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   1839篇
  免费   121篇
  国内免费   12篇
耳鼻咽喉   10篇
儿科学   24篇
妇产科学   31篇
基础医学   223篇
口腔科学   119篇
临床医学   183篇
内科学   463篇
皮肤病学   19篇
神经病学   192篇
特种医学   93篇
外科学   274篇
综合类   3篇
一般理论   1篇
预防医学   103篇
眼科学   19篇
药学   114篇
中国医学   3篇
肿瘤学   98篇
  2024年   4篇
  2023年   25篇
  2022年   59篇
  2021年   102篇
  2020年   74篇
  2019年   56篇
  2018年   61篇
  2017年   52篇
  2016年   65篇
  2015年   69篇
  2014年   81篇
  2013年   97篇
  2012年   175篇
  2011年   159篇
  2010年   90篇
  2009年   74篇
  2008年   107篇
  2007年   108篇
  2006年   107篇
  2005年   85篇
  2004年   91篇
  2003年   62篇
  2002年   43篇
  2001年   9篇
  2000年   2篇
  1999年   10篇
  1998年   5篇
  1997年   10篇
  1996年   6篇
  1995年   8篇
  1994年   3篇
  1993年   5篇
  1992年   3篇
  1991年   6篇
  1990年   4篇
  1989年   4篇
  1988年   7篇
  1987年   4篇
  1986年   7篇
  1984年   2篇
  1983年   6篇
  1982年   2篇
  1980年   2篇
  1979年   6篇
  1977年   2篇
  1974年   3篇
  1972年   2篇
  1965年   1篇
  1961年   1篇
  1960年   1篇
排序方式: 共有1972条查询结果,搜索用时 15 毫秒
11.
Taking a patient-oriented approach to developing lifestyle interventions includes incorporating the patient into the program’s design, delivery, and evaluation. This commentary assumes that a patient-oriented approach has not yet been implemented and tested in exercise-based interventions designed for pregnant women. We outline and define a patient-oriented approach to conduct exercise-based research and review previous physical activity interventions designed for pregnant women to determine whether a patient-oriented approach was applied. In addition, pregnant women living with obesity may have unique barriers to engaging in prenatal exercise interventions that have not been previously addressed, such as having experienced weight stigma before pregnancy in healthcare and fitness settings. We propose suggestions for future trials to effectively take a patient-oriented approach when designing and implementing prenatal exercise interventions to address patient-informed barriers and incorporate suggested facilitators for physical activity. Given that prenatal activity levels are low and pregnant women may have unique barriers to engaging in exercise interventions, a patient-oriented approach may be an effective strategy to improve inclusivity and equity and, as a result, increase uptake and adherence to the intervention.  相似文献   
12.
Bombyx mori silk fibroin (SF) is a very versatile biopolymer due to its biocompatibility and exceptional mechanical properties which make possible its use as a functional material in several applications. SF can be modified with a large variety of chemical approaches which endow the material with tailored chemical–physical properties. Here, a systematic investigation of different routes is reported to graft long alkyl chains on SF based on both liquid- and solid-phase, aiming to modulate its hydrophobic behavior. The liquid phase method involves direct activation of SF tyrosine residues via diazo coupling and cycloaddition reactions, generating hydrophobic materials insoluble in any common solvent. The solid phase approach consists of the chemical modification of drop-casted SF films by esterification of hydroxyl groups of serine, threonine, and tyrosine SF residues with acyl chlorides of fatty acids. For the solid-state functionalization, a new class of hydrophobic pendant groups is synthesized, based on triple esters of gallic acid anhydrides, that are reacted with the biopolymer to further enhance its resulting hydrophobic features.  相似文献   
13.
PURPOSE: Melanoma is a highly malignant and increasingly common tumor. Because the cure rate of metastatic melanoma by conventional treatment is very low, new therapeutic approaches are needed. We previously reported that coated cationic liposomes (CCL) targeted with a monoclonal antibody against the disialoganglioside (GD(2)) and containing c-myb antisense oligodeoxynucleotides (asODNs) resulted in a selective inhibition of the proliferation of GD(2)-positive neuroblastoma cells in vitro. EXPERIMENTAL DESIGN: Here, we tested the in vivo antitumor effects of this novel antisense liposomal formulation by targeting the c-myc oncogene on melanoma, a neuroectodermal tumor sharing with neuroblastoma the expression of GD(2). RESULTS: Our methods produced GD(2)-targeted liposomes that stably entrapped 90% of added c-myc asODNs. These liposomes showed a selective binding for GD(2)-positive melanoma cells in vitro. Melanoma cell proliferation was inhibited to a greater extent by GD(2)-targeted liposomes containing c-myc asODNs (aGD(2)-CCL-myc-as) than by nontargeted liposomes or free asODNs. The pharmacokinetic results obtained after i.v. injection of [(3)H]-myc-asODNs, free or encapsulated in nontargeted CCLs or GD(2)-targeted CCLs, showed that free c-myc-asODNs were rapidly cleared, with less than 10% of the injected dose remaining in blood at 30 min after injection. c-myc-asODNs encapsulated within either CCL or aGD(2)-CCL demonstrated a more favorable profile in blood, with about 20% of the injected dose of each preparation remaining in vivo at 24 h after injection. In an in vivo melanoma experimental metastatic model, aGD(2)-CCL-myc-as, at a total dose of only 10 mg of asODN per kilogram, significantly inhibited the development of microscopic metastases in the lung compared with animals treated with myc-asODNs, free or entrapped in nontargeted liposomes, or aGD(2)-CCL encapsulating scrambled asODNs (P < 0.01). Moreover, mice bearing established s.c. human melanoma xenografts treated with aGD(2)-CCL-myc-as exhibited significantly reduced tumor growth and increased survival (P < 0.01 versus control mice). The mechanism for the antitumor effects appears to be down-regulation of the expression of the c-myc protein and interruption of c-myc-mediated signaling: induction of p53 and inhibition of Bcl-2 proteins, leading to extensive tumor cell apoptosis. CONCLUSION: These results suggest that inhibition of c-myc proto-oncogene by GD(2)-targeted antisense therapy could provide an effective approach for the treatment of melanoma in an adjuvant setting.  相似文献   
14.
