全文获取类型
收费全文 | 15740篇 |
免费 | 1045篇 |
国内免费 | 76篇 |
专业分类
耳鼻咽喉 | 132篇 |
儿科学 | 323篇 |
妇产科学 | 339篇 |
基础医学 | 1910篇 |
口腔科学 | 352篇 |
临床医学 | 1532篇 |
内科学 | 3083篇 |
皮肤病学 | 193篇 |
神经病学 | 1566篇 |
特种医学 | 628篇 |
外科学 | 2432篇 |
综合类 | 184篇 |
现状与发展 | 1篇 |
一般理论 | 28篇 |
预防医学 | 1341篇 |
眼科学 | 521篇 |
药学 | 1202篇 |
中国医学 | 27篇 |
肿瘤学 | 1067篇 |
出版年
2024年 | 17篇 |
2023年 | 146篇 |
2022年 | 292篇 |
2021年 | 633篇 |
2020年 | 311篇 |
2019年 | 466篇 |
2018年 | 547篇 |
2017年 | 398篇 |
2016年 | 413篇 |
2015年 | 504篇 |
2014年 | 687篇 |
2013年 | 808篇 |
2012年 | 1311篇 |
2011年 | 1277篇 |
2010年 | 697篇 |
2009年 | 648篇 |
2008年 | 1008篇 |
2007年 | 1015篇 |
2006年 | 955篇 |
2005年 | 964篇 |
2004年 | 821篇 |
2003年 | 741篇 |
2002年 | 673篇 |
2001年 | 123篇 |
2000年 | 73篇 |
1999年 | 104篇 |
1998年 | 129篇 |
1997年 | 102篇 |
1996年 | 87篇 |
1995年 | 75篇 |
1994年 | 59篇 |
1993年 | 52篇 |
1992年 | 57篇 |
1991年 | 45篇 |
1990年 | 46篇 |
1989年 | 44篇 |
1988年 | 37篇 |
1987年 | 37篇 |
1986年 | 26篇 |
1985年 | 21篇 |
1984年 | 34篇 |
1983年 | 29篇 |
1982年 | 26篇 |
1981年 | 35篇 |
1980年 | 32篇 |
1978年 | 17篇 |
1977年 | 14篇 |
1976年 | 17篇 |
1975年 | 12篇 |
1974年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
Alex Westerband Joseph L. Mills Scott S. Berman Glenn C. Hunter 《Annals of vascular surgery》1997,11(1):14-19
n = 69) normal; Group B (n= 29), abnormal, severe defects; Group C (n= 56), abnormal, mild–moderate defect. RCA detected 32 defects in Group B: 10 internal carotid (ICA), seven endpoint flaps,
two kinks, one dissection; 16 external carotid (ECA), 10 severe endpoint defects and six total occlusion; six common carotid
(CCA), five irregular proximal shelfs, one web. Thirty of 32 defects were successfully repaired as confirmed by normal repeat
RCA studies; one ECA defect was not repaired and the ICA dissection was irreparable. In Group C, 67 mild–moderate defects
were identified, but not corrected. These included <30% stenosis in the ICA (12), ECA (18), CCA (24), and vein patch corrugation
or irregularity (13). For the entire series the postoperative ICA occlusion rate was 2% (3/154), stroke rate 2.6% (4/154),
and a subsequent >50% restenosis rate of 7% (11/154). The yield from routine carotid completion arteriograms was significant,
with 19% of studies identifying a severe defect that required repair. Although the difference in stroke rates and restenosis
between the different groups did not reach statistical significance, patients with normal intraoperative arteriograms initially
or after correction of a significant RCA defect had no early carotid occlusion (p= 0.05, Fisher's exact test) compared to patients with residual RCA defects. All early carotid occlusions occurred in patients
with unrepaired defects. We conclude that RCA is an important method of quality control after CEA and exerts a subtle, but
real, reduction in postoperative complications. 相似文献
22.
