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   1100篇
  免费   101篇
耳鼻咽喉   25篇
儿科学   71篇
妇产科学   22篇
基础医学   149篇
口腔科学   11篇
临床医学   133篇
内科学   235篇
皮肤病学   34篇
神经病学   69篇
特种医学   94篇
外科学   85篇
综合类   26篇
预防医学   89篇
眼科学   14篇
药学   92篇
中国医学   9篇
肿瘤学   43篇
  2022年   8篇
  2021年   11篇
  2019年   9篇
  2018年   11篇
  2017年   14篇
  2016年   15篇
  2015年   23篇
  2014年   30篇
  2013年   45篇
  2012年   38篇
  2011年   33篇
  2010年   34篇
  2009年   37篇
  2008年   38篇
  2007年   40篇
  2006年   37篇
  2005年   36篇
  2004年   32篇
  2003年   39篇
  2002年   44篇
  2001年   24篇
  2000年   22篇
  1999年   22篇
  1998年   25篇
  1997年   48篇
  1996年   36篇
  1995年   25篇
  1994年   40篇
  1993年   29篇
  1992年   24篇
  1991年   16篇
  1990年   28篇
  1989年   32篇
  1988年   25篇
  1987年   21篇
  1986年   22篇
  1985年   30篇
  1984年   18篇
  1983年   7篇
  1982年   10篇
  1981年   5篇
  1980年   9篇
  1979年   9篇
  1978年   10篇
  1977年   14篇
  1976年   6篇
  1975年   14篇
  1973年   6篇
  1972年   8篇
  1971年   7篇
排序方式: 共有1201条查询结果,搜索用时 15 毫秒
31.
Children diagnosed with attention-deficit/hyperactivity disorder (ADHD) are at increased risk for substance abuse. Response inhibition is a hallmark of ADHD, yet the combined effects of ADHD and regular substance use on neural networks associated with response inhibition are unknown. Task-based functional Magnetic Resonance Imaging (fMRI) data from young adults with childhood ADHD with (n?=?25) and without (n?=?25) cannabis use ≥ monthly in the past year were compared with a local normative comparison group (LNCG) with (n?=?11) and without (n?=?12) cannabis use. Go/NoGo behavioral and fMRI data were evaluated for main and interaction effects of ADHD diagnosis and cannabis use. ADHD participants made significantly more commission errors on NoGo trials than controls. ADHD participants also had less frontoparietal and frontostriatal activity, independent of cannabis use. No main effects of cannabis use on response inhibition or functional brain activation were observed. An interaction of ADHD diagnosis and cannabis use was found in the right hippocampus and cerebellar vermis, with increased recruitment of these regions in cannabis-using controls during correct response inhibition. ADHD participants had impaired response inhibition combined with less fronto-parietal/striatal activity, regardless of cannabis use history. Cannabis use did not impact behavioral response inhibition. Cannabis use was associated with hippocampal and cerebellar activation, areas rich in cannabinoid receptors, in LNCG but not ADHD participants. This may reflect recruitment of compensatory circuitry in cannabis using controls but not ADHD participants. Future studies targeting hippocampal and cerebellar-dependent function in these groups may provide further insight into how this circuitry is altered by ADHD and cannabis use.  相似文献   
32.
33.

