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   5232篇
  免费   276篇
  国内免费   109篇
耳鼻咽喉   92篇
儿科学   57篇
妇产科学   51篇
基础医学   870篇
口腔科学   115篇
临床医学   549篇
内科学   1008篇
皮肤病学   120篇
神经病学   452篇
特种医学   354篇
外科学   719篇
综合类   28篇
预防医学   200篇
眼科学   60篇
药学   465篇
中国医学   78篇
肿瘤学   399篇
  2023年   26篇
  2022年   121篇
  2021年   239篇
  2020年   109篇
  2019年   122篇
  2018年   155篇
  2017年   124篇
  2016年   199篇
  2015年   339篇
  2014年   352篇
  2013年   388篇
  2012年   568篇
  2011年   541篇
  2010年   269篇
  2009年   256篇
  2008年   332篇
  2007年   314篇
  2006年   242篇
  2005年   156篇
  2004年   117篇
  2003年   102篇
  2002年   91篇
  2001年   83篇
  2000年   68篇
  1999年   46篇
  1998年   40篇
  1997年   25篇
  1996年   31篇
  1995年   19篇
  1994年   27篇
  1993年   12篇
  1992年   14篇
  1991年   8篇
  1990年   8篇
  1989年   10篇
  1988年   8篇
  1987年   8篇
  1986年   10篇
  1985年   5篇
  1984年   4篇
  1982年   2篇
  1981年   2篇
  1980年   2篇
  1979年   2篇
  1978年   4篇
  1977年   13篇
  1976年   2篇
  1975年   1篇
  1970年   1篇
排序方式: 共有5617条查询结果,搜索用时 234 毫秒
51.
Extracellular matrix (ECM) plays an important role in controlling the β-cell morphology, survival and insulin secretary functions. An RGD-modified elastin-like polypeptide (RGD-ELP), TGPG[VGRGD(VGVPG)6]20WPC, has been reported previously as a bioactive matrix. In this study, to investigate whether RGD-ELP affects β-cell growth characteristics and insulin secretion, β-TC6 cells were cultured on the RGD-ELP coatings prepared via thermally induced phase transition. On RGD-ELP, β-TC6 cells clustered into an islet-like architecture with high cell viability. Throughout 7 days’ culture, the proliferation rate of the cells within a pseudoislet was similar to that of monolayer culture. Under high glucose (25 mM), β-TC6 pseudoislets showed up-regulated insulin gene expression and exhibited glucose-stimulated insulin secretion. Importantly, the mRNA and protein abundances of cell adhesion molecules (CAM) E-cadherin and connexin-36 were much higher in pseudoislets than in monolayer cells. The siRNA-mediated inhibition of E-cadherin or connexin-36 expression severely limited pseudoislet formation. In addition, the mRNA levels of collagen types I and IV, fibronectin and laminin were significantly elevated in pseudoislets. The results suggest that RGD-ELP promotes pseudoislet formation via up-regulation of the CAM and ECM components. The functional roles of RGD-ELP are discussed in respect of its molecular composition.  相似文献   
52.
We have successfully developed a multiscale acoustic-resolution photoacoustic tomography system in a single imaging platform. By switching between ultrasound transducers (center frequencies 5 and 40 MHz) and optical condensers, we have photoacoustically imaged microvasculatures of small animals in vivo at different scales. Further, we have extended the field of view of our imaging system to entire bodies of small animals. At different imaging planes, we have noninvasively imaged the major blood vessels (e.g., descending aorta, intercostal vessels, cephalic vessels, brachial vessels, femoral vessels, popliteal vessels, lateral marginal vessels, cranial mesenteric vessels, mammalian vessels, carotid artery, jugular vein, subclavian vessels, iliac vessels, and caudal vessels) as well as intact internal organs (e.g., spleen, liver, kidney, intestine, cecum, and spinal cord) of the animals in vivo. The spectroscopic whole-body photoacoustic imaging clearly reveals the spectral responses of the internal structures. Similar to other existing preclinical whole-body imaging systems, this whole-body photoacoustic tomography can be a useful tool for small-animal research.  相似文献   
53.
