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   327295篇
  免费   30200篇
  国内免费   22760篇
耳鼻咽喉   3023篇
儿科学   3440篇
妇产科学   4932篇
基础医学   40119篇
口腔科学   5530篇
临床医学   45746篇
内科学   50144篇
皮肤病学   3091篇
神经病学   18553篇
特种医学   12076篇
外国民族医学   213篇
外科学   33885篇
综合类   50373篇
现状与发展   78篇
一般理论   20篇
预防医学   19763篇
眼科学   9677篇
药学   33153篇
  343篇
中国医学   17866篇
肿瘤学   28230篇
  2024年   3481篇
  2023年   5151篇
  2022年   13106篇
  2021年   16459篇
  2020年   12409篇
  2019年   11003篇
  2018年   11499篇
  2017年   10035篇
  2016年   9453篇
  2015年   14400篇
  2014年   17841篇
  2013年   15390篇
  2012年   22904篇
  2011年   25837篇
  2010年   15922篇
  2009年   12278篇
  2008年   17039篇
  2007年   17049篇
  2006年   17073篇
  2005年   16794篇
  2004年   10678篇
  2003年   9777篇
  2002年   8475篇
  2001年   7482篇
  2000年   8289篇
  1999年   9021篇
  1998年   5481篇
  1997年   5501篇
  1996年   4339篇
  1995年   3929篇
  1994年   3215篇
  1993年   2098篇
  1992年   2827篇
  1991年   2417篇
  1990年   2119篇
  1989年   1862篇
  1988年   1565篇
  1987年   1357篇
  1986年   1109篇
  1985年   912篇
  1984年   527篇
  1983年   373篇
  1982年   242篇
  1981年   238篇
  1980年   190篇
  1979年   221篇
  1978年   82篇
  1977年   89篇
  1974年   102篇
  1973年   83篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Category‐based induction is an advanced cognitive function that is based on our category‐level knowledge. Previous findings have recognized the distance effect in category‐based induction: Inductive strength is affected by the hierarchical distance between the premises and conclusions. However, the neural mechanisms underlying this effect require elucidation. In the present study, we investigated the neural mechanisms of the distance effect by using EEG technology and a new experimental paradigm—category‐based induction. In this paradigm, we used three hierarchical levels of categories—the subordinate category, the basic category, the superordinate category—and an irrelevant category. We further used these categories to create four types of trial that varied in the hierarchical distance between the premise and the conclusion: the subordinate‐basic, the basic‐superordinate, the subordinate‐superordinate, and the irrelevant‐superordinate trials. In each trial, participants judged the probability that the conclusion category had the same property as the premise category. Our behavioral results revealed that people responded more slowly in the irrelevant‐superordinate trials than in the basic‐superordinate and the subordinate‐basic trials. Our ERP results showed that the irrelevant‐superordinate trials elicited smaller P300 (250–500 ms) amplitudes than did the subordinate‐basic and the basic‐superordinate trials. In addition, the subordinate‐superordinate trials elicited smaller P300 and PSW (700–998 ms) amplitudes than did the subordinate‐basic and the basic‐superordinate combinations. These findings indicate that the amplitudes of P300 and PSW may reflect the distance effect in inductive reasoning: The further the premise‐conclusion hierarchical distance, the lower the inductive strength, and thus the smaller the P300 and PSW amplitudes.  相似文献   
92.
The purpose of this study was to examine the mediating and moderating roles of resilience on the relationship between perceived stress and depression among heroin addicts. A total of 138 heroin addicts completed the measures of perceived stress, resilience, and depression. Correlation analysis indicated that perceived stress was positively associated with depression. Resilience was negatively correlated with perceived stress and depression. Mediation analysis revealed that resilience partially mediated the relationship between perceived stress and depression. However, resilience did not moderate the influence of perceived stress on depression. These findings might provide a better understanding of the mental health among heroin addicts.  相似文献   
93.
94.
95.
96.
