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   12066篇
  免费   776篇
  国内免费   24篇
耳鼻咽喉   75篇
儿科学   436篇
妇产科学   232篇
基础医学   1411篇
口腔科学   157篇
临床医学   1315篇
内科学   2088篇
皮肤病学   149篇
神经病学   1550篇
特种医学   547篇
外科学   2018篇
综合类   125篇
一般理论   22篇
预防医学   1148篇
眼科学   113篇
药学   841篇
中国医学   24篇
肿瘤学   615篇
  2023年   62篇
  2022年   93篇
  2021年   247篇
  2020年   167篇
  2019年   274篇
  2018年   311篇
  2017年   213篇
  2016年   257篇
  2015年   243篇
  2014年   431篇
  2013年   597篇
  2012年   916篇
  2011年   966篇
  2010年   536篇
  2009年   503篇
  2008年   844篇
  2007年   808篇
  2006年   785篇
  2005年   838篇
  2004年   758篇
  2003年   724篇
  2002年   663篇
  2001年   108篇
  2000年   75篇
  1999年   97篇
  1998年   144篇
  1997年   103篇
  1996年   104篇
  1995年   91篇
  1994年   73篇
  1993年   55篇
  1992年   59篇
  1991年   48篇
  1990年   34篇
  1989年   46篇
  1988年   59篇
  1987年   42篇
  1986年   41篇
  1985年   30篇
  1984年   44篇
  1983年   47篇
  1982年   48篇
  1981年   34篇
  1980年   48篇
  1979年   26篇
  1978年   20篇
  1977年   20篇
  1976年   21篇
  1972年   16篇
  1971年   14篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
MDMA (3,4-methylenedioxymethamphetamine) induces thermogenesis in a mitochondrial uncoupling protein 3-dependent manner. There is evidence that this hyperthermia is mediated in part by the lipolytic release of free fatty acids, that subsequently activate uncoupling protein 3 in skeletal muscle mitochondria. We hypothesize that atrial natriuretic peptide (ANP), a strong lipolytic mediator, may contribute to the induction and maintenance of MDMA-induced thermogenesis. The specific aims of this study were to (1) determine if ANP is released following MDMA administration, and (2) use the ANP receptor antagonist, Anantin, to ascertain the role of ANP in MDMA-induced hyperthermia. ANP levels were measured in plasma at baseline, 10, 20, 30 and 60 min following MDMA (40 mg/kg, sc) administration in 16 male Sprague-Dawley rats. A robust increase in ANP was seen within 10 min of MDMA administration. ANP levels returned to baseline at 20 min and then gradually rose over the 60 min monitoring period. The administration of Anantin (40 mg, ip), 15 min before and after MDMA, significantly attenuated the MDMA-induced hyperthermia. We conclude that ANP signaling contributes to the hyperthermia induced by MDMA.  相似文献   
992.
microRNA are small noncoding RNAs that translationally repress their target messenger RNAs. Many microRNAs are expressed at reduced levels in tumors. microRNAs with reduced expression in cancer often regulate oncogenes, resulting in enhanced tumor growth. One therapeutic option is to restore microRNA levels in the tumor to that of the non-diseased tissue. This is possible by delivering microRNA to the tumor in the form of an oligonucleotide mimic or by expressing the microRNA in the cancer using a gene vector. This article surveys the field of oligonucleotide mimics and gene vector approaches to restore microRNA levels in tumors and reviews the literature on experimental and pre-clinical studies that have used these approaches to treat cancer.  相似文献   
993.
994.
The core pathogenic process in the common marmoset model of multiple sclerosis (MS) is the activation of memory-like T cells specific for peptide 34 to 56 derived from the extracellular domain of myelin/oligodendrocyte glycoprotein (MOG34-56). Immunization with MOG34-56 in incomplete Freund’s adjuvant is a sufficient stimulus for in vivo activation of these T cells, together with the induction of MS-like disease and CNS pathology. Ex vivo functional characteristics of MOG34-56 specific T cells are specific cytolysis of peptide pulsed target cells and high IL-17A production. To indentify possible functions in this new model of T helper 1 cells, which play a central pathogenic role in MS models induced with complete Freund’s adjuvant, we tested the effect of human interferon-γ (IFNγ) administration during disease initiation of the disease (day 0–25) and around the time of disease expression (psd 56–81). The results show a clear modulatory effect of early IFNγ treatment on humoral and cellular autoimmune parameters, but no generalized mitigating effect on the disease course. These results argue against a prominent pathogenic role of T helper 1 cells in this new marmoset EAE model.  相似文献   
995.
Min K  Jo H  Song K  Cho M  Chun YS  Jon S  Kim WJ  Ban C 《Biomaterials》2011,32(8):2124-2132
We have designed a dual-aptamer complex specific to both prostate-specific membrane antigens (PSMA) (+) and (-) prostate cancer cells. In the complex, an A10 RNA aptamer targeting PSMA (+) cells and a DUP-1 peptide aptamer specific to PSMA (-) cells were conjugated through streptavidin. Doxorubicin-loaded onto the stem region of the A10 aptamer was delivered not only to PSMA (+) cells but to PSMA (-) cells, and eventually induced apoptosis in both types of prostate cancer cells. Cell death was monitored by measuring guanine concentration in cells using differential pulse voltammetry (DPV), a simple and rapid electrochemical method, and was further confirmed by directly observing cell morphologies cultured on the transparent indium tin oxide (ITO) glass electrode and checking their viabilities using a trypan blue assay. To investigate the in vivo application of the dual-aptamer system, both A10 and DUP-1 aptamers were immobilized on the surface of thermally cross-linked superparamagnetic iron oxide nanoparticles (TCL-SPION). Selective cell uptakes and effective drug delivery action of these probes were verified by Prussian blue staining and trypan blue staining, respectively.  相似文献   
996.

