全文获取类型
收费全文 | 218352篇 |
免费 | 15929篇 |
国内免费 | 764篇 |
专业分类
耳鼻咽喉 | 2506篇 |
儿科学 | 5770篇 |
妇产科学 | 4523篇 |
基础医学 | 28096篇 |
口腔科学 | 4707篇 |
临床医学 | 20916篇 |
内科学 | 46526篇 |
皮肤病学 | 2976篇 |
神经病学 | 20935篇 |
特种医学 | 7337篇 |
外国民族医学 | 13篇 |
外科学 | 34344篇 |
综合类 | 3572篇 |
现状与发展 | 2篇 |
一般理论 | 299篇 |
预防医学 | 19683篇 |
眼科学 | 4507篇 |
药学 | 14687篇 |
1篇 | |
中国医学 | 374篇 |
肿瘤学 | 13271篇 |
出版年
2023年 | 864篇 |
2022年 | 1433篇 |
2021年 | 3522篇 |
2020年 | 2167篇 |
2019年 | 3459篇 |
2018年 | 4060篇 |
2017年 | 3291篇 |
2016年 | 3482篇 |
2015年 | 4167篇 |
2014年 | 6219篇 |
2013年 | 9029篇 |
2012年 | 13391篇 |
2011年 | 14597篇 |
2010年 | 8265篇 |
2009年 | 7452篇 |
2008年 | 13837篇 |
2007年 | 14737篇 |
2006年 | 14224篇 |
2005年 | 14698篇 |
2004年 | 14075篇 |
2003年 | 13203篇 |
2002年 | 12721篇 |
2001年 | 2135篇 |
2000年 | 1742篇 |
1999年 | 2295篇 |
1998年 | 2900篇 |
1997年 | 2507篇 |
1996年 | 2288篇 |
1995年 | 2028篇 |
1994年 | 1821篇 |
1993年 | 1733篇 |
1992年 | 1445篇 |
1991年 | 1388篇 |
1990年 | 1274篇 |
1989年 | 1196篇 |
1988年 | 1207篇 |
1987年 | 1227篇 |
1986年 | 1204篇 |
1985年 | 1275篇 |
1984年 | 1649篇 |
1983年 | 1577篇 |
1982年 | 1896篇 |
1981年 | 1716篇 |
1980年 | 1624篇 |
1979年 | 954篇 |
1978年 | 1065篇 |
1977年 | 1005篇 |
1976年 | 914篇 |
1975年 | 759篇 |
1974年 | 761篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Between 1996 and 1998, two clades (B and C; genotype I) of dengue virus type 1 (DENV-1) appeared in Myanmar (Burma) that were new to that location. Between 1998 and 2000, a third clade (A; genotype III) of DENV-1, which had been circulating at that locality for at least 25 years, became extinct. These changes preceded the largest outbreak of dengue recorded in Myanmar, in 2001, in which more than 95% of viruses recovered from patients were DENV-1, but where the incidence of severe disease was much less than in previous years. Phylogenetic analyses of viral genomes indicated that the two new clades of DENV-1 did not arise from the, now extinct, clade A viruses nor was the extinction of this clade due to differences in the fitness of the viral populations. Since the extinction occurred during an inter-epidemic period, we suggest that it was due to a stochastic event attributable to the low rate of virus transmission in this interval. 相似文献
992.
