全文获取类型
收费全文 | 17729篇 |
免费 | 1903篇 |
国内免费 | 314篇 |
专业分类
耳鼻咽喉 | 61篇 |
儿科学 | 186篇 |
妇产科学 | 194篇 |
基础医学 | 2651篇 |
口腔科学 | 393篇 |
临床医学 | 2829篇 |
内科学 | 2999篇 |
皮肤病学 | 208篇 |
神经病学 | 1514篇 |
特种医学 | 1131篇 |
外科学 | 802篇 |
综合类 | 1739篇 |
一般理论 | 9篇 |
预防医学 | 2789篇 |
眼科学 | 318篇 |
药学 | 1088篇 |
47篇 | |
中国医学 | 343篇 |
肿瘤学 | 645篇 |
出版年
2024年 | 61篇 |
2023年 | 399篇 |
2022年 | 592篇 |
2021年 | 855篇 |
2020年 | 915篇 |
2019年 | 800篇 |
2018年 | 707篇 |
2017年 | 669篇 |
2016年 | 684篇 |
2015年 | 745篇 |
2014年 | 1174篇 |
2013年 | 1321篇 |
2012年 | 1119篇 |
2011年 | 1145篇 |
2010年 | 882篇 |
2009年 | 884篇 |
2008年 | 910篇 |
2007年 | 850篇 |
2006年 | 734篇 |
2005年 | 583篇 |
2004年 | 532篇 |
2003年 | 454篇 |
2002年 | 439篇 |
2001年 | 366篇 |
2000年 | 296篇 |
1999年 | 222篇 |
1998年 | 228篇 |
1997年 | 203篇 |
1996年 | 169篇 |
1995年 | 136篇 |
1994年 | 129篇 |
1993年 | 114篇 |
1992年 | 87篇 |
1991年 | 87篇 |
1990年 | 85篇 |
1989年 | 51篇 |
1988年 | 51篇 |
1987年 | 41篇 |
1986年 | 35篇 |
1985年 | 45篇 |
1984年 | 44篇 |
1983年 | 24篇 |
1982年 | 16篇 |
1981年 | 27篇 |
1980年 | 11篇 |
1979年 | 15篇 |
1978年 | 2篇 |
1977年 | 5篇 |
1975年 | 1篇 |
1966年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
71.
Identification and characterization of a DR4-restricted T cell epitope within chlamydia heat shock protein 60 总被引:11,自引:0,他引:11
下载免费PDF全文
![点击此处可从《Clinical and experimental immunology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
K H O DEANE R M JECOCK J H PEARCE J S H GASTON 《Clinical and experimental immunology》1997,109(3):439-445
An epitope within the 60 kD Chlamydia trachomatis heat shock protein (hsp) 60, recognized by a HLA-DRB1*0401-restricted T cell clone from a reactive arthritis patient, has been characterized. Stimulatory peptides contained a nine amino acid sequence (residues 38–46) predicted by algorithm to confer strong binding to DRB1*0401, with valine in the P1 position. The overall length of the peptide was critical for efficient recognition; peptides with at least one residue N-terminal to the putative P1 position were markedly more stimulatory than a peptide whose N-terminal is the P1 valine. Optimal responses were seen with 14mer peptides having two to three amino acids N- and C-terminal to the core 9mer. The sequence of the defined epitope is identical in hsp60 from both C. trachomatis and C. pneumoniae. Since the latter is a common respiratory pathogen, patients infected with C. trachomatis may already be primed for responses to hsp60 by prior infection with C. pneumoniae. Such secondary responses are important in the pathogenesis of chlamydia-induced inflammatory diseases such as trachoma. Priming by infection with enteric organisms was considered because of the similarity of the epitope sequence in Escherichia coli hsp60. However, although an E. coli-related peptide was recognized, intact E. coli hsp60 was not, suggesting that the epitope is cryptic in E. coli hsp60. Human hsp60 has six amino acid differences from chlamydial hsp60 in the epitope sequence and was not recognized. Thus cross-reactive recognition of self hsp60 could not be implicated in the pathogenesis of chlamydia-induced reactive arthritis in this patient. 相似文献
72.
In the oomycete, Phytophthora infestans, mating type is determined by a locus that segregates in a non-Mendelian manner consistent with its linkage to a system of
balanced lethals. The significance of this unusual phenomenon was addressed by studying the segregation patterns of DNA markers
linked to mating type in the related species, P. parasitica. This was done using loci identified by either RAPD analysis of P. parasitica crosses or by cross-hybridization with RFLP markers linked to mating type in P. infestans. The resulting data revealed that, unlike P. infestans, mating type in P. parasitica was regulated by a locus displaying Mendelian segregation. An improved model for mating-type determination in Phytophthora is presented.
Received: 21 October 1996 / 7 April 1997 相似文献
73.
