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   717篇
  免费   43篇
  国内免费   21篇
耳鼻咽喉   3篇
儿科学   39篇
妇产科学   1篇
基础医学   108篇
口腔科学   19篇
临床医学   81篇
内科学   124篇
皮肤病学   20篇
神经病学   42篇
特种医学   122篇
外科学   55篇
综合类   12篇
预防医学   63篇
眼科学   1篇
药学   37篇
肿瘤学   54篇
  2022年   4篇
  2021年   16篇
  2020年   6篇
  2019年   5篇
  2018年   14篇
  2017年   11篇
  2016年   13篇
  2015年   16篇
  2014年   19篇
  2013年   35篇
  2012年   20篇
  2011年   27篇
  2010年   35篇
  2009年   40篇
  2008年   20篇
  2007年   37篇
  2006年   27篇
  2005年   20篇
  2004年   19篇
  2003年   5篇
  2002年   9篇
  2001年   12篇
  2000年   6篇
  1999年   8篇
  1998年   35篇
  1997年   38篇
  1996年   32篇
  1995年   31篇
  1994年   11篇
  1993年   20篇
  1992年   4篇
  1991年   10篇
  1990年   11篇
  1989年   13篇
  1988年   19篇
  1987年   15篇
  1986年   12篇
  1985年   14篇
  1984年   7篇
  1983年   7篇
  1982年   18篇
  1981年   7篇
  1980年   9篇
  1978年   7篇
  1977年   7篇
  1976年   7篇
  1975年   5篇
  1974年   3篇
  1973年   3篇
  1970年   3篇
排序方式: 共有781条查询结果,搜索用时 15 毫秒
31.
Background: Ventilator frequency is one of the determinants of tidal volume delivery during high‐frequency ventilation. Clinicians increasingly use data on ventilator displays to inform their decisions. Aim: To measure the frequencies delivered by the Dräger Babylog 8000plus ventilator when used in high‐frequency mode. Methods: Ventilator waveforms using a test lung were recorded at the full range of settings 5–20 Hz using Spectra software at 1000 Hz. The changes in frequency produced by a 1‐ Hz change in set frequency were calculated. Actual and displayed frequencies were compared. Results: For settings up to 12 Hz, median (range) difference between set and delivered frequencies was 0 (?0.4 to +0.1) Hz. Above 12 Hz, delivered frequency varied by ?0.3 (?1.9 to +0.3) Hz. For 1‐ Hz changes in frequency settings, in the range 5–12 Hz, 1‐ Hz changes produced a change in delivered frequency of 1.0 (0.6–1.4) Hz. Above 12 Hz, the corresponding changes were 0.7 (0–2.9) Hz. The ventilator displays the set frequency during operation rather than the delivered frequency. Conclusion: At 12 Hz and below, the differences between set and delivered frequencies were relatively small compared with those at 13 Hz and higher. Above 13 Hz, the difference between set and delivered frequencies was up to 2.9 Hz. Some frequency setting changes did not result in a change in delivered frequency.  相似文献   
32.
In this study, Tithonia diversifolia Helms. (A Gray), Aloe secundiflora (Miller) and Azadirachta indica (A. Juss) plant extracts were used to make herbal soaps while Thevetia peruviana (Schum) seed oil was used to make a herbal lotion for skincare. The soaps were tested for the growth inhibition of Escherichia coli, and Candida albicans. The lotion was evaluated against Staphylococcus aureus and E.coli. Although Tithonia diversifolia soap exhibited the highest inhibitory effect on the test bacterial strains, it had the least inhibition against C. albicans. Results from this study indicated that the ‘Tithonia diversifolia’ soap would have superior skin protection against the tested bacteria but would offer the least skin protection against C. albicans. The herbal lotion inhibited S. aureus and E. coli in a concentration dependent manner, however, the inhibitory effect was more pronounced on S. aureus.  相似文献   
33.
Membranous nephropathy (MN), the leading cause of nephrotic syndrome in adults, is characterized by the deposition of subepithelial immune deposits that consist mainly of immunoglobulin (Ig)G and complement. Most of the cases are primary or idiopathic (iMN), while only approximately 25% of the cases are secondary to some known disease such as systemic lupus erythematosus, hepatitis B, drugs and malignancies. Most of our knowledge on the pathogenesis of iMN has relied upon old experimental models (i.e. Heymann nephritis) that have shown that immune deposits are formed in situ by the reaction of autoantibodies against the respective podocyte antigen. Recent findings indicate that podocyte proteins also act as an autoantigen in human iMN. The M‐type phospholipase A2 receptor (PLA2R) has been identified as the main target antigen, as it can be found in approximately 70% of iMN patients but only rarely in other glomerulonephritides. Podocytes damage in the experimental model of Heymann nephritis is complement‐mediated. In humans, the presence of complement within the subepithelial deposits is well established, but IgG4, which does not activate complement by classical or alternative pathways, represents the predominant subclass of IgG anti‐PLA2R. Some evidence suggests that IgG4 anti‐PLA2R autoantibodies can bind mannan‐binding lectin (MBL) and activate the lectin complement pathway. A genetic background for iMN has been demonstrated by genome‐wide association studies that have shown highly significant associations of the PLA2R1 and the human leucocyte antigen (HLA)‐DQA1 loci with iMN. In addition to their diagnostic value, anti‐PLA2R antibodies may be useful to monitor disease activity and predict response to treatment.  相似文献   
34.

