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   36986篇
  免费   3064篇
  国内免费   187篇
耳鼻咽喉   411篇
儿科学   1251篇
妇产科学   846篇
基础医学   4383篇
口腔科学   702篇
临床医学   3630篇
内科学   7760篇
皮肤病学   617篇
神经病学   2999篇
特种医学   1128篇
外科学   5459篇
综合类   838篇
一般理论   28篇
预防医学   2735篇
眼科学   1456篇
药学   2811篇
  1篇
中国医学   135篇
肿瘤学   3047篇
  2023年   258篇
  2022年   378篇
  2021年   1027篇
  2020年   622篇
  2019年   921篇
  2018年   1029篇
  2017年   754篇
  2016年   856篇
  2015年   981篇
  2014年   1322篇
  2013年   1644篇
  2012年   2579篇
  2011年   2594篇
  2010年   1437篇
  2009年   1279篇
  2008年   2205篇
  2007年   2148篇
  2006年   1978篇
  2005年   1908篇
  2004年   1822篇
  2003年   1565篇
  2002年   1419篇
  2001年   1156篇
  2000年   1038篇
  1999年   891篇
  1998年   340篇
  1997年   251篇
  1996年   226篇
  1995年   225篇
  1994年   199篇
  1993年   185篇
  1992年   529篇
  1991年   487篇
  1990年   447篇
  1989年   409篇
  1988年   369篇
  1987年   341篇
  1986年   335篇
  1985年   331篇
  1984年   229篇
  1983年   207篇
  1982年   142篇
  1981年   105篇
  1980年   112篇
  1979年   161篇
  1978年   95篇
  1977年   103篇
  1976年   71篇
  1974年   85篇
  1973年   72篇
排序方式: 共有10000条查询结果,搜索用时 531 毫秒
991.
992.

Background and objectives

Novel AKI biomarkers carry variable performance for prediction of AKI in patients with heterogeneous illness. Until utility is demonstrated in critically ill patients outside of the cardiopulmonary bypass population, AKI biomarkers are unlikely to gain widespread implementation. Operationalization of an AKI risk stratification methodology, termed renal angina, was recently reported to enhance prediction at the time of intensive care unit admission for persistent severe AKI. The renal angina index (RAI) was developed to provide the clinical context to direct AKI biomarker testing. This study tested the hypothesis that incorporation of AKI biomarkers in patients fulfilling renal angina improves the prediction of persistent severe AKI.

Design, setting, participants, & measurements

In a multicenter study of 214 patients admitted to the pediatric intensive care unit with sepsis, the discrimination of plasma neutrophil gelatinase–associated lipocalin (NGAL), matrix metalloproteinase-8 (MMP-8), and neutrophil elastase-2 (Ela-2) were determined individually and in combination with the RAI for severe AKI. Net reclassification improvement (NRI) and integrated discrimination improvement (IDI) were calculated.

Results

Individual biomarkers demonstrated marginal discrimination for severe AKI (area under curve [AUC]: NGAL, 0.72; MMP-8, 0.68; Ela-2, 0.72), inferior to prediction by the clinical model of the RAI (AUC=0.80). Incorporation of each biomarker significantly added to the renal angina model AKI prediction (AUC=0.80, increased to 0.84–0.88; P<0.05 for each). The inclusion of each biomarker with the RAI demonstrated NRI (0.512, 0.428, and 0.545 for NGAL, MMP-8, and Ela-2, respectively; all P<0.03) and IDI (0.075 for Ela-2). The inclusion of both Ela-2 and NGAL with RAI demonstrated an NRI of 0.871 (P<0.001) and an IDI of 0.1 (P=0.01).

