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   2561篇
  免费   100篇
  国内免费   11篇
耳鼻咽喉   83篇
儿科学   91篇
妇产科学   126篇
基础医学   329篇
口腔科学   34篇
临床医学   153篇
内科学   632篇
皮肤病学   44篇
神经病学   267篇
特种医学   46篇
外科学   170篇
综合类   17篇
预防医学   197篇
眼科学   59篇
药学   277篇
中国医学   2篇
肿瘤学   145篇
  2023年   9篇
  2022年   76篇
  2021年   125篇
  2020年   40篇
  2019年   70篇
  2018年   62篇
  2017年   62篇
  2016年   65篇
  2015年   82篇
  2014年   119篇
  2013年   137篇
  2012年   226篇
  2011年   225篇
  2010年   110篇
  2009年   94篇
  2008年   146篇
  2007年   186篇
  2006年   181篇
  2005年   180篇
  2004年   150篇
  2003年   150篇
  2002年   122篇
  2001年   6篇
  2000年   2篇
  1999年   4篇
  1998年   8篇
  1997年   4篇
  1996年   6篇
  1995年   8篇
  1994年   2篇
  1992年   1篇
  1991年   2篇
  1990年   5篇
  1988年   1篇
  1987年   1篇
  1981年   1篇
  1974年   1篇
  1972年   1篇
  1967年   1篇
  1925年   1篇
排序方式: 共有2672条查询结果,搜索用时 15 毫秒
91.

The described application of granular computing is motivated because cardiovascular disease (CVD) remains a major killer globally. There is increasing evidence that abnormal respiratory patterns might contribute to the development and progression of CVD. Consequently, a method that would support a physician in respiratory pattern evaluation should be developed. Group decision-making, tri-way reasoning, and rough set–based analysis were applied to granular computing. Signal attributes and anthropomorphic parameters were explored to develop prediction models to determine the percentage contribution of periodic-like, intermediate, and normal breathing patterns in the analyzed signals. The proposed methodology was validated employing k-nearest neighbor (k-NN) and UMAP (uniform manifold approximation and projection). The presented approach applied to respiratory pattern evaluation shows that median accuracies in a considerable number of cases exceeded 0.75. Overall, parameters related to signal analysis are indicated as more important than anthropomorphic features. It was also found that obesity characterized by a high WHR (waist-to-hip ratio) and male sex were predisposing factors for the occurrence of periodic-like or intermediate patterns of respiration. It may be among the essential findings derived from this study. Based on classification measures, it may be observed that a physician may use such a methodology as a respiratory pattern evaluation-aided method.

  相似文献   
92.
Infections related to orthopedic procedures are considered particularly severe when implantation materials are used, because effective treatments for biofilm removal are lacking. In this study, the relatively new approach for infection control by using an erbium:yttrium-aluminum-garnet (Er:YAG) laser was tested. This laser vaporizes all water containing cells in a very effective, precise, and predictable manner and results in only minimal thermal damage. For preliminary testing, 42 steel plates and 42 pins were seeded with mixed cultures. First, the minimally necessary laser energy for biofilm removal was determined. Subsequently, the effectiveness of biofilm removal with the Er:YAG laser and the cleansing of the metal implants with octenidine-soaked gauze was compared. Then, we compared the effectiveness of biofilm removal on 207 steel pins from 41 patients directly after explantation. Sonication and scanning electron microscopy were used for analysis. Laser fluences exceeding 2.8 J/cm2 caused a complete extinction of all living cells by a single-laser impulse. Cleansing with octenidine-soaked gauze and irradiation with the Er:YAG laser are both thoroughly effective when applied to seeded pins. In contrast, when explanted pins with fully developed biofilms were analyzed, we found a significant advantage of the laser procedure. The Er:YAG laser offers a secure, complete, and nontoxic eradication of all kinds of pathogens from metal implants without damaging the implant and without the possible development of resistance. The precise noncontact removal of adjacent tissue is a decisive advantage over conventional disinfectants. Therefore, laser irradiation could become a valuable method in every debridement, antibiotics, and implant retention procedure.  相似文献   
93.
94.
95.

Purpose

Tacrolimus (Tac) and cyclosporine (CsA) are mainly metabolized by CYP3A4 and CYP3A5. Several studies have demonstrated an association between the CYP3A5 genotype and Tac dose requirements. Recently, CYP3A4, PPARA, and POR gene variants have been shown to influence CYP3A metabolism. The present study investigated potential associations between CYP3A5*3, CYP3A4*22, PPARA c.209-1003G>A and c.208?+?3819A>G, and POR*28 alleles and dose-adjusted concentrations (C/D) of Tac and CsA in 177 renal transplant patients early post-transplant.

Methods

All patients (n?=?177) were genotyped for CYP3A4*22, CYP3A5*3, POR*28, PPARA c.209-1003G>A, and PPARA c.208?+?3819A>G using real-time polymerase chain reaction (PCR) and melting curve analysis with allele-specific hybridization probes or PCR restriction fragment length polymorphisms (RFLP) methods. Drug concentrations and administered doses were retrospectively collected from patient charts at Oslo University Hospital, Rikshospitalet, Norway. One steady-state concentration was collected for each patient.

