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   1230篇
  免费   88篇
  国内免费   2篇
耳鼻咽喉   12篇
儿科学   27篇
妇产科学   4篇
基础医学   206篇
口腔科学   27篇
临床医学   107篇
内科学   268篇
皮肤病学   30篇
神经病学   198篇
特种医学   56篇
外科学   124篇
综合类   8篇
预防医学   94篇
眼科学   7篇
药学   74篇
中国医学   6篇
肿瘤学   72篇
  2023年   9篇
  2022年   24篇
  2021年   33篇
  2020年   30篇
  2019年   29篇
  2018年   19篇
  2017年   20篇
  2016年   32篇
  2015年   35篇
  2014年   31篇
  2013年   46篇
  2012年   64篇
  2011年   63篇
  2010年   40篇
  2009年   48篇
  2008年   79篇
  2007年   80篇
  2006年   82篇
  2005年   66篇
  2004年   63篇
  2003年   78篇
  2002年   72篇
  2001年   21篇
  2000年   33篇
  1999年   29篇
  1998年   25篇
  1997年   10篇
  1996年   10篇
  1995年   20篇
  1994年   8篇
  1993年   7篇
  1992年   7篇
  1991年   15篇
  1990年   8篇
  1989年   5篇
  1988年   3篇
  1987年   6篇
  1986年   10篇
  1985年   3篇
  1984年   7篇
  1983年   4篇
  1982年   3篇
  1981年   3篇
  1979年   4篇
  1978年   5篇
  1969年   3篇
  1961年   2篇
  1939年   2篇
  1937年   2篇
  1884年   2篇
排序方式: 共有1320条查询结果,搜索用时 15 毫秒
21.
Allergic rhinitis (AR) is impacted by allergens and air pollution but interactions between air pollution, sleep and allergic diseases are insufficiently understood. POLLAR (Impact of air POLLution on sleep, Asthma and Rhinitis) is a project of the European Institute of Innovation and Technology (EIT Health). It will use a freely-existing application for AR monitoring that has been tested in 23 countries (the Allergy Diary, iOS and Android, 17,000 users, TLR8). The Allergy Diary will be combined with a new tool allowing queries on allergen, pollen (TLR2), sleep quality and disorders (TRL2) as well as existing longitudinal and geolocalized pollution data. Machine learning will be used to assess the relationship between air pollution, sleep and AR comparing polluted and non-polluted areas in 6 EU countries. Data generated in 2018 will be confirmed in 2019 and extended by the individual prospective assessment of pollution (portable sensor, TLR7) in AR. Sleep apnea patients will be used as a demonstrator of sleep disorder that can be modulated in terms of symptoms and severity by air pollution and AR. The geographic information system GIS will map the results. Consequences on quality of life (EQ-5D), asthma, school, work and sleep will be monitored and disseminated towards the population. The impacts of POLLAR will be (1) to propose novel care pathways integrating pollution, sleep and patients’ literacy, (2) to study sleep consequences of pollution and its impact on frequent chronic diseases, (3) to improve work productivity, (4) to propose the basis for a sentinel network at the EU level for pollution and allergy, (5) to assess the societal implications of the interaction. MASK paper N°32.  相似文献   
22.
23.
Objective: To describe the designs and methods used in published Australian health promotion evaluation articles between 1992 and 2011. Methods: Using a content analysis approach, we reviewed 157 articles to analyse patterns and trends in designs and methods in Australian health promotion evaluation articles. The purpose was to provide empirical evidence about the types of designs and methods used. Results: The most common type of evaluation conducted was impact evaluation. Quantitative designs were used exclusively in more than half of the articles analysed. Almost half the evaluations utilised only one data collection method. Surveys were the most common data collection method used. Few articles referred explicitly to an intended evaluation outcome or benefit and references to published evaluation models or frameworks were rare. Conclusion: This is the first time Australian‐published health promotion evaluation articles have been empirically investigated in relation to designs and methods. There appears to be little change in the purposes, overall designs and methods of published evaluations since 1992. Implications: More methodologically transparent and sophisticated published evaluation articles might be instructional, and even motivational, for improving evaluation practice and result in better public health interventions and outcomes.  相似文献   
24.
