全文获取类型
收费全文 | 23261篇 |
免费 | 1611篇 |
国内免费 | 348篇 |
专业分类
耳鼻咽喉 | 73篇 |
儿科学 | 534篇 |
妇产科学 | 220篇 |
基础医学 | 3784篇 |
口腔科学 | 390篇 |
临床医学 | 2312篇 |
内科学 | 1861篇 |
皮肤病学 | 180篇 |
神经病学 | 4104篇 |
特种医学 | 290篇 |
外国民族医学 | 1篇 |
外科学 | 799篇 |
综合类 | 2473篇 |
一般理论 | 1篇 |
预防医学 | 4576篇 |
眼科学 | 61篇 |
药学 | 2611篇 |
11篇 | |
中国医学 | 341篇 |
肿瘤学 | 598篇 |
出版年
2024年 | 82篇 |
2023年 | 367篇 |
2022年 | 818篇 |
2021年 | 1113篇 |
2020年 | 881篇 |
2019年 | 689篇 |
2018年 | 653篇 |
2017年 | 750篇 |
2016年 | 809篇 |
2015年 | 758篇 |
2014年 | 1391篇 |
2013年 | 1806篇 |
2012年 | 1198篇 |
2011年 | 1353篇 |
2010年 | 962篇 |
2009年 | 992篇 |
2008年 | 1047篇 |
2007年 | 1016篇 |
2006年 | 913篇 |
2005年 | 735篇 |
2004年 | 605篇 |
2003年 | 577篇 |
2002年 | 505篇 |
2001年 | 399篇 |
2000年 | 314篇 |
1999年 | 282篇 |
1998年 | 230篇 |
1997年 | 230篇 |
1996年 | 191篇 |
1995年 | 188篇 |
1994年 | 162篇 |
1993年 | 132篇 |
1992年 | 145篇 |
1991年 | 136篇 |
1990年 | 118篇 |
1989年 | 122篇 |
1988年 | 125篇 |
1987年 | 102篇 |
1986年 | 152篇 |
1985年 | 251篇 |
1984年 | 245篇 |
1983年 | 177篇 |
1982年 | 216篇 |
1981年 | 201篇 |
1980年 | 199篇 |
1979年 | 182篇 |
1978年 | 129篇 |
1977年 | 141篇 |
1976年 | 132篇 |
1975年 | 92篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
乳腺癌新辅助化疗后动态增强MRI表现与病理反应性相关性研究 总被引:3,自引:0,他引:3
目的探讨乳腺癌新辅助化疗后动态增强MRI(DCE—MRI)表现的形态学和时间信号强度曲线(TIC)类型与病理学反应性的关系。方法45例乳腺癌患者经新辅助化疗结束后行乳腺DCE—MR检查及手术治疗。应用AW4.2图像工作站观察残余肿瘤强化的形态和TIC类型(共3型)。由病理科医师对乳腺癌化疗后手术标本的病理反应性进行评估,分为1~5级,5级为病理完全缓解,4级和5级为组织学显著反应。分析病理反应性级别与DCE—MRI残余强化的TIC类型、形态的关系,统计方法采用精确概率法。结果45例中病理反应性5级7例,4级16例,3级16例,1和2级共6例。20例I型曲线中组织学显著反应者占70.0%(14/20),而6例Ⅲ型曲线均为组织学反应不显著者。TIC类型在不同的病理反应级别分布差异有统计学意义(P=0.001)。组织学显著反应且有残余强化者共18例,其中非肿块性强化11例。残余强化的肿块(非肿块)形态表现在不同病理反应性分级中分布差异有统计学意义(P=0.012)。结论乳腺癌新辅助化疗后DCE—MRI的形态及血液动力学表现特点与化疗后病理反应性相关。非肿块性强化和I型TIC与组织学显著反应有关。 相似文献
42.
A neurotrophic model for stress-related mood disorders. 总被引:31,自引:0,他引:31
There is a growing body of evidence demonstrating that stress decreases the expression of brain-derived neurotrophic factor (BDNF) in limbic structures that control mood and that antidepressant treatment reverses or blocks the effects of stress. Decreased levels of BDNF, as well as other neurotrophic factors, could contribute to the atrophy of certain limbic structures, including the hippocampus and prefrontal cortex that has been observed in depressed subjects. Conversely, the neurotrophic actions of antidepressants could reverse neuronal atrophy and cell loss and thereby contribute to the therapeutic actions of these treatments. This review provides a critical examination of the neurotrophic hypothesis of depression that has evolved from this work, including analysis of preclinical cellular (adult neurogenesis) and behavioral models of depression and antidepressant actions, as well as clinical neuroimaging and postmortem studies. Although there are some limitations, the results of these studies are consistent with the hypothesis that decreased expression of BDNF and possibly other growth factors contributes to depression and that upregulation of BDNF plays a role in the actions of antidepressant treatment. 相似文献
43.