Introduction

Tobacco quitlines (QLs) are efficacious and have assisted many smokers in achieving tobacco abstinence. However, most smokers are not able to achieve tobacco abstinence with QL services. QL counseling interventions for smokers who do not quit on their target quit date (TQD) and decline to set a new TQD after missing their TQD have not been systematically evaluated.

Methods

A telephone survey of tobacco QLs in the United States (US) was conducted to examine systematic approaches used with smokers who do not quit on their TQD and decline to set a new TQD. Tobacco QLs service providers were identified through the North American Quitline Consortium (NAQC).

Results

Fourteen service providers managing QLs of all 50 US states were identified and completed the voluntary survey. All providers recommended setting a new quit TQD if smokers did not achieve smoking cessation by their initial TQD. Six percent of US state QLs used brief motivational interviewing utilizing the “5R's” (relevance, risk, rewards, roadblocks, repetition). However, 90% of QLs had intervention protocols emphasizing smoking rate reduction.

Conclusion

Although some US QLs utilized the “5Rs,” the majority provided smoking reduction interventions for smokers not achieving tobacco cessation by their initial TQD and declining to set a new TQD. Research is needed to evaluate the efficacy of smoking rate reduction methods implemented through QLs for increasing smoking abstinence rates.  相似文献   
997.
The U.S. Environmental Protection Agency (EPA) has instituted the Chemical Safety for Sustainability (CSS) research program for assessing the health and environmental impact of manufactured chemicals. This is a broad program wherein one of the tasks is to develop high throughput screening (HTS) methods and follow-up confirmation for toxicity at realistic environmental exposure levels. The main tools under this task are in vitro toxicity testing, in silico molecular modeling, and in vivo (systemic) measurements documentation. The in vivo research component is intended to support and corroborate in vitro chemical toxicity prioritization with observations of systemic perturbations and statistical parameters derived from intact (living) organisms. Based on EPA's Biomonitoring Framework for human health research, such observations are intended to link environmental exposures to a cascade of biomarker chemicals to help identify and clarify adverse outcome pathways within the context of systems biology. This commentary discusses the issues regarding interpretation of in vitro changes from HTS as an adverse result, an adaptive (non-adverse) response, or a random/irrelevant occurrence. A second goal is to inform in vitro strategies as to relevant dosing (potency) levels at the cellular level that reflect realistic systemic exposures. Although we recognize the high value of in vivo animal toxicity testing, herein we focus on observational (minimally invasive) human biomonitoring methods and propose complementary in vivo testing that could help guide the design of high-throughput analyses and the ultimate interpretation of their outcomes.  相似文献   
998.
999.
Human induced pluripotent stem cells (iPSCs) have become an intriguing approach for neurological disease modeling, because neural lineage-specific cell types that retain the donors’ complex genetics can be established in vitro. The statistical power of these iPSC-based models, however, is dependent on accurate diagnoses of the somatic cell donors; unfortunately, many neurodegenerative diseases are commonly misdiagnosed in live human subjects. Postmortem histopathological examination of a donor's brain, combined with premortem clinical criteria, is often the most robust approach to correctly classify an individual as a disease-specific case or unaffected control. In this study, we describe iPSCs generated from a skin biopsy collected postmortem during the rapid autopsy of a 75-year-old male, whole body donor, defined as an unaffected neurological control by both clinical and histopathological criteria. These iPSCs were established in a feeder-free system by lentiviral transduction of the Yamanaka factors, Oct3/4, Sox2, Klf4, and c-Myc. Selected iPSC clones expressed both nuclear and surface antigens recognized as pluripotency markers of human embryonic stem cells (hESCs) and were able to differentiate in vitro into neurons and glia. Statistical analysis also demonstrated that fibroblast proliferation was significantly affected by biopsy site, but not donor age (within an elderly cohort). These results provide evidence that autopsy donor-derived fibroblasts can be successfully reprogrammed into iPSCs, and may provide an advantageous approach for generating iPSC-based neurological disease models.  相似文献   
1000.

Background

Depression is more likely in patients with chronic physical illness, and is associated with increased rates of disability and mortality. Effective treatment of depression may reduce morbidity and mortality. The use of two stem questions for case finding in diabetes and coronary heart disease is advocated in the Quality and Outcomes Framework, and has become normalised into primary care.

Aim

To define the most effective tool for use in consultations to detect depression in people with chronic physical illness.

Design

Meta-analysis.

Method

The following data sources were searched: CENTRAL, CINAHL, Embase, HMIC, MEDLINE, PsycINFO, Web of Knowledge, from inception to July 2009. Three authors selected studies that examined identification tools and used an interview-based ICD (International Classification of Diseases) or DSM (Diagnostic and statistical Manual of Mental Disorders) diagnosis of depression as reference standard. At least two authors independently extracted study characteristics and outcome data and assessed methodological quality.

Results

A total of 113 studies met the eligibility criteria, providing data on 20 826 participants. It was found that two stem questions, PHQ-9 (Patient Health Questionnaire), the Zung, and GHQ-28 (General Health Questionnaire) were the optimal measures for case identification, but no method was sufficiently accurate to recommend as a definitive case-finding tool. Limitations were the moderate-to-high heterogeneity for most scales and the facts that few studies used ICD diagnoses as the reference standard, and that a variety of methods were used to determine DSM diagnoses.

Conclusion

Assessing both validity and ease of use, the two stem questions are the preferred method. However, clinicians should not rely on the two-questions approach alone, but should be confident to engage in a more detailed clinical assessment of patients who score positively.  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