全文获取类型
收费全文 | 8728篇 |
免费 | 636篇 |
国内免费 | 23篇 |
专业分类
耳鼻咽喉 | 42篇 |
儿科学 | 257篇 |
妇产科学 | 248篇 |
基础医学 | 1357篇 |
口腔科学 | 181篇 |
临床医学 | 1016篇 |
内科学 | 1682篇 |
皮肤病学 | 242篇 |
神经病学 | 1164篇 |
特种医学 | 217篇 |
外科学 | 703篇 |
综合类 | 67篇 |
一般理论 | 9篇 |
预防医学 | 793篇 |
眼科学 | 300篇 |
药学 | 531篇 |
中国医学 | 20篇 |
肿瘤学 | 558篇 |
出版年
2023年 | 78篇 |
2022年 | 118篇 |
2021年 | 207篇 |
2020年 | 185篇 |
2019年 | 215篇 |
2018年 | 273篇 |
2017年 | 212篇 |
2016年 | 222篇 |
2015年 | 272篇 |
2014年 | 303篇 |
2013年 | 457篇 |
2012年 | 738篇 |
2011年 | 719篇 |
2010年 | 377篇 |
2009年 | 341篇 |
2008年 | 641篇 |
2007年 | 596篇 |
2006年 | 552篇 |
2005年 | 520篇 |
2004年 | 485篇 |
2003年 | 449篇 |
2002年 | 437篇 |
2001年 | 64篇 |
2000年 | 41篇 |
1999年 | 69篇 |
1998年 | 84篇 |
1997年 | 77篇 |
1996年 | 70篇 |
1995年 | 48篇 |
1994年 | 52篇 |
1993年 | 44篇 |
1992年 | 28篇 |
1991年 | 22篇 |
1990年 | 17篇 |
1989年 | 15篇 |
1988年 | 15篇 |
1987年 | 19篇 |
1986年 | 19篇 |
1985年 | 19篇 |
1984年 | 22篇 |
1983年 | 17篇 |
1982年 | 23篇 |
1980年 | 16篇 |
1978年 | 23篇 |
1977年 | 14篇 |
1976年 | 14篇 |
1975年 | 12篇 |
1971年 | 12篇 |
1970年 | 10篇 |
1968年 | 10篇 |
排序方式: 共有9387条查询结果,搜索用时 10 毫秒
51.
Factors affecting the determination of threshold doses for allergenic foods: how much is too much? 总被引:15,自引:0,他引:15
Steve L Taylor Susan L Hefle Carsten Bindslev-Jensen S Allan Bock A Wesley Burks Lynn Christie David J Hill Arne Host Jonathan O'b Hourihane Gideon Lack Dean D Metcalfe Denise Anne Moneret-Vautrin Peter A Vadas Fabienne Rance Daniel J Skrypec Thomas A Trautman Ingrid Malmheden Yman Robert S Zeiger 《The Journal of allergy and clinical immunology》2002,109(1):24-30
BACKGROUND: Ingestion of small amounts of an offending food can elicit adverse reactions in individuals with IgE-mediated food allergies. The threshold dose for provocation of such reactions is often considered to be zero. However, because of various practical limitations in food production and processing, foods may occasionally contain trace residues of the offending food. Are these very low, residual quantities hazardous to allergic consumers? How much of the offending food is too much? Very little quantitative information exists to allow any risk assessments to be conducted by the food industry. OBJECTIVE: We sought to determine whether the quality and quantity of existing clinical data on threshold doses for commonly allergenic foods were sufficient to allow consensus to be reached on establishment of threshold doses for specific foods. METHODS: In September 1999, 12 clinical allergists and other interested parties were invited to participate in a roundtable conference to share existing data on threshold doses and to discuss clinical approaches that would allow the acquisition of that information. RESULTS: Considerable data were identified in clinical files relating to the threshold doses for peanut, cows' milk, and egg; limited data were available for other foods, such as fish and mustard. CONCLUSIONS: Because these data were often obtained by means of different protocols, the estimation of a threshold dose was very difficult. Development of a standardized protocol for clinical experiments to allow determination of the threshold dose is needed. 相似文献
52.
The Cbl family of ubiquitin ligases: critical negative regulators of tyrosine kinase signaling in the immune system 总被引:9,自引:0,他引:9
The Cbl family of proteins are evolutionarily conserved negative regulators of activated tyrosine kinase-coupled receptors. Antigen receptors are prominent targets of negative regulation by the Cbl family members, Cbl and Cbl-b, which proteins function as ubiquitin ligases. Cbl and Cbl-b contain substrate recognition domains that interact specifically with activated protein tyrosine kinases of the Src and Syk/ZAP-70 families. Cbl-mediated ubiquitination of these kinases leads to their degradation, resulting in attenuation of receptor signals. Cbl may also control activation-induced monoubiquitination of antigen receptors, thus facilitating their delivery to lysosomes for subsequent degradation. Finally, the interactions of Cbl proteins with downstream targets of tyrosine kinases, such as PI-3-kinase and Vav, could provide an additional mechanism to attenuate receptor signaling. By targeting multiple components of antigen receptor signaling for degradation, the Cbl protein family provides a critical mechanism to ensure an appropriate immune response. The hyperresponsiveness of Cbl(-/-) and Cbl-b(-/-) lymphocytes and the autoimmune phenotype of Cbl-b(-/-) mice lend strong support for this proposal. The ability to control early receptor signals through regulated protein degradation provides a novel paradigm of immunoregulation. 相似文献
53.
