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   1067篇
  免费   73篇
耳鼻咽喉   7篇
儿科学   16篇
妇产科学   11篇
基础医学   115篇
口腔科学   8篇
临床医学   76篇
内科学   223篇
皮肤病学   30篇
神经病学   107篇
特种医学   22篇
外科学   71篇
综合类   22篇
预防医学   223篇
眼科学   5篇
药学   33篇
肿瘤学   171篇
  2023年   7篇
  2022年   21篇
  2021年   32篇
  2020年   24篇
  2019年   40篇
  2018年   41篇
  2017年   30篇
  2016年   29篇
  2015年   21篇
  2014年   24篇
  2013年   30篇
  2012年   56篇
  2011年   44篇
  2010年   13篇
  2009年   32篇
  2008年   46篇
  2007年   57篇
  2006年   60篇
  2005年   69篇
  2004年   51篇
  2003年   32篇
  2002年   37篇
  2001年   51篇
  2000年   31篇
  1999年   43篇
  1998年   14篇
  1997年   8篇
  1996年   15篇
  1995年   4篇
  1994年   9篇
  1992年   10篇
  1991年   14篇
  1990年   12篇
  1988年   8篇
  1987年   4篇
  1986年   11篇
  1985年   7篇
  1984年   8篇
  1983年   7篇
  1981年   8篇
  1980年   4篇
  1978年   5篇
  1977年   4篇
  1975年   6篇
  1974年   7篇
  1973年   11篇
  1972年   6篇
  1971年   7篇
  1970年   4篇
  1967年   4篇
排序方式: 共有1140条查询结果,搜索用时 375 毫秒
1.
2.
Brain potentials associated with the manipulation of conceptual fluency in a recognition memory paradigm were recorded. Enhanced fluency was associated with attenuation of the N400 and an increased rate of subjects' endorsing both studied and non-studied items as having been studied ("old" responses) in the recognition test. Differences were also found in latencies previously associated with post-retrieval processing, such that in the setting of enhanced fluency (1) non-studied items were associated with a positive wave from 800 to 1600 ms and (2) items endorsed as "new" were more positive than those endorsed as "old" from 1200 to 1600 ms. The effects on the N400 may be related to the impact of fluency on familiarity, whereas later processing may be involved in the attribution of fluency to prior experience.  相似文献   
3.
Objective: To investigate the frequency of neonatal and later childhood morbidity in children exposed to antiepileptic drugs in utero.

Design: Retrospective population based study.

Setting: Population of the Grampian region of Scotland.

Participants: Mothers taking antiepileptic drugs in pregnancy between 1976 and 2000 were ascertained from hospital obstetric records and 149 (58% of those eligible) took part. They had 293 children whose health and neurodevelopment were assessed.

Main outcome measures: Frequencies of neonatal withdrawal, congenital malformations, childhood onset medical problems, developmental delay, and behaviour disorders.

Results: Neonatal withdrawal was seen in 20% of those exposed to antiepileptic drugs. Congenital malformations occurred in 14% of exposed pregnancies, compared with 5% of non-exposed sibs, and developmental delay in 24% of exposed children, compared with 11% of non-exposed sibs. After excluding cases with a family history of developmental delay, 19% of exposed children and 3% of non-exposed sibs had developmental delay, 31% of exposed children had either major malformations or developmental delay, 52% of exposed children had facial dysmorphism compared with 25% of those not exposed, 31% of exposed children had childhood medical problems (13% of non-exposed sibs), and 20% had behaviour disorders (5% of non-exposed).

Conclusion: Prenatal antiepileptic drug exposure in the setting of maternal epilepsy is associated with developmental delay and later childhood morbidity in addition to congenital malformation.