The aim of this study was to evaluate the change of breast density in the normal breast of patients receiving neoadjuvant chemotherapy (NAC). Forty‐four breast cancer patients were studied. MRI acquisition was performed before treatment (baseline), and 4 and 12 weeks after treatment. A computer‐algorithm‐based program was used to segment breast tissue and calculate breast volume (BV), fibroglandular tissue volume (FV), and percent density (PD) (the ratio of FV over BV × 100%). The reduction of FV and PD after treatment was compared with baseline using paired t‐tests with a Bonferroni–Holm correction. The association of density reduction with age was analyzed. FV and PD after NAC showed significant decreases compared with the baseline. FV was 110.0 ml (67.2, 189.8) (geometric mean (interquartile range)) at baseline, 104.3 ml (66.6, 164.4) after 4 weeks (p < 0.0001), and 94.7 ml (60.2, 144.4) after 12 weeks (comparison with baseline, p < 0.0001; comparison with 4 weeks, p = 0.016). PD was 11.2% (6.4, 22.4) at baseline, 10.6% (6.6, 20.3) after 4 weeks (p < 0.0001), and 9.7% (6.2, 17.9) after 12 weeks (comparison with baseline, p = 0.0001; comparison with 4 weeks, p = 0.018). Younger patients tended to show a higher density reduction, but overall correlation with age was only moderate (r = 0.28 for FV, p = 0.07, and r = 0.52 for PD, p = 0.0003). Our study showed that breast density measured from MR images acquired at 3T MR can be accurately quantified using a robust computer‐aided algorithm based on non‐parametric non‐uniformity normalization (N3) and an adaptive fuzzy C‐means algorithm. Similar to doxorubicin and cyclophosphamide regimens, the taxane‐based NAC regimen also caused density atrophy in the normal breast and showed reduction in FV and PD. The effect of breast density reduction was age related and duration related. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   
54.
55.
56.
57.
BackgroundOblique lateral interbody fusion (OLIF) at lumbosacral junction is typically performed on the central window between the bifurcations of iliac vessels. However, the central window of lumbosacral transitional vertebrae (LSTVs) is usually obstructed by the iliocaval venous structures. We aimed to describe the vascular anatomy and surgical approach in OLIF at LSTVs compared with those in OLIF at typical L5-S1 junction.MethodsSixty-eight consecutive patients who underwent OLIF at lumbosacral junction were included. Of these, 31 patients had LSTVs and 37 patients had typical L5-S1 junction. The position of the iliocaval junction and the configuration of the left common iliac vein were compared using the preoperative CT and MR images of the lumbar spine. The surgical approach and intraoperative vascular findings were analyzed.ResultsAlmost 70% of LSTVs had the iliocaval junction at low or very low position. Mobilization of left common iliac vein for central window was potentially difficult in almost 74% of OLIF at LSTVs while it was not required or was potentially easy in almost 80% of OLIF at typical L5-S1. Vascular injury was identified in 2 (6.5%) patients with OLIF at LSTVs and in 3 (8.1%) patients with OLIF at typical L5-S1 junction (P = 0.904).ConclusionsIn our series, OLIF at LSTVs was performed through lateral window in 93.5% of the cases. Preoperative evaluation of the iliocaval junction using CT/MR of lumbar spine was reliable and valid in the determination of OLIF approach at lumbosacral junction.  相似文献   
58.
ObjectiveTo report a case of vulvar epithelioid sarcoma, a rare type of tumor that has been reported in 37 cases in the English literature to date.Case reportWe report three cases of vulvar epithelioid sarcoma, proximal type. Wide excisions of the mass were performed with margins free of tumor in all three cases.ConclusionDue to its low incidence, there are no evidence-based diagnostic algorithms or published recommendations for treatment. Locoregional lymph node involvement, vascular invasion, tumor size larger than 2 cm, deep localization, presence of necrosis, and a high mitotic index are known as poor prognostic factors. Adjuvant radiotherapy is advisable in the presence of a high-grade tumor or positive margins. The beneficial effect of adjuvant chemotherapy is not well established. Treatment decisions should be made based on the individual case presentation and pathology evaluation.  相似文献   
59.
We present a case of developmental venous anomaly associated with arteriovenous fistula supplied by a single arterial feeder adjacent to a large acute intracerebral hemorrhage. The arteriovenous fistula was successfully obliterated by superselective embolization while completely preserving the developmental venous anomaly. Two similar cases, including superselective angiographic findings, have been reported in the literature; however, we describe herein superselective angiographic findings in more detail and demonstrate the arteriovenous shunt more clearly than the previous reports. In addition, a literature review was performed to discuss the association of a developmental venous anomaly with vascular lesions.  相似文献   
60.
Pulmonary sequestration is a rare cystic malformation composed of bronchopulmonary tissue that is discontinuous from the tracheobronchial tree and has an anomalous systemic blood supply. We present a case of a 40-y-old male who presented with an extralobar pulmonary sequestration and underwent a laparoscopic retroperitoneal mass excision. Preoperative imaging revealed a large 11.3-cm retroperitoneal tumor consisting of a multiloculated cystic lesion. The patient was discharged home, and at 3-mo follow-up no complaints were reported.  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