首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   10245篇
  免费   1410篇
  国内免费   426篇
耳鼻咽喉   16篇
儿科学   85篇
妇产科学   97篇
基础医学   810篇
口腔科学   250篇
临床医学   1032篇
内科学   1118篇
皮肤病学   19篇
神经病学   355篇
特种医学   622篇
外科学   3558篇
综合类   1627篇
预防医学   534篇
眼科学   5篇
药学   946篇
  6篇
中国医学   907篇
肿瘤学   94篇
  2024年   129篇
  2023年   369篇
  2022年   558篇
  2021年   536篇
  2020年   564篇
  2019年   481篇
  2018年   345篇
  2017年   340篇
  2016年   362篇
  2015年   324篇
  2014年   690篇
  2013年   855篇
  2012年   566篇
  2011年   623篇
  2010年   553篇
  2009年   501篇
  2008年   522篇
  2007年   467篇
  2006年   450篇
  2005年   401篇
  2004年   359篇
  2003年   320篇
  2002年   264篇
  2001年   304篇
  2000年   173篇
  1999年   167篇
  1998年   145篇
  1997年   117篇
  1996年   89篇
  1995年   71篇
  1994年   49篇
  1993年   54篇
  1992年   47篇
  1991年   34篇
  1990年   25篇
  1989年   28篇
  1988年   19篇
  1987年   22篇
  1986年   16篇
  1985年   25篇
  1984年   15篇
  1983年   13篇
  1982年   13篇
  1981年   11篇
  1980年   12篇
  1979年   12篇
  1978年   8篇
  1977年   12篇
  1976年   10篇
  1971年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
In vitro and in vivo studies suggest that carotenoids may inhibit bone resorption, yet no previous study has examined individual carotenoid intake (other than β‐carotene) and the risk of fracture. We evaluated associations of total and individual carotenoid intake (α‐carotene, β‐carotene, β‐cryptoxanthin, lycopene, lutein + zeaxanthin) with incident hip fracture and nonvertebral osteoporotic fracture. Three hundred seventy men and 576 women (mean age, 75 ± 5 yr) from the Framingham Osteoporosis Study completed a food frequency questionnaire (FFQ) in 1988–1989 and were followed for hip fracture until 2005 and nonvertebral fracture until 2003. Tertiles of carotenoid intake were created from estimates obtained using the Willett FFQ adjusting for total energy (residual method). HRs were estimated using Cox‐proportional hazards regression, adjusting for sex, age, body mass index, height, total energy, calcium and vitamin D intake, physical activity, alcohol, smoking, multivitamin use, and current estrogen use. A total of 100 hip fractures occurred over 17 yr of follow‐up. Subjects in the highest tertile of total carotenoid intake had lower risk of hip fracture (p = 0.02). Subjects with higher lycopene intake had lower risk of hip fracture (p = 0.01) and nonvertebral fracture (p = 0.02). A weak protective trend was observed for total β‐carotene for hip fracture alone, but associations did not reach statistical significance (p = 0.10). No significant associations were observed with α‐carotene, β‐cryptoxanthin, or lutein + zeaxanthin. These results suggest a protective role of several carotenoids for bone health in older adults.  相似文献   
992.
Short leukocyte telomere length (TL), low BMD, and osteoporosis have been associated with increased inflammation. Previous reports suggest an association between TL, BMD, and osteoporosis in women. We sought to verify these associations and to determine whether TL is related to fracture in a cohort of older men and women. Participants included 2750 community‐dwelling older persons from the longitudinal Health, Aging, and Body Composition Study (Health ABC) in who average leukocyte TL was measured at baseline using qPCR. We used unconditional logistic regression to determine the association of TL with prevalent fracture, Cox proportional hazards regression for the association with 7‐yr incident fracture, and mixed linear models for the association with BMD, change in BMD, and the number of incident fractures. TL was negatively correlated with age, weight, fasting insulin, and fasting glucose in men and women, and additionally, with C‐reactive protein and IL‐6 in men. TL was not associated with BMD; change in BMD over 1, 3, or 5 yr; osteoporosis; baseline fracture; or 7‐yr incident fracture, before or after adjustment for age, race, smoking, and health characteristics. TL is not associated with BMD, osteoporosis, or fracture in older men or women in this sample.  相似文献   
993.
