全文获取类型
收费全文 | 52942篇 |
免费 | 3681篇 |
国内免费 | 179篇 |
专业分类
耳鼻咽喉 | 601篇 |
儿科学 | 1064篇 |
妇产科学 | 795篇 |
基础医学 | 6778篇 |
口腔科学 | 692篇 |
临床医学 | 4885篇 |
内科学 | 12810篇 |
皮肤病学 | 532篇 |
神经病学 | 5182篇 |
特种医学 | 2106篇 |
外科学 | 8470篇 |
综合类 | 587篇 |
一般理论 | 65篇 |
预防医学 | 3638篇 |
眼科学 | 926篇 |
药学 | 3188篇 |
中国医学 | 49篇 |
肿瘤学 | 4434篇 |
出版年
2023年 | 255篇 |
2022年 | 519篇 |
2021年 | 1434篇 |
2020年 | 900篇 |
2019年 | 1294篇 |
2018年 | 1641篇 |
2017年 | 1119篇 |
2016年 | 1205篇 |
2015年 | 1443篇 |
2014年 | 2164篇 |
2013年 | 2512篇 |
2012年 | 4330篇 |
2011年 | 4295篇 |
2010年 | 2404篇 |
2009年 | 2153篇 |
2008年 | 3761篇 |
2007年 | 3875篇 |
2006年 | 3746篇 |
2005年 | 3688篇 |
2004年 | 3287篇 |
2003年 | 3029篇 |
2002年 | 2741篇 |
2001年 | 323篇 |
2000年 | 226篇 |
1999年 | 332篇 |
1998年 | 489篇 |
1997年 | 440篇 |
1996年 | 357篇 |
1995年 | 326篇 |
1994年 | 251篇 |
1993年 | 236篇 |
1992年 | 143篇 |
1991年 | 127篇 |
1990年 | 113篇 |
1989年 | 96篇 |
1988年 | 87篇 |
1987年 | 68篇 |
1986年 | 75篇 |
1985年 | 100篇 |
1984年 | 121篇 |
1983年 | 105篇 |
1982年 | 136篇 |
1981年 | 109篇 |
1980年 | 95篇 |
1979年 | 42篇 |
1978年 | 60篇 |
1977年 | 57篇 |
1976年 | 49篇 |
1975年 | 40篇 |
1974年 | 39篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
191.
192.
Jamieson M. Bourque Eric J. Velazquez Robert H. Tuttle Linda K. Shaw Christopher M. O’Connor Salvador Borges-Neto 《Journal of nuclear cardiology》2007,14(2):165-173
Background Left ventricular ejection fraction (LVEF) is a significant predictor of morbidity and death. The nuclear summed rest score
(SRS) measures myocardial perfusion defects and provides prognostic information, but its effects on long-term outcomes are
not fully established. Moreover, information regarding the potential interaction between these 2 covariates is limited. The
purpose of this study was to determine whether the mortality risk associated with LVEF is the same across all values of SRS
in a population undergoing evaluation for ischemic heart disease.
Methods and Results We examined 3,187 patients who underwent cardiac catheterization and perfusion single photon emission computed tomography
imaging with a maximum follow-up of 8.1 years and median follow-up of 3.1 years. Cox proportional hazards modeling showed
that increasing nuclear SRS and decreasing LVEF were independently associated with a higher long-term mortality rate, with
a clinically significant interaction between them (P=.032). Patients with a normal LVEF and a high SRS (greater perfusion abnormality) have a prognosis similar to those with
a reduced LVEF.
Conclusions Resting perfusion studies provide prognostic information for long-term survival and significantly impact the interpretition
of mortality risk associated with changes in LVEF. Patient prognostication, risk stratification, and future research using
these variables should take this interaction into account.
Supported by a grant from the Tom & Lynn Royster Foundation. Durham, NC, and a National Institutes of Health Research Fellowship
Grant (T5 GM08679-04), Bethesda, Md. 相似文献
193.
