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   13042篇
  免费   909篇
  国内免费   29篇
耳鼻咽喉   121篇
儿科学   496篇
妇产科学   357篇
基础医学   2000篇
口腔科学   362篇
临床医学   1607篇
内科学   2579篇
皮肤病学   339篇
神经病学   1238篇
特种医学   321篇
外科学   1019篇
综合类   93篇
一般理论   4篇
预防医学   1178篇
眼科学   199篇
药学   823篇
中国医学   15篇
肿瘤学   1229篇
  2024年   11篇
  2023年   99篇
  2022年   155篇
  2021年   295篇
  2020年   275篇
  2019年   328篇
  2018年   319篇
  2017年   284篇
  2016年   334篇
  2015年   427篇
  2014年   519篇
  2013年   710篇
  2012年   1056篇
  2011年   1051篇
  2010年   627篇
  2009年   533篇
  2008年   865篇
  2007年   908篇
  2006年   876篇
  2005年   832篇
  2004年   798篇
  2003年   727篇
  2002年   655篇
  2001年   117篇
  2000年   69篇
  1999年   99篇
  1998年   151篇
  1997年   129篇
  1996年   82篇
  1995年   81篇
  1994年   68篇
  1993年   66篇
  1992年   41篇
  1991年   42篇
  1990年   24篇
  1989年   28篇
  1988年   29篇
  1987年   23篇
  1986年   13篇
  1985年   18篇
  1984年   24篇
  1983年   27篇
  1982年   17篇
  1981年   17篇
  1980年   19篇
  1978年   16篇
  1977年   22篇
  1975年   10篇
  1974年   10篇
  1967年   9篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Alloplastic and xenogeneic bone grafting materials are frequently used for bone augmentation. The effect of these materials on precursor cells for bone augmentation is yet to be determined. The aim of this study was to ascertain, in vitro, how augmentation materials influence the growth rates and viability of human unrestricted somatic stem cells. The biocompatibility of two xenogeneic and one alloplastic bone graft was tested using human unrestricted somatic stem cells (USSCs). Proliferation, growth, survival and attachment of unrestricted somatic stem cells were monitored after 24 h, 48 h and 7 days. Furthermore, cell shape and morphology were evaluated by SEM. Scaffolds were assessed for their physical properties by Micro-CT imaging. USSCs showed distinct proliferation on the different carriers. Greatest proliferation was observed on the xenogeneic carriers along with improved viability of the cells. Pore sizes of the scaffolds varied significantly, with the xenogeneic materials providing greater pore sizes than the synthetic inorganic material. Unrestricted somatic stem cells in combination with a bovine collagenous bone block seem to be very compatible. A scaffold’s surface morphology, pore size and bioactive characteristics influence the proliferation, attachment and viability of USSCs.  相似文献   
52.
BackgroundCardiovascular risk factors and comorbidities are highly prevalent among COVID‐19 patients and are associated with worse outcomes.HypothesisWe therefore investigated if established cardiovascular risk assessment models could efficiently predict adverse outcomes in COVID‐19. Furthermore, we aimed to generate novel risk scores including various cardiovascular parameters for prediction of short‐ and midterm outcomes in COVID‐19.MethodsWe included 441 consecutive patients diagnosed with SARS‐CoV‐2 infection. Patients were followed‐up for 30 days after the hospital admission for all‐cause mortality (ACM), venous/arterial thromboembolism, and mechanical ventilation. We further followed up the patients for post‐COVID‐19 syndrome for 6 months and occurrence of myocarditis, heart failure, acute coronary syndrome (ACS), and rhythm events in a 12‐month follow‐up. Discrimination performance of DAPT, GRACE 2.0, PARIS‐CTE, PREDICT‐STABLE, CHA2‐DS2‐VASc, HAS‐BLED, PARIS‐MB, PRECISE‐DAPT scores for selected endpoints was evaluated by ROC‐analysis.ResultsOut of established risk assessment models, GRACE 2.0 score performed best in predicting combined endpoint and ACM. Risk assessment models including age, cardiovascular risk factors, echocardiographic parameters, and biomarkers, were generated and could successfully predict the combined endpoint, ACM, venous/arterial thromboembolism, need for mechanical ventilation, myocarditis, ACS, heart failure, and rhythm events. Prediction of post‐COVID‐19 syndrome was poor.ConclusionRisk assessment models including age, laboratory parameters, cardiovascular risk factors, and echocardiographic parameters showed good discrimination performance for adverse short‐ and midterm outcomes in COVID‐19 and outweighed discrimination performance of established cardiovascular risk assessment models.  相似文献   
53.
54.
55.
