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   21101篇
  免费   1330篇
  国内免费   209篇
耳鼻咽喉   174篇
儿科学   363篇
妇产科学   360篇
基础医学   3033篇
口腔科学   696篇
临床医学   1915篇
内科学   5520篇
皮肤病学   254篇
神经病学   2163篇
特种医学   781篇
外科学   3106篇
综合类   67篇
一般理论   3篇
预防医学   1053篇
眼科学   260篇
药学   1672篇
中国医学   71篇
肿瘤学   1149篇
  2023年   123篇
  2022年   290篇
  2021年   596篇
  2020年   408篇
  2019年   527篇
  2018年   652篇
  2017年   472篇
  2016年   550篇
  2015年   620篇
  2014年   813篇
  2013年   1000篇
  2012年   1595篇
  2011年   1635篇
  2010年   897篇
  2009年   811篇
  2008年   1294篇
  2007年   1375篇
  2006年   1204篇
  2005年   1272篇
  2004年   1158篇
  2003年   1030篇
  2002年   977篇
  2001年   255篇
  2000年   243篇
  1999年   255篇
  1998年   230篇
  1997年   159篇
  1996年   119篇
  1995年   124篇
  1994年   110篇
  1993年   105篇
  1992年   165篇
  1991年   113篇
  1990年   106篇
  1989年   82篇
  1988年   90篇
  1987年   82篇
  1986年   84篇
  1985年   60篇
  1984年   59篇
  1983年   45篇
  1982年   39篇
  1981年   38篇
  1980年   36篇
  1979年   24篇
  1978年   24篇
  1973年   25篇
  1970年   24篇
  1925年   23篇
  1922年   22篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Intratumor heterogeneity is a main cause of the dismal prognosis of glioblastoma (GBM). Yet, there remains a lack of a uniform assessment of the degree of heterogeneity. With a multiscale approach, we addressed the hypothesis that intratumor heterogeneity exists on different levels comprising traditional regional analyses, but also innovative methods including computer-assisted analysis of tumor morphology combined with epigenomic data. With this aim, 157 biopsies of 37 patients with therapy-naive IDH-wildtype GBM were analyzed regarding the intratumor variance of protein expression of glial marker GFAP, microglia marker Iba1 and proliferation marker Mib1. Hematoxylin and eosin stained slides were evaluated for tumor vascularization. For the estimation of pixel intensity and nuclear profiling, automated analysis was used. Additionally, DNA methylation profiling was conducted separately for the single biopsies. Scoring systems were established to integrate several parameters into one score for the four examined modalities of heterogeneity (regional, cellular, pixel-level and epigenomic). As a result, we could show that heterogeneity was detected in all four modalities. Furthermore, for the regional, cellular and epigenomic level, we confirmed the results of earlier studies stating that a higher degree of heterogeneity is associated with poorer overall survival. To integrate all modalities into one score, we designed a predictor of longer survival, which showed a highly significant separation regarding the OS. In conclusion, multiscale intratumor heterogeneity exists in glioblastoma and its degree has an impact on overall survival. In future studies, the implementation of a broadly feasible heterogeneity index should be considered.  相似文献   
2.
3.
The present study aimed at measuring seropositivities for infection by Ascaris suum and Toxocara canis using the excretory/secretory (E/S) antigens from Ascaris suum (AES) and Toxocara canis (TES) within an indigenous population. In addition, quantification of cytokine expressions in peripheral blood cells was determined. A total of 50 Warao indigenous were included; of which 43 were adults and seven children. In adults, 44.1% were seropositive for both parasites; whereas children had only seropositivity to one or the other helminth. For ascariosis, the percentage of AES seropositivity in adults and children was high; 23.3% and 57.1%, respectively. While that for toxocariosis, the percentage of TES seropositivity in adults and children was low; 9.3% and 14.3%, respectively. The percentage of seronegativity was comparable for AES and TES antigens in adults (27.9%) and children (28.6%). When positive sera were analyzed by Western blotting technique using AES antigens; three bands of 97.2, 193.6 and 200.2 kDas were mostly recognized. When the TES antigens were used, nine major bands were mostly identified; 47.4, 52.2, 84.9, 98.2, 119.1, 131.3, 175.6, 184.4 and 193.6 kDas. Stool examinations showed that Blastocystis hominis, Hymenolepis nana and Entamoeba coli were the most commonly observed intestinal parasites. Quantification of cytokines IFN-γ, IL-2, IL-6, TGF-β, TNF-α, IL-10 and IL-4 expressions showed that there was only a significant increased expression of IL-4 in indigenous with TES seropositivity (p < 0.002). Ascaris and Toxocara seropositivity was prevalent among Warao indigenous.  相似文献   
4.
