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   6443篇
  免费   492篇
  国内免费   10篇
耳鼻咽喉   52篇
儿科学   239篇
妇产科学   178篇
基础医学   881篇
口腔科学   245篇
临床医学   647篇
内科学   1169篇
皮肤病学   65篇
神经病学   490篇
特种医学   161篇
外科学   1033篇
综合类   86篇
一般理论   18篇
预防医学   524篇
眼科学   50篇
药学   530篇
中国医学   1篇
肿瘤学   576篇
  2022年   47篇
  2021年   88篇
  2020年   71篇
  2019年   101篇
  2018年   112篇
  2017年   99篇
  2016年   109篇
  2015年   120篇
  2014年   177篇
  2013年   269篇
  2012年   380篇
  2011年   353篇
  2010年   181篇
  2009年   186篇
  2008年   265篇
  2007年   270篇
  2006年   289篇
  2005年   285篇
  2004年   269篇
  2003年   222篇
  2002年   195篇
  2001年   189篇
  2000年   194篇
  1999年   183篇
  1998年   72篇
  1997年   66篇
  1996年   77篇
  1995年   61篇
  1994年   55篇
  1993年   41篇
  1992年   158篇
  1991年   107篇
  1990年   106篇
  1989年   106篇
  1988年   120篇
  1987年   132篇
  1986年   100篇
  1985年   96篇
  1984年   69篇
  1983年   59篇
  1982年   54篇
  1981年   38篇
  1980年   38篇
  1979年   73篇
  1978年   41篇
  1977年   46篇
  1975年   51篇
  1974年   57篇
  1973年   48篇
  1972年   42篇
排序方式: 共有6945条查询结果,搜索用时 21 毫秒
101.
PURPOSE: We assess the effect of finasteride, a 5alpha-reductase inhibitor, on objective voiding parameters in men with lower urinary tract symptoms and benign prostatic enlargement on digital rectal examination (known as clinical benign prostatic enlargement) in a double-blind placebo controlled multicenter study using strict standard pressure flow study techniques. MATERIALS AND METHODS: A modification of the Abrams-Griffiths nomogram was used by 1 reader to ensure that all patients met objective criteria for bladder outlet obstruction at baseline. After performing a pressure flow study patients with obstruction were randomized 2:1 to receive 5 mg. finasteride (81) or placebo (40) daily. A second pressure flow study was performed at month 12. At baseline and month 12 free urinary flow studies and transrectal ultrasound were performed, and International Prostate Symptom Score questionnaires were completed. Patients were treated between May 1994 and July 1996. RESULTS: Finasteride caused a significant decrease (-8.1 cm. water) in detrusor pressure at maximum flow (p <0.05 versus placebo p = 0.02), increase (+1.1 ml. per second) in maximum flow rate (p <0.05 versus placebo p = 0.02) and decrease (-22.8%) in prostate volume (p <0.05 versus placebo p <0.001). Men with prostates larger than 40 cc had greater improvement in detrusor pressure at maximum flow (between group difference -14.5 cm. water, 95% confidence interval -26.2 to -2.6, p = 0.02) and maximum flow rate (mean treatment effect +1.6 ml. per second, 95% confidence interval -0.2 to 3.0, p = 0.02) compared to those with prostates 40 cc or less (between group differences not significant). CONCLUSIONS: Finasteride treatment resulted in improvements in urodynamic parameters, which were greater in men with large prostates.  相似文献   
102.
103.
