全文获取类型
收费全文 | 3044篇 |
免费 | 135篇 |
国内免费 | 13篇 |
专业分类
耳鼻咽喉 | 11篇 |
儿科学 | 14篇 |
妇产科学 | 23篇 |
基础医学 | 241篇 |
口腔科学 | 761篇 |
临床医学 | 244篇 |
内科学 | 692篇 |
皮肤病学 | 30篇 |
神经病学 | 199篇 |
特种医学 | 144篇 |
外科学 | 278篇 |
综合类 | 189篇 |
预防医学 | 116篇 |
眼科学 | 10篇 |
药学 | 173篇 |
中国医学 | 28篇 |
肿瘤学 | 39篇 |
出版年
2024年 | 4篇 |
2023年 | 94篇 |
2022年 | 72篇 |
2021年 | 140篇 |
2020年 | 106篇 |
2019年 | 253篇 |
2018年 | 278篇 |
2017年 | 141篇 |
2016年 | 83篇 |
2015年 | 66篇 |
2014年 | 206篇 |
2013年 | 178篇 |
2012年 | 99篇 |
2011年 | 127篇 |
2010年 | 85篇 |
2009年 | 102篇 |
2008年 | 91篇 |
2007年 | 142篇 |
2006年 | 72篇 |
2005年 | 78篇 |
2004年 | 65篇 |
2003年 | 39篇 |
2002年 | 15篇 |
2001年 | 25篇 |
2000年 | 19篇 |
1999年 | 20篇 |
1998年 | 18篇 |
1997年 | 15篇 |
1996年 | 9篇 |
1995年 | 4篇 |
1994年 | 7篇 |
1993年 | 31篇 |
1992年 | 12篇 |
1991年 | 12篇 |
1990年 | 8篇 |
1989年 | 12篇 |
1988年 | 4篇 |
1985年 | 44篇 |
1984年 | 55篇 |
1983年 | 29篇 |
1982年 | 56篇 |
1981年 | 26篇 |
1980年 | 22篇 |
1979年 | 24篇 |
1978年 | 42篇 |
1977年 | 13篇 |
1976年 | 21篇 |
1975年 | 46篇 |
1974年 | 40篇 |
1973年 | 37篇 |
排序方式: 共有3192条查询结果,搜索用时 562 毫秒
11.
Silvia Obenauer Christian Sohns Carola Werner Eckhardt Grabbe 《Journal of digital imaging》2006,19(3):258-263
The goal of this study was to evaluate the performance of a computer-aided detection (CAD) system in full-field digital mammography
(Senographe 2000D, General Electric, Buc, France) in finding out carcinomas depending on the parenchymal density. A total
of 226 mediolateral oblique (MLO) and 186 craniocaudal (CC) mammographic views of histologically proven cancers were retrospectively
evaluated with a digital CAD system (ImageChecker V2.3 R2 Technology, Los Altos, CA, USA). Malignant tumors were detected
correctly by CAD in MLO view in 84.85% in breasts with parenchymal tissue density of the American College of Radiology (ACR)
type 1, in 70.33% of the ACR type 2, in 68.12% of the ACR type 3, and in 69.70% of the ACR type 4. For the CC view, similar
results were found according to the ACR types. Using the chi-square and McNemar tests, there was no statistical significance.
However, a trend of better detection could be seen with decreasing ACR type. In conclusion, there seems to be a tendency for
breast tissue density to affect the detection rate of breast cancer when using the CAD system. 相似文献
12.
S M Flechner M I Lorber R H Kerman C T Van Buren C Wideman B D Kahan 《Human immunology》1985,14(3):305-313
The results of cadaveric retransplantation in 55 recipients immunosuppressed with cyclosporine and prednisone were compared to 156 recipients of primary renal allografts. By 3 yr posttransplant, there is no significant difference in patient survival, but the yearly graft survival for primary (79%, 72%, 72%) as compared to retransplant (69%, 58%, 58%) recipients was significantly (p less than 0.05) better. There was no significant difference in rejection episodes or mean +/- SD serum creatinine (mg/dl) at 2 yr between primary (32%, 2.14 +/- 1.1) and retransplant (33%, 2.08 +/- 1.4) patients, respectively. Donor source, third kidneys, human leukocyte antigen AB and Dr matching, percent reactive antibody levels, and cause of first graft loss do not have significant impact on cyclosporine-treated retransplant outcome. However, retransplant patients who have lost a previous graft in less than 3 months continue to be at high risk for subsequent early graft loss. These results suggest that the combination of cyclosporine and prednisone is the preferred regimen for cadaveric retransplantation. 相似文献
13.
Visual evoked potentials (VEPs) elicited by foveal presentation of words were compared to brain potentials evoked by the same words in a condition where subjects had to make a saccadic eye movement in order to perceive the words (saccade-related brain potentials, SRPs). Subjects had to categorize the words responding with a button press to stimuli belonging to the target (infrequent, P = 0.2) category. The VEP and SRP waveforms showed divergences in the early (up to 250 ms) components, but a marked similarity between the late components. Principal Component Analysis also revealed the same relationship between the two types of brain responses. Peak latency of the late SRP components measured from saccade offset showed an apparent processing advantage over the corresponding late components of VEPs. The N3 component, indexing semantic processing of visual patterns, peaked between 310 and 375 ms in the SRPs, while in the VEPs it appeared between 410 and 470 ms. The P4 component, associated with final stimulus evaluation, showed a similar latency benefit in favour of SRPs (420-500 ms vs 530-590 ms in VEPs). The mean reaction time was 74 ms shorter in the eye movement condition (measured from saccade offset) than in the VEP condition (703 vs 777 ms). The question of what kind of processes may contribute to the differences in mean RTs and to the latencies of the late components between the two conditions are discussed. We suggest that the late components (P3, N3 and P4) of the VEP and the SRP, respectively, index identical brain processes. 相似文献
14.