Schnyder corneal dystrophy (SCD) is an autosomal dominant disease characterized by germline variants in UBIAD1 introducing missense alterations leading to deposition of cholesterol in the cornea, progressive opacification, and loss of visual acuity. UBIAD1 was recently shown to synthesize menaquinone‐4 (MK‐4, vitamin K2), but causal mechanisms of SCD are unknown. We report a novel c.864G>A UBIAD1 mutation altering glycine 177 to glutamic acid (p.G177E) in six SCD families, including four families from Finland who share a likely founder mutation. We observed reduced MK‐4 synthesis by UBIAD1 altered by SCD mutations p.N102S, p.G177R/E, and p.D112N, and molecular models showed p.G177‐mutant UBIAD1 disrupted transmembrane helices and active site residues. We show UBIAD1 interacts with HMGCR and SOAT1, enzymes catalyzing cholesterol synthesis and storage, respectively, using yeast two‐hybrid screening and immunoprecipitation. Docking simulations indicate cholesterol binds to UBIAD1 in the substrate‐binding cleft and substrate‐binding overlaps with GGPP binding, an MK‐4 substrate, suggesting potential competition between these metabolites. Impaired MK‐4 synthesis is a biochemical defect identified in SCD suggesting UBIAD1 links vitamin K and cholesterol metabolism through physical contact between enzymes and metabolites. Our data suggest a role for endogenous MK‐4 in maintaining cornea health and visual acuity.  相似文献   
25.
Background: In severe acute coronary syndromes (ACS) elevation of markers of inflammation and acute phase reaction (APR) like C-reactive protein (CRP) as well as a release of troponin have been reported.Using a high sensitivity troponin T (TnT) test we investigated whether an APR occurs in ACS only in the presence of ischemic myocardial damage. Methods: In 85 patients with ACS C-reactive protein (CRP), serum amyloid A (SAA), fibrinogen, thrombin antithrombin III complexes (TAT) and kallikrein were determined vs. high sensitive TnT (0.02 ng/ml) initially and 2 d later vs. 45 patients with stable angina pectoris and 42 controls. Results: In stable angina pectoris, markers of inflammation and coagulation were slightly elevated (p < 0.05). Initially in ACS elevations of CRP to 1.2 ± 0.3 mg/dl, SAA to 4.8 ± 2.6 mg/dl and fibrinogen to 448 ± 21 mg/dl (all p < 0.01 vs. controls) were found followed by a significant APR (p < 0.01).In the subgroup of TnT positive ACS patients, an APR with increased CRP (4.1 ± 1.3 mg/dl), SAA (20.4 ± 8.3 mg/dl), and fibrinogen (641 ± 45 mg/dl) was detectable (all p < 0.05 vs. TnT negative patients). In contrast, patients without TnT release showed APR markers comparable to patients with stable angina pectoris. Conclusion: Our findings demonstrate an association between myocardial injury in ACS and acute phase reaction as evidenced by several molecular markers. A highly sensitive TnT-test identified myocardial inury in about all patients with APR while a standard TnT cut-off (0.1 ng/ml) missed 32% of these patients. Thus, the APR in patients with ACS is strongly associated with at least minor ischemic myocardial damage and prior findings of an APR independent from myocardial injury are probably based on less sensitive troponin tests.  相似文献   
26.
Summary Aggressive chemotherapy of advanced myelodysplastic syndrome (MDS), acute myeloid leukemia (AML) evolving from MDS, subacute AML and secondary AML has usually been associated with low complete remission (CR) rates, a high incidence of early death, and low disease-free survival. We therefore have initiated a phase-III trial of aggressive chemotherapy consisting of idarubicin, cytosine arabinoside, and VP-16 to improve the CR rate. Each chemotherapy cycle is followed by G-CSF to accelerate neutrophil recovery and to reduce the incidence of infections. Until now, 19 patients with high-risk AML have been entered. The CR rate is 47%, with only one death during induction. Patients achieving CR are randomized to receive either high-dose or low-dose interleukin-2 to eliminate residual leukemic cells and to prolong the duration of remission.Presented at the annual meeting of the German Society for Hematology and Oncology, 4–7 October 1992, Berlin  相似文献   
27.

