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   1728篇
  免费   83篇
  国内免费   11篇
耳鼻咽喉   26篇
儿科学   74篇
妇产科学   68篇
基础医学   318篇
口腔科学   9篇
临床医学   88篇
内科学   421篇
皮肤病学   17篇
神经病学   217篇
特种医学   22篇
外科学   72篇
综合类   18篇
预防医学   143篇
眼科学   97篇
药学   141篇
中国医学   2篇
肿瘤学   89篇
  2023年   6篇
  2022年   55篇
  2021年   96篇
  2020年   34篇
  2019年   43篇
  2018年   58篇
  2017年   40篇
  2016年   39篇
  2015年   55篇
  2014年   59篇
  2013年   78篇
  2012年   124篇
  2011年   133篇
  2010年   69篇
  2009年   36篇
  2008年   117篇
  2007年   128篇
  2006年   145篇
  2005年   125篇
  2004年   137篇
  2003年   98篇
  2002年   84篇
  2001年   3篇
  2000年   4篇
  1999年   4篇
  1998年   8篇
  1997年   9篇
  1996年   8篇
  1995年   5篇
  1994年   4篇
  1993年   4篇
  1991年   4篇
  1988年   2篇
  1987年   1篇
  1985年   2篇
  1983年   1篇
  1981年   1篇
  1980年   2篇
  1978年   1篇
排序方式: 共有1822条查询结果,搜索用时 15 毫秒
41.
42.
Deliberately controlled interfacial interactions between incorporated nanofiller particles and host polymer backbone chains constitute a critical element in the realm of polymer nanocomposites with tailorable multifunctional properties. We demonstrate the physicochemical effects induced by graphene nanoplatelets (GNP) of different sizes on the condensation polymerization reaction of aromatic thermosetting copolyester (ATSP) through the formation of electrically conductive percolating networks as enabled by interfacial interactions. Carboxylic acid and acetoxy-capped precursor oligomers of ATSP are solid-state mixed with chemically pristine GNP particles at various loading levels. Upon in situ endothermic condensation polymerization reaction, crosslinked backbone of the ATSP foam matrix is formed while the carbonaceous nanofillers are incorporated into the polymer network via covalent conjugation with functional end-groups of the oligomers. The controlled GNP size promotes different electrical percolation thresholds and ultimate electrical conductivities. Microstructural analysis demonstrates GNP distributions in the matrix as well as morphological modifications induced by the formation of conductive percolating GNP networks. Cure characteristics reveal the thermochemical changes prompted in the polymerization processes for GNP content above the requirement for percolation formation. Chemical spectroscopy of the ATSP nanocomposite morphology exhibits the formation of a robust interfacial coupling mechanism between the GNPs and ATSP backbone. The findings here may guide the developmental efforts of nanocomposites through better identifying roles of the morphology and content of nanofillers in polymerization processes.

Physicochemical effects induced by graphene nanoplatelets on the in situ polycondensation reaction of aromatic thermosetting copolyester through the formation of conductive percolating network assembled via interfacial interactions.  相似文献   
43.
44.
Thrombophilia, the state of increased tendency for blood clotting, is considered the disorder of a complex etiology, caused by both environmental and genetic factors. As gene variants predisposing to thrombophilia and influencing the increased risk of vein thrombosis might influence response to local thrombolysis, the aim of the work was to characterize the pharmacogenetic conditions for local streptokinase treatment in patients with a deep vein thrombosis (DVT) of lower extremities based on the following polymorphism analyses: G1691A polymorphism of factor V (FV), G20210A polymorphism of prothrombin (PT), A4250G (Thr312Ala) polymorphism of fibrinogen-alpha (FGA), G(-455)A polymorphism of fibrinogen-beta (FGB), 4G/5G polymorphism of plasminogen activator inhibitor type 1(PAI-1) and insertion/deletion (I/D) polymorphism of tissue plasminogen activator (t-PA). The study included 40 DVT patients who underwent a local thrombolytic treatment within 14-day period from diagnosis. Full recanalization was achieved in 20 subjects (50%) [group R(+)], whereas incomplete or total lack of recanalization was identified in the remaining 20 patients [group R(-)]. No major complications of thrombolytic treatment occurred in the studied group. In the case of prothrombin gene all individuals carried homozygous wild type genotype (GG). Prevalence of the genotypes and alleles of the remaining five polymorphisms did not differ significantly between the groups R(+) and R(-). Neither sex nor age, smoking or time period from diagnosis to introduction of the thrombolytic treatment significantly influenced treatment efficacy. The results of the study suggest that a local thrombolysis with streptokinase introduced within two week period from the diagnosis is a safe and efficient method of treatment for deep vein thrombosis of lower extremities. However, size of the group is insufficient to clearly determine the association between investigated polymorphisms and efficacy of local treatment with streptokinase.  相似文献   
45.
Background:?Menarcheal age is the most important measure of sexual maturation in girls and a sensitive indicator of environmental conditions during childhood.

