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   6833篇
  免费   483篇
  国内免费   68篇
耳鼻咽喉   46篇
儿科学   170篇
妇产科学   204篇
基础医学   951篇
口腔科学   98篇
临床医学   586篇
内科学   1748篇
皮肤病学   177篇
神经病学   855篇
特种医学   257篇
外科学   564篇
综合类   11篇
预防医学   448篇
眼科学   52篇
药学   486篇
中国医学   15篇
肿瘤学   716篇
  2024年   15篇
  2023年   121篇
  2022年   253篇
  2021年   362篇
  2020年   233篇
  2019年   294篇
  2018年   300篇
  2017年   244篇
  2016年   289篇
  2015年   328篇
  2014年   383篇
  2013年   469篇
  2012年   699篇
  2011年   684篇
  2010年   365篇
  2009年   280篇
  2008年   396篇
  2007年   362篇
  2006年   340篇
  2005年   275篇
  2004年   219篇
  2003年   186篇
  2002年   136篇
  2001年   13篇
  2000年   10篇
  1999年   13篇
  1998年   25篇
  1997年   11篇
  1996年   10篇
  1995年   9篇
  1994年   3篇
  1993年   7篇
  1992年   7篇
  1991年   2篇
  1990年   2篇
  1989年   7篇
  1988年   2篇
  1987年   4篇
  1986年   2篇
  1984年   4篇
  1979年   2篇
  1978年   2篇
  1976年   2篇
  1971年   1篇
  1969年   2篇
  1965年   1篇
  1947年   1篇
  1943年   1篇
  1942年   1篇
  1941年   1篇
排序方式: 共有7384条查询结果,搜索用时 15 毫秒
31.
Simple SummaryGlioblastoma is an aggressive brain tumor with a dismal prognosis. In a minority of cases, it presents with multiple lesions already at the time of diagnosis, affecting patients’ survival and treatment. Our retrospective study aims to increase the current understanding and define a treatment for this sub-entity, to improve patient survival. Chemoradiotherapy is a also safe and efficacy treatment in patients with multiple lesions. Survival advantages from extensive resection remain unclear.AbstractGlioblastomas with multiple foci at presentation (mGBMs) account for 2–35% of all GBMs. mGBMs have limited existing data and no standardized treatment. This study aims to determine their incidence, demographic and clinical features, outcome, and prognostic factors in terms of overall survival. We performed a monocentric retrospective study, reviewing patients treated at the Istituto Oncologico Veneto. Inclusion criteria were: new diagnosis of GBM and presence of multiple lesions on pre-treatment MRI. ECOG PS was used to evaluate clinical condition, RANO criteria for radiological assessment, and CTCAE v5.0 for treatment-related adverse events. The incidence of newly diagnosed mGBM was 7.2% and the study population consisted of 98 patients. Median age was 63 years, M:F ratio of 1.8:1, and a surgical approach was undertaken in 73 patients (mostly partial resection). MGMT was methylated in 47.5%, and 82 patients received active oncological treatment (65.9% radiotherapy plus temozolomide (RT + TMZ)). The disease control rate with RT + TMZ was 63%. Median OS of the entire study population was 10.2 months (95% CI 6.6–13.8), and median PFS was 4.2 months (95% CI 3.2–5.2). The ECOG PS, the extent of resection, and the RT + TMZ were significant prognostic factors in the univariate analysis for OS, but only the RT + TMZ was a significant independent OS predictor in the multivariate analysis (HR = 3.1, 95% IC 1.3–7.7, p = 0.014). The incidence of mGBM is not rare. RT + TMZ is confirmed to be an independent prognostic factor for survival and a safe and effective treatment. When feasible, RT + TMZ should be considered as a possible first-line treatment. The role of the extent of resection is still unclear.  相似文献   
32.
33.
The European Food Safety Authority is currently evaluating the risks related to the presence of emerging mycotoxins in food and feeds. The aim of this study was to investigate the role of soil fertility, resulting from different nitrogen fertilization rates, on the contamination of regulated mycotoxins and emerging fungal metabolites in maize grains. The trial was carried out in the 2012–2013 growing seasons as part of a long-term (20-year) experimental platform area in North-West Italy, where five different N rates, ranging from 0 to 400 kg N ha−1, were applied to maize each year. Maize samples were analyzed by means of a dilute-and-shoot multi-mycotoxin LC-MS/MS method, and more than 25 of the most abundant mycotoxins and fungal metabolites were detected. Contamination by fumonisins and