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   6137篇
  免费   449篇
  国内免费   57篇
耳鼻咽喉   26篇
儿科学   134篇
妇产科学   114篇
基础医学   942篇
口腔科学   103篇
临床医学   582篇
内科学   1610篇
皮肤病学   105篇
神经病学   742篇
特种医学   154篇
外科学   500篇
综合类   15篇
一般理论   1篇
预防医学   401篇
眼科学   65篇
药学   497篇
中国医学   13篇
肿瘤学   639篇
  2024年   8篇
  2023年   66篇
  2022年   158篇
  2021年   268篇
  2020年   133篇
  2019年   166篇
  2018年   234篇
  2017年   169篇
  2016年   188篇
  2015年   244篇
  2014年   279篇
  2013年   320篇
  2012年   534篇
  2011年   551篇
  2010年   276篇
  2009年   244篇
  2008年   438篇
  2007年   454篇
  2006年   389篇
  2005年   389篇
  2004年   324篇
  2003年   326篇
  2002年   246篇
  2001年   33篇
  2000年   15篇
  1999年   19篇
  1998年   29篇
  1997年   28篇
  1996年   24篇
  1995年   15篇
  1994年   17篇
  1993年   12篇
  1992年   7篇
  1991年   10篇
  1990年   5篇
  1989年   3篇
  1988年   4篇
  1986年   1篇
  1985年   1篇
  1984年   2篇
  1983年   3篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
  1979年   1篇
  1973年   1篇
  1971年   1篇
  1970年   1篇
  1969年   2篇
  1918年   1篇
排序方式: 共有6643条查询结果,搜索用时 0 毫秒
981.

Purpose

Knowledge of tumor mutational status has become a priority for effective NSCLC-tailored treatment. NSCLC diagnosis is more often reached through biopsy; thus, there is a clear need to implement for routine tumor molecular profiling on small cytological samples. This work aims to screen and compare the EGFR and KRAS mutational prevalence in fresh tumor cells and in corresponding routinely processed samples derived from trans-thoracic fine-needle aspiration. The latter currently represents the most appropriate diagnostic procedure in case of peripheral lesions, such as adenocarcinomas, which account for almost 40 % of all NSCLCs and for the highest EGFR mutational rates.

Methods

Two hundred and forty-four patients carrying peripheral lung masses underwent CT-guided aspiration. The obtained material was split, and a part was addressed to conventional histopathological analysis while the remaining one was stored at ?20 °C. In case of confirmation of adenocarcinoma, tumor genomic DNA was extracted from both fresh and fixed material, and EGFR and KRAS sequencing was performed.

Results

We identified 136 adenocarcinomas; from 134, we could recover enough material for the study. A full match was demonstrated between EGFR/KRAS mutational prevalences through the two approaches tested. We found EGFR mutations in 13 patients (9.7 %); 7 were females and 11 never or former smokers. KRAS mutations occurred in 20 (14.9 %) patients. EGFR and KRAS mutations were mutually exclusive.