Background  

The purpose of the present investigation was to determine if the salivary counts of 40 common oral bacteria in subjects with an oral squamous cell carcinoma (OSCC) lesion would differ from those found in cancer-free (OSCC-free) controls.  相似文献   
34.
希—内学习能力测验在中国聋儿中使用的信度和效度   总被引:4,自引:0,他引:4  
采用经部分修改的希-内学习能力测验(H-NTLA)量表对全国21个省、市、自治区1758名3-17岁聋儿逐人测试。样本人群地区分布、家长职业构成与1990年全国人口普查资料一致。1758名聋儿智商呈现正态分布(g1=0.011P>0.05,g2=0.058P>0.05)。测试员间信度系数0.981(N=24),复测信度0.841(N=136),分半信度0.927(3-8岁)及0.854(9-17岁)。各分测验得分随年龄增加而增加,小年龄组增加明显,大年龄组增加缓慢。各分测验之间、各分测验和总离差智商之间大多数相关系数有显著统计学意义。智商与学习成绩(语文及数学)相关系数0.208(P<0.01N=224),与教师评语等级相关系数0.44(P<0.05df=16),表明经修订的H-NTLA量表适用于中国听力语言障碍人群进行智力评定。  相似文献   
35.
创伤病人的手术与焦虑状态调查   总被引:6,自引:0,他引:6  
采用状态——特质焦虑问卷及10项躯体性焦虑测试题,对40例外科创伤病人手术前后的焦虑状态调查显示:术前状态焦虑量表评分显著高于术后;术前躯体性焦虑评分显著高于术后;高特质焦虑评分亚组与低特质焦虑评分亚组术前状态焦虑评分无显著差异,但术后则前者显著高于后者;急诊手术者手术前后状态焦虑评分显著高于择期手术者。  相似文献   
36.
The allelic frequency of the gene for the K variant of butyrylcholinesterase (BCHE-K) was 0.17 in 74 subjects with late-onset (age > 65 years) histopathologically diagnosed Alzheimer's disease (AD), which was higher than the frequencies in 104 elderly control subjects (0.09), in 14 early-onset cases of confirmed AD (0.07) and in 29 confirmed cases of other dementia (0.10). The association of BCHE-K with late-onset AD was limited to carriers of the epsilon 4 allele of the apolipoprotein E gene (APOE), among whom the presence of BCHE-K gave an odds ratio of confirmed late-onset AD of 6.9 (95% C.I. 1.65-29) in subjects > 65 years and of 12.8 (1.9-86) in subjects > 75 years. In APOE epsilon 4 carriers over 75 years, only 1/22 controls, compared with 10/24 confirmed late-onset AD cases, had BCHE-K. We suggest that BCHE-K, or a nearby gene on chromosome 3, acts in synergy with APOE epsilon 4 as a susceptibility gene for late-onset AD.   相似文献   
37.
38.
SummaryThe detailed molecular mechanisms following activation of apoptosis in ischemia-reperfusion injury are unknown. This study using different transgenic mouse models provided first evidence that apoptosis in myocardial ischemia-reperfusion injury is rather linked to the mitochondrial pathway than to death receptor pathway.IntroductionThere is a wealth of evidence for activation of apoptosis in ischemia-reperfusion injury. However, the understanding of detailed molecular mechanism is lacking.MethodsThe extent of myocardial infarction after ligation of the left anterior descending artery in mice carrying different transgenes for inhibition of either the intrinsic or the extrinsic or a combination of both apoptotic cascades was evaluated. The extent of myocardial damage was assessed by echocardiographic determination of left ventricular (LV) ejection fraction, LV hemodynamics, troponin T, and histology. The rate of apoptosis was analyzed by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and caspase-3 staining.ResultsHighest perioperative rate of death was observed in the dominant-negative form of a truncated Fas-associated death domain (FADD-DN) group. Infarction size by 2,3,5-triphenyltetrazolium chloride (TTC) staining was smaller in the Bcl-2, but not in the other groups as compared to wild-type mice. This was accompanied by lower troponin T values in Bcl-2 transgenic mice as compared to the all other groups. Troponin T correlated well with macroscopic extent of myocardial infarction by TTC staining. A lower decline of LV ejection fraction was seen in the Bcl-2 as compared to wild-type or FADD-DN mice. A smaller number of TUNEL- and caspase-3-positive myocyte nuclei were observed in the Bcl-2 and FADD-DN group as compared to wild-type mice.ConclusionsWe provide first evidence for protective effects on the myocardium in a transgenic mouse model of myocardial ischemia-reperfusion due to inhibition of the Bcl-2, but not the FADD pathway despite that reduced apoptotic cells were observed in both groups as compared to wild-type mice.  相似文献   
39.
The zebrafish is a model organism for studies of vertebrate muscle differentiation and development. However, an understanding of fish muscle physiology during this period is limited. We examined the membrane, contractile, electrical coupling, and synaptic properties of embryonic red (ER) and white (EW) muscle fibers in developing zebrafish from 1 to 5 days postfertilization. Resting membrane potentials were -73 mV in 1 day ER and -78 mV in 1 day EW muscle and depolarized 17 and 7 mV, respectively, by 5 days. Neither fiber type exhibited action potentials. Current-voltage relationships were linear in EW fibers and day 1 ER fibers but were outwardly rectifying in some ER fibers at 3 to 5 days. Both ER and EW fibers were contractile at all ages examined (1 to 5 days) and could follow trains of electrical stimulation of up to 30 Hz without fatiguing for up to 5 min. Synaptic activity consisting of miniature endplate potentials (mEPPs) was observed at the earliest ages examined (1.2-1. 4 days) in both ER and EW fibers. Synaptic activity increased in frequency, and mEPP amplitudes were larger by 5 days. Miniature EPP rise times and half-widths decreased in ER fibers by 5 days, while EW fiber mEPPs showed fast kinetics as early as 1.2-1.4 days. ER and EW muscle fibers showed extensive dye coupling but not heterologous (red-white) coupling. Dye coupling decreased by 3 days yet remained at 5 days. Somites were electrically coupling, and this allowed filtered synaptic potentials to spread from myotome to myotome. It is concluded that at early developmental stages the physiological properties of ER and EW muscle are similar but not identical and are optimized to the patterns of swimming observed at these stages.  相似文献   
40.

Background

Recent research from the American Board of Orthopaedic Surgery database indicates a decreasing rate of subacromial decompression (SAD) performed with rotator cuff repair (RCR) by younger orthopedic surgeons.

Questions/Purposes

The purpose of this study was to determine the rate of RCR with and without SAD and whether the rate of RCR with SAD decreased over time. Further, we set out to determine if there was significant variation in the rate of RCR with SAD by state.

Methods

Rates of RCR with and without open or arthroscopic SAD from 2010 to 2012 were determined based upon de-identified data from a national health insurance carrier. Data were normalized per 10,000 insured patients for comparative analysis.

Results

Rates of RCR with concomitant SAD were higher than RCR without SAD in each year analyzed. In patients 50 years old and older, this same significant difference was also seen for each year. The rate of RCR with or without SAD did not decrease over the 3-year time period. The rate of RCR performed concomitantly with SAD was significantly higher than RCR performed without SAD in all patient age groups combined. There was wide variation in the rate of RCR with or without concurrent SAD across states.

Conclusion

Disproving our hypothesis, the overall rate of RCR with or without SAD did not decrease over the period from 2010 to 2012. There was wide variation in the rate of RCR by state; however, this variation was not seen in the incidence of SAD performed concomitant with the RCR.
  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