Lina P Theodorakopoulou P Lionel Sadowsky Alex Jacobson William Lacefield 《American journal of orthodontics and dentofacial orthopedics》2004,125(3):329-336
The objectives of this study were to evaluate and compare the shear bond strengths and bond failure locations of 2 currently available orthodontic ceramic brackets. Forty polycrystalline ceramic brackets (Clarity, 3M Unitek, Monrovia, Calif) and 40 monocrystalline ceramic brackets (Inspire, Ormco, Orange, Calif) were bonded to 80 extracted premolars with the same bonding system. All bonded specimens were placed in distilled water for 42 hours at 37 degrees C followed by thermal cycling for 700 complete cycles. Forty ceramic brackets, 20 of each type, were tested on a universal testing machine to determine the shear force levels required to debond them. Forty ceramic brackets were removed with the debonding pliers recommended by the manufacturers. All teeth were examined under an optical microscope, and the adhesive remnant index was used to assess the bond failure locations. The mean shear bond strength of the Clarity brackets was 21.67 +/- 5.19 MPa, and the mean shear bond strength of the Inspire brackets was 20.32 +/- 8 MPa. The mean shear bond strengths of both brackets were higher than those considered clinically optimal. Most of the brackets (85% of Clarity and 75% of Inspire) tested on the machine failed at the bracket-adhesive interface. One premolar bonded with an Inspire bracket had enamel fracture upon debonding. Most of the brackets (90% of Clarity and 95% of Inspire) debonded with pliers failed at the bracket-adhesive interface. No enamel damage was evident in any specimen when the brackets were removed with the appropriate pliers. The results indicate that the safest way to remove ceramic brackets with respect to reducing the chance of enamel damage is to use the debonding technique specifically designed for each. 相似文献
23.
Simona Ben-Haim Ela Kupzov Ada Tamir Alex Frenkel Ora Israel 《Journal of nuclear cardiology》2006,13(6):791-800
BACKGROUND: Fluorine 18 fluorodeoxyglucose (FDG) uptake may be increased in atherosclerotic plaques in asymptomatic patients. Repeat positron emission tomography (PET)/computed tomography (CT) studies were assessed for changes in patterns of FDG uptake and CT calcifications. METHODS AND RESULTS: Fifty consecutive cancer patients (mean age, 68 +/- 8 years) had repeat PET/CT studies 8 to 26 months apart. PET, CT, and PET/CT images were retrospectively evaluated for vascular wall abnormalities and for interval changes in the thoracic and abdominal aortas, as well as in carotid and iliac arteries, classified as PET+/CT+, PET+/CT-, and PET-/CT+. There were 485 abnormal sites in the first study and 495 in the second. CT calcifications were found in 46 patients (92%) in the first study and in 47 (94%) in the second. Vascular wall FDG uptake was found in both studies in 37 patients (74%). The pattern changed in 57 of 119 PET+ sites (48%) in the second study compared with 15 of 366 PET- sites (4%) (P < .0001). In the second study new PET+ sites were observed in 36 of 111 sites (32%) versus new PET-/CT+ sites in 19 of 384 sites (5%) (P < .0001). CONCLUSIONS: Changes in vascular FDG activity and CT calcifications can be assessed by repeat PET/CT. FDG-avid foci may represent a dynamic process, transient inflammation, whereas CT calcifications may indicate stable atherosclerosis. These preliminary results support the need for further research. 相似文献
24.
