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   2223篇
  免费   132篇
  国内免费   11篇
耳鼻咽喉   29篇
儿科学   28篇
妇产科学   59篇
基础医学   353篇
口腔科学   47篇
临床医学   234篇
内科学   390篇
皮肤病学   34篇
神经病学   325篇
特种医学   83篇
外科学   366篇
综合类   6篇
一般理论   2篇
预防医学   131篇
眼科学   53篇
药学   146篇
肿瘤学   80篇
  2023年   17篇
  2022年   28篇
  2021年   46篇
  2020年   39篇
  2019年   48篇
  2018年   41篇
  2017年   55篇
  2016年   62篇
  2015年   54篇
  2014年   72篇
  2013年   123篇
  2012年   166篇
  2011年   158篇
  2010年   101篇
  2009年   85篇
  2008年   146篇
  2007年   159篇
  2006年   135篇
  2005年   139篇
  2004年   133篇
  2003年   151篇
  2002年   139篇
  2001年   29篇
  2000年   15篇
  1999年   18篇
  1998年   25篇
  1997年   35篇
  1996年   14篇
  1995年   13篇
  1994年   9篇
  1993年   15篇
  1992年   9篇
  1991年   4篇
  1990年   10篇
  1989年   8篇
  1988年   7篇
  1987年   3篇
  1986年   2篇
  1985年   7篇
  1984年   5篇
  1983年   7篇
  1982年   6篇
  1981年   3篇
  1980年   3篇
  1979年   5篇
  1978年   3篇
  1977年   2篇
  1973年   3篇
  1972年   2篇
  1971年   3篇
排序方式: 共有2366条查询结果,搜索用时 0 毫秒
71.
Two-point discrimination threshold is commonly used for assessing tactile spatial resolution. Since the effect of temporal features of cutaneous test stimulation on spatial discrimination ability is not yet well known, we determined whether the ability to discriminate between two stimulus locations varies with the interstimulus interval (ISI) of sequentially presented tactile stimuli or the length of the stimulus train. Electrotactile stimuli were applied to one or two locations on the skin of the thenar eminence of the hand in healthy human subjects. Tactile discrimination ability was determined using methods based on the signal detection theory allowing the assessment of sensory performance, independent of the subject’s response criterion. With stimulus pairs, the ability to discriminate spatial features of stimulation (one location vs. two stimulus locations 4 cm apart) was improved when the ISI was equal to or longer than that required for tactile temporal discrimination. With stimulus trains, the ability to discriminate spatial features of stimulation was significantly improved with an increase in the stimulus train (from 3 to 11 pulses corresponding to train lengths from 40 to 200 ms). These results indicate that temporal features of tactile stimulation significantly influence sensory performance in a tactile spatial discrimination task. Precise control of temporal stimulus parameters should help to reduce variations in results on the two-point discrimination threshold.  相似文献   
72.
The genetic architecture of behavioral traits is yet relatively poorly understood in most non-model organisms. Using an F2-intercross (n = 283 offspring) between behaviorally divergent nine-spined stickleback (Pungitius pungitius) populations, we tested for and explored the genetic basis of different behavioral traits with the aid of quantitative trait locus (QTL) analyses based on 226 microsatellite markers. The behaviors were analyzed both separately (viz. feeding activity, risk-taking and exploration) and combined in order to map composite behavioral type. Two significant QTL—explaining on average 6 % of the phenotypic variance—were detected for composite behavioral type on the experiment-wide level, located on linkage groups 3 and 8. In addition, several suggestive QTL located on six other linkage groups were detected on the chromosome-wide level. Apart from providing evidence for the genetic basis of behavioral variation, the results provide a good starting point for finer-scale analyses of genetic factors influencing behavioral variation in the nine-spined stickleback.  相似文献   
73.
74.
75.
Nikkonen  Sami  Töyräs  Juha  Mervaala  Esa  Myllymaa  Sami  Terrill  Philip  Leppänen  Timo 《Sleep & breathing》2020,24(1):379-386
Sleep and Breathing - Diagnostics of obstructive sleep apnea (OSA) is based on apnea-hypopnea index (AHI) determined as full-night average of occurred events. We investigate our hypothesis that...  相似文献   
76.
