全文获取类型
收费全文 | 304260篇 |
免费 | 7625篇 |
国内免费 | 237篇 |
专业分类
耳鼻咽喉 | 3037篇 |
儿科学 | 12048篇 |
妇产科学 | 7129篇 |
基础医学 | 34446篇 |
口腔科学 | 4568篇 |
临床医学 | 21939篇 |
内科学 | 56004篇 |
皮肤病学 | 4335篇 |
神经病学 | 26994篇 |
特种医学 | 14802篇 |
外国民族医学 | 32篇 |
外科学 | 49754篇 |
综合类 | 3936篇 |
一般理论 | 36篇 |
预防医学 | 24364篇 |
眼科学 | 6303篇 |
药学 | 18136篇 |
中国医学 | 959篇 |
肿瘤学 | 23300篇 |
出版年
2021年 | 942篇 |
2019年 | 966篇 |
2018年 | 23059篇 |
2017年 | 18293篇 |
2016年 | 20833篇 |
2015年 | 2466篇 |
2014年 | 2903篇 |
2013年 | 3828篇 |
2012年 | 11125篇 |
2011年 | 25087篇 |
2010年 | 21345篇 |
2009年 | 13963篇 |
2008年 | 23602篇 |
2007年 | 25945篇 |
2006年 | 5092篇 |
2005年 | 6818篇 |
2004年 | 7859篇 |
2003年 | 8585篇 |
2002年 | 6623篇 |
2001年 | 7431篇 |
2000年 | 7491篇 |
1999年 | 6153篇 |
1998年 | 1963篇 |
1997年 | 1882篇 |
1996年 | 1500篇 |
1995年 | 1372篇 |
1994年 | 1236篇 |
1993年 | 1219篇 |
1992年 | 3854篇 |
1991年 | 3698篇 |
1990年 | 3733篇 |
1989年 | 3459篇 |
1988年 | 3057篇 |
1987年 | 2962篇 |
1986年 | 2856篇 |
1985年 | 2667篇 |
1984年 | 1985篇 |
1983年 | 1641篇 |
1982年 | 970篇 |
1981年 | 931篇 |
1979年 | 1841篇 |
1978年 | 1369篇 |
1977年 | 1133篇 |
1976年 | 955篇 |
1975年 | 1202篇 |
1974年 | 1248篇 |
1973年 | 1220篇 |
1972年 | 1056篇 |
1971年 | 987篇 |
1970年 | 911篇 |
排序方式: 共有10000条查询结果,搜索用时 22 毫秒
991.
Kuniaki Nakahara Satoru Shimizu Satoshi Utsuki Sachio Suzuki Hidehiro Oka Kiyotaka Fujii 《Child's nervous system》2007,23(8):863-865
Objects We evaluated whether the presence of lacunar skull deformity (LSD) with myelomeningocele is a predictive factor for subsequent
hydrocephalus development.
Materials and methods We reviewed the clinical and radiological records of 18 infants with myelomeningocele, divided the patients into groups with
(group A, n=9) and without (group B, n=9) ventriculomegaly at birth and assessed whether the presence of LSD was predictive of the necessity for ventriculoperitoneal
shunt (VPS) placement.
Results LSD was present in five group A patients. All nine group A patients underwent VPS placement. Among the group B patients, five
had LSD; they underwent VPS placement. A significantly higher proportion of those with ventricle enlargement or LSD at birth
required VPS placement (p=0.0001).
Conclusion Adding to the ventriculomegaly at birth, the presence of LSD alerts to the necessity to monitor these infants closely to determine
the necessity for VPS placement. 相似文献
992.
993.
994.
Paolo Miletto 《European journal of nuclear medicine and molecular imaging》2007,34(2):304-304
995.
James A. Case Bai Ling Hsu Timothy M. Bateman S. James Cullom 《Journal of nuclear cardiology》2007,14(3):324-333
Background High-quality attenuation maps are critical for attenuation correction of myocardial perfusion single photon emission computed
tomography studies. The filtered backprojection (FBP) approach can introduce errors, especially with low-count transmission
data. We present a new method for attenuation map reconstruction and examine its performance in phantom and patient data.
Methods and Results The Bayesian iterative transmission gradient algorithm incorporates a spatially varying gamma prior function that preferentially
weights estimated attenuation coefficients toward the soft-tissue value while allowing data-driven solutions for lung and
bone regions. The performance with attenuation-corrected technetium 99m sestamibi clinical images was evaluated in phantom
studies and in 50 low-likelihood patients grouped by body mass index (BMI). The algorithm converged in 15 iterations in the
phantom studies. For the clinical studies, soft-tissue estimates had significantly greater uniformity of mediastinal coefficients
(mean SD, 0.005 cm−1 vs 0.011 cm−1; P<.0001). The accuracy and uniformity of the Bayesian iterative transmission gradient algorithm were independent of BMI, whereas
both declined at higher BMI values with FBP. Attenuation-corrected perfusion images showed improvement in myocardial wall
variability (4.8% to 4.1%, P=.02) for all BMI groups with the new method compared with FBP.
Conclusion This new method for attenuation map reconstruction provides rapidly converging and accurate attenuation maps over a wide spectrum
of patient BMI values and significantly improves attenuation-corrected perfusion images. 相似文献
996.
