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   44078篇
  免费   4195篇
  国内免费   1530篇
耳鼻咽喉   99篇
儿科学   609篇
妇产科学   952篇
基础医学   6515篇
口腔科学   1317篇
临床医学   4564篇
内科学   6254篇
皮肤病学   326篇
神经病学   6282篇
特种医学   1039篇
外科学   4766篇
综合类   4350篇
现状与发展   2篇
一般理论   1篇
预防医学   3344篇
眼科学   532篇
药学   5920篇
  17篇
中国医学   1870篇
肿瘤学   1044篇
  2024年   140篇
  2023年   782篇
  2022年   1278篇
  2021年   2196篇
  2020年   2073篇
  2019年   1772篇
  2018年   1718篇
  2017年   1927篇
  2016年   2038篇
  2015年   1962篇
  2014年   2936篇
  2013年   4006篇
  2012年   2448篇
  2011年   2836篇
  2010年   2211篇
  2009年   2339篇
  2008年   2421篇
  2007年   2034篇
  2006年   1878篇
  2005年   1433篇
  2004年   1354篇
  2003年   1172篇
  2002年   908篇
  2001年   787篇
  2000年   662篇
  1999年   531篇
  1998年   505篇
  1997年   445篇
  1996年   390篇
  1995年   274篇
  1994年   257篇
  1993年   207篇
  1992年   232篇
  1991年   201篇
  1990年   197篇
  1989年   179篇
  1988年   147篇
  1987年   114篇
  1986年   117篇
  1985年   144篇
  1984年   118篇
  1983年   69篇
  1982年   76篇
  1981年   62篇
  1980年   55篇
  1979年   54篇
  1978年   40篇
  1977年   24篇
  1976年   23篇
  1973年   7篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
While factors such as gender and SES have been studied as moderators of stress for children, their perceptions of control have received little attention. In the current study, children's domain-specific perceptions of their control during marital conflict were investigated as potential moderators of the impact of family stress on children's behavior problems, and perceptions of competence. Ninety-four children aged 6-12 years and mothers from families ranging in level of parental conflict from nondiscordant to discordant to physically violent were interviewed. Multiple regression analyses revealed that higher levels of conflict control beliefs acted as compensatory moderators of stress, being associated with lower levels of problem behaviors across stress levels. However, higher conflict control beliefs acted as vulnerability moderators with regard to children's perceptions of competence.  相似文献   
112.
113.
BACKGROUND: Previous structural magnetic resonance (MR) research in patients with posttraumatic stress disorder (PTSD) has found smaller hippocampal volumes in patients compared with control subjects. These studies have mostly involved subjects who have had PTSD for a number of years, such as war veterans or adult survivors of childhood abuse. Patients with recent-onset PTSD have rarely been investigated. To our knowledge only one other study has investigated such a group. The aim of this study was to compare hippocampal volumes of patients with recent onset PTSD and nontrauma-exposed control subjects. METHODS: Fifteen patients with PTSD, recruited from an accident and emergency department, were compared with 11, non-trauma-exposed, healthy control subjects. Patients underwent a structural MR scan soon after trauma (mean time = 158 +/- 41 days). Entire brain volumes, voxel size 1 x 1 x 1 mm, were acquired for each subject. Point counting and stereology were used to measure the hippocampal and amygdala volume of each subject. RESULTS: Right-sided hippocampal volume was significantly smaller in PTSD patients than control subjects after controlling for effects of whole brain volume and age. Neither left nor total hippocampal volume were significantly smaller in the PTSD group after correction. Whole brain volume was also found to be significantly smaller in patients. There were no differences in amygdala or white matter volumes between patients and control subjects. CONCLUSIONS: This result replicates previous findings of smaller hippocampal volumes in PTSD patients, but in an underinvestigated population, suggesting that either smaller hippocampal volume is a predisposing factor in the development of PTSD or that damage occurs within months of trauma, rather than a number of years. Either of these two hypotheses have significant implications for the treatment of PTSD. For instance, if it could be shown that screening for hippocampal volume may, in some cases, predict those likely to develop clinical PTSD.  相似文献   
114.
There is compelling evidence that the etiology of Alzheimer’s disease (AD) involves characteristic amyloid-β (Aβ) deposition, oxidative stress, and anomalous metal–Aβ protein interaction. New studies have implicated redox active metals such as copper, iron, and zinc as key mediating factors in the pathophysiology of Alzheimer’s disease. There is also evidence that drugs with metal chelating properties could produce a significant reversal of amyloid-β plaque deposition in vitro and in vivo. This paper reviews current observations on the etiologic role of zinc in AD. We also discuss the interactions of zinc and copper with Aβ, a factor that purportedly facilitates disease processes. Finally, we review the protective role of zinc against Aβ cytotoxicity and hypothesize how the apparent effect of zinc on AD pathology may be paradoxical, The Zinc Paradox. Indeed, complex pathologic stressors inherent to the Alzheimer’s diseased brain dictate whether or not zinc will be neuroprotective or neurodegenerative. Further research on the zinc paradox in AD is needed in order to elucidate the exact role zinc plays in AD pathogenesis.  相似文献   
115.
