全文获取类型
收费全文 | 436篇 |
免费 | 32篇 |
国内免费 | 13篇 |
专业分类
耳鼻咽喉 | 1篇 |
儿科学 | 22篇 |
妇产科学 | 2篇 |
基础医学 | 20篇 |
口腔科学 | 14篇 |
临床医学 | 59篇 |
内科学 | 79篇 |
皮肤病学 | 4篇 |
神经病学 | 6篇 |
特种医学 | 178篇 |
外科学 | 11篇 |
综合类 | 40篇 |
预防医学 | 6篇 |
眼科学 | 5篇 |
药学 | 9篇 |
1篇 | |
肿瘤学 | 24篇 |
出版年
2021年 | 4篇 |
2018年 | 5篇 |
2017年 | 2篇 |
2016年 | 3篇 |
2015年 | 6篇 |
2014年 | 5篇 |
2013年 | 2篇 |
2012年 | 9篇 |
2011年 | 9篇 |
2010年 | 8篇 |
2009年 | 10篇 |
2007年 | 13篇 |
2006年 | 11篇 |
2005年 | 10篇 |
2004年 | 5篇 |
2003年 | 10篇 |
2002年 | 3篇 |
2001年 | 6篇 |
1999年 | 5篇 |
1998年 | 24篇 |
1997年 | 23篇 |
1996年 | 17篇 |
1995年 | 23篇 |
1994年 | 20篇 |
1993年 | 33篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 9篇 |
1989年 | 17篇 |
1988年 | 21篇 |
1987年 | 34篇 |
1986年 | 21篇 |
1985年 | 20篇 |
1984年 | 8篇 |
1983年 | 12篇 |
1982年 | 6篇 |
1981年 | 12篇 |
1980年 | 12篇 |
1979年 | 1篇 |
1978年 | 7篇 |
1977年 | 5篇 |
1976年 | 2篇 |
1975年 | 5篇 |
1971年 | 1篇 |
1959年 | 1篇 |
1958年 | 1篇 |
1957年 | 3篇 |
1956年 | 3篇 |
1955年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有481条查询结果,搜索用时 0 毫秒
71.
Rosen BR; Fleming DM; Kushner DC; Zaner KS; Buxton RB; Bennet WP; Wismer GL; Brady TJ 《Radiology》1988,169(3):799
72.
73.
74.
75.
Magnetic resonance imaging of the brainstem: normal structure and basic functional anatomy 总被引:2,自引:0,他引:2
Flannigan BD; Bradley WG Jr; Mazziotta JC; Rauschning W; Bentson JR; Lufkin RB; Hieshima GB 《Radiology》1985,154(2):375-383
Normal structure and basic functional anatomy of the brainstem were studied using anatomic sections obtained with a cryomicrotome whole-organ sectioning technique. Major tracts and nuclei were identified and their function summarized. Magnetic resonance imaging of the brainstem was performed on 10 normal volunteers. By comparing these images with the corresponding anatomic sections, normal structures, including major tracts and nuclei, were identified. Knowledge of location and function of clinically important brainstem nuclei and tracts is necessary for optimal magnetic resonance image interpretation. 相似文献
76.
Greif WL; Buxton RB; Lauffer RB; Saini S; Stark DD; Wedeen VJ; Rosen BR; Brady TJ 《Radiology》1985,157(2):461-466
Paramagnetic agents enhance contrast between tissues in magnetic resonance (MR) imaging by altering tissue relaxation times. The effect of these changes on MR image intensity depends in part on the choice of operator-controlled pulse sequence parameters. With the newly described paramagnetic hepatobiliary contrast agent, iron(III) ethylenebis-(2-hydroxyphenylglycine), Fe(EHPG)-, an in vivo experimental analysis of pulse sequence optimization was performed on the rat. We compared the enhancement of the liver divided by background noise, EL/N, of standard inversion-recovery (IR) and spin-echo (SE) T1-weighted pulse sequences and several pulse sequences theoretically predicted to have improved EL/N. Optimization of the echo time (TE = TEmin) gave a substantial (greater than 60%) increase in EL/N over the standard IR and SE pulse sequences. Images obtained with optimized repetition rate and inversion time gave only a slight additional improvement. Within the uncertainties of our relaxation measurements, the measured changes in EL/N with pulse sequence optimization corresponded well with theoretical predictions. With the experimental and theoretical data, the importance of using a short echo time to obtain maximal T1 contrast in contrast-enhanced MR imaging and the relative merits of optimized SE versus IR pulse sequences for contrast-enhanced MR imaging are discussed. 相似文献
77.
78.
79.
80.
Natural killer cell precursors in the CD44neg/dim T-cell receptor population of mouse bone marrow 总被引:1,自引:0,他引:1
Natural killer (NK) cells develop from the nonadherent cell component of NK long-term bone marrow (BM) cultures (NK-LTBMC). Because these nonadherent cells are depleted of mature NK cells and T cells, but appear to enriched for NK precursors, they were used as a starting population to begin to define the NK precursors that function in NK- LTBMC. As the stromal cell component of NK-LTBMC has been shown to support interleukin (IL)-2-induced, CD44 dependent, NK cell development from nonadherent NK precursors, NK-LTBMC stroma was used in a limiting dilution assay (LDA) to quantitate the precursors. NK-LTBMC in 96-well plates were irradiated (20 Gy) to kill hematopoietic cells (including the NK precursors), seeded with limiting dilutions of the cells to be quantitated, cultured with 500 U/mL IL-2 for 13 days and assayed for development of NK activity by adding 51Cr-labeled YAC-1 cells to the wells and evaluating the release of 51Cr after 4 hours. Flow cytometric analysis, sorting, and quantitation of the nonadherent cell component of NK-LTBMC showed that NK precursors were concentrated in the CD44neg/dim subset that comprised 10% of the "lymphoid" gated cells. When the CD44neg/dim subset was sorted from BM of mice treated with 5- fluorouracil (5-FU) day before (-1FUBM), there were about 30% T cells, but no NK-1.1+ cells. When the T cells were removed by sorting and the CD44neg/dim, alphabeta, gammadelta T-cell receptorneg (TCR-) subpopulation was seeded onto irradiated stroma with IL-2, they proliferated, developed NK activity, became NK-1.1+ and CD44bright and remained alphabeta, gammadelta TCR-. The frequency of NK precursors in this population as estimated from the LDA was about 1/500. 相似文献