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   13795篇
  免费   1224篇
  国内免费   88篇
耳鼻咽喉   95篇
儿科学   598篇
妇产科学   346篇
基础医学   1753篇
口腔科学   405篇
临床医学   1596篇
内科学   2647篇
皮肤病学   459篇
神经病学   1069篇
特种医学   778篇
外科学   1848篇
综合类   319篇
一般理论   12篇
预防医学   1393篇
眼科学   211篇
药学   924篇
  2篇
中国医学   10篇
肿瘤学   642篇
  2021年   208篇
  2020年   117篇
  2019年   172篇
  2018年   234篇
  2017年   162篇
  2016年   176篇
  2015年   164篇
  2014年   284篇
  2013年   398篇
  2012年   562篇
  2011年   557篇
  2010年   380篇
  2009年   344篇
  2008年   542篇
  2007年   623篇
  2006年   562篇
  2005年   488篇
  2004年   476篇
  2003年   475篇
  2002年   490篇
  2001年   405篇
  2000年   473篇
  1999年   394篇
  1998年   267篇
  1997年   288篇
  1996年   230篇
  1995年   208篇
  1994年   212篇
  1993年   221篇
  1992年   310篇
  1991年   320篇
  1990年   311篇
  1989年   375篇
  1988年   282篇
  1987年   295篇
  1986年   270篇
  1985年   305篇
  1984年   189篇
  1983年   146篇
  1982年   136篇
  1981年   149篇
  1980年   117篇
  1979年   169篇
  1978年   134篇
  1977年   132篇
  1976年   116篇
  1975年   108篇
  1974年   94篇
  1973年   112篇
  1972年   98篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
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   
32.
33.
34.
Quality indicators for primary care mental health services   总被引:3,自引:2,他引:1       下载免费PDF全文
Objectives: To identify a generic set of face valid quality indicators for primary care mental health services which reflect a multi-stakeholder perspective and can be used for facilitating quality improvement.

Design: Modified two-round postal Delphi questionnaire.

Setting: Geographical spread across Great Britain.

Participants: One hundred and fifteen panellists representing 11 different stakeholder groups within primary care mental health services (clinical psychologist, health and social care commissioner, community psychiatric nurse, counsellor, general practitioner, practice nurse/district nurse/health visitor, psychiatrist, social worker, carer, patient and voluntary organisations).

Main outcome measures: Face validity (median rating of 8 or 9 on a nine point scale with agreement by all panels) for assessing quality of care.

Results: A maximum of 334 indicators were rated by panels in the second round; 26% were rated valid by all panels. These indicators were categorised into 21 aspects of care, 11 relating to general practices and 10 relating to health authorities or primary care groups/trusts. There was variation in the total number of indicators rated valid across the different panels. Overall, GPs rated the lowest number of indicators as valid (41%, n=138) and carers rated the highest number valid (91%, n=304).

Conclusions: The quality indicators represent consensus among key stakeholder groups in defining quality of care within primary care mental health services. These indicators could provide a guide for primary care organisations embarking on quality improvement initiatives in mental health care when addressing national targets and standards relating to primary care set out in the National Service Framework for Mental Health for England. Although many of the indicators relate to parochial issues in UK service delivery, the methodology used in the development of the indicators could be applied in other settings to produce locally relevant indicators.

