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   2648篇
  免费   158篇
  国内免费   22篇
耳鼻咽喉   14篇
儿科学   96篇
妇产科学   47篇
基础医学   394篇
口腔科学   47篇
临床医学   210篇
内科学   764篇
皮肤病学   37篇
神经病学   261篇
特种医学   48篇
外科学   188篇
综合类   5篇
预防医学   134篇
眼科学   6篇
药学   277篇
中国医学   21篇
肿瘤学   279篇
  2024年   2篇
  2023年   14篇
  2022年   60篇
  2021年   77篇
  2020年   49篇
  2019年   60篇
  2018年   75篇
  2017年   60篇
  2016年   71篇
  2015年   87篇
  2014年   99篇
  2013年   129篇
  2012年   212篇
  2011年   217篇
  2010年   103篇
  2009年   139篇
  2008年   217篇
  2007年   184篇
  2006年   158篇
  2005年   174篇
  2004年   173篇
  2003年   128篇
  2002年   122篇
  2001年   20篇
  2000年   12篇
  1999年   14篇
  1998年   31篇
  1997年   23篇
  1996年   17篇
  1995年   15篇
  1994年   7篇
  1993年   11篇
  1992年   4篇
  1991年   2篇
  1990年   8篇
  1989年   4篇
  1988年   7篇
  1987年   4篇
  1986年   3篇
  1985年   3篇
  1984年   5篇
  1983年   3篇
  1982年   5篇
  1980年   4篇
  1979年   2篇
  1978年   3篇
  1975年   2篇
  1973年   2篇
  1967年   3篇
  1890年   2篇
排序方式: 共有2828条查询结果,搜索用时 31 毫秒
111.
Nowadays, advanced extraction techniques and highly sensitive metabolic profiling methods are effectively employed to get new information on plant chemical constituents. Among them wild medicinal plants or their parts, with large and ancient use in folk medicine, are investigated for their potential functional use and cultivation. In this context, Inula viscosa leaves engaged our attention. A simple experimental design, based on Soxhlet extraction and chromatographic fractionation, allowed us to obtain the investigated polyphenol fraction (IvE). UHPLC-HRMS analyses revealed shikimoyl depsides of caffeic acid and unusual dihydrobenzofuran lignans as main secondary metabolites. These compounds, together with cinchonain-type phenols, and hydroxycinnamoyl flavonol glycosides, are reported for the first time in inula. Overall, forty-three secondary metabolites were identified. The extract exerted a remarkable antiradical activity towards DPPH and ABTS+•. Furthermore, it was able to inhibit cell viability and mitochondrial redox activity of neuroblastoma, hepatoblastoma and colon carcinoma cells, whereas it did not affect cell density of HaCaT cells immortalized human keratinocytes. As detected by the oxidant-sensing probe 2′,7′-dichlorodihydrofluorescein diacetate, the inhibitory responses seemed to be related to IvE-induced increase of intracellular reactive oxygen species (ROS). The obtained results highlighted that inula leaves, nowadays even undervalued and unexplored, could be considered a renewable source of nutraceutical compounds.  相似文献   
112.
The Bartholin's gland cyst is a condition that occurs in approximately 2% of women, most of whom are of reproductive age. Although benign, it is associated with significant patient discomfort. Definitive treatment involves the surgical removal of the entire cyst. The objective of this study was to describe an alternative conservative surgical technique with CO(2) laser adopted in our institution and to evaluate the feasibility, complication rate, and results obtained with this technique in an office setting. Our study showed that CO(2) laser treatment of the Bartholin's gland cyst can be carried out safely in an outpatient setting, with minimum patient discomfort and high long-term cure rates.  相似文献   
113.
114.
Renal interstitial fibrosis is a major complication of cisplatin treatment, due to the increased accumulation of extracellular matrix (ECM) proteins whose remodeling is important for the development of normal tissues; indeed, its malfunction might play a role in the etiology of various diseases.Biopharmacological evaluations suggest that l-carnitine can prevent cardiac metabolic damage caused by doxorubicin, as well as can inhibit cisplatin-induced injury in the kidney and in the small intestine, without any interference with the drug's antitumoral properties. Since the glomerular basement membrane and the mesangial matrix constitute the ECM of the renal glomerulus, we examined the localization and expression of MMP-9 and TIMP-3 in normal rat kidney and the changes in their expression over a period of time by treatment with cisplatin, with and without l-carnitine. MMP-9 immunoreaction in cisplatin-treated rat kidney tissue suggests an involution of the basal membrane, an alteration of ECM components and low glomerular function, due to the increased thickness of the mesangium. Our results suggest that the matrix remodeling by MMP-9 and TIMP-3, in the later stages, can play an important role in the development of glomerular sclerosis and interstitial fibrosis after cisplatin treatment. It can also be postulated that l-carnitine protects from cisplatin injury, by modulating the relationship between MMP-9 and TIMP-3.  相似文献   
115.