BackgroundMajor histocompatibility complex (MHC) gene region harbours haplotypes that associate with coronary artery disease (CAD). Their role in ST-elevation infarction (STEMI) or on the inflammatory level is not known.MethodsFour candidate MHC markers were analyzed by real-time quantitative PCR and constructed into haplotypes from patients with STEMI (n = 162), matched controls with no CAD (n = 319) and general population sample (n = 149). High sensitivity C-reactive protein (hsCRP) was assessed in a follow-up visit from patients (n = 86) and at inclusion from other study subjects.ResultsThe haplotype with one copy of HLA-DRB1*01, C4A, C4B but no HLA-B*35 doubled the risk of STEMI (OR = 2.15, 95%CI = 1.11–4.15, p = 0.020 for patients vs. controls, and OR = 2.26, 95%CI = 0.97–5.24, p = 0.052 for patients vs. population sample). The association between patients and controls persisted in multivariate analyses. The frequency of the haplotype was 5.86% (n = 19/324) in patients, 2.82% (n = 18/638) in controls and 2.68% (n = 8/298) in population sample. None of the individual MHC markers alone showed significant association with STEMI.In multivariate analyses, the haplotype carriers had higher hsCRP levels in patients (median 3.37 mg/L in carriers vs. 1.14 mg/L in non-carriers, p = 0.019) and in controls (median 2.90 mg/L vs. 1.21 mg/L, p = 0.009, respectively).ConclusionThe MHC haplotype associates with STEMI and elevated baseline hsCRP levels. The results are in concordance with previous data on non-STEMI patients, implying that a HLA-DRB1*01 – related haplotype increases the risk of CAD, possibly though increased inflammation.  相似文献   
77.
Background/Aims: To examine whether intestinal bacterial translocation occurs early in acute mild and severe pancreatitis and whether the intestinal expression of tight junction proteins (claudins-2, -3, -4, -5, -7), apoptosis or proliferation would explain the possible translocation. Methodology: Fifteen pigs were randomized to controls (n=5) or to develop mild edematous pancreatitis (n=5, saline infusion to pancreatic duct) or severe necrotic pancreatitis (n=5, taurocholic acid infusion). Translocation was studied by measuring bacterial cultures from portal vein blood and mesenteric lymph nodes. Immunohistochemical expression of the tight junction proteins, apoptosis rate (TUNEL) and Ki-67 were analyzed quantitatively from the epithelium of the jejunum and colon. Results: There was no bacterial translocation during the 6 hours followup, nor changes in the expression of tight junction proteins claudins-2 and -5 in jejunum or colon. Saturation and proportional area of claudin-3 staining decreased in the colon, as did claudins-4 and -7 staining in the jejunum of the necrotic pancreatitis group. Increased apoptosis was found in all samples from controls and the edematous pancreatitis group but not in jejunum in the necrotic pancreatitis group. Ki-67 activity tended to increase in the upper half of the villus in edematous and necrotic pancreatitis. There were no changes in the basic histology. Conclusions: The major finding of this study was that bacterial translocation from the gut is not present at the beginning of acute pancreatitis. Tight junction proteins claudin-2 and -5 do not become altered in the early stages of pancreatitis. Claudin-3 decreases in the colon and claudins-4 and -7 in the jejunum in necrotic pancreatitis. Laparotomy itself causes increased apoptosis in the colon and the jejunum.  相似文献   
78.
79.
80.
We developed and characterized 113 polymorphic microsatellites in the Tibetan frog (Nanorana parkeri) using 454 GS-FLX next generation sequencing technology. These loci were tested in 46 individuals from two N. parkeri populations from the Tibetan plateau. The average number of alleles per locus was 8.09 (range = 2–20). The average observed heterozygosities (H O) per locus in the two populations were 0.58 (range = 0.04–1) and 0.29 (range = 0–0.87), respectively. These microsatellites will be useful for population and conservation genetics studies of N. parkeri and other closely related species.  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