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   2173篇
  免费   106篇
  国内免费   7篇
耳鼻咽喉   21篇
儿科学   23篇
妇产科学   47篇
基础医学   261篇
口腔科学   96篇
临床医学   173篇
内科学   326篇
皮肤病学   15篇
神经病学   265篇
特种医学   233篇
外科学   431篇
综合类   10篇
一般理论   1篇
预防医学   78篇
眼科学   29篇
药学   132篇
中国医学   1篇
肿瘤学   144篇
  2023年   7篇
  2022年   28篇
  2021年   39篇
  2020年   32篇
  2019年   36篇
  2018年   58篇
  2017年   28篇
  2016年   43篇
  2015年   49篇
  2014年   65篇
  2013年   68篇
  2012年   128篇
  2011年   145篇
  2010年   89篇
  2009年   105篇
  2008年   139篇
  2007年   155篇
  2006年   140篇
  2005年   153篇
  2004年   134篇
  2003年   128篇
  2002年   130篇
  2001年   63篇
  2000年   54篇
  1999年   22篇
  1998年   24篇
  1997年   28篇
  1996年   9篇
  1995年   8篇
  1994年   8篇
  1993年   5篇
  1992年   11篇
  1991年   11篇
  1990年   10篇
  1989年   7篇
  1988年   8篇
  1986年   6篇
  1985年   8篇
  1984年   11篇
  1983年   9篇
  1982年   12篇
  1981年   6篇
  1980年   5篇
  1979年   4篇
  1975年   4篇
  1974年   9篇
  1973年   5篇
  1972年   5篇
  1970年   3篇
  1955年   3篇
排序方式: 共有2286条查询结果,搜索用时 15 毫秒
121.
122.
123.
BACKGROUND: Linear growth retardation and wasting are common in children born to HIV-infected women. Inexpensive interventions that could improve the postnatal growth pattern of such children are needed. OBJECTIVE: The objective was to examine the effect of supplementing HIV-infected women with multivitamins or vitamin A and beta-carotene, during and after pregnancy, on the growth of their children during the first 2 y of life. DESIGN: We conducted a randomized placebo-controlled trial in 886 mother-infant pairs in Tanzania. At the first prenatal visit, HIV-infected women were randomly assigned to 1 of 4 daily oral regimens in a 2 x 2 factorial fashion: multivitamins (MV: thiamine, riboflavin, vitamin B-6, niacin, vitamin B-12, vitamin C, vitamin E, and folic acid), preformed vitamin A + beta-carotene (VA/BC), MV including VA/BC, or placebo. Supplementation continued during the first 2 y postpartum and thereafter. Children were weighed and measured monthly, and all received vitamin A supplements after 6 mo of age per the standard of care. RESULTS: Multivitamins had a significant positive effect on attained weight (459 g; 95% CI: 35, 882; P = 0.03) and on weight-for-age (0.42; 95% CI: 0.07, 0.77; P = 0.02) and weight-for-length (0.38; 95% CI: 0.07, 0.68; P = 0.01) z scores at 24 mo. VA/BC seemed to reduce the benefits of MV on these outcomes. No significant effects were observed on length, midupper arm circumference, or head circumference. CONCLUSION: Supplementation of HIV-infected women with multivitamins (vitamin B complex, vitamin C, and vitamin E) during pregnancy and lactation is an effective intervention for improving ponderal growth in children.  相似文献   
124.
125.
BACKGROUND: Tissue factor pathway inhibitor (TFPI) is a multivalent Kunitz-type serine proteinase inhibitor which plays a central role in the extrinsic pathway of blood coagulation. A significant role of TFPI for the follicular development has been discussed in recent studies, and thrombotic complications during IVF procedure are a common problem. To elucidate the pathophysiological mechanisms underlying these problems, we have measured TFPI levels in human follicular fluid (hFF) of women undergoing in vitro fertilisation (IVF). METHODS: Total TFPI concentrations were determined in hFF of 28 women undergoing IVF treatment, 6 of whom developed an ovarian hyperstimulation syndrome (OHSS). RESULTS AND CONCLUSIONS: This is the first study to demonstrate an age-dependance of TFPI concentrations in hFF. Additionally, TFPI levels in hFF of women developing OHSS were determined as 323+/-66.8 ng/mL (mean+/-SD) in comparison with 279+/-137 ng/mL for non-OHSS patients. Our findings demonstrate that, unlike the decreased TFPI levels found in OHSS patients' blood, there is no statistically significant difference in hFF TFPI levels between OHSS and non-OHSS patients. Furthermore, we could show that the outcome of the IVF procedure is not correlated with TFPI levels in hFF.  相似文献   
126.
