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   811篇
  免费   44篇
  国内免费   14篇
耳鼻咽喉   7篇
儿科学   26篇
妇产科学   9篇
基础医学   109篇
口腔科学   16篇
临床医学   43篇
内科学   134篇
皮肤病学   7篇
神经病学   138篇
特种医学   155篇
外科学   90篇
综合类   12篇
一般理论   1篇
预防医学   42篇
眼科学   11篇
药学   41篇
肿瘤学   28篇
  2021年   12篇
  2020年   5篇
  2019年   5篇
  2018年   16篇
  2017年   10篇
  2016年   4篇
  2015年   18篇
  2014年   13篇
  2013年   19篇
  2012年   20篇
  2011年   35篇
  2010年   21篇
  2009年   26篇
  2008年   28篇
  2007年   32篇
  2006年   17篇
  2005年   26篇
  2004年   27篇
  2003年   23篇
  2002年   15篇
  2001年   24篇
  2000年   23篇
  1999年   27篇
  1998年   29篇
  1997年   25篇
  1996年   29篇
  1995年   19篇
  1994年   20篇
  1993年   12篇
  1992年   19篇
  1991年   12篇
  1990年   9篇
  1989年   20篇
  1988年   11篇
  1987年   12篇
  1986年   14篇
  1985年   20篇
  1984年   8篇
  1983年   22篇
  1982年   19篇
  1981年   19篇
  1980年   14篇
  1979年   7篇
  1978年   12篇
  1977年   17篇
  1976年   12篇
  1975年   5篇
  1974年   4篇
  1968年   5篇
  1966年   4篇
排序方式: 共有869条查询结果,搜索用时 15 毫秒
1.
Brain morphology was examined using magnetic resonance imaging in 30 first-episode patients with a schizophreniclike psychosis, 15 chronic schizophrenics, and 20 neurological controls. Statistical analyses of computer-generated measurements of regions of interest were controlled for gender, age, social class, and total brain volume. Lateral ventricular size was increased in both first-episode and chronic schizophrenic patients, with greater significance on the left than on the right side. Only the chronic patients, however, had reduced temporal lobe size, which also was greater on the left side. No major correlations of regional brain morphological measurements with cognitive functioning were found, although some measurements of verbal memory were correlated with parahippocampal size. This is a report of a preliminary study that suggests that some morphological brain changes may be present at the time of first treatment for a psychotic illness, whereas others may occur later in the course of illness. Future prospective studies may determine the clinical significance of these changes and whether they progress with the development of illness chronicity.  相似文献   
2.
N-Nitrosodibutylamine (NDBA) and its omega-oxidized metabolites N-nitrosobutyl-4-hydroxybutylamine (4-OH-NDBA) and N-nitrosobutyl-3-carboxypropylamine (BCPN) are potent urinary bladder carcinogens. To study putative organ specific activation of BCPN, its alpha-oxidation by liver and urinary bladder microsomal fractions was investigated in comparison to NDBA and 4-OH-NDBA. Additionally, induction of DNA single strand breaks (SSB) was monitored in hepatocytes and in a human lymphoblastoid cell line (Namalva) in the presence and absence of external metabolic activation, including N-nitroso-t-butyl-n-butylamine as a negative control. BCPN was alpha-hydroxylated and dealkylated at both alkyl chains in small rates (about 1 nmol x mg protein-1 x 60 min-1) by microsomes from rat liver and pig urinary bladder epithelium. NDBA and 4-OH-NDBA were dealkylated at similarly low rates by pig urinary bladder microsomes, in strong contrast to the high debutylation rates observed for rat liver microsomes. Correspondingly, SSB induction by NDBA and 4-OH-NDBA was observed in Namalva cells with NDBA and 4-OH-NDBA in the presence of PB-induced rat liver microsomes but not with urinary bladder microsomes or without external activation. BCPN did not induce DNA-damage in Namalva cells (with or without external activation) or in rat hepatocytes. Significant induction of sister chromatid exchanges (SCEs) and micronuclei, however, was observed in Namalva cells after incubation with NDBA and BCPN. Our data suggest activation of BCPN via alpha-oxidation in the urinary bladder, even though activation rate in-vitro is so low that a positive response is not detectable by several short-term tests.  相似文献   
3.
Many patients still suffer from unnessesary pain in the postoperative period. Waiting for new technologies or drugs will not improve the status of acute pain management. The establishment of an acute service is needed to reduce the incidence of postoperative pain. Acute pain therapy is one of the great challenges we have to take up.  相似文献   
4.
5.

Introduction

Soft tissue reactions following metal-on-metal (MoM) arthroplasty of the hip have been under considerable discussion. These reactions are seen following both hip resurfacing and MoM total hip arthroplasty (THA). The phenomenon may arise owing to shedding of metal particles in high wear states, hypersensitivity with normal metal wear rates or a combination of the two.

Methods

Three patients were identified who had developed a soft tissue reaction (pseudotumour) following MoM hip resurfacing procedures. The prostheses were revised to ceramic-on-ceramic (CoC) THA with only minimal debridement of the pseudotumour. Pre and postoperative magnetic resonance imaging was performed to assess the size of the lesions.

