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   1382篇
  免费   89篇
  国内免费   3篇
耳鼻咽喉   5篇
儿科学   38篇
妇产科学   28篇
基础医学   270篇
口腔科学   12篇
临床医学   104篇
内科学   311篇
皮肤病学   21篇
神经病学   92篇
特种医学   45篇
外科学   165篇
综合类   5篇
一般理论   2篇
预防医学   95篇
眼科学   11篇
药学   98篇
中国医学   3篇
肿瘤学   169篇
  2023年   9篇
  2022年   12篇
  2021年   24篇
  2020年   19篇
  2019年   26篇
  2018年   48篇
  2017年   34篇
  2016年   39篇
  2015年   43篇
  2014年   61篇
  2013年   63篇
  2012年   115篇
  2011年   99篇
  2010年   55篇
  2009年   68篇
  2008年   75篇
  2007年   81篇
  2006年   60篇
  2005年   64篇
  2004年   55篇
  2003年   51篇
  2002年   42篇
  2001年   29篇
  2000年   45篇
  1999年   33篇
  1998年   15篇
  1997年   11篇
  1996年   5篇
  1995年   4篇
  1994年   13篇
  1993年   6篇
  1992年   13篇
  1991年   14篇
  1990年   14篇
  1989年   15篇
  1988年   9篇
  1987年   6篇
  1986年   7篇
  1985年   9篇
  1984年   9篇
  1983年   10篇
  1982年   6篇
  1981年   5篇
  1979年   5篇
  1976年   4篇
  1975年   5篇
  1971年   3篇
  1967年   5篇
  1966年   3篇
  1960年   3篇
排序方式: 共有1474条查询结果,搜索用时 15 毫秒
1.
Melatonin, the main hormone produced by the pineal gland, is secreted in a circadian manner (24‐hr period), and its oscillation influences several circadian biological rhythms, such as the regulation of clock genes expression (chronobiotic effect) and the modulation of several endocrine functions in peripheral tissues. Assuming that the circadian synchronization of clock genes can play a role in the regulation of energy metabolism and it is influenced by melatonin, our study was designed to assess possible alterations as a consequence of melatonin absence on the circadian expression of clock genes in the epididymal adipose tissue of male Wistar rats and the possible metabolic repercussions to this tissue. Our data show that pinealectomy indeed has impacts on molecular events: it abolishes the daily pattern of the expression of Clock, Per2, and Cry1 clock genes and Pparγ expression, significantly increases the amplitude of daily expression of Rev‐erbα, and affects the pattern of and impairs adipokine production, leading to a decrease in leptin levels. However, regarding some metabolic aspects of adipocyte functions, such as its ability to synthesize triacylglycerols from glucose along 24 hr, was not compromised by pinealectomy, although the daily profile of the lipogenic enzymes expression (ATP‐citrate lyase, malic enzyme, fatty acid synthase, and glucose‐6‐phosphate dehydrogenase) was abolished in pinealectomized animals.  相似文献   
2.
Survival after resection of colorectal liver metastases has traditionally been associated with clinicopathologic factors. We sought to investigate whether echogenicity of colorectal liver metastasis as assessed by intraoperative ultrasound (IOUS) was a prognostic factor after hepatic resection. Prospective data on tumor IOUS appearance were collected in 84 patients who underwent hepatic resection for colorectal liver metastasis. Images were digitally recorded, blindly reviewed, and scored for echogenicity (hypo-, iso-, or hyperechoic). The median tumor number was 1 and the median tumor size was 5.0 cm. At the time of surgery, the IOUS appearance of the colorectal liver metastases were hypoechoic in 35 (41.7%) patients, isoechoic in 37 (44.0%) patients, and hyperechoic in 12 (14.3%) patients. Traditional clinicopathologic prognostic factors were similarly distributed among the three echogenicity groups (all p > 0.05). Patients with a hypoechoic lesion had a significantly shorter median survival (30.2 months) compared with patients who had either an isoechoic (53.2 months) or hyperechoic (42.3 months) lesion (p = 0.005). The 5-year survival after hepatic resection of colorectal liver metastasis was also associated with the echogenic appearance of the lesion (hypoechoic 14.4 vs isoechoic 37.4 vs hyperechoic 46.2%) (p < 0.05). Intraoperative ultrasound echogenicity should be considered a prognostic factor after hepatic resection of metastatic colorectal cancer. This study was presented at the 47th annual meeting of The Society for Surgery of the Alimentary Tract, Los Angeles, CA, USA, 22 May 2006.  相似文献   
3.
BACKGROUND/PURPOSE: The polysaccharide-rich composition of Aloe vera extracts (Aloe barbadensis Miller), often used in cosmetic formulations, may impart moisturizing properties to the product. The aim of this study was to evaluate the effect of cosmetic formulations containing different concentrations of freeze-dried Aloe vera extract on skin hydration, after a single and a 1- and 2-week period of application, by using skin bioengineering techniques. METHODS: Stable formulations containing 5% (w/w) of a trilaureth-4 phosphate-based blend were supplemented with 0.10%, 0.25% or 0.50% (w/w) of freeze-dried Aloe vera extract and applied to the volar forearm of 20 female subjects. Skin conditions in terms of the water content of the stratum corneum and of transepidermal water loss (TEWL) (Corneometer CM 825 and Tewameter TM 210) were analysed before and after a single and 1- and 2-week period of daily application. RESULTS: After a single application, only formulations supplemented with 0.25% and 0.50% (w/w) of Aloe vera extract increased the water content of the stratum corneum, while after the 2-week period application, all formulations containing the extract (0.10%, 0.25% and 0.50%) had the same effect, in both cases as compared with the vehicle. TEWL was not modified after a single and after 1- and 2-week period of application, when compared with the vehicle. CONCLUSION: Our results show that freeze-dried Aloe vera extract is a natural effective ingredient for improving skin hydration, possibly through a humectant mechanism. Consequently, it may be used in moisturizing cosmetic formulations and also as a complement in the treatment of dry skin.  相似文献   
4.
