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   124263篇
  免费   7796篇
  国内免费   2136篇
耳鼻咽喉   1753篇
儿科学   3023篇
妇产科学   4170篇
基础医学   18915篇
口腔科学   3688篇
临床医学   10043篇
内科学   22309篇
皮肤病学   2500篇
神经病学   8289篇
特种医学   4318篇
外国民族医学   5篇
外科学   17299篇
综合类   6382篇
一般理论   34篇
预防医学   9011篇
眼科学   2918篇
药学   10861篇
  12篇
中国医学   1238篇
肿瘤学   7427篇
  2021年   1128篇
  2019年   1263篇
  2018年   1799篇
  2017年   1406篇
  2016年   1380篇
  2015年   1791篇
  2014年   2295篇
  2013年   2764篇
  2012年   4007篇
  2011年   4380篇
  2010年   2681篇
  2009年   2325篇
  2008年   3761篇
  2007年   3934篇
  2006年   3953篇
  2005年   3518篇
  2004年   3190篇
  2003年   3014篇
  2002年   2823篇
  2001年   6897篇
  2000年   7063篇
  1999年   5784篇
  1998年   1845篇
  1997年   1414篇
  1996年   940篇
  1995年   921篇
  1992年   3756篇
  1991年   3831篇
  1990年   3573篇
  1989年   3573篇
  1988年   3451篇
  1987年   3286篇
  1986年   3101篇
  1985年   2981篇
  1984年   2049篇
  1983年   1794篇
  1982年   985篇
  1979年   1909篇
  1978年   1184篇
  1977年   984篇
  1976年   918篇
  1975年   1189篇
  1974年   1356篇
  1973年   1412篇
  1972年   1355篇
  1971年   1243篇
  1970年   1134篇
  1969年   1113篇
  1968年   1022篇
  1967年   895篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
目的分析肝移植术后受者外周血CD19+CD24hiCD38hi B细胞占单个核细胞比例变化情况及其与急性细胞性排斥反应(ACR)之间的关系。 方法回顾性分析2013年12月至2015年12月在浙江大学医学院附属第一医院接受心脏死亡器官捐献肝移植的80例成人受者临床资料,根据术后是否发生ACR,将受者分为ACR组(25例)和非ACR组(55例)。术前、术后各个时间点抽取参加研究者静脉血并分离外周血单个核细胞,加入异硫氰酸荧光素-单克隆鼠抗人CD19抗体、藻红蛋白-单克隆鼠抗人CD24抗体和别藻蓝蛋白-单克隆鼠抗人CD38抗体,流式细胞仪检测各组CD19+CD24hiCD38hi B细胞百分比。采用t检验和单因素方差分析比较正态分布计量资料,采用χ2检验比较计数资料,采用Kaplan-Meier法绘制受试者工作特征曲线(ROC曲线)。P<0.05为差异有统计学意义。 结果ACR组、非ACR组受者术前外周血平均CD19+CD24hiCD38hi B细胞比例分别为(3.13±0.91)%、(3.49±0.83)%,差异无统计学意义(t=1.636,P>0.05)。ACR组术后发生ACR前外周血平均CD19+CD24hiCD38hi B细胞比例为(1.87±0.70)%。非ACR组受者术后3个月、6个月和1年外周血平均CD19+CD24hiCD38hi B细胞比例分别为(1.64±0.52)%、(1.63±0.56)%和(2.04±1.24)%,术后3、6个月平均值均低于术前和术后1年,差异均有统计学意义(P均<0.05)。ACR组受者发生ACR时外周血平均CD19+CD24hiCD38hi B细胞比例为(0.8±0.5)%,低于发生ACR前的平均水平(t=5.752,P<0.05),且低于非ACR组术后3个月、6个月和1年的平均水平(P<0.05)。ACR组受者接受抗排斥反应治疗后,CD19+CD24hiCD38hi B细胞比例也逐渐增加,ACR发生后7 d为(0.84±0.08)%,与ACR发生时相比差异无统计学意义(P>0.05);而发生30 d后达(1.65±0.18)%,与ACR发生时相比差异有统计学意义(P<0.05)。当截断值为1.015%时,CD19+CD24hiCD38hi B细胞比例预测ACR发生的敏感度和特异度分别为0.786和0.702,ROC曲线下面积为0.775(95%CI: 0.671~0.879,P<0.05)。 结论CD19+CD24hiCD38hi B细胞比例下降与肝移植术后ACR反应发生有关,并可作为预测ACR发生的细胞标志物。  相似文献   
4.