15.
There is a growing quest for an ideal biomaterial that shows appropriate cellular response and is not susceptible to microbial adhesion. In this study, commercial grade II titanium was submitted to RF/DC plasma surface modification at 2.2 mbar, using gas mixtures of argon, nitrogen, and oxygen at proportions 4:1:2 and 4:1:3. The surfaces were physically and chemically characterized. In order to evaluate bacterial response, the surfaces were exposed to Staphylococcus epidermidis. Oxynitrided samples, although having a higher roughness as compared with untreated samples, exhibited lower bacterial growth. This observation is probably due to the formation of different crystalline phases of nitrides and oxides caused by plasma treatment. The surface with highest contact angle and highest surface tension showed lower bacterial adhesion. These results were confirmed by scanning electron microscopy. The role of nitrogen in reducing bacterial adhesion is clear when this material is compared with untreated titanium, on which only an oxide film is present.  相似文献   
16.
17.
Oxidative stress and inflammation are highly intertwined pathophysiological processes. We analyzed the markers of these processes and high-sensitive troponin I (hsTnI) for mortality prediction in patients on haemodialysis. This study enrolled a total of 62 patients on regular haemodialysis. The patients were monitored for two years, and the observed outcomes were all-cause and cardiovascular mortality. Blood samples were taken before one dialysis session for analysis of the baseline concentrations of prooxidant–antioxidant balance (PAB), total antioxidant status (TAS), total oxidative status (TOS), hsTnI, hsCRP and resistin. The overall all-cause mortality was 37.1% and CVD mortality 16.1%. By univariate and multivariate logistic regression, our findings suggest that good predictors of all-cause mortality include hsCRP and PAB (p?p?p?p?p?=?.001). Our data suggest that hsCRP and PAB are very good predictors of all-cause mortality. For CVD complications and mortality prediction in HD patients, the most sensitive parameters appear to be hsTnI and hsCRP.  相似文献   
18.
The aim of this research was to investigate the effect of new, non-conventional starter culture on the kinetics of the lactose transformation during milk fermentation by kombucha, at pH 5.8; 5.4; 5.1; 4.8; and 4.6, at two different temperatures 37 °C and 42 °C. Milk fermentation at 42 °C lasted significantly shorter (about 5 h, 30 min) compared to the fermentation at 37 °C. Changes of lactose concentration at the both temperatures are consisting of two retaining stages and very steep decline in–between. The analysis of the rate curves showed that the reaction rate passes through the maximum after 9 h, 30 min at 37 °C and after 4 h at 42 °C. The sigmoidal saturation curve indicates a complex kinetics of lactose fermentation by kombucha starter.  相似文献   
19.
20.
Pre-implantation genetic diagnosis for aneuploidy testing (PGD-A) is a tool to identify euploid embryos during IVF. The suggested populations of patients that can benefit from it are infertile women of advanced maternal age, with a history of recurrent miscarriages and/or IVF failures. However, a general consensus has not yet been reached.After the clinical failure of its first version based on cleavage stage biopsy and 9 chromosome-FISH analysis, PGD-A is currently performed by 24 chromosome screening techniques on trophectoderm (TE) biopsies. This approach has been clearly demonstrated to involve a higher clinical efficiency with respect to the standard care, in terms of sustained pregnancy rate per transfer and lower miscarriage rate. However, data about PGD-A efficacy calculated on a per intention-to-treat basis, as well as an analysis of its cost-effectiveness, are still missing.TE biopsy is a safe and extensively validated approach with low biological and technical margin of error. Firstly, the prevalence of mosaic diploid/aneuploid blastocysts is estimated to be between 0 and 16 %, thus largely tolerable. Secondly, all the comprehensive chromosome screening (CCS) technologies adapted to, or designed to conduct PGD-A are highly concordant, and qPCR in particular has been proven to show the lowest false positive error rate (0.5 %) and a clinically recognizable error rate per blastocyst of just 0.21 %.In conclusion, there is a sufficient body of evidence to support the clinical application of CCS-based PGD-A on TE biopsies. The main limiting factor is the need for a high-standard laboratory to conduct blastocyst culture, biopsy and vitrification without impacting embryo viability.  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