全文获取类型
收费全文 | 124939篇 |
免费 | 8274篇 |
国内免费 | 454篇 |
专业分类
耳鼻咽喉 | 1632篇 |
儿科学 | 3305篇 |
妇产科学 | 2077篇 |
基础医学 | 16005篇 |
口腔科学 | 2376篇 |
临床医学 | 12576篇 |
内科学 | 26394篇 |
皮肤病学 | 1920篇 |
神经病学 | 11996篇 |
特种医学 | 4278篇 |
外国民族医学 | 4篇 |
外科学 | 18104篇 |
综合类 | 1905篇 |
现状与发展 | 1篇 |
一般理论 | 167篇 |
预防医学 | 11154篇 |
眼科学 | 2914篇 |
药学 | 8715篇 |
2篇 | |
中国医学 | 172篇 |
肿瘤学 | 7970篇 |
出版年
2023年 | 511篇 |
2022年 | 836篇 |
2021年 | 2081篇 |
2020年 | 1231篇 |
2019年 | 2019篇 |
2018年 | 2326篇 |
2017年 | 1796篇 |
2016年 | 1965篇 |
2015年 | 2419篇 |
2014年 | 3449篇 |
2013年 | 5342篇 |
2012年 | 7784篇 |
2011年 | 8293篇 |
2010年 | 4699篇 |
2009年 | 4516篇 |
2008年 | 7983篇 |
2007年 | 8530篇 |
2006年 | 8367篇 |
2005年 | 8646篇 |
2004年 | 8183篇 |
2003年 | 8017篇 |
2002年 | 7588篇 |
2001年 | 1190篇 |
2000年 | 937篇 |
1999年 | 1243篇 |
1998年 | 1707篇 |
1997年 | 1427篇 |
1996年 | 1163篇 |
1995年 | 1153篇 |
1994年 | 945篇 |
1993年 | 960篇 |
1992年 | 766篇 |
1991年 | 709篇 |
1990年 | 681篇 |
1989年 | 634篇 |
1988年 | 581篇 |
1987年 | 548篇 |
1986年 | 547篇 |
1985年 | 668篇 |
1984年 | 831篇 |
1983年 | 834篇 |
1982年 | 1163篇 |
1981年 | 1055篇 |
1980年 | 951篇 |
1979年 | 473篇 |
1978年 | 578篇 |
1977年 | 549篇 |
1976年 | 450篇 |
1975年 | 408篇 |
1974年 | 367篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
19 polygraphic sleep recordings from 12 patients with Pick's Disease, including four histologically proved cases, were compared to those of an age-matched control group. Symptoms had been present for a mean 8 years, the patients being aged 59 to 78 (mean 70.5 years). All sleep stages could be identified. Total sleep time was reduced and the number of awakenings was sharply increased. High proportion of stage 1 contrasted with the reduction in the other sleep stages with disappearance of stage 4 in advanced cases. REM Sleep was identified in all recordings, although reduced as a function of the length of the illness; its production as a function of total sleep time was not different from that of the control. REM Sleep appeared often fragmented and with a remarkably short latency, reminiscent of that observed in severely depressed patients. 相似文献
52.
53.
Comparison of 2-dimensional and 3-dimensional acquisition for 18F-FDG PET oncology studies performed on an LSO-based scanner. 总被引:1,自引:0,他引:1
Martin A Lodge Ramsey D Badawi Richard Gilbert Pablo E Dibos Bruce R Line 《Journal of nuclear medicine》2006,47(1):23-31
Three-dimensional (3D) PET acquisition has the potential to reduce image noise but the advantage of 3D PET for studies outside the brain has not been well established. To compare the performance of 2-dimensional (2D) and 3D acquisition for whole-body (18)F-FDG applications, a series of patient studies were performed using a lutetium oxyorthosilicate (LSO)-based tomograph. METHODS: Comparative 2D and 3D images were acquired for 27 oncology patients using an LSO-based tomograph. Data acquisition (350-650 keV, 6 ns) started 99 +/- 12 min (mean +/- SD) after injection of 624 +/- 76 MBq (18)F-FDG. Bias caused by tracer redistribution and decay was eliminated by acquiring dynamic data over a single-bed position using a protocol that alternated between septa-in and septa-out modes (2D, 3D, 2D, 3D, 2D, 3D). Frames were combined to form 8 statistically independent sinograms: four 2D replicates (105 s) and four 3D replicates (90 s). The different frame durations in 2D and 3D compensated for the different number of overlapping bed positions required for an 85-cm whole-body study. Images were reconstructed with either 2D or fully 3D ordered-subsets expectation maximization (2 iterations and 8 subsets; 2D 6-mm gaussian, 3D 5- and 6-mm gaussian). Image target-to-background ratio was assessed by dividing the lesion maximum by the mean within a neighboring background region. Image noise was assessed by applying background regions of interest to the replicate images and calculating the within-patient coefficient of variation. RESULTS: The difference in target-to-background ratio between the 2D and 3D images, when they were filtered with 6-mm and 5-mm gaussian filters, respectively, was not highly statistically significant (P = 0.16). The mean ratio of 3D to 2D image values was 0.94 with 95% limits of agreement of 0.63-1.41. The within-patient coefficients of variation for the 2D and 3D images were 13% +/- 15% and 9% +/- 10%, respectively (P = 0.0005). CONCLUSION: Under conditions of matched target to-to-background ratios, the 3D mode was found to produce images with significantly less variability than the 2D mode. These data provide support for the use of 3D acquisition with LSO detectors to reduce scan times in whole-body (18)F-FDG applications. 相似文献
54.
