全文获取类型
收费全文 | 7573篇 |
免费 | 735篇 |
国内免费 | 230篇 |
专业分类
耳鼻咽喉 | 55篇 |
儿科学 | 40篇 |
妇产科学 | 21篇 |
基础医学 | 829篇 |
口腔科学 | 805篇 |
临床医学 | 614篇 |
内科学 | 982篇 |
皮肤病学 | 36篇 |
神经病学 | 508篇 |
特种医学 | 1069篇 |
外国民族医学 | 1篇 |
外科学 | 866篇 |
综合类 | 933篇 |
现状与发展 | 1篇 |
预防医学 | 535篇 |
眼科学 | 124篇 |
药学 | 631篇 |
7篇 | |
中国医学 | 336篇 |
肿瘤学 | 145篇 |
出版年
2024年 | 28篇 |
2023年 | 158篇 |
2022年 | 418篇 |
2021年 | 464篇 |
2020年 | 345篇 |
2019年 | 309篇 |
2018年 | 319篇 |
2017年 | 327篇 |
2016年 | 320篇 |
2015年 | 333篇 |
2014年 | 500篇 |
2013年 | 551篇 |
2012年 | 444篇 |
2011年 | 477篇 |
2010年 | 359篇 |
2009年 | 356篇 |
2008年 | 330篇 |
2007年 | 337篇 |
2006年 | 281篇 |
2005年 | 276篇 |
2004年 | 198篇 |
2003年 | 215篇 |
2002年 | 147篇 |
2001年 | 138篇 |
2000年 | 88篇 |
1999年 | 84篇 |
1998年 | 69篇 |
1997年 | 82篇 |
1996年 | 76篇 |
1995年 | 59篇 |
1994年 | 58篇 |
1993年 | 43篇 |
1992年 | 41篇 |
1991年 | 41篇 |
1990年 | 21篇 |
1989年 | 30篇 |
1988年 | 29篇 |
1987年 | 26篇 |
1986年 | 25篇 |
1985年 | 18篇 |
1984年 | 15篇 |
1983年 | 17篇 |
1982年 | 15篇 |
1981年 | 16篇 |
1980年 | 15篇 |
1979年 | 7篇 |
1978年 | 9篇 |
1977年 | 6篇 |
1974年 | 4篇 |
1972年 | 3篇 |
排序方式: 共有8538条查询结果,搜索用时 15 毫秒
11.
A restricted field of view (rFOV) approach for imaging a dynamic time series of volumes of limited spatial extent within a larger subject is described. The shorter readout with rFOV-MRI can be exploited to either limit image artifacts or increase spatial resolution. To accomplish rFOV imaging of a multislice volume for a dynamic series, an outer volume suppression (OVS) preparation that saturates signal external to a cylinder through the subject is followed by slice-selective excitation and a spiral readout. The pass- and stopband efficiencies of the OVS in an agar gel phantom were 97% (+/-1.5%) and 3% (+/-1%), respectively. Profiles of the temporal signal-to-noise ratio (SNR) were measured in a phantom and an adult brain. The rFOV sequence reduced distortions from off-resonance signal and T2*-induced blurring compared to a conventional sequence. Sequence utility is demonstrated for high-resolution rFOV functional MRI (fMRI) in the visual cortex. The rFOV sequence may prove to be useful for other multislice dynamic and high-resolution imaging applications. 相似文献
12.
报告用巯基棉(SCF)吸附富集分离──催化动力学法,测定了包头市区400名18~55岁健康成年人发硒值。结果显示:发硒值的中位数(M)为0.76mg/kg。男女分组分析,男性的M为0.69mg/kg,女性M为0.80mg/kg,男女两组间的差异无显著意义(P>0.05)。 相似文献
13.
S.D. Heintze A. Cavalleri G. Zellweger A. Büchler G. Zappini 《Dental materials》2008,24(10):1352-1361
OBJECTIVE: The purpose of this laboratory study was to compare the frequency of failures (complete fractures or partial cracks) of molar crowns made of two different all-ceramic materials during dynamic loading in a chewing simulator, as well as the fracture load when subjected to static loading, in relation to different dynamic loading and luting protocols. METHODS: One hundred and forty-four molar crowns fabricated with IPS Empress or an experimental e.max Press material with high translucency (e.max Press Exp) were luted on CAD/CAM milled PMMA abutments (first lower molar, circular chamfer) either with Variolink or glass-ionomer cement (GIC). All crowns were loaded according to three different loading protocols (n=12 per group) and two force profiles (sinusoidal, rectangular) in a pneumatically driven chewing simulator with a steel stylus (? 8mm) and they underwent simultaneous thermocycling (5 degrees C/55 degrees C). After each phase the crowns were evaluated with regard to fractures or cracks. After dynamic testing, the crowns that did not fail were subjected to compression loading until complete fracture in a universal testing machine (UTM). As control groups, unloaded crowns were also subjected to a UTM. Survival statistics with log-rank tests were applied for the results of the dynamic loading, while ANOVA with post hoc Tukey B was used for the fracture load results and two-way ANOVA was carried out for logarithmically transformed data. Weibull statistics were calculated for pooled fracture load data of the dynamically loaded and control groups. RESULTS: In the 144 IPS Empress crowns, complete fractures were observed in 9 crowns and partial cracks in another 3 crowns. When the data was pooled, a statistically significant increase in fractures occurred when the sinusoidal force profile was applied compared to a rectangular force profile (log-rank, p<0.05). No fractures occurred in the e.max Press Exp crowns. The two-way ANOVA showed that the type of luting protocol used had the most significant effect on the fracture load of both materials. In conjunction with Empress, however, the luting material influenced the variability twice as much as in e.max Press Exp. There was no statistically significant difference in the fracture load of GIC-luted e.max Press Exp crowns and that of the Variolink luted Empress crowns. The force profile had a significant effect on the fracture load only of the Empress crowns but not of the e.max Press Exp crowns. Weibull statistics revealed a higher scattering of the data of dynamically loaded crowns compared to that of the control groups. CONCLUSIONS: For testing all-ceramic materials, dynamic loading is indispensable to draw valid conclusions on clinical performance of all-ceramic molar crowns. A sinusoidal profile is advisable, while a gradual increase of the force amplitude does not significantly affect the results. 相似文献
14.
