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   8067篇
  免费   541篇
  国内免费   51篇
耳鼻咽喉   80篇
儿科学   347篇
妇产科学   205篇
基础医学   988篇
口腔科学   472篇
临床医学   658篇
内科学   1754篇
皮肤病学   185篇
神经病学   697篇
特种医学   588篇
外科学   891篇
综合类   62篇
一般理论   2篇
预防医学   735篇
眼科学   80篇
药学   519篇
中国医学   22篇
肿瘤学   374篇
  2023年   59篇
  2022年   138篇
  2021年   247篇
  2020年   152篇
  2019年   226篇
  2018年   268篇
  2017年   171篇
  2016年   201篇
  2015年   218篇
  2014年   282篇
  2013年   401篇
  2012年   528篇
  2011年   508篇
  2010年   331篇
  2009年   259篇
  2008年   380篇
  2007年   393篇
  2006年   351篇
  2005年   351篇
  2004年   257篇
  2003年   244篇
  2002年   258篇
  2001年   156篇
  2000年   152篇
  1999年   123篇
  1998年   170篇
  1997年   155篇
  1996年   158篇
  1995年   120篇
  1994年   95篇
  1993年   94篇
  1992年   92篇
  1991年   92篇
  1990年   77篇
  1989年   102篇
  1988年   83篇
  1987年   88篇
  1986年   76篇
  1985年   82篇
  1984年   50篇
  1983年   69篇
  1982年   54篇
  1981年   34篇
  1980年   47篇
  1979年   28篇
  1978年   29篇
  1977年   30篇
  1976年   34篇
  1975年   31篇
  1970年   14篇
排序方式: 共有8659条查询结果,搜索用时 15 毫秒
11.
1. alpha 2-Adrenoceptors on platelet membranes and beta 2-adrenoceptors on lymphocytes were studied in 24 patients with primary Raynaud's phenomenon and in 24 age- and sex-matched control subjects. In two subgroups, a standardized mental arithmetic test and a finger-cooling test were performed. 2. Baseline blood pressure, heart rate and forearm blood flow did not differ between the two groups. 3. Baseline skin microcirculation (laser Doppler flux) was decreased in primary Raynaud's phenomenon (19 +/- 15 arbitrary units) compared with control subjects (33 +/- 14 arbitrary units) (P less than 0.01). 4. Baseline plasma noradrenaline concentration (2.00 +/- 1.44 versus 1.16 +/- 0.36 nmol/l) and alpha 2-adrenoceptor density (301 +/- 119 versus 210 +/- 82 fmol/mg) were increased in patients with primary Raynaud's phenomenon in comparison with the control subjects. The alpha 2-adrenoceptor density/beta 2-adrenoceptor density ratio in patients with primary Raynaud's phenomenon was, with a value of 0.37 +/- 0.04, higher than in the control subjects, where a value of 0.25 +/- 0.02 was measured (P less than 0.001). Plasma adrenaline concentration, beta 2-adrenoceptor density and the antagonist affinity to both receptor subtypes did not differ between both groups under baseline conditions. 5. Whereas during the finger-cooling test no differences were seen in the responses of the parameters measured, the mental arithmetic test induced an increase in laser Doppler flux in patients with primary Raynaud's phenomenon and a decrease in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
12.
BACKGROUND: Our aims in the present study were to estimate the influences of pain and urinary symptoms on quality of life, and to determine which of these two variables has the most predictive power with respect to quality of life in young men with chronic prostatitis-like symptoms. METHODS: Chronic prostatitis-like symptoms were measured by the National Institutes of Health-Chronic Prostatitis Symptom Index. Of the 28,841 men aged 20 years who lived in the study community, 18,495 men (a response rate 64.1%) agreed to participate in the study. A total of 1057 men who complained of symptoms indicative of chronic prostatitis were included in the study. The influences of pain and urinary symptoms on quality of life were determined using logistic regression analysis. The receiver operating characteristic (ROC) curve was used to estimate the predictive ability of each of these variables with respect to quality of life. RESULTS: Results from multivariate analysis showed that both pain and urinary symptoms were associated with an increased likelihood of impaired quality of life, although pain contributed more to a reduced quality of life than urinary symptoms. Relative to men who experienced mild pain, men who experienced moderate pain had a 3.9-fold risk of poor quality of life (odds ratio [OR], 3.87; 95% confidence interval [CI], 2.86-5.23; P < 0.001) and those who experienced severe pain had a 15.7-fold risk of reduced quality of life (OR, 15.68; 95% CI, 6.59-37.35; P < 0.001). Moderate urinary symptoms were associated with a 1.4-fold risk of bother (OR, 1.41; 95% CI, 1.01-1.99; P < 0.001) and severe urinary symptoms were associated with 2.4-fold risk (OR, 2.39; 95% CI, 1.37-4.12; P < 0.001), relative to mild urinary symptoms. Comparison of the effects of pain and urinary symptoms showed that pain severity had the most predictive power for bother, quality of life, and quality-of-life impact. The areas under the ROC curves for bother, quality of life, and quality-of-life impact were 71.3%, 69.3% and 72.5%, respectively. CONCLUSION: Urinary symptoms and pain might be associated with an increased likelihood of impaired quality of life in young men with chronic prostatitis-like symptoms. In addition, our findings suggest that pain severity is the most influential variable for determining quality of life in this population.  相似文献   
13.