Y Unlü S Kele? N Becit C U Ko?o?ullari H Ko?ak E Bakan 《European journal of vascular and endovascular surgery》2005,30(3):315-318
OBJECTIVE: Several studies have shown a relation between hyperhomocysteinaemia and vascular disease. To assess the risk of deep-vein thrombosis (DVT) associated with hyperhomocysteinaemia, we studied plasma homocysteine levels in patients with deep-vein thrombosis and in normal control subjects. MATERIALS AND METHODS: We measured plasma homocysteine levels in 48 patients with deep-vein thrombosis and in 33 healthy controls matched to the patients according to age and sex. Plasma homocysteine levels were measured with high performance liquid chromatography and fluorescence detection. Hyperhomocysteinaemia was defined as a plasma homocysteine level about 15 micromol/L in both groups. The diagnosis of all patients with deep-vein thrombosis (n=48) was verified by Doppler ultrasonography. RESULTS: Plasma homocysteine levels were found to be increased in the deep-vein thrombosis group compared the control group (p<0.001, t-test). The mean plasma homocysteine level in the patients was 17.1 SD 5.13 micromol/L (range 6.4-31.3), and that in the controls was 9.0 SD 1.27 micromol/L (range 6.0-11.5). The association between elevated homocysteine levels and venous thrombosis was stronger among men than among women. CONCLUSIONS: The increased plasma homocysteine levels we have observed may have a causative role in the development of deep-vein thrombosis. 相似文献
997.
Frank Makowiec Stefan Post Hans-Detlev Saeger Norbert Senninger Heinz Becker Michael Betzler Heinz J. Buhr Ulrich T. Hopt German Advanced Surgical Treatment Study Group 《Journal of gastrointestinal surgery》2005,9(8):1080-1087
Despite decreasing mortality rates, morbidity is still high after pancreatic head resection. Comparative data in the United
States and Europe show a relationship between hospital volume and mortality. Treatment strategies vary frequently, partially
because of the lack of evidence-based data. We performed a multi-institutional analysis in Germany evaluating current numbers,
indications, techniques, and complication rates of pancreatic head resection. Questionnaires were completed by seven high-volume
surgical departments regarding quantitative and qualitative aspects of pancreatic head resections in the period from 1999
to 2004 (five prospective and two retrospective institutional databases). A total of 1454 pancreatic head resections (944
for malignancy) were reported. Mean annual hospital volume ranged from 14 to 52 (10 to 43 in malignancy). Mortality was between
1.1% and 4.8%, morbidity was between 24% and 46%, and pancreatic leakage was between 9% and 20%. In malignant disease, all
centers perform standard lymphadenectomy and regard arterial infiltration as a contraindication for resection. However, the
rate of portal vein resection varied from 0% to 28%. No consensus is seen on the type of surgery for malignancy and chronic
pancreatitis. After resection for pancreatic cancer less than one fourth of the patients receive adjuvant therapy. The results
of our analysis in Germany confirm that pancreatic head resection can be performed with low mortality in specialized units.
Variations in indications, operative technique, and perioperative care may demonstrate the lack of evidence-based data and/or
personal and institutional experience. The low number of patients receiving adjuvant therapy after resection of pancreatic
cancer suggests that more efforts must be made to establish novel adjuvant therapies under randomized study conditions.
Presented at the Forty-Sixth Annual Meeting of The Society for Surgery of the Alimentary Tract, Chicago, Illinois, May 14–18,
2005 (oral presentation). 相似文献
998.
Takahiko Misao Kanji Minamoto Hideharu Nakano Masataka Yamane Yosuke Yamamoto Katashi Satoh 《General thoracic and cardiovascular surgery》2005,53(6):309-312
A 64-year-old female was found to have localized ground-glass opacity (GGO) in the middle lobe on a chest computed tomography (CT) for screening. Middle lobectomy with video-assisted thoracoscopic surgery (VATS) was undertaken, and pathological diagnosis was a bronchioloalveolar carcinoma (BAC) in stage IA. A follow-up CT a year following the surgery revealed localized GGO in area S6 of the left lung. However, it disappeared during the gravitation-dependent gradient in the observation period. The patient was scanned again under prone position to exclude the gravitational effect, resulting in definite detection of the GGO. Left extended S6 segmentectomy with VATS was performed, and pathological diagnosis was a BAC in stage IA. As GGO existing in a gravitation-dependent area may be masked by the gravitation-dependent density, a change of the scanning position may lead to a proper detection of the tumor for the diagnosis of BAC. 相似文献
999.
1000.
G. Bonaspetti S. Di Fabio R. Fenu L. Costa U. E. Pazzaglia 《Journal of orthopaedics and traumatology》2005,6(1):15-20
Abstract
Polyethylene (PE) wear is a focal issue in joint replacement, so it is essential to understand how it takes place in vivo. PE wear is a multifactorial process with a complex interaction of variables related to the materials used, the mechanical conditions, operative procedures for implantation, activity of the patient and use of prosthesis. We retrieved 65 PE inserts with the respective femoral and tibial components (50 inserts of total knee prostheses and 15 monocompartmental prostheses) from first revision surgeries. The average age of the patients was 68.3 years; the average time to revision was 41.5 months. Macroscopic observation considered the grade, topography and type of wear. Degradation was also studied with scanning electron microscopy. No direct relationship was found between the level of wear and the survival of total or monocompartmental knee prostheses. The duration of 11 (22%) total prosthetic inserts with grade 2 wear was 42.6 months vs. 51.5 months of 17 (34%) total inserts with grade 1 wear. However, study of the relationship between wear grade and wear topography in total inserts suggested that there was a significant connection. In fact, the 22 (44%) prostheses with central and symmetrical wear never showed wear greater than grade 1. Instead, of the remaining 28 prostheses (56%) without central and symmetric wear, only 3 had grade 0 wear. Finally, considering the relationship between wear grade and type of wear, all 18 inserts (27.7%) with grade 2 or 3 wear had 100% delamination. In conclusion, this study suggests that the correct positioning of the prosthetic components, besides its quality, is an important cause of polyethylene wear. 相似文献