Werner Spileers Guy A. Orban Hugo Maes Luc Missotten 《Documenta ophthalmologica. Advances in ophthalmology》1988,68(3-4):363-374
CMSS-VEPs are presented as a sensitive, non-invasive functional investigation technique of the visual function, applicable in clinical practice. New improvements of the technique are presented. The underlying neuronal mechanisms are discussed. The clinical use is illustrated in a case of optic neuritis. 相似文献
15.
介绍供医用超声功率计用的两种高频、宽增益的小信号放大器,并比较了它们彼此的优缺点。 相似文献
16.
Summary Changes in the midshaft cross-sectional area of the ulna were measured in egg-laying turkeys on a diet insufficient in calcium.
Left: right comparisons were used to assess the bone loss over a six-week period due to 1) calcium insufficiency, 2) calcium
insufficiency plus disuse, and 3) calcium insufficiency and disuse interrupted by a short daily period of intermittent loading
applied from an external device. Calcium insufficiency alone in the intact ulna resulted in a 15% reduction in cross-sectional
area. In the functionally deprived bones this loss was increased to 32%. In bones where the disuse was interrupted by a single
short daily period of loading, the degree of bone loss was significantly modified (P<0.006) to 25%. No significant difference in the modulating effect of loading was achieved by varying the peak strain from
0.0015 to 0.003, the strain rate from 0.01 to 0.05, or the duration of the single loading period from 100 sec per day to 25
minutes. All the loading regimes employed had been demonstrated to be osteogenic in mature male birds on a diet sufficient
in calcium. 相似文献
17.
A method for dynamic imaging in MRI is presented that enables the acquisition of a series of images with both high temporal and high spatial resolution. The technique, which is based on the projection reconstruction (PR) imaging scheme, utilizes distinct data acquisition and reconstruction strategies to achieve this simultaneous capability. First, during acquisition, data are collected in multiple undersampled passes, with the view angles interleaved in such a way that those of subsequent passes bisect the views of earlier ones. During reconstruction, these views are weighted according to a previously described k-space weighted image contrast (KWIC) technique that enables the manipulation of image contrast by selective filtering. Unlike conventional undersampled PR methods, the proposed dynamic KWIC technique does not suffer from low image SNR or image degradation due to streaking artifacts. The effectiveness of dynamic KWIC is demonstrated in both simulations and in vivo, high-resolution, contrast-enhanced imaging of breast lesions. 相似文献
18.
王佑三 《山东中医药大学学报》1990,(4)
《明天的医学向何处去》一文是王佑三同志应中国中医研究院、中西医结合研究会1990~2010年中医药研究的重大进展与突破预测研究课题组和中国人体科学学会之约所撰。本报征得作者同意稍加删节后发表,期望引起对“明天的医学”的关注。 相似文献
19.
A. Urbano C. Babiloni P. Onorati F. Carducci A. Ambrosini L. Fattorini F. Babiloni 《The European journal of neuroscience》1998,10(2):765-770
We modelled the responses of human primary sensorimotor areas and supplementary motor area to simple, self-initiated unilateral and simultaneous bilateral middle finger movements using a novel high-resolution electroencephalography technology. The results support the view that these cortical motor areas are involved in parallel and present similar activity in the preparation, initiation, and execution of the contralateral and bilateral movements. Furthermore, the left primary sensorimotor area (dominant hemisphere) appears to be activated more than the right primary sensorimotor area during the preparation and performance of the ipsilateral movements. 相似文献
20.
JOOP KONSTEN COR G.M.I. BAETEN KAREL DEN DULK FRANK SPAANS† 《Pacing and clinical electrophysiology : PACE》1992,15(5):825-830
Electromagnetic fields and myopotentials from skeletal muscle may interfere with the function of a cardiac pacemaker. A 65-year-old woman with a unipolar DDD cardiac pacemaker underwent dynamic graciloplasty (transposition of the gracilis muscle around the anal canal and subsequent implantation of a bipolar pulse generator to stimulate the gracilis muscle), for the treatment of fecal incontinence. This gracilis pulse generator is turned "off" with an external magnet to allow defecation. Appropriate functioning of these two pulse generators (the cardiac pacemaker and the gracilis pulse generator) was tested during implantation of the gracilis pulse generator and afterwards. It was demonstrated that the combination could be used safely in this patient. 相似文献