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   411篇
  免费   21篇
  国内免费   7篇
耳鼻咽喉   1篇
儿科学   32篇
妇产科学   25篇
基础医学   47篇
口腔科学   7篇
临床医学   39篇
内科学   66篇
皮肤病学   6篇
神经病学   22篇
特种医学   7篇
外科学   56篇
综合类   9篇
预防医学   34篇
眼科学   8篇
药学   64篇
肿瘤学   16篇
  2023年   5篇
  2022年   6篇
  2021年   15篇
  2020年   10篇
  2019年   7篇
  2018年   11篇
  2017年   5篇
  2016年   8篇
  2015年   15篇
  2014年   14篇
  2013年   33篇
  2012年   23篇
  2011年   27篇
  2010年   16篇
  2009年   17篇
  2008年   30篇
  2007年   27篇
  2006年   18篇
  2005年   24篇
  2004年   14篇
  2003年   8篇
  2002年   3篇
  2001年   8篇
  2000年   7篇
  1999年   6篇
  1998年   8篇
  1997年   5篇
  1996年   3篇
  1995年   3篇
  1994年   1篇
  1993年   3篇
  1992年   7篇
  1991年   6篇
  1990年   7篇
  1989年   7篇
  1988年   8篇
  1987年   1篇
  1986年   7篇
  1985年   3篇
  1984年   1篇
  1983年   2篇
  1982年   1篇
  1980年   3篇
  1978年   1篇
  1976年   1篇
  1972年   1篇
  1965年   1篇
  1959年   1篇
  1951年   1篇
排序方式: 共有439条查询结果,搜索用时 0 毫秒
1.
BACKGROUND: The initial rate of plasma HIV-1 RNA (pVL) decline has been proposed as a marker of early efficacy of antiretroviral therapy (ART) and a possible predictor of late efficacy. We compared the rate of pVL decline in patients starting ART with nevirapine (NVP), efavirenz (EFV), or both drugs combined in addition to lamivudine (3TC) and stavudine (d4T). METHODS: Analysis of the viral decay constant (VDc) during the first 2 weeks of treatment in patients enrolled in the 2NN study who remained on allocated treatment. RESULTS: The median VDc (log10 copies per day, [interquartile range]) was similar for NVP (0.30 [0.25-0.36], EFV (0.31 [0.27-0.37]), and NVP + EFV (0.30 [0.27-0.36]). Patients with a baseline pVL >100,000 copies/mL were 8.7 (95% confidence interval [CI]: 6.2-12.3) times more likely to have a VDc >75th percentile. A high VDc was not associated with plasma drug concentration or with a decreased risk of virologic failure at week 48 after the start of therapy (hazard ratio = 0.8, 95% CI: 0.6-1.2). CONCLUSION: NVP, EFV, or NVP + EFV in combination with 3TC and d4T show similar rates of pVL decline during the first 2 weeks of treatment. The VDc with these regimens is not predictive of late virologic efficacy.  相似文献   
2.
Progesterone has been implicated in the process of spermatogenesis. This study aimed to investigate the association of progesterone receptor (PR) expression with spermatogenesis in the testis of infertile men. PR mRNA and protein were assessed by in-situ hybridization and immunohistochemistry in testicular biopsies obtained from 18 infertile men. The extent of spermatogenesis was assessed by Johnsen scoring. None of the patients included in the study had Yq microdeletions. PR expression was almost undetectable in all the testicular sections displaying Sertoli cell only (SCO) or arrest at spermatogonia. Weak cytoplasmic expression was observed in biopsies showing arrest at different stages of meiosis. In biopsies displaying spermatogenesis up to the round spermatid stages, PR expression was observed in both nucleus and cytoplasm of different cell types at intensity lower than that detected in normal biopsies. Normal PR expression was observed in biopsies demonstrating hypospermatogenesis. In biopsies showing mixed phenotypes, the tubules with SCO or spermatogonia arrest showed absence of PR expression; normal PR expression was observed in adjacent tubules showing complete spermatogenesis. Semi-quantitative assessment of PR expression and Johnsen scores in the testicular biopsies of infertile men demonstrating different phenotypes indicated a direct relationship between PR expression and extent of spermatogenesis.  相似文献   
3.
4.
5.
Influenza surveillance was conducted in Pune, India in 2003. A total of 573 throat swabs/ nasal swabs (TS/NS) and 190 nasopharyngeal aspirates (NPA) were collected from 763 in- and out-patients who were mostly children aged 0-16 years. TS/NS (507/573) and NPA (42/190) specimens were processed in MDCK cell cultures and identified with the hemagglutination inhibition test (HI). A total of 37 influenza viruses was isolated: twenty-three type A (H3N2) and 14 type B of the Yamagata lineage were isolated from 29 children and 8 adults. Three type A (H3N2) isolates were characterized as being similar to A/Panama/2007/99 like, A/Korea/770/2000 like, and B/Sichuan/379/99 like strains.  相似文献   
6.
Herein, a facile in situ solvothermal technique for the synthesis of a CdMoO4/graphene composite photocatalyst is reported. Graphene oxide (GO) was synthesised by an improved Hummers'' method and was further used for the in situ synthesis of graphene via GO reduction and the formation of a CdMoO4 nanowire/graphene composite. The structural phase formation of tetragonal CdMoO4 was confirmed from X-ray diffraction measurements. The small nanoparticle assembled nanowires, prismatic microsphere morphology and crystalline nature of the synthesized material were investigated using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). Due to its unique morphology and stability, the CdMoO4/graphene composite was used as a photocatalyst for H2O splitting. In comparison to pristine CdMoO4, the CdMoO4/graphene composite showed the best hydrogen evolution rate, i.e. 3624 μmole h−1 g−1, with an apparent quantum yield of 30.5%. The CdMoO4/graphene composite has a higher photocatalytic activity due to the inhibition of charge carrier recombination. H2 production measurements showed that the ternary semiconductor/graphene composite has enhanced photocatalytic activity for H2 generation.

