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   5096篇
  免费   361篇
  国内免费   30篇
耳鼻咽喉   38篇
儿科学   163篇
妇产科学   180篇
基础医学   594篇
口腔科学   239篇
临床医学   527篇
内科学   917篇
皮肤病学   225篇
神经病学   345篇
特种医学   500篇
外科学   448篇
综合类   77篇
一般理论   7篇
预防医学   382篇
眼科学   92篇
药学   345篇
中国医学   49篇
肿瘤学   359篇
  2024年   9篇
  2023年   106篇
  2022年   204篇
  2021年   329篇
  2020年   220篇
  2019年   332篇
  2018年   351篇
  2017年   224篇
  2016年   224篇
  2015年   234篇
  2014年   299篇
  2013年   320篇
  2012年   452篇
  2011年   424篇
  2010年   191篇
  2009年   154篇
  2008年   224篇
  2007年   217篇
  2006年   166篇
  2005年   129篇
  2004年   124篇
  2003年   92篇
  2002年   98篇
  2001年   49篇
  2000年   33篇
  1999年   30篇
  1998年   7篇
  1997年   8篇
  1996年   6篇
  1995年   4篇
  1993年   9篇
  1992年   16篇
  1991年   27篇
  1990年   14篇
  1989年   22篇
  1988年   12篇
  1987年   22篇
  1986年   11篇
  1985年   20篇
  1984年   9篇
  1983年   8篇
  1982年   6篇
  1981年   4篇
  1980年   4篇
  1978年   3篇
  1977年   6篇
  1976年   6篇
  1971年   5篇
  1970年   5篇
  1969年   4篇
排序方式: 共有5487条查询结果,搜索用时 15 毫秒
21.
22.
Graphene is a 2D material with remarkable properties. The present study demonstrates the fabrication of a graphene-based sensor for measuring the temperature and humidity of a metal body. The graphene sensor was fabricated by depositing a thin film of graphene nanoparticles between silver electrodes (separated by ∼50 μm) on a glass substrate. The graphene thin film was characterized by XRD, Raman spectroscopy and UV-vis techniques. The capacitance and resistance for both the relative humidity (in the range of 0–100% RH) and temperature (in the range of 230–310 K) were measured using an LCR meter at 1 kHz in a controlled chamber. The graphene-based sensor expressed high sensitivity with fast response and recovery times for both humidity and temperature with long stability and low hysteresis curves. The sensor was also tested on a metal body, which expressed a good response time. Moreover, the measured data of capacitance and resistance was analyzed with classical and neutrosophic analysis as an application of modern material statistics. It was observed that neutrosophic analysis is more flexible for analyzing the capacitance and resistance of the fabricated sensor.

