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   2040篇
  免费   120篇
  国内免费   142篇
耳鼻咽喉   12篇
儿科学   39篇
妇产科学   73篇
基础医学   242篇
口腔科学   50篇
临床医学   288篇
内科学   402篇
皮肤病学   29篇
神经病学   166篇
特种医学   118篇
外科学   171篇
综合类   113篇
预防医学   139篇
眼科学   61篇
药学   271篇
中国医学   27篇
肿瘤学   101篇
  2023年   5篇
  2022年   6篇
  2021年   31篇
  2020年   25篇
  2019年   31篇
  2018年   55篇
  2017年   24篇
  2016年   40篇
  2015年   64篇
  2014年   74篇
  2013年   112篇
  2012年   103篇
  2011年   150篇
  2010年   90篇
  2009年   91篇
  2008年   108篇
  2007年   174篇
  2006年   114篇
  2005年   112篇
  2004年   89篇
  2003年   79篇
  2002年   69篇
  2001年   65篇
  2000年   45篇
  1999年   32篇
  1998年   55篇
  1997年   49篇
  1996年   42篇
  1995年   32篇
  1994年   35篇
  1993年   30篇
  1992年   27篇
  1991年   22篇
  1990年   22篇
  1989年   26篇
  1988年   34篇
  1987年   21篇
  1986年   19篇
  1985年   16篇
  1984年   9篇
  1983年   8篇
  1982年   7篇
  1981年   8篇
  1980年   8篇
  1977年   5篇
  1976年   5篇
  1975年   5篇
  1973年   3篇
  1958年   14篇
  1955年   4篇
排序方式: 共有2302条查询结果,搜索用时 15 毫秒
101.
Purpose: To evaluate the accuracy of corneal surgically induced astigmatism (SIA) estimation when neglecting the posterior corneal surface measurement. Methods: Fifty right eyes undergoing phacoemulsification were measured with a rotating Scheimpflug camera (Pentacam; Oculus Inc., Wetzlar, Germany) both before and after surgery. Clear corneal incisions with one suture were used in the phacoemulsification surgery. The keratometric corneal SIA (KSIA) was derived using the anterior corneal surface measurement and the keratometric index (1.3375) while neglecting the posterior corneal surface measurement. The Pentacam‐derived total corneal SIA (PSIA) was derived by vergence tracing and polar value analysis [KP(135) and KP(180)] of the measurements on both corneal surfaces. Results: The mean arithmetic estimation errors of the KSIA for the PSIA were 0.16 ± 0.32 (?0.52 to 1.14) D for the KP(135), and ?0.02 ± 0.30 (?0.75 to 1.29) D for the KP(180). There was a significant difference between the KP(135) components of the KSIA and PSIA. Bivariate analysis revealed a statistically significant difference between the combined means of the KSIA and PSIA. Overall, 24% had either a KP(135) component of the KSIA that differed by > 0.50 D from that of the PSIA or a KP(180) component of the KSIA that differed by > 0.50 D from that of the PSIA. The blurring strength caused by neglecting the posterior corneal measurement was > 0.50 D in 24% of eyes. Conclusion: Neglecting the posterior corneal surface measurement may lead to significant deviation in the corneal SIA estimation after phacoemulsification in a proportion of eyes.  相似文献   
102.
Aim: Findings of hypoxia prior to death and involvement of a dysregulation of the serotonergic network in sudden infant death syndrome (SIDS) may indicate that brain‐derived neutrophic factor (BDNF) also is of importance with regard to sudden unexpected infant death. Based on this, the purpose of this study was to investigate the BDNF val66met polymorphism in SIDS cases, cases of infectious death and controls. Methods: The polymorphism was investigated in 163 SIDS cases, 34 cases of infectious death and 121 controls, using real‐time PCR and fluorescence melting curve analysis. Results: There were no differences in val66met genotype distribution between neither the SIDS cases nor the cases of infectious death and controls (p = 0.95 and p = 0.52, respectively). Conclusion: The study indicates that the val66met polymorphism is not important for sudden unexpected infant death. However, several other SNPs in the BDNF gene, as well as in other genes involved in this pathway, including G‐protein, have to be investigated to fully exclude any involvement of BDNF in SIDS.  相似文献   
103.
Men who have sex with men (MSM) are the demographic group most severely affected by HIV in the USA. Global association studies have shown that MSM who binge drink are more likely to engage in risky sexual behaviors and day- and event-level analyses have linked binge drinking to sexual risk behavior on specific days and during specific sexual encounters. Despite this strong foundation of research, no studies have examined the association between the frequency of situational binge drinking (i.e., binge drinking concurrent with sexual activity) and aggregated sexual risk over periods of longer duration. We used multivariable logistic regression to assess the relationship between situational binge drinking (i.e., binge drinking concurrent with anal intercourse) and condomless anal intercourse (CAI) and among a cross-sectional sample of 124 MSM in San Francisco, CA. There was a positive relationship between frequency of situational binge drinking and CAI (1–5 times vs. never: adjusted odds ratio?=?2.78, 95% CI?=?1.01–7.63; 6–10 times vs. never: 6.19, 1.27–30.22; more than 10 times vs. never: 11.88, 1.31–107.60). By filling a methodological gap and complementing existing global and event-level analyses, this positive situational relationship strengthens the evidence linking binge drinking and sexual risk, enhances the comparability of the existing literature, and further suggests that the integration of dual strategies that aim to prevent HIV and reduce binge drinking may be warranted.  相似文献   
104.

