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   209924篇
  免费   15585篇
  国内免费   745篇
耳鼻咽喉   2277篇
儿科学   5483篇
妇产科学   4308篇
基础医学   27111篇
口腔科学   4512篇
临床医学   19988篇
内科学   44810篇
皮肤病学   2755篇
神经病学   20319篇
特种医学   6949篇
外国民族医学   13篇
外科学   32943篇
综合类   3412篇
现状与发展   2篇
一般理论   291篇
预防医学   19048篇
眼科学   4367篇
药学   14477篇
  1篇
中国医学   375篇
肿瘤学   12813篇
  2023年   758篇
  2022年   1202篇
  2021年   3447篇
  2020年   2112篇
  2019年   3396篇
  2018年   3978篇
  2017年   3220篇
  2016年   3418篇
  2015年   4072篇
  2014年   6105篇
  2013年   8841篇
  2012年   13146篇
  2011年   14344篇
  2010年   8108篇
  2009年   7320篇
  2008年   13614篇
  2007年   14445篇
  2006年   13940篇
  2005年   14409篇
  2004年   13823篇
  2003年   12908篇
  2002年   12441篇
  2001年   1885篇
  2000年   1468篇
  1999年   2047篇
  1998年   2829篇
  1997年   2440篇
  1996年   2207篇
  1995年   1955篇
  1994年   1757篇
  1993年   1658篇
  1992年   1213篇
  1991年   1150篇
  1990年   1055篇
  1989年   956篇
  1988年   1014篇
  1987年   1021篇
  1986年   998篇
  1985年   1081篇
  1984年   1481篇
  1983年   1461篇
  1982年   1814篇
  1981年   1640篇
  1980年   1557篇
  1979年   813篇
  1978年   958篇
  1977年   932篇
  1976年   831篇
  1975年   682篇
  1974年   666篇
排序方式: 共有10000条查询结果,搜索用时 265 毫秒
51.
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   

52.
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   
53.
54.
55.
56.
57.
58.
2‐deoxy D‐glucose (2DG) was tested for efficacy in treating alopecia areata using the C3H/HeJ skin graft model. 2DG has proven to be efficacious in treatment of various mouse models of autoimmunity with minimal serious side effects noted. This agent has been shown to normalize abnormally activated T‐cell populations while also preventing cell surface expression of NKG2D; key factors defining alopecia areata disease progression. Daily oral ingestion of 2DG via drinking water to mice with patchy or diffuse alopecia areata for 16 weeks failed to prevent expansion of alopecia or cause regrowth of hair in treated mice. Histologically, there were no differences between treated and control groups. These results indicate that, while 2DG is effective for some autoimmune diseases, it was not efficacious for the cell‐mediated autoimmune mouse disease, alopecia areata.  相似文献   
59.

Background

Most elderly trauma patients suffer blunt head injury and many utilize antithrombotic (AT) medications. The utility of delayed CT-head (D-CTH) in neurologically intact elderly patients using AT who have an intracranial hemorrhage (ICH) on presentation is unknown. We hypothesized that D-CTH would not alter clinical management and aimed to evaluate the role of D-CTH in this population.

Methods

A retrospective cohort study was performed. Patients ≥65 years sustaining blunt head injuries from January 2010 to July 2017 were identified using our level 1 trauma center database. AT-patients presenting with ICH who underwent D-CTH were included. Patients with worsened ICH were compared to those with stable to improved ICH on D-CTH. AT-patients were compared to a cohort of non-AT patients. Fisher’s Exact and Mann-Whitney U tests were utilized and a power analysis conducted.

Results

137?A?T and 34 non-AT patients were identified. There was no difference in hemorrhage progression or appearance of new ICH. No patient had a change in management from D-CTH in either cohort. AT-patients were slightly older (p?<?0.001), but cohorts were otherwise similar.50 AT-patients with worsened ICH were compared to 87 with stable ICH. There was no difference in cohort demographics. Hemorrhage progression did not vary with type of AT used but did increase if multiple types of synchronous ICH were present (p?<?0.001).

Conclusions

Our data supports abstaining from routine D-CTH of elderly ICH patients with an intact neurologic examination who are utilizing aspirin, clopidogrel or warfarin. Conclusions cannot be drawn regarding new oral anticoagulants (NOACs) given low enrollment. Further multicenter study is required to provide adequate power and detect small levels of management change.  相似文献   
60.
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