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   26948篇
  免费   2357篇
  国内免费   494篇
耳鼻咽喉   270篇
儿科学   380篇
妇产科学   236篇
基础医学   2387篇
口腔科学   481篇
临床医学   3539篇
内科学   2918篇
皮肤病学   175篇
神经病学   1928篇
特种医学   1592篇
外国民族医学   4篇
外科学   2988篇
综合类   4131篇
现状与发展   1篇
一般理论   2篇
预防医学   2736篇
眼科学   543篇
药学   3140篇
  39篇
中国医学   1120篇
肿瘤学   1189篇
  2024年   66篇
  2023年   369篇
  2022年   620篇
  2021年   1036篇
  2020年   1008篇
  2019年   918篇
  2018年   968篇
  2017年   959篇
  2016年   853篇
  2015年   979篇
  2014年   1868篇
  2013年   1845篇
  2012年   1694篇
  2011年   1773篇
  2010年   1595篇
  2009年   1333篇
  2008年   1281篇
  2007年   1362篇
  2006年   1278篇
  2005年   950篇
  2004年   911篇
  2003年   795篇
  2002年   735篇
  2001年   507篇
  2000年   428篇
  1999年   413篇
  1998年   326篇
  1997年   282篇
  1996年   245篇
  1995年   220篇
  1994年   217篇
  1993年   154篇
  1992年   147篇
  1991年   150篇
  1990年   152篇
  1989年   141篇
  1988年   126篇
  1987年   113篇
  1986年   104篇
  1985年   136篇
  1984年   119篇
  1983年   99篇
  1982年   87篇
  1981年   103篇
  1980年   80篇
  1979年   53篇
  1978年   40篇
  1977年   32篇
  1976年   37篇
  1975年   19篇
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
21.
22.
23.

Purpose

The objective of the study was to define factors associated with adolescent and young adult (AYA) experiences with private time and having discussed confidentiality and the impact of these experiences on improving delivery of clinical preventive services.

Methods

In 2016, a nationally representative sample of 1,918 US AYAs (13- to 26-year-olds) was surveyed. Survey questionnaire domains were based on prior research and Fishers' information-motivation-behavior skills conceptual model. Data were weighted to represent US households with AYA and analyzed to identify factors independently associated with ever experiencing private time and discussions of confidentiality with a regular health-care provider (HCP). We examined the association of these experiences on AYA attitudes about health care.

Results

Fifty-five percent of female and 49% of male AYA reported ever having had private time with an HCP and 55% of female and 44% of male AYA had spoken to an HCP about confidentiality. Independent predictors of having experienced private time and confidentiality included older age, race, higher household income, gender of the provider, amount of years with the provider, and involvement in risk behaviors. AYA who had experienced private time and confidentiality discussions had more positive attitudes about their providers, were more willing and comfortable discussing sensitive topics, and thought that these discussions should happen at younger ages.

