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   1940篇
  免费   83篇
  国内免费   37篇
耳鼻咽喉   26篇
儿科学   100篇
妇产科学   32篇
基础医学   212篇
口腔科学   28篇
临床医学   143篇
内科学   553篇
皮肤病学   132篇
神经病学   47篇
特种医学   225篇
外科学   219篇
综合类   32篇
预防医学   121篇
眼科学   20篇
药学   64篇
中国医学   3篇
肿瘤学   103篇
  2021年   20篇
  2020年   11篇
  2019年   25篇
  2018年   19篇
  2017年   26篇
  2016年   25篇
  2015年   34篇
  2014年   55篇
  2013年   91篇
  2012年   48篇
  2011年   61篇
  2010年   63篇
  2009年   78篇
  2008年   60篇
  2007年   72篇
  2006年   66篇
  2005年   63篇
  2004年   41篇
  2003年   33篇
  2002年   53篇
  2001年   46篇
  2000年   32篇
  1999年   37篇
  1998年   90篇
  1997年   75篇
  1996年   83篇
  1995年   54篇
  1994年   65篇
  1993年   54篇
  1992年   22篇
  1991年   18篇
  1990年   29篇
  1989年   45篇
  1988年   47篇
  1987年   37篇
  1986年   31篇
  1985年   31篇
  1984年   26篇
  1983年   15篇
  1982年   21篇
  1981年   18篇
  1980年   15篇
  1979年   21篇
  1978年   15篇
  1977年   16篇
  1976年   16篇
  1975年   13篇
  1973年   21篇
  1972年   10篇
  1971年   11篇
排序方式: 共有2060条查询结果,搜索用时 15 毫秒
81.
82.
83.
84.
Parent‐of‐origin–dependent (epi)genetic factors are important determinants of prenatal development that program adult phenotype. However, data on magnitude and specificity of maternal and paternal genome effects on fetal bone are lacking. We used an outbred bovine model to dissect and quantify effects of parental genomes, fetal sex, and nongenetic maternal effects on the fetal skeleton and analyzed phenotypic and molecular relationships between fetal muscle and bone. Analysis of 51 bone morphometric and weight parameters from 72 fetuses recovered at day 153 gestation (54% term) identified six principal components (PC1–6) that explained 80% of the variation in skeletal parameters. Parental genomes accounted for most of the variation in bone wet weight (PC1, 72.1%), limb ossification (PC2, 99.8%), flat bone size (PC4, 99.7%), and axial skeletal growth (PC5, 96.9%). Limb length showed lesser effects of parental genomes (PC3, 40.8%) and a significant nongenetic maternal effect (gestational weight gain, 29%). Fetal sex affected bone wet weight (PC1, p < 0.0001) and limb length (PC3, p < 0.05). Partitioning of variation explained by parental genomes revealed strong maternal genome effects on bone wet weight (74.1%, p < 0.0001) and axial skeletal growth (93.5%, p < 0.001), whereas paternal genome controlled limb ossification (95.1%, p < 0.0001). Histomorphometric data revealed strong maternal genome effects on growth plate height (98.6%, p < 0.0001) and trabecular thickness (85.5%, p < 0.0001) in distal femur. Parental genome effects on fetal bone were mirrored by maternal genome effects on fetal serum 25‐hydroxyvitamin D (96.9%, p < 0.001) and paternal genome effects on alkaline phosphatase (90.0%, p < 0.001) and their correlations with maternally controlled bone wet weight and paternally controlled limb ossification, respectively. Bone wet weight and flat bone size correlated positively with muscle weight (r = 0.84 and 0.77, p < 0.0001) and negatively with muscle H19 expression (r = –0.34 and –0.31, p < 0.01). Because imprinted maternally expressed H19 regulates growth factors by miRNA interference, this suggests muscle‐bone interaction via epigenetic factors. © 2014 American Society for Bone and Mineral Research.  相似文献   
85.

Background

Early environmental exposures may help shape the development of the autonomic nervous system (ANS) and hypothalamic–pituitary–adrenal (HPA) axis, influencing vulnerability for health problems across the lifespan. Little is known about the role of maternal sensitivity in influencing the development of the ANS in early life.

Aims

To examine associations among maternal sensitivity and infant behavioral distress and ANS and HPA axis reactivity to the Repeated Still-Face Paradigm (SFP-R), a dyadic stress task.

Study design

Observational repeated measures study.

Subjects

Thirty-five urban, sociodemographically diverse mothers and their 6-month-old infants.

