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   14872篇
  免费   915篇
  国内免费   366篇
耳鼻咽喉   133篇
儿科学   232篇
妇产科学   155篇
基础医学   1160篇
口腔科学   122篇
临床医学   1967篇
内科学   1584篇
皮肤病学   88篇
神经病学   656篇
特种医学   1154篇
外科学   1037篇
综合类   2914篇
预防医学   1758篇
眼科学   348篇
药学   1880篇
  12篇
中国医学   458篇
肿瘤学   495篇
  2024年   16篇
  2023年   163篇
  2022年   322篇
  2021年   400篇
  2020年   447篇
  2019年   348篇
  2018年   377篇
  2017年   494篇
  2016年   531篇
  2015年   518篇
  2014年   1182篇
  2013年   1050篇
  2012年   1282篇
  2011年   1213篇
  2010年   957篇
  2009年   792篇
  2008年   780篇
  2007年   754篇
  2006年   663篇
  2005年   519篇
  2004年   459篇
  2003年   375篇
  2002年   317篇
  2001年   252篇
  2000年   252篇
  1999年   227篇
  1998年   181篇
  1997年   177篇
  1996年   151篇
  1995年   130篇
  1994年   91篇
  1993年   65篇
  1992年   76篇
  1991年   53篇
  1990年   37篇
  1989年   49篇
  1988年   45篇
  1987年   40篇
  1986年   30篇
  1985年   51篇
  1984年   46篇
  1983年   31篇
  1982年   34篇
  1981年   34篇
  1980年   30篇
  1979年   21篇
  1978年   18篇
  1977年   16篇
  1976年   18篇
  1975年   11篇
排序方式: 共有10000条查询结果,搜索用时 421 毫秒
1.
针对日常使用中遇到的Brilliance 16排螺旋CT高压系统、机架以及控制器局域网络(CAN)通讯等故障现象进行分析与维修,最终通过更换滤波电容、机架数据采集控制器(DMC)电源以及信号刷等配件得以排除故障。通过对故障准确判断以及合理运用厂家Service模式下的维修工具软件快速解决故障,保障了影像科检查工作的顺利进行,从而提高设备的稳定性。  相似文献   
2.
目的探讨乙肝相关性肝癌临床病理学特征与溶血磷脂酸(LPA)和高敏C反应蛋白(hs-CRP)表达的相关性。方法选取2019年1月至2020年1月间河南省驻马店市中心医院收治的198例乙肝相关性肝癌患者作为乙肝组,198例酒精相关性肝癌患者作为酒精组。两组患者都进行血清hs-CRP和LPA表达检测,调查患者的病理学特征并进行相关性分析。结果乙肝组患者血清hs-CRP和LPA含量均高于酒精组,差异均有统计学意义(均P <0.05)。两组患者血清ALP、AFP、ALT、AST和GGT含量比较,差异均无统计学意义(P> 0.05)。乙肝组不同临床分期和组织学分化患者的血清hs-CRP和LPA含量比较,差异均有统计学意义(均P <0.05)。乙肝组患者的临床分期和组织学分化与血清hs-CRP和LPA表达均存在相关性,差异均有统计学意义(均P <0.05)。患者的临床分期和组织学分化均为影响hs-CRP和LPA表达的重要因素,差异均有统计学意义(均P <0.05)。结论相对于酒精相关性肝癌,乙肝相关性肝癌的血清hs-CRP和LPA呈现高表达,与患者的临床病理学特征存在相关性。  相似文献   
3.
In the field of drug development, technology for producing human metabolites at a low cost is required. In this study, we explored the possibility of using prokaryotic water-soluble cytochrome P450 (CYP) to produce human metabolites. Streptomyces griseolus CYP105A1 metabolizes various non-steroidal anti-inflammatory drugs (NSAIDs), including diclofenac, mefenamic acid, flufenamic acid, tolfenamic acid, meclofenamic acid, and ibuprofen. CYP105A1 showed 4′-hydroxylation activity towards diclofenac, mefenamic acid, flufenamic acid, tolfenamic acid, and meclofenamic acid. It should be noted that this reaction specificity was similar to that of human CYP2C9. In the case of mefenamic acid, another metabolite, 3′-hydroxymethyl mefenamic acid, was detected as a major metabolite. Substitution of Arg at position 73 with Ala in CYP105A1 dramatically reduced the hydroxylation activity toward diclofenac, flufenamic acid, and ibuprofen, indicating that Arg73 is essential for the hydroxylation of these substrates. In contrast, substitution of Arg84 with Ala remarkably increased the hydroxylation activity towards diclofenac, mefenamic acid, and flufenamic acid. Recombinant Rhodococcus erythrocyte cells expressing the CYP105A1 variant R84A/M239A showed complete conversion of diclofenac into 4′-hydroxydiclofenac. These results suggest the usefulness of recombinant R. erythropolis cells expressing actinomycete CYP, such as CYP105A1, for the production of human drug metabolites.  相似文献   
4.
5.
6.
