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   24968篇
  免费   2553篇
  国内免费   2030篇
耳鼻咽喉   209篇
儿科学   257篇
妇产科学   364篇
基础医学   3212篇
口腔科学   506篇
临床医学   3345篇
内科学   3684篇
皮肤病学   193篇
神经病学   1467篇
特种医学   984篇
外国民族医学   14篇
外科学   2630篇
综合类   4073篇
现状与发展   8篇
一般理论   4篇
预防医学   1556篇
眼科学   599篇
药学   2791篇
  14篇
中国医学   1495篇
肿瘤学   2146篇
  2024年   26篇
  2023年   370篇
  2022年   589篇
  2021年   1173篇
  2020年   1000篇
  2019年   905篇
  2018年   875篇
  2017年   872篇
  2016年   764篇
  2015年   1172篇
  2014年   1542篇
  2013年   1271篇
  2012年   1888篇
  2011年   1962篇
  2010年   1282篇
  2009年   990篇
  2008年   1408篇
  2007年   1341篇
  2006年   1285篇
  2005年   1393篇
  2004年   933篇
  2003年   921篇
  2002年   729篇
  2001年   590篇
  2000年   644篇
  1999年   658篇
  1998年   427篇
  1997年   385篇
  1996年   326篇
  1995年   317篇
  1994年   279篇
  1993年   184篇
  1992年   207篇
  1991年   173篇
  1990年   141篇
  1989年   101篇
  1988年   105篇
  1987年   73篇
  1986年   77篇
  1985年   56篇
  1984年   34篇
  1983年   27篇
  1982年   12篇
  1981年   9篇
  1980年   8篇
  1979年   10篇
  1978年   3篇
  1977年   4篇
  1975年   2篇
  1929年   2篇
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
51.
The susceptibility and severity of periodontal diseases is made more severe by diabetes, with the impact on the disease process inversely proportional to the level of glycemic control. Although type 1 diabetes mellitus and type 2 diabetes mellitus have different etiologies, and their impact on bone is not identical, they share many of the same complications. Studies in animals and humans agree that both forms of diabetes increase inflammatory events in periodontal tissue, impair new bone formation, and increase expression of RANKL in response to bacterial challenge. High levels of glucose, reactive oxygen species, and advanced glycation end-products are found in the periodontium of diabetic individuals and lead to increased activation of nuclear factor-kappa B and expression of inflammatory cytokines such as tumor necrosis factor and interleukin-1. Studies in animals, moreover, suggest that there are multiple cell types in periodontal tissues that are affected by diabetes, including leukocytes, vascular cells, mesenchymal stem cells, periodontal ligament fibroblasts, osteoblasts, and osteocytes. The etiology of periodontal disease involves the host response to bacterial challenge that is affected by diabetes, which increases the expression of RANKL and reduces coupled bone formation. In addition, the inflammatory response also modifies the oral microbiota to render it more pathogenic, as demonstrated by increased inflammation and bone loss in animals where bacteria are transferred from diabetic donors to germ-free hosts compared with transfer from normoglycemic donors. This approach has the advantage of not relying upon limited knowledge of the specific bacterial taxa to determine pathogenicity, and examines the overall impact of the microbiota rather than the presumed pathogenicity of a few bacterial groups. Thus, animal studies have provided new insights into pathogenic mechanisms that identify cause-and-effect relationships that are difficult to perform in human studies.  相似文献   
52.
ObjectivesTo investigate the effect of corneal stromal pocket irrigation after small-incision lenticule extraction (SMILE) on visual acuity, intraocular pressure (IOP), corneal parameters and complications after surgery.MethodsA total of 242 eyes of 121 patients undergoing SMILE were enrolled in this prospective controlled study, and it was designed for one eye to randomly undergo SMILE with balanced salt solution irrigation of the corneal stromal pocket, while the other eye was not. The uncorrected distance visual acuity (UDVA) and slit lamp examination were recorded at 1 hour, 1 day, 1 week, and 1 month. Postoperative corneal density, corneal biomechanical, corneal endothelial cell number, and anterior OCT images were compared at 1 day, 1 week, and 1 month.ResultsCompared with the nonirrigation group, the irrigation group showed significantly higher UDVA at 1 day postoperatively (P < 0.05), but there was no significant difference during the rest of the postoperative period (1 hour, 1 week, and 1 month). In addition, no significant differences were found in IOP, corneal density, corneal biomechanics, corneal endothelial cells, and corneal morphology. No visual decline or severe postoperative complications were found in the patients in this study.ConclusionsInterlamellar irrigation did not affect IOP, corneal parameters, morphology, complications, or UDVA at 1 hour, 1 week, and 1 month after the operation, but it may promote UDVA 1 day after the operation.Subject terms: Refractive errors, Outcomes research, Surgery  相似文献   
53.