Outcome measures

Changes in infant affective distress, heart rate, respiratory sinus arrhythmia (RSA), and T-wave amplitude (TWA) across episodes of the SFP-R were assessed. A measure of cortisol output (area under the curve) in the hour following cessation of the SFP-R was also obtained.

Results

Greater maternal insensitivity was associated with greater infant sympathetic activation (TWA) during periods of stress and tended to be associated with greater cortisol output following the SFP-R. There was also evidence for greater affective distress and less parasympathetic activation (RSA) during the SFP-R among infants of predominantly insensitive mothers.

Conclusions

Caregiving quality in early life may influence the responsiveness of the sympathetic and parasympathetic branches of the ANS as well as the HPA axis. Consideration of the ANS and HPA axis systems together provides a fuller representation of adaptive versus maladaptive stress responses. The findings highlight the importance of supporting high quality caregiving in the early years of life, which is likely to promote later health.  相似文献   
86.
87.
BACKGROUND: Colorectal cancer is the third leading cause of cancer mortality in Western countries. Hereditary nonpolyposis colorectal cancer is the most common type of hereditary colorectal cancer, but its incidence remains controversial, ranging from 1 to 5%. OBJECTIVE: This present prospective, multicentre, nationwide study was aimed at compiling prominent epidemiological and clinical data with respect to hereditary non-polyposis colorectal cancer and other familial colorectal cancer forms in Spain, where information is lacking. METHODS: All patients with a de-novo diagnosis of colorectal cancer and who attended between November 2000 and October 2001 in 25 hospitals all over Spain were registered. Demographic, clinical and tumour-related characteristics of probands, and detailed family history, were obtained. RESULTS: A total of 1872 colorectal cancer patients were included. Clinical diagnosis of hereditary non-polyposis colorectal cancer was established in 46 (2.5%) patients according to the Amsterdam II criteria. Comparison between patients fulfilling either the Amsterdam I or the Amsterdam II criteria revealed no differences with respect to demographic, clinical and tumour-related characteristics. A total of 504 (27.0%) patients had a family history of hereditary non-polyposis colorectal cancer-related neoplasm not fulfilling the Amsterdam criteria (familial colorectal cancer), while 360 (19.2%) patients fulfilled at least one of the Bethesda's criteria. CONCLUSION: These clinicoepidemiological data provide a more accurate characterization of hereditary non-polyposis colorectal cancer and other familial colorectal cancer forms in Spain, with potential implications in preventive strategies.  相似文献   
88.
OBJECTIVES: To assess the impact of highly active antiretroviral therapy (HAART) on the blood pressure (BP) of naive patients after 1 year of treatment. METHODS: A prospective, observational study of 95 HIV-positive patients in our Unit starting HAART between January 2001 and October 2002 and maintaining the same regimen for 48 weeks of follow-up was carried out. Data on blood pressure (BP) and demographic, epidemiological, clinical, immunovirological and therapeutic characteristics related to HIV infection were collected prior to HAART and at week 48. High blood pressure (HBP) [systolic BP (SBP) > or =140 mm Hg and/or diastolic BP (DBP) > or =90 mm Hg] was defined according to international criteria. RESULTS: Of the 95 patients, 78 were men, 44% had AIDS and 68% were smokers, and their mean age was 40 years. At week 48 the prevalence of HBP was 26% and SBP, DBP and pulse pressure (PP) increased (121.8 versus 116.6 mm Hg, P=0.0001; 76.3 versus 69.7 mm Hg, P=0.004; 46.9 versus 43.8 mm Hg, P=0.001, respectively). Univariate analysis showed that HBP was associated with older age, higher body mass index (BMI), higher baseline lipids, and higher baseline BP. A linear regression model adjusting for age and sex suggested a significant impact of older age, higher baseline SBP, higher baseline hypercholesterolaemia and lower baseline CD4-cell count on SBP increase. CONCLUSIONS: Blood pressure increased after 48 weeks of HAART, leading to an important prevalence of hypertension. The increase in SBP depended on age and baseline lipid profile and immunological status. BP should be periodically measured and treated when necessary in HIV-infected patients on HAART.  相似文献   
89.
AIM:To evaluate changes in colorectal cancer(CRC) survival over the last 20 years.METHODS:We compared two groups of consecutive CRC patients that were prospectively recruited:Group Ⅰincluded 1990 patients diagnosed between 1980 and 1994.GroupⅡincluded 871 patients diagnosed in 2001.RESULTS:The average follow up time was 21 mo(1-229)for GroupⅠand 50 mo(1-73.4)for GroupⅡ.Overall median survival was significantly longer in Group Ⅱthan in GroupⅠ(73 mo vs 25 mo,P&lt;0.001)and the difference was significant for all ...  相似文献   
90.
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