全文获取类型
收费全文 | 3417篇 |
免费 | 323篇 |
国内免费 | 5篇 |
专业分类
耳鼻咽喉 | 150篇 |
儿科学 | 145篇 |
妇产科学 | 76篇 |
基础医学 | 402篇 |
口腔科学 | 52篇 |
临床医学 | 350篇 |
内科学 | 716篇 |
皮肤病学 | 48篇 |
神经病学 | 321篇 |
特种医学 | 83篇 |
外科学 | 481篇 |
综合类 | 59篇 |
一般理论 | 2篇 |
预防医学 | 407篇 |
眼科学 | 44篇 |
药学 | 227篇 |
中国医学 | 1篇 |
肿瘤学 | 181篇 |
出版年
2021年 | 52篇 |
2020年 | 29篇 |
2019年 | 41篇 |
2018年 | 57篇 |
2017年 | 30篇 |
2016年 | 43篇 |
2015年 | 60篇 |
2014年 | 64篇 |
2013年 | 118篇 |
2012年 | 127篇 |
2011年 | 135篇 |
2010年 | 83篇 |
2009年 | 83篇 |
2008年 | 148篇 |
2007年 | 119篇 |
2006年 | 150篇 |
2005年 | 141篇 |
2004年 | 137篇 |
2003年 | 146篇 |
2002年 | 126篇 |
2001年 | 110篇 |
2000年 | 86篇 |
1999年 | 109篇 |
1998年 | 40篇 |
1997年 | 27篇 |
1996年 | 39篇 |
1995年 | 39篇 |
1993年 | 30篇 |
1992年 | 72篇 |
1991年 | 76篇 |
1990年 | 76篇 |
1989年 | 83篇 |
1988年 | 63篇 |
1987年 | 88篇 |
1986年 | 73篇 |
1985年 | 65篇 |
1984年 | 59篇 |
1983年 | 40篇 |
1982年 | 28篇 |
1981年 | 26篇 |
1979年 | 63篇 |
1978年 | 39篇 |
1977年 | 35篇 |
1976年 | 36篇 |
1975年 | 27篇 |
1974年 | 31篇 |
1973年 | 28篇 |
1972年 | 28篇 |
1971年 | 50篇 |
1968年 | 27篇 |
排序方式: 共有3745条查询结果,搜索用时 0 毫秒
1.
Katherine M. Duszynski Nicole L. Pratt John W. Lynch Jesia G. Berry Michael S. Gold 《Vaccine》2019,37(2):280-288
Objective
To determine whether differences in combination DTaP vaccine types at 2, 4 and 6?months of age were associated with mortality (all-cause or non-specific), within 30?days of vaccination.Design
Observational nationwide cohort study.Setting
Linked population data from the Australian Childhood Immunisation Register and National Death Index.Participants
Australian infants administered a combination trivalent, quadrivalent or hexavalent DTaP vaccine (DTaP types) between January 1999 and December 2010 at 2, 4 and 6?months as part of the primary vaccination series. The study population included 2.9, 2.6, & 2.3?million children in the 2, 4 and 6?month vaccine cohorts, respectively.Main outcome measures
Infants were evaluated for the primary outcome of all-cause mortality within 30?days. A secondary outcome was non-specific mortality (unknown cause of death) within 30?days of vaccination. Non-specific mortality was defined as underlying or other cause of death codes, R95 ‘Sudden infant death syndrome’, R96 ‘Other sudden death, cause unknown’, R98 ‘Unattended death’, R99 ‘Other ill-defined and unspecified cause of mortality’ or where no cause of death was recorded.Results
The rate of 30?day all-cause mortality was low and declined from 127.4 to 59.3 deaths per 100,000 person-years between 2 and 6?month cohorts. When compared with trivalent DTaP vaccines, no elevated risk in all-cause or non-specific mortality was seen with any quadrivalent or hexavalent DTaP vaccines, for any cohort.Conclusion
Use of routine DTaP combination vaccines with differing disease antigens administered during the first six months of life is not associated with infant mortality. 相似文献2.
Stephen R. Thomas Ronald G. Pratt Ronald W. Millard R. C. Samaratunga Yoseph Shiferaw Leland C. Clark Richard E. Hoffmann 《Journal of magnetic resonance imaging : JMRI》1994,4(4):631-635
Oxygen-sensitive F-19 magnetic resonance imaging of perfluorocarbon compounds requires that fluorocarbon T1 changes correlate with the local Po2 and not with the composition of the surrounding aqueous phase. The influence of various bioconstituents and paramagnetic ions within the aqueous phase on the F-19 fluorocarbon phase T1 for PFC emulsions was evaluated at 0.14 and 0.66 T. T1 was measured for FC-43, perflubron, and a fluorinated surfactant. Controlled variables introduced in the aqueous phase included annex solution constituents, blood, pH changes, and Gd-DTPA. For a constant Po2, the F-19 T1s were independent of the emulsion constituents, blood concentration, and pH. For FC-43 and perflubron, F-19 T1 was independent of the Gd-DTPA concentration, while the aqueous phase T1 decreased by more than an order of magnitude. XMO-10 (smallest emulsion particle size) showed a slight decrease in F-19 T1 with increasing Gd-DTPA concentration at 0.66 T. 相似文献
3.
4.