Objective

To examine situations where shared decision making (SDM) in practice does not achieve the goal of a patient-centered decision.

Methods

We explore circumstances in which elements necessary to realize SDM – patient readiness to participate and understanding of the decision – are not present. We consider the influence of contextual factors on decision making.

Results

Patients’ preference and readiness for participation in SDM are influenced by multiple interacting factors including the patient’s comprehension of the decision, their emotional state, the strength of their relationship with the clinician, and the nature of the decision. Uncertainty often inherent in information can lead to misconceptions and ill-formed opinions that impair patients’ understanding. In combination with cognitive biases, these factors may result in decisions that are incongruent with patients’ preferences. The impact of suboptimal understanding on decision making may be augmented by the context.

Conclusions

There are circumstances in which basic elements required for SDM are not present and therefore the clinician may not achieve the goal of a patient-centered decision.

Practice Implications

A flexible and tailored approach that draws on the full continuum of decision making models and communication strategies is required to achieve the goal of a patient-centered decision.  相似文献   
35.

Background

Primary care is increasingly interested in the identification of frailty, as it selects the target population for integrated care. However, instruments for the identification of frailty specifically validated for use in primary care are scarce. This study developed the Easycare Two-step Older persons Screening (Easycare-TOS), which provides a valid, efficient, and pragmatic screening procedure to identify frail older people.

Aim

This paper aims to describe the development of the Easycare-TOS and the data from the pilot studies.

Design and setting

Observational pilot study in seven academic GP practices in and around Nijmegen, The Netherlands.

Method

The Easycare-TOS was developed in a cyclic process with the input of stakeholders. In every cycle, the requirements were first defined, then translated into a prototype that was tested in a pilot study. The Easycare-TOS makes optimal use of prior knowledge of the GP, and the professionals’ appraisal is decisive in the frailty decision, instead of a cut-off score. Further, it considers aspects of frailty, as well as aspects of the care context of the patient.

Results

The pilot data have shown that after step 1, two-thirds of the patients do not need further assessment, because they are judged as not frail, based on prior knowledge of the GP. The overall prevalence of frailty in this pilot study is 24%. Most professionals who participated in the pilot studies considered the time investment acceptable and the method to be of added value.

