全文获取类型
收费全文 | 2176篇 |
免费 | 166篇 |
国内免费 | 9篇 |
专业分类
耳鼻咽喉 | 25篇 |
儿科学 | 94篇 |
妇产科学 | 40篇 |
基础医学 | 262篇 |
口腔科学 | 22篇 |
临床医学 | 155篇 |
内科学 | 478篇 |
皮肤病学 | 42篇 |
神经病学 | 77篇 |
特种医学 | 214篇 |
外科学 | 296篇 |
综合类 | 85篇 |
一般理论 | 2篇 |
预防医学 | 111篇 |
眼科学 | 68篇 |
药学 | 211篇 |
中国医学 | 8篇 |
肿瘤学 | 161篇 |
出版年
2023年 | 11篇 |
2022年 | 31篇 |
2021年 | 65篇 |
2020年 | 24篇 |
2019年 | 42篇 |
2018年 | 58篇 |
2017年 | 48篇 |
2016年 | 61篇 |
2015年 | 57篇 |
2014年 | 83篇 |
2013年 | 100篇 |
2012年 | 149篇 |
2011年 | 162篇 |
2010年 | 112篇 |
2009年 | 80篇 |
2008年 | 138篇 |
2007年 | 121篇 |
2006年 | 134篇 |
2005年 | 123篇 |
2004年 | 123篇 |
2003年 | 87篇 |
2002年 | 68篇 |
2001年 | 32篇 |
2000年 | 36篇 |
1999年 | 39篇 |
1998年 | 16篇 |
1997年 | 12篇 |
1996年 | 14篇 |
1995年 | 10篇 |
1994年 | 11篇 |
1993年 | 13篇 |
1992年 | 23篇 |
1991年 | 32篇 |
1990年 | 22篇 |
1989年 | 18篇 |
1988年 | 10篇 |
1987年 | 9篇 |
1986年 | 11篇 |
1985年 | 12篇 |
1983年 | 11篇 |
1982年 | 13篇 |
1981年 | 12篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1976年 | 7篇 |
1974年 | 10篇 |
1972年 | 10篇 |
1970年 | 7篇 |
1969年 | 9篇 |
排序方式: 共有2351条查询结果,搜索用时 15 毫秒
61.
62.
Duan C Karnik R Lu MC Majumdar A 《Proceedings of the National Academy of Sciences of the United States of America》2012,109(10):3688-3693
Cavitation, known as the formation of vapor bubbles when liquids are under tension, is of great interest both in condensed matter science as well as in diverse applications such as botany, hydraulic engineering, and medicine. Although widely studied in bulk and microscale-confined liquids, cavitation in the nanoscale is generally believed to be energetically unfavorable and has never been experimentally demonstrated. Here we report evaporation-induced cavitation in water-filled hydrophilic nanochannels under enormous negative pressures up to -7 MPa. As opposed to receding menisci observed in microchannel evaporation, the menisci in nanochannels are pinned at the entrance while vapor bubbles form and expand inside. Evaporation in the channels is found to be aided by advective liquid transport, which leads to an evaporation rate that is an order of magnitude higher than that governed by Fickian vapor diffusion in macro- and microscale evaporation. The vapor bubbles also exhibit unusual motion as well as translational stability and symmetry, which occur because of a balance between two competing mass fluxes driven by thermocapillarity and evaporation. Our studies expand our understanding of cavitation and provide new insights for phase-change phenomena at the nanoscale. 相似文献
63.