Multivariate curve resolution—alternating least squares (MCR‐ALS) has been applied to data collected from UV spectrophotometric analysis of melatonin samples exposed to light with varying irradiance power. MCR‐ALS was able to explain the degradation kinetics of this drug, deducing the pure spectra and concentration changes of the different species present throughout the entire process. Possible rotational ambiguities associated with MCR solutions were investigated and their extent was evaluated. The extent of the rotation ambiguity was estimated from the band boundaries of feasible solutions calculated using the MCR‐BANDS procedure. The use of a non‐linear fitting routine allowed improving kinetic information and provided a method of evaluation of the rate constants of the degradation process. The degradation pathway was found to follow a first‐order reaction model, in which melatonin underwent photo‐oxidation of the indole ring to give a formylamine group. Kinetics of the reaction was shown to be dependent on irradiation conditions, with an increase of the rate constants when light power also increased. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   
116.
BACKGROUND AND AIMS: The metabolic profile and morphologic aspects of normal and pathologic human gastric mucosa were studied. The aim of the present research was the application of ex vivo high-resolution magic angle spinning magnetic resonance spectroscopy (HR-MAS MRS) to the human gastric tissue to get information on the molecular steps involved in gastric carcinogenesis and the identification of biochemical markers useful for the development of in vivo MRS methodologies to diagnose gastric pathologies in clinical situations. METHODS: Twelve normal subjects, five with autoimmune atrophic gastritis, five with Helicobacter pylori infection, and five with adenocarcinoma were examined. Ten biopsies were taken during endoscopy from each patient. Specimens from carcinoma were also obtained during gastrectomy. Of the 10 biopsies, 4 were used for histologic evaluation, 4 were fixed in glutaraldehyde and processed for transmission and scanning electron microscopy, and 2 were immersed in liquid nitrogen and stored at -85 degrees C for monodimensional and bidimensional ex vivo HR-MAS MRS analysis. RESULTS: Ex vivo HR-MAS MRS identified glycine, alanine, free choline, and triglycerides as possible molecular markers related to the human gastric mucosa differentiation toward preneoplastic and neoplastic conditions. Ultrastructural studies of autoimmune atrophic gastritis and gastric adenocarcinoma revealed lipid accumulations intracellularly and extracellularly associated with a severe prenecrotic hypoxia and mitochondria degeneration. CONCLUSIONS: This is the first report of synergic applications of ex vivo HR-MAS MRS and electron microscopy in studying the human gastric mucosa differentiation. This research provides useful information about some molecular steps involved in gastric carcinogenesis. The biochemical data obtained on gastric pathologic tissue could represent the basis for clinical applications of in vivo MRS.  相似文献   
117.
Among the chitosan derivatives, trimethylchitosan (TMC) has been shown to have penetration enhancement properties also in intestinal environment. In addition, the use of nanoparticulate systems has the advantage of protecting peptidic drugs from intestinal degradations, due to internalisation behaviour. Therefore, the aim of this paper was to evaluate nanoparticulate systems based on TMC. In particular the mucoadhesive and absorption enhancement properties of nanoparticles based on TMC with different quaternization degree (QD) intended for the intestinal administration of macromolecules (peptides) have been evaluated. Comparison with chitosan (CS.HCl) nanoparticles was made. The nanoparticles were loaded with fluorescein isothiocyanate dextran (FD4, MW 4400 Da), used as the model macromolecule. The intestinal penetration enhancement properties of nanoparticles were investigated in an in vitro Caco-2 cell model and an ex vivo rat jejunum model. The mucoadhesion of the nanosystems was evaluated using excised rat jejunum. All of the nanoparticulate systems interacted with the Caco-2 cells decreasing the transepithelial electric resistance (TEER) and increasing Lucifer Yellow (LY) Papp (paracellular pathway marker). All the nanosystems improved FD4 Papp, with the exception of the nanoparticles based on TMC with the highest QD. In this case an entrapment of nanoparticles into Caco-2 cells was supposed. Analogous results were obtained using the excised rat jejunum model. The increase in QD of TMC was seen to favour the mucoadhesion, resulting in a prolonged residence time on intestinal mucosa. The nanoparticle penetration into excised rat jejunum tissue, observed by means of CLSM, suggested that the mucoadhesive properties delayed the absorption of nanoparticles, however they produced an increase in the contact time with intestinal epithelium, offering a better chance for internalisation. The improvement of mucoadhesion and of nanoparticle internalisation with respect to chitosan nanosystems makes the TMCs nanosystems suitable carriers for the intestinal absorption of peptides.  相似文献   
118.