Objective:?The study analysed the association between age at menarche and socio-economic characteristics (urbanization, population size, education of parents and number of children in the family).

Subjects and methods:?Questionnaire data were collected from 3271 female schoolchildren born between 1981 and 1984, living in three provinces of southern Poland. Menarcheal age was estimated by the recall method and based on the date of menarche given by the study participants. ANCOVA and multiple regression analyses were applied to test statistical significance of differences between groups.

Results:?Girls from families with high socio-economic status experience menarche at an earlier age than girls from families with lower socio-economic status. However, depending on the geographical region and the population size, other factors influence menarcheal age. In the Krakow province, factors that significantly differentiate age at menarche are urbanization, father's education and number of children in the family; in the Opole province, these factors include urbanization and number of children in the family, while in the Nowy Sacz province, number of children in the family is significant.

Conclusions:?Socio-economic differences are greater in a large urban city (Krakow), and affect variation in age at menarche. However, within smaller populations (Opole, Nowy Sacz) living in towns and villages, the difference in age at menarche is less visible. In addition, variation between areas reveals a lower age at menarche in urban as compared with non-urban areas.

Résumé. Arrière plan: L’âge aux premières règles est une mesure importante de la maturation sexuelle des filles ainsi qu’un indicateur sensible des conditions du milieu au cours de l’enfance.

Objectif: Cette étude analyse l’association entre âge aux premières règles et facteurs socio-économiques (urbanisation, taille de la population, éducation parentale et nombre d’enfants dans la famille).

Sujets et méthodes: Des données par questionnaire ont été rassemblées sur 3271 écoliers habitant dans trois provinces du sud de la Pologne, nés entre 1981 et 1984. L’âge aux premières règles a été estimé par la méthode de mémorisation. Des analyses de régression multiple et de covariance (ANCOVA) ont été effectuées afin d’évaluer la signification statistique des différences entre groupes.

Résultats: Les filles de familles à statut socio-économique élevé sont plus précoces que celles de statut socio-économique défavorable, mais suivant la région et la dimension de la population, d’autres facteurs influencent l’âge aux premières règles. Dans la province de Cracovie, l’urbanisation, l’éducation du père et le nombre d’enfants dans la famille jouent un rôle significatif. Dans la province d’Opole, ce sont l’urbanisation, l’éducation du père et le nombre d’enfants dans la famille qui interviennent, alors que dans la province de Nowi Sacz, est significatif le nombre d’enfants dans la famille.

Conclusions: Les différences socio-économiques sont plus significatives dans une grande ville (Cracovie), alors que dans les ensembles populationnels plus restreints (Opole, Nowy Sacz), elles sont de moindre importance. Par ailleurs, la variation entre régions révèle un âge aux premières règles plus précoce chez les filles urbaines que chez les rurales.

Zusammenfassung. Hintergrund: Das Menarchealter ist das wichtigste Maß für die sexuelle Reife bei Mädchen und ein empfindlicher Indikator für Umweltbedingungen während der Kindheit.

Ziel: Die Studie analysierte die Beziehung zwischen Menarchealter und sozio-ökonomischen Kennzeichen (Urbanisation, Populationsgröße, Schulbildung der Eltern und Anzahl der Kinder pro Familie).

