全文获取类型
收费全文 | 1785篇 |
免费 | 106篇 |
国内免费 | 10篇 |
专业分类
耳鼻咽喉 | 13篇 |
儿科学 | 45篇 |
妇产科学 | 149篇 |
基础医学 | 219篇 |
口腔科学 | 42篇 |
临床医学 | 129篇 |
内科学 | 282篇 |
皮肤病学 | 34篇 |
神经病学 | 206篇 |
特种医学 | 155篇 |
外科学 | 206篇 |
综合类 | 21篇 |
一般理论 | 1篇 |
预防医学 | 87篇 |
眼科学 | 98篇 |
药学 | 138篇 |
中国医学 | 6篇 |
肿瘤学 | 70篇 |
出版年
2024年 | 1篇 |
2023年 | 7篇 |
2022年 | 26篇 |
2021年 | 55篇 |
2020年 | 38篇 |
2019年 | 53篇 |
2018年 | 64篇 |
2017年 | 51篇 |
2016年 | 51篇 |
2015年 | 62篇 |
2014年 | 86篇 |
2013年 | 112篇 |
2012年 | 145篇 |
2011年 | 166篇 |
2010年 | 87篇 |
2009年 | 77篇 |
2008年 | 133篇 |
2007年 | 151篇 |
2006年 | 114篇 |
2005年 | 108篇 |
2004年 | 92篇 |
2003年 | 81篇 |
2002年 | 48篇 |
2001年 | 19篇 |
2000年 | 14篇 |
1999年 | 10篇 |
1998年 | 7篇 |
1997年 | 7篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1975年 | 3篇 |
1973年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有1901条查询结果,搜索用时 15 毫秒
1.
2.
3.
Ashish Raj Honglei Zhang Martin R Prince Yi Wang Ramin Zabih 《Magnetic resonance in medicine》2006,55(3):649-658
Time-resolved contrast enhanced magnetic resonance angiography (MRA) may suffer from involuntary patient motion. It is noted that while MR signal change associated with motion is large in magnitude and has smooth phase variation in k-phase, signal change associated with vascular enhancement is small in magnitude and has rapid phase variation in k-space. Based upon this observation, a novel projection onto convex sets (POCS) algorithm is developed as an automatic iterative method to remove motion artifacts. The presented POCS algorithm consists of high-pass phase filtering and convex projections in both k-space and image space. Without input of detailed motion knowledge, motion effects are filtered out, while vasculature information is preserved. The proposed method can be effective for a large class of nonrigid motions, including through-plane motion. The algorithm is stable and converges quickly, usually within five iterations. A double-blind evaluation on a set of clinical MRA cases shows that a completely unsupervised version of the algorithm produces significantly better rank scores (P=0.038) when compared to angiograms produced manually by an experienced radiologist. 相似文献
4.
James C Halstead David Spielvogel Dieter M Meier Sindy Rinke Carol Bodian Ramin Malekan M Arisan Ergin Randall B Griepp 《European journal of cardio-thoracic surgery》2005,27(4):626-32; discussion 632-3
OBJECTIVE: The indications for aortic root replacement in acute type A dissection are unclear. We reviewed the immediate and long-term outcome of consecutive patients in a series in which a low-threshold policy of composite aortic root replacement had evolved. METHODS: From a prospectively compiled aortic surgery database, we identified 162 patients who had either supracoronary interposition grafting, Group A (n=89), or composite root replacement, Group B (n=73) for acute type A dissection. Patients receiving total arch replacements were excluded. Operative and clinical details were analyzed and patient survival was compared to an age and gender matched census cohort. Need for reoperation on the proximal or distal aorta was also noted. Follow-up totaled 795.5 patient-years. RESULTS: Hospital mortality rates were identical in both groups (12.3%: 11 deaths in group A; 9 in group B). Chronic pulmonary disease, diabetes, malperfusion, hemodynamic compromise and aortic root dilatation were independent risk factors for hospital death. Actuarial survival estimates at 1, 5 and 10 years were 79% (71-88%), 64% (53-75%), and 55% (41-68%) for group A, and 79% (70-86%), 73% (62-83%), and 65% (52-78%) for group B (P=0.48). Age and operative patency of the ascending false lumen were independent risk factors for death after hospital discharge. Proximal aortic reoperation was required for four patients in group A and none in group B (P=0.085). CONCLUSION: A strategy of replacement rather than repair of the dissected aortic root for specific indications in type A dissection yielded high survival and low proximal reoperation rates. These results support an aggressive policy of composite root replacement in acute type A dissection. 相似文献
5.