Michael D. Cabana David Bruckman Susan L. Bratton Alex R. Kemper Noreen M. Clark 《The Journal of asthma》2003,40(7):741-749
Background. The National Heart, Lung, and Blood Institute (NHLBI) guidelines recommend that patients receive a follow-up outpatient asthma visit after being discharged from an emergency department (ED) for asthma. Objective. To measure the frequency of follow-up outpatient asthma visits and its association with repeat ED asthma visit. Design. We conducted a retrospective cohort study of children with asthma using claims data from a university-based managed care organization from 01 1998 to 10 2000. We performed a multivariate survival analysis using Cox proportional hazards model to determine the effect of follow-up outpatient asthma visits on the likelihood of a repeat ED asthma visit, after controlling for severity of illness, patient age, gender, insurance, and the specialty of the primary care provider. Results: A total of 561 children had 780 ED asthma visits. Of these, 103 (17%) had a repeat ED asthma visit within 1 year. Almost two-thirds of children (66%) did not receive outpatient follow-up for asthma within 30 days of an ED asthma visit. Outpatient asthma visits within 30 days of an ED asthma visit are associated with an increased likelihood (relative risk = 1.80; 95% confidence interval 1.19, 2.72) for repeat ED asthma visits within 1 year. Conclusions. Most patients do not have outpatient follow-up after an ED asthma visit. However, those patients that present for outpatient follow-up have an increased likelihood for repeat ED asthma visits. For the primary care provider, these outpatient follow-up visits signal an increased risk that a patient will return to the ED for asthma and are a key opportunity to prevent future ED asthma visits. 相似文献
25.
Intracranial Angioplasty and Stenting in the Awake Patient 总被引:1,自引:0,他引:1
Alex Abou-Chebl MD Derk W. Krieger MD Christopher T. Bajzer MD Jay S. Yadav MD FACC 《Journal of neuroimaging》2006,16(3):216-223
BACKGROUND AND PURPOSE: Endovascular treatment for intracranial atherosclerosis is evolving, but complications remain an issue. Most interventions are performed under general anesthesia, preventing intraprocedural clinical evaluations. We describe our approach to intracranial angioplasty and stenting, using local rather than general anesthesia, and intraprocedural neurological assessment. METHODS: We prospectively collected procedural and outcome information on all patients undergoing intracranial angioplasty and stenting. Patients underwent interventions under local anesthesia with mild intravenous sedation or analgesia only if needed. Intraoperative neurological evaluations were performed, and symptomatology was used to guide the interventional technique. RESULTS: Forty-eight arteries in 40 patients with a mean age of 65.2 years were treated. Thirty-two anterior and 16 posterior circulation segments were treated. Technical success was achieved in 100% of patients with reduction of the mean pretreatment stenosis from 85 +/- 8.6% to 7 +/- 10.1%. Stents were deployed in 40 segments; five patients were treated with drug-eluting stents. The cobalt-chromium coronary stents were the easiest to deliver. Thirty-seven patients were treated under local anesthesia and, of those, 61.4% experienced intraprocedural symptoms that led to some alteration of the interventional technique. Headache was the most common symptom, and, when persistent, it heralded the occurrence of subarachnoid hemorrhage. There were seven total neurological complications, but only five (10.5%) led to permanent morbidity (4 strokes) or mortality (1 death). CONCLUSIONS: Intracranial angioplasty and stenting can be successfully performed using coronary techniques and equipment including drug-eluting stents. Local anesthesia permits neurological evaluations and often leads to the adjustment of the interventional technique, potentially making the procedure safer. 相似文献
26.
Alex Zacharek Jieli Chen Xu Cui Ang Li Yi Li Cynthia Roberts Yifan Feng Qi Gao Michael Chopp 《Journal of cerebral blood flow and metabolism》2007,27(10):1684-1691
Bone marrow stromal cells (MSCs) increase vascular endothelial growth factor (VEGF) expression and promote angiogenesis after stroke. Angiopoietin-1 (Ang1) and its receptor Tie2 mediate vascular integrity and angiogenesis as does VEGF and its receptors. In this study, we tested whether MSC treatment of stroke increases Ang1/Tie2 expression, and whether Ang1/Tie2 with VEGF/ vascular endothelial growth factor receptor 2 (VEGFR2) (Flk1), in combination, induced by MSCs enhances angiogenesis and vascular integrity. Male Wistar rats were subjected to middle cerebral artery occlusion (MCAo) and treated with or without MSCs. Marrow stromal cell treatment significantly decreased blood-brain barrier (BBB) leakage and increased Ang1, Tie2, and occludin (a tight junction protein) expression in the ischemic border compared with MCAo control. To further test the mechanisms of MSC-induced angiogenesis and vascular stabilization, cocultures of MSCs with mouse brain endothelial cells (MBECs) or astrocytes were performed. Supernatant derived from MSCs cocultured with MBECs significantly increased MBEC expression of Ang1/Tie2 and Flk1 compared with MBEC alone. Marrow stromal cells cocultured with astrocytes also significantly increased astrocyte VEGF and Ang1/Tie2 expression compared with astrocyte culture alone. Conditioned media from MSCs alone, and media from cocultures of MSCs with astrocytes or MBECs, all significantly increased capillary tube-like formation of MBEC compared with control Dulbecco's modified Eagle's medium media. Inhibition of Flk1 and/or Ang1 significantly decreased MSC-induced MBEC tube formation. Knockdown of Tie2 expression in MBECs significantly inhibited MSC-induced tube formation. Our data indicate MSC treatment of stroke promotes angiogenesis and vascular stabilization, which is at least partially mediated by VEGF/Flk1 and Ang1/Tie2. 相似文献
27.
