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   4391篇
  免费   257篇
  国内免费   53篇
耳鼻咽喉   69篇
儿科学   43篇
妇产科学   119篇
基础医学   719篇
口腔科学   182篇
临床医学   474篇
内科学   901篇
皮肤病学   56篇
神经病学   312篇
特种医学   286篇
外科学   481篇
综合类   94篇
一般理论   1篇
预防医学   264篇
眼科学   41篇
药学   312篇
中国医学   53篇
肿瘤学   294篇
  2023年   21篇
  2022年   88篇
  2021年   159篇
  2020年   70篇
  2019年   107篇
  2018年   125篇
  2017年   94篇
  2016年   138篇
  2015年   181篇
  2014年   221篇
  2013年   262篇
  2012年   419篇
  2011年   351篇
  2010年   190篇
  2009年   157篇
  2008年   242篇
  2007年   248篇
  2006年   240篇
  2005年   201篇
  2004年   142篇
  2003年   148篇
  2002年   144篇
  2001年   107篇
  2000年   120篇
  1999年   63篇
  1998年   27篇
  1997年   20篇
  1996年   19篇
  1995年   9篇
  1994年   13篇
  1993年   9篇
  1992年   30篇
  1991年   29篇
  1990年   27篇
  1989年   24篇
  1988年   22篇
  1987年   34篇
  1986年   33篇
  1985年   8篇
  1984年   12篇
  1983年   19篇
  1982年   9篇
  1981年   11篇
  1980年   6篇
  1979年   11篇
  1978年   12篇
  1974年   13篇
  1972年   14篇
  1970年   6篇
  1965年   6篇
排序方式: 共有4701条查询结果,搜索用时 15 毫秒
31.
32.
OBJECTIVES: To estimate the combined screening performance of first and early second trimester prenatal serum markers for Down syndrome, in screening for the development of preeclampsia, and analyze the correlation among marker levels, week of onset, and severity of the disease. METHODS: A retrospective cohort study was carried out on 32 women with preeclampsia and 3044 controls. Serum samples from these pregnancies were assayed for pregnancy-associated plasma protein-A (PAPP-A), alpha-fetoprotein (AFP), unconjugated estriol (uE3), human chorionic gonadotrophin (hCG), and inhibin-A. A likelihood ratio and the odds of being affected given a positive result (OAPR) of various combinations of markers were calculated and receiver operating characteristic (ROC) curves analysis was performed. RESULTS: In the pregnancies that subsequently developed preeclampsia, first trimester PAPP-A concentration was significantly lower and concentrations of early second trimester inhibin-A and hCG significantly elevated. Levels of early second trimester uE3 and AFP were not significantly altered. We also found that inhibin-A correlates with both onset of the disease and the severity. CONCLUSION: Down syndrome biochemical markers levels are altered in those patients who subsequently developed preeclampsia and may be a useful screening test for preeclampsia. Inhibin-A is the most predictive marker and correlates with the severity of subsequent preeclampsia and inversely with the week of occurrence of preeclampsia.  相似文献   
33.
34.
BACKGROUND: Vitamin A (retinol), which is required for normal fetal development and successful gestation, circulates in the blood bound to a specific protein, the retinol binding protein (RBP). Little is known about the transport and metabolism of this complex protein or about retinol status during normal human pregnancy. OBJECTIVE: The aim of this study was to assess retinol status and transport modalities of retinol in well-nourished women with normal pregnancies, a population poorly investigated compared with pathologic and malnourished pregnant women. DESIGN: The maternal blood and cord blood concentrations of retinol, vitamin E, beta-carotene, RBP, and transthyretin of pregnant French women at term (n = 27) were measured and compared with values from a nonpregnant control group (n = 27). In addition, holo-RBP (retinol bound), apo-RBP (retinol free), and total protein were assessed in both groups to enable the hemodilution occurring during pregnancy to be taken into consideration and to evaluate the extent of saturation of RBP with retinol. RESULTS: Healthy pregnant women at term had normal serum circulatory amounts of retinol, vitamin E, binding proteins, and beta-carotene. However, they had less binding of retinol to RBP (holo-RBP: 49.9% in pregnant women, 54.0% in cord blood, and 77.5% in the control group). CONCLUSION: The results of this study suggest that retinol homeostasis and transport are modified during normal human pregnancy.  相似文献   
35.
PurposeTo date, no study has compared the effects of adding sodium glucose cotransporter-2 (SGLT-2) inhibitors to the combination of metformin plus dipeptidyl peptidase-4 (DPP-4) inhibitors to the effects of adding other conventional anti-diabetic drugs (ADDs) to the dual therapy. We aimed to compare the effect of adding SGLT-2 inhibitors with that of adding sulfonylurea (SU) in type 2 diabetes (T2D) patients inadequately controlled with metformin plus DPP-4 inhibitors.Materials and MethodsThis study was designed to evaluate the non-inferiority of SGLT-2 inhibitor to SU as an add-on therapy to the dual combination of metformin plus DPP-4 inhibitors. A total of 292 T2D patients who started SU or SGLT-2 inhibitors as an add-on therapy to metformin plus DPP-4 inhibitors due to uncontrolled hyperglycemia, defined as glycated hemoglobin (HbA1c) ≥7%, were recruited. After propensity score matching, 90 pairs of patients remained, and 12-week changes in HbA1c levels were reviewed to assess glycemic effectiveness. Data from these patients were analyzed retrospectively.ResultsAfter 12 weeks of triple therapy, both groups showed significant changes in HbA1c levels, with a mean of -0.9% in each group. The inter-group difference was 0.01% [95% confidence interval (CI): -0.26–0.27], and the upper limit of the 95% CI was within the limit for non-inferiority (0.40%). There were no inter-group differences in the changes of liver enzyme levels and kidney function.ConclusionAdding SGLT-2 inhibitors is not inferior to adding SU as a third-line ADD to metformin plus DPP-4 inhibitor combination therapy.  相似文献   
36.