The new U.S. National Osteoporosis Foundation Clinician's Guide to Prevention and Treatment of Osteoporosis includes criteria for recommending pharmacologic treatment based on history of hip or vertebral fracture, femoral neck (FN), or spine BMD T‐scores ≤?2.5 and presence of low bone mass at the FN or spine plus a 10‐yr risk of hip fracture ≥3% or of major osteoporotic fracture ≥20%. The proportion of women who would be recommended for treatment by these guidelines is not known. We applied the NOF criteria for treatment to women participating in the Study of Osteoporotic Fractures (SOF). To determine how the SOF population differs from the general U.S. population of white women ≥65 yr of age, we compared women in SOF with women who participated in the National Health and Nutrition Examination Survey (NHANES) III on criteria included in the NOF treatment guidelines that were common to both cohorts. Compared with NHANES III, women in SOF had higher FN BMD and were younger. Application of NOF guidelines to SOF data estimated that at least 72% of U.S. white women ≥65 yr of age and 93% of those ≥75 yr of age would be recommended for drug treatment. Application of the new NOF Guidelines would result in recommending a very large proportion of white women in the United States for pharmacologic treatment of osteoporosis.  相似文献   
994.
Vertebral fractures are the most common osteoporotic fracture, and patients with prevalent vertebral fractures have a greater risk of future fractures. However, radiographically determined vertebral fractures are not identified as a distinct risk factor in the World Health Organization (WHO) fracture risk assessment tool. The objective of this study was to evaluate and compare potential risk factors including morphometric spine fracture status and the WHO risk factors for predicting 5‐yr fracture risk. We hypothesized that spine fracture status provides prognostic information in addition to consideration of the WHO risk factors alone. A randomly selected, population‐based community cohort of 2761 noninstitutionalized men and women ≥50 yr of age living within 50 km of one of nine regional centers was enrolled in the Canadian Multicentre Osteoporosis Study (CaMOS), a prospective and longitudinal cohort study following subjects for 5 yr. Prevalent and incident spine fractures were identified from lateral spine radiographs. Incident nonvertebral fragility fractures were determined by an annual, mailed fracture questionnaire with validation, and nonvertebral fragility fracture was defined by investigators as a fracture with minimal trauma. A model considering the WHO risk factors plus spine fracture status provided greater prognostic information regarding future fracture risk than a model considering the WHO risk factors alone. In univariate analyses, age, BMD, and spine fracture status had the highest gradient of risk. A model considering these three risk factors captured almost all of the predictive information provided by a model considering spine fracture status plus the WHO risk factors and provided greater predictive information than a model considering the WHO risk factors alone. The use of spine fracture status along with age and BMD predicted future fracture risk with greater simplicity and higher prognostic accuracy than consideration of the risk factors included in the WHO tool.  相似文献   
995.
The vertebral hydatidosis is uncommon. It causes problems in diagnosis and in management. A case of an extensive vertebral hydatidosis with few symptoms is reported. A 21-year-old man has consulted for recurrent lumbosciatica that has been evolving for 1 year. Clinical exam was normal. Plain radiographic films disclosed a lytic lesion throughout the bodies of L4 and L5 and calcifications thrown on the liver area. The computed tomography (CT) and the magnetic resonance (MR) images revealed multicystic bony lesions involving the lumbar spine with extension into the spinal canal. Abdominal ultrasound showed also cyst lesions in the right kidney and in the liver. The diagnosis of vertebral and abdominal (liver and kidney) hydatidosis was retained. Four sets of 4-week albendazole cures were given with a 2-week interval in between. Our case of extended vertebral hydatidosis with few symptoms confirms the clinical latency and diagnosis difficulties usually encountered in this disease. This often leads to a late diagnosis of the stage of spinal cord compression. Radiological diagnosis and determination of extension of the hydatid cyst are usually provided by CT and MRI. Vertebral hydatidosis should be evoked in lumbosciatica especially in endemic regions.  相似文献   
996.