Background

Point of care ultrasound (POCUS) is a useful diagnostic tool in medicine. POCUS provides an easy and reproducible method of diagnosis where conventional radiologic studies are unavailable. Telemedicine is also a great means of communication between educators and students throughout the world.

Hypothesis

Implementing POCUS with didactics and hands-on training, using portable ultrasound devices followed by telecommunication training, will impact the differential diagnosis and patient management in a rural community outside the United States.

Materials and methods

This is an observational prospective study implementing POCUS in Las Salinas, a small village in rural western Nicaragua. Ultrasound was used to confirm a diagnosis based on clinical exam, or uncover a new, previously unknown diagnosis. The primary endpoint was a change in patient management. International sonographic instructors conducted didactic and practical training of local practitioners in POCUS, subsequently followed by remote guidance and telecommunication for 3 months.

Results

A total of 132 patients underwent ultrasound examination. The most common presentation was for a prenatal exam (23.5 %), followed by abdominal pain (17 %). Of the 132 patients, 69 (52 %) were found to have a new diagnosis. Excluding pregnancy, 67 patients of 101 (66 %) were found to have a new diagnosis. A change in management occurred in a total of 64 (48 %) patients, and 62 (61 %) after excluding pregnancy.

Conclusion

Implementing POCUS in rural Nicaragua led to a change in management in about half of the patients examined. With the appropriate training of clinicians, POCUS combined with telemedicine can positively impact patient care.  相似文献   
28.

Background

Clinical reasoning is based on the declarative and procedural knowledge of workflows in clinical medicine. Educational approaches such as problem-based learning or mannequin simulators support learning of procedural knowledge. Immersive patient simulators (IPSs) go one step further as they allow an illusionary immersion into a synthetic world. Students can freely navigate an avatar through a three-dimensional environment, interact with the virtual surroundings, and treat virtual patients. By playful learning with IPS, medical workflows can be repetitively trained and internalized. As there are only a few university-driven IPS with a profound amount of medical knowledge available, we developed a university-based IPS framework. Our simulator is free to use and combines a high degree of immersion with in-depth medical content. By adding disease-specific content modules, the simulator framework can be expanded depending on the curricular demands. However, these new educational tools compete with the traditional teaching

Objective

It was our aim to develop an educational content module that teaches clinical and therapeutic workflows in surgical oncology. Furthermore, we wanted to examine how the use of this module affects student performance.

Methods

The new module was based on the declarative and procedural learning targets of the official German medical examination regulations. The module was added to our custom-made IPS named ALICE (Artificial Learning Interface for Clinical Education). ALICE was evaluated on 62 third-year students.

Results

Students showed a high degree of motivation when using the simulator as most of them had fun using it. ALICE showed positive impact on clinical reasoning as there was a significant improvement in determining the correct therapy after using the simulator. ALICE positively impacted the rise in declarative knowledge as there was improvement in answering multiple-choice questions before and after simulator use.

