全文获取类型
收费全文 | 180547篇 |
免费 | 10242篇 |
国内免费 | 173篇 |
专业分类
耳鼻咽喉 | 2634篇 |
儿科学 | 5945篇 |
妇产科学 | 4142篇 |
基础医学 | 27037篇 |
口腔科学 | 6030篇 |
临床医学 | 15281篇 |
内科学 | 34376篇 |
皮肤病学 | 4687篇 |
神经病学 | 18103篇 |
特种医学 | 7533篇 |
外国民族医学 | 11篇 |
外科学 | 26627篇 |
综合类 | 781篇 |
现状与发展 | 1篇 |
一般理论 | 101篇 |
预防医学 | 12099篇 |
眼科学 | 3661篇 |
药学 | 11591篇 |
中国医学 | 242篇 |
肿瘤学 | 10080篇 |
出版年
2023年 | 964篇 |
2022年 | 804篇 |
2021年 | 1844篇 |
2020年 | 1643篇 |
2019年 | 2106篇 |
2018年 | 3767篇 |
2017年 | 3219篇 |
2016年 | 4086篇 |
2015年 | 3719篇 |
2014年 | 4305篇 |
2013年 | 7075篇 |
2012年 | 9488篇 |
2011年 | 10366篇 |
2010年 | 5806篇 |
2009年 | 4419篇 |
2008年 | 10150篇 |
2007年 | 10659篇 |
2006年 | 10330篇 |
2005年 | 10118篇 |
2004年 | 9361篇 |
2003年 | 9321篇 |
2002年 | 8990篇 |
2001年 | 6721篇 |
2000年 | 8038篇 |
1999年 | 5031篇 |
1998年 | 1993篇 |
1997年 | 1713篇 |
1996年 | 1433篇 |
1995年 | 1160篇 |
1994年 | 1127篇 |
1993年 | 1077篇 |
1992年 | 1740篇 |
1991年 | 1569篇 |
1990年 | 1517篇 |
1989年 | 1470篇 |
1988年 | 1316篇 |
1987年 | 1281篇 |
1986年 | 1176篇 |
1985年 | 1318篇 |
1984年 | 1088篇 |
1983年 | 916篇 |
1982年 | 779篇 |
1981年 | 749篇 |
1980年 | 676篇 |
1979年 | 799篇 |
1978年 | 610篇 |
1977年 | 639篇 |
1976年 | 532篇 |
1975年 | 596篇 |
1974年 | 564篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Recently we observed that in human embryos and fetuses with a variety of malformations, not only malformed tissues, but also several non-malformed tissues displayed alterations in the glycosylation pattern. It was the aim of this work to investigate this more or less inexplicable phenomenon under experimental conditions. To this end, we studied a well known mouse model, the mouse mutant undulated, which has an exactly defined genetic defect (substitution in the pax-1 gene) leading to a localized malformation in the vertebral column. The glycosylation pattern was studied using lectin histochemistry. Distribution of binding sites for the lectins RCA I, Con A, SNA, SBA, PNA, LTA and WGA was studied during the organogenesis stages (i.e., days 11-18). It was striking that in mutants, changes in the glycosylation pattern were found not only in the malformed organ (i.e., vertebral anlage), but also in other embryonic tissues, which showed normal morphology. This suggests that the altered glycosylation seems to be a part of genetically determined phenomena throughout the entire organism. Our results show that a defect in a gene with a very restricted expression can cause universal changes in the glycosylation pattern during development. 相似文献
992.