54.
自身免疫性胶质纤维酸性蛋白星形胶质细胞病是一种可治的中枢神经系统自身免疫性炎性疾病,以脑膜、脑、脊髓和视神经等受累为主要表现,磁共振成像可见脑室旁线样放射状强化和(或)脊髓长节段受累伴中央强化病灶,脑活体组织检查提示小血管周围炎症伴小胶质细胞活化,对类固醇激素治疗敏感.胶质纤维酸性蛋白抗体被认为是本病的特异性生物标志物.  相似文献   
55.
目的探讨磁共振成像(MRI)阴性颞叶癫痫(nonlesional temporal lobe epilepsy,TLE-NL)患者的临床特征、记忆水平和影像学特点。方法纳入2012年9月1日至2017年8月31日在浙江大学医学院附属第二医院确诊的44例单侧TLE-NL患者和53例同期就诊单侧颞叶癫痫伴海马硬化(temporal lobe epilepsy with hippocampal sclerosis,TLE-HS)患者,对TLE-NL和TLE-HS的临床特点进行对比。同时纳入20名健康志愿者作为正常对照组。采用韦氏记忆量表评估患者和对照组记忆功能,并通过高分辨率MRI定量分析海马体积及形态,评估TLE-NL和TLE-HS患者记忆水平和海马体积的改变。结果TLE-NL患者比TLE-HS患者发病年龄更晚[(24.3±12.6)岁与(15.8±10.3)岁;t=3.684,P<0.01],癫痫病程更短[4.00(2.00,8.75)年与14.00(7.50,22.00)年;Z=-4.675,P<0.01],热性惊厥史比例[4.5%(2/44)与62.3%(33/53);χ2=32.270,P<0.01)和药物难治性比例更低[47.7%(21/44)与84.9%(45/53);χ2=15.282,P<0.01)。TLE-NL患者在性别比例、癫痫家族史、致痫灶侧别、先兆发生率、症状学类型及发作频率上与TLE-HS患者类似。TLE-NL患者与正常对照组相比无明显记忆损害(记忆商数:105.2±17.4与103.8±16.2;P=1.000),而TLE-HS患者与正常对照组相比存在明显记忆损害(记忆商数:84.5±20.3与103.8±16.2;P<0.01)。TLE-NL患者海马体积和形态与正常对照组相比无明显改变,而TLE-HS患者存在明显致痫灶同侧海马萎缩[(2953±481)mm3与(4431±505)mm3;P<0.01),形态分析结果提示萎缩以海马头及海马体部明显。结论TLE-NL是一类有别于TLE-HS的颞叶癫痫综合征,具有发病年龄晚、病程短、热性惊厥史少、药物难治性癫痫发生率较低、无明显记忆损害及海马萎缩的临床特点。  相似文献   
56.
目的 分析变异型吉兰-巴雷综合征(GBS)的临床特点。方法 回顾性分析2012年10月-2019年3月变异型GBS患者的临床表现、电生理及脑脊液特点。结果 共34例患者,包括Miller-Fisher综合征(MFS)及MFS变异亚型共12例,脑神经变异型(CNV)12例,急性感觉神经病(ASN)1例,急性泛自主神经病(APN)1例,咽-颈-臂(PCB)2例以及不能明确分型6例。34例变异型GBS患者中男20例、女14例(P=0.392); 发病年龄17~80岁,平均年龄(53.38±14.99)岁,中年(41~65岁)组所占比例最多(P=0.000); 20例有前驱事件,上呼吸道感染占65%; 首发症状以肢体麻木(38.2%)、吞咽困难(29.4%)、吐词不清(23.5%)多见; 97.1%的患者发病4周内达高峰; 需机械通气者5.9%; 疾病开始恢复的中位时间13 d,住院中位时长13.5 d; 64.7%的患者腱反射减弱或消失; 在完成腰椎穿刺检查的患者中脑脊液蛋白-细胞分离者58.6%; 发病到完善神经电生理检查的平均时间(10.70±7.32)d,85.2%神经电生理检查表现异常; 50%患者给予静脉注射免疫球蛋白(IVIg)治疗,14.7%患者给予激素治疗,8.8%患者给予免疫球蛋白联合激素治疗,除外1例患者主动要求出院,其余治疗均有效。结论 变异型GBS临床表现多样,常无典型急性四肢对称性迟缓性麻痹等症状,临床诊断需要综合判断,出现一些少见的临床表现并不能除外GBS的诊断,脑脊液和神经电生理检查可以帮助提高诊断,详尽的病史及神经系统查体尤为重要,免疫球蛋白和激素治疗有效。  相似文献   
57.