other fungal metabolites produced by Fusarium spp. of the section Liseola was observed to have increased in soils that showed a poor fertility status. On the other hand, an overload of nitrogen fertilization was generally associated with higher deoxynivalenol and zearalenone contamination in maize kernels, as well as a higher risk of other fungal metabolites produced by Fusarium spp. sections Discolor and Roseum. A balanced application of N fertilizer, in accordance with maize uptake, generally appears to be the best solution to guarantee an overall lower contamination by regulated mycotoxins and emerging fungal metabolites.  相似文献   
34.
La Crosse virus (LACV) is a major cause of pediatric encephalitis and aseptic meningitis in the Midwestern, Mid-Atlantic, and Southern United States, where it is an emerging pathogen. The LACV Gc glycoprotein plays a critical role in the neuropathogenesis of LACV encephalitis as the putative virus attachment protein. Previously, we identified and experimentally confirmed the location of the LACV fusion peptide within Gc and generated a panel of recombinant LACVs (rLACVs) containing mutations in the fusion peptide as well as the wild-type sequence. These rLACVs retained their ability to cause neuronal death in a primary embryonic rat neuronal culture system, despite decreased replication and fusion phenotypes. To test the role of the fusion peptide in vivo, we tested rLACVs in an age-dependent murine model of LACV encephalitis. When inoculated directly into the CNS of young adult mice (P28), the rLACV fusion peptide mutants were as neurovirulent as the rLACV engineered with a wild-type sequence, confirming the results obtained in tissue culture. In contrast, the fusion peptide mutant rLACVs were less neuroinvasive when suckling (P3) or weanling (P21) mice were inoculated peripherally, demonstrating that the LACV fusion peptide is a determinant of neuroinvasion, but not of neurovirulence. In a challenge experiment, we found that peripheral challenge of weanling (P21) mice with fusion peptide mutant rLACVs protected from a subsequent WT-LACV challenge, suggesting that mutations in the fusion peptide are an attractive target for generating live-attenuated virus vaccines. Importantly, the high degree of conservation of the fusion peptide amongst the Bunyavirales and, structurally, other arboviruses suggests that these findings are broadly applicable to viruses that use a class II fusion mechanism and cause neurologic disease.  相似文献   
35.
In the last 20 years, gut microbiota in patients with cystic fibrosis (CF) has become an object of interest. It was shown that these patients had gut dysbiosis and this could explain not only the intestinal manifestations of the disease but also part of those involving the respiratory tract. The acquisition of previously unknown information about the importance of some bacteria, i.e., those partially or totally disappeared in the gut of CF patients, in the regulation of the activity and function of the gut and the lung was the base to suggest the use of probiotics in CF patients. The main aim of this paper is to discuss the biological basis for probiotic administration to CF patients and which results could be expected. Literature analysis showed that CF intestinal dysbiosis depends on the same genetic mutations that condition the clinical picture of the diseases and is aggravated by a series of therapeutic interventions, such as dietary modifications, the use of antibiotics, and the administration of antacids. All this translates into a significant worsening of the structure and function of organs, including the lung and intestine, already deeply penalized by the genetic alterations of CF. Probiotics can intervene on dysbiosis, reducing the negative effects derived from it. However, the available data cannot be considered sufficient to indicate that these bacteria are essential elements of CF therapy. Further studies that take into account the still unsolved aspects on how to use probiotics are absolutely necessary.  相似文献   
36.
37.

