全文获取类型
收费全文 | 1302篇 |
免费 | 89篇 |
国内免费 | 5篇 |
专业分类
耳鼻咽喉 | 6篇 |
儿科学 | 51篇 |
妇产科学 | 3篇 |
基础医学 | 120篇 |
口腔科学 | 18篇 |
临床医学 | 120篇 |
内科学 | 143篇 |
皮肤病学 | 3篇 |
神经病学 | 278篇 |
特种医学 | 153篇 |
外科学 | 44篇 |
综合类 | 33篇 |
预防医学 | 52篇 |
眼科学 | 6篇 |
药学 | 324篇 |
肿瘤学 | 42篇 |
出版年
2023年 | 3篇 |
2022年 | 5篇 |
2021年 | 9篇 |
2020年 | 4篇 |
2019年 | 8篇 |
2018年 | 14篇 |
2017年 | 9篇 |
2016年 | 20篇 |
2015年 | 26篇 |
2014年 | 38篇 |
2013年 | 46篇 |
2012年 | 57篇 |
2011年 | 39篇 |
2010年 | 36篇 |
2009年 | 26篇 |
2008年 | 52篇 |
2007年 | 52篇 |
2006年 | 48篇 |
2005年 | 55篇 |
2004年 | 45篇 |
2003年 | 37篇 |
2002年 | 35篇 |
2001年 | 35篇 |
2000年 | 37篇 |
1999年 | 34篇 |
1998年 | 34篇 |
1997年 | 37篇 |
1996年 | 43篇 |
1995年 | 41篇 |
1994年 | 36篇 |
1993年 | 25篇 |
1992年 | 32篇 |
1991年 | 36篇 |
1990年 | 33篇 |
1989年 | 38篇 |
1988年 | 50篇 |
1987年 | 36篇 |
1986年 | 35篇 |
1985年 | 22篇 |
1984年 | 24篇 |
1983年 | 17篇 |
1982年 | 11篇 |
1981年 | 12篇 |
1980年 | 9篇 |
1979年 | 8篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1974年 | 8篇 |
1945年 | 6篇 |
排序方式: 共有1396条查询结果,搜索用时 15 毫秒
111.
O(6)-methylguanine-DNA methyltransferase activity, p53 gene status and BCNU resistance in mouse astrocytes 总被引:7,自引:0,他引:7
We observed previously that wild-type p53 rendered neonatal mouse astrocytes resistant to 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) in a gene dose-dependent fashion. This effect of p53 appeared to be unrelated to its cell cycle regulation or apoptotic functions. Because in many cell types O(6)-methylguanine-DNA methyltransferase (MGMT)-mediated DNA repair is an important mechanism of resistance to nitrosoureas, we measured MGMT activity in wild-type, heterozygous and p53 knockout neonatal mouse astrocytes. Wild-type p53 astrocytes had significantly greater MGMT activity than either heterozygous or p53 knockout astrocytes: MGMT activity was approximately 5-fold greater in wild-type p53 astrocytes than in p53 knockout cells. However, despite successful depletion of MGMT activity in wild-type astrocytes by O(6)-benzylguanine (BG), resistance to BCNU persisted unchanged. Moreover, we excluded the possibility that continued resistance to BCNU at the concentrations used could be explained by a compensatory induction of MGMT triggered by exposure to either BCNU or BG. Although these studies support a role for p53 regulation of MGMT in neonatal mouse astrocytes, BCNU resistance in wild-type cells appears to be mediated by a non-MGMT mechanism. Nevertheless, regulation of DNA repair by MGMT may be another mechanism by which alterations of the p53 gene promote tumor initiation or progression. 相似文献
112.
PC Morris JN Cawson GS Balasubramaniam 《Journal of Medical Imaging and Radiation Oncology》1999,43(1):12-15
Two cases of epidermal cyst of the breast, a rare benign condition, were detected during a 3-year period in a mammographic screening programme, from 57 954 screening examinations. It is not uncommon for epidermal cysts to be initially misdiagnosed. The mammographic, ultrasound and histological features are presented. It is recommended that these lesions be resected because they possibly have malignant potential. 相似文献
113.
The word tracheostomy derived from two greek words meaning ‘I cut the trachea’ has been known for about 3500 yrs. The process has evolved over the years and has undergone revolutionary changes in the methodology, instrumentation and indications. Although tracheostomy is now commonly used the complication rate remains high. In our series it was 48% which is comparable with other series. The purpose of this paper is to discuss the complications of tracheostomy with special attention to their management and prevention.KEY WORDS: Complications, Tracheostomy 相似文献
114.