Objective

We examined anthropometric indicators to improve predictive ability of asymptomatic vertebral fracture screening models.

Study design and setting

Data were obtained from the 1996 Japanese Population-based Osteoporosis (JPOS) Study. McCloskey–Kanis criteria diagnosed vertebral deformities on X-ray absorptiometric images in 693 women aged ≥50.The multiple logistic regression model included age, height, weight, postmenopausal status, total hip BMD, and arm span (AS) or sitting height as explanatory variables. Akaike's information criterion (AIC) evaluated model goodness-of-fit.

Results

Age-adjusted AS and sitting height in subjects with and without vertebral deformities were 147.2 ± 0.6 cm and 148.5 ± 0.2 cm (P = 0.055), 78.5 ± 0.5 cm and 79.9 ± 0.2 cm (P = 0.007), respectively. Every 5-cm increase in AS indicated 1.5-fold increased risk of prevalent vertebral deformity in the model including age, height, weight, postmenopausal status, and BMD. Including the explanatory variable AS in models yielded better predictive accuracy than excluding AS (AIC, 441.7 vs 446.6, respectively). Sitting height did not significantly influence model predictive ability.

Conclusion

Predictive accuracy of model for vertebral fracture including age, height, weight, postmenopausal status, and BMD improved when AS was added as an explanatory variable. Models to screen for asymptomatic vertebral fractures should include AS.  相似文献   
997.
地塞米松对大鼠腰椎骨质量的影响   总被引:1,自引:1,他引:0  
目的观察地塞米松(Dex)对大鼠腰椎骨质量的影响。方法 SPF级3月龄SD雌性大鼠,每周尾静脉注射Dex 12,.5及5 mg.kg-1 2次,共8周。在实验结束前第14,13天和第4,3天分别sc四环素和钙黄绿素荧光标记。实验结束时处死大鼠后取材,采用不脱钙骨切片和骨组织形态计量学方法观察和测量第4腰椎骨的显微结构参数;骨密度仪测量第3腰椎的骨矿密度;采用生物力学方法进行第5腰椎的压缩力学检测。结果与正常对照组相比,所有Dex组体重明显下降,分别下降了14.8%,16.6%和18.0%(P<0.05)。骨矿含量和压缩力学检测变化与正常对照组无明显统计学差异。骨小梁数量分别增加了17.2%,13.3%和9.0%,分离度分别减小了19.2%,16.7%和15.1%(P<0.05),但镜下观察看到小梁细碎,断裂点多且分布不均。动态参数荧光周长百分率明显下降,Dex 1,2.5和5 mg.kg-1组分别降低49.5%,62.4%和73.2%(P<0.01);骨形成率分别降低47.0%,66.8%和76.7%(P<0.01);成骨细胞周长也分别降低了20.0%,49.3%和43.6%(P<0.05,P<0.01)。结论 Dex显著抑制骨形成,骨代谢的失衡致骨的组织成分改变,三维结构变差,但腰椎骨质量还没有明显下降。  相似文献   
998.
This study was performed to discover a novel herbal therapeutic for effective glucocorticoid-induced osteoporosis (GIO) treatment and further to clarify its molecular mechanism of action. Ethanol or methanol extracts of 68 edible Korean native plants were screened to find effective natural plant sources for the treatment of GIO, and Poncirus trifoliata (L.) (Rutaceae, PT) was selected as a final candidate because of its high inhibitory activity plus its novelty. The hexane extract of PT (PT-H) inhibited apoptotic cell death in dexamethasone-induced osteoblastic cell lines, C3H10T1/2 and MC3T3-E1. In vivo mouse results indicated that PT-H not only had an inhibitory effect on the bone loss caused by glucocorticoid, but also promoted bone formation. The molecular mechanisms behind the effect of PT-H on GIO were further clarified by screening of differentially expressed genes (DEGs) between dexamethasone (Dex)-induced osteoblastic cells with or without PT-H treatment. Finally, it was found that the expression level of AnxA6 in Dex-induced osteoblastic cells and prednisolone (PD)-treated GIO-model mice was significantly decreased by PT-H treatment. These findings suggest that PT-H has a strong in vitro and in vivo inhibitory effect on GIO, and decreased expression of AnxA6 may play a key role in this inhibition.  相似文献   
999.
1000.
Background:  According to several guidelines, the assessment of postmenopausal fracture risk should be based on clinical risk factors (CRFs) and bone density. Because measurement of bone density by dual x-ray absorptiometry (DXA) is quite expensive, there has been increasing interest to estimate fracture risk by CRFs.
Objective:  The aim of this study was to determine the cost-effectiveness of osteoporosis screening of CRFs with and without DXA compared with no screening in postmenopausal women in Germany.
Methods:  A cost-utility analysis and a budget-impact analysis were performed from the perspective of the statutory health insurance. A Markov model simulated costs and benefits discounted at 3% over lifetime.
Results:  Cost-effectiveness of CRFs compared with no screening is €4607, €21,181, and €10,171 per quality-adjusted life-year (QALY) for 60-, 70-, and 80-year-old women, respectively. Cost-effectiveness of DXA plus CRFs compared with CRFs alone is €20,235 for 60-year-old women. In women above the age of 70, DXA plus CRFs dominates CRFs alone. DXA plus CRFs results in annual costs of €175 million, or 0.4% of the statutory health insurance's annual budget.
Conclusion:  Funders should be careful in adopting a strategy based on CRFs alone instead of DXA plus CRFs. Only if DXA is not available, assessing CRFs only is an acceptable option in predicting a woman's risk of fracture.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号