Conclusions

This study shows that incorporation of AKI biomarkers into the RAI improves discrimination for severe AKI. The RAI optimizes the utility of AKI biomarkers in a heterogeneous, critically ill patient population.  相似文献   
993.
994.
Burning and stabbing pain in the feet and lower limbs can have a significant impact on the activities of daily living, including walking, climbing stairs and sleeping. Peripheral neuropathy in particular is often misdiagnosed or underdiagnosed because of a lack of awareness amongst both patients and physicians. Furthermore, crude screening tools, such as the 10‐g monofilament, only detect advanced neuropathy and a normal test will lead to false reassurance of those with small fiber mediated painful neuropathy. The underestimation of peripheral neuropathy is highly prevalent in the South‐East Asia region due to a lack of consensus guidance on routine screening and diagnostic pathways. Although neuropathy as a result of diabetes is the most common cause in the region, other causes due to infections (human immunodeficiency virus, hepatitis B or C virus), chronic inflammatory demyelinating polyneuropathy, drug‐induced neuropathy (cancer chemotherapy, antiretrovirals and antituberculous drugs) and vitamin deficiencies (vitamin B1, B6, B12, D) should be actively excluded.  相似文献   
995.

Objective

This study examined if ongoing support delivered by telephone following pulmonary rehabilitation (PR) assisted chronic obstructive pulmonary disease (COPD) patients to maintain health outcomes.

Methods

Phase one (n = 79) compared post-rehabilitation telephone-based support delivered by peers compared to usual care (UC). The second phase (n = 168) compared post-rehabilitation support from peer educators, respiratory therapists (RT), or UC. Primary outcome variables were St. George's Respiratory Questionnaire (SGRQ) total score and the six minute walk test (6MWT). Measures were obtained at baseline, immediately following PR, and six-months post PR.

Results

Six-month follow-up data for phase one was collected for 66 COPD patients (n = 35 peer support, n = 31 UC) and 142 for phase two (n = 42 peer support, n = 52 RT support, n = 48 UC). Per-protocol and intention to treat (ITT) analysis in both phases found no significant group by time differences for SGRQ or 6MWT.

Conclusion

Providing peer or RT support via telephone following PR was not more effective than UC for maintaining health outcomes.

