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   1168篇
  免费   61篇
  国内免费   7篇
耳鼻咽喉   9篇
儿科学   39篇
妇产科学   5篇
基础医学   175篇
口腔科学   78篇
临床医学   133篇
内科学   226篇
皮肤病学   20篇
神经病学   77篇
特种医学   101篇
外科学   134篇
综合类   25篇
一般理论   1篇
预防医学   56篇
眼科学   23篇
药学   63篇
中国医学   13篇
肿瘤学   58篇
  2024年   1篇
  2023年   15篇
  2022年   31篇
  2021年   77篇
  2020年   46篇
  2019年   60篇
  2018年   58篇
  2017年   46篇
  2016年   60篇
  2015年   50篇
  2014年   68篇
  2013年   88篇
  2012年   115篇
  2011年   109篇
  2010年   69篇
  2009年   36篇
  2008年   64篇
  2007年   73篇
  2006年   56篇
  2005年   33篇
  2004年   25篇
  2003年   16篇
  2002年   7篇
  2001年   2篇
  2000年   3篇
  1999年   2篇
  1998年   2篇
  1997年   2篇
  1996年   2篇
  1995年   4篇
  1994年   2篇
  1992年   1篇
  1991年   1篇
  1990年   1篇
  1989年   3篇
  1988年   1篇
  1987年   1篇
  1986年   1篇
  1984年   1篇
  1983年   1篇
  1979年   1篇
  1976年   1篇
  1971年   1篇
排序方式: 共有1236条查询结果,搜索用时 12 毫秒
991.
Color parameters were used in this study to develop a machine learning model for predicting the mechanical properties of artificially weathered fir, alder, oak, and poplar wood. A CIELAB color measuring system was employed to study the color changes in wood samples. The color parameters were fed into a decision tree model for predicting the MOE and MOR values of the wood samples. The results indicated a reduction in the mechanical properties of the samples, where fir and alder were the most and least degraded wood under weathering conditions, respectively. The mechanical degradation was correlated with the color change, where the most resistant wood to color change exhibited less reduction in the mechanical properties. The predictive machine learning model estimated the MOE and MOR values with a maximum R2 of 0.87 and 0.88, respectively. Thus, variations in the color parameters of wood can be considered informative features linked to the mechanical properties of small-sized and clear wood. Further research could study the effectiveness of the model when analyzing large-sized timber.  相似文献   
992.
The syntheses and investigations of new biologically active derivatives of dihydropyrimidines by Biginelli reaction in the presence of copper triflate are reported. Due to the fact that salicylaldehyde and its derivatives under Biginelli reaction conditions can lead to the formation of 2 types of dihydropyrimidines, the influence of copper triflate on product formation was also investigated. In addition to this, regioselective oxidation of dihydropyrimidines was performed in the presence of cerium ammonium nitrate and novel oxidized dihydropyrimidines were obtained. Single crystals of some of them were obtained and as a result, the structures of them were investigated by X-ray diffraction method, which allows determining the presence of hydrogen bonds in their structures. In addition to this, the presence of hydrogen bonds in their structures affects the formation of the corresponding tautomer during oxidizing of dihydropyrimidines. Since dihydropyrimidines are claimed to be biologically active compounds, activities of the synthesized compounds were studied against Acinetobacter baumanii, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae and Staphylococcus aureus bacteria.

