全文获取类型
收费全文 | 743篇 |
免费 | 24篇 |
国内免费 | 3篇 |
专业分类
耳鼻咽喉 | 2篇 |
儿科学 | 38篇 |
妇产科学 | 10篇 |
基础医学 | 57篇 |
口腔科学 | 15篇 |
临床医学 | 77篇 |
内科学 | 159篇 |
皮肤病学 | 10篇 |
神经病学 | 12篇 |
特种医学 | 248篇 |
外科学 | 31篇 |
综合类 | 19篇 |
预防医学 | 24篇 |
眼科学 | 4篇 |
药学 | 33篇 |
1篇 | |
中国医学 | 8篇 |
肿瘤学 | 22篇 |
出版年
2021年 | 3篇 |
2020年 | 2篇 |
2018年 | 2篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 9篇 |
2014年 | 5篇 |
2013年 | 9篇 |
2012年 | 7篇 |
2011年 | 20篇 |
2010年 | 24篇 |
2009年 | 23篇 |
2008年 | 11篇 |
2007年 | 10篇 |
2006年 | 16篇 |
2005年 | 13篇 |
2004年 | 2篇 |
2003年 | 7篇 |
2002年 | 7篇 |
2001年 | 6篇 |
2000年 | 6篇 |
1999年 | 9篇 |
1998年 | 37篇 |
1997年 | 34篇 |
1996年 | 38篇 |
1995年 | 47篇 |
1994年 | 37篇 |
1993年 | 38篇 |
1992年 | 8篇 |
1991年 | 3篇 |
1990年 | 11篇 |
1989年 | 37篇 |
1988年 | 23篇 |
1987年 | 29篇 |
1986年 | 37篇 |
1985年 | 21篇 |
1984年 | 17篇 |
1983年 | 14篇 |
1982年 | 15篇 |
1981年 | 19篇 |
1980年 | 18篇 |
1979年 | 9篇 |
1978年 | 15篇 |
1977年 | 15篇 |
1976年 | 13篇 |
1975年 | 12篇 |
1959年 | 2篇 |
1958年 | 4篇 |
1957年 | 6篇 |
1954年 | 2篇 |
排序方式: 共有770条查询结果,搜索用时 343 毫秒
741.
Pulmonary abnormalities and PET data analysis: a retrospective study 总被引:13,自引:0,他引:13
Lowe VJ; Duhaylongsod FG; Patz EF; Delong DM; Hoffman JM; Wolfe WG; Coleman RE 《Radiology》1997,202(2):435
742.
Gamma camera radionuclide images: improved contrast with energy- weighted acquisition 总被引:4,自引:0,他引:4
An energy-weighted acquisition (EWA) technique has been developed that utilizes all scintillation events, weighting their contributions depending on their energy, to formulate a radionuclide image. Photopeak events from primary radiation contribute positively; scatter events contribute negatively, providing for scatter subtraction and improved image contrast. EWA is employed with an on-line weighted-acquisition module (WAM) as the data are acquired, rather than as a postprocessing technique. EWA was compared with normal window imaging in patients and in phantoms. For gallium-67 and thallium-201, contrast improved by as much as 40%. A much smaller improvement in contrast was observed with technetium-99m due to its ideal monoenergetic emissions. Single photon emission computed tomographic studies also showed improved contrast and were without artifact. EWA has great promise, and with further development quantitative scatter correction may be possible. 相似文献
743.
In the present study we investigate the nature of the murine bone marrow cell subset responsible for the marked increase in histamine synthesis induced by interleukin-3 (IL-3). Because mast cells, and eventually their committed precursors, represent a potential source of histamine in this context, we examined their possible participation in this biologic activity with particular attention. We provide evidence that neither of these populations respond to IL-3 in terms of histamine synthesis and that other differentiated end cells or stromal components of the bone marrow are also not involved in this phenomenon. Starting from these findings, we further characterized the immature hematopoietic compartment responsible for IL-3-induced histamine synthesis using fluorescence-activated cell sorter (FACS) sorting based on rhodamine retention or wheat germ agglutinin (WGA) affinity. These procedures have allowed us to ascribe the following features to histamine-producing cells: (1) They belong to a low-density, progenitor- enriched bone marrow subset containing cells of relatively important size and internal structure. (2) The highest histamine levels are generated by the rhodamine-bright fraction of this population, while the most primitive rhodamine-dull cells do not express this biologic activity. (3) Histamine-producing cells do not copurify with colony- forming units in spleen day 7 and day 12 in WGA-bright fractions. (4) Their enrichment is associated with increased frequencies of cells forming colonies in methylcellulose (CFU-C), suggesting the involvement of several progenitors with partially limited differentiation potential in this biologic activity. 相似文献
744.
745.
A linear attenuation coefficient for water (mu = .15 cm-1) at 140 keV has been used in the determination of left ventricular volumes (LVV) by attenuation-corrected equilibrium methods. This theoretical value ignores the effect of Compton scatter and thus may be too high for human LVV determinations. The effective attenuation coefficient, mu', of the human chest was determined in ten normal volunteers using a Tc-99m esophageal source imaged with a gamma camera. Values for mu' at 30 degrees LAO in end-expiration, quiet breathing, and end-inspiration were .125 +/- .006 cm-1, .125 +/- .005 cm-1, and .113 +/- .007 cm-1, respectively (95% confidence interval). Values of mu' at 45 degrees LAO were .122 +/- .006 cm-1, .119 +/- .007 cm-1, and .099 +/- .009 cm-1, respectively, for the same conditions. The measured value of mu' for the source in a water phantom was .127 +/- .001 cm-1. This suggests that a value of mu' of .125 cm-1 may be appropriate for use in determining LVV in patients. 相似文献
746.
747.
Mapping cerebral blood flow by xenon-enhanced computed tomography: clinical experience 总被引:2,自引:0,他引:2
Yonas H; Good WF; Gur D; Wolfson SK Jr; Latchaw RE; Good BC; Leanza R; Miller SL 《Radiology》1984,152(2):435
748.
749.
750.