5.
Tyrosine hydroxylase-like immunoreactive (TH-IR) neurons with morphological features of interneurons were found throughout the human cerebral cortex. Quantitative estimates in 14 different cytoarchitectonic areas revealed a specific regional distribution pattern, neurons being less dense in primary cortical areas and denser in higher order associative areas and some limbic related areas. A partial relationship was noted between the density of labeled neurons and that of the known dopaminergic innervation. The role of the cortical TH-IR neurons in catecholaminergic function, however, remains unclear since the presence of other catecholaminergic synthesizing enzymes, dopamine-β-hydroxylase and DOPA decarboxylase, could not be demonstrated at their level. Similar neurons have been observed transiently in the rodent cortex during development; their persistence and topographical extension in the human brain warrants further study on their possible functional role.  相似文献   
6.
We report the case of a 4-year-old child with an atypical presentation of an aspirated unwitnessed foreign body in the airway. During an attempt to obtain a biopsy of what appeared to be a mucosal growth, the foreign body was removed. This may be the first report of foreign body removal in a child this young, using a flexible fiberoptic bronchoscope. Pediatr Pulmonol. 1994; 18:51–52. © 1994 Wiley-Liss. Inc.  相似文献   
7.
Carcinoma of the papilla of Vater is classified as periampullary cancer representing 5% of all gastrointestinal tract malignancies. Early and accurate diagnosis is important for those patients with a tumor of the papilla, as the prognosis is more favorable than in other periampullary neoplasms. Endoscopically obtained biopsies from suspicious papillae can detect an early tumor, although even for skilled pathologists it is often difficult to differentiate carcinomas from noninvasive lesions on the basis of forceps biopsies. The purpose of this study was to assess the preoperative diagnostic accuracy of duodenoscopy appearance and biopsy in all cases with suspicion of tumor. Thirty patients with suspicion of carcinoma of the papilla of Vater and with final diagnosis established by pancreatoduodenectomy were included in this retrospective study. In each case, a comparison was made between endoscopic biopsy and duodenoscopic appearance. Duodenoscopic appearance sensitivity and accuracy for malignancy were 86% and 83%, respectively, whereas endoscopic biopsy sensitivity and accuracy were 65% and 67%, respectively. Although preoperative diagnosis of carcinoma of the papilla of Vater is useful for making therapeutic decisions, the diagnostic value of the endoscopic appearance was superior to endoscopic biopsy in this series. Presented at the 2003 American Hepato-Pancreato-Biliary Association Congress, Miami, Florida, February 27-March 3, 2003. Supported by FADA-CAPES/PROP 200J (M.L.D.).  相似文献   
8.
Minocycline is a useful adjuvant therapy for pemphigus   总被引:1,自引:0,他引:1  
Pemphigus is an autoimmune blistering disease with high mortality if untreated. The cases of 10 patients who had minocycline 100 mg daily added as adjuvant therapy are reported. Prior to the use of minocycline, all patients had active disease, nine were on prednisolone (10–40 mg) and five were on azathioprine (100–200 mg). The response was assessed on clinical improvement and reduction of immunosuppressive (IS) drugs. It was graded into four categories: major, minor, equivocal and no significant response. A major response was seen in four patients, minor in two, equivocal in one and no improvement in three patients. The prednisolone dose in the six responders was reduced to 0–6 mg (0 mg in three patients), with an average decrease of 21 mg. The average time to respond was 8 months. Of the six responders, three were on azathioprine, which was ceased in two patients and reduced by two-thirds in the other patient. No patient ceased minocycline because of side effects. In conclusion, minocycline 100 mg daily is a simple, safe and well tolerated treatment that should be tried in patients with pemphigus to reduce disease activity and/or the dose of potent IS agents.  相似文献   
9.
A flow injection-fluorimetric determination of thiamine is reported. The procedure is based on the oxidation of the analyte with potassium hexacyanoferrate(III) immobilized on an anionic exchange resin; the fluorescence is monitored in aqueous basic solution. Concentrations of the vitamin of 0.1–4 ppm have been determined; the relative standard deviation was 1.8%. The injection rate was 28 samples/h. The influence of other substances and the determination of the drug in a pharmaceutical formulation are also reported.  相似文献   
10.
Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominant disorder caused by the expansion of a polymorphic (CAG)(n) tract, which is translated into an expanded polyglutamine tract in the ataxin-2 protein. Although repeat length and age at disease onset are inversely related, approximately 50% of the age at onset variance in SCA2 remains unexplained. Other familial factors have been proposed to account for at least part of this remaining variance in the polyglutamine dis-orders. The ability of polyglutamine tracts to interact with each other, as well as the presence of intra-nuclear inclusions in other polyglutamine disorders, led us to hypothesize that other CAG-containing proteins may interact with expanded ataxin-2 and affect the rate of protein accumulation, and thus influence age at onset. To test this hypothesis, we used step-wise multiple linear regression to examine 10 CAG-containing genes for possible influences on SCA2 age at onset. One locus, RAI1, contributed an additional 4.1% of the variance in SCA2 age at onset after accounting for the effect of the SCA2 expanded repeat. This locus was further studied in SCA3/Machado-Joseph disease (MJD), but did not have an effect on SCA3/MJD age at onset. This result implicates RAI1 as a possible contributor to SCA2 neurodegeneration and raises the possibility that other CAG-containing proteins may play a role in the pathogenesis of other polyglutamine disorders.  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