Comorbid psychiatric disorders in depressed outpatients: demographic and clinical features 总被引:2,自引:0,他引:2
Rush AJ Zimmerman M Wisniewski SR Fava M Hollon SD Warden D Biggs MM Shores-Wilson K Shelton RC Luther JF Thomas B Trivedi MH 《Journal of affective disorders》2005,87(1):43-55
BACKGROUND: This study evaluated the clinical and sociodemographic features associated with various degrees of concurrent comorbidity in adult outpatients with nonpsychotic major depressive disorder (MDD). METHODS: Outpatients enrolled in the STAR*D trial completed the Psychiatric Diagnostic Screening Questionnaire (PDSQ). An a priori 90% specificity threshold was set for PDSQ responses to ascertain the presence of 11 different concurrent DSM-IV Axis I disorders. RESULTS: Of 1376 outpatients, 38.2% had no concurrent comorbidities, while 25.6% suffered one, 16.1% suffered two, and 20.2% suffered three or more comorbid conditions. Altogether, 29.3% met threshold for social anxiety disorder, 20.8% for generalized anxiety disorder, 18.8% for posttraumatic stress disorder, 12.4% for bulimia, 11.9% for alcohol abuse/dependence, 13.4% for obsessive-compulsive disorder, 11.1% for panic disorder, 9.4% for agoraphobia, 7.3% for drug abuse/dependence, 3.7% for hypochondriasis, and 2.2% for somatoform disorder. Those with more concurrent Axis I conditions had earlier ages at first onset of MDD, longer histories of MDD, greater depressive symptom severity, more general medical comorbidity (even though they were younger than those with fewer comorbid conditions), poorer physical and mental function, health perceptions, and life satisfaction; and were more likely to be seen in primary care settings. LIMITATIONS: Participants had to meet entry criteria for STAR*D. Ascertainment of comorbid conditions was not based on a structured interview. CONCLUSIONS: Concurrent Axis I conditions (most often anxiety disorders) are very common with MDD. Greater numbers of concurrent comorbid conditions were associated with increased severity, morbidity, and chronicity of their MDD. 相似文献
993.
994.
Adherence of Streptococcus pneumoniae to Human Bronchial Epithelial Cells (BEAS-2B) 总被引:1,自引:0,他引:1 下载免费PDF全文
John E. Adamou Theresa M. Wizemann Philip Barren Solomon Langermann 《Infection and immunity》1998,66(2):820-822
Pneumococcal adherence to alveolar epithelial cells and nasopharyngeal epithelial cells has been well characterized. However, the interaction of Streptococcus pneumoniae with bronchial epithelial cells has not been studied. We have now shown that pneumococci bind specifically to a human bronchial epithelial cell line (BEAS-2B cells). Pneumococci adhered to BEAS-2B cells in a time- and dose-dependent manner. These results suggest that the bronchial epithelium may serve as an additional site of attachment for pneumococci and demonstrate the utility of the BEAS-2B cell line for studying mechanisms of pneumococcal infection. 相似文献
995.
Detection of N-myc gene amplification by fluorescence in situ hybridization. Diagnostic utility for neuroblastoma. 总被引:4,自引:1,他引:4 下载免费PDF全文
D. N. Shapiro M. B. Valentine S. T. Rowe A. E. Sinclair J. E. Sublett W. M. Roberts A. T. Look 《The American journal of pathology》1993,142(5):1339-1346
We assessed fluorescence in situ hybridization (FISH) as an alternative to Southern blot analysis for determination of N-myc gene amplification in neuroblastoma. In the 44 pediatric solid tumor cell lines examined (20 neuroblastomas), the mean number of N-myc copies determined by FISH correlated closely with Southern blot results. There was wide intercellular variability in gene copy number in tumors that had evidence of amplification; however, tumors judged to be non-amplified completely lacked any cells with high N-myc copy number. FISH provided reliable estimates of N-myc amplification in 12 clinical samples even when the percentage of tumor was low. The other advantages of FISH over Southern blot analysis were speed and technical simplicity, ability to discern heterogeneous gene amplification among tumor cells in the same specimen, and capacity to determine the source of the amplified N-myc signal, whether extrachromosomal double-minute chromosomes, expanded intrachromosomal regions, or chromosome 2 aneuploidy. We conclude that FISH would refine the analysis of N-myc amplification in neuroblastoma and thus improve the assignment of patients to prognostic groups based on this unfavorable risk factor. 相似文献
996.
