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   499346篇
  免费   32786篇
  国内免费   1131篇
耳鼻咽喉   6440篇
儿科学   15592篇
妇产科学   14292篇
基础医学   71336篇
口腔科学   11889篇
临床医学   43651篇
内科学   99021篇
皮肤病学   9024篇
神经病学   40783篇
特种医学   18319篇
外国民族医学   56篇
外科学   78636篇
综合类   11027篇
现状与发展   3篇
一般理论   449篇
预防医学   38567篇
眼科学   11179篇
药学   34895篇
  1篇
中国医学   1136篇
肿瘤学   26967篇
  2021年   5531篇
  2020年   3403篇
  2019年   5524篇
  2018年   7453篇
  2017年   5767篇
  2016年   6355篇
  2015年   7389篇
  2014年   10459篇
  2013年   15766篇
  2012年   21739篇
  2011年   23376篇
  2010年   13940篇
  2009年   12632篇
  2008年   21896篇
  2007年   23540篇
  2006年   22895篇
  2005年   23028篇
  2004年   22141篇
  2003年   20773篇
  2002年   19922篇
  2001年   15148篇
  2000年   15070篇
  1999年   13415篇
  1998年   5772篇
  1997年   5167篇
  1996年   4787篇
  1995年   4435篇
  1994年   4058篇
  1993年   3820篇
  1992年   9492篇
  1991年   9568篇
  1990年   9291篇
  1989年   9008篇
  1988年   8300篇
  1987年   8072篇
  1986年   7696篇
  1985年   7568篇
  1984年   6204篇
  1983年   5546篇
  1982年   4228篇
  1981年   3652篇
  1980年   3526篇
  1979年   5221篇
  1978年   4156篇
  1977年   3644篇
  1976年   3313篇
  1975年   3506篇
  1974年   4006篇
  1973年   3942篇
  1972年   3540篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
Trabecular bone score (TBS) is used for fracture prediction in adults, but its utility in children is limited by absence of appropriate reference values. We aimed to develop reference ranges for TBS by age, sex, and population ancestry for youth ages 5 to 20 years. We also investigated the association between height, body mass index (BMI), and TBS, agreement between TBS and lumbar spine areal bone mineral density (aBMD) and bone mineral apparent density (BMAD) Z-scores, tracking of TBS Z-scores over time, and precision of TBS measurements. We performed secondary analysis of spine dual-energy X-ray absorptiometry (DXA) scans from the Bone Mineral Density in Childhood Study (BMDCS), a mixed longitudinal cohort of healthy children (n = 2014) evaluated at five US centers. TBS was derived using a dedicated TBS algorithm accounting for tissue thickness rather than BMI. TBS increased only during ages corresponding to pubertal development with an earlier increase in females than males. There were no differences in TBS between African Americans and non-African Americans. We provide sex-specific TBS reference ranges and LMS values for calculation of TBS Z-scores by age and means and SD for calculation of Z-scores by pubertal stage. TBS Z-scores were positively associated with height Z-scores at some ages. TBS Z-scores explained only 27% and 17% of the variance of spine aBMD and BMAD Z-scores. Tracking of TBS Z-scores over 6 years was lower (r = 0.47) than for aBMD or BMAD Z-scores (r = 0.74 to 0.79), and precision error of TBS (2.87%) was greater than for aBMD (0.85%) and BMAD (1.22%). In sum, TBS Z-scores provide information distinct from spine aBMD and BMAD Z-scores. Our robust reference ranges for TBS in a well-characterized pediatric cohort and precision error estimates provide essential tools for clinical assessment using TBS and determination of its value in predicting bone fragility in childhood and adolescence. © 2022 American Society for Bone and Mineral Research (ASBMR).  相似文献   
102.
103.
104.
105.

Purpose

The objective of the study was to define factors associated with adolescent and young adult (AYA) experiences with private time and having discussed confidentiality and the impact of these experiences on improving delivery of clinical preventive services.