Dipeptidyl carboxypeptidase 1 (DCP1) and butyrylcholinesterase (BCHE) gene interactions with the apolipoprotein E epsilon4 allele as risk factors in Alzheimer's disease and in Parkinson's disease with coexisting Alzheimer pathology 下载免费PDF全文
Mattila KM Rinne JO Röyttä M Laippala P Pietilä T Kalimo H Koivula T Frey H Lehtimäki T 《Journal of medical genetics》2000,37(10):766-770
Alzheimer's disease (AD) and Parkinson's disease (PD) are genetically heterogeneous. Dipeptidyl carboxypeptidase 1 (DCP1) and butyrylcholinesterase (BCHE) genes may modify the risk of these disorders. We investigated whether common polymorphisms present in these genes operate as risk factors for AD and PD in Finnish subjects, independently or in concert with the apolipoprotein E ε4 allele (APOE ε4). Eighty late onset sporadic AD patients, 53 PD patients (34 of whom had concomitant AD pathology), and 67 control subjects were genotyped for the insertion (I)/deletion (D) polymorphism of DCP1 and the K variant of BCHE. In logistic regression analysis, the DCP1 *I allele in combination with APOE ε4 significantly increased the risk of AD (OR 30.0, 95% CI 7.3-123.7), compared to subjects carrying neither of the alleles. Similar analysis showed that the risk of AD was significantly increased in subjects carrying both the BCHE wild type (*WT/*WT) genotype and ε4 (OR 9.9, 95% CI 2.9-33.8), compared to those without this BCHE genotype and ε4. Further, the risk of PD with AD pathology was significantly increased for carriers of DCP1 *I and ε4 (OR 8.0, 95% CI 2.1-31.1). We thus conclude that, in Finns, interaction between DCP1 *I and ε4 increases the risk of AD as well as of PD with coexisting Alzheimer pathology, which underlines the importance of the DCP1 I/D polymorphism in the development of Alzheimer neuropathology, whereas the wild type BCHE genotype in combination with ε4 had a combined effect with regard to the risk of AD.
Keywords: Alzheimer's disease; Parkinson's disease; dipeptidyl carboxypeptidase 1; butyrylcholinesterase 相似文献
Keywords: Alzheimer's disease; Parkinson's disease; dipeptidyl carboxypeptidase 1; butyrylcholinesterase 相似文献
993.
994.
Krustrup P Söderlund K Mohr M González-Alonso J Bangsbo J 《Pflügers Archiv : European journal of physiology》2004,449(1):56-65
To investigate recruitment of slow-twitch (ST) and fast-twitch (FT) muscle fibres, as well as the involvement of the various quadriceps femoris muscle portions during repeated, intense, one-legged knee-extensor exercise, 12 healthy male subjects performed two 3-min exercise bouts at ~110% maximum thigh O2 consumption (EX1 and EX2) separated by 6 min rest. Single-fibre metabolites were determined in successive muscle biopsies obtained from the vastus lateralis muscle (n=6) and intra-muscular temperatures were continuously measured at six quadriceps muscle sites (n=6). Creatine phosphate (CP) had decreased (P<0.05) by 27, 73 and 88% in ST fibres and 25, 71 and 89% in FT fibres after 15 and 180 s of EX1 and after 180 s of EX2, respectively. CP was below resting mean–1 SD in 15, 46, 84 and 100% of the ST fibres and 9, 48, 85 and 100% of the FT fibres at rest, after 15 and 180 s of EX1 and after 180 s of EX2, respectively. A significant muscle temperature increase (Tm) occurred within 2–4 s at all quadriceps muscle sites. Tm varied less than 10% between sites during EX1, but was 23% higher (P<0.05) in the vastus lateralis than in the rectus femoris muscle during EX2. Tm in the vastus lateralis was 101 and 109% of the mean quadriceps value during EX1 and EX2, respectively. We conclude that both fibre types and all quadriceps muscle portions are recruited at the onset of intense knee-extensor exercise, that essentially all quadriceps muscle fibres are activated during repeated intense exercise and that metabolic measurements in the vastus lateralis muscle provide a good indication of the whole-quadriceps muscle metabolism during repeated, intense, one-legged knee-extensor exercise. 相似文献
995.
Jacobi F Wittchen HU Holting C Höfler M Pfister H Müller N Lieb R 《Psychological medicine》2004,34(4):597-611
BACKGROUND: The German National Health Interview and Examination Survey (GHS) is the first government mandated nationwide study to investigate jointly the prevalence of somatic and mental disorders within one study in the general adult population in Germany. This paper reports results from its Mental Health Supplement (GHS-MHS) on 4-week 12-month, and selected lifetime prevalence of a broad range of DSM-IV mental disorders, their co-morbidity and correlates in the community. METHODS: The sample of the GHS-MHS (n=4181; multistage stratified random sample drawn from population registries; conditional response rate: 87.6%) can be regarded as representative for the German population aged 18-65. Diagnoses are based on fully structured computer assisted clinical interviews (M-CIDI), conducted by clinically trained interviewers. RESULTS: 12-month prevalence for any DSM-IV study disorder is 31% (lifetime: 43%; 4-week: 20%) with anxiety disorders, mood disorders and somatoform syndromes being the most frequent diagnoses. Retrospective age of onset information reveals that most disorders begin early in life. Co-morbidity rates among mental disorders range from 44% to 94%. Correlates of increased rates of mental disorders and co-morbidity were: female gender (except for substance disorders), not being married, low social class, and poor somatic health status. Health care utilization for mental disorders depended on co-morbidity (30% in 'pure', 76% in highly co-morbid cases) and varied from 33% for substance use disorders to 75% for panic disorder. CONCLUSIONS: Results confirm and extend results from other national studies using the same assessment instruments with regard to prevalence, co-morbidity and sociodemographic correlates, covering a broader range of DSM-IV disorders [i.e. somatoform disorders, all anxiety disorders (except PTSD), mental disorders due to substance or general medical factor, eating disorders]. Intervention rates were higher than in previous studies, yet still low overall. 相似文献
996.
