全文获取类型
收费全文 | 3671篇 |
免费 | 192篇 |
国内免费 | 25篇 |
专业分类
耳鼻咽喉 | 16篇 |
儿科学 | 79篇 |
妇产科学 | 84篇 |
基础医学 | 411篇 |
口腔科学 | 74篇 |
临床医学 | 262篇 |
内科学 | 878篇 |
皮肤病学 | 148篇 |
神经病学 | 318篇 |
特种医学 | 99篇 |
外科学 | 716篇 |
综合类 | 16篇 |
预防医学 | 314篇 |
眼科学 | 43篇 |
药学 | 187篇 |
中国医学 | 25篇 |
肿瘤学 | 218篇 |
出版年
2023年 | 21篇 |
2022年 | 46篇 |
2021年 | 91篇 |
2020年 | 56篇 |
2019年 | 98篇 |
2018年 | 108篇 |
2017年 | 85篇 |
2016年 | 78篇 |
2015年 | 90篇 |
2014年 | 129篇 |
2013年 | 162篇 |
2012年 | 288篇 |
2011年 | 305篇 |
2010年 | 151篇 |
2009年 | 155篇 |
2008年 | 207篇 |
2007年 | 265篇 |
2006年 | 244篇 |
2005年 | 229篇 |
2004年 | 211篇 |
2003年 | 183篇 |
2002年 | 161篇 |
2001年 | 55篇 |
2000年 | 44篇 |
1999年 | 41篇 |
1998年 | 25篇 |
1997年 | 19篇 |
1996年 | 22篇 |
1995年 | 13篇 |
1994年 | 18篇 |
1993年 | 14篇 |
1992年 | 25篇 |
1991年 | 23篇 |
1990年 | 20篇 |
1989年 | 23篇 |
1988年 | 12篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1984年 | 10篇 |
1983年 | 10篇 |
1982年 | 8篇 |
1980年 | 9篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 13篇 |
1976年 | 11篇 |
1975年 | 6篇 |
1974年 | 12篇 |
1970年 | 10篇 |
排序方式: 共有3888条查询结果,搜索用时 31 毫秒
81.
Mortality after hospitalization for COPD 总被引:20,自引:0,他引:20
Almagro P Calbo E Ochoa de Echagüen A Barreiro B Quintana S Heredia JL Garau J 《Chest》2002,121(5):1441-1448
OBJECTIVES: To identify variables associated with mortality in patients admitted to the hospital for acute exacerbation of COPD. DESIGN: Prospective cohort study. SETTING: Acute-care hospital in Barcelona (Spain). PATIENTS: One hundred thirty-five consecutive patients hospitalized for acute exacerbation of COPD, between October 1996 and May 1997. MEASUREMENTS AND RESULTS: Clinical, spirometric, and gasometric variables were evaluated at the time of inclusion in the study. Socioeconomic characteristics, comorbidity, dyspnea, functional status, depression, and quality of life were analyzed. Mortality at 180 days, 1 year, and 2 years was 13.4%, 22%, and 35.6%, respectively. Sixty-four patients (47.4%) were dead at the end of the study (median follow-up duration, 838 days). Greater mortality was observed in the bivariate analysis among the oldest patients (p < 0.0001), women (p < 0.01), and unmarried patients (p < 0.002). Hospital admission during the previous year (p < 0.001), functional dependence (Katz index) [p < 0.0004], greater comorbidity (Charlson index) [p < 0.0006], depression (Yesavage Scale) [p < 0.00001]), quality of life (St. George's Respiratory Questionnaire [SGRQ]) [p < 0.01], and PCO(2) at discharge (p < 0.03) were also among the significant predictors of mortality. In the multivariate analysis, the activity SGRQ subscale (p < 0.001; odds ratio [OR], 2.62; confidence interval [CI], 1.43 to 4.78), comorbidity (p < 0.005; OR, 2.2; CI, 1.26 to 3.84), depression (p < 0.004; OR, 3.6; CI, 1.5 to 8.65), hospital readmission (p < 0.03; OR, 1.85; CI, 1.26 to 3.84), and marital status (p < 0.0002; OR, 3.12; CI, 1.73 to 5.63) were independent predictors of mortality. CONCLUSIONS: Quality of life, marital status, depressive symptoms, comorbidity, and prior hospital admission provide relevant information of prognosis in this group of COPD patients. 相似文献
82.
