全文获取类型
收费全文 | 404671篇 |
免费 | 26698篇 |
国内免费 | 9498篇 |
专业分类
耳鼻咽喉 | 4229篇 |
儿科学 | 11185篇 |
妇产科学 | 7376篇 |
基础医学 | 33823篇 |
口腔科学 | 8450篇 |
临床医学 | 47276篇 |
内科学 | 53472篇 |
皮肤病学 | 4898篇 |
神经病学 | 22431篇 |
特种医学 | 10555篇 |
外国民族医学 | 35篇 |
外科学 | 41306篇 |
综合类 | 62343篇 |
现状与发展 | 17篇 |
一般理论 | 29篇 |
预防医学 | 39480篇 |
眼科学 | 5932篇 |
药学 | 36555篇 |
440篇 | |
中国医学 | 35900篇 |
肿瘤学 | 15135篇 |
出版年
2023年 | 6314篇 |
2022年 | 11146篇 |
2021年 | 15630篇 |
2020年 | 14575篇 |
2019年 | 19869篇 |
2018年 | 17574篇 |
2017年 | 14676篇 |
2016年 | 12276篇 |
2015年 | 11634篇 |
2014年 | 23499篇 |
2013年 | 25403篇 |
2012年 | 21507篇 |
2011年 | 23253篇 |
2010年 | 18662篇 |
2009年 | 17113篇 |
2008年 | 16827篇 |
2007年 | 17480篇 |
2006年 | 15328篇 |
2005年 | 13477篇 |
2004年 | 11203篇 |
2003年 | 9917篇 |
2002年 | 7987篇 |
2001年 | 7310篇 |
2000年 | 6022篇 |
1999年 | 5228篇 |
1998年 | 4401篇 |
1997年 | 4328篇 |
1996年 | 3689篇 |
1995年 | 3644篇 |
1994年 | 3435篇 |
1993年 | 2694篇 |
1992年 | 2722篇 |
1991年 | 2354篇 |
1990年 | 2038篇 |
1989年 | 1831篇 |
1988年 | 1768篇 |
1987年 | 1500篇 |
1986年 | 1415篇 |
1985年 | 4298篇 |
1984年 | 5225篇 |
1983年 | 3612篇 |
1982年 | 4188篇 |
1981年 | 3829篇 |
1980年 | 3401篇 |
1979年 | 3085篇 |
1978年 | 2674篇 |
1977年 | 2034篇 |
1976年 | 2271篇 |
1975年 | 1691篇 |
1974年 | 1474篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Objectives
For individuals not on antiretroviral therapy, the risk of heterosexual transmission of HIV appears negligible when blood plasma (BP) viral loads are <1500 HIV‐1 RNA copies/mL. It is not clear whether this observation can be extrapolated to individuals on highly active antiretroviral therapy (HAART). Because of differential tissue penetration, antiretroviral drug concentrations may be sufficient to maintain an undetectable viral load in the BP yet not achieve adequate levels to suppress HIV in the genital tract. Therefore, we wanted to correlate HIV viral loads and drug concentrations in semen plasma (SP) and BP.Methods
Thirty‐three men were included. All were on combination antiretroviral therapy with an undetectable BP viral load for at least 1 year. Blood and semen samples were collected within 2 h of each other and tested for HIV RNA by the NucliSens QT (bioMerieux, St Laurent, QC, Canada) method; drug concentrations were determined by liquid chromatography tandem mass spectrometry.Results
Two of the 33 patients (6.1%) with BP viral loads below detection had time‐matched HIV viral loads in SP ≥700 copies/mL. Both patients were on efavirenz, the SP concentrations of which were ≤10% of the levels in BP and well below the minimal therapeutic drug monitoring target concentration required to suppress HIV.Conclusions
Because, at least in part, of poor drug penetration into the genital tract, an undetectable HIV viral load in the BP does not guarantee an undetectable viral load in semen. In view of this, caution should be taken in concluding that patients on HAART with suppressed viraemia are sexually non‐infectious. 相似文献102.
103.
104.
Johannes Woitzik Elke Lassel Ulf C. Schneider Helmut Schroeck Rudolf Graf 《Experimental neurology》2009,218(1):41-350
Lesion evolution during focal cerebral ischemia may depend on flow restrictions or on accumulation of toxic mediators within the infarct and expansion of these factors to the periinfarct region. So far, the precise contribution of flow dependent versus spreading-mediated impairment of viable periinfarct tissue has not been determined. Therefore, we measured lesion expansion, flow restrictions and glutamate distribution on serial brain sections at different time points after experimental focal ischemia.Permanent focal ischemia was induced by occlusion of the right middle cerebral artery in male rats and the flow reduction was subsequently measured at 1, 12 and 24 h using iodo[14C]antipyrine autoradiography. Additionally, the necrotic volume was determined on serial brain sections and the glutamate content was measured in tissue samples from adjacent microdissections.Twelve hours after focal ischemia no noteworthy viable areas with blood flow restrictions of 20-40 ml 100 g− 1 min− 1 existed but at 24 h the necrotic tissue exceeded the hemodynamically compromised region by 40 ± 21 mm3 (24%). Furthermore, at 12 and 24 h the glutamate content was elevated in areas surrounding the infarct.Relevant flow restrictions are detectable only during early stages of infarct maturation, whereas the propagation of secondary factors may be the predominant mechanism for delayed infarct evolution. 相似文献
105.