Conclusions

Mutational screening on fresh cancer cells is an achievable, safe and cost-effective procedure which might allow routinely tumor molecular profiling as powerful integration of conventional histopathological analysis.  相似文献   
982.
Since obesity seems to play a causal role in both obstructive sleep apnea/hypopnea syndrome (OSAHS) and type 2 diabetes, the question arises whether diet-induced weight loss is equally efficacious in type 2 diabetic patients with and without OSAHS. The present study was aimed to investigate the effect of 1 week very low calorie diet (VLCD) on oxygen desaturation index (ODI) and on glucose regulation in OSAHS versus non-OSAHS patients. Fourteen patients with type 2 diabetes mellitus and morbid obesity were enrolled. According to ODI, patients were divided into 2 groups (with and without OSAHS) and evaluated by a hyperglycemic clamp study, before and after a 7 day-VLCD. After a VLCD, a significant reduction of anthropometric parameters, in the overall group and in subgroups, was observed. M-value and acute insulin response increased significantly only in patients without obstructive sleep apnea (990.10 ± 170.19 vs. 1,205.22 ± 145.73 μmol min?1 m?2, p = 0.046; ?1.05 ± 8.40 vs. 48.26 ± 11. 90 pmol/L, p = 0.028, respectively). The average 24-h heart rate (24-h HR) fell significantly (p = 0.05), primarily because of a decrease during daytime (p = 0.041), in the whole group. In conclusion, we observed that morbidly obese patients with type 2 diabetes and OSAHS are specifically resistant to the acute beneficial effects of VLCD on metabolic parameters. Our preliminary observation deserves further investigation to clarify the pathogenetic mechanisms involved.  相似文献   
983.
BackgroundNPR3, located on human chromosome 5 (5p14–p13), encodes the natriuretic peptide receptor type C (NPR-C) that is mainly known as the natriuretic peptide clearance receptor. Involvement of NPR3 in susceptibility to cardiovascular diseases, i.e. hypertension, has been previously shown. With regard to stroke predisposition, evidence for a potential role of genetic variation within or nearby NPR3 has been suggested by a previous genome wide association study.MethodsWe investigated the contribution to early-onset ischemic stroke susceptibility of the NPR3 ? 55 C > A transition by genotyping this variant in an Italian cohort of 368 cases and 335 controls.ResultsIn a multivariable logistic regression analysis adjusting for age, gender, hypertension, hypercholesterolemia, smoking habit and diabetes, a significant association of the ? 55 AA genotype with stroke was observed (OR = 3.2, 95% CI 1.2–8.3, p = 0.016). Remarkably, the polymorphism remained associated with stroke after adjusting for hypertensive status.ConclusionOur observation obtained in an Italian cohort of early onset ischemic strokes suggests that a NPR3 promoter gene variant could have a role on cerebrovascular disease susceptibility.  相似文献   
984.
The use of nucleic acid (NA) amplification techniques has transformed the diagnosis of viral infections of the central nervous system (CNS). Because of their enhanced sensitivity, these methods enable detection of even low amounts of viral genomes in cerebrospinal fluid. Following more than 10 years of experience, the polymerase chain reaction or other NA-based amplification techniques are nowadays performed in most diagnostic laboratories and have become the test of choice for the diagnosis of several viral CNS infections, such as herpes encephalitis, enterovirus meningitis and other viral infections occurring in human immunodeficiency virus-infected persons. Furthermore, they have been useful to establish a viral etiology in neurological syndromes of dubious origin and to recognise unusual or poorly characterised CNS diseases. Quantitative methods have provided a valuable additional tool for clinical management of these diseases, whereas post-amplification techniques have enabled precise genome characterisation. Current efforts are aiming at further improvement of the diagnostic efficiency of molecular techniques, their speed and standardisation, and to reduce the costs. The most relevant NA amplification strategies and clinical applications of to date will be the object of this review.  相似文献   
985.
OBJECTIVE AND PATIENTS: Patients with acromegaly (12 women, 26 men) and a control group (36 women, 50 men) were chosen for cephalometry to assess the size, shape and positional characteristics of the craniofacial bones and the upper airways.RESULTS: When compared with the controls, patients of both sexes with acromegaly were found to have significant anomalies in the orofacial skeleton: increased facial height, elongated ascending ramus mandibulae and greater basion-supramentale distance, a negative difference between maxillary and mandibular protrusions, enlarged lower part of the gonion angle and of the angle of inclination of the maxilla, as well as alterations in the neurocranium: enlargement of sella turcica and of sinus frontalis and protrusion of the supraorbital ridges. As for the soft tissues, patients with acromegaly exhibited an elongated soft palate and a diminished angle between the uvular axis and the palatal plane. A comparison between the cephalometric parameters of patients with active acromegaly and those without active disease revealed no significant differences in either sex.CONCLUSION: Patients with acromegaly exhibited an enlargement of all parts of the neurocranium and orofacial bones except the maxilla. The greatest anomaly was seen in the mandible, with greater enlargement of the ascending ramus than of the body of the mandible. The shape of this bone was also altered.  相似文献   