肝硬化患者的脑电活动地形图 总被引:1,自引:0,他引:1
对20例无临床肝性脑病的失代偿期肝硬化患者进行脑电活动地形图(BEAM)检查,并与33例正常人作对照,以探讨亚临床肝性脑病(SHE)的诊断价值。结果表明,20例肝硬化患者中,BEAM正常5例,轻度异常5例,轻 ̄中度异常5例,中度异常5例,总异常率为75%(15/20)。BEAM异常的分布特点以弥漫性分布为主要表现,主要为慢频域(δ.θ.δ+θ/α+β)活动增强,Z值增高,只有3例波及α频域。提示: 相似文献
74.
A P Orfanos R Guthrie D C Jinks 《Clinica chimica acta; international journal of clinical chemistry》1987,166(2-3):219-225
Human alkaline phosphatases extracted with butanol from liver, kidney and placenta, and from foetal and adult small intestine each contain fragments with molecular masses within the range of approximately 8 kDa to 20 kDa which can be removed by digestion with bromelain. However, in the case of adult intestine, this fragment (which is presumed to represent a membrane-binding domain) can only be demonstrated in tissue extracted immediately after removal at operation. Similar fragments are also present in foetal intestinal phosphatase in amniotic fluid, and in liver and bone alkaline phosphatases recovered from serum. Again, however, adult intestinal phosphatase from serum differs in the absence of the bromelain-sensitive fragment. These observations indicate differences in the ways in which intestinal and non-intestinal alkaline phosphatases gain access to the circulation, and also have implications for structural studies on intestinal phosphatase extracted post mortem from adult tissue. 相似文献
75.
Gary W Thickbroom Michelle L Byrnes Rick Stell Frank L Mastaglia 《Movement disorders》2003,18(4):395-402
Previous work has suggested that there may be a widespread disturbance of motor control mechanisms in patients with cervical dystonia. In the present study, we used transcranial magnetic stimulation to investigate the topography of the corticomotor projection to the abductor pollicis brevis (APB) muscle in 10 subjects with idiopathic torticollis. Threshold-adjusted stimuli were delivered at multiple scalp sites during a low-level voluntary contraction of the APB, and maps were generated of motor evoked potential amplitude versus scalp site. The cortical maps for the APB on the side opposite to the direction of head rotation were displaced laterally or posteriorly in all subjects and reverted to a more normal position after botulinum toxin injection of the cervical muscles in 5 subjects. The findings point to a reversible reorganisation of the corticomotor representation of the hand on the same side as the sternocleidomastoid (SCM) muscle that is involved in producing the dystonia. These results provide further evidence for the involvement of cortical centres and for a more widespread abnormality of motor control mechanisms in focal dystonia. The findings also support the notion that head turning is chiefly mediated by the hemisphere ipsilateral to the direction of the head rotation by means of a corticomotor projection to the contralateral SCM. 相似文献
76.
Christine Ceci 《Nursing philosophy》2003,4(1):61-76
Abstract The paper contrasts understandings of knowledge grounded in Enlightenment norms with the departures from those norms taken by some strands of feminism and hermeneutics, as well as the contributions made by the writing of Michel Foucault. A reading of Foucault's writings on knowledge, power and the discursive constitution of self and world is offered as a potentially useful frame within which to raise questions about nursing, nurses and knowledge. 相似文献
77.
Topographical analysis of the EEG effects of a subconvulsive dose of lidocaine in healthy volunteers
O. DETSCH U. ERKENS U. JACOFSKY A. THIEL E. KOCHS G. HEMPELMANN 《Acta anaesthesiologica Scandinavica》1997,41(8):1039-1046
Background: The purpose of the present study was to assess the effects of intravenous lidocaine on spatial changes of electroen-cephalographic power and on psychomotoric status in conscious volunteers.
Methods: In 11 healthy volunteers lidocaine (2-min bolus, 100 mg; 15-min infusion, 40 μg kg-1 min-1 ) or placebo were given intravenously in a randomized, single-blinded, two-way crossover study. Haemodynamics and lidocaine plasma concentrations were measured at baseline and within a period of 30 min following bolus injection. Vigilance and emotional status were tested using visual analogue scales (VAS). Toxic CNS effects were evaluated by a questionnaire. The raw EEG (17 leads, reference Cz ) and computed power spectra were continuously recorded.
Results: The chosen lidocaine dosage led to nearly constant plasma concentrations (unbound lidocaine 2.5 min and 15 min after bolus 0.36±0.14 μg/ml and 0.30±0.06 μg/ml, respectively [mean±SD]). The placebo caused no symptoms, changes in VAS-scores or EEG-parameters. Lidocaine induced pronounced subjective symptoms and significant increases in delta activity for 15 min, most dominant at the frontotemporal and occipital leads (max. +219% O1 ). Frontal and occipital beta1 and beta2 power (max. +131% and +124% at O1 , respectively) was immediately increased after the bolus injection. No EEG changes occurred at central region Cz , and no interhemispheric EEG differences were noted. Theta, alphal, and alpha2 power remained unchanged.