This study aimed to understand the perceived effects of the COVID-19 pandemic on physical activity, recreation walking, and use of recreational facilities; and if the COVID-19 pandemic amplified disparities in physical activity, recreational walking, and use of recreational facilities related to the levels of neighborhood disadvantage. Recreational walking and the use of neighborhood streets and green spaces significantly decreased in high deprivation areas but not in low deprivation areas during the pandemic. While COVID-19 has negatively affected overall recreational activities, the inequitable impact on recreational walking and use of outdoor recreational facilities has been more evident in disadvantaged neighborhoods with greater deprivation.  相似文献   
7.
ObjectiveIdentify the effects of multi-directional, high intensity exercise on VOMS symptom scores in male and female recreational, college-aged athletes.DesignCross-sectional study.SettingAthletic Therapy facility.ParticipantsA convenience sample of 29 (15 females, 14 males; 21.48 ± 1.40 years old) healthy recreational athletes.Main outcome measuresVOMS symptom scores pre, immediately post-, and 10 min post a multidirectional, high intensity intermittent exercise protocol (HIIP). Friedman tests and Wilcoxon Signed Rank tests identified significant differences at the time points. A Mann-Whitney U Test investigated the effect of sex.ResultsThe majority of component and overall VOMS symptom scores increased post-HIIP (p < 0.001–0.007, effect sizes 0.39–0.50) and 10 min post-HIIP (p = 0.003–0.015, effect sizes 0.32–0.39). Near point convergence distance increased immediately post-HIIP (p < 0.001, effect size 0.52). Females had higher smooth pursuits (z = −2.340, p = 0.019, r = 0.31), vertical vestibular ocular reflex (z = −2.81, p = 0.04, r = 0.39) visual motion sensitivity (z = −2.312, p = 0.021 r = 0.30) and overall VOMS symptom scores (z = −2.84, p = 0.04, r = 0.27) 10 min post-HIIP.ConclusionsMultidirectional, high intensity exercise can induce concussive-like changes in VOMS symptom scores in healthy, recreational athletes, particularly in females. These results may assist in SRC assessment and management of athletes involved in multidirectional, high intensity sports.  相似文献   
8.
目的:比较卡贝缩宫素和缩宫素治疗剖宫产高危产妇的效果。方法:选取122例剖宫产高危产妇为研究对象,按照随机数字表法分为观察组与对照组各61例。两组均行剖宫产手术,胎儿娩出后,对照组给予缩宫素治疗,观察组给予卡贝缩宫素治疗,比较两组术中、产后2、24 h出血量,产后加用前列素氨丁三醇率,凝血功能指标[纤维蛋白原(FIB)、D-二聚体(D-D)、凝血酶原时间(PT)、部分凝血活酶时间(APTT)]水平,心率,血压,血红蛋白水平和不良反应发生率。结果:观察组术中、产后2、24 h出血量均低于对照组,差异有统计学意义(P<0.05);观察组加用卡前列素氨丁三醇率为4.92%(3/61),明显低于对照组的16.39%(10/61),差异有统计学意义(P<0.05);术后,两组FIB、D-D水平均高于术前,且观察组高于对照组,两组PT、APTT均短于术前,且观察组短于对照组,差异有统计学意义(P<0.05);术后,两组血红蛋白水平均低于术前,但观察组高于对照组,差异有统计学意义(P<0.05);手术前后,两组心率、血压和不良反应发生率比较,差异均无统计学意义(P>0.05)。结论:卡贝缩宫素治疗剖宫产高危产妇可减少出血量和加用卡前列素氨丁三醇率,提高其术后血红蛋白水平,以及改善凝血功能指标,效果优于缩宫素。  相似文献   
9.
An accurate transfer of a 3D virtual planned proportional condylectomy to the patient is challenging due to the limited surgical access. A new clinical workflow that uses augmented reality to assist a condylectomy is presented step-by-step. This AR-based approach has the potential to be implemented in the clinical setting routinely.  相似文献   
10.
《Vaccine》2019,37(47):7003-7010
Control and prevention of rapid influenza spread among humans depend on the availability of efficient and safe seasonal and pandemic vaccines, made primarily from inactivated influenza virus particles. Current influenza virus production processes rely heavily on embryonated chicken eggs or on cell culture as substrate for virus propagation. Today’s efforts towards process intensification in animal cell culture could innovate viral vaccine manufacturing using high-yield suspension cells in high cell density perfusion processes. In this work, we present a MDCK cell line adapted to grow as single cell suspension with a doubling time of less than 20 h, achieving cell concentrations over 1 × 107 cells/mL in batch mode. Influenza A virus titer obtained in batch infections were 3.6 log10(HAU/100 µL) for total- and 109 virions/mL for infectious virus particles (TCID50), respectively. In semi-perfusion mode concentrations up to 6 × 107 cells/mL, accumulated virus titer of 4.5 log10(HAU/100 µL) and infectious titer of almost 1010 virions/mL (TCID50) were possible. This exceeds results reported previously for cell culture-based influenza virus propagation by far and suggests perfusion cultures as the preferred method in viral vaccine manufacturing.  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