全文获取类型
收费全文 | 931篇 |
免费 | 36篇 |
国内免费 | 3篇 |
专业分类
耳鼻咽喉 | 11篇 |
儿科学 | 128篇 |
妇产科学 | 16篇 |
基础医学 | 116篇 |
口腔科学 | 7篇 |
临床医学 | 67篇 |
内科学 | 165篇 |
皮肤病学 | 7篇 |
神经病学 | 23篇 |
特种医学 | 11篇 |
外科学 | 150篇 |
综合类 | 25篇 |
预防医学 | 39篇 |
眼科学 | 23篇 |
药学 | 116篇 |
中国医学 | 5篇 |
肿瘤学 | 61篇 |
出版年
2023年 | 5篇 |
2022年 | 14篇 |
2021年 | 30篇 |
2020年 | 16篇 |
2019年 | 14篇 |
2018年 | 36篇 |
2017年 | 34篇 |
2016年 | 30篇 |
2015年 | 35篇 |
2014年 | 46篇 |
2013年 | 45篇 |
2012年 | 73篇 |
2011年 | 69篇 |
2010年 | 43篇 |
2009年 | 59篇 |
2008年 | 57篇 |
2007年 | 53篇 |
2006年 | 56篇 |
2005年 | 41篇 |
2004年 | 61篇 |
2003年 | 35篇 |
2002年 | 28篇 |
2001年 | 13篇 |
2000年 | 4篇 |
1999年 | 4篇 |
1998年 | 6篇 |
1997年 | 10篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 7篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 2篇 |
1982年 | 3篇 |
1980年 | 4篇 |
1976年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1902年 | 2篇 |
排序方式: 共有970条查询结果,搜索用时 15 毫秒
71.
Maternal and obstetric risk factors for sudden infant death syndrome in the United States 总被引:4,自引:0,他引:4
OBJECTIVE: The objectives of this study were to 1). study the incidence of sudden infant death syndrome (SIDS) among singleton births in the United States and 2). identify maternal and obstetric risk factors for SIDS. METHODS: A cohort of all live births in the United States from 1995 to 1998, formed the source population (n = 15627404). The data were obtained from the National Centers for Health Statistics Linked Births and Infant Deaths File. A nested case-control study was used to examine risk factors for SIDS. From this birth cohort, all SIDS deaths (n = 12404) were first identified (case group). From the remaining non-SIDS births, a 4-fold larger sample (n = 49616) was randomly selected as a control group. RESULTS: The overall incidence of SIDS was 81.7 per 100000 live births. More mothers in the case group than in the control group were reported to have placenta previa (odds ratio [OR]: 1.70; 95% confidence interval [CI] 1.24, 2.33), abruptio placentae (OR 1.57; 95% CI 1.24, 1.98), premature rupture of membranes (OR 1.48; 95% CI 1.33, 1.66), or small for gestational age (OR 1.40; 95% CI 1.30, 1.50 for the 10th percentile). SIDS cases were also more likely to be male. Mothers of cases were more likely to be younger, less educated, and nonwhite, and more of them smoked during pregnancy and did not attend prenatal care. CONCLUSION: This analysis confirms the importance of several well known demographic and lifestyle risk factors for SIDS. In addition, placental abnormalities were risk factors for SIDS. LEVEL OF EVIDENCE: II-2 相似文献
72.
73.
74.
Duplications of the esophagus are the second most common duplication of the gastrointestinal tract. The children with esophageal duplication cyst usually present with respiratory distress or as asymptomatic thoracic mass found on incidental chest x-ray. We report a case of infected esophageal duplication cyst initially confused with empyema in a two years old boy. 相似文献
75.
Hirayama disease causes unilateral or asymmetrical bilateral distal weakness and atrophy of upper limbs. We report a 6 1/2-year-old female with Hirayama disease and associated high serum lead levels. This report highlights the occurrence of this condition in younger children and the need to further study the role of lead in its pathophysiology. 相似文献
76.
77.
The incidence and prevalence of Crohn's disease (CD) among children in developed countries is extremely high. Although, dietary factors have long been implicated, to date no single causative element has been identified. Risks or benefits for CD from dietary elements would depend on their appropriate metabolism within the gut by xenobiotic metabolising enzymes (XME). The metabolising capacity among individuals differs and is determined by the level and/or activity of the specific XME. As the latter is the function of the DNA variants that code them, we propose that certain individuals exposed to dietary elements are likely to be more or less susceptible for CD. We highlight this hypothesis by describing gene-environment interaction (GxE) mechanisms that could determine susceptibility for CD. We suggest that investigating these mechanisms will be paramount for the appropriate identification of susceptible populations, such that preventive and/or therapeutic interventions could be adequately targeted. 相似文献
78.
