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   236664篇
  免费   15509篇
  国内免费   989篇
耳鼻咽喉   2565篇
儿科学   6047篇
妇产科学   4444篇
基础医学   29626篇
口腔科学   4336篇
临床医学   24227篇
内科学   49787篇
皮肤病学   3253篇
神经病学   23774篇
特种医学   10165篇
外国民族医学   13篇
外科学   37316篇
综合类   2564篇
现状与发展   1篇
一般理论   183篇
预防医学   16777篇
眼科学   5660篇
药学   15621篇
  1篇
中国医学   320篇
肿瘤学   16482篇
  2023年   1228篇
  2022年   1892篇
  2021年   5359篇
  2020年   3059篇
  2019年   5081篇
  2018年   6082篇
  2017年   4460篇
  2016年   4868篇
  2015年   5773篇
  2014年   8400篇
  2013年   11356篇
  2012年   17407篇
  2011年   18123篇
  2010年   10138篇
  2009年   9373篇
  2008年   15972篇
  2007年   16801篇
  2006年   16320篇
  2005年   16194篇
  2004年   15230篇
  2003年   13941篇
  2002年   13303篇
  2001年   1982篇
  2000年   1455篇
  1999年   2050篇
  1998年   2811篇
  1997年   2244篇
  1996年   1949篇
  1995年   1781篇
  1994年   1542篇
  1993年   1509篇
  1992年   1015篇
  1991年   955篇
  1990年   817篇
  1989年   774篇
  1988年   703篇
  1987年   642篇
  1986年   657篇
  1985年   696篇
  1984年   934篇
  1983年   814篇
  1982年   1057篇
  1981年   982篇
  1980年   864篇
  1979年   482篇
  1978年   530篇
  1977年   458篇
  1976年   438篇
  1975年   331篇
  1974年   333篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
191.
Transcranial Doppler (TCD) is an accepted modality for the evaluation of cerebral blood flow velocities. OBJECTIVES: The purpose of this study was to test the feasibility of bedside TCD measurement in the emergency department (ED) with critically ill, intubated patients. METHODS: A prospective convenience sample of patients presenting to a university hospital over a two-month period underwent TCD evaluation of the middle cerebral artery. Intubated patients with head trauma and any patient requiring tracheal intubation were eligible. A 2-MHz Doppler probe was positioned over the temporal bone to acquire blood flow velocities. An emergency medicine resident and research assistant obtained measurements. Continuous TCD tracings were recorded on a video cassette recorder tape for quality assurance review and data collection. Vital signs and therapeutic interventions were also recorded. Flow velocities were measured in cm/s; the peak Resistance Index (RI) was calculated for each patient. RESULTS: A total of 30 patients were enrolled in the study. Adequate tracings were obtained in 25 patients (83%) without a disruption of resuscitation. Tracings could not be obtained in five patients; they were listed as TCD failures. However, in two of these patients, adequate flow velocity tracings were obtained after resuscitation. Four patients were evaluated during tracheal intubation. One patient was monitored successfully during cardiopulmonary resuscitation. The median time required for data acquisition was 1.9 minutes. The mean highest RI for those who expired was 0.84. For those who survived, the mean highest RI was 0.52. The difference of 0.32 was statistically significant (p = 0.04). CONCLUSIONS: Noninvasive blood flow velocity monitoring of the middle cerebral artery using TCD is feasible in the ED when performed at the bedside on intubated patients with traumatic brain injury and others during tracheal intubation and resuscitation.  相似文献   
192.
This study was designed to describe the course of epilepsy (in terms of seizure frequency) and to assess the variables (antiepileptic therapy regimens and others) correlated to improvement. Seizure frequency (categories: seizure free, more than one seizure/year, monthly seizures, weekly seizures and daily seizures) and antiepileptic medication were retrospectively compared between 1992 and 2002 in a large cohort of 550 inpatients with chronic epilepsy and different degrees of intellectual disability or multiple handicaps. RESULTS: Seizure frequency decreased significantly (p<0.001). 218 of the 394 patients (55.3%) not seizure free in 1992 improved (changed into a better frequency category). The improvement rate was marginally higher in patients who had undergone a medication change (p=0.08). A high seizure frequency in 1992 (p=0.016) and older age (p=0.006), but not epilepsy syndrome or degree of intellectual disability, were predictors for improvement (stepwise logistic regression analysis). 56.4% of the improved patients were on combinations of two AEDs (17.4%, monotherapy; 20.2%, triple therapy). The most frequent therapy regimens in the improved patients were lamotrigine/valproate (48 patients), carbamazepine/phenobarbital (21) and carbamazepine only (19). Lamotrigine/valproate was effective in all kinds of epileptic syndromes. Most patients on lamotrigine had serum concentrations above 10microg/ml, approximately one half had dosages above 200mg/day. The rate of seizure freedom increased from 28.4 to 37.6%. The 84% of the patients seizure free in 1992 remained seizure free. Predictors for seizure freedom in 2002 were higher age (stepwise logistic regression, p<0.0005) and seizure freedom in 1992 (p<0.0005). CONCLUSIONS: Substantial improvement can be achieved even in intellectually disabled patients with chronic epilepsy. Although the rate of seizure freedom is reduced in comparison with a non-ID population, once seizure freedom has been achieved it is most likely to continue. For a majority of this patient population, monotherapy may not be sufficient. Lamotrigine/valproate appears to be a major therapeutic innovation.  相似文献   
193.