Jay Pratt 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》1998,118(1):135-138
It is well known that the removal of a fixation point prior to the presentation of a peripheral target dramatically reduces
saccadic reaction time (SRT). This effect has become known as the “gap effect”. The present study examined several detailed
kinematic variables to determine whether the removal of the fixation point also affects the manner in which saccades are produced.
The findings indicate that saccades that were initiated after the removal of the fixation point had higher average velocities
and reached greater peak velocities, accelerations, and decelerations than did saccades produced in the presence of the fixation
point. The results suggest that the removal of the fixation point may affect the force-time curves of saccades in addition
to affecting the time needed to initiate the saccades.
Received: 21 February 1997 / Accepted: 24 July 1997 相似文献
5.
OBJECTIVE: To indicate whether the double peaked N(1) to gaps in continuous white noise is a composite of onset and offset responses to transients or whether it reflects higher processing such as change or mismatch detection and to assess the role of attention in this process. METHODS: Evoked potentials were recorded to two binaural stimulus types: (1) gaps of different durations randomly distributed in continuous white noise; and (2) click pairs at intervals identical to those between gap onsets and offsets in the continuous noise stimulus. Potentials to these stimuli were recorded while subjects read a text and while detecting gaps in noise or click pairs. RESULTS: Potentials were detected to all click pairs and to gaps of 5 ms or longer, corresponding to the subjects' psychoacoustic gap detection threshold. With long gap durations of 200-800 ms, distinct potentials to gap onset and gap offset were observed. The waveforms to all click pairs and to offsets of long gaps were similar and single-peaked, while potentials to gaps of 10 ms and longer, and potentials to onsets of long gaps were double-peaked, consisting of two N(1) negativities, 60 ms apart, irrespective of gap duration. The first (N(1a)), was more frontal in its distribution and similar to that of clicks. The second (N(1b)) peak's distribution was more central/temporal and its source locations and time course of activity were distinct. No effects of attention on any of the varieties and constituents of N(1) were observed. CONCLUSIONS: Comparing potentials to gap onsets, to click pairs and to gap offsets, suggests that potentials to gap onsets involve not only sound onset/offset responses (N(1), N(1a)) but also the subsequent pre-attentive perception of the cessation of an ongoing sound (N(1b)). We propose that N(1b) is distinct from change or mismatch detection and is associated with termination of an ongoing continuous stimulus. We propose to call it the N(egation)-process. SIGNIFICANCE: A constituent of the N(1) complex is shown to be associated with the pre-attentive perception of termination of an ongoing stimulus and to have distinct scalp distribution and intracranial sources. 相似文献
6.
Ronald G. Pratt Jie Zheng Brent K. Stewart Yoseph Shiferaw Anthony J. McGoron Ranasinghage C. Samaratunga Stephen R. Thomas 《Magnetic resonance in medicine》1997,37(2):307-313
A limited flip angle gradient-echo 3D volume acquisition imaging protocol for mapping partial pressure of oxygen (pO2) in perfluorocarbon compounds (PFCs) at low field (0.14 T) is presented. The pO2 measurement method is based on the paramagnetic effect of dissolved molecular oxygen (O2) which reduces the PFC 19F T1? Specific objectives related to imaging of PFCs through use of the protocol include improved image signal-to-noise characteristics and elimination of 19F chemical shift artifacts. A parametric Wiener deconvolution filtering algorithm is used for suppression of 19F chemical shift artifacts. Application of the protocol is illustrated in a series of calculated pO2 maps of a gas equilibrated, multi-chamber phantom containing perfluorotributylamine (FC-43). The utility of the protocol is demonstrated in vivo through images of a commercially available perfluorocarbon based blood substitute emulsion containing FC-43 sequestered in the liver and spleen of a rat. 相似文献
7.
G Pratt 《Journal of clinical pathology》2002,55(5):273-283
8.
9.
Human renin is synthesized as an inactive zymogen (prorenin) which is processed to the active form. We synthesized an 11-amino acid peptide which spans the human prorenin processing site in order to develop a simple assay to study human prorenin activation. Six enzymes which are capable of activating recombinant prorenin in vitro were studied. Four of these enzymes digested the synthetic peptide in a specific fashion, as analyzed by reverse-phase high-performance liquid chromatography. Amino acid analysis of the purified digestion products revealed that trypsin cleaves between Arg-Leu, the authentic processing site, while kallikrein, plasmin and elastase all cleaved at alternate sites. On the other hand, pepsin and cathepsin D did not cleave this substrate, suggesting that the activation of prorenin by these proteases might occur at a site distinct from the authentic processing site. Our data suggest that this synthetic peptide may be used as a simple and specific assay for prorenin activation. 相似文献
10.
Ruprecht Nitschke Charles Pratt Michael Harris Jeffrey Krischer Teresa J. Vietti Holcombe Grier Willem Kamps Stuart Toledano 《Investigational new drugs》1992,10(2):93-96
CHIP (325 mg/M2), a second generation cisplatin derivative, was administered intravenously every 3 weeks to 85 pediatric patients with recurrent sarcomas (19), osteosarcomas (20), neuroblastoma (23), germ cell tumors (10), and other malignant tumors (7). Thirty-eight of them had been previously exposed to cisplatin. Partial remissions were only observed in 3 of 23 (13% SE=7%) patients having neuroblastoma. Severe thrombocytopenia (65%) and neutropenia (35%) were the dose limiting factors. 相似文献