5.
6.
Background:Workplace hazards are a significant source of health impairment for workers and of financial losses for firms. EU directives on workers’ health and safety standards significantly contributed to reduce reported occupational injuries, yet the incidence and prevalence of work-related mental illness is still very high.Objectives:We investigated the association between work-related hazards and individuals’ perceived mental health. We reviewed the existing evidence on the channels through which task-related factors, adverse agents and psychosocial factors are expected to affect workers’ health, with specific regard to mental health.Methods:We used data from the fifth wave of the European Working Conditions Survey, covering over 40,000 face-to-face interviews with workers in 34 countries, which includes information on socio-demographic characteristics, firms and jobs attributes, employment status, as well as working conditions and health status. We carried out an empirical analysis with multivariate regression models in order to estimate the relationship between workers’ mental health problems and workplace risk factors.Results:21,020 interviews were used in the multivariate analysis. We found strong correlations between hazards and various indicators of mental health. Among hazardous agents, low temperatures (β=0.0287) and contact with infectious materials (β=0.0394) were positively associated with mental health outcomes. Among task/sequence-related factors, tiring or painful positions (β=0.0713), repetitive hand/arm movements (β=0.0255), working with VDUs (β=0.0301), repetitive tasks <10 min (β=0.0859) and working in evenings (β=0.00754) were positively associated with mental health. Various psychosocial risk factors related to both the content of the job (for example, frequent disruptive interruptions: β=0.219, working in free time: β=0.0759, poor work-life balance: β=0.228) as well as the job context (for example, bad employment prospects: β=0.177, low decisional autonomy: β=0.245, bad social relations: β=0.186, workplace violence: β=0.411) were positively associated with mental health. The main results of the decomposition show that an important contribution to workers’ overall mental distress at work is associated with psychosocial risk factors (up to 60% for depression/anxiety symptoms and sleep disorders), while the contribution of somatic factors is on average lower (up to 20% for overall fatigue).Conclusions:We argue that action is needed to improve workers’ mental well-being, and reduce the economic costs for both the national health system and employers. Regulations and traditional economic measures are unlikely to prove successful in providing adequate standards of primary and secondary preventive measures in the work place without an appropriate and reliable Risk Assessment Procedure.Key words: Work hazards, risk assessment, job content, mental health  相似文献   
7.
8.
The recognition that neurogenesis does not stop with adolescence has spun off research towards the reduction of brain disorders by enhancing brain regeneration. Adult neurogenesis is one of the tougher problems of developmental biology as it requires the generation of complex intracellular and pericellular anatomies, amidst the danger of neuroinflammation. We here review how a multitude of regulatory pathways optimized for early neurogenesis has to be revamped into a new choreography of time dependencies. Distinct pathways need to be regulated, ranging from neural growth factor induced differentiation to mitochondrial bioenergetics, reactive oxygen metabolism, and apoptosis. Requiring much Gibbs energy consumption, brain depends on aerobic energy metabolism, hence on mitochondrial activity. Mitochondrial fission and fusion, movement and perhaps even mitoptosis, thereby come into play. All these network processes are interlinked and involve a plethora of molecules. We recommend a deep thinking approach to adult neurobiology.  相似文献   
9.
Magnetic resonance elastography aims to non-invasively and remotely characterize the mechanical properties of living tissues. To quantitatively and regionally map the shear viscoelastic moduli in vivo, the technique must achieve proper mechanical excitation throughout the targeted tissues. Although it is straightforward, ante manibus, in close organs such as the liver or the breast, which practitioners clinically palpate already, it is somewhat fortunately highly challenging to trick the natural protective barriers of remote organs such as the brain. So far, mechanical waves have been induced in the latter by shaking the surrounding cranial bones. Here, the skull was circumvented by guiding pressure waves inside the subject's buccal cavity so mechanical waves could propagate from within through the brainstem up to the brain. Repeatable, reproducible and robust displacement fields were recorded in phantoms and in vivo by magnetic resonance elastography with guided pressure waves such that quantitative mechanical outcomes were extracted in the human brain.  相似文献   
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