Known methods of synthesis of dihydropyrimidines and their oxidized products were modified, the impact of hydrogen bonds on stabilization of preferred tautomer and biological activities were studied.  相似文献   
993.
International Journal of Mental Health and Addiction - The Young Schema Questionnaire-Short Form (YSQ-SF), as a measure of early maladaptive schemas (EMSs), showed good validity and reliability....  相似文献   
994.
Patients with both heart failure and obstructive sleep apnea often have poor, repeatedly disrupted sleep, and yet they frequently do not complain of excessive daytime sleepiness. Understanding this lack of perceived sleepiness is crucial for the case identification and treatment of obstructive sleep apnea in the heart failure population at high risk of this disease, especially given the association between untreated obstructive sleep apnea and mortality among patients with heart failure. In this review, we present epidemiologic evidence concerning the lack of sleepiness symptoms in heart failure and obstructive sleep apnea, explore possible mechanistic explanations for this relationship, assess the benefits of treatment in this population, discuss implications for clinical practice and explore directions for future research.  相似文献   
995.
Constipation, a disorder of bowel movements, is among the most frequent gastrointestinal complaints in Western countries. Dietary constituents such as inadequate fiber intake have been related to constipation, but discrepancies exist in the findings regarding dietary factors. This study investigated the association between dietary patterns and bowel movements in adults living in Luxembourg. Data from 1431 participants from ORISCAV-LUX 2 (a cross-sectional survey) who completed a 174-item food frequency questionnaire (FFQ) were analyzed. A questionnaire-based constipation score was assessed by a validated scoring system. Confounders such as physical activity and serum/urine indicators were assessed. Women had higher constipation scores than men (p < 0.001). In food group-based regression models, a negative association was found between higher constipation score and intake of grains (Beta = −0.62, 95%CI: −1.18, −0.05) and lipid-rich foods (Beta = −0.84, 95%CI: −1.55, −0.13), while a positive association was found for sugary products (Beta = 0.54, 95%CI: 0.11, 0.97) (p < 0.05). In a nutrient-based regression model, a positive association was found between constipation score and total energy (Beta = 5.24, 95%CI: 0.37, 10.11) as well as sodium intake (Beta = 2.04, 95%CI: 0.21, 3.87), and a negative one was found for total fats (Beta = −4.17, 95%CI: −7.46, −0.89) and starch (Beta = −2.91, 95%CI: −4.47, −1.36) (p < 0.05). Interestingly, neither fruits and vegetables or dietary fiber were significantly associated with constipation. Thus, grains, lipid-rich foods, total fats and starch were associated with a lower constipation score, while sugary products, sodium, and higher energy intake were correlated with higher constipation.  相似文献   
996.
Context: The immune system through T-helper 1 (Th1) and Th17 cells play a critical role in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), whereas the Th2 responses inhibit myelin degeneration. Artemisinin, as an anti-malaria as its agent, has been used widely in the treatment of malaria, shifts the lymphocyte responses from Th1 to Th2.

Objective: In this study, we have investigated the therapeutic effects of artemisinin on the EAE treatment.

Materials and methods: EAE was induced in the inbred C57BL6 mice. High and low doses of prednisolone and artemisinin were injected daily with the control and test groups, respectively. The spleen and the brain of the mice were removed and used for ELISA and histological studies.

Results: The mean weight of mice was significantly (p value?p value p value?p value?Conclusions: Since, artemisinin can shift the immune responses from Th1 to Th2, therefore, it can be helpful in the treatment of MS after more investigation.  相似文献   
997.
Several studies have been performed to develop effective neutralizing monoclonal antibodies. The Epstein–Barr virus (EBV) can efficiently immortalize B-cells to establish lymphoblastoid cell lines (LCL) and so it has been used extensively for transformation of B-cells to produce and secrete immunoglobulin. The present study addressed the effect of TLR7/8 agonist (R848), feeder cells layer and ?uorescence-activated cell sorting (FACS) and magnetic-activated cell sorting (MACS) cell separation methods on the transformation efficiency of antibody-producing memory B-cells. For these studies, the antigen used for analyses of antibody formation was the tetanus neurotoxin (TeNT) derived from Clostridium tetani. The results here showed that employing an HFFF.PI6 feeder cell layer, R848 agonist and FACS-mediated purification of memory B-cells led to increased transformation efficiency. Altogether, the effects of the R848 and the feeder cells provided an efficient method for EBV transformation of human B-cells. Moreover, there was an advantage in using FACS sorting of B-cells over the MACS method in the context of EBV transformation and immortalization of precursors of antigen-specific B-cells.  相似文献   
998.
999.
Parasitology Research - Hydrophilic acylated surface protein B (HASPB) is an immunogenic Leishmania-specific protein that antibodies are produced against it in the sera of Leishmania-infected...  相似文献   
1000.
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