Wincy S C Chan Paul S F Yip Paul W C Wong Eric Y H Chen 《Archives of Suicide Research》2007,11(4):327-335
The suicide rate has been paralleled by an upward trend of unemployment in Hong Kong since 1997. This study aims to explore the unknown suicide-related factors among the unemployed. This information is useful in developing culturally specific suicide prevention initiatives related to unemployment. Seventy-six suicide deceased and 15 life subjects who were unemployed were selected from a previous psychological autopsy study. Logistic regression models were employed to estimate the relative suicide risks among the unemployed people. Among the unemployed, the suicide deceased were more likely to be male, had suffered from psychiatric illness, and had attempted suicide before. They also had acquired less competent social problem solving skills. Comparison with a small control group creates a generalizability problem. Suicide prevention for the unemployed could be done through mental health awareness programs; problem-solving skills training for attempters and males; and vocational training and job opportunities for discharged psychiatric patients and rehabilitees. 相似文献
194.
Suhny Abbara Sanjeeva Kalva Ricardo C. Cury Eric M. Isselbacher 《Journal of Cardiovascular Computed Tomography》2007,1(1):40-54
The clinical presentation of diseases involving the thoracic aorta ranges from a large number of asymptomatic patients with clinically undetectable thoracic aortic aneurysm to patients with symptoms of severe chest pain as a result of acute aortic dissection. Thoracic aortic disease often remains undiagnosed until a life-threatening complication occurs or the disease is discovered serendipitously on imaging studies performed for other purposes. Multidetector row computed tomography (MDCT) imaging of the aorta is used to diagnose various acute and chronic conditions, including aortic aneurysms, aortic dissection, intramural hematoma, penetrating atherosclerotic ulcer, traumatic injury, rupture, inflammatory disorders, and congenital malformations. This review illustrates the wide range of MDCT imaging findings of thoracic aortic disease. 相似文献
195.
A new Le Fort I internal distraction device in the treatment of severe maxillary hypoplasia. 总被引:2,自引:0,他引:2
Jaime Gateno Eric R Engel John F Teichgraeber Kyoko E Yamaji James J Xia 《Journal of oral and maxillofacial surgery》2005,63(1):148-154
PURPOSE: The purpose of this pilot study was to test a new Le Fort I internal distraction device. PATIENTS AND METHODS: A new internal Le Fort I distraction device designed by 1 of the authors was used in 3 patients with cleft lip and palate and severe maxillary hypoplasia who needed maxillary advancements in excess of 12 mm. Presurgical planning used CASSOS (SoftEnable Technology, Ltd, Hong Kong SAR, China) prediction tracing software and a stereolithographic model to calculate the distraction vector. The distractors were pre-bent and installed on the stereolithographic model and activated to advance the maxilla. Surgery was performed in a conventional manner, and distraction was started after a 7-day latency phase at the rate of 1 mm/day and continued until the presurgical plan was achieved. The distractor was removed after a 3-month consolidation phase. Cephalometric radiographs were taken at the completion of each phase. RESULTS: This new Le Fort I internal distraction device successfully distracted the maxillae as planned in all 3 patients. At the end of the distraction phase, the maxillary advancement was measured at 15.8 mm, 15.8 mm, and 13.5 mm, respectively. In each patient, a clockwise rotation of the maxilla was observed with a tendency to a posterior open bite. Postoperative radiographs also showed that the actual distraction vectors differed from the planned vectors. After the consolidation phase, radiographs showed a relapse of 2.6 mm, 0 mm, and 5.0 mm, respectively. There was no further relapse on 3-month follow-up radiographs. Each case showed radiographic evidence of excellent new bone formation at the osteotomy sites. CONCLUSION: The new Le Fort I internal distraction device produced the necessary advancement in all 3 patients. The study also showed that the actual distraction vector differed from the planned vector. This discrepancy was caused by a clockwise rotation of the maxilla during the distraction. Finally, the study showed a variable relapse rate not previously reported in maxillary distraction. 相似文献
196.
Mechanoregulation of human articular chondrocyte aggrecan and type II collagen expression by intermittent hydrostatic pressure in vitro. 总被引:6,自引:0,他引:6
197.
198.
Yi-Shing Lisa Cheng Harvey Kessler John Wright Eric Huang Ju-Ru Lin Li-Min Lin Yuk-Kwan Chen 《Oral surgery, oral medicine, oral pathology, oral radiology, and endodontics》2007,104(1):82-88
Four poorly differentiated malignant lesions occurred in a 60-year-old Chinese male in the nasal cavity, submandibular gland, a lymph node in the neck, and the mandible. These malignant lesions developed within an 8-year period and each showed distinctive histological features. Among these malignant lesions, the neoplasm in the submandibular gland presented variegated histological and immunohistochemical (IHC) features and posed a diagnostic challenge in interpretation. Based on microscopic and IHC findings, we believe the diagnosis of teratocarcinosarcoma is justified for the submandibular neoplasm and the metastasis in the lymph node. The pathological features and diagnoses of these malignant lesions are discussed. 相似文献
199.