Plasma concentration of asymmetric dimethylarginine,an endogenous inhibitor of nitric oxide synthase,is elevated in hyperthyroid patients 总被引:3,自引:0,他引:3
Hermenegildo C Medina P Peiró M Segarra G Vila JM Ortega J Lluch S 《The Journal of clinical endocrinology and metabolism》2002,87(12):5636-5640
Cardiovascular manifestations are frequent findings in patients with thyroid hormone disorders. Nitric oxide (NO) plays a key role in vascular, endothelial-mediated relaxation. NO is synthesized from L-arginine by NO synthase, an enzyme inhibited by endogenous compounds, mainly asymmetric dimethylarginine [asymmetric N(G),N(G)-dimethyl-L-arginine (ADMA)]. The aim of our work was to investigate whether plasma L-arginine and dimethylarginine concentrations and NO production are altered in hypo- and hyperthyroid patients, compared with control subjects. L-arginine, ADMA and symmetric dimethylarginine were analyzed by HPLC. NO was measured as plasma nitrite plus nitrate (NO(x)) concentration by a colorimetric method based on Griess reagent. L-arginine, ADMA, and symmetric dimethylarginine plasma levels in the hypothyroid group were similar to those of the control group; whereas in hyperthyroidism, these values were significantly increased. However, the L-arginine/ADMA ratio was decreased in hyperthyroid patients, resulting in diminished NO(x) production. When all subjects were analyzed together, free T(4) levels were directly correlated with ADMA and inversely correlated with NO(x). 相似文献
83.
Resino S Galán I Pérez A Ramos JT Bellón JM Fontelos PM de José MI Gutiérrez MD Cabrero E Muñoz-Fernández MA 《AIDS research and human retroviruses》2005,21(5):398-406
We evaluated the effect of salvage antiretroviral therapy with lopinavir/ritonavir (LPV/r) on the immune system of heavily antiretroviral pretreated HIV-infected children. We carried out a longitudinal study in 20 antiretroviral experienced HIV-infected children to determine the changes in several immunological parameters (T cell subsets, thymic function) every 3 months during 18 months of follow-up on salvage therapy with LPV/r. Statistical analyses were performed with the Wilcoxon test, taking as a reference the basal value at the entry in the study. HIV-infected children showed an increase of CD4+ T cells, a decrease in CD8+ T cells, and an increase in T cell rearrangement excision circle (TRECs) levels. The percentage of HIV children with undetectable viral load (VL < or = 400 copies/ml) increased significantly (p = 0.007) and the percentage with SI viral phenotype decreased significantly (p = 0.002) at the end of the study. Thus, the viral phenotype changed to NSI/R5 after salvage therapy with LPV/r. Interestingly, we observed a significant decrease of memory (CD4+ CD45RO+) and a moderate decrease of activated (CD4+ HLA-DR+, CD4+ HLA-DR+CD38, CD4+, CD45RO+HLA-DR+) CD4+ T cells during the follow-up. On the other hand, memory (CD8+ CD45RO+ and CD8+ CD45RO+CD38+), activated (CD8+ HLA-DR+CD38+, CD8+ HLA-DR+, CD8+ CD38+), and effector (CD8+ CD57+, CD8+ CD28(-)CD57+) CD8+ T cells had a very significant decrease during follow-up. Our data indicate an immune system reconstitution in heavily pretreated HIV-infected children in response to salvage therapy with LPV/r as a consequence of a decrease in immune system activation and an increase in thymic function. 相似文献
84.
In this paper, the approach to the genesis of the acute hypertension of pregnancy, uses a conceptual and methodological perspective adjusted to its multifactorial nature; a set of questions with epidemiologic focus is proposed, in order to vinculate psychosocial factors with the biologic processes characteristic of this health problem. 相似文献
85.
Salvador MJ Sebaoun A Sonntag F Blanch P Silber S Aznar J Komajda M;Council for Cardiology Practice de la Sociedad Europea de Cardiologia 《Revista espa?ola de cardiología》2004,57(12):1170-1178
INTRODUCTION AND OBJECTIVES: This cross-sectional study examined the overall clinical characteristics and management of 1252 outpatients with heart failure in 3 countries (Spain, France and Germany). MATERIAL AND METHOD: A standardized questionnaire was used to record demographic, diagnostic, clinical and treatment data for all patients seen on one day (26 April 2001) by 465 outpatient cardiologists. RESULTS: Men accounted for 62.1% of the patients in the population, and mean age of the patients was 68.3 years. In the twelve months prior to the study 78% of the patients consulted their physician at least once because of heart failure, and 36.2% had hospital admissions. Differences between the three countries were observed in reported causes of heart failure (alone or in combination) such as ischemic heart disease (France 40.7%, Germany 41.3%, Spain 26%, P<.0001) and hypertension (France 10.7%, Germany 16.7%, Spain 43.6%, P<.0001). How-ever the proportion of patients with prior myocardial infarction was very similar (France 63.7%, Germany 69.5%, Spain 65%, P=NS). Diuretics were not prescribed in 19.7% of the patients, ACE inhibitors were not prescribed in 27.9%, and beta blockers were not prescribed in 52.3%. CONCLUSIONS: The study provides further information on the consumption of large amounts of medical resources because of heart failure. The reported etiologies differed between countries. However, the proportion of patients with prior myocardial infarction was very similar. Treatment with ACE inhibitors and beta blockers was slightly more common than previously reported, although beta blockers continue to be underused. 相似文献
86.