Phospholipidosis (PLD) is characterized by an intracellular accumulation of phospholipids in lysosomes and the concurrent development of concentric lamellar bodies. Recently, H. Sawada et al. (2005, Toxicol. Sci. 83, 282-292) identified 17 genes as potential biomarkers of PLD in HepG2 cells. The present study was undertaken to determine if this set of genes measured by quantitative PCR could be validated in the same cell line. The objective was also to investigate the dose-response relationship to further validate the assay and to select the concentrations to use for screening activities. In a first experiment (one concentration tested), out of the 17 genes, the best gene biomarkers of PLD (i.e., 11 genes) were selected for practical screening reasons. Based on these genes, 91.6% (i.e., 11 of 12) of the compounds known to induce PLD were identified as positive and all the negative compounds (i.e., five of five) were also confirmed. When the data obtained in the first experiment were compared to the data by Sawada et al., (2005) the coefficient of correlation calculated was slightly higher than 75%. In the second experiment (26 compounds [all 17 compounds from the first experiment plus 9 other compounds] tested at a minimum of three concentrations), 93.3% (14/15) of the compounds known to induce PLD were identified as such and all the negative controls (six compounds) were also confirmed. Three compounds likely to induce PLD were identified as positive in our assay. Finally, two compounds for which no data are available were also tested. When both experiments 1 and 2 were compared, the coefficient of correlation for 16 compounds tested at the same concentrations reached 87.7%. In conclusion, the present study further confirms the utility of gene expression in HepG2 cells to identify a potential to induce PLD. Finally, based on the data presented, researchers are encouraged to use a range of minimum three concentrations (e.g., 12.5, 25, and 50 microM) to screen for PLD in the human HepG2 cell line.  相似文献   
14.
15.
16.
Objective. The medical practitioner is faced with an increasing list of protocols and algorithms related to patient care. These recommendations are often difficult to recall, particularly in stressful emergency situations. Using advanced cardiac life support (ACLS) protocols, we built a computer-based system to exhibit precompiled response plans for medical emergencies. To validate the usefulness of this prompting device, we tested application of two of the nine ACLS algorithms, pulseless ventricular fibrillation/ventricular tachycardia (Vfib/Vtach) and bradycardia, in a simulated operating room (OR) environment.Methods. The system utilized the software authoring system IconAuthor (Aimtec Inc., Nashua, NH) and a touch-screen monitor (DiamondScan, Microtouch, Methuen, MA). Prior to testing our system, all 39 subjects were given time to familiarize themselves with its operation. Subsequently, all subjects were videotaped while managing a standard simulated anesthetic. During the anesthetic, the subjects were presented with two emergency scenarios, not viewed during the familiarization period. The electrocardiographic (EKG) signals for normal sinus rhythm, ventricular fibrillation, and second-degree heart block were presented. By random selection, the prompter was available to half of the subjects for help with arrhythmia management (experimental group), while to half it was not (control group).Results. A total of 39 subjects completed the exercise. Use of the prompter enabled significantly more subjects to administer correct drugs and dosages during ventricular fibrillation. The correct lidocaine dose was chosen more often by the experimental group than by the control (p=0.015); similarly MgSO4 was appropriately ordered more often in the experimental group (p=0.003). During second-degree heart block, atropine was correctly followed with a dopamine infusion (p=0.004), and epinephrine infusion was ordered for refractory bradycardia (p=0.002) more often in the experimental than the control group.Conclusions. These data demonstrate the value of a prompting device at the anesthesia workstation. We foresee the use of such prompters in many areas of medicine.This study was made possible by a grant from the Anesthesia Patient Safety Foundation. Results were presented, in part, at the meeting of the STA/SEA Orlando, Florida, January 1994.  相似文献   
17.