54.
Torous DK Hall NE Illi-Love AH Diehl MS Cederbrant K Sandelin K Pontén I Bolcsfoldi G Ferguson LR Pearson A Majeska JB Tarca JP Hynes GM Lynch AM McNamee JP Bellier PV Parenteau M Blakey D Bayley J van der Leede BJ Vanparys P Harbach PR Zhao S Filipunas AL Johnson CW Tometsko CR Dertinger SD 《Environmental and molecular mutagenesis》2005,45(1):44-55
An interlaboratory study was performed to validate an anti-CD71/flow cytometry-based technique for enumerating micronucleated reticulocytes (MN-RETs) in mouse peripheral blood. These experiments were designed to address International Workshop on Genotoxicity Test Procedures validation criteria by evaluating the degree of correspondence between MN-RET measurements generated by flow cytometry (FCM) with those obtained using traditional microscopy-based methods. In addition to these cross-methods data, flow cytometric MN-RET measurements for each blood sample were performed at two separate sites in order to evaluate the reproducibility of data between laboratories. In these studies, groups of male CD-1 mice were treated with vehicle (saline or vegetable oil), a negative control (saline or vegetable oil), or four dose levels of five known genotoxicants (clastogens: cyclophosphamide, benzo[a]pyrene, 5-fluorouracil, methotrexate; aneugen: vincristine sulfate). Exposure occurred on 3 consecutive days via intraperitoneal injection, and blood samples were obtained approximately 24 hr after the final treatment. MN-RET frequencies were determined for each sample based on the analysis of 2,000 (microscopy) and 20,000 (FCM) reticulocytes. Regardless of the method utilized, each genotoxic agent was observed to cause statistically significant increases in the frequency of MN-RETs, and each response occurred in a dose-dependent manner. Spearman's correlation coefficient (rs) for FCM versus microscopy-based MN-RET measurements (nine experiments, 252 paired measurements) was 0.740, indicating a high degree of correspondence between methods. The rs value for all flow cytometric MN-RET measurements performed at the two independent sites was 0.857 (n = 248), suggesting that the automated method is highly transferable between laboratories. Additionally, the flow cytometric system offered advantages relative to microscopy-based scoring, including a greater number of cells analyzed, much faster analysis times, and a greater degree of objectivity. Collectively, data presented in this report suggest that the overall performance of mouse peripheral blood micronucleus tests is enhanced by the use of the flow cytometric scoring procedure. 相似文献
55.
Adoptive immunotherapy for posttransplantation viral infections. 总被引:1,自引:0,他引:1
Catherine M Bollard Ingrid Kuehnle Ann Leen Cliona M Rooney Helen E Heslop 《Biology of blood and marrow transplantation》2004,10(3):143-155
Viral diseases are a major cause of morbidity and mortality after hemopoietic stem cell transplantation. Because viral complications in these patients are clearly associated with the lack of recovery of virus-specific cellular immune responses, reconstitution of the host with in vitro expanded cytotoxic T lymphocytes is a potential approach to prevent and treat these diseases. Initial clinical studies of cytomegalovirus and Epstein-Barr virus in human stem cell transplant patients have shown that adoptively transferred donor-derived virus-specific T cells may restore protective immunity and control established infections. Preclinical studies are evaluating this approach for other viruses while strategies for generating T cells specific for multiple viruses to provide broader protection are being evaluated in clinical trials. The use of genetically modified T cells or the use of newer suicide genes may result in improved safety and efficacy. 相似文献
56.
GABRD encoding a protein for extra- or peri-synaptic GABAA receptors is a susceptibility locus for generalized epilepsies 总被引:11,自引:0,他引:11
Dibbens LM Feng HJ Richards MC Harkin LA Hodgson BL Scott D Jenkins M Petrou S Sutherland GR Scheffer IE Berkovic SF Macdonald RL Mulley JC 《Human molecular genetics》2004,13(13):1315-1319
A major challenge in understanding complex idiopathic generalized epilepsies has been the characterization of their underlying molecular genetic basis. Here, we report that genetic variation within the GABRD gene, which encodes the GABAA receptor delta subunit, affects GABA current amplitude consistent with a model of polygenic susceptibility to epilepsy in humans. We have found a GABRD Glu177Ala variant which is heterozygously associated with generalized epilepsy with febrile seizures plus. We also report an Arg220His allele in GABRD which is present in the general population. Compared with wild-type receptors, alpha1beta2Sdelta GABAA receptors containing delta Glu177Ala or Arg220His have decreased GABAA receptor current amplitudes. As GABAA receptors mediate neuronal inhibition, the reduced receptor current associated with both variants is likely to be associated with increased neuronal excitability. Since delta subunit-containing receptors localize to extra- or peri-synaptic membranes and are thought to be involved in tonic inhibition, our results suggest that alteration of this process may contribute to the common generalized epilepsies. 相似文献
57.
