全文获取类型
收费全文 | 49746篇 |
免费 | 3114篇 |
国内免费 | 155篇 |
专业分类
耳鼻咽喉 | 653篇 |
儿科学 | 1423篇 |
妇产科学 | 856篇 |
基础医学 | 5897篇 |
口腔科学 | 804篇 |
临床医学 | 5052篇 |
内科学 | 10697篇 |
皮肤病学 | 860篇 |
神经病学 | 4636篇 |
特种医学 | 1997篇 |
外国民族医学 | 1篇 |
外科学 | 8710篇 |
综合类 | 474篇 |
一般理论 | 48篇 |
预防医学 | 3129篇 |
眼科学 | 807篇 |
药学 | 3044篇 |
中国医学 | 45篇 |
肿瘤学 | 3882篇 |
出版年
2023年 | 246篇 |
2022年 | 416篇 |
2021年 | 1082篇 |
2020年 | 625篇 |
2019年 | 1099篇 |
2018年 | 1305篇 |
2017年 | 952篇 |
2016年 | 990篇 |
2015年 | 1173篇 |
2014年 | 1820篇 |
2013年 | 2320篇 |
2012年 | 3742篇 |
2011年 | 3895篇 |
2010年 | 2181篇 |
2009年 | 1863篇 |
2008年 | 3406篇 |
2007年 | 3581篇 |
2006年 | 3562篇 |
2005年 | 3465篇 |
2004年 | 3333篇 |
2003年 | 3100篇 |
2002年 | 2848篇 |
2001年 | 378篇 |
2000年 | 263篇 |
1999年 | 399篇 |
1998年 | 567篇 |
1997年 | 456篇 |
1996年 | 349篇 |
1995年 | 347篇 |
1994年 | 327篇 |
1993年 | 268篇 |
1992年 | 209篇 |
1991年 | 197篇 |
1990年 | 174篇 |
1989年 | 160篇 |
1988年 | 161篇 |
1987年 | 144篇 |
1986年 | 138篇 |
1985年 | 142篇 |
1984年 | 181篇 |
1983年 | 180篇 |
1982年 | 202篇 |
1981年 | 176篇 |
1980年 | 124篇 |
1979年 | 83篇 |
1978年 | 77篇 |
1977年 | 69篇 |
1976年 | 43篇 |
1975年 | 30篇 |
1974年 | 43篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
Cognitive impairment is common in multiple sclerosis (MS), occurring at all stages of the disease, and can be a major source of vocational disability, social impairment, and impoverished quality of life. Dysfunction in free recall from long-term memory, speed of information processing, working memory, and abstract reasoning are frequently observed in MS. Despite weak correlation with disease duration and physical disability status, the degree of cognitive impairment in MS has been related to the extent of topographically specific neuronal tissue damage and loss. Additional clinical factors including disease course, fatigue, affective disturbance, and medication can impact on the degree of MS-related cognitive impairment. We suggest that the symbol digits modalities test, paced auditory serial addition task, the clock drawing test and the MS neuropsychological screening questionnaire be considered as valid and relevant screening tests for cognitive impairment in MS. 相似文献
92.
93.
Jeffrey A Morgan Ranjit John Yookyung Park Linda J Addonizio Mehmet C Oz Niloo M Edwards Jan M Quaegebeur Ralph S Mosca 《The Journal of heart and lung transplantation》2005,24(1):58-62
BACKGROUND: Many cardiac transplant programs have liberalized donor eligibility criteria in an attempt to maximize donor supply and to accommodate increasing demand. Although many studies have evaluated the potential adverse effects of prolonged donor ischemic time (DIT) in adults undergoing cardiac transplantation, relatively few have focused specifically on pediatric recipients that include a substantial number of patients and long-term follow-up. The focus of this study was to examine the effect of extended DIT on mortality after pediatric heart transplantation. METHODS: We conducted a retrospective review of our pediatric cardiac transplant experience in the past 11 years, comparing patients who received allografts and had ischemic times >240 minutes with those who had ischemic times <240 minutes. RESULTS: A total of 129 pediatric patients (<19 years) underwent orthotopic heart transplantation, of whom 78 (60.5%) had DIT <240 minutes and 51 (39.5%) had DIT >240 minutes. We found no statistically significant difference in age, sex, race, height, weight, or donor age between the groups (p = not significant). Post-transplant survival at 1, 5, and 10 years was similar for both groups: 91.2%, 88.0%, and 85.2%, respectively, for patients with DIT <240 minutes vs 89.6%, 87.2%, and 79.8%, respectively, for patients with DIT >240 minutes (p = 0.433). Additionally, using Cox proportional hazard models, extended DIT >240 minutes was not a statistically significant independent predictor of post-transplant mortality (odds ratio, 0.655; 95% confidence interval, 0.518-0.972; p = 0.684; standard error = 0.468). CONCLUSION: Procurement of hearts from distant locations with associated extended DIT is justified in the setting of increased demand and a fixed donor population. 相似文献
94.