目的:研析奥氮平治疗老年晚期癌症患者抑郁状态的血药浓度与临床疗效的关系,促进合理用药。方法:80例这类患者服用2.5 ~ 10 mg·d-1奥氮平,应用全自动二维液相色谱法(2D-LC/UV)检测患者用药后4周内每周奥氮平血药浓度(C奥氮平);采用汉密尔顿抑郁量表(HAMD-24)于治疗前、治疗后4周内每周评估疗效,应用线性回归方程分析奥氮平剂量与血药浓度相关性,运用Logistic回归和受试者工作曲线(ROC)分析奥氮平血药浓度与临床疗效相关性;采用副反应量表(TESS)评估药物不良反应。结果:奥氮平日剂量(D日)和C奥氮平线性方程呈正相关(r=0.634,P<0.001)。治疗的第1、2、3、4周末,有效组与无效组患者D日、C奥氮平、HAMD-24量表减分率存在显著性差异(P<0.05)。经Logistic回归分析得出年龄大、奥氮平血药浓度低是导致奥氮平治疗效果不理想的影响因素。以C奥氮平作为疗效预测因子绘制治疗第1、2、3、4周末ROC曲线,得出约登指数最大时对应的最佳临界值切点分别11.18、13.89、11.55、12.44 ng·mL-1;未发现C奥氮平与TESS量表评分相关(P>0.05)。结论:奥氮平血药浓度与日剂量、临床疗效密切相关,治疗老年晚期癌症患者抑郁状态最低有效血药浓度范围为11~14 ng·mL-1。  相似文献   
58.
Hu  Ying-Chao  Tang  Yun  Chen  Zhi-Qiang  Chen  Jing-Yi  Ding  Guo-Hua 《Ecotoxicology (London, England)》2019,28(10):1150-1159

Cadmium (Cd) exposure is harmful to amphibians in natural environments and the Cd concentration is a key parameter in water monitoring. Cd pollution has been a severe issue in the Yangtze River and its southern reaches in recent years. Acute toxicity assays were employed to determine the tolerance limits of Cd for Microhyla fissipes tadpoles and five different concentrations of Cd (0, 50, 100, 200 and 300 μg/L) were involved to detect its chronic effects on metamorphosis, growth, locomotion, genotoxicity and enzymatic activities of M. fissipes tadpoles. The results showed that the 24-h and 48-h LC50 values of Cd on M. fissipes tadpoles were 2591.3 μg/L and 1567.9 μg/L, respectively, and the presumable non-lethal concentration obtained was 172.2 μg/L. During the 70-day chronic toxicity assays, Cd showed negative impacts on survival, growth, metamorphosis and the frequency of erythrocytes nuclear abnormality of M. fissipes tadpoles. However, the Cd exposure caused the increased body size and condition of tadpoles at complete metamorphosis (GS46). The tadpoles exposed to 200 μg/L of Cd exhibited degraded locomotor performance at GS46. Weight increments of tadpoles were inhibited at Day 14 and massive deaths were observed over the next 14 days. The enzymatic activities of tadpoles experienced a shock response stage (GS30-GS35) and a complete recovery stage (GS36-GS41) in all treatments. However, the enzymatic activities (except alkaline phosphatase) of tadpoles at GS46 increased after Cd exposure, especially at high concentrations. In summary, Cd is a threat to M. fissipes tadpoles as that causes reduced fitness.

  相似文献   
59.
Based on the physical randomization of completely randomized experiments, in a recent article in Statistics in Medicine, Rigdon and Hudgens propose two approaches to obtaining exact confidence intervals for the average causal effect on a binary outcome. They construct the first confidence interval by combining, with the Bonferroni adjustment, the prediction sets for treatment effects among treatment and control groups, and the second one by inverting a series of randomization tests. With sample size n, their second approach requires performing O(n4)randomization tests. We demonstrate that the physical randomization also justifies other ways to constructing exact confidence intervals that are more computationally efficient. By exploiting recent advances in hypergeometric confidence intervals and the stochastic order information of randomization tests, we propose approaches that either do not need to invoke Monte Carlo or require performing at most O(n2)randomization tests. We provide technical details and R code in the Supporting Information . Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   
60.
Yang  Hongna  Wang  Cuilan  Wang  Hao  Ding  Shifang 《Journal of neurovirology》2020,26(6):976-979
Journal of NeuroVirology - Listeria rhombencephalitis (L. rhombencephalitis) is an uncommon form of central nervous system infection caused by Listeria monocytogenes (LM). It often occurs to...  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