Conclusion: The current data demonstrate simultaneous changes in psychomotoric status as well as delta and beta spectral power during lidocaine infusion. These data could be an indication that the pronounced frontotemporal and occipital EEG changes are the electroencephalographic expression of subjective sensations. 相似文献
Methods: In 11 healthy volunteers lidocaine (2-min bolus, 100 mg; 15-min infusion, 40 μg kg
Results: The chosen lidocaine dosage led to nearly constant plasma concentrations (unbound lidocaine 2.5 min and 15 min after bolus 0.36±0.14 μg/ml and 0.30±0.06 μg/ml, respectively [mean±SD]). The placebo caused no symptoms, changes in VAS-scores or EEG-parameters. Lidocaine induced pronounced subjective symptoms and significant increases in delta activity for 15 min, most dominant at the frontotemporal and occipital leads (max. +219% O
Conclusion: The current data demonstrate simultaneous changes in psychomotoric status as well as delta and beta spectral power during lidocaine infusion. These data could be an indication that the pronounced frontotemporal and occipital EEG changes are the electroencephalographic expression of subjective sensations. 相似文献
78.
YOSHIKAZU MURAWAKI YUJIRO IKUTA YUUKO NISHIMURA MASAHIKO KODA HIRONAKA KAWASAKI 《Journal of gastroenterology and hepatology》1996,11(5):443-450
In order to elucidate collagen metabolism in hepatocellular carcinoma (HCC) tissue, we compared levels of different potential markers of collagen metabolism and plasma transforming growth factor-β1 in patients with HCC and in patients with liver cirrhosis. Serum levels of prolyl hydroxylase and the tissue inhibitor of metalloproteinase-1 in patients with HCC were significantly higher than those in patients with liver cirrhosis and increased with the size of the HCC tumour, whereas the serum levels of procollagen type III propeptide and type IV collagen 7S domain were similar in the two groups. In HCC, the increased plasma transforming growth factor-β1 levels were closely correlated with serum levels of prolyl hydroxylase and the tissue inhibitor of metalloproteinase-1. These findings suggest that, in HCC tissue, the intracellular biosynthesis of collagen is enhanced, whereas the secretion of procollagen is disturbed and the degradation of collagen is suppressed by the excess production of the tissue inhibitor of metalloproteinase-1. The results also suggest that plasma transforming growth factor-β1 plays an important role in the altered metabolism of collagen in HCC. 相似文献
79.
健康成人135例心率变异性时域分析 总被引:2,自引:0,他引:2
目的:探讨国人心率变异时域分析各项指标的正常值。方法:应用清华-西安兰港监测系统对135例18~79岁健康成人连续24h动态心电图监测。结果:①心率变异性时域:SDNN、SDSD、SDANN、RMSSD、PNN50分别为129.52±27.25ms;21.18±8.20ms;114.78±26.84ms;31.36±12.67ms;8.50 ± 7.80ms,所测得正常值范围与国内外研究结果相似。②18~35岁组、36~59岁组,均与≥60岁组有非常显著的差异(P<0.01,或P<0.05)。③各年龄组男女间SDNN、SDSD、PNN50无显著差异(P>0.05),但SDANN男性较女性大(P<0.05);女性RMSSD较男性大(P<0.05)。结论:SDNN>100ms;SDSD>12ms;SDANN>87ms;RMSSD>18ms;PNN50>0.7%可作为HRV时域分析参考正常值。 相似文献
80.
Irwin M. Braverman 《Microcirculation (New York, N.Y. : 1994)》1997,4(3):329-340
The cutaneous microcirculation is organized as two horizontal plexuses. One is situated 1–1.5 mm below the skin surface, and the other is at the dermal-subcutaneous junction. Ascending arterioles and descending venules are paired as they connect the two plexuses. From the upper layer, arterial capillaries arise to form the dermal papillary loops that represent the nutritive component of the skin circulation. There are sphincter-like smooth muscle cells at the point where the ascending arterioles divide to form the arteriolar component of the upper horizontal plexus. At the dermal subcutaneous junction, there are collecting veins with 2-cusped valves that are oriented to prevent the retrograde flow of blood. Laser Doppler flowmetry (LDF) has demonstrated vasomotion of red cell flux localized to the sites of ascending arterioles. The simultaneous recording by LDF of red cell flux and the concentration of moving red blood cells from individual sites allows one to construct by computer topographic maps of these two valves. The two maps, based on initial studies using correlative skin biopsy specimens, can define 1-mm3 volumes of skin that are predominantly arteriolar in composition, predominantly venular in composition, or essentially devoid of all microvascular elements. The electron and light microscopic features that define the microvascular segments, when coupled with the ability of LDF to define the predominant microvascular segments under the probe, will allow one to study both the mechanisms of normal physiological states and the pathogenetic mechanisms underlying pathological skin disorders in which the microvasculature plays a predominant role. 相似文献