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   114767篇
  免费   6344篇
  国内免费   2418篇
耳鼻咽喉   731篇
儿科学   2689篇
妇产科学   1219篇
基础医学   8180篇
口腔科学   678篇
临床医学   15778篇
内科学   26811篇
皮肤病学   308篇
神经病学   5958篇
特种医学   7643篇
外国民族医学   4篇
外科学   14245篇
综合类   17939篇
现状与发展   6篇
预防医学   5154篇
眼科学   2991篇
药学   9103篇
  70篇
中国医学   2752篇
肿瘤学   1270篇
  2024年   153篇
  2023年   1593篇
  2022年   3276篇
  2021年   4445篇
  2020年   3954篇
  2019年   3459篇
  2018年   3560篇
  2017年   3265篇
  2016年   3393篇
  2015年   3524篇
  2014年   7610篇
  2013年   7748篇
  2012年   6384篇
  2011年   7024篇
  2010年   5686篇
  2009年   5682篇
  2008年   5868篇
  2007年   5979篇
  2006年   5391篇
  2005年   4491篇
  2004年   3646篇
  2003年   3049篇
  2002年   2521篇
  2001年   2469篇
  2000年   1897篇
  1999年   1755篇
  1998年   1616篇
  1997年   1578篇
  1996年   1196篇
  1995年   1301篇
  1994年   1110篇
  1993年   961篇
  1992年   928篇
  1991年   776篇
  1990年   702篇
  1989年   619篇
  1988年   613篇
  1987年   546篇
  1986年   470篇
  1985年   541篇
  1984年   515篇
  1983年   276篇
  1982年   422篇
  1981年   323篇
  1980年   282篇
  1979年   255篇
  1978年   214篇
  1977年   137篇
  1976年   114篇
  1975年   68篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
4.
We have updated recommendations on 12 controversial topics that were published in the 2013 National Consensus on the diagnosis, risk stratification and treatment of patients with pulmonary embolism (PE). A comprehensive review of the literature was performed for each topic, and each recommendation was evaluated in two teleconferences. For diagnosis, we recommend against using the Pulmonary Embolism Rule Out Criteria (PERC) rule as the only test to rule out PE, and we recommend using a D-dimer cutoff adjusted to age to rule out PE. We suggest using computed tomography pulmonary angiogram as the imaging test of choice for the majority of patients with suspected PE. We recommend using direct oral anticoagulants (over vitamin K antagonists) for the vast majority of patients with acute PE, and we suggest using anticoagulation for patients with isolated subsegmental PE. We recommend against inserting an inferior cava filter for the majority of patients with PE, and we recommend using full-dose systemic thrombolytic therapy for PE patients requiring reperfusion. The decision to stop anticoagulants at 3 months or to treat indefinitely mainly depends on the presence (or absence) and type of risk factor for venous thromboembolism, and we recommend against thrombophilia testing to decide duration of anticoagulation. Finally, we suggest against extensive screening for occult cancer in patients with PE.  相似文献   
5.
6.
7.
Noninvasive imaging of cardiac fibrosis is important for early diagnosis and intervention in chronic heart diseases. Here, we investigated whether noninvasive, contrast agent-free MRI T2-mapping can quantify myocardial fibrosis in preclinical models of aging and pressure overload. Myocardial fibrosis and remodeling were analyzed in two animal models: (i) aging (15-month-old male CF-1 mice vs. young 6- to 8-week-old mice), and (ii) pressure overload (PO; by transverse aortic constriction in 4- to 5-month-old male C57BL/6 mice vs. sham-operated for 14 days). In vivo T2-mapping was performed by acquiring data during the isovolumic and early diastolic phases, with a modified respiratory and ECG-triggered multiecho TurboRARE sequence on a 7-T MRI. Cine MRI provided cardiac morphology and function. A quantitative segmentation method was developed to analyze the in vivo T2-maps of hearts at midventricle, apex, and basal regions. The cardiac fibrosis area was analyzed ex vivo by picro sirius red (PSR) staining. Both aged and pressure-overloaded hearts developed significant myocardial contractile dysfunction, cardiac hypertrophy, and interstitial fibrosis. The aged mice had two phenotypes, fibrotic and mild-fibrotic. Notably, the aged fibrotic subgroup and the PO mice showed a marked decrease in T2 relaxation times (25.3 ± 0.6 in aged vs. 29.9 ± 0.7 ms in young mice, p = 0.002; and 24.3 ± 1.7 in PO vs. 28.7 ± 0.7 ms in shams, p = 0.05). However, no significant difference in T2 was detected between the aged mild-fibrotic subgroup and the young mice. Accordingly, an inverse correlation between myocardial fibrosis percentage (FP) and T2 relaxation time was derived (R2 = 0.98): T2 (ms) = 30.45 – 1.05 × FP. Thus, these results demonstrate a statistical agreement between T2-map–quantified fibrosis and PSR staining in two different clinically relevant animal models. In conclusion, T2-mapping MRI is a promising noninvasive contrast agent-free quantitative technique to characterize myocardial fibrosis.  相似文献   
8.