Ramin Shadman Matthew A Allison Michael H Criqui 《Journal of the American College of Cardiology》2007,49(22):2172-2181
OBJECTIVES: The purpose of this work was to assess the prognostic role of glomerular filtration rate (GFR) and NT-terminal pro-B-type natriuretic peptide (NT-proBNP) for mortality end points in the vascular population. BACKGROUND: The GFR and NT-proBNP have been shown to predict mortality end points in free-living and limited vascular populations, independent of traditional risk factors. However, their prognostic power in an unrestricted vascular population is poorly understood. METHODS: A total of 412 subjects from a vascular cohort with a history of either peripheral arterial disease (PAD) and/or other cardiovascular disease (CVD) were included in this prospective cohort analysis and followed for an average of 6.7 years. Outcome variables were all-cause mortality, ischemic heart disease (IHD) mortality, and any cardiovascular mortality. The prognostic roles of GFR and NT-proBNP levels were determined using multivariate survival analysis. RESULTS: Higher GFR (per 10 ml/min/1.73 m2) was significantly protective for all-cause mortality (hazard ratio [HR] 0.81, p < 0.001), IHD mortality (HR 0.82, p = 0.008), and CVD mortality (HR 0.84, p = 0.005). Conversely, NT-proBNP was not a significant predictor of any mortality end point. The GFR showed the strongest association in subjects with a history of other CVD. Although NT-proBNP did not demonstrate a significant prognostic role in any of the subgroups, the data were suggestive for patients with PAD alone. CONCLUSIONS: Glomerular filtration rate was a robust predictor of all-cause, IHD, and cardiovascular mortality in the vascular population, particularly in those with a history of other CVD, while NT-proBNP showed a suggestive association limited to the group with PAD only. These findings suggest that these markers must be selectively applied in the vascular population for greatest clinical utility. 相似文献
6.
Many quantitative imaging protocols that make use of a metabolite-corrected arterial input function require the use of a mathematic model to describe the rate of metabolism of the radioligand. Commonly, parametric models are fit to metabolism data and then the fitted model is used to correct the plasma input function. (11)C-WAY 100635 is a rapidly metabolized radioligand used extensively in mapping the 5-hydroxytryptamine receptor 1A system. METHODS: To evaluate the adequacy of fit of 4 metabolite models, we examined data from 92 subjects who received an injection of (11)C-WAY 100635, were imaged with PET, and underwent measurement of total plasma concentration and metabolites. The performance of these models was assessed according to residual plots, as well as fit and information criteria. RESULTS: The study showed that the choice of model has a substantial effect on the resulting estimates of outcome measures. CONCLUSION: Among the models considered, the Hill model provides the best fit across all criteria. 相似文献
7.
Objective. Bone infarction (BI) of the calcaneus is an uncommon entity which has received little mention in the recent literature. In
this paper, we review the MR images of six calcanei with BI, which demonstrate a pattern of presentation that may explain
the etiology of BI at this unusual location. Design. A retrospective review was performed of the transcribed reports of the foot or ankle MR examinations at our institution.