Conclusions

ALICE has a positive effect on knowledge gain and raises students’ motivation. It is a suitable tool for supporting clinical education in the blended learning context.  相似文献   
29.
Complexation of biomacromolecules (e.g., nucleic acids, proteins, or viruses) with surfactants containing flexible alkyl tails, followed by dehydration, is shown to be a simple generic method for the production of thermotropic liquid crystals. The anhydrous smectic phases that result exhibit biomacromolecular sublayers intercalated between aliphatic hydrocarbon sublayers at or near room temperature. Both this and low transition temperatures to other phases enable the study and application of thermotropic liquid crystal phase behavior without thermal degradation of the biomolecular components.Liquid crystals (LCs) play an important role in biology because their essential characteristic, the combination of order and mobility, is a basic requirement for self-organization and structure formation in living systems (13). Thus, it is not surprising that the study of LCs emerged as a scientific discipline in part from biology and from the study of myelin figures, lipids, and cell membranes (4). These and the LC phases formed from many other biomolecules, including nucleic acids (5, 6), proteins (7, 8), and viruses (9, 10), are classified as lyotropic, the general term applied to LC structures formed in water and stabilized by the distinctly biological theme of amphiphilic partitioning of hydrophilic and hydrophobic molecular components into separate domains. However, the principal thrust and achievement of the study of LCs has been in the science and application of thermotropic materials, structures, and phases in which molecules that are only weakly amphiphilic exhibit LC ordering by virtue of their steric molecular shape, flexibility, and/or weak intermolecular interactions [e.g., van der Waals and dipolar forces (11)]. These characteristics enable thermotropic LCs (TLCs) to adopt a wide variety of exotic phases and to exhibit dramatic and useful responses to external forces, including, for example, the electro-optic effects that have led to LC displays and the portable computing revolution. This general distinction between lyotropic LCs and TLCs suggests there may be interesting possibilities in the development of biomolecular or bioinspired LC systems in which the importance of amphiphilicity is reduced and the LC phases obtained are more thermotropic in nature. Such biological TLC materials are very appealing for several reasons. Most biomacromolecules were extensively characterized in aqueous environments, but in TLC phases, their solvent-free properties and functions could be investigated in a state in which no or only traces of water are present. Water exhibits a high dielectric constant and has the ability to form hydrogen bonds, greatly influencing the structure and functions of biomacromolecules or compromising electronic properties such as charge transport (1215). Indeed, anhydrous TLC systems containing glycolipids (1619), ferritin (20), and polylysine have been reported (2123). However, a general approach to fabricating TLCs based on nucleic acids, polypeptides, proteins, and protein assemblies of large molecular weights such as virus particles remains elusive.Here we propose that the combination of biomaterials with suitably chosen surfactants, followed by dehydration, can be effectively applied as a simple generic scheme for producing biomacromolecular-based TLCs. We demonstrate that biological TLCs can be made from a remarkable range of biomolecules and bio-inspired molecules, including nucleic acids, polypeptides, fusion proteins, and viruses. TLC materials typically combine rigid or semirigid anisometric units, which introduce orientational anisotropy, with flexible alkyl chains, which suppress crystallization (24). In the present experiments, negatively charged biomolecules and bio-inspired molecules act as rigid parts, and cationic surfactants make up the flexible units to produce TLC phases with remarkably low LC-isotropic clearing temperatures, which is another TLC signature. Electrostatic interactions couple these rigid and flexible components into hybrid assemblies, which then order into lamellar phases of alternating rigid and flexible layers (Fig. 1) stabilized by the tendency in TLCs for rigid and flexible to spatially segregate (25).Open in a separate windowFig. 1.Proposed structures of TLCs formed by the biological building blocks complexed with surfactants, showing sketches of various lamellar phases and the corresponding phase transition temperatures (°C). The lamellar bilayer structures are made of, alternately, a sublayer of the biomacromolecules and an interdigitated sublayer of the surfactants, where the negatively charged parts of the biomolecules (e.g., phosphate groups of ssDNA and ssRNA, glutamate residues of supercharged ELPs, and N-terminal glutamate and aspartate residues of pVIII protein in phages) electrostatically interact with the cationic head groups of the surfactants. For the ssDNA–DOAB and ssRNA–DOAB smectic TLCs, the oligonucleotides are randomly orientated in the DNA (RNA) sublayers. For the ELP–DDAB complexes, in addition to the bilayer smectic phase, a modulated smectic (Smmod) phase is observed at lower temperature. For the phage–DOAB–DDAB lamellar structures, rodlike virus particles are embedded in a sublayer between interdigitated surfactants with additional in-plane orientational order.  相似文献   
30.
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