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   497篇
  免费   37篇
耳鼻咽喉   1篇
儿科学   4篇
妇产科学   3篇
基础医学   46篇
口腔科学   15篇
临床医学   46篇
内科学   186篇
皮肤病学   3篇
神经病学   41篇
特种医学   21篇
外科学   75篇
预防医学   11篇
药学   20篇
中国医学   1篇
肿瘤学   61篇
  2024年   2篇
  2023年   12篇
  2022年   4篇
  2021年   49篇
  2020年   32篇
  2019年   27篇
  2018年   29篇
  2017年   22篇
  2016年   15篇
  2015年   27篇
  2014年   22篇
  2013年   25篇
  2012年   49篇
  2011年   33篇
  2010年   15篇
  2009年   19篇
  2008年   15篇
  2007年   21篇
  2006年   14篇
  2005年   11篇
  2004年   19篇
  2003年   14篇
  2002年   11篇
  2001年   5篇
  2000年   10篇
  1999年   8篇
  1998年   5篇
  1997年   2篇
  1996年   3篇
  1995年   3篇
  1994年   1篇
  1993年   1篇
  1992年   1篇
  1991年   1篇
  1989年   1篇
  1987年   5篇
  1980年   1篇
排序方式: 共有534条查询结果,搜索用时 203 毫秒
1.
Poly(vinyl alcohol) (PVA) was coated onto polyethylene (PE) films by a repetitive adsorption and drying process, and then the PVA-coated PE films were alternately immersed into aqueous solutions of Ca2+ and CO3(2-) ions (alternate soaking cycles), to deposit calcium carbonate (CaCO3) onto the films. The PVA coating was essential for the CaCO3 deposition. The amount of CaCO3 deposited increased with an increasing number of cycles. Scanning electron microscopic observations and attenuated total reflection spectra revealed the presence of both calcite and aragonite as the crystal structures of CaCO3 on the film. L929 fibroblast cells adhered and proliferated on these CaCO3-deposited PE films, as well as the hydroxyapatite-coated PE films previously prepared. It was found that the PVA coating and the subsequent deposition of calcium salts on certain films facilitated cell compatibility.  相似文献   
2.
Clinical and genomic features of prostate cancer (PCa) vary considerably between Asian and Western populations. PTEN loss is the most frequent abnormality in intraductal carcinoma of the prostate (IDC-P) in Western populations. However, its prevalence and significance in Asian populations have not yet been well studied. In the present study, we evaluated PTEN expression in IDC-P in a Japanese population and its association with ERG expression. This study included 45 and 59 patients with PCa with and without IDC-P, respectively, who underwent radical prostatectomy. PTEN loss was observed in 10 patients with PCa with IDC-P (22%) and nine patients with PCa without IDC-P (17%). ERG expression was relatively frequent in patients with PCa with PTEN loss, although a significant difference was not observed. The co-occurrence of PTEN loss and ERG expression was observed in four patients with PCa with IDC-P and one without IDC-P. PTEN loss and ERG expression did not affect progression-free survival, regardless of the presence of IDC-P. The frequency of PTEN loss in IDC-P is lower in Asian patients than in Western patients. Our results indicate that mechanisms underlying IDC-P in Asian populations are different from those of Western populations.  相似文献   
3.
The hypothalamic growth hormone (GH)-releasing hormone (GHRH) promotes non-rapid eye movement sleep (NREMS). Insulin-like growth factor-1 (IGF-1) acts as a negative feedback in the somatotropic axis inhibiting GHRH and stimulating somatostatin. To determine whether this feedback alters sleep, rats and rabbits were injected intracerebroventricularly (i.c.v.) with IGF-1 (5.0 and 0.25 microgram, respectively) and the sleep-wake activity was studied. Compared to baseline (i.c.v. injection of physiological saline), IGF-1 elicited prompt suppressions in both NREMS and rapid eye movement sleep (REMS) in postinjection hour 1 in rats and rabbits. The intensity of NREMS (characterized by the slow wave activity of the EEG by means of fast-Fourier analysis) was significantly enhanced 7 to 11 h postinjection in rats. Plasma GH concentrations were measured in 30-min samples after i.c.v. IGF-1 injection in rats and a significant suppression of GH secretion was observed 30 min postinjection. The simultaneous inhibition of the somatotropic axis and sleep raises the possibility that the sleep alterations also result from an IGF-1-induced suppression of GHRH. The late increases in NREMS intensity are attributed to metabolic actions of IGF-1 or to a release of GHRH from the IGF-1-induced inhibition.  相似文献   
4.
5.
