全文获取类型
收费全文 | 2587522篇 |
免费 | 185004篇 |
国内免费 | 7569篇 |
学科分类
医药卫生 | 2780095篇 |
出版年
2021年 | 19982篇 |
2019年 | 20621篇 |
2018年 | 29290篇 |
2017年 | 22595篇 |
2016年 | 26231篇 |
2015年 | 29504篇 |
2014年 | 40444篇 |
2013年 | 60424篇 |
2012年 | 80226篇 |
2011年 | 84496篇 |
2010年 | 51007篇 |
2009年 | 49146篇 |
2008年 | 79027篇 |
2007年 | 83841篇 |
2006年 | 85566篇 |
2005年 | 81735篇 |
2004年 | 78729篇 |
2003年 | 76043篇 |
2002年 | 73332篇 |
2001年 | 128413篇 |
2000年 | 131330篇 |
1999年 | 110502篇 |
1998年 | 31255篇 |
1997年 | 27919篇 |
1996年 | 28219篇 |
1995年 | 27386篇 |
1994年 | 25068篇 |
1993年 | 23419篇 |
1992年 | 85161篇 |
1991年 | 81567篇 |
1990年 | 78785篇 |
1989年 | 76061篇 |
1988年 | 69470篇 |
1987年 | 67998篇 |
1986年 | 63545篇 |
1985年 | 60513篇 |
1984年 | 44943篇 |
1983年 | 37944篇 |
1982年 | 22456篇 |
1981年 | 19984篇 |
1979年 | 38959篇 |
1978年 | 27439篇 |
1977年 | 23256篇 |
1976年 | 21495篇 |
1975年 | 22818篇 |
1974年 | 26788篇 |
1973年 | 25373篇 |
1972年 | 23749篇 |
1971年 | 21955篇 |
1970年 | 20185篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
104.
N. V. Bashmakova G. N. Chistiakova I. A. Gazieva Y. M. Trapeznikova D. O. Mazurov 《Gynecological endocrinology》2015,31(10):31-33
AbstractThis study was undertaken to compare the concentrations of pro- and anti-angiogenic growth factors, nitric oxide (NO) stable metabolites in maternal serum and embryonic left ventricular (LV) isovolumic relaxation time (IRT, ms) during the first trimester in two groups of women: with pregnancy conceived by assisted reproductive technologies (ART, n?=?39) and normally conceived (control group, n?=?68) pregnancy. The concentration of vasoconstrictor endothelin 1 was 45.5 times more in ART than in control group. On the contrary, the concentrations of NO stable metabolites in ART were 1.9 times less than in control women. The assessment of angiogenic suppressors in ART women demonstrates the decrease in s-endoglin concentration was 1.6 times and in soluble receptor to vascular endothelial growth factor concentration was 2.0 times in comparison with control group. There was a significant increase in LV IRT in ART embryos in comparison to control ones. These data suggest significant changes in pro- anti-angiogenic factors balance and increase in vascular impedance in ART-conceived embryos. 相似文献
105.
106.
107.
Arjenne H.M. Gussenhoven Amika S. Singh S. Theo Goverts Marten van Til Johannes R. Anema Sophia E. Kramer 《International journal of audiology》2015,54(8):507-517
Objective: A multidisciplinary vocational rehabilitation programme, the Vocational Enablement Protocol (VEP) was developed to address the specific needs of employees with hearing difficulties. In the current study we evaluated the process of implementing the VEP in audiologic care among employees with hearing impairment. Design: In conjunction with a randomized controlled trial, we collected and analysed data on seven process parameters: recruitment, reach, fidelity, dose delivered, dose received and implemented, satisfaction, and perceived benefit. Study sample: Sixty-six employees with hearing impairment participated in the VEP. The multidisciplinary team providing the VEP comprised six professionals. Results: The professionals performed the VEP according to the protocol. Of the recommendations delivered by the professionals, 31% were perceived as implemented by the employees. Compliance rate was highest for hearing-aid uptake (51%). Both employees and professionals were highly satisfied with the VEP. Participants rated good perceived benefit from it. Conclusions: Our results indicate that the VEP could be a useful treatment for employees with hearing difficulties from a process evaluation perspective. Implementation research in the audiological setting should be encouraged in order to further provide insight into parameters facilitating or hindering successful implementation of an intervention and to improve its quality and efficacy. 相似文献
108.
Carlos A. ávila-Orta Zoe V. Qui?ones-Jurado Miguel A. Waldo-Mendoza Erika A. Rivera-Paz Víctor J. Cruz-Delgado José M. Mata-Padilla Pablo González-Morones Ronald F. Ziolo 《Materials》2015,8(11):7900-7912
Isotactic polypropylenes (iPP) with different melt flow indexes (MFI) were used to fabricate nanocomposites (NCs) with 10 wt % loadings of multi-wall carbon nanotubes (MWCNTs) using ultrasound-assisted extrusion methods to determine their effect on the morphology, melt flow, and electrical properties of the NCs. Three different types of iPPs were used with MFIs of 2.5, 34 and 1200 g/10 min. Four different NC fabrication methods based on melt extrusion were used. In the first method melt extrusion fabrication without ultrasound assistance was used. In the second and third methods, an ultrasound probe attached to a hot chamber located at the exit of the die was used to subject the sample to fixed frequency and variable frequency, respectively. The fourth method is similar to the first method, with the difference being that the carbon nanotubes were treated in a fluidized air-bed with an ultrasound probe before being used in the fabrication of the NCs with no ultrasound assistance during extrusion. The samples were characterized by MFI, Optical microscopy (OM), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), electrical surface resistivity, and electric charge. MFI decreases in all cases with addition of MWCNTs with the largest decrease observed for samples with the highest MFI. The surface resistivity, which ranged from 1013 to 105 Ω/sq, and electric charge, were observed to depend on the ultrasound-assisted fabrication method as well as on the melt flow index of the iPP. A relationship between agglomerate size and area ratio with electric charge was found. Several trends in the overall data were identified and are discussed in terms of MFI and the different fabrication methods. 相似文献
109.
Kimberly M. Avallone 《The Journal of asthma》2015,52(5):498-504
Objective: Despite its negative effects, smoking is more common among individuals with asthma compared to those without. Anxiety sensitivity (fear of arousal-related sensations) is associated with both smoking and asthma; however, no research, to date, has examined the interplay between these three factors. Thus, the purpose of the current study was to evaluate the mediating role of anxiety sensitivity in the association between asthma diagnosis and smoking status. Methods: The current study was a secondary analysis of data from three existing datasets of non-smokers and smokers with and without asthma (n?=?433; 56.3% female, Mage?=?34.01 years, SD?=?13.9). Participants provided information on their asthma diagnosis status and smoking status and completed self-report measures. Results: As hypothesized, after controlling for gender, race and age, there was a significant indirect effect of asthma diagnosis on smoking status through anxiety sensitivity (95% CI?=?0.07–0.48). Conclusions: These results indicate that the association between asthma diagnosis and smoking status appears to be driven, in part, by anxiety sensitivity and suggest that anxiety sensitivity may serve as an important target for prevention and intervention efforts for smokers with asthma. 相似文献
110.
K.-C. Sung D.-C. Seo S.-J. Lee M.-Y. Lee S.H. Wild C.D. Byrne 《Nutrition, metabolism, and cardiovascular diseases : NMCD》2019,29(5):489-495