Practice implications

There are concerns with using peers to provide ongoing support to COPD patients. Additionally, COPD patients require a higher level of care than telephone support can provide.  相似文献   
996.
Echocardiography is an important diagnostic tool in evaluating a patient with Staphylococcus aureus bacteremia (SAB) for diagnosing infective endocarditis (IE). We sought to compare the utility of transthoracic echocardiography (TTE) with transesophageal echocardiography (TEE) in screening for IE in patients with SAB. We performed a retrospective chart review of 285 adult patients from two tertiary care hospitals with at least one positive blood culture for S. aureus between 2010 and 2012. Patients who underwent echocardiography were divided into two groups: TTE (screened with TTE only) and TEE (screened with both TTE and TEE). The demographic factors and clinical outcomes were compared between the groups. Of the 285 charts reviewed, 213 (74.7 %) patients were screened with echocardiography: 183 (85.9 %) were screened with TTE alone and 30 (14.1 %) were screened with both TTE and TEE. TEE disclosed more cases of definite IE than TTE (8 [26.7 %] vs. 22 [12.0 %], p?=?0.046). The TEE group had higher mortality than the TTE group (15 [50.0 %] vs. 43 [23.5 %], p?=?0.004). In patients with definite IE, mortality was higher in the TEE group than in the TTE group (6 [75.0 %] vs. 6 [27.3 %], p?=?0.034). TEE discovered additional findings that were missed by TTE in 36.7 % of cases and refuted the findings of TTE in 13.3 % of cases. We do not support the routine use of TEE in patients with uncomplicated SAB. High-risk patients in which IE is a serious consideration should undergo investigation with TEE.  相似文献   
997.
Helicobacter pylori and Epstein–Barr virus (EBV) account for roughly 80% and 10%, respectively, of gastric carcinomas worldwide. Autophagy is an evolutionarily conserved and intricately regulated cellular process that involves the sequestration of cytoplasmic proteins and organelles into double‐membrane autophagosomes that eventually fuse with lysosomes for degradation of the engulfed content. Emerging evidence indicates that xenophagy, a form of selective autophagy, plays a crucial role in the pathogenesis of H. pylori‐ and EBV‐induced gastric cancer. Xenophagy specifically recognizes intracellular H. pylori and EBV and physically targets these pathogens to the autophagosomal–lysosomal pathway for degradation. In this connection, H. pylori or EBV‐induced dysregulation of autophagy may be causally linked to gastric tumourigenesis and therefore can be exploited as therapeutic targets. This review will discuss how H. pylori and EBV infection activate autophagy and how these pathogens evade recognition and degradation by the autophagic pathway. Elucidating the molecular aspects of H. pylori‐ and EBV‐induced autophagy will help us better understand the pathogenesis of gastric cancer and promote the development of autophagy modulators as antimicrobial agents. Published by John Wiley & Sons, Ltd  相似文献   
998.
999.
Dental pulp loss due to caries or pulpitis can affect the longevity of teeth. Dental pulp tissue engineering necessitates the use of progenitor cells that has the potential to differentiate into neural, vascular and odontoblasts like cells. Previous reports have shown that human gingival progenitor cells (HGPCs) can be differentiated into different cell types; however neural differentiation of these cells, to the best of our knowledge, has not been reported. Low intensity pulsed ultrasound (LIPUS) has been reported to enhance cell differentiation. The aims of this study were (1) to explore the potential neural differentiation of HGPCs and (2) to investigate the effect of LIPUS on the differentiation of HGPCs when incubated under neuroinductive conditions. The HGPCs were isolated from human interdental papilla proximal to the premolar teeth that were extracted for orthodontic purpose. The HGPCs were induced to differentiate into neural lineage using a neuroinductive culture medium. HGPCs were divided into four groups; control group, neuro-induction (NI) group, ultrasound group (LIPUS), and a combined NI+LIPUS group. HGPCs were harvested for immunostaining and q-PCR after 1 day. Immunostaining for neuron specific antigens and q-PCR suggested that HGPCs can be differentiated into neural lineage and that selected neurodifferentiation markers can be enhanced by LIPUS.  相似文献   
1000.
5F‐PY‐PICA and 5F‐PY‐PINACA are pyrrolidinyl 1‐(5‐fluoropentyl)ind (az)ole‐3‐carboxamides identified in 2015 as putative synthetic cannabinoid receptor agonist (SCRA) new psychoactive substances (NPS). 5F‐PY‐PICA, 5F‐PY‐PINACA, and analogs featuring variation of the 1‐alkyl substituent or contraction, expansion, or scission of the pyrrolidine ring were synthesized and characterized by nuclear magnetic resonance (NMR) spectroscopy and liquid chromatography–quadrupole time‐of‐flight–mass spectrometry (LC–QTOF–MS). In competitive binding experiments against HEK293 cells expressing human cannabinoid receptor type 1 (hCB1) or type 2 (hCB2), all analogs showed minimal affinity for CB1 (pKi < 5), although several demonstrated moderate CB2 binding (pKi 5.45–6.99). In fluorescence‐based membrane potential assays using AtT20‐hCB1 or ‐hCB2 cells, none of the compounds (at 10 μM) produced an effect >50% of the classical cannabinoid agonist CP55,940 (at 1 μM) at hCB1, although several showed slightly higher relative efficacy at hCB2. Expansion of the pyrrolidine ring of 5F‐PY‐PICA to an azepane ( 8 ) conferred the greatest hCB2 affinity (pKi 6.99) and activity (pEC50 7.54, Emax 72%) within the series. Unlike other SCRA NPS evaluated in vivo using radio biotelemetry, 5F‐PY‐PICA and 5F‐PY‐PINACA did not produce cannabimimetic effects (hypothermia, bradycardia) in mice at doses up to 10 mg/kg.  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