Differentiation of Strains of Infectious Bovine Rhinotracheitis Virus by Neutralization Kinetics with Late 19S Rabbit Antibodies 总被引:2,自引:0,他引:2 下载免费PDF全文
Two vaccine, two respiratory (infectious bovine rhinotracheitis [IBR]), and two genital (infectious pustular vulvovaginitis [IPV]) strains of infectious bovine rhinotracheitis virus were compared by neutralization kinetics using late 19S antibody (AB). The two vaccine strains were indistinguishable from one another, but were neutralized far more rapidly than the other four strains when either anti-IBR or anti-IPV 19S AB was used. The two IPV strains were indistinguishable from one another, but were neutralized significantly more rapidly than the two IBR strains when anti-IBR 19S AB was used. The 2 IBR strains were neutralized at a similar rate with the latter globulin preparation. Almost identical results were obtained with anti-IPV 19S AB, except that one IPV strain was neutralized at a rate similar to the IBR strains. However, when early and late rabbit 7S AB were used, IBR strains could not be distinguished from IPV strains by neutralization kinetics. Preliminary experiments indicated that both early and late 19S rabbit antibodies neutralized the homologous strain more rapidly than the heterologous strain, but the difference was more noticeable with late 19S AB. It was also determined that neutralization of IBR-IPV virus by specific early and late 19S rabbit AB and early 7S rabbit AB was markedly enhanced by guinea pig complement. Neutralization of this virus by late 7S AB, however, was only slightly enhanced by complement. These results suggest that vaccine strains of IBR-IPV virus may be distinguished by neutralization kinetics with late 19S rabbit AB, and that genital and respiratory strains may possibly also be distinguishable with some 19S AB preparations. 相似文献
997.
Ethanol tolerance, a decrease in drug responsiveness with repeated administrations, is an important diagnostic criterion for alcoholism. Rapid tolerance develops within 8-24 hours of an initial ethanol exposure and shares many similarities with chronic tolerance. The genetic contribution to rapid tolerance to ethanol-induced ataxia was estimated using a panel of inbred strains of mice. Strains differed significantly in the degree of rapid tolerance development, which had a broad-sense heritability estimate of 0.11. Artificial selection was carried out to develop lines of mice that would show High (HRT) and Low (LRT) levels of Rapid Tolerance. Starting with HS/Npt mice, derived from a systematic cross of eight inbred strains, a significant response to selection was seen in replicate 1 by the third selection generation. No difference was found in replicate 2. Heritability estimates after the fourth generation were 0.25 for HRT-1 mice and 0.06 for LRT-1 mice. HRT-1 and LRT-1 mice also differed significantly in chronic tolerance development to four doses of ethanol. These studies provide evidence for a genetic contribution to rapid tolerance and support a genetic link between rapid and chronic tolerance to ethanol's ataxic effects. 相似文献
998.
Burchill MA Nardelli DT England DM DeCoster DJ Christopherson JA Callister SM Schell RF 《Infection and immunity》2003,71(6):3437-3442
We showed that Borrelia burgdorferi-vaccinated interferon gamma-deficient (IFN-gamma(0)) mice challenged with the Lyme spirochete developed a prominent chronic severe destructive osteoarthropathy. The immune response underlying the development of the severe destructive arthritis involves interleukin-17 (IL-17). Treatment of vaccinated IFN-gamma(0) mice challenged with B. burgdorferi with anti-IL-17 antibody delayed the onset of swelling of the hind paws but, more importantly, inhibited the development of arthritis. Histopathologic examination confirmed that treatment with anti-IL-17 antibody prevented the destructive arthropathy seen in vaccinated and challenged IFN-gamma(0) mice. Similar preventive results were obtained when vaccinated and challenged IFN-gamma(0) mice were treated with anti-IL-17 receptor antibody or sequentially with anti-IL-17 antibody followed by anti-IL-17 receptor antibody. By contrast, treatment of vaccinated and challenged IFN-gamma(0) mice with recombinant IL-17 (rIL-17) did not alter the development and progression of arthritis found in vaccinated and challenged IFN-gamma(0) mice without treatment with rIL-17. Therapeutic intervention may be a realistic approach to prevent arthritis, especially if IL-17 is involved in the perpetuation of chronic or intermittent arthritis. 相似文献
999.
Primitive Neuroectodermal Tumors of the Central Nervous System 总被引:2,自引:0,他引:2
Lucy Balian Rorke M.D. John Q. Trojanowski M.D. Ph.D. Virginia MY Lee Ph.D. Robert A. Zimmerman M.D. Leslie N. Sutton M.D. Jaclyn A. Biegel Ph.D. Joel W. Goldwein M.D. Roger J. Packer M.D. 《Brain pathology (Zurich, Switzerland)》1997,7(2):765-784
Controversial issues relating to the pathobiology and classification of central nervous system primitive neuroectodermal tumors (PNETs) have plagued neuropathologists for more than 70 years. Hypotheses advanced in the mid-1920's have remained as fixed concepts in contemporary literature, largely consequent to repetitious support by a small number of neuropathologists despite a growing body of information discrediting these ideas from neuroembryologists, oncologists, neuroscien-tists and pathologists.
