全文获取类型
收费全文 | 4389篇 |
免费 | 519篇 |
国内免费 | 312篇 |
专业分类
耳鼻咽喉 | 52篇 |
儿科学 | 32篇 |
妇产科学 | 42篇 |
基础医学 | 503篇 |
口腔科学 | 39篇 |
临床医学 | 680篇 |
内科学 | 631篇 |
皮肤病学 | 68篇 |
神经病学 | 231篇 |
特种医学 | 178篇 |
外科学 | 442篇 |
综合类 | 631篇 |
现状与发展 | 2篇 |
一般理论 | 1篇 |
预防医学 | 352篇 |
眼科学 | 145篇 |
药学 | 491篇 |
3篇 | |
中国医学 | 277篇 |
肿瘤学 | 420篇 |
出版年
2024年 | 12篇 |
2023年 | 85篇 |
2022年 | 222篇 |
2021年 | 252篇 |
2020年 | 216篇 |
2019年 | 205篇 |
2018年 | 181篇 |
2017年 | 159篇 |
2016年 | 168篇 |
2015年 | 237篇 |
2014年 | 308篇 |
2013年 | 206篇 |
2012年 | 344篇 |
2011年 | 338篇 |
2010年 | 220篇 |
2009年 | 156篇 |
2008年 | 270篇 |
2007年 | 236篇 |
2006年 | 189篇 |
2005年 | 204篇 |
2004年 | 108篇 |
2003年 | 102篇 |
2002年 | 113篇 |
2001年 | 84篇 |
2000年 | 85篇 |
1999年 | 109篇 |
1998年 | 82篇 |
1997年 | 68篇 |
1996年 | 51篇 |
1995年 | 41篇 |
1994年 | 39篇 |
1993年 | 18篇 |
1992年 | 27篇 |
1991年 | 16篇 |
1990年 | 19篇 |
1989年 | 9篇 |
1988年 | 10篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 6篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 2篇 |
排序方式: 共有5220条查询结果,搜索用时 31 毫秒
131.
目的观察和总结心电散点图在心率变异性(HRV)分析中的作用,寻找提高HRV分析准确性的方法。方法对321例动态心电图数据HRV心电散点图与时域、频域指标进行相关分析,观察心电散点图指标的特点。结果心电散点图用于表达HRV的各项指标与时域、频域指标,有对应关系,心电散点图视觉直观性强,能分辨出真实窦性心搏图形与干扰伪差图形,窦性心搏图形具有多态性和个体唯一性。结论心电散点图可独立用于HRV分析。对于记录不良,伪差干扰较多的心电数据,时、频域分析结果易受其影响,应以散点图的窦性心搏图形作为判断HRV的依据。对于记录质量较好的数据,可根据对散点图形的目测,检验时域、频域分析的准确性。一份高质量的HRV分析报告的标志是散点图、时域、频域三种分析结果中各相关指标的高度相关。 相似文献
132.
A high monosaccharide conversion rate of hemicellulose in a green solvent and under moderate reaction conditions for industrialization is one of the most important keys in a lignocellulosic biorefinery. The behavior of Populus tomentosa hemicellulose polysaccharides, crystallinity and the furfural formation in the autohydrolysis process under moderate subcritical water conditions (160–180 °C, 0.618–1.002 MPa) were studied. The results have shown that the hemicellulose was converted to corresponding monosaccharides at an ultra-high hydrolysis rate. Factor analysis indicates that the temperature is the most important factor affecting hemicellulose autohydrolysis. When the autohydrolysis temperature increased from 160 to 180 °C for 2 h, the hydrolysis rate of xylose, rhamnose, galactose, mannose, and glucose from hemicellulose increased from 70% to 91%, 71% to 100%, 82% to 95%, 42% to 58%, and 34% to 37%, respectively. Arabinose was completely dissolved in 30 min. The xylose, rhamnose, galactose, and arabinose from hemicellulose could be almost completely removed under the conditions. The hemicellulose removal rate obtained herein exceeded the values reported for most acid, alkali, ionic liquid, or deep eutectic solvent treatments. It is notable that almost all glucose in hemicellulose was dissolved and the glucose in cellulose was partially hydrolyzed. An analysis of the sugar composition and the crystallinity change in the process at 180 °C demonstrate that hydrolysis reaction started to shift from amorphous regions to crystalline regions, due to the partial hydrolysis of crystalline cellulose after 90 min at 180 °C. Overall, these results show that the moderate subcritical water autohydrolysis of hemicellulose in Populus tomentosa may be a potential bio-refinery process.A high monosaccharide conversion rate of hemicellulose in a green solvent and under moderate reaction conditions for industrialization is one of the most important keys in a lignocellulosic biorefinery. 相似文献
133.
The existence of fine-sized oil drops that are difficult to coalesce greatly decreases the separation efficiency of produced water from alkali, surfactant, and polymer flooding technology (ASP) containing oil-in-water emulsions. To improve oil–water separation efficiency, a silica-supported polyether polysiloxane quaternary ammonium (abbreviated as PPQA@SiO2) demulsifier was synthesized. The supported demulsifier possesses a rough surface structure and large surface area. In addition, it displays high thermal stability. It was applied for treating the produced water from ASP flooding. The effects of dosage, treatment temperature and treatment time on the oil removal efficiency from ASP produced water were investigated. Owing to the synergetic effect of demulsification and adsorption, the supported demulsifier exhibited an oil removal greater than 92% within 50 min at the initial oil concentration of 300 mg L−1, which is much higher than that of a commercial demulsifier SA001 (40.33%). Furthermore, the demulsification mechanism was explored from the perspective of the zeta potential, mean diameter and size distribution of the oil droplets. The high oil removal efficiency establishes PPQA@SiO2 as a promising candidate for oil–water separation from the ASP flooding produced wastewater.The existence of fine-sized oil drops that are difficult to coalesce greatly decreases the separation efficiency of produced water from alkali, surfactant, and polymer flooding technology (ASP) containing oil-in-water emulsions. 相似文献
134.
