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   1591篇
  免费   123篇
  国内免费   7篇
耳鼻咽喉   16篇
儿科学   67篇
妇产科学   66篇
基础医学   205篇
口腔科学   51篇
临床医学   123篇
内科学   346篇
皮肤病学   47篇
神经病学   112篇
特种医学   69篇
外科学   165篇
综合类   26篇
一般理论   2篇
预防医学   137篇
眼科学   58篇
药学   122篇
中国医学   4篇
肿瘤学   105篇
  2024年   4篇
  2023年   31篇
  2022年   75篇
  2021年   119篇
  2020年   62篇
  2019年   73篇
  2018年   88篇
  2017年   43篇
  2016年   66篇
  2015年   65篇
  2014年   69篇
  2013年   96篇
  2012年   112篇
  2011年   128篇
  2010年   67篇
  2009年   38篇
  2008年   86篇
  2007年   95篇
  2006年   91篇
  2005年   76篇
  2004年   68篇
  2003年   52篇
  2002年   38篇
  2001年   17篇
  2000年   2篇
  1999年   11篇
  1998年   6篇
  1997年   6篇
  1996年   7篇
  1995年   4篇
  1994年   5篇
  1993年   1篇
  1992年   2篇
  1991年   2篇
  1989年   1篇
  1988年   1篇
  1987年   1篇
  1986年   2篇
  1985年   4篇
  1984年   1篇
  1983年   1篇
  1980年   1篇
  1979年   1篇
  1977年   2篇
  1930年   1篇
排序方式: 共有1721条查询结果,搜索用时 46 毫秒
61.
International Journal of Mental Health and Addiction - There is an urgent need to assess the impacts of the Coronavirus-19 disease (COVID-19) outbreak on mental health among the general population...  相似文献   
62.
63.
Recent studies show that Janus Fe3O4‐TiO2 nanoparticles (NPs) have potential applications as a multifunctional agent of magnetic resonance imaging (MRI) and photodynamic therapy (PDT) for the diagnosis and therapy of cancer. However, little work has been done on their biological effects. To evaluate the toxicity and underlying molecular mechanisms of Janus Fe3O4‐TiO2 nanoparticles, an in vitro study using a human liver cell line HL‐7702 cells was conducted. For comparison, the Janus Fe3O4‐TiO2 NPs parent material TiO2 NPs was also evaluated. Results showed that both Fe3O4‐TiO2 NPs and TiO2 NPs decreased cell viability and ATP levels when applied in treatment, but increased malonaldehyde (MDA) and reactive oxygen species (ROS) generation. Mitochondria JC‐1 staining assay showed that mitochondrial membrane permeability injury occurred in both NPs treated cells. Cell viability analysis showed that TiO2 NPs induced slightly higher cytotoxicity than Fe3O4‐TiO2 NPs in HL7702 cells. Western blotting indicated that both TiO2 NPs and Fe3O4‐TiO2 NPs could induce apoptosis, inflammation, and carcinogenesis related signal protein alterations. Comparatively, Fe3O4‐TiO2 NPs induced higher signal protein expressions than TiO2 NPs under a high treatment dose. However, under a low dose (6.25 μg/cm2), neither NPs had any significant toxicity on HL7702 cells. In addition, our results suggest both Fe3O4‐TiO2 NPs and TiO2 NPs could induce oxidative stress and have a potential carcinogenetic effect in vitro. Further studies are needed to elaborate the detailed mechanisms of toxicity induced by a high dose of Fe3O4‐TiO2 NPs.  相似文献   
64.
The aim of this study was to report an unusual case of mucoepidermoid carcinoma (MEC) in a 39-year-old woman. The tumor showed a prominent population of clear and intermediate basal cells. Clear cells rarely predominate over other cell types. Such cases are called clear cell variant of MEC. The case also revealed a variable amount of calcified material in the tumor mass. Calcifications are rare in clear cell MEC. These structures were periodic acid-Schiff positive and diastase resistant, excluding glycogen origin. Immunohistochemistry was performed, and the epidermoid component was positive for cytokeratin (CK)7, CK13, CK14, and CK19. The mucous and clear cells presented mild staining for CK7. Cytokeratins 7, 13, and 19 stained luminal cells, and intermediate cells exhibited positivity for CK7, CK14, and vimentin. The origin of the calcifications is speculated to be the result of dystrophic calcification of the amorphous eosinophilic material secreted by intermediate basal cells.  相似文献   
65.
Introduction: Child-appropriate drug formulations are mandatory for an efficient and safe drug therapy in children. Since the implementation of supportive legislations development of novel drug formulations has significantly been enforced despite the fact that children are a heterogeneous group of patients with varying needs according to age, maturation and disease.

Areas covered: In this review, recent advances and current strategies are evaluated how to overcome the specific hurdles in pediatric drug development. For cardiovascular diseases as an example, EMA’s decisions on pediatric investigation plans (PIPs) have been evaluated. New developments with innovative platform technologies such as mini-tablets and orodispersible preparations have been identified indicating a clear shift from liquid preparations to small-sized solid (multiparticulate) or orodispersible dosage forms. Reasons for this shift of paradigm are discussed.