Höglund M Gisselsson D Soller M Hansen GB Elfving P Mitelman F 《Cancer Genetics and Cytogenetics》2004,154(1):1-9
Molecular cytogenetic analysis frequently shows human papillomavirus (HPV) integration near translocation breakpoints in cervical cancer cells. We have recently described a cluster of HPV18 integrations in the distal end of the common fragile site FRA8C at 8q24 in primary cervical carcinoma samples. Chromosome band 8q24 contains the MYC gene (alias c-MYC), FRA8C, and FRA8D. The MYC gene is frequently deregulated--usually by translocation or amplification--in various tumor types. In the present study, we performed a molecular cytogenetic analysis of HPV18 integration patterns and the 8q24 translocation in a primary cervical carcinoma and in HeLa cells using combined binary ratio-fluorescence in situ hybridization. Our aim was to determine how the chromosomal breaks involved in these events relate physically to the MYC gene; whether they map to the FRA8C site, the FRA8D site, or both; and how they correlate with the occurrence of DNA flexibility domains. The 8q24 translocation breakpoints mapped between stretches of integrated HPV18 sequences in the distal end of FRA8C. This region contained DNA helix flexibility clusters, several of which mapped in the vicinity of HPV integration sites and translocation breakpoints in cervical carcinomas. DNA helix flexibility clusters were also found near known MYC translocation breakpoints in Burkitt lymphomas (BL), but most BL breakpoints mapped clearly outside FRA8C. Our data revealed that FRA8C is involved in HPV integration and chromosomal translocations in cervical carcinoma; however, this fragile site is not involved in classical MYC translocations in most BLs. In the context of the familial nature of cervical cancer, FRA8C may be considered a candidate susceptibility region for cervical carcinoma. 相似文献
997.
Interferon-gamma (IFN-gamma) and IL-4 expressed during mercury-induced membranous nephropathy are toxic for cultured podocytes. 下载免费PDF全文
W Coers J T Vos P H Van der Meide M L Van der Horst S Huitema J J Weening 《Clinical and experimental immunology》1995,102(2):297-307
The subepithelial immune deposits of Dorus Zadel Black (DZB) rats with mercury-induced membranous nephropathy consist of autoantibodies directed to laminin P1 and of complement. The animals develop massive proteinuria within 10-14 days which is associated with obliteration of foot processes of glomerular visceral epithelial cells (GVEC), or podocytes. Previous studies indicate that these autoantibodies are probably not the sole mediator of proteinuria and GVEC damage. In this study we investigated whether circulating or macrophage-derived cytokines can contribute to the GVEC changes as detected in vivo. In vivo at the height of the proteinuria, increased intraglomerular IFN-gamma immunoreactivity was found. In diseased rats a five-fold increase in intraglomerular macrophages was found, but we could not detect intraglomerular IFN-alpha, IFN-beta, IL-1 beta or tumour necrosis factor-alpha (TNF-alpha) by using immunohistology. Subsequently, we exposed cultured GVEC to these cytokines to investigate their cytotoxic effects on several physiological and structural parameters. IFN-gamma and IL-4 were the only cytokines that exerted toxic effects, resulting in a rapidly decreased transepithelial resistance of confluent monolayers, which was closely associated with altered immunoreactivity of the tight junction protein ZO-1. IL-4 also affected vimentin and laminin immunoreactivity. IFN-gamma and IL-4 only interfered with monolayer integrity when added to the basolateral side of the GVEC, indicating specific (receptor-mediated) effects. Only IL-4 decreased the viability of the cells, and treated monolayers demonstrated an increased passage of the 44-kD protein horseradish peroxidase. From our experiments we concluded that IFN-gamma subtly affected monolayer integrity at the level of the tight junctions, and that IL-4 additionally induced cell death. We hypothesize that the toxic effects of the cytokines IFN-gamma and IL-4 as seen with cultured podocytes are necessary together with the autoantibodies, for the ultimate induction of proteinuria in mercury nephropathy in the DZB rat. 相似文献
998.