It is a great challenge to tune the porosity of porous materials. As most porous organic cages are soluble, solution processability can be a possible way to regulate the porosity of such materials. Herein, a triptycene-based cage (TC) is demonstrated to be stable in acid, base or boiling water. Meanwhile, its porosity can be tuned by adjusting the solution-state assembly processes. TC molecules crystallized slowly from solution exhibit nearly no porosity to nitrogen (off-state). While, after rapid precipitating from methanol/dichloromethane solution, the obtained TC (TC-rp) is in a porous state and exhibit a high BET surface area of 653 m2 g−1 (on-state).Here, a kind of triptycene-based cage is demonstrated to have good chemical stability in acid, base and boiling water. Moreover, its porosity can be tuned by varying the solution-state assembly processes. 相似文献
135.
Hydrophobic clinoptilolite (CP) was successfully synthesized via a silanization method using methyltriethoxysilane (MTS) or diethoxydimethylsilane (DMTS) as silane coupling agents. The structural and textural properties of the resultant hydrophobic CP were characterized using various methods. The effect of the amount of MTS or DMTS additive on the induction (nucleation) and growth of CP were also investigated, and the apparent activation energy values for induction and growth periods were calculated, suggesting that the induction period is kinetically controlled, while the rapid growth process is thermodynamically controlled. Meanwhile, DMTS modification enhanced the hydrophobicity of CP compared with its MTS-modified counterpart and pure CP. Finally, various ZnO-supported CPs were used as photocatalysts for the removal of crystal violet from aqueous solution, demonstrating that ZnO/hydrophobic CP has the largest adsorption capacity and best removal performance. These results suggest that hydrophobic CP, as an adsorbent or support, has the most potential for applications in separation and catalysis.One-step synthesis of hydrophobic CPs was demonstrated, in which the kinetically-controlled induction period and thermodynamically-based rapid growth process were elucidated. 相似文献
136.
Changhe Hou Yangchun Zhang Shiming Yu Ziqing Li Qiyi Zhai Zhanchun Li Xibao Zhang Jianhong Xiao Puyi Sheng 《International orthopaedics》2013,37(5):953-959
Purpose
The most common long-term complication of joint arthroplasty is aseptic loosening. The proinflammatory cytokines secreted by macrophages are involved in aseptic loosening. Recently, a novel proinflammatory cytokine IL-17C was reported to participate in inflammatory diseases by synergising with proinflammatory cytokines. However, the relationship between IL-17C and the aseptic loosening is unclear.Methods
The tissues around aseptic loosened implants were collected during revision surgery and handled by formalin fixation and embedded in paraffin. The presence of IL-17C in the tissues around the aseptic loosened implants was investigated in 12 aseptic loosening patients using immunofluorescence.Results
The presence of IL-17C protein in the tissues around aseptic loosened implants was detected by immunofluorescence. There are no statistical differences between optical density of IL-17C in aseptic loosening samples and in rheumatoid arthritis samples (positive control).Conclusions
These results suggest the presence of IL-17C in aseptic loosening. Interleukin-17C was related to the inflammation of aseptic loosening, possibly by contributing to the inflammation and osteolysis in the tissues surrounding aseptic loosened implants. 相似文献137.
138.
ABSTRACTObjective: Exposure to female estrous, a natural rewarding experience, alleviates anxiety and depression, and the contribution of this behavior to stroke outcome is unknown. The aim of this study was to evaluate whether exposure to female estrous is beneficial to recovery following transient ischemic stroke in male mice.Methods: Cerebral ischemia was induced in male ICR mice with thread occlusion of the middle cerebral artery (MCAO) for 30 min followed by reperfusion. MCAO mice were randomly divided into MCAO group and Estrous Female Exposure (EFE) group. The mice in the EFE group were subjected to estrous female mouse interaction from day 1 until the end of the experiment. Mortality was recorded during the investigation. Behavioral functions were assessed by a beam-walking test and corner test from day 1 to day 10 after MCAO. Serum testosterone levels were analyzed with ELISA, and the expression levels of growth-associated protein-43 (GAP-43) and synaptophysin in the cortex of the ischemic hemisphere were determined by western blot on day 7 after MCAO.Results: Exposure to female estrous reduced the mortality induced by cerebral ischemic lesions. The beam-walking test demonstrated that exposure to female estrous significantly improved motor function recovery. The serum testosterone levels and ischemic cortex GAP-43 expression were significantly higher in MCAO male mice exposed to female estrous.Conclusion: Exposure to female estrous reduces mortality and improves functional recovery in MCAO male mice. The study provides the first evidence to support the importance of female interaction to male stroke rehabilitation.Abbreviations: GAP-43: growth-associated protein-43; SYP: Synaptophysin; MCAO: middle cerebral artery occlusion; OVXs: ovariectomies; CCA: common carotid artery; ECA: external carotid artery; EFE: estrous female exposure; TTC: 2,3,5-triphenyltetrazolium chloride; PAGE: polyacrylamide gel electrophoresis; PVDF: polyvinylidene difluoride; ANOVA: analysis of variance; LSD: least significant difference 相似文献
139.
140.
Liu Chunyan Zhai Huajie Su Shuhua Song Sutao Chen Gongxiang Jiang Yi 《Journal of autism and developmental disorders》2022,52(11):4861-4871
Journal of Autism and Developmental Disorders - Previous studies have found reduced leftward bias of facial processing in individuals with Autism Spectrum Disorder (ASD). However, it is not clear... 相似文献