Probanden und Methoden: Mittels Fragebögen wurden Daten von 3271 Schülerinnen, geboren zwischen 1981 und 1984, aus drei Provinzen Südpolens erhoben. Das Menarchealter wurde retrospektiv erfragt und basiert auf Angaben zur Menarche von den Studienteilnehmerinnen. Es wurden ANCOVA und multiple Regressionsanalysen verwendet, um Unterschiede zwischen den Gruppen auf statistische Signifikanz zu testen.

Ergebnisse: Mädchen aus Familien der oberen sozio-ökonomischen Schicht menstruieren früher als Mädchen aus Familien niederer sozio-ökonomischer Schichten. Je nach geographischer Region und Populationsgröße gibt es jedoch noch weitere Faktoren, die das Menarchealter beeinflussten. Faktoren, die in der Provinz Krakau signifikanten Einfluss auf das Menarchealter zeigen, sind Urbanisationsgrad, Schulbildung des Vaters und Anzahl der Kinder in der Familie; in der Provinz Oppeln beinhalten diese Faktoren den Urbanisationsgrad und die Anzahl der Kinder in der Familie, während in der Provinz Novy Sacz nur die Anzahl der Kinder in der Familie Signifikanzniveau erreichen.

Zusammenfassung: Sozio-ökonomische Unterschiede sind in einer Großstadt (Krakau) größer und nehmen Einfluss auf die Variation des Menarchealters. In den weniger umfangreichen Populationen (Oppeln, Novy Sacz) aus kleineren Städten und Dörfern ist dagegen der Unterschied im Menarchealter weniger offensichtlich. Darüber hinaus zeigt die Variation zwischen Regionen, dass das Menarchealter in städtischen Gegenden niedriger ist als in ländlichen.

Resumen. Antecedentes: La edad de menarquia es la medida más importante de la maduración sexual en chicas y un sensible indicador de las condiciones ambientales durante la infancia.

Objetivo: El estudio analizó la asociación entre la edad de menarquia y características socioeconómicas (urbanización, tamaño poblacional, educación de los padres y número de hijos en la familia).

Sujetos y métodos: Los datos del cuestionario se recogieron en 3271 niñas escolares nacidas entre 1981 y 1984, que residían en tres provincias del sur de Polonia. La edad de menarquia se estimó por el método retrospectivo y se basó en la fecha de menarquia proporcionada por las participantes en el estudio. Se aplicaron los análisis ANCOVA y de regresión múltiple para comprobar la significación estadística de las diferencias entre grupos.

Resultados: Las chicas de familias con un nivel socioeconómico elevado experimentan la menarquia a una edad más temprana que las de familias con un nivel socioeconómico bajo. Sin embargo, dependiendo de la región geográfica y del tamaño poblacional, existen otros factores que influyen sobre la edad de menarquia. En la provincia de Cracovia, los factores que producen diferencias significativas en la edad de menarquia son la urbanización, la educación del padre y el número de hijos en la familia; en la provincia de Opole, estos factores incluyen la urbanización y el número de hijos de la familia, mientras que en la provincia de Nowy Sacz, es significativo el número de hijos por familia.

Conclusiones: Las diferencias socioeconómicas son mayores en una gran urbe (Cracovia) y afectan a la variación en la edad de menarquia. Sin embargo, dentro de poblaciones más pequeñas (Opole, Nowy Sacz), viviendo en pueblos y aldeas, la diferencia en la edad de menarquia es menos evidente. Además, la variación entre áreas revela una menor edad de menarquia en el medio urbano comparado con las áreas no urbanas.  相似文献   
46.

To evaluate the impact of a community health worker intervention (CHW) (referred to as Personalized Support for Progress (PSP)) on all-cause health care utilization and cost of care compared with Enhanced Screening and Referral (ESR) among women with depression. A total of 223 patients (111 in PSP and 112 in ESR randomly assigned) from three women’s health clinics with elevated depressive symptoms were enrolled in the study. Their electronic health records were queried to extract all-cause health care encounters along with the corresponding billing information 12 months before and after the intervention, as well as during the first 4-month intervention period. The health care encounters were then grouped into three mutually exclusive categories: high-cost (> US$1000 per encounter), medium-cost (US$201–$999), and low-cost (≤ US$200). A difference-in-difference analysis of mean total charge per patient between PSP and ESR was used to assess cost differences between treatment groups. The results suggest the PSP group was associated with a higher total cost of care at the baseline; taking this baseline difference into account, the PSP group was associated with lower mean total charge amounts (p = 0.008) as well as a reduction in the frequency of high-cost encounters (p < 0.001) relative to the ESR group during the post-intervention period. Patient-centered interventions that address unmet social needs in a high-cost population via CHW may be a cost-effective approach to improve quality of care and patient outcomes.