目的 探讨右美托咪定联合综合体温保护对腔镜手术治疗老年恶性肿瘤患者苏醒期质量及免疫功能的影响。方法 选择择期行腔镜手术治疗的老年恶性肿瘤患者90例,随机均分为3组:对照组(C组)、体温保护组(T组)和体温保护联合右美托咪定组(T-D组),每组30例。C组常规体温保护,T组和T-D组综合体温保护;T-D组麻醉诱导前10 min泵注右美托咪定0.5 μg/kg。记录3组患者麻醉诱导开始时(T0)、手术开始30 min(T1)、60 min(T2)、90 min(T3)、120 min(T4)以及手术结束时(T5)的鼻咽温度;于T0、术后2 h(T6)、24 h(T7)和48 h(T8)时抽取静脉血标本,测定T淋巴细胞亚群(CD3+、CD4+和CD8+)和自然杀伤细胞(NK cell)水平;记录患者术中麻醉药物用量及苏醒期质量指标。结果 与T0比较,C组T2~T5时点鼻咽温度均明显降低(P < 0.05);与C组比较,T组和T-D组T2~T5时点鼻咽温度明显升高(P < 0.05)。与T0时点比较,C组、T组和T-D组T6、T7和T8时点CD3+和NK cell活性均明显降低(P < 0.05);C组在T6、T7和T8时点,T组和T-D组在T6和T7时点,CD4+活性均明显降低(P < 0.05)。与C组比较,T组和T-D组T6和T7时点CD3+细胞活性均明显升高(P < 0.05);T组在T7时点,T-D组在T6和T7时点,CD4+细胞活性均明显升高(P < 0.05);T组在T7时点,T-D组在T6、T7和T8时点,NK cell活性均明显升高(P < 0.05)。结论 采用体温保护措施联合右美托咪定能够维持老年恶性肿瘤患者的体温稳定,减少围手术期意外低体温(IPH)的发生,并有效提高患者苏醒期质量,减轻免疫抑制程度,加速患者早期恢复。  相似文献   
5.
目的 评价美国国家电器制造协会(National Electrical Manufactures Association, NEMA)最新标准(NU 2-2018)在正电子发射型计算机断层显像/电子计算机断层显像(positron emission tomography/computed tomography, PET/CT)设备性能检测中的作用。 方法 依据最新的NEMA NU 2-2018标准,检测西门子Biograph Vision PET/CT的空间分辨率、灵敏度、散射分数、计数丢失、随机符合、飞行时间分辨率、计数丢失率和随机符合校正精度、图像质量、衰减和散射校正精度及PET与CT配准精度指标。 结果 距视野中心1 cm处横向和轴向空间分辨率分别为3.75 mm和3.76 mm;在视野中心和轴向10 cm处的灵敏度分别为16.83 kcps/MBq和16.67 kcps/MBq;放射性浓度为27.37 kBq/mL时,最大等效噪声计数率为258.26 kcps,散射分数为38.58%;系统时间分辨率为209.82 ps;图像质量模型的对比度恢复系数范围为88.9%~96.2%,背景变异系数范围为2.05%~6.80%,平均肺插件残余误差为2.43%;计数丢失和随机符合校正最大误差为3.9%;距离床板末端 5 cm 和 100 cm处,在距视野中心Y轴1 cm处,PET和CT的配准精度分别为0.46 mm和1.07 mm,在距视野中心X轴20 cm处,PET和CT的配准精度分别为1.06 mm和1.45 mm,在距视野中心Y轴20 cm处PET和CT的配准精度分别为0.85 mm和1.15 mm。 结论 NEMA NU 2-2018标准检测条件更加接近临床,能更好地反映PET/CT设备的系统性能。  相似文献   
6.
Integrase strand transfer inhibitors (InSTIs) have been widely used in recent years because of their high genetic barrier to resistance. The World Health Organization (WHO) has recommended dolutegravir (DTG)-containing regimens as the preferred first- and second-line antiretroviral therapy (ART) regimens for people living with human immunodeficiency virus (HIV)[1]. During the long-term treatment process, the appearance of drug resistance mutations to InSTIs is inevitable. A meta-analysis has shown that the resistance rate among InSTI treatment-experienced patients is 3.9% (Raltegravir, RAL), 1.2% (Elvitegravir, EVG), and 0.1% (DTG)[2]. However, resistance to InSTIs has not been reported in treatment-naive populations.  相似文献   
7.