STUDY OBJECTIVE: To evaluate regression rates among adolescents (aged < or =21) with cervical intraepithelial neoplasia (CIN) 2 managed expectantly and to determine factors associated with disease regression. DESIGN: Cohort study using a colposcopic database of 2,996 women seen between August 1999 and November 2005. SETTING: Colposcopy clinic in urban, tertiary care medical center. PARTICIPANTS: Adolescents with CIN 2. Routine management consisted of two options: immediate treatment or repeat colposcopic evaluation in 6 months. MAIN OUTCOME MEASURES: For those managed conservatively, regression was defined either as a subsequent normal colposcopy and/or biopsy and at least 2 smears read as negative for epithelial abnormality or at least 3 consecutive negative smears if repeat colposcopy was not performed. Demographic information, including age, was assessed to determine possible associations with disease regression. RESULTS: Of the 93 adolescents, 53 (57%) elected to undergo immediate treatment with a diagnostic excisional procedure, and 40 (43%) chose management with colposcopic follow-up. Of those treated, high-grade disease (CIN 2+) was found in 40 (75%). Of the 36 young women followed conservatively (4 were lost to follow-up), regression after a median follow-up time of 378 days was documented in 14 (39%). Of the 22 adolescents not fulfilling our criteria for regression, only 3 had evidence of CIN 2 or worse during follow-up. The remaining 19 had either CIN 1 or mildly abnormal cytologic results. Kaplan-Meier survival estimates indicated younger age (< or =16 years) tended to be associated with decreased time to regression. CONCLUSION: Based on significant regression of CIN 2 among adolescent women, primary management in this population should consist of cytologic and colposcopic follow-up.  相似文献   
56.
PURPOSE OF REVIEW: To review publications, published during the past year, that have examined uterine artery Doppler findings in women with adverse pregnancy outcome. RECENT FINDINGS: Almost two-thirds of stillbirths that occur in the early preterm period (up to 32 weeks) can be predicted by uterine artery Doppler at 23 weeks. First trimester screening studies have shown that an abnormal result increases the risk of subsequent fetal growth restriction, and such women are at particularly high risk when indices remain abnormal in the second trimester. Studies combining uterine artery Doppler with maternal serum markers have demonstrated that measurement of first-trimester maternal serum pregnancy-associated plasma protein A and free beta human chorionic gonadotrophin improve sensitivities of second-trimester Doppler. As these are frequently measured in Down syndrome screening and they lend themselves in screening for pre-eclampsia. Women with abnormal first and second-trimester serum markers constitute a high-risk group. Maternal serum placental protein 13 remains a promising method for early screening, although a recent study suggests lower sensitivities than initially reported. SUMMARY: Uterine artery Doppler screening identifies women at high risk for developing adverse pregnancy outcomes. Detection rates may be increased and false positive rates reduced by combination with maternal characteristics or serum markers.  相似文献   
57.
58.
Background: Alongside metabolic diseases (esp. obesity), allergic disorders are becoming increasingly prevalent. Since both obesity and allergies are highly impacted by environmental determinants, with this study we assessed the potential link between metabolic implications and two distinct types of allergies. Methods: Using cross-sectional data from the German FoCus cohort, n = 385 allergy cases, either hay fever (=type I allergy, n = 183) or contact allergy (=type IV allergy, n = 202) were compared to age- and sex-matched healthy control subjects (1:1 ratio, in total n = 770) regarding their metabolic phenotype, diet, physical activity, sleep, gut microbial composition, and serum metabolite profile using suitable BMI-adjusted models. Results: Obesity and metabolic alterations were found significantly more prevalent in subjects with allergies. In fact, this relation was more pronounced in contact allergy than hay fever. Subsequent BMI-adjusted analysis reveals particular importance of co-occurring hyperlipidaemia for both allergy types. For contact allergy, we revealed a strong association to the dietary intake of poly-unsaturated fatty acids, particularly α-linolenic acid, as well as the enrichment of the corresponding metabolic pathway. For hay fever, there were no major associations to the diet but to a lower physical activity level, shorter duration of sleep, and an altered gut microbial composition. Finally, genetic predisposition for hyperlipidaemia was associated to both contact allergy and hay fever. Conclusions: Reflected by higher allergy prevalence, our findings indicate an impaired immune response in obesity and hyperlipidaemia, which is differentially regulated in type I and type IV allergies by an unfavourable lifestyle constellation and subsequent microbial and metabolic dysfunctions.  相似文献   
59.