ObjectiveEach pulmonary segment is an anatomical and functional unit. However, it is fundamentally difficult to precisely distinguish every pulmonary segment using the conventional pulmonary intersegmental planes from computed tomography images. Building arteriopulmonary segments is likely to be an effective way to identify pulmonary segments.MethodsThe thoracic computed tomography images of 40 patients were collected. The anatomic structures of interest were extracted in the transverse, sagittal, and coronal planes using the semi-automated segmentation tools provided by Amira software. The intrapulmonary vessels were subsequently segmented and reconstructed. The distributions of the pulmonary arteries, veins, and bronchi were observed. In patients with pulmonary masses, the mass was also reconstructed.ResultsThe three-dimensional reconstructed images showed the branches of the pulmonary artery ramified up to their eighth order covering the entire lung as well as evident intersegmental gaps without pulmonary arteries. The segmental artery was closely accompanied by the segmental bronchi in 486 pulmonary segments (90% of total number of segments). The size and spatial location of the pulmonary mass within a pulmonary segment were also clearly visible.ConclusionsDemarcation of arteriopulmonary segments can be used to precisely distinguish every pulmonary segment and provide its detailed anatomical structure before pulmonary segmentectomy.  相似文献   
9.
PurposeTo investigate the safety and efficacy of thyroid artery embolization (TAE) in the treatment of nodular goiter (NG).MethodsDuring a 5.5-year period, 56 consecutive patients with a NG underwent TAE. In Group A, there were 20 patients with a solitary/dominant 5–11-cm nodule, and in Group B, there were 36 patients with numerous nodules. Of the 56 patients, 47 (84%) had a retrosternal goiter and 25 had hyperthyroidism. In all patients, clinical and radiological evaluations were made at baseline and 6 months after TAE, and these parameters were statistically compared.ResultsIn 56 patients, 145 of the 146 thyroid arteries were successfully embolized. The 30-day mortality rate was 1.8%. Minor and major complications occurred in 25 and 2 patients, respectively. Six months after the TAE, the mean nodule volume was reduced from 80.2 mL to 25.0 mL, the mean thyroid volume was reduced from 147.0 mL to 62.6 mL, and the mean intrathoracic extension was reduced from 31.7 mm to 15.9 mm (P < .001). Of the 22 patients with non–Graves hyperthyroidism, 19 (86%) became euthyroid. The mean thyroid-related patient-reported outcome scores improved from 155.4 to 70.4 (P < .001). Of the 51 patients, 50 (98%) declared that they would recommend TAE to other patients with NG.ConclusionsTAE is safe and effective for the treatment of NG, with a significant volume reduction of the nodule(s) and thyroid gland.  相似文献   
10.
PurposeTo review and to compare indirectly the outcomes of minimally invasive therapies for the treatment of lower urinary tract symptoms secondary to benign prostatic hyperplasia.Materials and MethodsA literature search via Medline and Cochrane Central databases was completed for randomized control studies published between January 2000 to April 2020 for the following therapies: Rezum, Urolift, Aquablation, and prostatic artery embolization (PAE). Data on the following variables were included: International prostate symptom score (IPSS), maximum urinary flow rate, quality of life, and postvoid residual (PVR). Standard mean differences between treatments were compared through a meta-analysis using transurethral resection of the prostate (TURP) to assess differences in treatment effect.ResultsThere was no significant difference in outcomes between therapies for IPSS at the 3, 6, and 12-month follow ups. Although outcomes for Rezum were only available out to 3 months, there were no consistently significant differences in outcomes when comparing Aquablation versus PAE versus Rezum. TURP PVR was significantly better than Urolift at 3, 6, and 12 months. No significant differences in minor or major adverse events were noted.ConclusionAlthough significant differences in outcomes were limited, Aquablation and PAE were the most durable at 12 months. PAE has been well studied on multiple randomized control trials with minimal adverse events while Aquablation has limited high quality data and has been associated with bleeding-related complications.  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