The Sixth Epilepsy Research Foundation workshop, held in Oxford in March 2006, brought together basic scientists, geneticists, epidemiologists, statisticians, pharmacologists and clinicians to consider progress, issues and strategies for harnessing genetics to improve the understanding and treatment of the epilepsies. General principles were considered, including the fundamental importance of clear study design, adequate patient numbers, defi ned phenotypes, robust statistical data handling, and follow-up of genetic discoveries. Topics where some progress had been made were considered including chromosomal abnormalities, neurodevelopment, hippocampal sclerosis, juvenile myoclonic epilepsy, focal cortical dysplasia and pharmacogenetics. The ethical aspects of epilepsy genetics were reviewed. Principles and limitations of collaboration were discussed. Presentations and their matched discussions are produced here. There was optimism that further genetic research in epilepsy was not only feasible, but might lead to improvements in the lives of people with epilepsy.  相似文献   
194.
Percutaneous intervention in saphenous vein grafts (SVG) carries a higher risk of distal embolization than intervention in a native vessel, and use of a distal protection device has been shown to improve the outcomes in SVG interventions. We describe an intervention done in an unexpected 'Y' SVG which required dual distal protection with Filterwires placed in both limbs of the diseased graft and which was performed via a 6 Fr guide catheter.  相似文献   
195.
196.
18F-FCWAY (18F-trans-4-fluoro-N-(2-[4-(2-methoxyphenyl) piperazin-1-yl)ethyl]-N-(2-pyridyl)cyclohexanecarboxamide) is useful in clinical research with PET for measuring serotonin 1A (5-HT1A) receptor densities in brain regions of human subjects but has significant bone uptake of radioactivity due to defluorination. The uptake of radioactivity in skull compromises the accuracy of measurements of 5-HT1A receptor densities in adjacent areas of brain because of spillover of radioactivity through the partial-volume effect. Our aim was to demonstrate with a rat model that defluorination of 18F-FCWAY may be inhibited in vivo to improve its applicability to measuring brain regional 5-HT1A receptor densities. METHODS: PET of rat head after administration of 18F-FCWAY was used to confirm that the distribution of radioactivity measured in brain is dominated by binding to 5-HT1A receptors and to reveal the extent of defluorination of 18F-FCWAY in vivo as represented by radioactivity (18F-fluoride ion) uptake in skull. Cimetidine, diclofenac, and miconazole, known inhibitors of CYP450 2EI, were tested for the ability to inhibit defluorination of 18F-FCWAY in rat liver microsomes in vitro. The effects of miconazole treatment of rats on skull radioactivity uptake and, in turn, its spillover on brain 5-HT1A receptor imaging were assessed by PET with venous blood analysis. RESULTS: PET confirmed the potential of 18F-FCWAY to act as a radioligand for 5-HT1A receptors in rat brain and also revealed extensive defluorination. In rat liver microsomes in vitro, defluorination of 18F-FCWAY was almost completely inhibited by miconazole and, to a less extent, by diclofenac. In PET experiments, treatment of rats with miconazole nitrate (60 mg/kg intravenously) over the 45-min period before administration of 18F-FCWAY almost obliterated defluorination and bone uptake of radioactivity. Also, brain radioactivity almost doubled while the ratio of radioactivity in receptor-rich ventral hippocampus to that in receptor-poor cerebellum almost tripled to 14. The plasma half-life of radioligand was also extended by miconazole treatment. CONCLUSION: Miconazole treatment, by eliminating defluorination of 18F-FCWAY, results in effective imaging of brain 5-HT1A receptors in rat. 18F-FCWAY PET in miconazole-treated rats can serve as an effective platform for investigating 5-HT1A receptors in rodent models of neuropsychiatric conditions or drug action.  相似文献   
197.
198.
199.
200.
Molecular determinants of cetuximab efficacy.   总被引:17,自引:0,他引:17  
PURPOSE: To investigate whether mRNA expression levels of cyclin D1 (CCND1), cyclooxygenase 2 (Cox-2), epidermal growth factor receptor (EGFR), interleukin 8 (IL-8), and vascular endothelial growth factor (VEGF), all members of the EGFR signaling pathway, are associated with clinical outcome in patients with EGFR-expressing metastatic colorectal cancer (CRC) treated with cetuximab. PATIENTS AND METHODS: Thirty-nine patients with metastatic CRC, refractory to both irinotecan and oxaliplatin, were enrolled on IMCL-0144 and treated with single-agent cetuximab. The intratumoral mRNA levels of CCND1, Cox-2, EGFR, IL-8, and VEGF were assessed from paraffin-embedded tissue samples using laser-capture microdissection and quantitative real-time polymerase chain reaction. RESULTS: There were 21 women and 18 men with a median age of 64 years (range, 35 to 83 years). Higher gene expression levels of VEGF were associated with resistance to cetuximab (P = .038; Kruskal-Wallis test). The combination of low gene expression levels of Cox-2, EGFR, and IL-8 was significantly associated with overall survival (13.5 v 2.3 months; P = .028; log-rank test). Both findings were independent of skin toxicity that was itself significantly correlated to survival. Patients with a lower mRNA amount of EGFR had a longer overall survival compared with patients that had a higher mRNA amount (7.3 v 2.2 months; P = .09; log-rank test). Patients with lower expression of Cox-2 had a significantly higher rate of grade 2 to 3 skin reactions under cetuximab treatment. CONCLUSION: This pilot study suggests that gene expression levels of Cox-2, EGFR, IL-8, and VEGF in patients with metastatic CRC may be useful markers of clinical outcome in single-agent cetuximab treatment.  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