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   2221篇
  免费   255篇
  国内免费   1篇
耳鼻咽喉   28篇
儿科学   68篇
妇产科学   41篇
基础医学   376篇
口腔科学   108篇
临床医学   265篇
内科学   496篇
皮肤病学   46篇
神经病学   208篇
特种医学   73篇
外科学   300篇
综合类   8篇
一般理论   3篇
预防医学   182篇
眼科学   36篇
药学   143篇
中国医学   2篇
肿瘤学   94篇
  2023年   37篇
  2022年   10篇
  2021年   39篇
  2020年   45篇
  2019年   49篇
  2018年   81篇
  2017年   88篇
  2016年   87篇
  2015年   107篇
  2014年   99篇
  2013年   211篇
  2012年   150篇
  2011年   136篇
  2010年   101篇
  2009年   46篇
  2008年   82篇
  2007年   89篇
  2006年   90篇
  2005年   75篇
  2004年   104篇
  2003年   70篇
  2002年   75篇
  2001年   25篇
  1999年   14篇
  1998年   15篇
  1997年   11篇
  1996年   17篇
  1995年   21篇
  1992年   17篇
  1991年   17篇
  1989年   11篇
  1988年   12篇
  1987年   16篇
  1986年   21篇
  1985年   15篇
  1984年   22篇
  1982年   16篇
  1981年   12篇
  1980年   10篇
  1979年   14篇
  1978年   10篇
  1977年   10篇
  1976年   10篇
  1975年   9篇
  1974年   10篇
  1955年   38篇
  1954年   88篇
  1949年   20篇
  1948年   17篇
  1943年   11篇
排序方式: 共有2477条查询结果,搜索用时 390 毫秒
91.
92.
Escherichia coli is a versatile pathogen causing millions of infections in humans every year. This bacterium can form multicellular aggregates when it expresses a self-associating protein, antigen 43 (Ag43), on its surface. We have discovered that Ag43-expressing E. coli cells are efficiently taken up by human defense cells, polymorphonuclear neutrophils (PMNs), in an opsonin-independent manner. Surprisingly, the phagocytosed bacteria were not immediately killed but resided as tight aggregates within the PMNs. Our observations indicate that Ag43-mediated uptake and survival in PMNs constitute a mechanism to subvert one of the primary defense mechanisms of the human body.  相似文献   
93.
94.
The aim of this study was to determine if the bactericidal effect of microwaving gypsum casts is maintained at maximum capacity of the oven (16 casts). Batches of 8 and 16 gypsum casts made from in vivo impressions were divided in half. One half of each cast was microwaved at 900 W for 5 minutes. The remaining halves were left untreated. When assessed for bacteriological growth, the median cfu/mL of the untreated casts was between 10(5) and 10(6) [corrected] while the microwaved casts showed a cfu/mL of 0, indicating that microwaving as described will disinfect gypsum casts even at maximum capacity of the oven.  相似文献   
95.
BACKGROUND: Little information has been published regarding the difference between how patients perceive their own smiles and how dentists view them. METHODOLOGY: The authors interviewed 78 consecutively seen patients in a general dental practice in Norway about esthetic features of their faces. The patients were not actively seeking esthetic treatment. Patients rated themselves using a 100-point visual analog scale (VAS), and then two dentists (the patients' regular dentist and an independent periodontist), working with photographs of the patients, used the same VAS in rating the patients' smiles. RESULTS: The average age of the patients was 51.2 years (range, 22-84 years). There were 50 women (average age, 51.5 years; range, 22-84 years) and 28 men (average age, 52 years; range, 30-78 years). Patients' satisfaction with their own smiles reached an average of 59.1 (standard deviation [SD], 21.1; range, 5-100) on the VAS. The dentists' scores (38.6 and 40.7) were significantly lower than the patients' scores. The authors observed poor correlation between the periodontist's scores of dentogingival features and the patients' scores. Patients were most satisfied with the gingiva when smiling and least satisfied with tooth shade. Patients younger than 50 years were most satisfied with their smiles. Patients rated teeth and eyes as the most important features in an attractive face. Women gave teeth and hair significantly higher scores and head shape lower scores than did men. CONCLUSION: Patients' opinions of their own smiles were significantly higher than the two clinicians' assessments of their smiles. Dentists should be aware that patients who seek esthetic services may have different perceptions of their smiles than may patients who do not express such desires.  相似文献   
96.
The objectives of this study were to (1) determine the acute toxicity of selected shoreline washing agents (SWA) and dispersants, and (2) assess interspecies differences in sensitivity to the products. Eight shoreline washing agents (Hela saneringsvæske, Bios, Bioversal, Absorrep K212, and Corexit 9580) and chemical dispersants (Corexit 9500, Dasic NS, and Gamlen OD4000) were tested on five marine species, algae Skeletonema costatum, planktonic copepod species Acartia tonsa (temperate species), Calanus finmarchicus (boreal species) and Calanus glacialis (Arctic species), and benthic amphipod Corophium volutator. For most products, A. tonsa was the most sensitive species, whereas C. volutator was the least sensitive; however, these species were exposed through different media (water/sediment). In general, all copepod species displayed a relatively similar sensitivity to all products. However, A. tonsa was somewhat more sensitive than other copepods to most of the tested products. Thus, A. tonsa appears to be a candidate species for boreal and Arctic copepods for acute toxicity testing, and data generated on this species may be used as to provide conservative estimates. The benthic species (C. volutator) had a different sensitivity pattern relative to pelagic species, displaying higher sensitivity to solvent-based SWA than to water-based SWA. Comparing product toxicity, the dispersants were in general most toxic while the solvent-based SWA were least toxic to pelagic species.  相似文献   
97.

