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   8849篇
  免费   398篇
  国内免费   41篇
耳鼻咽喉   79篇
儿科学   129篇
妇产科学   102篇
基础医学   931篇
口腔科学   233篇
临床医学   576篇
内科学   2332篇
皮肤病学   253篇
神经病学   706篇
特种医学   312篇
外科学   1578篇
综合类   37篇
预防医学   172篇
眼科学   130篇
药学   627篇
  1篇
中国医学   14篇
肿瘤学   1076篇
  2024年   25篇
  2023年   68篇
  2022年   111篇
  2021年   187篇
  2020年   108篇
  2019年   154篇
  2018年   201篇
  2017年   145篇
  2016年   189篇
  2015年   188篇
  2014年   256篇
  2013年   312篇
  2012年   539篇
  2011年   559篇
  2010年   339篇
  2009年   294篇
  2008年   487篇
  2007年   493篇
  2006年   510篇
  2005年   591篇
  2004年   557篇
  2003年   514篇
  2002年   538篇
  2001年   139篇
  2000年   122篇
  1999年   142篇
  1998年   135篇
  1997年   115篇
  1996年   109篇
  1995年   76篇
  1994年   107篇
  1993年   62篇
  1992年   68篇
  1991年   70篇
  1990年   78篇
  1989年   91篇
  1988年   77篇
  1987年   73篇
  1986年   47篇
  1985年   46篇
  1984年   48篇
  1983年   38篇
  1982年   26篇
  1981年   22篇
  1980年   25篇
  1979年   30篇
  1978年   23篇
  1977年   21篇
  1974年   23篇
  1972年   19篇
排序方式: 共有9288条查询结果,搜索用时 15 毫秒
991.

Objectives

Changes in plasma thioredoxin (TRX) concentrations before, during, and after a 130-km endurance race were measured with the aim of elucidating the relationship between exercise and oxidative stress (OS).

Methods

Blood samples were taken from 18 runners participating in a 2-day-long 130-km ultra-marathon during the 2 days of the race and for 1 week thereafter. There were six sampling time points: at baseline, after the goal had been reached on the first and second day of the endurance race, respectively, and on 1, 3, and 5/6 days post-endurance race. The samples were analyzed for plasma TRX concentrations, platelet count, and blood lipid profiles.

Results

Concentrations of plasma TRX increased from 17.9 ± 1.2 ng/mL (mean ± standard error of the mean) at baseline to 57.3 ± 5.0 ng/mL after the first day’s goal had been reached and to 70.1 ± 6.9 ng/mL after the second day's goal had been reached; it then returned to the baseline level 1 day after the race. Platelet counts of 21.3 ± 1.2 × 104 cell/μL at baseline increased to 23.9 ± 1.5 × 104 cells/μL on Day 1 and to 26.1 ± 1.0 × 104 cells/μL on Day 2. On Day 7, the platelet counts had fallen to 22.1 ± 1.2 × 104 cell/μL. There was a significant positive correlation between plasma TRX and platelet count.

Conclusions

These data suggest that plasma TRX is an OS marker during physical exercise. Further studies are needed to determine the appropriate level of exercise for the promotion of health.  相似文献   
992.