Most high-grade serous carcinomas are thought to arise from Fallopian tube epithelium (FTE), but some likely arise outside of the tube, perhaps from ectopic tubal-type epithelium known as endosalpingiosis. Importantly, the origin of endosalpingiosis is poorly understood. The proximity of the tubal fimbriae to the ovaries has led to the proposal that disruptions in the ovarian surface that occur during ovulation may allow detached FTE to implant in the ovary and form tubal-type glands and cysts. An alternative model suggests that cells present in ectopic locations outside the Müllerian tract retain the capacity for multi-lineage differentiation and can form glands with tubal-type epithelium. We used double transgenic Ovgp1-iCreERT2;R26RLSL-eYFP mice, which express an eYFP reporter protein in OVGP1-positive tissues following transient tamoxifen (TAM) treatment, to track the fate of oviductal epithelial cells. Cohorts of adult mice were given TAM to activate eYFP expression in oviductal epithelium, and ovaries were examined at time points ranging from 2 days to 12 months post-TAM. To test whether superovulation might increase acquisition of endosalpingiosis, additional cohorts of TAM-treated mice underwent up to five cycles of superovulation and ovaries were examined at 1, 6, and 12 months post-TAM. Ovaries were sectioned in their entirety to identify endosalpingiosis. Immunohistochemical staining for PAX8, tubulin, OVGP1, and eYFP was employed to study endosalpingiosis lesions. Ovarian endosalpingiosis was identified in 14.2% of TAM-treated adult mice. The endosalpingiotic inclusion glands and cysts were lined by secretory and ciliated cells and expressed PAX8, tubulin, OVGP1, and eYFP. Neither age nor superovulation was associated with a significant increase in endosalpingiosis. Endosalpingiosis was also occasionally present in the ovaries of pre-pubertal mice. The findings imply that ovarian endosalpingiosis in the mouse does not likely arise as a consequence of detachment and implantation of tubal epithelium and other mechanisms may be relevant. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.  相似文献   
97.
Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) deficiency in primary human glioblastoma (GBM) is associated with increased invasiveness and poor prognosis with unknown mechanisms. Therefore, how loss of PTEN promotes GBM progression remains to be elucidated. Herein, we identified that ADP-ribosylation factor like-4C (ARL4C) was highly expressed in PTEN-deficient human GBM cells and tissues. Mechanistically, loss of PTEN stabilized ARL4C protein due to AKT/mTOR pathway-mediated inhibition of ARL4C ubiquitination. Functionally, ARL4C enhanced the progression of GBM cells in vitro and in vivo. Moreover, microarray profiling and GST pull-down assay identified that ARL4C accelerated tumor progression via RAC1-mediated filopodium formation. Importantly, targeting PTEN potently inhibited GBM tumor progression in vitro and in vivo, whereas overexpression of ARL4C reversed the tumor progression impaired by PTEN overexpression. Clinically, analyses with patients' specimens validated a negative correlation between PTEN and ARL4C expression. Elevated ARL4C expression but PTEN deficiency in tumor was associated with poorer disease-free survival and overall survival of GBM patients. Taken together, ARL4C is critical for PTEN-deficient GBM progression and acts as a novel prognostic biomarker and a potential therapeutic candidate. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.  相似文献   
98.
Current models describing HLA epitopes are both theoretical and empirical. Each has limitations yielding discordant results and increasingly complex modeling. The models make a priori assumptions that epitopes must be present only on the mature protein, solvent accessible, on the ‘top’ (peptide binding surface) of the molecule, restricted to the same class as the antibody, and in the same position on the target allele if reactive to more than one locus. Results obtained counter to these assumptions are routinely discounted. For the 17th International Histocompatibility and Immunogenetics Workshop, we developed a reverse engineering algorithm to define epitopes without these assumptions on a cohort of 332 primary transplant pairs. Complete NGS typing of the transcribed (including leader) genomic DNA for 11 HLA loci of donor and recipient and DSA assignment by single antigen beads was performed. Our results show that, when grouped by 16 class I and II allele specific DSA, uniform clusters and 172 specific amino acid target epitopes are recognized by recipients despite originating from disparate HLA pairs. Data also show that these targets can be in the leader, alpha 3, transmembrane and cytoplasmic domains, thus calling into question current assumptions regarding immunogenic epitopes. Comparisons of amino acid epitopes defined by the Terasaki and Duquesnoy groups (TerEp and EpRegistry) are given.  相似文献   
99.
To understand the evolution and molecular characteristics of Jiangxi H9N2 viruses, we isolated 17 viruses in 2011 and analyzed their characteristics. Phylogenetic analyses revealed that their hemagglutinin genes originate from JS/1/00-like sublineage, neuraminidase genes originate from BJ/94-like sublineage, PB1, PA, NP, and NS genes all come from SH/F/98-like sublineage, PB2 genes originate from ST/163/04-like sublineage, while M genes come from G1-like sublineage. Genotype analysis showed that our isolates were classified as genotype 57. Molecular analyses indicated that our strains contained specific sites characteristic of low-pathogenic viruses. The current study once again highlights the necessity for continued surveillance of novel H9N2 viruses.  相似文献   
100.
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