Objective

The objective of this multicentre, non-controlled, open-label study is the evaluation of the bleeding patterns during the use of a vaginal combined contraceptive, its safety in relation to occurrence of adverse effects, its efficacy as a contraceptive method and user compliance.

Study design

Healthy female volunteers (N = 165), asking for contraception, were enrolled to participate in the study. Each subject was given seven vaginal rings, releasing an average amount of 120 μg etonogestrel (ENG) and 15 μg ethinylestradiol (EE) per day. Study period was 7 cycles. A total of 878 cycles was valid for statistical analysis. The primary parameter, (breakthrough bleeding and/or spotting), was recorded for each cycle. The subjects were asked to report any adverse effect experienced during the treatment period, general physical and gynaecological examinations were performed and haematological blood tests were taken.

Results

Breakthrough bleeding/spotting occurred in 5.01% cycles (44 out of 878 cycles, of whom 37 were breakthrough spotting only). Absence of withdrawal bleeding during the ring-free period was reported in 1.94% cycles (17 out of 878). Forty-one subjects (24.8%) reported 66 events that were potentially drug-related. The most frequently drug-related events were weight increase (10 cases), headache (9 cases), nausea (4 cases). No pregnancy was reported during the study period. Haematology and chemical chemistry tests showed no clinically significant abnormality.

Conclusions

In the present study, NuvaRing® has shown to be a valid contraceptive method to ensure optimal cycle control with low incidence of irregular bleeding and altered withdrawal bleeding. The low incidence of gastrointestinal side effects (nausea, vomiting) may be related the low hormonal dose and to the vaginal delivery of hormones which avoids the gastrointestinal tract.  相似文献   
38.
Fertility preservation in young girls affected by malignancies has got growing relevance in the last decade due to the improved survival chance of these patients after oncostatic treatments. Most studies have focused on preserving ovarian follicles and avoiding premature ovarian failure, whereas only a few have evaluated the effects exerted by radiotherapy and chemotherapy on the uterus. It is self-evident that fertility preservation after oncostatic therapies must include the maintenance of a functional uterus, and a certain degree of uterine damage must be considered when estimating reproductive prognosis in previously treated, childhood cancer survivors. TARGET AUDIENCE: Obstetricians & Gynecologists, Family Physicians. LEARNING OBJECTIVES: After completion of this article, the reader should be able to recall the growing number of children who survive oncostatic treatments, explain the possible effects on future reproductive endeavors, and summarize the possible ways to preserve fertility.  相似文献   
39.
This article focuses on agar biopolymer films that offer promise for developing biodegradable packaging, an important solution for reducing plastics pollution. At present there is a lack of data on the mechanical performance of agar biopolymer films using a simple plasticizer. This study takes a Design of Experiments approach to analyze how agar-glycerin biopolymer films perform across a range of ingredients concentrations in terms of their strength, elasticity, and ductility. Our results demonstrate that by systematically varying the quantity of agar and glycerin, tensile properties can be achieved that are comparable to agar-based materials with more complex formulations. Not only does our study significantly broaden the amount of data available on the range of mechanical performance that can be achieved with simple agar biopolymer films, but the data can also be used to guide further optimization efforts that start with a basic formulation that performs well on certain property dimensions. We also find that select formulations have similar tensile properties to thermoplastic starch (TPS), acrylonitrile butadiene styrene (ABS), and polypropylene (PP), indicating potential suitability for select packaging applications. We use our experimental dataset to train a neural network regression model that predicts the Young’s modulus, ultimate tensile strength, and elongation at break of agar biopolymer films given their composition. Our findings support the development of further data-driven design and fabrication workflows.  相似文献   
40.
BackgroundPeptide receptor radionuclide therapy (PRRT) with radiolabeled somatostatin receptor (SSR) analogs is now an established systemic treatment for neuroendocrine tumors (NET). However, more short- and long-term data about renal and hepatotoxicity is needed. Here we present our experience in this clinical scenario.MethodsEighty-six patients with progressive SSR-expressing malignancies underwent PRRT with Lu-177 Dotatate and were followed up for up to 2 years. Laboratory tests were done 1 week before each cycle and every 2 months at follow-up. Hepatic and renal toxicity was determined based on NCI CTCAE V5.0.Results55/86 (64%) patients completed all 4 cycles of PRRT; 18/86 (20.9%) are currently being treated; 13/86 (15.1%) had to discontinue PRRT: 4/13 (31%) due to hematologic toxicity, 9/13 (69%) due to non-PRRT-related comorbidities. Out of the patients who finished treatment, only transient grade 2 toxicities were observed during PRRT: hypoalbuminemia in 5.5% (3/55), and renal toxicity (serum creatinine and estimated glomerular filtration rate) in 1.8% (1/55). No grade 3 or 4 liver and renal toxicity occurred. Patients presenting with impaired liver or renal function prior to PRRT, either improved or had stable findings. No deterioration was observed.ConclusionPeptide receptor radionuclide therapy does not have a negative impact on liver and renal function, even in patients with pre-existing impaired parameters. No grade 3 or 4 hepatic or renal toxicity was identified. Only transient grade 2 hypoalbuminemia in 5.5% and nephrotoxicity in 1.8% of patients were seen during PRRT.  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