95.
96.
Jennifer B Freeman Molly L Choate-Summers Phoebe S Moore Abbe M Garcia Jeffrey J Sapyta Henrietta L Leonard Martin E Franklin 《Neuropsychopharmacology》2007,61(3):337-343
Obsessive-compulsive disorder (OCD) is a distressing and functionally impairing disorder that can emerge as early as age 4. Cognitive behavior therapy (CBT) for OCD in youth shows great promise for amelioration of symptoms and associated functional impairment. However, the empirical evidence base for the efficacy of CBT in youth has some significant limitations, particularly as related to treating the very young child with OCD. This report includes a quantitative review of existing child CBT studies to evaluate evidence for the efficacy of CBT for OCD. It identifies gaps in the literature that, when addressed, would enhance the understanding of effective treatment in pediatric OCD. Finally, it presents a proposed research agenda for addressing the unique concerns of the young child with OCD. 相似文献
97.
98.
99.
Jonathan L. Katz Jeffrey M. Witkin Steven I. Dworkin Linda A. Dykstra Richard B. Carter 《Drug development research》1990,20(1):31-41
Effects of daily administrations of d-amphetamine were studied on key peck responses of pigeons maintained under a multiple fixed-interval 2-min, fixed-ratio 30-responseschedule. Under the fixed-interval schedule, a pause was followed by a transition to increasing rates of responding until food presentation. Under the fixed-ratio schedule, higher sustained rates of responding were maintained. Low to intermediate doses (0.3-1.0 mg/kg) of d-amphetamine changed the temporal patterns and occasionally increased rates of responding under the fixed-interval schedule. Higher doses decreased rates of responding under bothschedules. With daily injections of 1.0 mg/kg d-amphetamine prior to experimental sessions, the effects of this dose on rates and patterns of responding were attenuated, and d-anphetamine dose-effect curves were shifted to the right, primarily under the fixed-ratio schedule. Similar results were obtained with daily presession injections of 5.6 mg/kg d-amphetamine in a second group of pigeons, except that rates of responding under both schedules were decreased by this daily dose, and did not return completely to control values with repeated injections. In a third group of pigeons, 1.0 mg/kg d-amphetamine administered daily, after experimental sessions, did not alter dose-effect functions for d-amphetamine. In a second experiment, pigeons were trained to peck one response key when given 1.0 mg/kg d-amphetamine and a different key when given presession water injections. Increasing doses of d-amphetamine produced incresing percentages of d-amphetamine-key responses. Repeated administration of 5.6 mg/kg d-amphetamine shifted these dose-effect functions to the right one-half log unit. Results suggested that decreases in reinforcement frequency are not a necessary condition for the development of behavioral tolerance to d-amphetamine. 相似文献
100.
Genetically modified fibroblasts induce angiogenesis in the rat epigastric island flap 总被引:2,自引:0,他引:2
H.-G. Machens Jeffrey R. Morgan Francois Berthiaume Peter Stefanovich Ralf Reimer Alfred C. Berger 《Langenbeck's archives of surgery / Deutsche Gesellschaft fur Chirurgie》1998,383(5):345-350
Methods: Gene therapy was tested for inducing functional angiogenesis in the superficial rat epigastric island flap to allow earlier
pedicle division. Autologous rat fibroblasts were grown, harvested, cultured and retrovirally transfected to produce platelet-derived
growth factor AA (PDGF-AA), an angiogenetically active protein. Stable gene expression was monitored by PDGF-AA enzyme-linked
immunosorbent assay (ELISA). One hundred and eighty animals were divided into three groups (I–III) and a bilateral flap created
in each animal. In all experiments, the right-sided flap was subjected to experimental treatment and the left-sided flap served
as control (1 ml saline 0.9%). During flap elevation, group I received 5×106 GMFB (genetically modified fibroblasts) plus 1 ml Dul-becco's modified Eagle's medium. Group II was treated with 5×106 NMFB (non-modified fibroblasts) plus 1 ml medium and group III received 1 ml medium only. The flaps were sutured back and
the vascular pedicle was bilaterally ligated and divided in each of ten animals during the following 6 days. After 7 days,
the flaps were harvested, the amount of necrosis measured and histologically examined. Results: The GMFB produced up to 560 times more PDGF-AA than the NMFB, measured by ELISA. The GMFB-treated flaps tolerated surgical
division of the vascular pedicle significantly earlier than groups II and III. Histologically, fibroblasts persisted in all
flaps of groups I and II, without major inflammatory reaction. In all GMFB-treated flaps, massive angiogenesis could be demonstrated.
Conclusion: By means of retroviral gene transfer, autologous rat fibroblasts can be genetically modified for stable expression of the
PDGF-A gene to produce high amounts of PDGF-AA, which is angiogenetically active. After injection into the panniculus carnosus,
these cells induce functional angiogenesis to permit earlier division of the vascular pedicle in this flap model.
Received: 5 January 1998 / Accepted: 17 June 1998 相似文献