Transbuccal drug delivery has got several well-known advantages especially with respect to peroral way. Since a major limitation in buccal drug delivery could be the low permeability of the epithelium, the aptitude of NLX to penetrate the mucosal barrier was assessed. Ex vivo permeation across porcine buccal mucosa 800 microm thick was investigated using Franz type diffusion cells and compared with in vitro data previously obtained by reconstituted human oral epithelium 100 microm thick. Both fluxes (Js) and permeability coefficients (K(p)) are in accordance, using either buffer solution simulating saliva or natural human saliva. Permeation was evaluated also in presence of chemical enhancers or iontophoresis. No significant differences in penetration rate were observed using chemical enhancers; in contrast, Js and K(p) were extensively affected by application of electric fields. Tablets, designed for Naltrexone hydrochloride (NLX) administration on buccal mucosa, were developed and prepared by direct compression of drug loaded (56%) poly-octylcyanocrylate (poly-OCA) matrices. NLX is slowly discharged from buccal tablets following Higuchian kinetic. Histologically, no signs of flogosis ascribable to NLX and/or poly-OCA were observed, while cytoarchitectural changes due to iontophoresis were detected. Buccal tablets containing NLX may represent a potential alternative dosage form in addiction management.  相似文献   
119.
Pharmacists play an important role in providing information about natural products and in preventing risks related to these substances, particularly with respect to interactions with conventional drugs. For these reasons, a survey was specifically designed to investigate the quality of self-care counselling by pharmacists on phytotherapy. Twenty-three pharmacy stores took part in the project. Face-to-face interviews, using a pre-structured questionnaire, were undertaken by trained pharmacists to consumers buying a herbal product. The questionnaire included socio-demographic data and 17 items designed to elicit information regarding the reason of consumption, product knowledge, relationship/communication with healthcare providers, level of satisfaction, concurrent drug use and adverse reactions. The collection of interviews started in November 2006 until April 2007. From the analysis of 1420 questionnaires, it is evident that herbal use is increasing in Italy: 12% of our interviewees were buying a herbal product for the first time. The present survey highlights the favourable perception of efficacy of phytotherapic compounds by the pharmacy's consumers, who consider this healthcare modality to be an important and effective way to promote health/wellness and disease management as well as being safer overall than conventional drugs. Moreover, findings from this study demonstrate that pharmacists are more likely to answer correctly about the uses of herbal medicines than about drug interactions, adverse drug effects and cautions about these products.  相似文献   
120.
BACKGROUND AND OBJECTIVE: Anthracyclines are highly effective and widely used cytotoxic agents, but their application is often limited by cumulative dose-dependent cardiotoxicity. Dexrazoxane has been shown in several clinical trials to prevent the development of this serious toxicity. The aim of our study was to analyze the incidence of cardiac dysfunction over a 10-year period in patients with breast cancer who were treated with anthracycline-based regimens with addition of dexrazoxane, mainly in an adjuvant setting. METHODS: We conducted a retrospective analysis on a population of women with breast cancer treated at our institution between January 1993 and October 2003. We reviewed patients' medical records and data on patient characteristics, treatment history, and adverse events that were collected, starting from the time of first visit before starting therapy, with the use of software created and designed for clinical records management in our institution (1999 OK-DHtrade mark). Patients underwent an ECG assessment prior to starting chemotherapy, and were clinically monitored for cardiac failure. Those who developed signs and symptoms suggestive of cardiac dysfunction underwent further ECG. If clinical findings indicated, echocardiography and further cardiologic investigations were performed. The main outcome measure was the development of signs and symptoms indicative of congestive heart failure (CHF). RESULTS: A total of 318 female patients were treated with an anthracycline (doxorubicin or epirubicin)-based combination chemotherapy regimen during this time, in most cases in the adjuvant setting (n = 285). Most patients (n = 302) had early-stage disease and only 16 women presented with metastatic disease with good life expectancy (at least 1 year). All patients received dexrazoxane 1000 mg/m(2) intravenously prior to anthracycline administration during each chemotherapy cycle. The median follow-up duration was 35 months. During this time, five patients (1.57%) developed signs and symptoms of CHF. No patient at our institution died of heart failure during the period analyzed. Dexrazoxane was well tolerated, with no reports of adverse events associated with this drug. CONCLUSIONS: The reported incidence of cardiotoxicity in this study represents a marked reduction compared with historical data for patients receiving anthracycline-based chemotherapy without dexrazoxane. Dexrazoxane appears to have a cardioprotective effect in women with early-stage or advanced breast cancer treated with anthracycline-based combination chemotherapy, mainly as an adjuvant treatment. Prospective, randomized, controlled clinical trials in adjuvant setting should be performed to confirm these results.  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