L. J. Jacobsson M. Westerberg S. Söderberg J. Lexell 《Acta neurologica Scandinavica》2009,120(6):389-395
Objectives – To assess long‐term functioning and disability after traumatic brain injury (TBI). Material and methods – Individuals (n = 88) in Norrbotten, northern Sweden, who had been transferred for neurosurgical care were assessed with internationally established TBI outcome measures 6–15 years post‐injury. Results – There was an improvement in overall outcome from discharge from inpatient rehabilitation to follow‐up. Many individuals had a high degree of motor and cognitive functioning, which enabled them to live independently in their own home without assistance, but there remained a disability related to community reintegration and social participation. This affected their productivity and to some degree their marital stability. The remaining disability and reduced productivity were related to the age at injury and the injury severity. Conclusions – Our data showed that individuals with a TBI can achieve and maintain a high degree of functioning many years after the injury. Increasing age and a greater injury severity contributed to their long‐term disability. 相似文献
106.
107.
108.
While much time has been spent deliberating about the definition of play, little emphasis has been placed on what children themselves perceive as play. The aim of the present study was to examine social context as a cue for children's perceptions of play and learning. Ninety-two children aged between four and six years (mean four years nine months) participated in the study and completed the Activity Apperception Story Procedure. Children were asked to sort photographic stimuli into those they believed depicted play/not play and learning/not learning. Each of the stimuli were identified by independent raters as containing one of the following social cues; teacher absence (solitary activity, parallel activity or cooperative activity) or teacher presence (teacher involved activity or teacher directed activity). Findings revealed that children associated teacher absence with play. More specifically, children made links between play and the presence of peers (parallel and cooperative activity). Findings are discussed in relation to play in the early years curriculum, differences in children's early educational experiences and the importance of understanding children's perceptions of play. 相似文献
109.
Central Sensitization Theory of Migraine: Clinical Implications 总被引:4,自引:2,他引:2
The clinical science of migraine headache continues to evolve. Theories of the pathophysiology of migraine have progressed from the early vascular basis of migraine to more complex current theories that emphasize the centrality of neuronal dysfunction. The most recently articulated theory of migraine is the central sensitization hypothesis, which proposes that altered processing of sensory input in the brainstem, principally the trigeminal nucleus caudalis, could account for many of the temporal and symptomatic features of migraine, as well as its poor response to triptan therapy when such treatment is initiated hours after the onset of pain. Both preclinical and clinical data support the central sensitization theory. A critical clinical implication of this theory is that drugs that are capable of either aborting or arresting the process of central sensitization, most prominently dihydroergotamine, may have a unique role in the treatment of migraine. An additional, and highly practical, implication is based upon the finding that cutaneous allodynia—pain arising from innocuous stimulation of the skin, as in hair brushing or the application of cosmetics—is an easily identifiable marker of central sensitization. Thus, the presence or absence of cutaneous allodynia can be integrated into the routine clinical assessment of migraine and utilized as a determinant of treatment. Future basic and clinical research on central sensitization is likely to be of ongoing importance to the field. 相似文献
110.
M. P. Gosselink J. J. Busschbach† C. M. Dijkhuis§ L. P. Stassen¶ W. C. Hop‡ W. R. Schouten 《Colorectal disease》2006,8(1):15-22
BACKGROUND: After total mesorectal excision for rectal cancer, many surgeons try to avoid an abdominoperineal resection (APR) by performing a transanally double stapled low colo-rectal anastomosis (LRA), frequently without a pouch. This policy is mainly based on the assumption that the quality of life after such LRA is higher than after APR. It has been suggested that a better functional outcome and therefore a higher quality of life might be achieved by a colo-anal J-pouch anastomosis (CPA). The aim of this study was to assess quality of life among disease-free survivors after APR, LRA and CPA. METHODS: The charts of 301 consecutive patients who had undergone surgery for cancer in the middle or lower third of the rectum were analysed. Two hundred four patients were eligible for inclusion. The quality of life among these patients was assessed using one generic (EQ-5D) and two disease-specific questionnaires (EORTC QLQ-C30 and EORTC QLQ-CR38). RESULTS: The response rate was 82%. The median follow-up was 31 months. Overall, quality of life was good but CPA patients had better quality of life scores than APR and LRA patients. This difference was not only due to the better functional outcome but also to the lower incidence of disturbed micturition and sexual problems in the CPA group. CONCLUSION: The quality of life after colo-anal J-pouch anastomosis is better than after abdominoperineal resection (APR) and low colo-rectal anastomosis (LRA). The quality of life after APR is similar to that after LRA. 相似文献