PURPOSE: The aim of this study was to investigate the changes in biometric measurements and corresponding refractive errors during a three-year period among university students exposed to high educational demands. METHODS: A three-year longitudinal cohort study was performed among 149 Norwegian engineering students (79 females and 70 males, mean age 20.6+/-1.2 years) measuring their refraction and ocular dimensions at the beginning and at the end of the period. The examinations included refraction, keratometry, and A-scan ultrasonographic measurements of the ocular components, all made in cycloplegia. RESULTS: After three years the mean refractive change was -0.52+/-0.45 D (p<0.05), which was accompanied by a change in lens thickness of 0.07+/-0.10 mm (p<0.05), and a vitreous chamber elongation of 0.27+/-0.30 mm (p<0.05). The results refer to the right eye. Stratification of the sample based on their initial refraction (myopes, emmetropes, and hyperopes) showed refractive change towards myopia for all subgroups as well as a significant increase in lens thickness and vitreous chamber depth. No significant three-year change in anterior chamber depth or corneal curvature was found in any of the groups. For all groups, vitreous chamber elongation gave a notable dioptric change in myopic direction. CONCLUSIONS: A shift in refraction towards myopia after puberty is accompanied by vitreous chamber elongation which can explain the dioptric change in myopic direction.  相似文献   
104.
Our goal was to develop an animal model of cavernous nerve injury similar to that encountered among patients having undergone a successful nerve sparing radical prostatectomy and to compare patterns of nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase staining to quality of erections using the newly developed model. We studied 50 mature Sprague Dawley rats, which were divided into five equal groups. Animals were either observed (sham), underwent an exploratory laparotomy, underwent moderate or severe percussive injury to both cavernous nerves, or underwent ablation of both cavernous nerves. Between 28 and 30 days later, all animals underwent electrostimulation and simultaneous recording of intracavernosal pressure. After sacrifice, penes were harvested and penile tissue NADPH-diaphorase staining pattern was assessed. Severity of cavernous nerve percussive injury and NADPH-diaphorase staining patterns correlated with the quality of recorded erections. This model is a useful experimental tool for research in the field of erectile dysfunction such as is encountered following a successful nerve sparing radical prostatectomy. Penile biopsy assessing NADPH-diaphorase staining may potentially prove to be a useful minimally-invasive diagnostic modality quantifying neurogenic erectile function among patients following radical prostatectomy.  相似文献   
105.
106.
Summary The mixed haemagglutination technique was used to demonstrate IgG antibodies to peripheral nerve tissue in sera from patients with the Guillain-Barré syndrome. The clinical effect and the effect on the antibodies of plasma exchange were examined in 18 patients. Neurological examination with muscle testing and neurophysiological examination of the patients were performed before and immediately after plasma exchange. Before the exchange antibodies were detected in sera from 11 of the patients. These patients showed clinical improvement during the treatment. After plasma exchange, antibodies were detected in sera from only two of the patients. The seven patients without detectable antibodies showed no clinical improvement.
Zusammenfassung Bei 18 Patienten mit Guillain-Barré Syndrom, die einem therapeutischen Plasmaaustausch (PA) unterzogen wurden, wurde das Serum mit Hilfe einer gemischten Hämagglutinations-Technik auf IgG-Antikörper (IgG-AK) gegen peripheres Nervengewebe untersucht. Einfluß der PA auf den klinischen Zustand und Titerverlauf wurden verglichen: Bei 11 Patienten wurden IgG-AK gefunden; sie zeigten unter der PA eine klinisch verifizierte Besserung, die in einigen Fällen auch elektromyographisch gesichert werden konnte; nach Beendigung der PA waren nur noch in 2 Fällen IgG-AK nach-weisbar. Bei den restlichen 7 Patienten fehlten IgG-AK; bei ihnen war die PA ohne Effekt.
  相似文献   
107.
A total number of 27 premature infants with idiopathic respiratory distress syndrome (IRDS) and 52 healthy controls with comparable gestational age and body weights were studied during the first month of life. In infants with IRDS a reduced thyrotropin (TSH) response to birth was suggested, as serum TSH was lower in IRDS patients than in controls during the first two days of life. Low serum concentrations of thyroid hormones were found in the acute stage of IRDS reaching minimal values by day 3--5. After that period an increase in thyroid hormone levels occurred. The serum T2 increased to the level of healthy prematures by day 6--10, whereas the serum T4 increased to normal levels by day 21--30. Serum concentrations of thyroxine-binding globulin (TBG) were significantly lower in IRDS patients than in healthy controls; a gradual increase to normal levels occurred during recovery. Serum prealbumin (TBPA) levels in IRDS infants increased rapidly after birth and exceeded levels of healthy infants. Serum albumin values were not significantly different in the two groups of infants. The serum T4/TBG ratios were low during recovery from IRDS.  相似文献   
108.