BACKGROUND: The most common opportunistic viral pathogen after lung transplantation is cytomegalovirus (CMV). Oral valganciclovir, a prodrug of ganciclovir, has been introduced as a potential drug for prophylaxis and treatment of CMV infection and disease in lung transplantation. The goal of this study was to describe our initial experience with oral valganciclovir for pre-emptive treatment of CMV infections after lung transplantation. METHODS AND PATIENTS: We summarize our experience with 19 patients who underwent lung transplantation and received pre-emptive oral valganciclovir therapy in the situation of positive CMV polymerase chain reaction (PCR) in either plasma or bronchoalveolar lavage. None of the patients presented with manifest CMV disease. Treatment dosage of valganciclovir was 450 mg to 1800 mg daily, depending on renal function and white blood count. Treatment was continued until the CMV PCR became negative, in any case for a period of at least 14 days. RESULTS: Three patients received two courses of pre-emptive oral valganciclovir; 16 patients were treated once. Eleven patients (57.9%) were treated because of a positive plasma CMV PCR; in eight patients (42.1%) the PCR was positive only in bronchoalveolar lavage. Therapy was initiated 896 +/- 1186 days (range, 108-3911) after transplantation with a mean CMV PCR of 45,536 +/- 149,294 copies (range, 426-706,000). In all cases the PCR fell below detectability (<400 copies) after a period of 22 +/- 10 days of treatment (range, 7-50 days). Mild to moderate leucopenia was observed in seven patients (36.8%) during treatment. None of the patients developed new onset of other potentially drug-related disorders such as neutropenia, anemia, deterioration of renal function or gastrointestinal disorder. CONCLUSIONS: Pre-emptive therapy with oral valganciclovir for CMV infections detected by PCR in either plasma or bronchoalveolar lavage after lung transplantation seems to be efficacious and safe. However, regular blood counts should be performed to detect developing leucopenia.  相似文献   
127.
The German short version of "Profile of Mood States" (POMS) was psychometrically tested in a representative sample (1009 subjects in Eastern Germany and 1034 subjects in Western Germany). The 35 items (7 point scale, instruction "How you have been feeling during the past 24 hours?") form the following scales: Depression/Anxiety, Fatigue, Vigor, Hostility. The POMS appears to be an internally consistent instrument (Cronbach's Alpha from 0.89 to 0.95). Replication of the postulated 4 factors was limited. There are hints for convergent validity of POMS-Scales using two questions: "1. Over the past two weeks, have you felt down, depressed, or helpless?" and "2. Over the past two weeks, have you felt little interest or pleasure in doing things?"  相似文献   
128.
RPGR-interacting protein 1 (RPGRIP1) is a key component of cone and rod photoreceptor cells, where it interacts with RPGR (retinitis pigmentosa GTPase regulator). Mutations in RPGRIP1 lead to autosomal recessive congenital blindness [Leber congenital amaurosis (LCA)]. Most LCA-associated missense mutations in RPGRIP1 are located in a segment that encodes two C2 domains. Based on the C2 domain of novel protein kinase C epsilon (PKC epsilon), we built a 3D-homology model for the C-terminal C2 domain of RPGRIP1. This model revealed a potential Ca2+-binding site that was predicted to be disrupted by a missense mutation in RPGRIP1, which was previously identified in an LCA patient. Through yeast two-hybrid screening of a retinal cDNA library, we found this C2 domain to specifically bind to nephrocystin-4, encoded by NPHP4. Mutations in NPHP4 are associated with nephronophthisis and a combination of nephronophthisis and retinitis pigmentosa called Senior-L?ken syndrome (SLSN). We show that RPGRIP1 and nephrocystin-4 interact strongly in vitro and in vivo, and that they colocalize in the retina, matching the panretinal localization pattern of specific RPGRIP1 isoforms. Their interaction is disrupted by either mutations in RPGRIP1, found in patients with LCA, or by mutations in NPHP4, found in patients with nephronophthisis or SLSN. Thus, we provide evidence for the involvement of this disrupted interaction in the retinal dystrophy of both SLSN and LCA patients.  相似文献   
129.
130.
INTRODUCTION: Late enhancement magnetic resonance imaging (MRI) of myocardial infarction (MI) is clinically established. There are no reports on MI assessment using state-of-the-art multislice CT technology. For this reason, animal experiments were conducted to examine the applicability of contrast-enhanced ECG-gated multislice computed tomography (MSCT) for the detection of acute MI. The results were correlated with MRI and postmortem tissue staining. MATERIAL AND METHODS: Acute MI was induced in 14 pigs by balloon occlusion of the LAD. In 8 animals, the LAD was reperfused after 45 minutes. In 6 animals, the LAD was permanently blocked. MR imaging was performed 15 minutes after the administration of 0.2 mmol Gd-DTPA/kg/bodyweight. Subsequently, 16-slice MSCT was performed at various timepoints after injecting 120 mL of iodinated contrast medium. 2,3,5-Triphenyltetrazolin-chloride (TTC) staining was acquired for all hearts investigated. Correlation analysis was applied to compare the area of MI derived from MRI, MSCT, and TTC. The reperfused infarcts were compared with the nonreperfused infarcts using an unpaired t test. RESULTS:: Mean infarct area as measured by TTC staining was 18.3% +/- 7.8% of the left ventricular area. Good correlation of the spatial extent of the infarcted area was found for TTC and MRI as well as for TTC and MSCT data obtained 5 minutes postcontrast injection. MSCT imaging demonstrated a significant difference in density (P < 0.001) between nonreperfused (47.0 +/- 6.6 HU) and reperfused (116.4 +/- 19.8 HU) infarction. CONCLUSION: In our pilot study, contrast-enhanced MSCT was feasible to assess myocardial viability in pigs. MSCT also affords differentiation of nonreperfused and reperfused acute MI. MI sizes derived from MSCT imaging correlate well to those obtained with MRI and TTC.  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