18.
Studies were carried out to investigate the metabolism of senecionine by human liver microsomes and the role of human cytochrome P450IIIA4 in this process. Human liver microsomes metabolized senecionine to two major products, (+/-)-6,7-dihydro-7-hydroxy-1-hydroxymethyl-5H-pyrrolizine (DHP) and senecionine N-oxide. The rates of product formation (DHP and senecionine N-oxide) varied widely with the microsomal samples tested. There was a 30-fold difference in DHP formation and a 25-fold difference in N-oxidation between the poorest metabolizer and the highest metabolizer of senecionine. The conversion of senecionine to DHP and senecionine N-oxide in human liver microsomes was markedly inhibited by the mechanism-based inactivators of P450IIIA4, gestodene and triacetyloleandomycin. Anti-P450IIIA4 IgG, at a concentration of 1 mg/nmol of P450, was found to inhibit completely the formation of DHP and senecionine N-oxide in human liver microsomes (HL101) having low activity toward senecionine. At 5 mg IgG/nmol P450, anti-P450IIIA4 inhibited 90 and 84% respectively of the formation of DHP and senecionine N-oxide in liver microsomes (HL110) with the highest activity toward senecionine. The formation of DHP or senecionine N-oxide was highly correlated with the amount of P450IIIA4 measured in the microsomes using polyclonal anti-P450IIIA4 IgG. The rate of DHP production also had a strong correlation with the rate of senecionine N-oxide formation (r = 0.999) and with the rate of nifedipine oxidation (r = 0.998). Our present studies provide evidence that P450IIIA4 is the major enzyme catalyzing the bioactivation (DHP formation) and detoxication (senecionine N-oxide formation) of senecionine in human liver.  相似文献   
19.
After total gastrectomy, the ileocecal graft may act as a reservoir and protect against reflux but give rise to transposition of the ileum and cause possible changes in bile acid metabolism and nutrition. This study compared the ileocecal graft and jejunal pouch. Male Wistar rats weighing 265 +/- 22 g were submitted to sham operation (S), ileocecal interposition graft (IIG), and jejunal pouch interposition graft (JP) after total gastrectomy. Eight weeks later, the esophagus was examined for evidence of esophagitis. Nutritional biochemistry and weight profile were documented preoperatively and 8 weeks after surgery. The oral glucose tolerance test was performed. Thirty-three rats were operated on and 30 survived for 8 weeks. Esophagitis occurred in seven JP rats. Body weight was significantly higher in IIG than in JP rats (p < .05). Normal glucose tolerance to intragastric glucose load was observed in sham and operated rats. JP rats had a significant decrease in serum albumin, glucose, transferrin, hemoglobin, iron, folate, and calcium, compared to sham (p < .05). Cobalamine was significantly lower in IIG rats than in JP rats (p < .05). In the IIG and JP groups, serum/hepatic total bile acid did not differ significantly from preoperative and sham values. In conclusion, the IIG interposition graft in rats prevented esophagitis, preserved nutrition, and did not interfere with enterohepatic total bile acid circulation.  相似文献   
20.
Forty-six patients in the postoperative period of proximal gastric vagotomy (PGV) for duodenal ulcer (DU) were studied comparatively to verify whether the dividing of the gastroepiploic nerves (Rosati's maneuver) can reduce or not the occurrence of recurrent ulcer as it was proposed. Twenty-one patients who underwent PGV associated with Rosati's maneuver (PGV-R) were compared to 25 after standard PGV (PGV-S), according to several criteria: (1) clinical evaluation; (2) pre and postoperative basal and pentagastrin-stimulated gastric acidity; (3) postoperative basal and pentagastrin-stimulated serum pepsinogen; (4) postoperative basal and sham feeding-stimulated serum gastrin; (5) postoperative endoscopy; (6) endoscopic Congo red test. Both groups were similar (P greater than 0.05) as to age, sex, levels of preoperative gastric acidity and had a 24.4 month average follow-up (12 to 58 months). There has been no significant difference between the techniques studied as to clinical, secretory, morphological or hormonal gastric tests, although PGV-R proved more effective in reducing basal gastric acidity than PGV-S (P less than 0.05). We concluded that Rosati's maneuver does not improve the results obtained with PGV, although it provided greater reduction of basal gastric acidity than PGV-S.  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