  相似文献   
4.
The Museum Vrolik collection of anatomical specimens in Amsterdam, The Netherlands, comprises over 5,000 specimens of human and animal anatomy, embryology, pathology, and congenital anomalies. Recently, we rediagnosed a subset of the collection comprising dried infantile, juvenile, and adult human skulls with congenital and acquired conditions. On external examination and additional radiography, we found 58 skulls with craniosynostosis (CS) involving one or more sutures and 40 skulls with a presumed suture related condition. Most of these were part of the material collected and described by Louis Bolk (1866-1930). Analysis of his observations suggests that skull deformation because of premature suture closure depends not only on the identity of the sutures involved but also on the timing and progression of their closure and the extent of their involvement. Moreover, premature closure of the sagittal suture after 3-6 years of age appeared to be much more common than expected because it is not accompanied by skull deformation. Many of the skulls with single-suture CS were microcephalic, which may be the cause of the premature synostosis. By contrast, microcephaly may be a resulting phenomenon in multi-suture CS. We noticed that the quotient between height of the cranial vault (vertex-porion distance) and head circumference, multiplied by 100, was 26 or higher only in those CS cases with multi-suture involvement. We therefore consider this parameter, which we named "acrocephalic index", to be an indicator of multi-suture involvement in individual CS cases. In two adult skulls, the skull had a quadrangular shape, which we assumed to be correlated to the presence of an unusually interdigitated open metopic suture. We propose to name this anomaly: tetragonocephaly. Another presumed suture-related condition, bathrocephaly, was found concomitantly with basilar invagination in several cases. We hypothesize that the chronically raised intracranial pressure in these cases caused the still open lambdoidal sutures to distend and the occipital bone to protrude.  相似文献   
5.
It can be shown that the procedure for representing the effect of the vagal innervation of the heart introduced by Brown and Eccles in 1934 distorts the actual course of the inhibitory effect. A corrected procedure is proposed. It is stressed that cycle phase specificity of the stimulation can be studied only by drawing different curves representing the course of the vagal effect for different times of stimulation within the cardiac cycle.  相似文献   
6.
We have identified the mouse and rat homologs of human interleukin-22 receptor alpha 2 (IL-22R alpha 2) and compared the localization, structure, and expression of the encoding murine and human genes. The mouse IL-22R alpha 2-encoding gene is located on chromosome 10A3 between, like in human, the genes for interferon-gamma R1 and IL-20R1. It spans a region of approximately 10 kb therefore being three times shorter than the human gene. Although the overall gene structure in both species is similar, the mouse gene lacks a counterpart to the third coding exon of the human gene known to be alternatively spliced. Like in human, mouse and rat IL-22R alpha 2 exist only as soluble receptors as deduced from the lack of transmembrane and intracellular domains encoding sequences. Quantitative expression analyses showed, analogically to the human system, a limited tissue distribution of mouse IL-22R alpha 2 mRNA. Differential modulation of IL-22R alpha 2 mRNA expression was observed upon systemic inflammation in mice in spleen, thymus, and lymph node.  相似文献   
7.
Epstein–Barr virus (EBV) reactivation is a very common and potentially lethal complication of renal transplantation. However, its risk factors and effects on transplant outcome are not well known. Here, we have analysed a large, multi-centre cohort (N = 512) in which 18.4% of the patients experienced EBV reactivation during the first post-transplant year. The patients were characterized pre-transplant and two weeks post-transplant by a multi-level biomarker panel. EBV reactivation was episodic for most patients, only 12 patients showed prolonged viraemia for over four months. Pre-transplant EBV shedding and male sex were associated with significantly increased incidence of post-transplant EBV reactivation. Importantly, we also identified a significant association of post-transplant EBV with acute rejection and with decreased haemoglobin levels. No further severe complications associated with EBV, either episodic or chronic, could be detected. Our data suggest that despite relatively frequent EBV reactivation, it had no association with serious complications during the first post-transplantation year. EBV shedding prior to transplantation could be employed as biomarkers for personalized immunosuppressive therapy. In summary, our results support the employed immunosuppressive regimes as relatively safe with regard to EBV. However, long-term studies are paramount to support these conclusions.  相似文献   
8.
Assessments of 45 health technologies undertaken by Australian advisory bodies are considered in terms of the effect they have had on health care policy. The conduct and impact of the assessments was influenced by selection of topics, timing, other inputs to policy formulation and changes to policy areas and assessment agencies. Seventeen of 26 detailed assessments appear to have influenced policy, with greatest impact occurring when the technology was being introduced and there was collection of local primary data. Continued requests for the assessment reports suggests a possible longer term educational effect. All nine appraisals of proposals for nationally funded centres were influential, but the influence of guidelines for superspecialty services is less clear. Factors decreasing the influence of assessments included limitations of available policy instruments, lack of consensus between governments and professional groups and pressure of more urgent matters on the policy process.  相似文献   
9.
One hundred fifty women who had previously had at least one mammogram were sent one of three prompt letters informing them that they were due for screening. The letters were either reassuring, anxiety provoking, or the standard hospital prompt. Based on a review of the literature, we hypothesized that the reassuring letter would be most effective in motivating women to schedule and keep appointments, the anxiety-provoking letter would produce an intermediate level fo compliance, and the standard hospital letter would be least effective. Our hypothesis was partially supported. Overall, 45% of the women in the study scheduled mammogram appointments. This included 54% of those who received the reassuring letter, 42% of those who received the anxiety provoking letter, and 38% of those who received the standard letter. Although the results were in the predicted direction, the results of a chi-square test indicated that differences among groups were not statistically significant. When the dependent measure was number of appointments kept, rather than scheduled, however, significantly more women who received the reassuring letter actually kept their appointments compared with those who received the standard hospital letter. Subsequent analyses suggested that having a family history of breast cancer, receiving a reassuring letter, and being older than 50 years were important factors in scheduling appointments.  相似文献   
10.
BACKGROUND: Experimental studies in laboratory animals and humans suggest that alpha-linolenic acid (18:3n-3) may reduce the risk of arrhythmia. OBJECTIVE: The objective was to examine the association between dietary intake of alpha-linolenic acid and risk of fatal ischemic heart disease (IHD). DESIGN: This was a prospective cohort study. The intake of alpha-linolenic acid was derived from a 116-item food-frequency questionnaire completed in 1984 by 76283 women without previously diagnosed cancer or cardiovascular disease. RESULTS: During 10 y of follow-up, we documented 232 cases of fatal IHD and 597 cases of nonfatal myocardial infarction. After adjustment for age, standard coronary risk factors, and dietary intake of linoleic acid and other nutrients, a higher intake of alpha-linolenic acid was associated with a lower relative risk (RR) of fatal IHD; the RRs from the lowest to highest quintiles were 1.0, 0.99, 0.90, 0.67, and 0.55 (95% CI: 0.32, 0.94; P for trend = 0.01). For nonfatal myocardial infarction there was only a modest, nonsignificant trend toward a reduced risk when extreme quintiles were compared (RR: 0.85; 95% CI: 0.61, 1.19; P for trend = 0.50). A higher intake of oil and vinegar salad dressing, an important source of alpha-linolenic acid, was associated with reduced risk of fatal IHD when women who consumed this food > or =5-6 times/wk were compared with those who rarely consumed this food (RR: 0.46; 95% CI: 0.27, 0.76; P for trend = 0.001). CONCLUSIONS: This study supports the hypothesis that a higher intake of alpha-linolenic acid is protective against fatal IHD. Higher consumption of foods such as oil-based salad dressing that provide polyunsaturated fats, including alpha-linolenic acid, may reduce the risk of fatal IHD.  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