Conclusion

The Easycare-TOS instrument meets the predefined efficiency, flexibility, and acceptability requirements for use as an identification instrument for frailty in primary care.  相似文献   
36.
Our goals were to determine the prognostic value of a yolk sac or fetal heart motion seen during an early accurately dated transvaginal ultrasound (TVU). We reviewed 225 consecutive pregnancies for fetal heart motion data. Furthermore, 63 pregnancies following in-vitro fertilization were reviewed for yolk sac information. The TVU was performed between 5 and 6 weeks following presumed conception (heart motion data) and between 22 and 32 days following in-vitro fertilization (yolk sac data). Pregnancies were followed until an ongoing pregnancy or spontaneous abortion was documented. The presence of a yolk sac between 22 and 32 days from fertilization was associated with the development of fetal heart motion in 94% of cases. The absence of the yolk sac by 32 days after fertilization was always associated with a poor outcome. In women < 36 years of age, the presence of fetal heart motion was associated with a spontaneous abortion in only 4.5% of the cases. However, the incidence of spontaneous abortion following fetal heart motion increased to 10% in women 36-39 years and 29% in women > or = 40 years of age. The presence of heart motion should not be considered a reassuring sign in the older woman. These data have implications regarding early embryology and the counselling of infertility patients.   相似文献   
37.
Over a 26 month period 17% of couples having treatment in our clinical programmes selected a commercially available protein (normal serum albumin, NSA) prepared from pooled human sera instead of using their own serum as a supplement for their embryo culture media. In a retrospective analysis of >2000 gonadotrophin-stimulated cycles and 1000 cycles where frozen/thawed embryos were transferred, fertilization, embryo quality and pregnancy rates following in-vitro fertilization (IVF), gamete intra-Fallopian transfer (GIFT) or intracytoplasmic sperm injection (ICSI) were unaffected by the type of protein used to supplement the culture medium. When embryos were thawed in medium containing NSA, both pregnancy (PR) and implantation rates (IR) were significantly lower (P <0.05) than if the medium was supplemented with serum (PR 8.3% and 17.5%; IR 4.6% and 10.5%). Inclusion of NSA before freezing reduced the IR of thawed embryos. To further test this observation all cycles where embryos were cultured and frozen in medium containing NSA (173 cycles) were matched to cycles where serum was used and the outcome was compared. At the end of 1995 just over half of the embryos in both groups had been thawed. No statistical difference was noted in the pregnancy rates (NSA, 5.6% versus serum, 11.3%) but the IR per embryo was significantly lower when embryos were cultured and frozen in medium supplemented with NSA (2.2%) than when serum was used as the supplement (6.6%).   相似文献   
38.
39.
Inflamed fibronectin: an altered fibronectin enhances neutrophil adhesion   总被引:4,自引:0,他引:4  
Vercellotti  GM; McCarthy  J; Furcht  LT; Jacob  HS; Moldow  CF 《Blood》1983,62(5):1063-1069
Recent investigations have emphasized the role of activated granulocytes in mediating vascular endothelial injury in the pathogenesis of shock lung. In vitro studies have indicated that tight adherence of the neutrophil to the endothelium is crucial for the development of cellular injury. Fibronectin is critical to cell-to- substratum and cell-to-cell interactions. Since fibronectin resides in plasma, on endothelial cell surfaces and is secreted into cell matrices, the adhesive properties of fibronectin must be modulated, lest universal cell agglomeration occur, yet be enhanced when cell attachment is appropriate. In these studies, treatment of fibronectin- coated surfaces with neutrophil release products increased the adhesion of activated neutrophils. Similarly, endothelial cells treated with neutrophil release products become a more adherent substrate for neutrophils. This enhanced adherence generated by treatment of fibronectin with neutrophil supernatants is inhibitable by heat and the lysosomal proteinase inhibitor, pepstatin-A. Neutrophil release products cause proteolytic fragmentation of fibronectin and enhanced fibronectin immunofluorescence on endothelial cells. In addition, neutrophils are more injurious to endothelial cells that have been pretreated with neutrophil release products. Neutrophils may enhance their own adherence to endothelial cells by altering fibronectin, and this altered, or "inflamed," fibronectin may serve as an amplifier of inflammation.  相似文献   
40.

Background  

Recent evidence, both animal and human, suggests that modifiable factors during fetal and infant development predispose for cardiovascular disease in adult life and that they may become possible future targets for prevention. One of these factors is maternal psychosocial stress, but so far, few prospective studies have been able to investigate the longer-term effects of stress in detail, i.e. effects in childhood. Therefore, our general aim is to study whether prenatal maternal psychosocial stress is associated with an adverse cardio-metabolic risk profile in the child at age five.  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