Background  

The purpose of this study was to evaluate two commercial hemodialyzers (F100 and P21) through the clearance of identified and unidentified uremic solutes.  相似文献   
105.
Purpose: Temporal lobe epilepsy (TLE) is the most common focal epilepsy and frequently causes memory problems. It is often associated with hippocampal sclerosis (HS) and is useful in exploring memory functions. We aimed to examine the effect of restricted hippocampal lesions on gist memory function in patients with TLE. Methods: Forty‐five patients with TLE and HS (16 left, 15 right, and 14 bilateral lesions) and 22 control subjects were recruited. Patients with magnetic resonance imaging (MRI) or electroencephalography (EEG) evidence of extratemporal lesions were excluded. All participants performed a gist‐based recognition task following the Deese‐Roediger‐McDermott paradigm and were tested for verbal IQ and memory functions. We conducted hippocampal volumetry on MRI of all the participants. Results: Patients showed multidomain memory impairments. Gist memory was impaired in patients with bilateral HS and probably in patients with right HS. Hippocampal volumetry supported such findings that total volume of hippocampi and volume of right hippocampus correlated positively with gist memory function. Discussion: HS has a dose effect and a probable right dominance effect on gist memory; good item memory supports gist memory performance; and a disproportionate deficit was noted in tasks with high relational demand but not in tasks with simple association. We should develop memory skills for patients with TLE by enhancing performance of gist memory related to simple association task.  相似文献   
106.
107.
This study was designed to evaluate the association between the aminolevulinate dehydrogenase (ALAD) genotype and blood lead levels in a general population environmentally exposed to lead. This study population of 660 subjects was secondarily sampled from the 3000 random samples of Taiwanese general population to study the distribution of blood lead levels in the Taiwanese population. A simple assay based on the polymerase chain reaction-restriction fragment length polymorphism technique was used to determine the genotype of the ALAD gene. This study found that most of the Taiwanese population was ALAD 1-1 (95.4%). Only 4.6% (30 subjects) of population were found to be 1-2 or 2-2. It has been hypothesized that the ALAD2 allele is associated with increased absorption of lead. This study found that individuals with ALAD2 alleles had 20% higher blood lead levels than persons with ALAD1 alleles (7.83 +/- 5.95 vs 6.51 +/- 5.03 micrograms/dL). However, the difference was not statistically significant, even after adjustment for other risk factors of environmental exposure. The result supports the previous finding that individuals with ALAD2 allele had higher blood lead levels. The small sample size and large amount of variation in our study may account for the insignificant association.  相似文献   
108.
109.
BACKGROUND: Thyrotoxic periodic paralysis (TPP) commonly precedes the overt symptoms and signs of hyperthyroidism and may be misdiagnosed as other causes of paralysis (non-TPP). Because the cardiovascular system is very sensitive to elevation of thyroid hormone, we hypothesize that electrocardiographic manifestations may aid in early diagnosis of TPP. METHODS: We retrospectively identified 54 patients who presented to the emergency department (ED) with hypokalemic paralysis during a 3.5-year period. Thirty-one patients had TPP and 23 patients had non-TPP, including sporadic periodic paralysis, distal renal tubular acidosis, diuretic use, licorice intoxication, primary hyperaldosteronism, and Bartter-like syndrome. Electrocardiograms during attacks were analyzed for rate, rhythm, conduction, PR interval, QRS voltage, ST segment, QT interval, U waves, and T waves. RESULTS: There were no significant differences in age, sex distribution, and plasma K+ concentration between the TPP and non-TPP groups. Plasma phosphate was significantly lower in TPP than non-TPP. Heart rate, PR interval, and QRS voltage were significantly higher in TPP than non-TPP. Forty-five percent of TPP patients had first-degree atrioventricular block compared with 13% in the non-TPP group. There were no significant differences in QT shortening, ST depression, U wave appearance, or T wave flattening between the 2 groups. CONCLUSION: Relatively rapid heart rate, high QRS voltage, and first-degree AV block are important clues suggesting TPP in patients who present with hypokalemia and paralysis.  相似文献   
110.
We describe a new method for treating livedoid vasculopathy. The typical presentation of livedoid vasculopathy includes chronic, recurrent painful ulcers, satellite scar-like atrophy and telangiectasia involving the lower extremities. Histologically, these lesions show areas of ulceration and dermal vessel occlusion without frank inflammatory cell infiltration. There is currently no satisfactory therapy available for this disease. Hyperbaric oxygen (HBO) has recently established itself as one of the most effective methods of treating ischaemic wounds, including diabetic ulcers. We used this therapy in two patients whose lesions were resistant to multiple therapeutic modalities. Not only did their ulcers respond rapidly to the HBO therapy, but the disturbing wound pain also resolved at the same time. To our knowledge, this is the first successful trial of HBO therapy in livedoid vasculopathy. We believe this to be a very promising new therapy for livedoid vasculopathy and to be worth further investigation.  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