Giuseppe M. Peretti Vanessa Campo-Ruiz Salvador Gonzalez Mark A. Randolph Jian Wei Xu Kenneth R. Morse 《Connective tissue research》2013,54(4):190-199
This study investigated the in vivo formation of engineering cartilage within living or devitalized cartilage discs using reflectance mode confocal microscopy and conventional light microscopy. Pig articular chondrocytes were suspended in fibrin glue and placed between two cartilage discs. Four experimental groups were prepared: in groups 1 and 2, the cell-hydrogel composite was placed between two live or between two devitalized cartilage discs, respectively; in groups 3 and 4, acellular fibrin glue was placed between two live or between two devitalized cartilage discs, respectively. Samples were implanted in the back of nude mice and analyzed after 2, 5, and 8 weeks. Results showed that engineered cartilage seems to grow more homogenously when the cell-seeded gel was placed between devitalized cartilages than when it was placed between live cartilage matrices. Confocal microscopy provides valuable information on the integration of tissue-engineered cartilage with native tissue and could be useful for nondestructive imaging in vivo. 相似文献
87.
Maria Loane Joan K Morris Marie-Claude Addor Larraitz Arriola Judith Budd Berenice Doray Ester Garne Miriam Gatt Martin Haeusler Babak Khoshnood Kari Klungs?yr Melve Anna Latos-Bielenska Bob McDonnell Carmel Mullaney Mary O'Mahony Annette Quei?er-Wahrendorf Judith Rankin Anke Rissmann Catherine Rounding Joaquin Salvador David Tucker Diana Wellesley Lyubov Yevtushok Helen Dolk 《European journal of human genetics : EJHG》2013,21(1):27-33
This study examines trends and geographical differences in total and live birth prevalence of trisomies 21, 18 and 13 with regard to increasing maternal age and prenatal diagnosis in Europe. Twenty-one population-based EUROCAT registries covering 6.1 million births between 1990 and 2009 participated. Trisomy cases included live births, fetal deaths from 20 weeks gestational age and terminations of pregnancy for fetal anomaly. We present correction to 20 weeks gestational age (ie, correcting early terminations for the probability of fetal survival to 20 weeks) to allow for artefactual screening-related differences in total prevalence. Poisson regression was used. The proportion of births in the population to mothers aged 35+ years in the participating registries increased from 13% in 1990 to 19% in 2009. Total prevalence per 10 000 births was 22.0 (95% CI 21.7–22.4) for trisomy 21, 5.0 (95% CI 4.8–5.1) for trisomy 18 and 2.0 (95% CI 1.9–2.2) for trisomy 13; live birth prevalence was 11.2 (95% CI 10.9–11.5) for trisomy 21, 1.04 (95% CI 0.96–1.12) for trisomy 18 and 0.48 (95% CI 0.43–0.54) for trisomy 13. There was an increase in total and total corrected prevalence of all three trisomies over time, mainly explained by increasing maternal age. Live birth prevalence remained stable over time. For trisomy 21, there was a three-fold variation in live birth prevalence between countries. The rise in maternal age has led to an increase in the number of trisomy-affected pregnancies in Europe. Live birth prevalence has remained stable overall. Differences in prenatal screening and termination between countries lead to wide variation in live birth prevalence. 相似文献
88.
Arely Bahena Ilse Magaa Hctor Ricardo Lpez Gonzlez Rishab Handa Francisco Javier Enríquez-Medrano Sugam Kumar Ricardo Mendoza Carrizales Salvador Fernandez Luis Valencia Ramn Enrique Díaz de Len Gmez 《RSC advances》2020,10(60):36531
This article proposes a method to produce bio-elastomer nanocomposites, based on polyfarnesene or polymyrcene, reinforced with surface-modified graphene oxide (GO). The surface modification is performed by grafting alkylamines (octyl-, dodecyl-, and hexadecylamine) onto the surface of GO. The successful grafting was confirmed via spectroscopic (FTIR and Raman) and X-ray diffraction techniques. The estimated grafted amines appear to be around 30 wt%, as calculated via thermogravimetric analysis, increasing the inter-planar spacing among the nanosheets as a function of alkyl length in the amine. The resulting modified GOs were then used to prepare bio-elastomer nanocomposites via in situ coordination polymerization (using a ternary neodymium-based catalytic system), acting as reinforcing additives of polymyrcene and polyfarnesene. We demonstrated that the presence of the modified GO does not affect significantly the catalytic activity, nor the microstructure-control of the catalyst, which led to high cis-1,4 content bio-elastomers (>95%). Moreover, we show via rheometry that the presence of the modified-GO expands the capacity of the elastomer to store deformation or applied stress, as well as exhibit an activation energy an order of magnitude higher.This article proposes a method to produce bio-elastomer nanocomposites, based on polyfarnesene or polymyrcene, reinforced with surface-modified graphene oxide (GO). 相似文献
89.