Expert opinion: Innovative platform technologies for solid drug dosage forms such as mini-tablets, orodispersible tablets or film preparations will continue to conquer the pharmaceutical market. Still, there are some major issues to be resolved, e.g. how to ensure quality of the new dosage forms and dose accuracy in flexible dosing, but the governmental incentives will continue to accelerate development of pediatric medicines and will bridge the still existing gaps in the near future.  相似文献   

66.

Purpose

The aim of the present study was to formulate and optimize lipid blend-based olmesartan medoxomil (OLM) loaded nanoparticulate scaffolds (NLCs) for enhanced oral bioavailability.

Method

The OLM-NLCs were formulated using dependent variables in different concentrations of solid lipid, liquid lipid, surfactant, and co-surfactant by using melt emulsification combined with ultrasonication technique. The formulations were experimentally optimized using a three-factor, three-level statistical design approach. The formulated OLM-NLCs were evaluated for various pharmaceutical quality evaluation parameters and further optimized formulation (OLM-NLCopt) was assessed for release kinetics, thermal behavior, and in vivo absorption assessment.

Result

The optimized formulation (OLM-NLCopt) showed particle size (138.7 nm), PDI (0.18), and entrapment efficiency (83.65%). The comparative in vitro release study revealed OLM-NLCopt showed significantly higher (p?<?0.05) drug release compare to OLM-susp. The in vivo study showed the OLM-NLCopt indicated nearly 3-fold improvement in oral bioavailability vis-a-vis OLM-susp in mice model.

Conclusion

The results of the release study and pharmacokinetic study suggest the potential of OLM-NLCs for improved oral delivery.
  相似文献   
67.
68.
Laser-assisted high speed milling is a subtractive machining method that employs a laser to thermally soften a difficult-to-cut material’s surface in order to enhance machinability at a high material removal rate with improved surface finish and tool life. However, this machining with high speed leads to high friction between workpiece and tool, and can result in high temperatures, impairing the surface quality. Use of conventional cutting fluid may not effectively control the heat generation. Besides, vegetable-based cutting fluids are invariably a major source of food insecurity of edible oils which is traditionally used as a staple food in many countries. Thus, the primary objective of this study is to experimentally investigate the effects of water-soluble sago starch-based cutting fluid on surface roughness and tool’s flank wear using response surface methodology (RSM) while machining of 316 stainless steel. In order to observe the comparison, the experiments with same machining parameters are conducted with conventional cutting fluid. The prepared water-soluble sago starch based cutting fluid showed excellent cooling and lubricating performance. Therefore, in comparison to the machining using conventional cutting fluid, a decrease of 48.23% in surface roughness and 38.41% in flank wear were noted using presented approach. Furthermore, using the extreme learning machine (ELM), the obtained data is modeled to predict surface roughness and flank wear and showed good agreement between observations and predictions.  相似文献   
69.
This review addresses the main contributions of anodic oxide films synthesized and designed to overcome the current limitations of practical applications in energy conversion and storage devices. We present some strategies adopted to improve the efficiency, stability, and overall performance of these sustainable technologies operating via photo, photoelectrochemical, and electrochemical processes. The facile and scalable synthesis with strict control of the properties combined with the low-cost, high surface area, chemical stability, and unidirectional orientation of these nanostructures make the anodized oxides attractive for these applications. Assuming different functionalities, TiO2-NT is the widely explored anodic oxide in dye-sensitized solar cells, PEC water-splitting systems, fuel cells, supercapacitors, and batteries. However, other nanostructured anodic films based on WO3, CuxO, ZnO, NiO, SnO, Fe2O3, ZrO2, Nb2O5, and Ta2O5 are also explored and act as the respective active layers in several devices. The use of AAO as a structural material to guide the synthesis is also reported. Although in the development stage, the proof-of-concept of these devices demonstrates the feasibility of using the anodic oxide as a component and opens up new perspectives for the industrial and commercial utilization of these technologies.  相似文献   
70.
Objectives. This study examined the psychometric properties of the Multidimensional Fatigue Symptom Inventory-Short Form (MFSI-SF) in a community-based sample of African-Americans.

Design. A sample of 340 African-Americans (116 men, 224 women) ranging in age from 18–81 years were recruited from the community (e.g., churches, health fairs, and beauty salons). Participants completed a brief demographic survey, the MFSI-SF and the Positive and Negative Affect Schedule.

Results. The structural validity of the MFSI-SF for a community-based sample of African-Americans was not supported. The five dimensions of fatigue (General, Emotional, Physical, Mental, Vigor) found for Whites in prior research were not found for African-Americans in this study. Instead, fatigue, while multidimensional for African-Americans, was best represented by a unique four-four profile in which general and emotional fatigue are collapsed into a single dimension and physical fatigue, mental fatigue, and vigor are relatively distinct. Hence, in the absence of modifications, the MFSI-SF cannot be considered to be structurally invariant across ethnic groups. A modified four-factor version of the MFSI-SF exhibited excellent internal consistency reliability and evidence supports its convergent validity. Using the modified four-factor version, gender, and age were not meaningfully associated with MFSI-SF scores.

Conclusion. Future research should further examine whether modifications to the MFSI-SF would, as the findings suggest, improve its validity as a measure of multidimensional fatigue in African-Americans.  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