SR Majumdar FA McAlister JA Johnson D Bellerose K Siminoski DA Hanley I Qazi DA Lier RG Lambert AS Russell BH Rowe 《The American journal of medicine》2012,125(9):929-936
BackgroundMost vertebral compression fractures are not recognized or treated. We conducted a controlled trial in older patients with vertebral fractures incidentally reported on chest radiographs, comparing usual care with osteoporosis interventions directed at physicians (opinion-leader-endorsed evidence summaries and reminders) or physicians+patients (adding activation with leaflets and telephone counseling).MethodsPatients aged >60 years who were discharged home from emergency departments and who had vertebral fractures reported but were not treated for osteoporosis were allocated to usual care (control) or physician intervention using alternate-week time series. After 3 months, untreated controls were re-allocated to physician+patient intervention. Allocation was concealed, outcomes ascertainment blinded, and analyses intent-to-treat. Primary outcome was starting osteoporosis treatment within 3 months.ResultsThere were 1315 consecutive patients screened, and 240 allocated to control (n = 123) or physician intervention (n = 117). Groups were similar at baseline (average age 74 years, 45% female, 58% previous fractures). Compared with controls, physician interventions significantly (all P <.001) increased osteoporosis treatment (20 [17%] vs 2 [2%]), bone mineral density testing (51 [44%] vs 5 [4%]), and bone mineral density testing or treatment (57 [49%] vs 7 [6%]). Three months after controls were re-allocated to physician+patient interventions, 22% had started treatment and 65% had bone mineral density testing or treatment (P <.001 vs controls). Physician+patient interventions increased bone mineral density testing or treatment an additional 16% compared with physician interventions (P = .01).ConclusionsAn opinion-leader-based intervention targeting physicians substantially improved rates of bone mineral density testing and osteoporosis treatment in patients with incidental vertebral fractures, compared with usual care. Even better osteoporosis management was achieved by adding patient activation to physician interventions [NCT00388908]. 相似文献
64.
65.
Bandyopadhyay Arghya M.D. Majumdar Kaushik M.D. D.N.B. Gangopadhyay Mimi M.D. Chakraborty Subrata M.D. 《Diagnostic cytopathology》2013,41(5):459-462
Histoplasmosis is usually an opportunistic fungal infection in patients with defective cell mediated immunity, and has been considered as one of the acquired immunodeficiency syndrome (AIDS) defining illness. However, cutaneous involvement in human immunodeficiency virus (HIV) positive patients is less common, and very rarely can be the initial presenting symptom for the diagnosis of AIDS. We present here an unusual case of multiple diffuse cutaneous nodular lesions predominantly in face, trunk, and upper extremities diagnosed initially on aspiration cytology as histoplasmosis. Subsequent serological test revealed positivity for HIV 1 and 2, along with a low CD4 count and low CD4:CD3 ratio. The cytomorphological features were further corroborated by histology and histochemical stains. Hence, cutaneous histoplasmosis can cause multiple wide spread nodular or umbilicated lesions in AIDS patients as the initial presentation. Fine needle aspiration cytology (FNAC) is a rapid, cost effective tool for diagnosis of the fungi from such lesions and initiating work up for immunocompromised states including AIDS. Diagn. Cytopathol. 2013. © 2011 Wiley Periodicals, Inc. 相似文献
66.
67.
68.