Marius J. van der Mooren Antonius G. J. M. Hanselaar George F. Borm Rune Rolland 《Maturitas》1994,20(2-3):175-180
Objective: To describe changes in the withdrawal bleeding pattern and endometrial histology during a sequential 17β-estradiol —dydrogesterone regimen in postmenopausal women. Design: Open-label, non-comparative, prospective study. Setting: Gynecological outpatient department of a university hospital. Patients: Twenty-seven healthy nonhysterectomized postmenopausal women. Interventions: Continuous micronized 17β-estradiol supplementation, 2 mg daily, and cyclic administration of dydrogesterone, 10 mg daily for the first half of each 28 day treatment cycle. Main Outcome Measures: Changes in the characteristics of the withdrawal bleeding pattern and the endometrial biopsy histology during 2 years of treatment. Results: The initial withdrawal bleeding was comparable to normal menstruation with respect to amount and duration. During the 2 years of treatment the bleeding showed a significant tendency to become shorter with less blood loss. This was mainly the result of the decrease (P < 0.001) in the number of days per cycle with bleeding grade II (normal menstruation). None of the women developed endometrial hyperplasia, and in almost all women the given hormone replacement therapy regimen induced secretory or atrophic changes of the endometrium. Conclusions: This sequential 17β-estradiol —dydrogesterone regimen can be regarded as safe with respect to the prevention of endometrial disease and appeared to foster patient compliance. 相似文献
999.
Glycoprotein B of bovine herpesvirus type 4: Its phylogenetic relationship to gB equivalents of the herpesviruses 总被引:1,自引:0,他引:1
Michael Goltz Hermann Broll Annette Mankertz Wolfgang Weigelt Hanns Ludwig Hans-Jörg Buhk Kerstin Borchers 《Virus genes》1994,9(1):53-59
In order to estimate the phylogenetic relationship of BHV-4 among the herpesviruses, we have cloned and sequenced its glycoprotein B (gB). The 2.6 kb open reading frame codes for a 874 amino acid long protein. The comparison of its deduced amino acid sequence with those of its counterparts in 19 distinct herpesviruses groups BHV-4 into the -herpesvirinae. The calculation of an evolutionary tree emphasized that BHV-4 is more closely related to herpesvirus saimiri (HVS) than to Epstein-Barr virus (EBV). However, in contrast to EBV and HVS, the gB of BHV-4 contains a putative protease cleavage site and 20 potential N-glycosylation sites. The alignment of the amino acid sequences revealed that 10 cysteine and 7 proline residues, as well as the motifs SPF and GQLG, were completely conserved among the 20 investigated gBs. 相似文献
1000.
Eccentric and concentric torque-velocity characteristics of the quadriceps femoris in man 总被引:2,自引:0,他引:2
Stephen H. Westing Jan Y. Seger Eddy Karlson Björn Ekblom 《European journal of applied physiology》1988,58(1-2):100-104
Summary The primary purpose of this investigation was to study the eccentric and concentric torque-velocity characteristics of the quadriceps femoris in man using a recently developed combined isometric, concentric and eccentric controlled velocity dynamometer (the SPARK System). A secondary purpose was to compare the method error associated with maximal voluntary concentric and eccentric torque output over a range of testing velocities. 21 males (21–32 years) performed on two separate days maximal voluntary isometric, concentric and eccentric contractions of the quadriceps femoris at 4 isokinetic lever arm velocities of 0° · s–1 (isometric), 30° · s–1 120° · s–1 and 270° · s–1. Eccentric peak torque and angle-specific torques (measured every 10° from 30° to 70°) did not significantly change from 0° · s–1 to 270° · s–1 (p>0.05) (with the exception of angle-specific 40° torque, which significantly increased;p<0.05). The mean method error was significantly higher for the eccentric tests (10.6%±1.6%) than for the concentric tests (8.1%±1.7%) (p<0.05). The mean method error decreased slightly with increasing concentric velocity (p>0.05), and increased slightly with increasing eccentric velocity (p>0.05). A tension restricting neural mechanism, if active during maximal eccentric contractions, could possibly account for the large difference seen between the present eccentric torque-velocity results and the classic results obtained from isolated animal muscle. 相似文献