Graphene is a 2D material with remarkable properties.  相似文献   
23.
This study assesses the retreatability of TotalFill bioceramic (TFBC) and AH Plus (AHP) sealers and their impact on retreatment force and torque. Twenty-six premolar teeth with single oval canals were instrumented, obturated using the matched gutta-percha cone technique with one of the tested sealers, and then temporized. After a 6-month incubation at 37 °C and 100% humidity, the canals were retreated with the XP Shaper system. During retreatment, the generated force and torque were measured. Micro-CT scanning was run before and after the retreatment procedure to analyze the remaining obturating materials in the canals. The apically directed maximum force in AHP was higher than that in TFBC. The coronally directed maximum force and the maximum torque were comparable between the groups. A higher amount of remaining obturating materials was found in the AHP compared to that in the TFBC. Based on these findings, endodontic sealer had an influence on retreatability, and the TFBC showed less remaining obturating materials and lower retreatment forces in the apical direction compared to the AHP in extracted teeth with oval canals.  相似文献   
24.
Background Sentinel lymph node (SLN) mapping with radioisotope and blue dye is rapidly becoming the standard of care for breast cancer. The optimal location for injection of radioisotope and blue dye is still being investigated. The goal of this study was to determine whether blue dye injection into the subareolar (SA) location localized the same sentinel nodes as the peritumoral (PT) location for patients with breast cancer. Methods Three hundred thirty-two patients with biopsy-proven operable breast cancer or ductal carcinoma in situ at two institutions underwent SLN mapping. Eighty-three patients had PT injection of blue dye (group 1), and 249 patients had SA injection of blue dye (group 2). All patients underwent PT injection of99mTc-labeled sulfur colloid. Results The two groups were similar in age, previous biopsy type, and tumor size, location, and histology. The mean number of SLNs identified was 2.4 (range, 0–9) in group 1 and 2.5 (range, 0–11) in group 2. The SLN identification rate was 95% for group 1 and 97% for group 2. The isotope success rate was 94% for both groups. The blue dye success rate was 84% for group 1 and 90% for group 2. The isotope/blue dye concordance rate was 87% for group 1 and 90% for group 2. At a median follow-up of 28 months (range, 14 to 40), there were no axillary recurrences in any of the 332 patients. Conclusions These data suggest that delivery of mapping reagents in the SA and PT locations identifies similar lymph nodes. Because of simplicity and the similarity in node identification between SA and PT injection, further investigation of the SA site for delivery of SLN mapping reagents for breast cancer is warranted. Presented at the 54th Annual Cancer Symposium, Society of Surgical Oncology. Washington, DC, March 15–18, 2001.  相似文献   
25.
26.
27.
This study aimed to investigate dietary supplement use among Iranian adults in northern Iran. A cross-sectional study was undertaken on randomly selected men and women in Guilan province, northern Iran. The study population was parents of children and adolescents studying in schools. Totally, 1,425 women and 676 men were studied and data on age, body weight, height, educational level, and supplement use was gathered using a self-administrated questionnaire. These data showed that supplement use was related to sex, body mass index, and educational levels in both sexes. Most common supplements used in this population were Iron, calcium, multivitamin/multiminerals and fish oils. These results showed that 13.3, 3.4, 2.2, and 1.1 % of the study men used iron, calcium, multivitamin/multimineral, and fish oil, respectively. In women, 27.1, 10.7, 5.1, and 5.5 % used Iron, calcium, multivitamin/multimineral, and fish oil, respectively. More educated men and women and those with more healthy weight were more likely to use any dietary supplement than the less educated and overweight/obese men and women. This study showed that iron was the most common dietary supplement in this study middle aged Iranians. Using the other supplements was mostly related to age, educational level, and body weight status in this population. These data indicated that dietary supplement use was inversely related to some health-related behaviors and socioeconomic factors.  相似文献   
28.
Heat stroke is a lifethreatening disease with high mortality, characterized by a body temperature of over 40°C and clinical symptoms of central nervous system dysfunction. However, the pathophysiological mechanisms are not fully understood. A new interesting explanation for the clinical symptoms could be a systemic inflammatory response due to barrier dysfunction in the intestine leading to endothelial damage and a syndrome of multiorgan dysfunction. We describe a 37-year-old male patient who collapsed while working in a vineyard in an environmental temperature of 32°C with a body temperature of 42.5°C. Despite intensive care treatment, he died with symptoms of shock and multiorgan dysfunction. Autopsy was performed followed by the histological evaluation of paraffin-embedded tissue. As correlates for clinical shock symptoms, shock kidneys and shock liver could be demonstrated. Furthermore, multiple microthrombi were found, together with clinically undetectable fibrinogen values. Finally, the patient died due to massive diffuse gastrointestinal bleeding and bleeding in pleural and pericardial cavities. No signs of severe edema of the central nervous system were detectable. This case supports the hypothesis that in heat stroke endothelial damage occurs with consecutive cascade of inflammatory and coagulatory reactions, which may play a critical pathophysiological role.  相似文献   
29.

Background

Diabetes mellitus is characterized jointly by hyperglycemia and hyperinsulinemia that make insulin more prone to be glycated and evolve insulin advanced glycation end products (Insulin- AGE). Here, we report the effect of beta-hydroxy butyrate (BHB) (the predominant ketone body) on the formation of insulin-AGE, insulin glycation derived liposomal lipid peroxidation and insulin-AGE toxicity in microglial cells.

Methods

The inhibitory effect of BHB was monitored as a result of insulin incubation in the presence of glucose or fructose using AGE-dependent fluorescence, Tyr fluorescence as well as anilinonaphthalenesulfonate (ANS) andthioflavin T (ThT) binding, and circular dichroism (CD) investigations. To study lipid peroxidation induced by insulin glycation, thiobarbituric acid (TBA) assay and thiobarbituric acid reactive substance (TBARS) monitoring were used. The effect of insulin–AGE on microglial viability was investigated by 3-(4, 5 dimethylthiazol-2-yl)—2, 5-diphenyltetrazoliumbromide (MTT) cell assay and Annexin V/propidium iodide (PI) staining.

Results

Here we are reporting the inhibitory effect of BHB on insulin glycation and generation of insulin-AGE as a possible explanation for insulin resistance. Moreover, the protective effect of BHB on consequential glycation derived liposomal lipid peroxidation as a causative event in microglial apoptosis is reported.

Conclusion

The reduced insulin fibril formation, structural inertia to glycation involved conformational changes, anti-lipid peroxidation effect, and increasing microglia viability indicated the protective effect of BHB that disclose insight on the possible preventive effect of BHB on Alzheimer’s disease.  相似文献   
30.
Renal cell carcinoma (RCC) is the most common renal malignancy in adults and exhibits highly intrinsic and acquired resistance to standard therapeutic strategies. We sought to determine the anti-cancer activity of hydroalcoholic extract of Nigella sativa seeds (NSE) and thymoquinone (TQ). Human renal cell carcinoma (ACHN) and fibroblast L929 cell lines were treated with NSE and TQ, and cytotoxicity was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium (MTT) assay. Cell death pattern was determined by annexin V and propidium iodine (PI)-staining methods. Exposure to NSE, TQ and cisplatin significantly inhibited the growth of ACHN cells and showed significant increase of early apoptotic cells. Normal cells were more resistant to NSE and TQ-induced effects. The present study demonstrates that N. sativa and TQ exert anti-proliferative and pro-apoptotic effects on ACHN cells in a concentration and time-dependent manner, which suggests their potential to be used as a new therapeutic strategy for renal cancers.  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