Herein, a facile in situ solvothermal technique for the synthesis of a CdMoO4/graphene composite photocatalyst for hydrogen generation under natural solar light.  相似文献   
7.

PURPOSE

The purpose of this study was to explore the perceptions and experiences of health care clinicians working in multidisciplinary teams that include specialist heart failure nurses when caring for the management of heart failure patients.

METHODS

We used a qualitative in-depth interview study nested in a broader ethnographic study of unplanned admissions in heart failure patients (HoldFAST). We interviewed 24 clinicians across primary, secondary, and community care in 3 locations in the Midlands, South Central, and South West of England.

RESULTS

Within a framework of the role and contribution of the heart failure specialist nurse, our study identified 2 thematic areas that the clinicians agreed still represent particular challenges when working with heart failure patients. The first was communication with patients, in particular explaining the diagnosis and helping patients to understand the condition. The participants recognized that such communication was most effective when they had a long-term relationship with patients and families and that the specialist nurse played an important part in achieving this relationship. The second was communication within the team. Multidisciplinary input was especially needed because of the complexity of many patients and issues around medications, and the participants believed the specialist nurse may facilitate team communication.

CONCLUSIONS

The study highlights the role of specialist heart failure nurses in delivering education tailored to patients and facilitating better liaison among all clinicians, particularly when dealing with the management of comorbidities and drug regimens. The way in which specialist nurses were able to be caseworkers for their patients was perceived as a method of ensuring coordination and continuity of care.  相似文献   
8.
Sol–gel-synthesized Co–Cu–Zn ferrite nanoparticles diluted with Dy3+ ions were investigated in terms of their structural, morphological, elastic, magnetic and dielectric properties. X-ray diffraction patterns showed the formation of a single-phase cubic spinel structure. As the concentration of Dy3+ ions was increased, the lattice length gradually increased from 8.340 to 8.545 Å, obeying Vegard''s law. The Williamson–Hall (W–H) method was employed to observe the change in the lattice strain. Crystallite size obtained from W–H plots followed a pattern similar to that observed using the Scherrer equation. The cation distribution suggested a strong preference of Dy3+ ions for the octahedral B site while Cu2+ and Fe3+ ions were distributed over both A and B sites. The microstructures of the samples were visualized using transmission electron microscopy. Mechanical properties such as stiffness constant, longitudinal and transverse wave velocities, Young''s modulus, bulk modulus, rigidity modulus, Poisson''s ratio and Debye temperature were investigated by acquiring infrared spectra recorded in the range of 300 to 800 cm−1. Replacement of Fe3+ ions with the strongly magnetic Dy3+ ions increased the saturation magnetization and coercivity. Dielectric constant increased with Dy3+ substitution but decreased with applied frequency.

Improvement in various properties of Co–Cu–Zn ferrite upon Dy substitution.  相似文献   
9.
10.
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