Elaine C McKevitt Eric Calvert Alex Ng Richard K Simons Andrew W Kirkpatrick Leanne Appleton D Ross G Brown 《Canadian journal of surgery》2003,46(3):211-215
INTRODUCTION: Elderly patients who suffer trauma have a higher mortality and use disproportionately more trauma resources than younger patients. To compare these 2 groups and determine the outcomes and characteristics of elderly patients, we reviewed patients in these 2 groups admitted and treated in our tertiary care provincial trauma centre. METHODS: From the provincial trauma registry we selected a cohort of 40 geriatric patients (group 1) (> or = 65 yr of age) with an ISS of 16 or more who were admitted to and spent time in our trauma service for more than 48 hours and compared them with a similar randomly selected cohort of 44 patients (group 2) aged 20-30 years. Family physicians were contacted for follow-up of these patients 2 years after discharge. We considered length of hospital stay, complications, disposition of the patients and use of consultation services. RESULTS: Patients in group 1 had a mean age of 72.1 years (range from 65-98 yr) and a mean ISS of 27.3 (range from 17-50). Patients in group 2 had a mean age of 26.3 years (range from 22-29 yr) and a mean ISS of 26.3 (range from 17-54). Hospital stay was significantly longer in the group 1: 34.5 days (95% confidence interval [CI]: 24-44 d) versus 21.6 days (95% CI: 15-28 d). More elderly patients experienced complications (35 v. 13, p < 0.001) and required medical consultations (35 v. 26, p < 0.001). In-hospital death rates were 8% (3 of 40) and 4% (2 of 44) respectively (p = 0.3). Fewer geriatric patients could be discharged home (35% [14 of 40] v. 27% [22 of 44], p = 0.056) or to rehabilitation facilities (28% [11 of 40] v. 34% [15 of 44], p = 0.3). Five geriatric patients were discharged to nursing homes (p = 0.007). Of the geriatric patients discharged to rehabilitation facilities or home, 75% were independent 2 years after discharge. CONCLUSIONS: Aggressive care for geriatric trauma patients is warranted, and resources should be directed toward rehabilitation. Based on our findings, we expect that creating a directed care pathway for these patients, targetting complications and earlier discharge, will further improve their outcomes. 相似文献
28.
Gilbert H. L. Tang Paul W. M. Fedak Terrence M. Yau Richard D. Weisel Alex Kulik Donald A. G. Mickle Ren-Ke Li 《European journal of cardio-thoracic surgery》2003,23(6):907-916
Current therapies for congestive heart failure are limited in efficacy or in applicability. Cardiac cell transplantation offers a novel therapeutic approach to improve heart function. Although significant progress has been made over the past decade in the development of cell transplantation, only recently have investigators studied the changes in ventricular function following cell transplantation. This review article describes the latest research developments, evaluates recent studies of ventricular function after cell transplantation, and discusses the future directions of cell transplantation as a new therapy to ‘repair broken hearts’. 相似文献
29.
30.