PET imaging of oncogene overexpression using 64Cu-vasoactive intestinal peptide (VIP) analog: comparison with 99mTc-VIP analog. 总被引:13,自引:0,他引:13
Mathew L Thakur Mohan R Aruva Jean Gariepy Paul Acton Satish Rattan Shyam Prasad Eric Wickstrom Abass Alavi 《Journal of nuclear medicine》2004,45(8):1381-1389
The purpose of this study was to assess the feasibility of PET imaging of oncogene VPAC1 receptors overexpressed in human breast cancer cells. METHODS: Vasoactive intestinal peptide (VIP) analog (TP3982) was synthesized to harbor a carboxy-terminus lysine (Lys) residue separated from VIP-asparagine (Asn(28)) by 4-aminobutyric acid (Aba) as a spacer. Lys was derivatized with diaminopropionic acid coupled to a pair of dibenzoylthioglycolic acid residues as protecting groups. The analog was labeled with (64)Cu at pH 9 ((64)Cu-TP3982) and (99m)Tc at pH 12 ((99m)Tc-TP3982). (99m)Tc-TP3982 and VIP derivatized with Aba-GAGG and labeled with (99m)Tc ((99m)Tc-TP3654) were used as reference agents. Smooth muscle relaxivity assays performed with each derivative and compared with unaltered VIP(28) demonstrated functional integrity. In vitro stability of (64)Cu-TP3982 was determined by challenging the complex with 100-mol excess of diethylenetriaminepentaacetic acid (DTPA), human serum albumin (HSA), and cysteine. In vivo stability was determined in urine and serum for up to 24 h. The mass of the Cu-TP3982 complex was determined by mass spectrometry. Human T47D breast tumor xenografts were grown in athymic nude mice. Planar scintigraphic imaging was performed at 4 and 24 h after the intravenous administration of (99m)Tc-TP3982 and (99m)Tc-TP3654 and PET imaging was performed using a small animal MOSAIC PET scanner, also at 4 and 24 h after injection of (64)Cu-TP3982. Tissue-distribution studies were also performed. In a separate experiment, receptors were blocked by intravenous injection of authentic VIP(28) 30 min before the administration of (64)Cu-TP3982 and tissue distribution was examined. RESULTS: (64)Cu-TP3982 labeling yields were 98% +/- 1.2% and those for (99m)Tc-TP3982 and (99m)Tc-TP3654 were 98.2% +/- 1.1% and 97% +/- 1.6%, respectively. The biologic activity of both VIP analogs was uncompromised. When (64)Cu-TP3982 was challenged with 100-mol excess of DTPA, HSA, or cysteine, >98% radioactivity remained as (64)Cu-TP3982. In vivo, >98% of (64)Cu circulating in plasma remained as (64)Cu-TP3982. Of the (64)Cu excreted in urine 4, 20, and 24 h after injection, >98%, 89.9% +/- 0.9%, and 85% +/- 3%, respectively, were bound to TP3982. The mass of Cu-TP3982 as determined by surface-enhanced laser desorption/ionization time of flight (SELDI-TOF) was 4,049.7 Da. Four hours after receptor blocking with VIP(28), there was a significant reduction in uptake of all tissues except in the liver. With (64)Cu-TP3982, the 4-h postinjection tumor uptake was 10.8 +/- 2.1 %ID/g versus 0.5 +/- 0.02 %ID/g and 0.24 +/- 0.08 %ID/g for (99m)Tc-TP3982 and (99m)Tc-TP3654, respectively. Twenty-four hours after injection, the corresponding numbers were 17 +/- 0.7 %ID/g, 0.77 +/- 0.1 %ID/g, and 0.23 +/- 0.1 %ID/g. The severalfold greater uptake (21.2-74) of (64)Cu-TP3982 is attributable to the in vivo stability of the agent. CONCLUSION: The results suggest that the uncompromised biologic activity and the significantly greater tumor uptake of (64)Cu-TP3982, combined with the high sensitivity and enhanced resolution of PET imaging, make (64)Cu-TP3982 highly desirable for further studies in PET imaging of oncogene receptors overexpressed in breast and other types of cancers. 相似文献
200.