Attention has largely focused upon PNETs arising in the cerebellum (commonly known as medul-loblastomas [MBs]), because about 80% of central nervous system (CNS) PNETs originate in this site. It has been asserted that the 20% which do not are biologically different, although most individuals agree that the histological features of PNETs that occur in different sites throughout the CNS are indistinguishable from those growing in the cerebellum.
The historical aspects of this controversy are examined in the face of evidence that there is, in fact, a unique class of CNS tumors which should appropriately be regarded as primitive neuroectodermal in nature. Specifically, a number of different approaches to the problem have yielded data supporting this hypothesis. These approaches include the identification of patterns of expression among a variety of cellular antigens (demonstrated by the use of immunopathological techniques), molecular analyses of cell lines derived from these tumors, experimental production of PNETs and molecular genetic analyses.
Differences of opinion among surgeons, oncologists and radiotherapists are typically resolved by conducting cooperative studies of patients with these tumors who are diagnosed and treated at multiple centers. 相似文献
Attention has largely focused upon PNETs arising in the cerebellum (commonly known as medul-loblastomas [MBs]), because about 80% of central nervous system (CNS) PNETs originate in this site. It has been asserted that the 20% which do not are biologically different, although most individuals agree that the histological features of PNETs that occur in different sites throughout the CNS are indistinguishable from those growing in the cerebellum.
The historical aspects of this controversy are examined in the face of evidence that there is, in fact, a unique class of CNS tumors which should appropriately be regarded as primitive neuroectodermal in nature. Specifically, a number of different approaches to the problem have yielded data supporting this hypothesis. These approaches include the identification of patterns of expression among a variety of cellular antigens (demonstrated by the use of immunopathological techniques), molecular analyses of cell lines derived from these tumors, experimental production of PNETs and molecular genetic analyses.
Differences of opinion among surgeons, oncologists and radiotherapists are typically resolved by conducting cooperative studies of patients with these tumors who are diagnosed and treated at multiple centers. 相似文献
1000.
Kevin D. Derman John A. Hawley Timothy D. Noakes Steven C. Dennis 《European journal of applied physiology》1996,74(1-2):36-43
On two occasions, six well-trained, male competitive triathletes performed, in random order, two experimental trials consisting of either a timed ride to exhaustion on a cycle ergometer or a run to exhaustion on a motor-driven treadmill at 80% of their respective peak cycling and peak running oxygen (VO2max) uptakes. At the start of exercise, subjects drank 250 ml of a 15 g·100 ml–1 w/v [U-14C]glucose solution and, thereafter, 150 ml of the same solution every 15 min. Despite identical metabolic rates [VO2 3.51 (0.06) vs 3.51 (0.10) 1·min–1; values are mean (SEM) for the cycling and running trials, respectively], exercise times to exhaustion were significantly longer during cycling than running [96 (14) vs 63 (11) min; P < 0.05]. The superior cycling than running endurance was not associated with any differences in either the rate of blood glucose oxidation [3.8 (0.1) vs 3.9 (0.4) mmol· min–1], or the rate of ingested glucose oxidation [2.0 (0.1) vs 1.7 (0.2) mmol· min–1] at the last common time point (40 min) before exhaustion, despite higher blood glucose concentrations at exhaustion during running than cycling [7.0 (0.9) vs 5.8 (0.5) mmol·1–1; P < 0.05]. However, the final rate of total carbohydrate (CHO) oxidation was significantly greater during cycling than running [24.0 (0.8) vs 21.7 (1.4) mmol C6·min–1; P < 0.01]. At exhaustion, the estimated contribution to energy production from muscle glycogen had declined to similar extents in both cycling and running [68 (3) vs 65 (5)%]. These differences between the rates of total CHO oxidation and blood glucose oxidation suggest that the direct and/or indirect (via lactate) oxidation of muscle glycogen was greater in cycling than running. 相似文献