BACKGROUND: We have used a laminoplasty technique in multilevel cervical canal stenosis that incorporates spinous process in the neural arch and does not require free graft or foreign material. METHODS:In this technique, laminae and spinous processes were used to enlarge stenotic cervical spinal canal. Three patients (mean age 34.6 years) formed the study group with a mean follow-up period of 24.6 months. Postoperative computed tomography (CT) and lateral radiographs were used to assess results in terms of bony union, canal diameter, and alignment of cervical spine. RESULTS: All patients noted some improvement in both sensory and motor functions. The average increase in sagittal diameter of cervical spinal canal was 4.2 mm, and decrease in range of motion (ROM) was 13.2 degrees. Bony fusions at the gutters were seen after 6 months. CONCLUSION: This new technique of cervical laminoplasty is safe, effective, relatively easy, and avoids complications related to free grafts or metallic or nonmetallic foreign materials used in other techniques 相似文献
79.
The purpose of this work was to obtain information about protein tertiary structure in solid state by using steady state tryptophan (Trp) fluorescence emission spectroscopy on protein powders. Beta-lactoglobulin (betaLg) and interferon alpha-2a (IFN) powder samples were studied by fluorescence spectroscopy using a front surface sample holder. Two different sets of dried betaLg samples were prepared by vacuum drying of solutions: one containing betaLg, and the other containing a mixture of betaLg and guanidine hydrochloride. Dried IFN samples were prepared by vacuum drying of IFN solutions and by vacuum drying of polyethylene glycol precipitated IFN. The results obtained from solid samples were compared with the emission scans of these proteins in solutions. The emission scans obtained from protein powders were slightly blue-shifted compared to the solution spectra due to the absence of water. The emission scans were red-shifted for betaLg samples dried from solutions containing GuHCl. The magnitude of the shifts in lambda(max) depended on the extent of drying of the samples, which was attributed to the crystallization of GuHCl during the drying process. The shifts in the lambda(max) of the Trp emission spectrum are associated with the changes in the tertiary structure of betaLg. In the case of IFN, the emission scans obtained from PEG-precipitated and dried sample were different compared to the emission scans obtained from IFN in solution and from vacuum dried IFN. The double peaks observed in this sample were attributed to the unfolding of the protein. In the presence of trehalose, the two peaks converged to form a single peak, which was similar to solution emission spectra, whereas no change was observed in the presence of mannitol. We conclude that Trp fluorescence spectroscopy provides a simple and reliable means to characterize Trp microenvironment in protein powders that is related to the tertiary conformation of proteins in the solid state. This study shows that the use of fluorescence spectroscopy of proteins can be extended from simple protein aqueous solutions to protein powders, precipitates, and semidried protein samples to gain understanding of protein tertiary structure in these physical states. 相似文献
80.
Calphostin C as a rapid and strong inducer of apoptosis in human coronary artery smooth muscle cells
Krueger KD Hunter WJ DelCore MG Agrawal DK 《International immunopharmacology》2003,3(13-14):1751-1759
Vascular smooth muscle cells (VSMCs) play a major role in the development of atherosclerotic and restenotic lesions. The apoptotic process has been implicated in the development of this pathology. In this study, we characterized the induction of apoptosis by calphostin C (CC), a protein kinase C (PKC) inhibitor, in primary human coronary artery smooth muscle cells in the presence and absence of insulin-like growth factor-I (IGF-I). Additionally, we investigated the signal transduction pathways important for IGF-I mediated protection. Calphostin C induced apoptosis, as measured by terminal deoxy-UTP nick-end labeling (TUNEL), in a time- and dose-dependent manner, approaching 20% within 6 h of 50 nM calphostin C treatment. The amount of apoptosis increased to 44.58+/-8.08%, 47.54+/-1.66% and 78.1+/-11.9% after 8, 10 and 12 h of treatment, respectively (p<0.01 vs. control). IGF-I offered significant protection (p<0.05) at 8 and 10 h of treatment (60.6% and 52.5% protection, respectively). DNA ELISA confirmed the apoptotic effect of calphostin C and the protective effect of IGF-I. After 6 h of calphostin C treatment, DNA ELISA revealed 11.20+/-1.53 fold greater apoptosis as compared to baseline values. IGF-I treatment offered a level of protection of 46.6% as measured by DNA ELISA (p=0.06). Apoptosis was further qualitatively confirmed by time-lapse video microscopy and scanning electron microscopy. Interestingly, inhibitors of phosphatidylinositol-3-kinase (PI-3-K), p38 and extracellular regulated kinase (ERK) activation significantly (p<0.05 vs. calphostin C only treatment) increased apoptosis when used in conjunction with calphostin C. Inhibitors of phospatidylinositol-3-kinase and ERK activation reversed IGF-I protection. However, the p38 inhibitor SB203580 failed to reverse IGF-I protection. This study characterized an apoptotic system for human coronary artery smooth muscle cells offering a rapid and strong induction of programmed cell death (PCD) that remains responsive to the survival effects of IGF-I. Studies utilizing this system may prove useful in understanding the apoptotic response of VSMCs in the arterial wall. 相似文献