Background

Surgical treatment for displaced proximal humeral fractures is widely used. However, there are very few randomized controlled studies comparing surgical treatment to conservative treatment, and the evidence is debated. The aim of this study was to describe patients with displaced proximal humeral fractures in a 2-years extension of a randomized controlled trial, their functional outcome and quality of life.

Materials and methods

Patients from a single-center randomized controlled study of fifty patients aged 60 or above with displaced proximal humeral fracture (AO/OTA group B2 or C2) were randomized to surgical or conservative treatment. Surgery was performed with an angular stable implant. The main outcome was Constant score at 2-year follow-up. Secondary outcomes were an ASES self-assessment form, the 15D quality of life assessment and radiographs at 2 years.

Results

A marked improvement of shoulder function and health-related quality of life for both surgically and conservatively treated patients occurs between 6 and 12 months. Almost no change was observed between 1 and 2 year. There were no significant differences between the two treatments at 2-year follow-up.

Conclusions

In this randomized controlled trial, surgical treatment proved no better results than conservative treatment for patients with displaced proximal humeral fracture at 2-year follow-up.  相似文献   
98.
99.

Background

Early detection of autoimmune Addison's disease (AAD ) is important as delay in diagnosis may result in a life‐threatening adrenal crisis and death. The classical clinical picture of untreated AAD is well‐described, but methodical investigations are scarce.

Objective

Perform a retrospective audit of patient records with the aim of identifying biochemical markers for early diagnosis of AAD .

Material and Methods

A multicentre retrospective study including 272 patients diagnosed with AAD at hospitals in Norway and Sweden during 1978–2016. Scrutiny of medical records provided patient data and laboratory values.

Results

Low sodium occurred in 207 of 247 (84%), but only one‐third had elevated potassium. Other common nonendocrine tests were largely normal. TSH was elevated in 79 of 153 patients, and hypoglycaemia was found in 10%. Thirty‐three per cent were diagnosed subsequent to adrenal crisis, in whom electrolyte disturbances were significantly more pronounced (P < 0.001). Serum cortisol was consistently decreased (median 62 nmol L?1 [1–668]) and significantly lower in individuals with adrenal crisis (38 nmol L?1 [2–442]) than in those without (81 nmol L?1 [1–668], P < 0.001).

Conclusion

The most consistent biochemical finding of untreated AAD was low sodium independent of the degree of glucocorticoid deficiency. Half of the patients had elevated TSH levels. Only a minority presented with marked hyperkalaemia or other nonhormonal abnormalities. Thus, unexplained low sodium and/or elevated TSH should prompt consideration of an undiagnosed AAD , and on clinical suspicion bring about assay of cortisol and ACTH . Presence of 21‐hydroxylase autoantibodies confirms autoimmune aetiology. Anticipating additional abnormalities in routine blood tests may delay diagnosis.
  相似文献   
100.
For many years, the severity of valvular aortic stenosis (AS) was evaluated mainly on the basis of cardiac catheterization. In many centers, the handy peak-to-peak transvalvular pressure difference or 'peak-to-peak gradient' in relation to left ventricular function was used as a crucial feature in taking a decision regarding valve substitution. In a prospective study during the period 1994-1997, 150 consecutive patients with AS were examined systematically using cardiac catherization as well as transthoracic (TTE) and transesophageal echocardiography. The study was performed in order to compare the diagnostic accuracy and reproducibility of the three modalities with the purpose of improving our evaluation strategy. We found that the three methods were able to determine the aortic valve area with similar accuracy and reproducibility. The data thus support earlier papers and the currently recommended strategy of managing most patients on the basis of TTE since this approach is more rapid and gentle to the patients. In accordance with the past policy of our department, however, considerable weight was put on the invasive data during the study period. Thus, 12 patients with invasive peak-to-peak gradient <50 mm Hg and no severe depression of left ventricular function were not offered valve replacement, despite symptoms and significant valve area reductions. At 2.5 years of follow-up, 6 had died, 3 of severe heart failure, 2 while awaiting scheduled valve replacement, and 1 during aortocoronary bypass surgery. Another 3 patients later experienced further symptom progression and underwent successful aortic valve replacement. In the remaining 3 patients, all free from coronary stenoses and other valvular heart disease than AS, heart failure symptoms had worsened considerably during continued medical therapy. In conclusion, we do not recommend consideration of the peak-to-peak gradient in the process of deciding whether or not AS patients should receive valve replacement. A low peak-to-peak gradient does not exclude severe AS, even in the presence of preserved left ventricular function.  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