Sharmila Rajendrababu Hiruni Kaushalya Wijesinghe Mohammed Sithiq Uduman Naresh Babu Kannan Chitaranjan Mishra Lalitha Prajna 《Indian journal of ophthalmology》2021,69(2):279
Purpose:The purpose of this study is to compare the endothelial cell loss (ECL) in nanophthalmic eyes and age-matched controls undergoing cataract surgery by phacoemulsification and also to identify the risk factors influencing the endothelial cell density (ECD). This was a prospective comparative interventional case series.Methods:We enrolled 19 nanophthalmic eyes (study group) and 42 age-matched cataract controls (control group) undergoing phacoemulsification after meeting the inclusion criteria. Ocular parameters like best-corrected visual acuity, intraocular pressure, pachymetry, specular microscopy, and slit lamp findings were noted preoperatively and at month 1 and 3 postsurgery. All nanophthalmic eyes underwent cataract surgery with concomitant prophylactic posterior sclerostomy.Results:The median percentage endothelial loss in nanophthalmic eyes was 4.0 (IQR 0–23.5), 7.4 (IQR 1.0–-22.4) at 1 and 3 months postoperatively compared to 6.3 (IQR 1.7–14.1) and 6.4 (IQR 2.6–-12.1) in age controlled normal eyes (P = 0.94, P = 0.46, respectively). Linear regression analysis showed increasing age as the only variable influencing the percentage decrease in corneal ECD in the study group (P = 0.001). Nanophthalmic eyes with ACD <2.5 mm had a significantly greater reduction in ECD at 3 months postcataract surgery compared to baseline (P = 0.039). Visual outcomes and IOP reduction in the study group with ACD >2.5 mm were significantly better postcataract surgery (P = 0.02 and P = 0.002, respectively).Conclusion:The percentage of ECL in nanophthalmic eyes undergoing phacoemulsification is equivalent to normal eyes. However, in the nanophthamic eyes with AC depth <2.5 mm, the percentage cell loss was significantly higher warranting the need for extensive intraoperative care. Increasing age was found to be the only significant risk factor influencing the ECD in short eyes. 相似文献
69.
Andrew J Burghardt Jean‐Baptiste Pialat Galateia J Kazakia Stephanie Boutroy Klaus Engelke Janina M Patsch Alexander Valentinitsch Danmei Liu Eva Szabo Cesar E Bogado Maria Belen Zanchetta Heather A McKay Elizabeth Shane Steven K Boyd Mary L Bouxsein Roland Chapurlat Sundeep Khosla Sharmila Majumdar 《Journal of bone and mineral research》2013,28(3):524-536
High‐resolution peripheral quantitative computed tomography (HR‐pQCT) has recently been introduced as a clinical research tool for in vivo assessment of bone quality. The utility of this technology to address important skeletal health questions requires translation to standardized multicenter data pools. Our goal was to evaluate the feasibility of pooling data in multicenter HR‐pQCT imaging trials. Reproducibility imaging experiments were performed using structure and composition‐realistic phantoms constructed from cadaveric radii. Single‐center precision was determined by repeat scanning over short‐term (<72 hours), intermediate‐term (3–5 months), and long‐term intervals (28 months). Multicenter precision was determined by imaging the phantoms at nine different HR‐pQCT centers. Least significant change (LSC) and root mean squared coefficient of variation (RMSCV) for each interval and across centers was calculated for bone density, geometry, microstructure, and biomechanical parameters. Single‐center short‐term RMSCVs were <1% for all parameters except cortical thickness (Ct.Th) (1.1%), spatial variability in cortical thickness (Ct.Th.SD) (2.6%), standard deviation of trabecular separation (Tb.Sp.SD) (1.8%), and porosity measures (6% to 8%). Intermediate‐term RMSCVs were generally not statistically different from short‐term values. Long‐term variability was significantly greater for all density measures (0.7% to 2.0%; p < 0.05 versus short‐term) and several structure measures: cortical thickness (Ct.Th) (3.4%; p < 0.01 versus short‐term), cortical porosity (Ct.Po) (15.4%; p < 0.01 versus short‐term), and trabecular thickness (Tb.Th) (2.2%; p < 0.01 versus short‐term). Multicenter RMSCVs were also significantly higher than short‐term values: 2% to 4% for density and micro–finite element analysis (µFE) measures (p < 0.0001), 2.6% to 5.3% for morphometric measures (p < 0.001), whereas Ct.Po was 16.2% (p < 0.001). In the absence of subject motion, multicenter precision errors for HR‐pQCT parameters were generally less than 5%. Phantom‐based multicenter precision was comparable to previously reported in in vivo single‐center precision errors, although this was approximately two to five times worse than ex vivo short‐term precision. The data generated from this study will contribute to the future design and validation of standardized procedures that are broadly translatable to multicenter study designs. © 2013 American Society for Bone and Mineral Research. 相似文献