Results

We confirmed a significant impact of the CYP3A5*3 allele on Tac exposure. Patients with POR*28 and PPARA variant alleles demonstrated 15 % lower (P?=?0.04) and 19 % higher (P?=?0.01) Tac C0/D respectively. CsA C2/D was 53 % higher among CYP3A4*22 carriers (P?=?0.03).

Conclusion

The results support the use of pre-transplant CYP3A5 genotyping to improve initial dosing of Tac, and suggest that Tac dosing may be further individualized by additional POR and PPARA genotyping. Furthermore, initial CsA dosing may be improved by pre-transplant CYP3A4*22 determination.  相似文献   
96.
97.
In this study, hydrogels based on chitosan cross-linked by glyoxal have been investigated for potential medical applications. Hydrogels were loaded with tannic acid at different concentrations. The thermal stability and the polyphenol-releasing rate were determined. For a preliminary assessment of the clinical usefulness of the hydrogels, they were examined for blood compatibility and in the culture of human dental pulp cells (hDPC). The results showed that after immersion in a polyphenol solution, chitosan/glyoxal hydrogels remain nonhemolytic for erythrocytes, and we also did not observe the cytotoxic effect of hydrogels immersed in tannic acid (TA) solutions with different concentration. Tannic acid was successfully released from hydrogels, and its addition improved material thermal stability. Thus, the current findings open the possibility to consider such hydrogels in clinics.  相似文献   
98.
The article presents the results of research on the structural evolution of the composite Fe-Al-based coating deposited by arc spray with initial low participation of in situ intermetallic phases. The arc spraying process was carried out by simultaneously melting two different electrode wires, aluminum and low alloy steel (98.6 wt.% of Fe). The aim of the research was to reach protective coatings with a composite structure consisting of a significant participation of FexAly as intermetallic phases reinforcement. Initially, synthesis of intermetallic phases took place in situ during the spraying process. In the next step, participation of FexAly fraction was increased through the annealing process, with three temperature values, 700 °C, 800 °C, and 900 °C. Phase structure evolution of the Fe-Al arc-sprayed coating, stimulated by annealing, has been described by means of SEM images taken with a QBSD backscattered electron detector and by XRD and conversion electron Mössbauer spectroscopy (CEMS) investigations. Microhardness distribution of the investigated annealed coatings has been presented.  相似文献   
99.
The article presents the results of research aimed at examining the type of swelling material introduced into moulding or core sand to improve their knock-out properties. Tests on Slovak perlite ore (three grain sizes), Hungarian perlite ore and ground vermiculite (South Africa) were carried out. For this purpose, thermal and structural analyses (FTIR—Fourier Transform Infrared Spectroscopy), a chemical composition test (XRF-X-Ray Fluorescence), phase analysis (XRD—X-Ray Diffraction), and scanning electron microscopy (SEM—Scanning Electron Microscope) as well as final strength tests of moulding sands with the addition of perlite ore and vermiculite were carried out. The results of thermal studies were related to IR (Infrared Spectroscopy) spectra and XRD diffractograms. It has been shown that the water content in the pearlite ore is almost three times lower than in vermiculite, but the process of its removal is different. Moreover, the chemical composition of the perlite ore, in particular the alkali content and its grain size, may influence its structure. The phenomena of expansion (perlite) and peeling (vermiculite) have a positive effect on the reduction of the final sand strength and eliminate technological inconveniences (poor knocking out) that significantly limit the wide use of moulding sands with inorganic binders.  相似文献   
100.
Vitamin D deficiency seems to be implicated in the onset and progression of some autoimmune disorders. No previous study has investigated vitamin D homeostasis in post‐partum thyroiditis. We compared 25‐hydroxyvitamin D and parathyroid hormone (PTH) levels between four groups of non‐lactating women who gave birth within 12 months before the beginning of the study: hypothyroid women with post‐partum thyroiditis (group A; n = 14), euthyroid females with post‐partum thyroiditis (group B; n = 14), women with non‐autoimmune hypothyroidism (group C; n = 16) and healthy euthyroid females without thyroid autoimmunity (group D; n = 15). In the second part of the study, groups A and C were treated for 6 months with l ‐thyroxine. Serum levels of 25‐hydroxyvitamin D were lower, while PTH higher in patients with post‐partum thyroiditis than in patients without thyroid autoimmunity. They were also lower (25‐hydroxyvitamin D) or higher (PTH) in group A than in group B, as well as in group C in comparison with group D. l ‐thyroxine treatment increased 25‐hydroxyvitamin D and reduced PTH levels only in hypothyroid women with post‐partum thyroiditis. Baseline levels of 25‐hydroxyvitamin D correlated with thyroid antibody titres, thyroid function and circulating PTH levels, while the effect of l ‐thyroxine on serum levels of this vitamin correlated with the changes in thyroid antibody titres and PTH levels. The results of our study suggest the association of vitamin D status with post‐partum thyroiditis and l ‐thyroxine treatment of this disorder.  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