Objectives  

We evaluated the effectiveness and safety of a disinfectant newly developed by our laboratories for use against influenza viruses.  相似文献   
993.
Fimbriae of Vibrio cholerae O1 were purified from a strain of the classical biotype, Inaba serotype (Bgd 17), and a strain of the El Tor biotype, Ogawa serotype (K23), grown on TCG agar medium by the following procedure; homogenization of the cell suspension to detach fimbriae, ultracentrifugation to remove remaining cells and their debris, concentration of the supernatant containing fimbriae with ultrafiltration, and 20 to 40% sucrose linear gradient centrifugation of the concentrated material. The fimbriae in both preparations were flexible, long fibres readily distinguishable under the electron microscope from those of CFA/I, CFA/II seen in ETEC strains. Their structural subunit was a protein of 16 kdaltons. Fimbriae isolated from both serotypes and biotypes shared antigenic determinants.  相似文献   
994.
The effect of an alpha 2-adrenoceptor agonist, clonidine on wet-dog shaking (WDS; also, WDS = wet-dog shakes) induced by electrical stimulation of the hippocampus was investigated. Clonidine (0.01-0.32 mg/kg i.p.) inhibited the appearance of WDS in a dose-dependent manner without showing any effect on hippocampal afterdischarge. Although clonidine has been reported to inhibit the activity not only of noradrenergic but also of serotonergic neurons, a 5-hydroxytryptamine (5-HT) antagonist, cinanserin at doses up to 32 mg/kg had no significant effect on hippocampal stimulation-induced WDS. Therefore, a possible anti-5-HT action of clonidine in the inhibition of WDS can be excluded. The WDS inhibition produced by clonidine was blocked significantly by pretreatment of the rats with an alpha 2-adrenoceptor antagonist, yohimbine, but not with a narcotic antagonist, naloxone. The present results suggest that a central noradrenergic function may be involved in WDS induced by hippocampal stimulation.  相似文献   
995.
Behavioral effects of zopiclone were investigated in mice and rats and compared with the data on diazepam, nitrazepam and flurazepam. The electroencephalographic effect of the drug was also examined in unanesthetized rabbits with chronic electrode implants and compared with that of diazepam. The present results indicate that zopiclone possesses pharmacological properties qualitatively similar to benzodiazepines, which are characterized by potent anticonflict and antiaggressive effects and much weaker anticonvulsant, muscle relaxant, ataxiogenic, sedative and anesthesia potentiating effects; the properties of this drug were compared with those of diazepam, nitrazepam and flurazepam. Zopiclone suppressed the EEG arousal responses and inhibited afterdischarges induced by electrical stimulation of the hippocampus and amygdala. The effects of zopiclone on EEG and afterdischarges were approximately 1/10 those of diazepam.  相似文献   
996.
OBJECTIVES: This study was conducted to assess characteristics of elderly leaders volunteering to participate in a fall prevention programme. METHODS: We surveyed 1,503 individuals (75 elderly leaders volunteering to participate in a fall prevention programme and 1,428 non-leader elderly) among the elderly population living in a rural community, Miyagi Prefecture. Subjects were aged 70-84 years. The questionnaire covered socio-demographic factors, as well as physical, psychology and social variables. To analyze the characteristics of the elderly leaders volunteering to participate in this programme, the relationships of socio-demographic, physical, psychology and social factors to whether the elderly were leaders in the programme were analyzed using logistic regression. RESULT: As a result of multiple logistic regression analysis, the characteristics of elderly leaders volunteering to participate in the fall prevention programme were as follows; 1) being male (OR = 0.25, 95%CI 0.14-0.44); 2) young age (OR=0.43, 95%CI 0.25-0.73); 3) having a high intellectual activity (OR = 2.72, 95%CI 1.65-4.48); 4) being well satisfied with their health (OR = 1.45, 95%CI 1.02-2.07), and 5) having a high IKIGAI (OR = 1.06, 95%CI 1.01-1.13). CONCLUSION: Only elderly individuals capable of high-level intellectual activities can fill the roles of elderly volunteer group leaders discussed in this study.  相似文献   
997.
STUDY OBJECTIVE: Th2 cytokines play an important role in the pathogenesis of asthma. Our study objective was to determine the effect of suplatast tosilate, a Th2 cytokine inhibitor, on patients with cough-variant asthma. METHODS: Twenty patients with cough-variant asthma (CVA) were assigned to a suplatast tosilate (100 mg three times daily) group or a placebo group for 6 weeks in a double-blind randomized study. The cough scores, medication scores, pulmonary function, bronchial hyperresponsiveness to methacholine, cough threshold for capsaicin, percentage of eosinophils and concentrations of eosinophilic cationic protein (ECP) in hypertonic saline-induced (induced) sputum were evaluated. The main outcome measures were capsaicin cough threshold and concentrations of ECP in induced sputum. RESULTS: In the suplatast group, the cough scores and the medication scores decreased significantly over time. The percentage of eosinophils in induced sputum significantly decreased from 53.5+/-5.6% to 13.6+/-2.6%. The cough threshold for capsaicin improved significantly from 2.72+/-3.41 microM to 39.7+/-22.7 microM in the suplatast group. The concentrations of ECP in induced sputum decreased significantly from 435+/-123 microg/l to 56+/-34 microg/l in the suplatast group. The bronchial responsiveness to methacholine changed from 8.45+/-3.43 units to 11.4+/-3.76 units in the suplatast group. CONCLUSIONS: Suplatast improved the cough scores and the cough threshold for capsaicin in patients with CVA without significant side effects, suggesting the effectiveness of suplatast in the treatment of CVA. Suplatast also decreased the percentage of eosinophils and concentrations of ECP in induced sputum, suggesting improvement in eosinophilic inflammation in patients with CVA. Further pharmacodynamic research is needed to explain the precise mechanism.  相似文献   
998.
We isolated a cDNA of 2001bp encoding the full-length precursor of flavoridin, which is one of the four disintegrins in the venom of Trimeresurus flavoviridis, and analyzed the cDNA nucleotide sequence. The deduced amino acid sequence of the open reading frame consisted of a pro-domain (190 residues), a metalloproteinase domain (205 residues), a spacer domain (18 residues) and a disintegrin (flavoridin) domain (70 residues), thus indicating that the flavoridin precursor belongs to the P-II class of snake venom metalloproteinases. The unknown metalloproteinase domain shared strong sequence similarity with HR2a (71.2% identity) and H(2)-proteinase (74.1% identity), a low molecular mass hemorrhagic metalloproteinase and a non-hemorrhagic metalloproteinase in the same snake venom, respectively.  相似文献   
999.
1000.
The unevenness of pulmonary nanoparticle (NP) distribution, which hinders the establishment of an absolute dose–response relationship, has been described as one of the limitations of intratracheal administration techniques for toxicological assessment of inhaled NPs. Quantification of the NP microdistribution would facilitate the establishment of a concentration–response relationship in localized regions of the lung; however, such quantitative methods have not been reported. Here, we established a quantitative method for evaluating pulmonary TiO2 NP microdistribution in rats using X‐ray fluorescence microscopy. Ti intensity in lung sections from rats intratracheally administered 10 mg kg–1 TiO2 NPs with a microsprayer was measured using X‐ray fluorescence with a 100 µm beam size. Ti reference samples were prepared by dropping different concentrations of Ti solutions on glass slide or lung sections of untreated rat. Ti intensity increased linearly with Ti content in the reference samples on both substrates. The detection limit of TiO2 was estimated to be 6.3 ng mm–2. The reproducibility was confirmed for measurements done in the short‐ (2 weeks) and long‐term (6 months). The quantitative results of TiO2 NP microdistribution suggested that more TiO2 NPs were distributed in the right caudal and accessory lobes, which are located downstream of the administration direction of the NP suspension, and the lower portion of each lobe. The detection rates of TiO2 NPs were 16.6–25.0%, 5.19–15.6%, 28.6–39.2%, 21.4–38.7% and 10.6–23.2% for lung sections from the right cranial, middle, caudal, accessory and left lobes, respectively. Copyright © 2015 John Wiley & Sons, Ltd.  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