Results

Progressive and satisfactory resolution of the associated pseudotumours was identified following revision of the prostheses to CoC THA.

Conclusions

In the early stages of pseudotumour formation following MoM hip resurfacing, this potentially devastating condition can be managed adequately with revision to a CoC bearing THA with minimal soft tissue excision.  相似文献   
6.
7.
Embury  SH; Gholson  MA; Gillette  P; Rieder  RF 《Blood》1985,65(3):769-771
We have identified a black individual with homozygous sickle cell anemia who is the silent carrier of alpha-thalassemia (genotype - alpha/alpha alpha) due to heterozygosity for the leftward deletion alpha-thal-2 haplotype. This deletion has not been described previously in a black subject and is the only leftward deletion that we have found among 255 alpha-thal-2 chromosomes from sickle cell subjects. Its effects on the clinical, hematologic, biosynthetic, and cellular pathology of sickle cell anemia resemble those reported for the common alpha-thalassemia genotypes of the black population.  相似文献   
8.
Electromyography (EMG) of the shoulder girdle is commonly performed; however, EMG spectral properties of shoulder muscles have not been clearly defined. The purpose of this study was to determine the maximum power frequency, Nyquist rate, and minimum sampling rate for indwelling and surface EMG of the normal shoulder girdle musculature. EMG signals were recorded using indwelling electrodes for the rotator cuff muscles and surface electrodes for ten additional shoulder muscles in ten healthy volunteers. A fast Fourier transform was performed on the raw EMG signal collected during maximal isometric contractions to derive the power spectral density. The 95% power frequency was calculated during the ramp and plateau subphase of each contraction. Data were analyzed with analysis of variance (ANOVA) and paired t tests. Indwelling EMG signals had more than twice the frequency content of surface EMG signals (p < .001). Mean 95% power frequencies ranged from 495 to 560 Hz for indwelling electrodes and from 152 to 260 Hz for surface electrodes. Significant differences in the mean 95% power frequencies existed among muscles monitored with surface electrodes (p = .002), but not among muscles monitored with indwelling electrodes (p = .961). No significant differences in the 95% power frequencies existed among contraction subphases for any of the muscle–electrode combinations. Maximum Nyquist rate was 893 Hz for surface electrodes and 1,764 Hz for indwelling electrodes. Our results suggest that when recording EMG of shoulder muscles, the minimum sampling frequency is 1,340 Hz for surface electrodes and 2,650 Hz for indwelling electrodes. The minimum sampling recommendations are higher than the 1,000 Hz reported in many studies involving EMG of the shoulder.  相似文献   
9.

Introduction and hypothesis

Hydrodissection incorporating different types of vasoconstrictors is commonly used in vaginal prolapse surgery. There is little evidence as to whether it adds clinical value or whether it exposes the patient to unnecessary risk. The aim of this study was to compare the effect of a vasoconstrictor compared with saline alone on operative blood loss and cardiovascular parameters in a randomised clinical trial setting.

Methods

Patients undergoing vaginal prolapse surgery were randomised to an ornipressin (Por-8, Ferring) solution or saline alone for hydrodissection. The surgeon and patient were blinded to the solution used. Operative blood loss was accurately quantified and blood pressure and pulse readings recorded Pre, intra- and postoperatively.

Results

Eighty women were randomised. There was a statistically significant difference in the median blood loss: 35 ml (1-209 ml) in the ornipressin group compared with 81 ml (2-328 ml) in the saline group, p?=?0.03. There was no statistically significant difference in the median pre and postoperative blood pressure or pulse rate between groups.

Conclusions

The use of a vasoconstrictor (ornipressin) resulted in a statistically significant decrease in operative blood loss during vaginal prolapse surgery. This occurred without any significant changes in measured cardiovascular parameters.
  相似文献   
10.

Background

Febrile urinary tract infections (fUTIs) are common after kidney transplantation (KTx); however, prospective data in a multicenter pediatric cohort are lacking. We designed a prospective registry to record data on fUTI before and after pediatric KTx.

Methods

Ninety-eight children (58 boys and 40 girls)?≤?18 years from 14 mid-European centers received a kidney transplant and completed a 2-year follow-up.

Results

Posttransplant, 38.7 % of patients had at least one fUTI compared with 21.4 % before KTx (p?=?0.002). Before KTx, fUTI was more frequent in patients with congenital anomalies of kidneys and urinary tract (CAKUT) vs. patients without (38 % vs. 12 %; p?=?0.005). After KTx, fUTI were equally frequent in both groups (48.7 % vs. 32.2 %; p?=?0.14). First fUTI posttransplant occurred earlier in boys compared with girls: median range 4 vs. 13.5 years (p?=?0.002). Graft function worsened (p?<?0.001) during fUTI, but no difference was recorded after 2 years. At least one recurrence of fUTI was encountered in 58 %.

Conclusion

This prospective study confirms a high incidence of fUTI after pediatric KTx, which is not restricted to patients with CAKUT; fUTIs have a negative impact on graft function during the infectious episode but not on 2-year graft outcome.
  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