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   3864篇
  免费   390篇
  国内免费   36篇
耳鼻咽喉   67篇
儿科学   248篇
妇产科学   52篇
基础医学   532篇
口腔科学   52篇
临床医学   366篇
内科学   789篇
皮肤病学   70篇
神经病学   261篇
特种医学   263篇
外科学   372篇
综合类   122篇
一般理论   7篇
预防医学   380篇
眼科学   132篇
药学   250篇
中国医学   2篇
肿瘤学   325篇
  2021年   56篇
  2020年   38篇
  2019年   41篇
  2018年   65篇
  2017年   47篇
  2016年   37篇
  2015年   73篇
  2014年   74篇
  2013年   124篇
  2012年   154篇
  2011年   165篇
  2010年   112篇
  2009年   87篇
  2008年   139篇
  2007年   173篇
  2006年   133篇
  2005年   151篇
  2004年   146篇
  2003年   126篇
  2002年   132篇
  2001年   134篇
  2000年   131篇
  1999年   119篇
  1998年   67篇
  1997年   71篇
  1996年   80篇
  1995年   64篇
  1994年   57篇
  1993年   61篇
  1992年   97篇
  1991年   109篇
  1990年   103篇
  1989年   117篇
  1988年   118篇
  1987年   96篇
  1986年   90篇
  1985年   94篇
  1984年   57篇
  1983年   48篇
  1982年   38篇
  1981年   35篇
  1980年   29篇
  1979年   42篇
  1978年   30篇
  1976年   38篇
  1975年   25篇
  1974年   28篇
  1973年   27篇
  1972年   27篇
  1971年   29篇
排序方式: 共有4290条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
Exposure of young children to group day-care settings increases the risk of illness and may result in higher use of medical care. These observations raise concerns that the use of such settings for early intervention programs for low-birth-weight infants may increase the already high burden of medical care costs incurred by these children and their families. To address the question of medical care use associated with center-based care, we examined the hospital-based and ambulatory care reported for participants of the Infant Health and Development Program. This project is a multisite randomized trial of an early intervention program for preterm low-birth-weight infants with an intervention including 2 years of center-based care. The Intervention group did not differ in hospital-based care and averaged only two more physicians' visits over the 3-year observation period than the comparison group. We conclude that early intervention programs involving high-quality group care are not accompanied by substantial increases in health care use.  相似文献   
5.
Satellite cells are the myogenic cells lying between the myofiber sarcolemma and basal lamina. The objective of this study was to determine the expression patterns of MyoD, myogenin, and Pax7 within the satellite cell population in the growing rat soleus and extensor digitorum longus (EDL) muscles. Secondly, the expression of the myogenic markers was also studied within the interstitial cell compartment and myonuclei. It was discovered that the soleus contained a higher number of Pax7, MyoD, or myogenin-positive nuclei compared with the EDL. Similarly, myogenin was expressed at a lower level in the myonuclei of the soleus compared with the EDL, and myogenin was expressed at a higher level in the interstitial compartment of the soleus compared with the EDL. When interstitial nuclei, myonuclei, and double-labeled nuclei were used in the estimate of the satellite cell population, it was discovered that approximately of 13% of the myofibers in a transverse section of the soleus muscle and 4.1% of EDL myofibers exhibit a labeled satellite cell nucleus. Overall, results from this study suggest that expression patterns of these markers vary predictably among muscles with different growth dynamics and phenotypic characteristics.  相似文献   
6.
BACKGROUND: Vitiligo is the most common pigmentary disorder with a global incidence from 0.1% to 2% in different geographical areas. Histopathology and histochemistry have shown the reduction of melanocytes in achromic patches, but microscopic changes of lesional and non-lesional skin are still not completely understood. Reflectance confocal microscopy (RCM), based on the different light reflectance index of cutaneous structures, allowed in vivo, en face microscopic evaluation of superficial skin layers with a resolution similar to skin histology. AIM: The purpose of this study was to evaluate RCM features of lesional and non-lesional skin of vitiligo patients. Moreover, re-pigmented areas were taken into consideration in order to evaluate melanocyte response to ultraviolet B (UVB) radiation. SUBJECTS AND METHODS: Sixteen patients of different phototypes affected by active non-segmental vitiligo and 10 controls were enrolled in the study. In vivo skin imaging was done using a commercially available RCM (Lucid, Vivascope 1500. Re-pigmented areas from 6 to 16 patients (after UVB narrow-band therapy) were also examined. RESULTS: Vitiligo lesions showed the disappearance of the bright rings normally seen at the dermo-epidermal junction. Moreover, non-lesional skin of vitiligo patients showed unexpected changes as the presence of half-rings or scalloped border-like features of the bright papillary rings. In re-pigmented areas after UVB narrow band therapy, the presence of activated, dendritic melanocytes was seen. CONCLUSIONS: Considering our results, and following further studies, RCM clinical applications could be used in the therapeutic monitoring and evaluation of the evolution of vitiligo.  相似文献   
7.
There is evidence from investigations of non-CNS neoplasms that secreted proteolytic enzymes may facilitate tumour invasion by partially degrading extracellular matrix (ECM). Among the enzymes which may be involved are members of the cysteine proteinase superfamily and especially cathepsin B (CB). In the present investigation we have studied CB in human gliomas in vitro , concentrating particularly on CB secretion, as extracellular enzyme is of prime importance in this context. We have found that CB is secreted by gliomas in vitro as a latent zymogen, requiring activation. This has been confirmed by gel chromatography which indicated that CB is secreted as a 42 kDa proenzyme which may be proteolytically processed to an enzymatically active 29 kDa molecule. The inactive, high molecular weight, latent CB is stable at extracellular pH in contrast to the activated low molecular weight form which rapidly loses activity at this pH. We have also measured secretion of cysteine proteinase inhibitors (CPI), as their presence would have a direct influence on the effective activity of CB, and found that all of the gliomas secreted significant amounts of a CPI as assessed by papain inhibition. Our experiments suggest that a number of factors are involved in the regulation of extracellular glioma-derived CB activity. These include: rate of secretion of pro-CB, rate of CB activation, destabilization of CB at neutral pH and the presence of cysteine proteinase inhibitors.  相似文献   
8.
9.
10.
Changes in height of choroidal melanomas after plaque therapy.   总被引:1,自引:1,他引:0       下载免费PDF全文
Serial ultrasonic measurements of 82 uveal melanomas treated with brachytherapy plaques (cobalt-60 and iodine-125) and followed up for up to 141 months revealed that no two patients had identical patterns of change. The mean absolute change in tumour height after treatment was 1.8 mm at six months, 5.6 mm at 48 months for large tumours, and 0.9 and 1.9 mm for medium sized tumours. Eighty of the 82 patients fell into one of three patterns of response: 57 patients had a decrease in height after treatment (type D), 13 patients had the same height after treatment (type S), and 10 patients had a progressive increase in height (type I). Life table comparison showed no correlation between survival and location of tumour, sex of patient, size of tumour when treated, or laterality. There was a slight correlation between age and survival. Patients older than 60 died more frequently from metastatic melanoma than those under 60 (p = 0.06). Life table analysis showed a significant correlation between tumour regression type and survival. At 48 months the best cumulative probability of survival was in patients with type D (88% alive) compared with those of type I (34% alive, p = 0.0004).  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