986.
Gelatin–dextran hydrogel scaffolds (G-PEG-Dx) were evaluated for their ability to activate the bone marrow human mesenchymal stromal cells (BM-hMSCs) towards mineralization. G-PEG-Dx1 and G-PEG-Dx2, with identical composition but different architecture, were seeded with BM-hMSCs in presence of fetal bovine serum or human platelet lysate (hPL) with or without osteogenic medium. G-PEG-Dx1, characterized by a lower degree of crosslinking and larger pores, was able to induce a better cell colonization than G-PEG-Dx2. At day 28, G-PEG-Dx2, with hPL and osteogenic factors, was more efficient than G-PEG-Dx1 in inducing mineralization. Scanning electron microscopy (SEM) and Raman spectroscopy showed that extracellular matrix produced by BM-hMSCs and calcium-positive mineralization were present along the backbone of the G-PEG-Dx2, even though it was colonized to a lesser degree by hMSCs than G-PEG-Dx1. These findings were confirmed by matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI), detecting distinct lipidomic signatures that were associated with the different degree of scaffold mineralization. Our data show that the architecture and morphology of G-PEG-Dx2 is determinant and better than that of G-PEG-Dx1 in promoting a faster mineralization, suggesting a more favorable and active role for improving bone repair.  相似文献   
987.
The clinical relevance of the urokinase receptor (uPAR) as a prognostic marker in ovarian cancer is well documented. We have shown that the uPAR sequence corresponding to 84-95 residues, linking D1 and D2 domains (uPAR84-95), drives cell migration and angiogenesis in a protease-independent manner. This study is aimed at defining the contribution of uPAR84-95 sequence to invasion of ovarian cancer cells. Now, we provide evidence that the ability of uPAR-expressing ovarian cancer cells to cross extra-cellular matrix and mesothelial monolayers is prevented by specific inhibitors of PAR84-95 sequence. To specifically investigate uPAR84-95 function, uPAR-negative CHO-K1 cells were stably transfected with cDNAs coding for uPAR D2 and D3 regions and exposing (uPARD2D3) or lacking (uPARΔD2D3) the 84–95 sequence. CHO-K1/D2D3 cells were able to cross matrigel, mesothelial and endothelial monolayers more efficiently than CHO-K1/ΔD2D3 cells, which behave as CHO-K1 control cells. When orthotopically implanted in nude mice, tumor nodules generated by CHO-K1/D2D3 cells spreading to peritoneal cavity were more numerous as compared to CHO-K1/ΔD2D3 cells. Ovarian tumor size and intra-tumoral microvessel density were significantly reduced in the absence of uPAR84-95. Our results indicate that cell associated uPAR promotes growth and abdominal dissemination of ovarian cancer cells mainly through its uPAR84-95 sequence.  相似文献   
988.
989.
The present study assessed the influence of food intake on acoustic radiation force impulse elastography (ARFI) measurements. Seventy-three healthy volunteers were included: 57 subjects in the study group (on whom ARFI measurements were performed first in fasting condition, followed by measurements made 1h and 3h after food intake); and 16 subjects in the control group (on whom ARFI measurements were performed 3 times during a 3-h interval without eating). All subjects included in the study group received the same standard solid meal. In the study group, the mean liver stiffness (LS) values by ARFI increased significantly 1 h after food intake (1.51 ± 0.40 m/s vs. 1.27 ± 0.23, p = 0.003), but 3 h after the meal the differences were no longer significant (1.46 ± 0.51 vs. 1.27 ± 0.23, p = 0.06). In the control group, the mean LS values were similar in all 3 measurements. In conclusion, food intake significantly increased the LS values, thus ARFI measurements should be performed in fasting conditions.  相似文献   
990.
Our study compared three elastographic methods—transient elastography (TE), acoustic radiation force impulse (ARFI) imaging and supersonic shear imaging (SSI)—with respect to the feasibility of their use in liver fibrosis evaluation. We also compared the performance of ARFI imaging and SSI, with TE as the reference method. The study included 332 patients, with or without hepatopathies, in which liver stiffness was evaluated using TE, ARFI and SSI. Reliable measurements were defined as a median value of 10 (TE, ARFI imaging) or 5 (SSI) liver stiffness measurements with a success rate ≥60% and an interquartile range interval <30%. A significantly higher percentage of reliable measurements were obtained using ARFI than by using TE and SSI: 92.1% versus 72.2% (p < 0.0001) and 92.1% versus 71.3% (p < 0.0001). Higher body mass index and older age were significantly associated with inability to obtain reliable measurements of liver stiffness using TE and SSI. In 55.4% of patients, reliable liver stiffness measurements were obtained using all three elastographic methods, and ARFI imaging and TE were similarly accurate in diagnosing significant fibrosis and cirrhosis, with TE as the reference method.  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