Traditional medicines play an important role in the provision of health care in many developing countries. Their use is also significant in developed countries, increasing their commercial value. Several 'high-profile' cases of patenting of traditional medicines, without consent from or compensation to their holders, have further focussed attention on their importance. Traditional medicine usually involves biological resources and the knowledge of local and indigenous peoples and/or healers regarding their medicinal use; thus, it is interlinked with biodiversity conservation and indigenous peoples' rights over their knowledge and resources. At this multi-faceted interface, complex ethical questions arise. This article provides an overview and discussion of key issues, dilemmas and challenges. It points to possible modifications and at ways to devise new forms of intellectual property ownership that may better suit the needs of those who seek to protect traditional medicine. Yet it also questions whether such protection, which may restrict access, is the preferred option.While intellectual property protection for traditional medicines has multiple and diverse objectives, the priorities are often not clear and the strategies which could be deployed may interfere with each other, as well as with the prioritization of objectives. This is further aggravated by differences in stakeholders' concepts on ownership of knowledge and by uncertain or paradoxical effects of some potentially useful strategies. Thus, policymakers should address the multiple, multi-layered issues and questions, and try to develop a range of solutions in order to address and balance the various objectives and interests.  相似文献   
60.
Over half the world’s population is at risk for viruses transmitted by Aedes mosquitoes, such as dengue and Zika. The primary vector, Aedes aegypti, thrives in urban environments. Despite decades of effort, cases and geographic range of Aedes-borne viruses (ABVs) continue to expand. Rigorously proven vector control interventions that measure protective efficacy against ABV diseases are limited to Wolbachia in a single trial in Indonesia and do not include any chemical intervention. Spatial repellents, a new option for efficient deployment, are designed to decrease human exposure to ABVs by releasing active ingredients into the air that disrupt mosquito–human contact. A parallel, cluster-randomized controlled trial was conducted in Iquitos, Peru, to quantify the impact of a transfluthrin-based spatial repellent on human ABV infection. From 2,907 households across 26 clusters (13 per arm), 1,578 participants were assessed for seroconversion (primary endpoint) by survival analysis. Incidence of acute disease was calculated among 16,683 participants (secondary endpoint). Adult mosquito collections were conducted to compare Ae. aegypti abundance, blood-fed rate, and parity status through mixed-effect difference-in-difference analyses. The spatial repellent significantly reduced ABV infection by 34.1% (one-sided 95% CI lower limit, 6.9%; one-sided P value = 0.0236, z = 1.98). Aedes aegypti abundance and blood-fed rates were significantly reduced by 28.6 (95% CI 24.1%, ∞); z = −9.11) and 12.4% (95% CI 4.2%, ∞); z = −2.43), respectively. Our trial provides conclusive statistical evidence from an appropriately powered, preplanned cluster-randomized controlled clinical trial of the impact of a chemical intervention, in this case a spatial repellent, to reduce the risk of ABV transmission compared to a placebo.

Aedes-borne viral diseases (ABVDs) [e.g., dengue (DENV), chikungunya, Zika (ZIKV), and yellow fever] are devastating, expanding global public health threats that disproportionally affect low- and middle-income countries. DENV, one of the most rapidly increasing vector-borne infectious diseases, results in ∼400 million infections each year (1, 2), with 4 billion people at risk for infection annually (3). Currently, the primary means for ABVD prevention is controlling the primary mosquito vector, Aedes aegypti. Existing vector control interventions, however, have failed to prevent ABV transmission and epidemics (46).There is an urgent need to develop evidence-based guidance for the use of new and existing ABV vector control tools. The evidence base for vector control against ABVs is weak, despite considerable government investments in World Health Organization (WHO)-recommended control of larval habitats (larviciding, container removal) and ultra-low-volume insecticide spraying (4, 5, 79). These strategies continue to be implemented despite the lack of rigorously generated data from controlled clinical trials demonstrating they reduce ABV infection or disease (6). The only ABV intervention with a proven epidemiological impact in a cluster-randomized control trial (cRCT) assessed community mobilization to reduce mosquito larval habitats (10). A recent test-negative trial with Wolbachia-infected mosquitoes reported a significant reduction of DENV illness in Indonesia (11).Spatial repellents (SRs) are devices that contain volatile active ingredients that disperse in air. The active ingredients can repel mosquitoes from entering a treated space, inhibit attraction to human host cues, or disrupt mosquito biting and blood-feeding behavior and, thus, interfere with mosquito–human contact (1214). Any of these outcomes reduce the probability of pathogen transmission. Pyrethroid-based SRs have shown efficacy in reducing malaria infections in China (15) and Indonesia (16). There have, however, been no clinical trials evaluating the protective efficacy (PE) of SRs against ABV infection or disease.To generate evidence for public health consideration, we conducted a double-blinded, parallel cRCT to demonstrate and quantify the PE of a transfluthrin-based SR to reduce ABV infection incidence over 2 y in a human cohort in Iquitos, Peru.  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