全文获取类型
收费全文 | 18703篇 |
免费 | 1921篇 |
国内免费 | 27篇 |
专业分类
耳鼻咽喉 | 162篇 |
儿科学 | 690篇 |
妇产科学 | 319篇 |
基础医学 | 2589篇 |
口腔科学 | 381篇 |
临床医学 | 1983篇 |
内科学 | 3556篇 |
皮肤病学 | 471篇 |
神经病学 | 1724篇 |
特种医学 | 670篇 |
外国民族医学 | 11篇 |
外科学 | 2026篇 |
综合类 | 328篇 |
一般理论 | 25篇 |
预防医学 | 2029篇 |
眼科学 | 737篇 |
药学 | 1525篇 |
中国医学 | 12篇 |
肿瘤学 | 1413篇 |
出版年
2021年 | 272篇 |
2020年 | 154篇 |
2019年 | 314篇 |
2018年 | 307篇 |
2017年 | 215篇 |
2016年 | 260篇 |
2015年 | 324篇 |
2014年 | 428篇 |
2013年 | 616篇 |
2012年 | 834篇 |
2011年 | 883篇 |
2010年 | 491篇 |
2009年 | 453篇 |
2008年 | 716篇 |
2007年 | 723篇 |
2006年 | 742篇 |
2005年 | 743篇 |
2004年 | 762篇 |
2003年 | 681篇 |
2002年 | 644篇 |
2001年 | 639篇 |
2000年 | 680篇 |
1999年 | 544篇 |
1998年 | 238篇 |
1997年 | 216篇 |
1996年 | 194篇 |
1995年 | 195篇 |
1994年 | 173篇 |
1993年 | 177篇 |
1992年 | 430篇 |
1991年 | 428篇 |
1990年 | 415篇 |
1989年 | 425篇 |
1988年 | 373篇 |
1987年 | 419篇 |
1986年 | 349篇 |
1985年 | 359篇 |
1984年 | 291篇 |
1983年 | 269篇 |
1982年 | 162篇 |
1981年 | 166篇 |
1980年 | 164篇 |
1979年 | 279篇 |
1978年 | 222篇 |
1977年 | 159篇 |
1976年 | 168篇 |
1975年 | 164篇 |
1974年 | 183篇 |
1973年 | 172篇 |
1972年 | 171篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
Topical dexamethasone was used to elevate rabbit intraocular pressure in order to study the interaction with a steroid antagonist, mifepristone. Dexamethasone did not cause a consistently significant increase in intraocular pressure. Animals treated with mifepristone followed by dexamethasone showed no apparent increase in intraocular pressure after dexamethasone, indeed mifepristone caused a lower intraocular pressure than seen in other groups whether in the presence or absence of dexamethasone. Reductions of intraocular pressure when mifepristone was given after 14 days of dexamethasone administration were not found. No conclusion can be reached regarding any dexamethasone antagonism by mifepristone, except that intraocular pressure tended to be lower even in the presence of dexamethasone. 相似文献
23.
24.
25.
26.
Leeta Alison Green Khoi Nguyen Bijan Berenji Meera Iyer Eileen Bauer Jorge R Barrio Mohammad Namavari Nagichettiar Satyamurthy Sanjiv S Gambhir 《Journal of nuclear medicine》2004,45(9):1560-1570
Reporter probe 9-(4-18F-fluoro-3-[hydroxymethyl]butyl)guanine (18F-FHBG) and reporter gene mutant herpes simplex virus type 1 thymidine kinase (HSV1-sr39tk) have been used for imaging reporter gene expression with PET. Current methods for quantitating the images using the percentage injected dose per gram of tissue do not distinguish between the effects of probe transport and subsequent phosphorylation. We therefore investigated tracer kinetic models for 18F-FHBG dynamic microPET data and noninvasive methods for determining blood time-activity curves in an adenoviral gene delivery model in mice. METHODS: 18F-FHBG (approximately 7.4 MBq [approximately 200 microCi]) was injected into 4 mice; 18F-FHBG concentrations in plasma and whole blood were measured from mouse heart left ventricle (LV) direct sampling. Replication-incompetent adenovirus (0-2 x 10(9) plaque-forming units) with the E1 region deleted (n = 8) or replaced by HSV1-sr39tk (n = 18) was tail-vein injected into mice. Mice were dynamically scanned using microPET (approximately 7.4 MBq [approximately 200 microCi] 18F-FHBG) over 1 h; regions of interest were drawn on images of the heart and liver. Serial whole blood 18F-FHBG concentrations were measured in 6 of the mice by LV sampling, and 1 least-squares ratio of the heart image to the LV time-activity curve was calculated for all 6 mice. For 2 control mice and 9 mice expressing HSV1-sr39tk, heart image (input function) and liver image time-activity curves (tissue curves) were fit to 2- and 3-compartment models using Levenberg-Marquardt nonlinear regression. The models were compared using an F statistic. HSV1-sr39TK enzyme activity was determined from liver samples and compared with model parameter estimates. For another 3 control mice and 6 HSV1-sr39TK-positive mice, the model-predicted relative percentage of metabolites was compared with high-performance liquid chromatography analysis. RESULTS: The ratio of 18F-FHBG in plasma to whole blood was 0.84 +/- 0.05 (mean +/- SE) by 30 s after injection. The least-squares ratio of the heart image time-activity curve to the LV time-activity curve was 0.83 +/- 0.02, consistent with the recovery coefficient for the partial-volume effect (0.81) based on independent measures of heart geometry. A 3-compartment model best described 18F-FHBG kinetics in mice expressing HSV1-sr39tk in the liver; a 2-compartment model best described the kinetics in control mice. The 3-compartment model parameter, k3, correlated well with the HSV1-sr39TK enzyme activity (r2 = 0.88). CONCLUSION: 18F-FHBG equilibrates rapidly between plasma and whole blood in mice. Heart image time-activity curves corrected for partial-volume effects well approximate LV time-activity curves and can be used as input functions for 2- and 3-compartment models. The model parameter k3 from the 3-compartment model can be used as a noninvasive estimate for HSV1-sr39TK reporter protein activity and can predict the relative percentage of metabolites. 相似文献
27.
Tumor-associated retinal pigment epithelial proliferation simulating retinal pigment epithelial tear
A lesion with both the clinical and fluorescein angiographic appearance of the classical retinal pigment epithelial (RPE) tear was discovered over the dome of an actively growing metastatic choroidal tumor in a patient with a previous history of breast carcinoma. However, our patient exhibited no evidence of pigment epithelial detachment or age-related macular degeneration, the underlying cause of the RPE tear. Although we cannot be sure that a true RPE tear did not exist over our patient's tumor, more likely, we are observing a tumor induced zone of RPE dehiscence accompanied by RPE proliferation at its border, giving a very similar fundus appearance. Possible pathogenic mechanisms for the finding in our patient, and a comparison to those mechanisms responsible for the classical RPE tear, are discussed. 相似文献
28.
29.
30.