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   2106篇
  免费   214篇
  国内免费   66篇
耳鼻咽喉   17篇
儿科学   85篇
妇产科学   74篇
基础医学   286篇
口腔科学   101篇
临床医学   266篇
内科学   454篇
皮肤病学   29篇
神经病学   179篇
特种医学   260篇
外科学   155篇
综合类   65篇
预防医学   165篇
眼科学   20篇
药学   178篇
肿瘤学   52篇
  2021年   14篇
  2019年   26篇
  2018年   32篇
  2017年   20篇
  2016年   19篇
  2015年   27篇
  2014年   36篇
  2013年   71篇
  2012年   62篇
  2011年   62篇
  2010年   59篇
  2009年   77篇
  2008年   63篇
  2007年   108篇
  2006年   75篇
  2005年   61篇
  2004年   71篇
  2003年   56篇
  2002年   58篇
  2001年   55篇
  2000年   77篇
  1999年   64篇
  1998年   78篇
  1997年   88篇
  1996年   95篇
  1995年   82篇
  1994年   56篇
  1993年   63篇
  1992年   38篇
  1991年   49篇
  1990年   43篇
  1989年   62篇
  1988年   40篇
  1987年   64篇
  1986年   43篇
  1985年   44篇
  1984年   32篇
  1983年   37篇
  1982年   39篇
  1981年   31篇
  1980年   34篇
  1979年   12篇
  1978年   16篇
  1977年   16篇
  1976年   14篇
  1975年   11篇
  1972年   10篇
  1971年   12篇
  1969年   10篇
  1966年   11篇
排序方式: 共有2386条查询结果,搜索用时 15 毫秒
51.
The changes in concentration of plasma oestradiol, oestrone, progesterone, androstenedione, testosterone, cortisol and FSH were followed in intact female ferrets brought into oestrus by extension of the photoperiod from 8 to 16 h daily. An additional group of spayed females was similarly exposed to the extended photoperiod. There was no change in the blood oestrone, androstenedione and testosterone levels in the spayed females; the concentration of oestradiol, progesterone and FSH fell, while that of cortisol rose after 6 weeks. The intact females showed no change in plasma oestrone and cortisol concentrations, a rise in plasma oestradiol associated with the onset of oestrus, and falls in the blood levels of testosterone, androstenedione, progesterone and FSH. These results indicate that the changes in plasma gonadal steroid levels after extension of the photoperiod differ markedly from those in rodents or ruminants.  相似文献   
52.
The effect of plasma exchange with plasma protein fraction on blood viscosity was determined in seven hyperlipoproteinaemic patients with coronary or peripheral vascular disease. This resulted in decreases in whole blood viscosity of 83% and 30% respectively at the lowest and highest shear rates studied, and decreases of 21% and 59% in plasma viscosity and fibrinogen. Serum cholesterol and triglyceride were reduced by 66% and 48% respectively. Sequential studies in two patients showed that blood viscosity returned to near-basal values by the 6th day. These findings suggest that plasma exchange may result in short-term enhancement of blood flow in vessels where low shear rates predominate.  相似文献   
53.
An automated method of modelling the electrical properties of the human thorax from horizontal section data such as computerized tomographic scans has been used to develop both forward and inverse transformations between epicardial and body surface potential distributions. Eleven torso models with varying geometry and organ configurations have been studied. For the forward calculations, a standard dipole-like source is placed along the axis of the heart. Inverse calculations are performed using a measured body surface potential distribution and are based on a division of the surface of the heart into 25 source regions, producing epicardial potentials on these regions. A regularization method is used to stabilize the inverse solutions. Both forward and inverse solutions show substantial differences between models. These findings imply that matching models with patient geometry may be necessary in order to use such solutions in a clinical setting.  相似文献   
54.
Attachment organization in a combat-related PTSD sample was investigated and compared with previously published clinical and non-clinical samples. The association between insecure attachment and unresolved mourning classification (U-loss) and between U-loss and PTSD symptoms was investigated. Vietnam combat veterans diagnosed with PTSD and in treatment (N = 48) were administered the Adult Attachment Interview, the SCID-IV, and CAPS. The PTSD sample was like non-clinical samples in the incidence of secure attachment (50%), but were more commonly unresolved. Veterans with insecure attachment organizations were more likely than those with secure attachment to be classified U-loss. U-loss classification was associated with greater likelihood of comorbid anxiety disorders and PTSD avoidance/numbing symptoms. The results suggest that while insecure attachment organization is associated with unresolved mourning in response to loss, it is not differentially associated with combat-related PTSD. The relationship between U-loss and PTSD is discussed in light of current literature.  相似文献   
55.
Tuberculous mastitis is rare, especially in Western countries. We describe a case where the interferon gamma release assay blood test led to diagnosis and successful treatment of the disease.  相似文献   
56.

Background

Hormone replacement therapy may be beneficial for cardiovascular disease risk (CVR) in post-menopausal women. Soy isoflavones may act as selective estrogen receptor modulators. The aim of this study was to evaluate whether soy isoflavones had an effect on CVR markers.

