全文获取类型
收费全文 | 584篇 |
免费 | 28篇 |
国内免费 | 5篇 |
专业分类
耳鼻咽喉 | 8篇 |
儿科学 | 33篇 |
妇产科学 | 7篇 |
基础医学 | 67篇 |
口腔科学 | 16篇 |
临床医学 | 83篇 |
内科学 | 118篇 |
皮肤病学 | 32篇 |
神经病学 | 25篇 |
特种医学 | 123篇 |
外科学 | 18篇 |
综合类 | 22篇 |
预防医学 | 23篇 |
眼科学 | 4篇 |
药学 | 14篇 |
1篇 | |
肿瘤学 | 23篇 |
出版年
2023年 | 1篇 |
2022年 | 3篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 5篇 |
2018年 | 10篇 |
2017年 | 4篇 |
2016年 | 8篇 |
2015年 | 11篇 |
2014年 | 12篇 |
2013年 | 15篇 |
2012年 | 8篇 |
2011年 | 13篇 |
2010年 | 29篇 |
2009年 | 28篇 |
2008年 | 12篇 |
2007年 | 26篇 |
2006年 | 17篇 |
2005年 | 16篇 |
2004年 | 9篇 |
2003年 | 4篇 |
2002年 | 9篇 |
2001年 | 8篇 |
2000年 | 4篇 |
1999年 | 7篇 |
1998年 | 38篇 |
1997年 | 45篇 |
1996年 | 38篇 |
1995年 | 19篇 |
1994年 | 29篇 |
1993年 | 22篇 |
1992年 | 9篇 |
1991年 | 9篇 |
1990年 | 11篇 |
1989年 | 22篇 |
1988年 | 20篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 14篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1981年 | 11篇 |
1980年 | 7篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1969年 | 1篇 |
排序方式: 共有617条查询结果,搜索用时 15 毫秒
51.
Let''s look at human immunodeficiency virus look-back before leaping into hepatitis C virus look-back 总被引:1,自引:0,他引:1
MP Busch 《Transfusion》1991,31(7):655-661
52.
M P Kilgard P K Pandya J L Vazquez D L Rathbun N D Engineer R Moucha 《Audiology & neuro-otology》2001,6(4):196-202
Cortical responses are adjusted and optimized throughout life to meet changing behavioral demands and to compensate for peripheral damage. The cholinergic nucleus basalis (NB) gates cortical plasticity and focuses learning on behaviorally meaningful stimuli. By systematically varying the acoustic parameters of the sound paired with NB activation, we have previously shown that tone frequency and amplitude modulation rate alter the topography and selectivity of frequency tuning in primary auditory cortex. This result suggests that network-level rules operate in the cortex to guide reorganization based on specific features of the sensory input associated with NB activity. This report summarizes recent evidence that temporal response properties of cortical neurons are influenced by the spectral characteristics of sounds associated with cholinergic modulation. For example, repeated pairing of a spectrally complex (ripple) stimulus decreased the minimum response latency for the ripple, but lengthened the minimum latency for tones. Pairing a rapid train of tones with NB activation only increased the maximum following rate of cortical neurons when the carrier frequency of each train was randomly varied. These results suggest that spectral and temporal parameters of acoustic experiences interact to shape spectrotemporal selectivity in the cortex. Additional experiments with more complex stimuli are needed to clarify how the cortex learns natural sounds such as speech. 相似文献
53.
Rubin JI; Arger PH; Pollack HM; Banner MP; Coleman BG; Mintz MC; VanArsdalen KN 《Radiology》1987,162(1):21
54.
JJ Korelitz ; AE Williams ; MP Busch ; TF Zuck ; HE Ownby ; LJ Matijas ; DJ Wright 《Transfusion》1994,34(10):870-876
BACKGROUND: Most blood centers utilize a confidential unit exclusion (CUE) process, intended to reduce the risk of transfusion-associated infectious diseases by allowing high-risk donors confidentially to exclude their blood from use for transfusion. The effectiveness of this method remains controversial. STUDY DESIGN AND METHODS: Confirmatory or supplemental test results for antibodies to human immunodeficiency virus, human T-lymphotropic virus type I, and hepatitis C virus, as well as hepatitis B surface antigen and syphilis and screening test results for antibodies to hepatitis B core (antigen) and alanine aminotransferase levels were obtained for approximately 1.8 million units donated during 1991 and 1992 at five blood centers within the United States. The prevalences of these infectious disease markers in units that the donors confidentially excluded (CUE+) and units that the donors did not exclude (CUE-) were calculated and examined within demographic subgroups. RESULTS: Units that were CUE+ were 8 to 41 times more likely to be seropositive for antibodies to human immunodeficiency virus and hepatitis C virus, hepatitis B surface antigen, and syphilis and three to four times more likely to react for antibody to hepatitis B core (antigen) or to have elevated alanine aminotransferase levels than units that were CUE- (p < 0.001). The positive predictive value of CUE (the percentage of CUE+ units that were confirmed seropositive for any marker) was 3.5 percent, and the sensitivity of CUE (the percentage of confirmed-seropositive units that were CUE+) was 2.3 percent. CONCLUSION: The current CUE process has low sensitivity and apparently low positive predictive value, and in many cases, it appeared that donors misunderstood it. Yet, CUE was not a “random process,” as CUE+ units were more likely to be seropositive for any infectious disease marker than CUE- units. This suggests that efforts to improve the CUE system may be warranted. As risk factors for transfusion-transmitted infection become more difficult to identify by history-based screening, however, such efforts may have limited effect. 相似文献
55.