目的:探讨宫颈癌的临床、病理特点、诊治方法及预后因素。方法:收集1996年1月至2001年1月226例宫颈癌患者进行回顾性分析。结果:平均患病年龄为48.18岁。130例患者为阴道流血,70例为阴道流液,25例下腹疼痛,l例精神减退、贫血、浮肿。病理分期:Ⅰ期病例数为169例(75%);Ⅱ期病例数为3l例(13.72%);Ⅲ期病例数为23例(10.18%);Ⅳ期病例数为3例(1.1%)。比较2l例宫颈鳞癌与宫颈腺癌的转移,显示后者的腹主动脉旁淋巴结转移、肾上腺转移、子宫转移、胸水形成明显高于前者。结论:重视宫颈癌发病相关因素及临床症状,争取早期诊断,严格手术病理分期,选择适当治疗方案。 相似文献
44.
Background While parenting behaviours have direct effects on children’s behavioural outcomes, other, more distal factors also may be shaping the way a mother handles parenting responsibilities. Dispositional factors are likely to be a major influence in determining how one parents. Although researchers have studied the relationships among maternal dispositional factors, parenting, and child behaviours, few studies have examined these relationships when the child is at developmental risk. Children with developmental delays evidence elevated clinical level behaviour problems, so this group is of primary interest in the search for precursors to psychopathology. The present study examined how the maternal dispositional trait of self‐mastery, as well as supportive and non‐supportive parenting, relate to behaviour problems in young children with and without developmental delay. Method Participants were 225 families, drawn from Central Pennsylvania and Southern California. The children, all aged 4 years, were classified as delayed (n = 97) or non‐delayed (n = 128). The Self‐Mastery Scale measured perceived level of control over life events. The Coping with Children’s Negative Emotions Scale measured different ways parents perceive themselves as reacting to their children’s distress and negative affect. The Child Behavior Checklist assessed children’s behaviour problems. Results Delayed condition mothers reported significantly more child behaviour problems than non‐delayed condition mothers; the two conditions did not differ in self‐mastery, supportive parenting, or non‐supportive parenting. Self‐mastery, non‐ supportive parenting reactions, and child behaviour problems all related significantly to one another. For the sample as a whole and within the delayed condition, the association between self‐mastery and child behaviour problems was partially mediated by non‐supportive parenting reactions, although self‐mastery was still significantly associated with problem behaviour. In the non‐delayed condition, although significant relationships also were found among the variables of interest, non‐supportive parenting did not have a significant main or mediation effect. Delay status moderated the relationship between negative parenting reactions and child behaviour problems, assessed by the Child Behavior Checklist Total and Internalizing scores. When mothers displayed low levels of non‐supportive reactions, children in the delayed and non‐delayed groups had similar levels of total problem behaviour. However, when mothers were medium or high in non‐supportive reactions, children in the delayed group had much higher levels of problem behaviours than those in the non‐delayed group. Conclusions The present study extended research on parental dispositional factors and parenting by measuring self‐mastery as a global personality trait rather than measuring self‐efficacy related specifically to childrearing. Moreover, relationships were examined for both developmentally delayed and non‐delayed samples, allowing for a clearer understanding of the influences on problem behaviours in children with developmental delays. The findings support the view that parenting behaviours have a greater impact on children at developmental risk. 相似文献
45.
The behavioral genetics of colony defense in honeybees: Genetic variability for guarding behavior 总被引:3,自引:1,他引:2
Guard honeybees stand at the entrance of colonies and facilitate the exclusion of nonnestmates from the colony. In this study, we examined the hypothesis that genetic variability among individuals in colonies might explain variability in guarding activity. To do this, we cross-fostered honey bees between colonies with high-defensive responses and colonies with low-defensive responses in alarm pheromone tests. Individuals from high-defensive colonies were more likely to guard in their own colonies (controls) than cross-fostered bees from low-defensive colonies. Cross-fostered high-defensive bees also were more likely to guard in low-defense colonies. These results support the hypothesis that interindividual differences in guarding behavior are at least partially under genetic control. A positive correlation between number of guards and response to alarm pheromone demonstrates a link between behaviorally separated components of the overall defensive response.This work was supported by NSF Grant BNS 8605604. 相似文献
46.