Methods

The expected 10-year risk of cardiovascular disease and mortality were calculated as a secondary endpoint from a double blind randomised parallel study involving 200 women (mean age 55 years, Caucasian, Hull, UK, 2012) in the early menopause who were randomised to 15 g soy protein with 66 mg isoflavone (SPI) or 15 g soy protein alone (depleted of all isoflavones; SP) given as a snack bar between meals daily for 6 months. Age, diabetes, smoking, blood pressure and lipid profiles were used to calculate CVR using the Framingham CVR engine.

Results

SPI treatment resulted in a significant reduction in the metabolic parameters and systolic blood pressure compared to SP (p < 0.01). There were no changes in fasting lipid profile and diastolic blood pressure with either treatment. At 6 months, changes in these parameters with SPI treatment were reflected in a calculated 27% (p < 0.01) reduction in 10 year coronary heart disease risk, a 37% (p < 0.01) reduction in myocardial infarction risk, a 24% (p < 0.04) reduction in cardiovascular disease and 42% (p < 0.02) reduction in cardiovascular disease death risk.

Conclusions

Supplementation with soy protein with isoflavones for 6 months significantly improved CVR markers and calculated CVR at 6 months during early menopause compared to soy protein without isoflavones.

ISRCTN registry

ISRCTN34051237.  相似文献   
57.
Galli  SJ; Arizono  N; Murakami  T; Dvorak  AM; Fox  JG 《Blood》1987,69(6):1661-1666
The normal skin and other tissues of adult mast cell-deficient WBB6F1- W/Wv or WCB6F1-Sl/Sld mice contain less than 1.0% the number of mast cells present in the corresponding tissues of the congenic normal (+/+) mice. As a result, genetically mast cell-deficient WBB6F1-W/Wv or WCB6F1-Sl/Sld mice are widely used for studies of mast cell differentiation and function. We found that mast cells developed at sites of idiopathic chronic dermatitis in WBB6F1-W/Wv mice and that the number of mast cells present in the skin of WBB6F1-W/Wv mice was proportional to the severity of the dermatitis (in ear skin, there were 33 +/- 4 mast cells/mm2 of dermis at sites of severe dermatitis v 9 +/- 3 at sites of mild dermatitis, 0.8 +/- 0.3 in skin without dermatitis, and 100 +/- 7 in the normal skin of congenic WBB6F1-+/+ mice; in back skin, the corresponding values were 2.0 +/- 0.6, 1.1 +/- 0.9, 0.025 +/- 0.025, and 26.2 +/- 3.2). The development of mast cells was a local, not systemic, consequence of the dermatitis. Thus, WBB6F1-W/Wv mice with severe dermatitis lacked mast cells in skin not showing signs of dermatitis and also in the peritoneal cavity, stomach, cecum, and tongue. Idiopathic chronic dermatitis was not associated with the local development of mast cells in WCB6F1-Sl/Sld mice, a mutant whose mast cell deficiency is due to a mechanism distinct from that of WBB6F1-W/Wv mice. These findings may have implications for understanding the nature of the mast cell deficiency in WBB6F1-W/Wv and WCB6F1-Sl/Sld mice and for the use of these mutants to analyze mast cell differentiation and function.  相似文献   
58.

Background:

Undergraduate surgery is at an important crossroads. Many departments report significant difficulties delivering effective teaching. Our student feedback indicated a dated surgical curriculum lacking structure, quality and uniformity. We report on a new ”blended” approach employing a combination of professional DVDs, case based discussions, online material and traditional bedside teaching designed to provide structure, standardization, and equality of learning .

Methods:

Year 4 students who had undertaken the new course and year 5 students who had participated in the traditional teaching programme were compared. Students completed a 20 item questionnaire about their experiences of the surgical teaching programme.

Results:

One hundred and seventy-one year 4 (70%) and148 year 5 students (66%) responded. Domains relating to “Overall Satisfaction with the course”, “Approval of innovative teaching methods and interactivity” and “Satisfaction with the clarity of course information” showed improvements when comparing the new and old programmes. However bedside teaching was not rated as highly in the new programme (p<0.05).

Conclusion:

This blended approach has resulted in improved student understanding and engagement. The apparent compromise of bedside teaching may be a reflection of higher expectations. We believe that a similar blended approach has the potential to re-invigorate surgical teaching elsewhere.  相似文献   
59.
Previous studies have shown that spermatogenic cells are a major source of testicular RNA encoding the opioid peptide precursor proenkephalin, suggesting that proenkephalin-derived peptides may function as intratesticular paracrine factors produced by male germ cells. However, direct evidence for the production of proenkephalin by spermatogenic cells has been lacking. In this report, we have used polysome profile analysis, peptide quantitation, and immunocytochemistry to show that proenkephalin products are synthesized during spermatogenesis and are retained within spermatozoa of humans, hamsters, rats, and sheep. We further show that these peptides are stored in the sperm acrosome and are depleted from sperm following the acrosome reaction, an exocytotic event required for fertilization. Proenkephalin products thus may serve a dual function as sperm acrosomal factors released during the fertilization process as well as intratesticular regulators secreted by spermatogenic cells.  相似文献   
60.
Serum ficolin‐2 was measured in multiple (2‐27) samples from 68 paediatric sepsis patients. Fourteen individuals (21%) gave values that included a change in status from ‘normal’ to ‘insufficient’ or vice versa. Therefore, if possible, ficolin‐2 concentration should be determined in samples obtained when a disease is inactive.  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