  相似文献   
47.
48.
IntroductionIn inflammatory bowel diseases (IBD), osteopenia and osteoporosis constitute a significant medical problem. Cytokines, especially IL-17, play an important role in the pathogenesis of IBD and osteoporosis. Vitamin D is a regulator of bone metabolism, and helps maintain immune system homeostasis.Material and methodsThe research sample consisted of 208 persons: 83 patients (age 35 ±11.99 years) with Crohn’s disease (CD); 86 patients (age 39.58 ±14.74 years) with ulcerative colitis (UC); and 39 persons (age 30.74 ±8.63 years) in the control group (CG). Clinical data on bone mineral density of the lumbar spine (L2-L4), bone mineral density of the femoral neck (FN), and body mass index (BMI) were collected. 25OHD and IL-17 serum concentrations were also measured.ResultsBody mass index (kg/m2) results: in CD, 21.51 ±3.68; in UC, 23.31 ±4.38; and in CG, 24.57 ±3.45 (p < 0.01). Densitometry results for L2–L4 T-score SD: in CD –0.83 ±1.45; in UC –0.47 ±1.15; in CG 0.09 ±0.70. Densitometry results for FN T-score SD: in CD –0.62 ±1.26; in UC –0.29±1.17; in CG 0.41 ±1.03 25OHD (ng/ml) serum concentrations: in CD, 21.33±12.50; in UC, 22.04±9.56; in CG, 21.56±9.11 (ns). IL-17 (pg/ml) serum concentrations: in CD, 8.55±10.99; in UC, 11.67±12.97; in CG, 5.16±9.11 (ns).ConclusionsInflammatory bowel diseases patients and persons from the CG did not differ in vitamin D or IL-17 levels. Patients with a mild course of the disease had a higher vitamin D concentration and bone mineral density. In UC, higher vitamin D concentrations were associated with lower IL-17 concentrations. The IBD patients with a severe course of the disease had a lower body mass than those in the CG and the patients with a mild course of the disease.  相似文献   
49.

Objective

To assess the prevalence of pain in the musculoskeletal system and possible reasons for these complaints among early age children from Warsaw schools.

Material and methods

The study was conducted in 34 randomly selected primary schools in Warsaw in 2011. 2748 survey-questionnaires were given to parents or legal guardians by children. Of these, 1509 surveys were subject to a final analysis. The survey included 66 questions regarding, among other things, pain in the musculoskeletal system in children. Additionally, there were questions about possibly occurring diseases, any postural defects, significant obesity, as well as effects of these complaints on the child''s physical activity. Survey data regarded 6–7-year-old children.

Results

In the group of 1509 respondents, 242 children (16%) complained about pain in the musculoskeletal system. Pain was located most frequently in the knee joints, and more rarely in the spine and joints in the upper extremities. In the group of children who complained about pain, moderate physical activity was statistically significantly limited. According to parents, physicians did not diagnose any medical conditions in 106 children. Joint disease was diagnosed in 33 children. Postural defects were diagnosed in 589 children. In 123 children complaining about pain at least one postural defect was diagnosed. Such defects were diagnosed statistically significantly more rarely (p = 0.011) in 1234 children who did not complain about pain (460 children). Platypodia or other foot deformation was observed in 25% of these children, spinal curvature in 12%, abnormal knee joint position in 11% and uneven hip position in 2% children. Of note, 17% of all children were significantly overweight. In overweight children the prevalence of pain, especially in the knee joints and feet, was significantly higher.

Conclusions

This study aims to underline the problem of musculoskeletal pain in early-age children which limits their physical activity. Also the authors draw attention to the issue of postural defects in a large group of school children. This issue undoubtedly requires more attention and a plan how to create more effective methods of prevention.  相似文献   
50.
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