  相似文献   
35.
FM sonography - a signal-processing technique that uses frequency and phase information as well as amplitude data - shows promise in evaluation of patients with diffuse liver disease. In a prospective blinded review of 37 patients with biopsy-proved liver disease and 42 healthy volunteers, FM sonography was clearly superior to traditional amplitude-based (AM) sonography in distinguishing healthy from diseased subjects. Statistically significant differences were seen in accuracy (FM, 98.7%; AM, 84.8%), sensitivity (FM, 97.3%; AM, 70.3%), and negative predictive value (FM, 97.7%; AM, 78.8%). Our data also suggest that current FM sonographic techniques cannot differentiate among histologic findings associated with different hepatic parenchymal abnormalities. It is unclear, therefore, whether FM imaging can reduce the numbers of patients who require biopsy for diagnosis or the frequency of biopsy procedures in patients with known disease.  相似文献   
36.
A double-blind random-ordered comparison of the effects of placebo and 5-hydroxytryptophan (200 mg, orally) in ten depressed patients with seasonal affective disorder (SAD) and ten controls disclosed slightly but significantly higher basal levels of serum prolactin and a trend toward higher basal levels of serum cortisol in the patients with SAD compared with controls. After administration of 5-HTP, the cortisol level significantly increased and the prolactin level significantly decreased in both patients and controls. No differences in the melatonin level, growth hormone level, blood pressure, or pulse rate and no side effects were noted between patients and controls in the two study conditions; the timing of basal and 5-hydroxytryptophan-stimulated hormonal secretions was similar for both groups. These results are discussed with reference to current hypotheses of the cause of SAD.  相似文献   
37.
The cigarette smoke-induced rat model of chronic bronchitis was used to study the time course of the return of cigarette smoke-induced secretory cell hyperplasia to the normal and the capacity of two non-steroidal anti-inflammatory drugs to speed this recovery. Cigarette smoke alone significantly increased (P less than 0.05) the number of secretory cells in all of the eight airway levels studied to between 52-225% above control values. After cessation of exposure, recovery was complete by 9 days in the trachea, between 10-21 days in 'proximal' intrapulmonary airways and 43-84 days in distal bronchioli. Indomethacin and flurbiprofen, given by intraperitoneal injection at 4 mg/kg body weight for 21 days of the recovery period, significantly reduced the time taken for recovery to between 4 and 9 days in intrapulmonary airways but had no effect in the trachea.  相似文献   
38.
Is EMDR an exposure therapy? A review of trauma protocols   总被引:1,自引:0,他引:1  
This article presents the well established theoretical base and clinical practice of exposure therapy for trauma. Necessary requirements for positive treatment results and contraindicated procedures are reviewed. EMDR is contrasted with these requirements and procedures. By the definitions and clinical practice of exposure therapy, the classification of EMDR poses some problems. As seen from the exposure therapy paradigm, its lack of physiological habituation and use of spontaneous association should result in negligible or negative effects rather than the well researched positive outcomes. Possible reasons for the effectiveness of EMDR are discussed, ranging from the fundamental nature of trauma reactions to the nonexposure mechanisms utilized in information processing models.  相似文献   
39.
Because chronic Mycoplasma pneumoniae respiratory infection is hypothesized to play a role in asthma, the potential of M. pneumoniae to establish chronic respiratory infection with associated pulmonary disease was investigated in a murine model. BALB/c mice were intranasally inoculated once with M. pneumoniae and examined at 109, 150, 245, 368, and 530 days postinoculation. M. pneumoniae was detected in bronchoalveolar lavage fluid by culture or PCR in 70 and 22% of mice at 109 and 530 days postinoculation, respectively. Lung histopathology was normal up to 368 days postinoculation. At 530 days, however, 78% of the mice inoculated with M. pneumoniae demonstrated abnormal histopathology characterized by peribronchial and perivascular mononuclear infiltrates. A mean histopathologic score (HPS) at 530 days of 5.1 was significantly greater (P < 0.01) than that for controls (HPS score of 0). Serum anti-M. pneumoniae immunoglobulin G was detectable in all of the mice inoculated with M. pneumoniae and was inversely correlated with HPS (r = -0.95, P = 0.01) at 530 days postinoculation. Unrestrained whole-body plethysmography measurement of enhanced pause revealed significantly elevated airway methacholine reactivity in M. pneumoniae-inoculated mice compared with that in controls at 245 days (P = 0.03) and increased airway obstruction at 530 days (P = 0.01). Murine M. pneumoniae respiratory infection can lead to chronic pulmonary disease characterized by airway hyperreactivity, airway obstruction, and histologic inflammation.  相似文献   
40.
Is the grading of breast carcinomas affected by a delay in fixation?   总被引:6,自引:0,他引:6  
Summary The effect of delay in fixation on the modified Bloom and Richardson grade of eight breast carcinomas was investigated. Topologically shuffled samples of each tumour were immersed in fixative at times of 0.5, 2, 4, 6, 18 and 24 h after surgical removal. The grade of each tumour was assessed at delays of 0.5 and 6 h. The tubule formation and nuclear pleomorphism components of the grade showed no change with a delay in fixation of 6 h. The number of mitotic figures declined by a mean of 53% over the same period and this resulted in a decrease in the histological grade of one of the tumours. The implications of these findings for the handling of breast specimens in a diagnostic histopathological laboratory are discussed.Some of these data were presented at the 162nd meeting of the Pathological Society of Great Britain and Ireland at Cambridge, 3 January 1991. Published as an abstract in J Pathol (1991) 163:154A  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