Methods

In 2016, a nationally representative sample of 1,918 US AYAs (13- to 26-year-olds) was surveyed. Survey questionnaire domains were based on prior research and Fishers' information-motivation-behavior skills conceptual model. Data were weighted to represent US households with AYA and analyzed to identify factors independently associated with ever experiencing private time and discussions of confidentiality with a regular health-care provider (HCP). We examined the association of these experiences on AYA attitudes about health care.

Results

Fifty-five percent of female and 49% of male AYA reported ever having had private time with an HCP and 55% of female and 44% of male AYA had spoken to an HCP about confidentiality. Independent predictors of having experienced private time and confidentiality included older age, race, higher household income, gender of the provider, amount of years with the provider, and involvement in risk behaviors. AYA who had experienced private time and confidentiality discussions had more positive attitudes about their providers, were more willing and comfortable discussing sensitive topics, and thought that these discussions should happen at younger ages.

Conclusions

Although confidentiality and private time are important to AYA, many are not experiencing these components of care. Providing private time and discussions of confidentiality can improve the delivery of health care for young people by enhancing positive youth attitudes about preventive care.  相似文献   
106.

Objective

The teaching hospital of Nancy, France, implemented a specific multidisciplinary care pathway (French acronym AMDPL) to improve the management of patients presenting with Lyme borreliosis (LB) suspicion. We aimed to assess the first year of activity of this care pathway.

Patients and methods

We included all patients managed in the AMDPL pathway from November 1, 2016 to October 31, 2017. The first step was a dedicated Lyme disease consultation with an infectious disease specialist. Following this consultation, the LB diagnosis was either confirmed and adequate treatment was prescribed, or a differential diagnosis was established and patients received adequate management, or further investigations were required and patients were offered multidisciplinary management as part of a day hospitalization.

Results

A total of 468 patients were included. LB diagnosis was confirmed in 15% of patients (69/468), 49% of patients received a differential diagnosis, and 26% (122/468) of patients had the LB diagnosis ruled out without receiving any other diagnosis.

Conclusions

This is to our knowledge the first multidisciplinary center implemented in France for the management of patients presenting with LB suspicion related to polymorphous signs and symptoms. Several diagnoses could be confirmed or corrected, although some symptoms and complaints could not be explained. This cohort could improve our knowledge of LB and its differential diagnoses.  相似文献   
107.
Objective: To determine serotonin system abnormalities related to major depression or previous suicidal behavior.

Methods: [11C]WAY100635, [18F]altanserin and positron emission tomography were used to compare 5-HT1A and 5-HT2A binding in MDD patients divided into eight past suicide attempters (>4yrs prior to scanning) and eight lifetime non-attempters, and both groups were compared to eight healthy volunteers.

Results: The two receptor types differed in binding pattern across brain regions from each other, but there were no differences in binding between healthy volunteers and the two depressed groups or between depressed suicide attempters and non-attempters. No effects of depression severity or lifetime aggression were observed for either receptor.

Conclusion: Limitations of this study include small sample size and absence of high lethality suicide attempts in the depressed attempter group. No trait-like binding correlations with past suicide attempt or current depression were observed. Given the heterogeneity of nonfatal suicidal behavior, a larger sample study emphasizing higher lethality suicide attempts may find the serotonin biological phenotype seen in suicide decedents.  相似文献   

108.
Algorithms based on deep neural networks (DNNs) have attracted increasing attention from the scientific computing community. DNN based algorithms are easy to implement, natural for nonlinear problems, and have shown great potential to overcome the curse of dimensionality. In this work, we utilize the multi-scale DNN-based algorithm (MscaleDNN) proposed by Liu, Cai and Xu (2020) to solve multi-scale elliptic problems with possible nonlinearity, for example, the p-Laplacian problem. We improve the MscaleDNN algorithm by a smooth and localized activation function. Several numerical examples of multi-scale elliptic problems with separable or non-separable scales in low-dimensional and high-dimensional Euclidean spaces are used to demonstrate the effectiveness and accuracy of the MscaleDNN numerical scheme.  相似文献   
109.
110.
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