David R Owen Qi Guo Nicola J Kalk Alessandro Colasanti Dimitra Kalogiannopoulou Rahul Dimber Yvonne L Lewis Vincenzo Libri Julien Barletta Joaquim Ramada-Magalhaes Aruloly Kamalakaran David J Nutt Jan Passchier Paul M Matthews Roger N Gunn Eugenii A Rabiner 《Journal of cerebral blood flow and metabolism》2014,34(6):989-994
Positron emission tomography (PET) targeting the 18 kDa translocator protein (TSPO) is used to quantify neuroinflammation. Translocator protein is expressed throughout the brain, and therefore a classical reference region approach cannot be used to estimate binding potential (BPND). Here, we used blockade of the TSPO radioligand [11C]PBR28 with the TSPO ligand XBD173, to determine the non-displaceable volume of distribution (VND), and hence estimate the BPND. A total of 26 healthy volunteers, 16 high-affinity binders (HABs) and 10 mixed affinity binders (MABs) underwent a [11C]PBR28 PET scan with arterial sampling. Six of the HABs received oral XBD173 (10 to 90 mg), 2 hours before a repeat scan. In XBD173-dosed subjects, VND was estimated via the occupancy plot. Values of BPND for all subjects were calculated using this VND estimate. Total volume of distribution (VT) of MABs (2.94±0.31) was lower than VT of HABs (4.33±0.29) (P<0.005). There was dose-dependent occupancy of TSPO by XBD173 (ED50=0.34±0.13 mg/kg). The occupancy plot provided a VND estimate of 1.98 (1.69, 2.26). Based on these VND estimates, BPND for HABs is approximately twice that of MABs, consistent with predictions from in vitro data. Our estimates of [11C]PBR28 VND and hence BPND in the healthy human brain are consistent with in vitro predictions. XBD173 blockade provides a practical means of estimating VND for TSPO targeting radioligands. 相似文献
115.
The ability of various benzodiazepine receptor ligands to antagonize the anticonvulsant action of ethanol was investigated using intravenous infusion of the GABA antagonist bicuculline. The partial inverse agonists FG 7142, RO 15-4513 and RO 15-3505 produced dose-related reductions in seizure threshold. These compounds also partially reversed the anticonvulsant action of ethanol. However, the magnitude of the effects in each case was only equivalent to the reduction in seizure threshold caused by each compound when administered alone. This is the proconvulsant effect of each compound merely subtracted from the anticonvulsant effect of ethanol. ZK 93426, a benzodiazepine receptor antagonist which alone failed to alter seizure threshold, did not affect the anticonvulsant action of ethanol. Both RO 15-4513 and RO 15-3505 also lowered the seizure threshold of barbiturate-treated mice, again in a subtractive fashion. The ability of RO 15-4513 and other inverse agonists to antagonize the anticonvulsant effect of ethanol appears to result from their intrinsic proconvulsant properties. 相似文献
116.
Nutt D 《Addiction (Abingdon, England)》2011,106(11):1892-3; discussion 1896-8
117.
Michaël Chopin Aaron T. Lun Yifan Zhan Jaring Schreuder Hannah Coughlan Angela D’Amico Lisa A. Mielke Francisca F. Almeida Andrew J. Kueh Ross A. Dickins Gabrielle T. Belz Shalin H. Naik Andrew M. Lew Phillipe Bouillet Marco J. Herold Gordon K. Smyth Lynn M. Corcoran Stephen L. Nutt 《Immunity》2019,50(1):77-90.e5
118.
Centrilobular emphysema: CT-pathologic correlation 总被引:5,自引:0,他引:5
Foster WL Jr; Pratt PC; Roggli VL; Godwin JD; Halvorsen RA Jr; Putman CE 《Radiology》1986,159(1):27-32
Over a 5-year period, 25 patients who had undergone chest computed tomography (CT) died and were autopsied. Their lungs were fixed in the inflated state and were assessed for the presence and severity of centrilobular emphysema (CLE). Three radiologists independently evaluated the CT scans for nonperipheral low-attenuation areas, peripheral low-attenuation areas, pulmonary vascular pruning, pulmonary vascular distortion, and pulmonary density gradient. The CT criterion that best correlated with the presence and severity of CLE was the nonperipheral low-attenuation area. With this CT criterion, lung destruction was correctly identified in 13 of 15 cases. The absence of this criterion resulted in correct identification of eight of ten normal lungs. These preliminary data suggest that CLE can be reliably identified and quantified with current CT scanners. 相似文献
119.
120.
The effects of chronic ritanserin treatment on sleep and the neuroendocrine response to l-tryptophan
A previous study has shown that acute administration of the 5-HT2 receptor antagonist ritanserin doubles Slow Wave Sleep (SWS) and increases the prolactin (PRL) response to l-tryptophan (LTP). The present study investigated the effect of repeated ritanserin treatment on sleep, neuroendocrine response to LTP and 5-HT2 platelet receptor binding. After 2 weeks, ritanserin administration SWS was persistently increased but the PRL response to LTP was unchanged. Platelet 5-HT receptor binding was undetectable at the end of ritanserin treatment but recovered 2 weeks after drug withdrawal. The results suggest that ritanserin causes a sustained effect on the 5-HT mechanisms mediating SWS and on platelet 5-HT2 receptors. However, adaptation occurs to its effect on 5-HT-mediated neuroendocrine responses. 相似文献