calibrator. RESULTS: Measured urinary concentrations of DHBA and DHPPA were 0.8-115 micromol/L. The mean recoveries of all added concentrations were 85%-104% for DHBA and 86%-99% for DHPPA, depending on the degree of the purification. The protocol versions with less purification correlated well with the protocol including highest purification. The correlation coefficients (r(2)) were 0.9699-0.8153 for DHBA and 0.9854-0.8371 for DHPPA. CONCLUSION: Although the protocol with the most purification steps was most specific, all protocols were suitable for measuring DHBA and DHPPA in urine. The rapid protocol with simple hydrolysis could be used in large-scale clinical studies. Additional investigation is needed to clarify whether these metabolites are useful biomarkers of whole-grain intake and helpful in the exploration of its association with human diseases.  相似文献   
99.
Polymer nanocomposites used in underground cables have been of great interest to researchers over the past 10 years. Their preparation and the dispersion of the nanoparticles through the polymer host matrix are the key factors leading to their enhanced dielectric properties. Their important dielectric properties are breakdown strength, permittivity, conductivity, dielectric loss, space charge accumulation, tracking, and erosion, and partial discharge. An overview of recent advances in polymer nanocomposites based on LDPE, HDPE, XLPE, and PVC is presented, focusing on their preparation and electrical properties.  相似文献   
100.
The aim of this study was to continue our previously published work and to compare the different indirect diagnostic methods for hypolactasia with the lactase to sucrase ratio obtained by jejunal biopsy. The following tests were performed in 63 adult patients: the breath hydrogen test, the lactose tolerance test with ethanol (serum galactose measurement after oral lactose load with ethanol), the urinary lactose tolerance test (urinary galactose measurement after oral lactose load with ethanol), and the strip test (like the former but using a special test strip for urinary galactose). Specificities of all these tests were good (96-98%). The 3-h breath hydrogen test was less sensitive (69%) than the other methods (81-94%). The strip test is recommended for the general practitioner for the diagnosis of this common cause of abdominal complaints.  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