We have determined cutaneous DTH reactions to SK-SD and PPD and peripheral blood lymphocyte profiles in a group of asbestos workers in two consecutive surveys. It was found that asbestosis and, to a lesser extent, the presence of ANA are significantly correlated with the lack of response to the above antigens. 83% of asbestos workers when tested at a 4 year interval fell into the same two categories of responsiveness (lack of response or response at least to one antigen).The asbestosis cases had lower total lymphocyte count as well as proportions and absolute number of E-RFC as compared to asbestos workers without asbestosis and/or ANA. Furthermore, the latter group showed the lower percentages and absolute number of E-RFC than the matched controls. The presence of ANA is also correlated with lower proportions of E-RFC. However, this is related at least in part to asbestosis. 相似文献
15.
Standardization for image characteristics in telemammography using genetic and nonlinear algorithms 总被引:2,自引:0,他引:2
As the soft copy reading and computer assisted diagnosis (CAD) in mammography become more and more important, the standardization of digital images becomes paramount. Telemammography and telemedicine requires the standardization for image characteristics, such as image resolution, bit-depth and intensity response. Soft copy reading and CAD in mammography are both dependent on the characteristics of the source of the digital data, either direct digital mammography or digitized screen-film mammography. An algorithm developed on images from one database may not perform well as on images from another database (with a different digitization). In this paper, we describe two methods based on a genetic algorithm and a nonlinear algorithm for standardization of digitized and digital mammography. The proposed standardization techniques are based on geometric and intensity transformations that are discovered using a set of calibration images. A set of transformation algorithm is used to search for the best standardization. 相似文献
16.
An autoradiographic method combined with a rosette technique was used to assess the bactericidal activity of individual control and inflammatory peritoneal macrophages (PM phi) in the presence or absence of expression of Fc receptor for IgG (FcR). There was a lack of FcR reactivity in a certain percentage of both categories of PM phi exposed to E. coli X43, a bacterium which is readily phagocytosed in the presence of specific antibody. Both rosetting and non-rosetting PM phi were capable of phagocytosing E. coli X43, but inflammatory PM phi showed a marked reduction in their capacity to ingest these bacteria compared with control PM phi. Once ingested the E. coli X43 were killed equally well by non-rosetting and rosetting control and inflammatory PM phi. 相似文献
17.
M.D. Claudio Meirelles Medeiros M.D. Nilo Pinho Medeiros M.D. Nelson Carvalho de Nonohay M.D. Rubem Rodrigues 《Journal of electrocardiology》1985,18(4):409-413
A 53-year-old man with myocardial infarction was found to have frequent premature ventricular beats. The predominant pattern was classical concealed trigeminy; i.e., the number of conducted sinus beats, S, between extrasystoles satisfied the equation S = 3n + 2, where "n" is zero or any positive integer. Two other transient patterns also occurred. The first one was characterized by exceptional values of S, which satisfied the equation S = 3n + 3. In the second transient pattern, all values of S fitted the classical equation, but there were singularly absent values; i.e., the "n" in the equation was exclusively an odd number, giving rise to only prime numbers of interectopic conducted sinus beats. It is proposed in this last form that there are two sites of fixed block proximal to a variable distal block in a re-entry loop responsible for the ventricular extrasystoles. 相似文献
18.
van Rooij HH Pirovano IM Soudijn W 《Journal of pharmaceutical and biomedical analysis》1984,2(1):91-99
Methods have been developed for the determination of nicomorphine using reversed-phase HPLC with UV detection; for the simultaneous assay of morphine and mononicotinoylmorphine by a coupled normal-phase HPLC-radioimmunoassay method; and for conjugates of morphine and mononicotinoylmorphine by radioimmunoassay. The methods have been evaluated and applied to a pharmacokinetic study of nicomorphine administered intramuscularly. 相似文献
19.
动态心电图、高频心电图和运动试验诊断冠心病价值的比较 总被引:4,自引:0,他引:4
目的 比较动态心电图、高频心电图和运动试验在冠心病诊断中的意义。方法 对冠心病组(81例 )及对照组 (6 7例 )分别进行动态心电图、高频心电图、运动试验以及选择性冠状动脉造影检查 (2次检查间隔在 2周内 ) ,以至少一支冠脉直径狭窄≥ 5 0 %作为诊断冠心病的标准。结果 高频心电图诊断冠心病的敏感性高于动态心电图及运动试验 ,但特异性较这两种方法明显偏低 (P <0 .0 0 5 )。运动试验与动态心电图的敏感性无明显差异 (P >0 .0 5 ) ,但运动试验的特异性高于动态心电图 (P <0 .0 5 )。结论 动态心电图与运动试验是两种价值较高的冠心病诊断方法 相似文献