BackgroundThe purpose of this study was to investigate residual acetabular retroversion after skeletal maturity in patients with Pemberton osteotomy.Patients and methodsWe compared 40 hips in 36 patients treated with a Pemberton osteotomy (Pemberton group) and 30 hips in 26 patients treated only with a Pavlik harness (Rb group) for developmental dysplasia of the hip. The average age at operation in the Pemberton group was 94.5 months and the follow-up duration was 151.8 months. Radiographic parameters included the acetabular index (a angle) and the center-edge angle of Wiberg, preoperatively and at skeletal maturity. We examined the crossover sign (COS) at the latest follow-up as a sign of acetabular retroversion (AR). We compared the parameters between the two groups and examined the risk factors for acetabular retroversion using a multivariate Cox model.ResultA COS (+) was significantly more frequent in the Pemberton group compared to the Rb group [15 hips (37.5 %) vs 3 hips (10 %); p = 0.0077]. In the Pemberton group, the average age at operation in COS (+) hips was significantly older than that in COS (—) hips (126.9 vs 72.8 months; p = 0.0005). The preoperative α angle did not vary between hips with and without COS; however, the postoperative α angle was significantly smaller in COS (+) hips. A multiple logistic regression analysis for prediction of COS (+) showed that the age at operation and the amount change of α angle were significant predictors for COS (+) hips. The cut-off of the age at operation was 7 years and 9 months old.ConclusionsAR was present in 37.5 % of the hips in the Pemberton group after skeletal maturity. Remodeling of acetabular version was observed in younger patients; however, hips in older patients (> 8 years) at the time of operation and greater degrees of correction tended to result in AR.  相似文献   
6.
The present patient developed a severe rectal ulcer more than 1 month after having received external beam radiation therapy for prostate cancer. Surveillance endoscopy every 3 months demonstrated healing of this rectal ulcer using a novel therapy. He was given enemas with ecabet sodium, which provides physical protection and promotes healing by increasing prostaglandin E2, and this process induced squamous metaplasia that halted the progression of the ulcer of radiation proctitis as a late‐phase reaction. Intrapapillary capillary loops were visualized with magnified narrow band imaging at the healing ulcer site as seen via the esophagus and, moreover, demonstrated histologically.  相似文献   
7.
The requirement for well spread out chromosomes for the cytogenetic analysis of primary gastrointestinal tumors led us to develop new techniques. These techniques involved two main procedures: (1) preliminary incubation with culture medium in the presence of collagenase, Dispase, and colcemid, for 3h, and (2) treatment with an extremely hypotonic solution (0.044 M KCl) for 30 min. The techniques were applied to 11 gastrointestinal malignancies (including 1 early gastric cancer and 1 metastatic liver lesion of colon cancer) and significant increases (P<0.01) in the number of metaphases of analyzable karyotypes were obtained, compared with a previous method in which the standard hypotonic molarity of KCL (0.075 M) was employed. The mean value for metaphase numbers of the analyzable karyotypes was 37.0±3.7% in the 5 gastric cancers and 44.7±4.8% in the 5 colon cancers and 1 metastatic lesion. These values were three times and more than twice, respectively, the values obtained by the previous method. A fluorescence in situ hybridization (FISH) study was carried out on one cologenic tumor, the α-satellite centromere-specific probe 17 being used. Deletion of the long arm of chromosome 17 was demonstrated. The method proposed here could yield a sufficient number of metaphases without the use of tissue culture that might cause alteration of karyotype. It can be employed with small biopsy specimens and in studies utilizing the FISH technique.  相似文献   
8.
9.
BACKGROUND: The development of well-matured fibrosis in usual interstitial pneumonia (UIP) is strongly associated with an unfavorable outcome of patients with idiopathic pulmonary fibrosis (IPF). However, differences in the rates of development are likely to result in variable clinical courses in IPF patients. OBJECTIVE: We tried to evaluate the progression of honeycombing and ground-glass opacity on CT using a scoring system, and to examine those serial changes in the clinical course of disease. METHODS: A hospital-based, retrospective cohort study. Twenty-three patients with IPF diagnosed as UIP by surgical lung biopsy were analyzed during the initial examination by scoring the presence of honeycombing (HC: range, 0-24) and ground-glass opacity (GG: range, 0-24) on CT scan. We also compared the serial changes observed in the CT scores (interval: 2-42 months, 2-6 examinations). RESULTS: (1) The serial change in the HC score in treated patients (n = 10) was similar to that in untreated patients (n = 16); (2) the HC score at the time of the initial examination and the rate of HC progression were both higher in the non-surviving patients (HC 12.3 +/- 3.7, mean +/- SD; deltaHC 4.2 +/- 1.3 per year) than in the surviving patients (HC 5.8 +/- 2.7; deltaHC 1.2 +/- 0.7 per year) (p < 0.05); (3) the GG score did not correlate with the HC score at any of the examinations; (4) the HC score was higher in the lower lung field than in the upper and middle lung fields. CONCLUSIONS: Scoring of the honeycombing and its serial changes using the high-resolution computed tomography scoring method was useful for predicting the prognosis in patients with IPF/UIP. Corticosteroid treatment did not prevent the progression of HC.  相似文献   
10.
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