Background  The data visualization literature asserts that the details of the optimal data display must be tailored to the specific task, the background of the user, and the characteristics of the data. The general organizing principle of a concept-oriented display is known to be useful for many tasks and data types. Objectives  In this project, we used general principles of data visualization and a co-design process to produce a clinical display tailored to a specific cognitive task, chosen from the anesthesia domain, but with clear generalizability to other clinical tasks. To support the work of the anesthesia-in-charge (AIC) our task was, for a given day, to depict the acuity level and complexity of each patient in the collection of those that will be operated on the following day. The AIC uses this information to optimally allocate anesthesia staff and providers across operating rooms. Methods  We used a co-design process to collaborate with participants who work in the AIC role. We conducted two in-depth interviews with AICs and engaged them in subsequent input on iterative design solutions. Results  Through a co-design process, we found (1) the need to carefully match the level of detail in the display to the level required by the clinical task, (2) the impedance caused by irrelevant information on the screen such as icons relevant only to other tasks, and (3) the desire for a specific but optional trajectory of increasingly detailed textual summaries. Conclusion  This study reports a real-world clinical informatics development project that engaged users as co-designers. Our process led to the user-preferred design of a single binary flag to identify the subset of patients needing further investigation, and then a trajectory of increasingly detailed, text-based abstractions for each patient that can be displayed when more information is needed.  相似文献   
8.
Whether testicular toxicity is mediated by matrix metalloproteinases (MMPs) is an important question that has not been examined. This study investigated the suppressive effect of curcumin and caffeic acid phenethyl ester (CAPE) on oxidative stress, apoptosis, and whether MMPs mediate doxorubicin (DOX)-induced testicular injury. Male rats were randomly divided into eight groups (n = 8 per group). The groups were as follows: sham, dimethyl sulphoxide (100 µL), DOX (3 mg/kg), CAPE (2.68 mg/kg), curcumin (30 mg/kg), DOX+CAPE (3 mg/kg DOX and 2.68 mg/kg CAPE), DOX+curcumin (3 mg/kg DOX and 30 mg/kg curcumin) and DOX+CAPE+curcumin (3 mg/kg DOX, 2.68 mg/kg CAPE and 30 mg/kg curcumin). Injections were administered daily for 21 days. The oxidative stress, MMPs, proinflammatory cytokines and apoptotic markers in the DOX group were higher than the sham group (p < .05); these measures were lower in the groups treated with CAPE and curcumin together with DOX compared with the DOX group (p < .05). The results showed that MMPs mediated DOX-induced testicular injury, but CAPE and especially curcumin suppressed testis injury and cell apoptosis by suppressing DOX-induced increases in MMPs, oxidative stress and proinflammatory cytokines. However, curcumin exhibited more pronounced effects than CAPE in terms of all studied parameters.  相似文献   
9.
The adoption of a management approach that integrates corporate social responsibility in organizations is an increasing trend that responds to the demands of society related to sustainability, ethics and transparency. Health organizations are adopting corporate social responsibility asymmetrically, which raises the analysis of the implementation models and the developed initiatives. Through qualitative research, with four in-depth case studies of the Catalan health sector, this article analyzes the need to address this new approach and to identify good practices and the challenges for its implementation.  相似文献   
10.
IntroductionRealignment knee osteotomy relies on accurate preoperative assessment of coronal alignment. Weightbearing (WB) ‘long-leg’ (LL) radiographs are the accepted gold-standard investigation, though in practice standard knee radiographs (short leg; SL) and non-weightbearing (NWB) cross-sectional imaging such as computed tomography (CT) scanograms have been used. We compare the accuracy of SL and NWB radiographs to formal LL alignment radiographs.MethodsA prospectively maintained osteotomy database was reviewed to identify the study population. All patients underwent standardised weightbearing long-leg alignment radiographs. The series was screened consecutively until 30 patients who also underwent WB SL radiographs (‘WB cohort’), and 30 with NWB SL (‘NWB cohort’) radiographs, were identified. Anatomic tibiofemoral angle was calculated by independent reviewers using a validated technique from both radiographs and contrasted.Results60 patients were identified as outlined in the study protocol. There were no differences in baseline demographics. Coronal alignment calculated from SL and LL radiographs differed significantly (median difference 2.1°, p < 0.001). Alignment values from weightbearing SL radiographs demonstrated markedly greater agreement with LL values than those from NWB radiographs (intraclass correlation coefficient 0.878 vs 0.657), with the NWB cohort also exhibiting greater outlier and extreme outlier incidence.ConclusionOur data adds to the growing evidence that SL radiographs are inadequate in the interpretation of knee alignment. In addition, we demonstrate that NWB radiographs (and by extension other NWB modalities such CT scanograms) demonstrate poorer agreement to gold-standard than WB methods. Coronal alignment of the knee cannot be reliably measured from non-weightbearing imaging modalities.Implications for practiceThough potentially useful as an adjunct, non-weightbearing cross-sectional imaging and standard knee radiographs should not be used as a proxy for formal weightbearing long-leg radiographs in osteotomy planning.  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