Summary The pharmacokinetics of a new high ceiling diuretic, muzolimine (Bay g 2821), were investigated after a single oral dose of 40 mg in 7 patients with cardiac failure (Stages I–IV, New York Heart Association classification), and in 2 healthy subjects. Plasma concentrations peaked 1–3 h after administration and declined according to a two-compartment model. The -phase (distribution phase) lasted until 12–16 h after administration and the mean t1/2 was 3.6 h (range 2.3–4.7) in patients, and 2.6 h (range 2.3–2.9) in healthy subjects. The mean t1/2 was 13.5 h (range 7.4–22.4) in the patients and 14.0 h (range 12.4–14.6) in healthy subjects. T1/2 was not correlated with the degree of heart failure or with the area beneath the plasma concentration curve, which varied three-fold. The renal clearance of muzolimine was in the range 2.7–15.3 ml · min–1 in 5 subjects in whom it was investigated. The pharmacokinetics of muzolimine appear not to be significantly altered by cardiac failure. The prolonged half-lives of the drug are probably responsible for the longer duration of diuretic action reported for muzolimine than for furosemide and bumetamide.  相似文献   
109.
Steady-state kinetics of imipramine in patients   总被引:1,自引:0,他引:1  
Steady-state plasma level kinetics were studied in 76 patients given imipramine (IP) 150 to 225 mg/day for 2–5 weeks. IP was given in three divided doses at 8.00 a.m., 1.00 p.m. and 5.00 p.m. Plasma concentrations of IP and its active metabolite desipramine (DMI) were determined by quantitative in situ thin-layer chromatography. The plasma levels of IP and DMI showed pronounced flucutations throughout the day with a ratio of about 2 between highest and lowest level. Patients with steady-state levels of IP and/or DMI below 50 g/l reached this within 1 week of treatment. Patients with higher steady-state levels reached steady-state concentrations within 2–3 weeks. There were some intraindividual fluctuations in plasma levels from week to week after steady state had been reached (coefficient of variation: 10–20%). Interindividually, the steady-state levels corrected to a dose of 3.5 mg/kg per day varied considerably: IP: 6–356 g/l, DMI: 24–659 g/l and IP+DMI: 58–809 g/l. The steady-state plasma levels showed a skew distribution that became normal by logarithmic transformation. The IP/DMI ratio ranged from 0.07 to 5.5 with a median value of 0.47. Compared to data from amitriptyline treated patients the IP/DMI ratios had significantly lower median value and larger variation than the corresponding plasma level ratios of amitriptyline/nortriptyline. Several statistically significant differences in steady-state levels between age groups were found. For IP: Women aged 30–39 had lower levels than women aged 20–29, 40–49, and 50–59, and men aged 50–59 and 60–65; men aged 30–39 had lower levels than men aged 60–65. For DMI: Women aged 30–39 had lower levels than women aged 50–59.  相似文献   
110.
OBJECTIVE: Recent work has underscored the role of serotonergic neurotransmission in chronic neural adaptations to cocaine dependence. The authors tested for evidence of serotonergic dysfunction during acute abstinence from cocaine, a period of high risk for relapse in cocaine dependence.METHOD: Binding availability of dopamine transporters and serotonin transporters was measured in 15 cocaine-dependent subjects during acute abstinence and in 37 healthy comparison subjects by using [(123)I]beta-CIT and single photon emission computed tomography.RESULTS: Significant increases in diencephalic and brainstem serotonin transporter binding (16.7% and 31.6%, respectively) were observed in cocaine-dependent subjects. Brainstem serotonin transporter binding was significantly inversely correlated with age across diagnostic groups.CONCLUSIONS: These findings provide further evidence of serotonergic dysfunction during acute abstinence from chronic cocaine use. Age-related decline in brainstem serotonin transporter binding may underlie the poor response to selective serotonin reuptake inhibitor antidepressants seen in some elderly depressed patients.  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