MR images of examinations with any marrow signal abnormality were reviewed for presence of BI and its distribution. Patients. Based on MRI criteria, four patients had calcaneal BI (none biopsy proven); they ranged in age from 37 to 51 years old. Two
patients were diagnosed with systemic lupus erythematosus, one with fibrositis, and another with polymyositis. All were treated
with corticosteroids. Results. Six calcanei (in four patients) contained a region of calcaneal BI. In five of the six, the lesions were entirely or predominantly
located in the posterior half of the calcaneus. Conclusion. Two theories are proposed which may explain why BI predominantly occurs in the posterior half of the calcaneus. First, the
convergence of the recurrent intraosseous calcaneal vessels may occasionally produce the equivalent of a single dominant vessel
that is more prone to vascular accidents. Secondly, the region between the recurrent and the epiphyseal vessels may act as
a watershed zone, increasing its susceptibility to ischemia. 相似文献
8.
Carcinosarcomas are rare but aggressive neoplasms commonly described in organs such as the breast, urinary bladder, uterus, liver, and lungs. Histopathologically, they are characterized by the presence of malignant epithelial and mesenchymal components. The exact histogenesis of carcinosarcomas remains unknown and is debated in the literature. Primary carcinosarcomas of the skin are uncommon. To our knowledge, 20 cases of primary cutaneous carcinosarcoma have been described in the world literature. Most of these tumors were seen on the head and neck region of older individuals, both male and female. Microscopically, the more common carcinoma component is a squamous cell carcinoma followed by basal cell carcinoma, whereas the most common sarcoma component is an osteosarcoma. We report an example of this rare entity and speculate on its histogenesis in the skin. 相似文献
9.
Human chondrocytes differentially express matrix modulators during in vitro expansion for tissue engineering 总被引:2,自引:0,他引:2
Goessler UR Bieback K Bugert P Naim R Schafer C Sadick H Hormann K Riedel F 《International journal of molecular medicine》2005,16(4):509-515
Cartilage tissue engineering plays an important role in the generation of grafts for reconstructive surgery. In cultured chondrocytes, the dedifferentiation of cells seems unavoidable for multiplication. Dedifferentiated cells produce matrix of less quality, and the molecular basis is still not well understood. Therefore, the aim of our study was to investigate the expression of matrix modulators in human chondrocytes during expansion. Human chondrocytes were isolated from septal cartilage (n=32) and held in primary cell culture. Cells were harvested after 1, 6 and 21 days. The differentiation of cells using light microscopy, the expression patterns of various proteins (MMPs, BMPs, and TIMPs) using immunohistochemistry, and the expression of distinct genes using microarray technique, were investigated. The chondrocytes showed strong in vitro proliferation. After 6 and 21 days, BMP-5 and -8 were up-regulated, BMP-2 was down-regulated and BMP-6 was inactivated. Other BMPs were not expressed. The expression of MMP-2, -3 and -13 was up-regulated from day 1 to 21, and MMP-12 and -20 were down-regulated. Other MMPs were not expressed. TIMP-1 was up-regulated and TIMP-3 was down-regulated during expansion. Differential expression of matrix modulators might influence the matrix composition of engineered cartilage. Improving the basic knowledge in this area may ultimately help clinicians to identify and proactively intervene in an attempt to prevent bioartificial cartilage from losing stability. 相似文献
10.
Vahid Haghpanah Peiman Shooshtarizadeh Ramin Heshmat Bagher Larijani Seyed Mohamad Tavangar 《Applied immunohistochemistry & molecular morphology》2006,14(4):422-425
Survivin is one of the 8 members of human inhibitor of apoptosis , which is differentially expressed in cancerous/transformed cells versus normal differentiated tissues. This retrospective study of thyroid histologic samples aimed to assess the clinical usefulness of survivin immunostaining for discrimination between follicular adenoma and carcinoma of thyroid. Immunohistochemical staining for survivin was performed on 41 lesions from patients who had undergone surgery for either follicular adenoma or carcinoma of thyroid. Survivin expression was significantly (P < 0.005) higher in the cases that received a diagnosis of carcinoma in comparison with follicular adenomas cases. Odds ratio of follicular carcinoma for survivin expression was 21.375 (95% CI: 3.283 to 139.177). Our results showed potential value of survivin in discrimination between follicular thyroid adenoma and follicular thyroid carcinoma. We conclude that survivin is a potential candidate for further investigation in the proper histologic diagnosis of thyroid cancers. 相似文献