Livia Maria Ionescu Ion Petrea Ingrid Ionescu Bujor Ioana Demetrescu 《Macromolecular chemistry and physics.》1983,184(5):1005-1015
Light scattering measurements from aqueous solutions for two samples of poly(acrylamide-co-maleic anhydride) in the presence of salt are conducted. One of the samples exhibits a negative initial slope and a minimum in the plot of the conventional reciprocal scattered intensity function of sin2 (θ/2). The explanation for this anomaly is a large optical anisotropy of the segment. A correction for this effect of segmental anisotropy is made. The behaviour of the other sample of this copolymer is typical for a polyelectrolyte. By analysing the disymmetry of the scattered light, the influence of the salt concentration on the polyion is evidenced by the determination of the macromolecular dimensions. Light scattering data allow the evaluation of the Mark-Kuhn-Houwink exponent a for various degrees of dissociation of the polyion; a correlation between the variation of a and the shape of the macromolecule is observed. 相似文献
58.
Taylor S Thordarson DS Maxfield L Fedoroff IC Lovell K Ogrodniczuk J 《Journal of consulting and clinical psychology》2003,71(2):330-338
The authors examined the efficacy, speed, and incidence of symptom worsening for 3 treatments of posttraumatic stress disorder (PTSD): prolonged exposure, relaxation training, or eye movement desensitization and reprocessing (EMDR; N = 60). Treaments did not differ in attrition, in the incidence of symptom worsening, or in their effects on numbing and hyperarousal symptoms. Compared with EMDR and relaxation training, exposure therapy (a) produced significantly larger reductions in avoidance and reexperiencing symptoms, (b) tended to be faster at reducing avoidance, and (c) tended to yield a greater proportion of participants who no longer met criteria for PTSD after treatment. EMDR and relaxation did not differ from one another in speed or efficacy. 相似文献
59.
Markus Wahrmann Sigurd Krieger Ingrid Raab Robert Ullrich Dontscho Kerjaschki 《Molecular immunology》2007,44(16):3932-3933
60.
Clara cell protein 16 (CC16) gene polymorphism influences the degree of airway responsiveness in asthmatic children 总被引:8,自引:0,他引:8
Sengler C Heinzmann A Jerkic SP Haider A Sommerfeld C Niggemann B Lau S Forster J Schuster A Kamin W Bauer C Laing I LeSouef P Wahn U Deichmann K Nickel R 《The Journal of allergy and clinical immunology》2003,111(3):515-519
BACKGROUND: Several studies have indicated linkage of chromosome 11q12-13 to asthma and associated traits. Among other candidate genes, the Clara cell protein 16 (CC16) gene maps to this region. CC16 is expressed in the bronchial epithelium and exhibits potent anti-inflammatory properties. A single-nucleotide polymorphism (SNP) in the CC16 gene (A38G) was previously associated with asthma. OBJECTIVE: We evaluated the role of the CC16 SNP in pediatric asthma and asthma severity in 2 German study populations. METHODS: The German Multicenter Allergy Study (MAS) cohort (n = 872, 94 asthmatic patients) and 112 allergic asthmatic children recruited in Freiburg, Germany, were included in the present study. Histamine provocations were performed at the age of 7 years in the MAS cohort to determine bronchial hyperreactivity; in the Freiburg study population a standardized exercise-induced decrease in FEV1 was evaluated. For genotyping, melting-curve analysis and restriction enzyme digestion were applied. RESULTS: No association of the CC16*38A allele with asthma could be observed in either study population. However, in asthmatic subjects (MAS cohort) PC(20)FEV(1) values were significantly lower in individuals homozygous or heterozygous for the CC16*38A allele compared with those in subjects with the CC16*38GG genotype (P <.05 and P <.03, respectively). Similarly, allergic asthmatic patients in the Freiburg cohort showed a significantly greater decrease in FEV1 after exercise when homozygous for the CC16*38A allele compared with that seen in asthmatic patients with the *38AG or *38GG genotype (P <.04 and P =.006, respectively). CONCLUSION: We conclude that the CC16*A38G SNP influences bronchial hyperreactivity and might be a genetic determinant of asthma severity in German children. 相似文献