Bruce Becker MD Robert Woolard MD Ted D. Nirenberg PhD P. Allison Minugh PhD Richard Longabaugh EdD Patrick R. Clifford PhD 《Academic emergency medicine》1995,2(9):784-790
Objectives: To determine the incidence of alcohol use in subcritically injured patients presenting to the ED, by using a saliva alcohol test (SAT) at ED triage during the ED initial assessment; to compare the incidence of alcohol use revealed by the SAT with documentation of alcohol use by ED nurses and emergency physicians (EPs) blinded to the SAT results; and to describe the demographics of the SAT-positive, subcritically injured population.
Methods: A blinded, prospective, observational evaluation of ED patients presenting with subcritical injuries was performed. The patients were tested for alcohol use with an SAT, and a subsequent record review was conducted for extraction of demographic data and evidence of documentation of alcohol use by ED nurses and EPs blinded to the SAT results.
Results: During the study. 791 subcritically injured patients had SATs performed. Twenty-one percent of these patients were found to be alcohol-positive by SAT. Either the ED nurse or the EP documented a clinical impression of alcohol use for 52% of the SAT-positive patients. There were higher SAT-positive rates among men (24%), victims of assault (47%), and patients arriving at night (41%).
Conclusions: While the SAT identified 21% of the subcritically injured patient population as alcohol-positive, ED nurse and EP documentation did not identify half of these alcohol-positive patients. Many of these patients may be at risk for additional injuries related to their drinking behavior. 相似文献
Methods: A blinded, prospective, observational evaluation of ED patients presenting with subcritical injuries was performed. The patients were tested for alcohol use with an SAT, and a subsequent record review was conducted for extraction of demographic data and evidence of documentation of alcohol use by ED nurses and EPs blinded to the SAT results.
Results: During the study. 791 subcritically injured patients had SATs performed. Twenty-one percent of these patients were found to be alcohol-positive by SAT. Either the ED nurse or the EP documented a clinical impression of alcohol use for 52% of the SAT-positive patients. There were higher SAT-positive rates among men (24%), victims of assault (47%), and patients arriving at night (41%).
Conclusions: While the SAT identified 21% of the subcritically injured patient population as alcohol-positive, ED nurse and EP documentation did not identify half of these alcohol-positive patients. Many of these patients may be at risk for additional injuries related to their drinking behavior. 相似文献
47.
This study investigated a discrete-trial, titration duration discrimination procedure in behavioral pharmacology. Pentobarbital and d-amphetamine, measured with this procedure, selectively affected discrimination more than response tendencies. Pentobarbital also tended to affect selectively discrimination of longer durations, whereas d-amphetamine did not. Further experiments showed that (1) other algorithms for modulating stimulus duration are useful in behavioral pharmacology and toxicology, (2) threshold estimates are similar with the method of constant stimuli and the method of titration, and (3) this titration procedure permits the separate examination of drug effects upon discrimination and upon response tendencies; the fixed-interval procedure does not. Baseline variability was an important correlate of drug effects in that the endpoints with more variable baselines were also more sensitive to drugs. 相似文献
48.
A. L. Dinzburg A. M. Chirkov S. K. Chirkova I. S. Voit 《Bulletin of experimental biology and medicine》1992,114(5):1579-1581
Research Institute of Experimental Pathology and Therapy, Sukhumi. (Presented by Academician of the Russian Academy of Medical Sciences B. A. Lapin.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 114, No. 11, pp. 457–459, November, 1992. 相似文献
49.
The moderator effect of gender on (i) the relation between adolescents' sexual experience on the one hand; and (ii) their orientations towards the type of relational and emotional commitment that they expect to be present before engaging in a sexual relationship, and (iii) having a steady partner on the other was examined. We hypothesized that the relations between these facets would be stronger for women. We utilized a random sample of 253 British adolescents interviewed twice with a 1-year interval LISREL multigroup analysis with mean structures was used to test the hypotheses, thus offering the opportunity of detecting moderator as well as main effects of gender. Differential effects of emotional and relational commitment and having a steady partner relationship on sexual experience supported the hypotheses. 相似文献
50.
用动物肠道溶瘤病毒(Ecco-18)实验治疗荷瘤小鼠(P_(615))时,对其非瘤器官进行了光镜和电镜观察。结果发现,荷瘤小鼠各脏器均未查到病毒颗粒或病毒性物质。各脏器的超微结构与对照组相比未见病理改变。 相似文献