Yubin Miao Said D Figueroa Darrell R Fisher Herbert A Moore Richard F Testa Timothy J Hoffman Thomas P Quinn 《Journal of nuclear medicine》2008,49(5):823-829
Peptide-targeted alpha-therapy with 7.4 MBq of (212)Pb-[1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid]-ReO-[Cys(3,4,10),d-Phe(7),Arg(11)]alpha-MSH(3-13) ((212)Pb-DOTA-Re(Arg(11))CCMSH) cured 45% of B16/F1 murine melanoma-bearing C57 mice in a 120-d study, highlighting its melanoma treatment potential. However, there is a need to develop an imaging surrogate for patient-specific dosimetry and to monitor the tumor response to (212)Pb-DOTA-Re(Arg(11))CCMSH therapy. The purpose of this study was to evaluate the potential of (203)Pb-DOTA-Re(Arg(11))CCMSH as a matched-pair SPECT agent for (212)Pb-DOTA-Re(Arg(11))CCMSH. METHODS: DOTA-Re(Arg(11))CCMSH was labeled with (203)Pb in 0.5 M NH(4)OAc buffer at pH 5.4. The internalization and efflux of (203)Pb-DOTA-Re(Arg(11))CCMSH were determined in B16/F1 melanoma cells. The pharmacokinetics of (203)Pb-DOTA-Re(Arg(11))CCMSH was examined in B16/F1 melanoma-bearing C57 mice. A micro-SPECT/CT study was performed with (203)Pb-DOTA-Re(Arg(11))CCMSH in a B16/F1 melanoma-bearing C57 mouse at 2 h after injection. RESULTS: (203)Pb-DOTA-Re(Arg(11))CCMSH was easily prepared in NH(4)OAc buffer and completely separated from the excess nonradiolabeled peptide by reversed-phase high-performance liquid chromatography (RP-HPLC). (203)Pb-DOTA-Re(Arg(11))CCMSH displayed fast internalization and extended retention in B16/F1 cells. Approximately 73% of (203)Pb-DOTA-Re(Arg(11))CCMSH activity internalized after a 20-min incubation at 25 degrees C. After incubation of the cells in culture medium for 20 min, 78% of internalized activity remained in the cells. (203)Pb-DOTA-Re(Arg(11))CCMSH exhibited a biodistribution pattern similar to that of (212)Pb-DOTA-Re(Arg(11))CCMSH in B16/F1 melanoma-bearing mice. (203)Pb-DOTA-Re(Arg(11))CCMSH exhibited a peak tumor uptake of 12.00+/-3.20 percentage injected dose per gram (%ID/g) at 1 h after injection. The tumor uptake gradually decreased to 3.43+/-1.12 %ID/g at 48 h after injection. (203)Pb-DOTA-Re(Arg(11))CCMSH exhibited a peak tumor-to-kidney uptake ratio of 1.53 at 2 h after injection. The absorbed doses to the tumor and kidneys were 4.32 and 4.35 Gy, respectively, per 37 MBq. Whole-body clearance of (203)Pb-DOTA-Re(Arg(11))CCMSH was fast, with approximately 89% of the injected activity cleared through the urinary system by 2 h after injection. (203)Pb showed 1.6-mm SPECT resolution, which was comparable to (99m)Tc. Melanoma lesions were visualized through SPECT/CT images of (203)Pb-DOTA-Re(Arg(11))CCMSH at 2 h after injection. CONCLUSION: (203)Pb-DOTA-Re(Arg(11))CCMSH exhibited favorable pharmacokinetic and tumor imaging properties, highlighting its potential as a matched-pair SPECT agent for (212)Pb-DOTA-Re(Arg(11))CCMSH melanoma treatment. 相似文献
55.
56.
57.
58.
59.
60.
J. Richard Hanley Lyndsey Nickels 《Cortex; a journal devoted to the study of the nervous system and behavior》2009,45(6):784-790
In this paper, we investigate the claim that although the same lexical units are involved in speech production and comprehension, there are separate input and output phoneme layers (Foygel and Dell, 2000). Data from a case series of aphasic patients are used to test this claim by examining the relationship between performance on a test of picture naming and performance on tests of phonological input. Estimates of each patient's semantic-lexical and phonological impairments in speech production were derived from Foygel and Dell's computational model of picture naming. It was found that the strength of the semantic-lexical impairments in speech production was significantly correlated with performance on auditory comprehension tests. This finding is consistent with the claim that the same lexical units are involved in speech comprehension and production. Conversely, the correlations between the strength of the phonological lesions in speech production and performance on tests of phonological input were non-significant, consistent with Foygel and Dell's claim that there are distinct input and output phoneme layers. 相似文献