Conclusions

Although confidentiality and private time are important to AYA, many are not experiencing these components of care. Providing private time and discussions of confidentiality can improve the delivery of health care for young people by enhancing positive youth attitudes about preventive care.  相似文献   
24.
25.
《中国现代医生》2020,58(32):28-30+封三
探讨真菌性、细菌性和病毒性肺炎的若干凝血指标差异性研究。方法 回顾性分析2017 年7 月~2019 年11 月本院肺炎患者128 例与同期门诊健康体检者50 例,分析患者血浆纤维蛋白原(FIB)、凝血酶原时间(PT)和活化部分凝血酶时间(APTT)的水平。结果 三类肺炎组与对照组在FIB、PT 和APTT 水平比较,差异均有统计学意义(P<0.01);FIB、PT 水平与病原感染呈正相关,APTT 与病原感染呈负相关。结论FIB、PT、APTT 可以间接提示肺炎感染病原体类型,具有临床意义。  相似文献   
26.
《Clinical neurophysiology》2020,131(1):213-224
ObjectiveSystematically review the abnormalities in event related potential (ERP) recorded in Rett Syndrome (RTT) patients and animals in search of translational biomarkers of deficits related to the particular neurophysiological processes of known genetic origin (MECP2 mutations).MethodsPubmed, ISI Web of Knowledge and BIORXIV were searched for the relevant articles according to PRISMA standards.ResultsERP components are generally delayed across all sensory modalities both in RTT patients and its animal model, while findings on ERPs amplitude strongly depend on stimulus properties and presentation rate. Studies on RTT animal models uncovered the abnormalities in the excitatory and inhibitory transmission as critical mechanisms underlying the ERPs changes, but showed that even similar ERP alterations in auditory and visual domains have a diverse neural basis. A range of novel approaches has been developed in animal studies bringing along the meaningful neurophysiological interpretation of ERP measures in RTT patients.ConclusionsWhile there is a clear evidence for sensory ERPs abnormalities in RTT, to further advance the field there is a need in a large-scale ERP studies with the functionally-relevant experimental paradigms.SignificanceThe review provides insights into domain-specific neural basis of the ERP abnormalities and promotes clinical application of the ERP measures as the non-invasive functional biomarkers of RTT pathophysiology.  相似文献   
27.
The presented case reports on successful treatment with everolimus in a neonate with left ventricular giant rhabdomyoma. The authors used a different dosage regime compared to literature and documented rapid tumor regression by 3D echocardiography.  相似文献   
28.
PurposeTo investigate if high-frequency irreversible electroporation (H-FIRE) treatments can be delivered at higher voltages and with greater energy delivery rates than currently implemented in clinical irreversible electroporation protocols.Materials and MethodsTreatments using 3,000 V and 5,000 V were administered to mechanically perfused ex vivo porcine liver via a single applicator and grounding pad (A+GP) as well as a 4-applicator array (4AA). Integrated energized times (IET) 0.01–0.08 seconds and energy delivery rates 25–300 μs/s were investigated. Organs were preserved at 4°C for 10–15 hours before sectioning and gross analysis using a metabolic stain to identify the size and shape of ablation zones.ResultsA+GP ablations measured between 1.6 cm and 2.2 cm, which did not increase when IET was increased from 0.02 seconds to 0.08 seconds (P > .055; range, 1.9–2.1 cm). Changes in tissue color and texture consistent with thermal damage were observed for treatments with energy delivery rates 50–300 μs/s, but not for treatments delivered at 25 μs/s. Use of the 4AA with a 3-cm applicator spacing resulted in ablations measuring 4.4–4.9 cm with energy delivery times of 7–80 minutes.ConclusionsH-FIRE treatments can rapidly and reproducibly create 2-cm ablations using an A+GP configuration. Treatments without thermal injury were produced at the expense of extended treatment times. More rapid treatments resulted in ablations with varying degrees of thermal injury within the H-FIRE ablation zone. Production of 4-cm ablations is possible using a 4AA.  相似文献   
29.
Study objectivesTo analyze the association between sleep-related symptoms and sleep length in parents and their children in relation to other risk factors in both generations.MethodThe participants were parents (n = 5,855, age 54.3 ± 6.5 years, 45.2% men) who participated in the community-based Respiratory Health in Northern Europe (RHINE) study and one random member of their adult offspring (n = 5,855, age 30.2 ± 7.7 years, 41.5% men) who participated in the Respiratory Health in Northern Europe, Spain and Australia (RHINESSA) study. Both generations responded to identical questionnaires on sleep symptoms, including difficulty initiating sleep (DIS), difficulty maintaining sleep (DMS), early morning awakening (EMA), snoring, nocturnal sweating, nocturnal gastroesophageal reflux (nGER), sleep time and excessive daytime sleepiness (EDS). Insomnia was defined as either, or both, DIS and DMS in combination with EDS.ResultsAll sleep variables except nocturnal sweating were more common in offspring whose parents had reported the same symptom. After adjusting for age, gender, BMI, smoking, physical activity, education, center and parents' total number of children, there were independent associations between sleep symptoms in parents and offspring for DIS (adj. OR, 95% CI: 1.52, 1.20–1.93), DMS (1.34, 1.15–1.56), snoring (1.45, 1.15,1.83), nGER (1.65, 1.15–2.37), insomnia (1.39, 1.13–1.73), short sleep time (<6 h/night) (2.51, 1.72–3.68) and EDS (1.48, 1.26,1.72). There were no independent relationships between symptoms in parents and offspring for EMA, nocturnal sweating or long sleep time (>9 h/night).ConclusionThe familiar aggregation of many sleep disturbances was not explained by investigated lifestyle and environmental factors. This supports a heritable factor in sleep problems.  相似文献   
30.
The stability and efficiency, especially the stability, are generally concerned issues in Q compensated reverse time migration (Q-RTM). The instability occurs because of the exponentially boosted high frequency ambient noise during the forward or backward seismic wavefield propagation. The regularization and low-pass filtering methods are two effective strategies to control the instability of the wave propagation in Q-RTM. However, the regularization parameters are determined experimentally, and the wavefield cannot be recovered accurately. The low-pass filtering method cannot balance the selection of cutoff frequency for varying Q values, and may damage the effective signals, especially when the signal-to-noise ratio (SNR) of the seismic data is low, the Q-RTM will be a highly unstable process. In order to achieve the purpose of stability, the selection of cutoff frequency will be small enough, which can cause great damage to the effective high frequency signals. In this paper, we present a stable Q-RTM algorithm based on the excitation amplitude imaging condition, which can compensate both the amplitude attenuation and phase dispersion. Unlike the existing Q-RTM algorithms enlarging the amplitude, the exponentially attenuated seismic wavefield will be used during both the forward and backward wavefield propagation of Q-RTM. Therefore, the new Q-RTM algorithm is relative stable, even for the low SNR seismic data. In order to show the accuracy and stability of our stable Q-RTM algorithm clearly, an example based on Graben model will be illustrated. Then, a realistic BP gas chimney model further demonstrates that the proposed method enjoys good stability and anti-noise performance compared with the traditional Q-RTM with amplitude amplification. Compare the Q-RTM images of these two models to the reference images obtained by the acoustic RTM with acoustic seismic data, the new Q-RTM results match the reference images quite well. The proposed method is also tested using a field seismic data, the result shows the effectiveness of our proposed method.  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