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   21543篇
  免费   2259篇
  国内免费   457篇
耳鼻咽喉   199篇
儿科学   371篇
妇产科学   225篇
基础医学   2289篇
口腔科学   445篇
临床医学   2799篇
内科学   2789篇
皮肤病学   157篇
神经病学   1781篇
特种医学   1483篇
外国民族医学   4篇
外科学   2041篇
综合类   2490篇
现状与发展   1篇
一般理论   2篇
预防医学   2256篇
眼科学   440篇
药学   2427篇
  34篇
中国医学   1011篇
肿瘤学   1015篇
  2024年   51篇
  2023年   360篇
  2022年   487篇
  2021年   984篇
  2020年   963篇
  2019年   907篇
  2018年   981篇
  2017年   935篇
  2016年   795篇
  2015年   853篇
  2014年   1526篇
  2013年   1510篇
  2012年   1276篇
  2011年   1387篇
  2010年   1178篇
  2009年   999篇
  2008年   980篇
  2007年   974篇
  2006年   935篇
  2005年   708篇
  2004年   646篇
  2003年   564篇
  2002年   498篇
  2001年   331篇
  2000年   304篇
  1999年   303篇
  1998年   232篇
  1997年   203篇
  1996年   191篇
  1995年   179篇
  1994年   186篇
  1993年   134篇
  1992年   141篇
  1991年   141篇
  1990年   145篇
  1989年   133篇
  1988年   122篇
  1987年   99篇
  1986年   96篇
  1985年   120篇
  1984年   112篇
  1983年   99篇
  1982年   84篇
  1981年   95篇
  1980年   77篇
  1979年   48篇
  1978年   34篇
  1977年   31篇
  1976年   34篇
  1973年   18篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
PurposeTo investigate dynamic variables obtained from retrospective computed tomography angiography for ability to predict thoracic endovascular aortic repair (TEVAR) outcomes in patients with complicated type B aortic dissection (cTBAD).Materials and MethodsSeventy-nine patients with cTBAD who received TEVAR from March 2009 to June 2018 were retrospectively enrolled. Relative true lumen area (r-TLA) was computed at the level of tracheal bifurcation every 5% of all R-R intervals. Parameters that reflect the state of intimal motion were evaluated, including difference between maximum and minimum r-TLA (D-TLA) and true lumen collapse. The endpoints comprised early (≤ 30 days) and late (> 30 days) outcomes after intervention.ResultsOverall early mortality rate was 13.9% (11/79), and early adverse events rate was 24.1% (19/79). Patients who received TEVAR within 2 days of symptom onset demonstrated the worst outcomes. A longer time of r-TLA < 25% in 1 cardiac cycle (P = .049) and larger D-TLA (P < .001) were correlated to an increased early death. In addition, D-TLA was an independent predictor of early mortality. Area under the curve of D-TLA was 0.849 (95% confidence interval 0.730–0.967) for predicting early mortality and 0.742 (95% CI 0.611–0.873) for predicting early adverse events. Survival and event-free survival rates during follow-up were decreased in the D-TLA > 21.5% group compared with the D-TLA ≤ 21.5% group (all P < .001).ConclusionsLarger D-TLA is correlated with worse postoperative outcomes and might be a crucial parameter for future risk stratification in patients with cTBAD.  相似文献   
22.
23.
24.
Episodic memory is defined as the ability to recall events in a spatiotemporal context. Formation of such memories is critically dependent on the hippocampal formation and its inputs from the entorhinal cortex. To be able to support the formation of episodic memories, entorhinal cortex and hippocampal formation should contain a neuronal code that follows several requirements. First, the code should include information about position of the agent (“where”), sequence of events (“when”), and the content of the experience itself (“what”). Second, the code should arise instantly thereby being able to support memory formation of one‐shot experiences. For successful encoding and to avoid interference between memories during recall, variations in location, time, or in content of experience should result in unique ensemble activity. Finally, the code should capture several different resolutions of experience so that the necessary details relevant for future memory‐based predictions will be stored. We review how neuronal codes in entorhinal cortex and hippocampus follow these requirements and argue that during formation of episodic memories entorhinal cortex provides hippocampus with instant information about ongoing experience. Such information originates from (a) spatially modulated neurons in medial entorhinal cortex, including grid cells, which provide a stable and universal positional metric of the environment; (b) a continuously varying signal in lateral entorhinal cortex providing a code for the temporal progression of events; and (c) entorhinal neurons coding the content of experiences exemplified by object‐coding and odor‐selective neurons. During formation of episodic memories, information from these systems are thought to be encoded as unique sequential ensemble activity in hippocampus, thereby encoding associations between the content of an event and its spatial and temporal contexts. Upon exposure to parts of the encoded stimuli, activity in these ensembles can be reinstated, leading to reactivation of the encoded activity pattern and memory recollection.  相似文献   
25.

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   
26.
27.
《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   
28.
《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   
29.
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   
30.
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   
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