乙型肝炎疫苗免疫效果影响因素分析   总被引:5,自引:0,他引:5  
目的探讨乙肝疫苗免疫效果的影响因素。方法选择正定县乙肝疫苗效果考核试点乡1986-2004年出生的人群为研究对象,以固相放射免疫(RIA)法检测血清HBsAg、抗-HBs和抗-HBc,用EpiInfo和SAS软件进行统计处理。结果1994年及以后出生的1~11岁组人群HBsAg、抗-HBc分别为0.41%、2.29%,显著低于1994年前出生的12~19岁组人群的2.18%和8.44%;乙肝疫苗3针全程免疫组人群HBsAg阳性率最低,为0.35%;44例HBsAg阳性者中,母亲HBsAg阳性者21例,占47.73%。结论母亲HBsAg携带状况和乙肝疫苗接种史是影响乙肝疫苗免疫效果的关键因素。  相似文献   
37.
ObjectiveTo evaluate the feasibility of single-shot whole thoracic time-resolved MR angiography (TR-MRA) to identify the feeding arteries of pulmonary arteriovenous malformations (PAVMs) and reperfusion of the lesion after embolization in patients with multiple PAVMs.Materials and MethodsNine patients (8 females and 1 male; age range, 23–65 years) with a total of 62 PAVMs who underwent percutaneous embolization for multiple PAVMs and were subsequently followed up using TR-MRA and CT obtained within 6 months from each other were retrospectively reviewed. All imaging analyses were performed by two independent readers blinded to clinical information. The visibility of the feeding arteries on maximum intensity projection (MIP) reconstruction and multiplanar reconstruction (MPR) TR-MRA images was evaluated by comparing them to CT as a reference. The accuracy of TR-MRA for diagnosing reperfusion of the PAVM after embolization was assessed in a subgroup with angiographic confirmation. The reliability between the readers in interpreting the TR-MRA results was analyzed using kappa (κ) statistics.ResultsFeeding arteries were visible on the original MIP images of TR-MRA in 82.3% (51/62) and 85.5% (53/62) of readers 1 and 2, respectively. Using the MPR, the rates increased to 93.5% (58/62) and 95.2% (59/62), respectively (κ = 0.760 and 0.792, respectively). Factors for invisibility were the course of feeding arteries in the anteroposterior plane, proximity to large enhancing vessels, adjacency to the chest wall, pulsation of the heart, and small feeding arteries. Thirty-seven PAVMs in five patients had angiographic confirmation of reperfusion status after embolization (32 occlusions and 5 reperfusions). TR-MRA showed 100% (5/5) sensitivity and 100% (32/32, including three cases in which the feeding arteries were not visible on TR-MRA) specificity for both readers.ConclusionSingle-shot whole thoracic TR-MRA with MPR showed good visibility of the feeding arteries of PAVMs and high accuracy in diagnosing reperfusion after embolization. Single-shot whole thoracic TR-MRA may be a feasible method for the follow-up of patients with multiple PAVMs.  相似文献   
38.
We present a case of developmental venous anomaly associated with arteriovenous fistula supplied by a single arterial feeder adjacent to a large acute intracerebral hemorrhage. The arteriovenous fistula was successfully obliterated by superselective embolization while completely preserving the developmental venous anomaly. Two similar cases, including superselective angiographic findings, have been reported in the literature; however, we describe herein superselective angiographic findings in more detail and demonstrate the arteriovenous shunt more clearly than the previous reports. In addition, a literature review was performed to discuss the association of a developmental venous anomaly with vascular lesions.  相似文献   
39.
Iterative decomposition of water and fat with echo asymmetry and the least-squares estimation (IDEAL) is a recently developed method for robust separation of fat and water with very high signal-to-noise-ratio (SNR) efficiency. In contrast to conventional fat-saturation methods, IDEAL is insensitive to magnetic field (B0 and B1) inhomogeneity. The aim of this study was to illustrate the practical application of the IDEAL technique in reducing metallic artifacts in postoperative patients with metallic hardware. The IDEAL technique can help musculoskeletal radiologists make an accurate diagnosis particularly in musculoskeletal imaging by reducing metallic artifacts, enabling the use of contrast enhancement, improving SNR performance, and providing various modes of MR images with one scan parameter.  相似文献   
40.
Objectives To investigate the magnitude and characteristics of the economic burden resulting from acute pesticide poisoning (APP) in South Korea. Methods The total costs of APP from a societal perspective were estimated by summing the direct medical and non‐medical costs together with the indirect costs. Direct medical costs for patients assigned a disease code of pesticide poisoning were extracted from the Korean National Health Insurance Reimbursement Data. Direct non‐medical costs were estimated using the average transportation and caregiving costs from the Korea Health Panel Survey. Indirect costs, incurred by pre‐mature deaths and work loss, were obtained using 2009 Life Tables for Korea and other relevant literature. Results In 2009, a total of 11 453 patients were treated for APP and 1311 died, corresponding to an incidence of 23.1 per 100 000 population and a mortality rate of 2.6 per 100 000 population in South Korea. The total costs of APP were estimated at approximately US$ 150 million, 0.3% of the costs of total diseases. Costs due to pre‐mature mortality accounted for 90.6% of the total costs, whereas the contribution of direct medical costs was relatively small. Conclusion Costs from APP demonstrate a unique characteristic of a large proportion of the indirect costs originating from pre‐mature mortality. This finding suggests policy implications for restrictions on lethal pesticides and safe storage to reduce fatality and cost due to APP.  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