The Viral Activation Transfusion Study (VATS): rationale, objectives, and design overview 总被引:1,自引:0,他引:1
56.
Maat M Buysse CM Emonts M Spanjaard L Joosten KF de Groot R Hazelzet JA 《Critical care (London, England)》2007,11(5):R112
Background
To gain insight into factors that might affect results of future case-control studies, we performed an analysis of children with sepsis and purpura admitted to the paediatric intensive care unit (PICU) of Erasmus MC-Sophia Children's Hospital (Rotterdam, The Netherlands). 相似文献57.
BACKGROUND: Concern over the theoretical possibility of disease transmission via blood from donors who develop Creutzfeldt-Jakob disease has led to proposals to exclude older individuals from donating plasma for further manufacture into pooled plasma donations. The impact of extending this age-deferral policy to blood donors was examined with respect to the risk for known transmissible viruses. STUDY DESIGN AND METHODS: Demographic characteristics and confirmed prevalence rates (/10(5) first-time donations) and incidence rates (/10(5) person-years for repeat donors) for viral markers were compared for donors < 50 years old (n = 1,259,805 [85%]) and > or = 50 years old (n = 219,856 [15%]) and for donors < 60 years old (n = 1,409,176 [95%]) and > or = 60 years old (n = 70,485 [5%]). Incidence rates were combined with infectious window-period estimates for each virus, to calculate the risk of virus transmission per 10(6) donations. RESULTS: Unadjusted prevalence rates were significantly greater for younger than for older donor groups for human immunodeficiency virus (HIV), hepatitis B surface antigen (HBsAg), and hepatitis C virus (HCV) (p < or = 0.05). Incidence rates (and transmission risk estimates) for HBsAg were significantly higher in the < 50 donor group than in the > or = 50 group (p < or = 0.05), and those for HIV, human T-lymphotropic virus, and HCV were not significantly higher (p > 0.05). Blanket removal of donors over the age of 50 would potentially lead to the following significant increases in the risk of infected units: HIV, 12 percent; HCV, 21 percent; and hepatitis B virus (HBsAg), 22 percent. CONCLUSION: Removal of donors over the age of 60 would not significantly affect the risk of infected units. Deferral of donors > or = 50 years of age from whole-blood donations for unfounded concerns about Creutzfeldt-Jakob disease could have adverse effects on both blood availability and safety. 相似文献
58.
To determine the incidence of transfusion-associated human immunodeficiency virus (HIV) infection after routine screening of donated blood, a pilot study estimated the pretransfusion prevalence of HIV infection among blood product recipients in San Francisco. Among the 911 nonduplicate pretransfusion specimens from recipients without a clinical history of acquired immune deficiency syndrome (AIDS) or AIDS-related complex (ARC), the overall prevalence of antibody to HIV was 2.9 percent (5.2% among males and 0.6% among females; p = 0.00002). If recipients in specifically defined or possible high-risk groups (n = 348) were excluded, a seropositivity rate of 1.8 percent (10/563) was detected, with all the positives occurring in men (10/242, 4.1%) and none in women (0/321, 0%). This demonstrated prevalence of HIV infection among blood product recipients in San Francisco before transfusion was substantially higher than the known 0.02 to 0.04 percent prevalence in the donor population. Therefore, the population of women without known risk for AIDS is the best in which to assess the risk of HIV infection in patients who are currently receiving seronegative blood transfusions. 相似文献
59.
Sudhakar Selvaraj Osamu Abe Francesco Amico Yuqi Cheng Sean J. Colloby John T. O'Brien Thomas Frodl Ian H. Gotlib Byung-Joo Ham M Justin Kim P Cédric MP Koolschijn Cintia A.‐M. Périco Giacomo Salvadore Alan J. Thomas Marie‐José Van Tol Nic J.A. van der Wee Dick J. Veltman Gerd Wagner Andrew M. McIntosh 《Human brain mapping》2016,37(4):1393-1404
60.
The inactivation of HIV by gamma-radiation was studied in frozen and liquid plasma; a reduction of the virus titer of 5 to 6 logs was achieved at doses of 5 to 10 Mrad at -80 degrees C and 2.5 Mrad at 15 degrees C. The effect of irradiation on the biologic activity of a number of coagulation factors in plasma and in lyophilized concentrates of factor VIII (FVIII) and prothrombin complex was examined. A recovery of 85 percent of the biologic activity of therapeutic components present in frozen plasma and in lyophilized coagulation factor concentrates was reached at radiation doses as low as 1.5 and 0.5 Mrad, respectively. As derived from the first-order radiation inactivation curves, the radiosensitive target size of HIV was estimated to be 1 to 3 MDa; the target size of FVIII was estimated to be 130 to 160 kDa. Gamma radiation must be disregarded as a method for the sterilization of plasma and plasma-derived products, because of the low reduction of virus infectivity at radiation doses that still give acceptable recovery of biologic activity of plasma components. 相似文献