A new decontaminated hassles measure for adults, the Survey of Recent Life Experiences, was developed and validated. An initial pool of 92 items was administered to 100 subjects along with the Perceived Stress Scale. Fifty-one items were selected, based on significant correlations with the latter scale. The alpha reliability of the resultant final form of the Survey of Recent Life Experiences and its correlation with perceived stress were both high. In a separate cross-replication sample of 136 adults, the alpha reliability of the Survey and its correlation against the Perceived Stress Scale remained acceptably high. Moreover, separate-sex analyses supported the reliability and validity of the Survey of Recent Life Experiences across gender. Factor analysis of the Survey yielded six interpretable factors. Intercorrelations among subscales based on these factors were generally modest, suggesting that the scale is relatively free from contamination by psychological distress.The work reported was facilitated by a grant from the Social Sciences and Humanities Research Council of Canada's Small Grant Program, administered by the Office of Research Administration, York University. The authors appreciate the cooperation of staff at the Ontario Science Centre, Toronto, and the assistance of Maria Gurevich in verifying the data.  相似文献   
116.
大气颗粒物健康效应生物学机制研究进展   总被引:11,自引:1,他引:10  
大量流行病学研究发现,大气颗粒物的污染水平与心肺系统疾病的超额发病、死亡存在密切关联,但其毒理学机制尚未阐明。本文对近年来大气颗粒物毒理学研究进行综述,包括大气颗粒物对呼吸系统、心血管系统及神经系统的毒性作用,并对氧化应激损伤、细胞钙稳态失衡及激活关键转录因子等分子毒理学机制进行了初步的阐述。  相似文献   
117.
牛磺酸对应激大鼠心肌损伤的保护机制   总被引:5,自引:2,他引:3  
何天培  顾景范 《营养学报》1997,19(2):158-162
以异丙肾上腺素诱导的大鼠应激为模型,研究牛磺酸对心肌及血清中自由基系统与游离脂肪酸含量组成的影响。与对照组比较,结果Iso组心肌中FR、LPO、CK、LDH、C16:0、C18:0、C18:1、FFA与C18:0/FFA值显著升高,SOD、C18:3、C20:4PUFA/FFA值显著降低;血清中LPO、CK、C16:0、C18:1、FFA值显著升高,C18:3、C20:4、PUFA/FFA及SOD值呈下降趋势,牛磺酸对纠正应激引起的上述变化有显著作用,结果提示牛磺酸可通过减少自由基产生,增加抗氧化酶活性来减少脂质过氧化反应,维持细胞膜完整,影响心肌中FFA含量及组成,保护心肌免受应激损伤。  相似文献   
118.
Research on irritable bowel syndrome (IBS), a functional disorder of the gastrointestinal (GI) system, has linked GI symptoms to stress. This study examined the relationship between daily stress and GI symptoms across women and within woman in IBS patients (n = 26), IBS nonpatients (IBS-NP; n = 23), and controls (n = 26), controlling for menstrual cycle phase. Women (ages 20–45) completed daily health diaries for two cycles in which they monitored daily GI symptoms and stress levels. The Life Event Survey (LES) was used as a retrospective measure of self-reported stress. The across-women analyses showed higher mean GI symptoms and stress in the IBS and IBS-NP groups relative to controls but no group differences in LES scores. The within-woman analyses found a significant and positive relationship between daily stress and daily symptoms in both the IBS-NP and the IBS groups. Controlling for menstrual cycle had no substantial impact on the results.  相似文献   
119.
The current study evaluated psychosocial variables that may contribute to the experience of headache in college adults. One hundred ninety-nine participants, 103 women and 96 men, completed head pain logs for 4 weeks after completing measures assessing psychosocial variables. Multiple regression analyses indicated that level of emotional functioning, perception of stress, and gender were predictive of future headache frequency, intensity, and duration. Family history and health habits did not predict headache activity. These findings are consistent with research investigating psychosocial variables and headache activity.  相似文献   
120.
Da-Nian Zhu, Long-Mei Xue, Peng Li. Effect of central muscarine receptor blockade. with DKJ-21 on the blood pressure and heart rote in stress-induced hypertensive rats.

The experiments were performed on Wistar or Sprague-Dawley rats of both sexes divided at random into stress and control groups. The rats in the stress groups were put into cages and subjected to electric foot-shocks and noises for 9-15 days, which caused an increase in blood pressure (BP) and heart rate (HR). In hypertensive rats DKJ-21 (4mg/lml) was injected intravenously (i.v.), and 0.5-1.0h after administration the BP and HR dropped from the high level to normotensive level. In normotensive rats, however, administration of DKJ-21 had no effect on BP or HR. In separate groups of normotensive rats, pretreatment of DKJ-21 (4 mg/l ml, i.v.) blocked the pressor and tachycardiac effect induced by microinjection of physostigmine (0.4μg/0.1 /μl/site), corticosterone (40μg/0.1μl/site) or aldosterone (40 μg/0.1 μl/site) into the rostral ventrolateral medulla (rVLM). Furthermore, DKJ-21 also attenuated the enhancement of the pressor response to stimulation of the defense area in the midbrain, which was induced by microinjection of drugs (mentioned above) into the rVLM. These results indicate that i.v. DKJ-21 can selectively block the muscarinic receptors in the rVLM in stress-induced hypertensive rats, which suggests that abnormal enhancement of cholinergic mechanism in the rVLM may be related to hypertensive effects of corticoids in this area.  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