全文获取类型
收费全文 | 132879篇 |
免费 | 8068篇 |
国内免费 | 1137篇 |
专业分类
耳鼻咽喉 | 2041篇 |
儿科学 | 2024篇 |
妇产科学 | 1983篇 |
基础医学 | 21199篇 |
口腔科学 | 3251篇 |
临床医学 | 12352篇 |
内科学 | 23729篇 |
皮肤病学 | 4256篇 |
神经病学 | 10697篇 |
特种医学 | 7573篇 |
外科学 | 17734篇 |
综合类 | 575篇 |
现状与发展 | 3篇 |
一般理论 | 29篇 |
预防医学 | 7214篇 |
眼科学 | 3333篇 |
药学 | 11944篇 |
中国医学 | 1506篇 |
肿瘤学 | 10641篇 |
出版年
2023年 | 934篇 |
2022年 | 2825篇 |
2021年 | 4571篇 |
2020年 | 2210篇 |
2019年 | 3107篇 |
2018年 | 3872篇 |
2017年 | 3111篇 |
2016年 | 4082篇 |
2015年 | 5692篇 |
2014年 | 6726篇 |
2013年 | 7873篇 |
2012年 | 11704篇 |
2011年 | 11257篇 |
2010年 | 6452篇 |
2009年 | 5542篇 |
2008年 | 7897篇 |
2007年 | 7505篇 |
2006年 | 6773篇 |
2005年 | 6307篇 |
2004年 | 5462篇 |
2003年 | 4757篇 |
2002年 | 4128篇 |
2001年 | 3165篇 |
2000年 | 2918篇 |
1999年 | 2262篇 |
1998年 | 957篇 |
1997年 | 707篇 |
1996年 | 547篇 |
1995年 | 486篇 |
1994年 | 415篇 |
1993年 | 358篇 |
1992年 | 793篇 |
1991年 | 749篇 |
1990年 | 686篇 |
1989年 | 589篇 |
1988年 | 508篇 |
1987年 | 501篇 |
1986年 | 379篇 |
1985年 | 415篇 |
1984年 | 298篇 |
1983年 | 239篇 |
1982年 | 146篇 |
1981年 | 184篇 |
1980年 | 145篇 |
1979年 | 250篇 |
1978年 | 192篇 |
1977年 | 138篇 |
1976年 | 150篇 |
1974年 | 164篇 |
1973年 | 144篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Epstein-Barr viral load as a marker of lymphoma in AIDS patients 总被引:5,自引:0,他引:5
Fan H Kim SC Chima CO Israel BF Lawless KM Eagan PA Elmore S Moore DT Schichman SA Swinnen LJ Gulley ML 《Journal of medical virology》2005,75(1):59-69
Epstein-Barr virus (EBV) is implicated in the pathogenesis of acquired immunodeficiency syndrome (AIDS) lymphoma, and viral DNA is present within the malignant cells in about half of affected patients. We examined the extent to which EBV viral load is elevated in the plasma of AIDS lymphoma patients compared to AIDS patients with opportunistic infections. Sixty-one AIDS patients were studied including 35 with lymphoma (24 non-Hodgkin, six Hodgkin, and five brain lymphoma) and 26 with various opportunistic infections. In situ hybridization revealed EBV encoded RNA (EBER) expression in the malignant cells of 17/28 AIDS lymphomas (61%). In 232 serial plasma samples from 35 lymphoma patients and in 128 samples from AIDS controls, EBV viral load was assayed by quantitative-polymerase chain reaction (Q-PCR) using a TaqMan probe targeting the BamH1W sequence. EBV was detected in plasma from all 17 EBER-positive AIDS lymphoma patients, with viral loads ranging from 34 to 1,500,000 copies per ml (median 3,210). Viral load usually fell rapidly upon initiation of lymphoma therapy and remained undetectable except in two patients with persistent tumor. In 11 AIDS patients, whose lymphoma lacked EBER expression, and in 26 control patients without lymphoma, levels of EBV in plasma were usually low or undetectable (range 0-1,995 and 0-2,409, median 0 and 0, respectively). There was no association between EBV viral load and human immunodeficiency virus (HIV) load or CD4 count. In conclusion, EBV viral load shows promise as a tool to assist in diagnosis and management of EBV-related lymphoma patients. 相似文献
992.
This cross‐sectional study identified variables associated with protease inhibitor (PI) non‐adherence in 179 patients taking anti‐retroviral therapy. Univariate analyses identified 11 variables associated with PI non‐adherence. Multiple logistic regression modelling identified three predictors of PI non‐adherence: low adherence self‐efficacy and seriousness of non‐adherence and HIV (p < .001), perceived absence of HIV associated illness (p < .01), and use of more than one type of recreational drug (p = .001). The model correctly classified 83.9% of the sample, offers psychologists insight into psychological barriers to treatment adherence to guide interventions for improving adherence, and supports a modified version of the reformulated health belief model. 相似文献
993.
The periodic oscillations of outward currents were studied in smooth muscle cells of the rabbit pulmonary artery. The combined stimuli of superfusion with 1 mM caffeine and depolarization of the membrane potential to 0 mV evoked periodic oscillations of outward currents with fairly uniform amplitudes and intervals. The oscillating outward currents induced by caffeine were dependent on intracellular Ca2+ concentration ([Ca2+]i) and had a reversal potential near to the equilibrium potential for K+. So the oscillating outward currents are carried by K+ through Ca2+-dependent K+ channels (I
K(Ca)), and may reflect the oscillations of [Ca2+]i. The oscillating outward currents were abolished, or their frequency reduced, by lowering external [Ca2+], Ca2+ channel blockers, or by 1 M ryanodine, indicating that: (1) there is a continuous influx of Ca2+ through the plasma membrane at a holding potential of 0 mV; (2) the periodic transient increases of [Ca2+]i are ascribed to the rhythmic release of Ca2+ from ryanodinesensitive intracellular store by the mechanism of Ca2+-induced Ca2+ release (CICR). On the basis of the above results, we simulated the oscillation of [Ca2+]i induced by caffeine, which is known to lower the threshold of CICR. The patterns of peak amplitude histograms of spontaneous transient outward currents (STOC) in the oscillating cells were different from those in non-oscillating cells. The amplitudes of STOC in the latter were more variable than those in the former. The oscillating outward currents were modulated by 1 M forskolin and 1 M sodium nitroprusside, but STOC were little affected. The above differences between STOC and oscillating outward currents suggest that the two currents are activated by the Ca2+ originating from different intracellular Ca2+ stores which are functionally heterogeneous. 相似文献
994.
Resistance of calves to Cryptosporidium parvum: effects of age and previous exposure. 总被引:2,自引:5,他引:2 下载免费PDF全文
Cryptosporidium parvum is a coccidian parasite that causes diarrheal disease in many vertebrate species, including young (less than or equal to 1 month old) calves. Older calves and adult cattle are resistant to infection. In this study, newborn calves were raised in isolation from C. parvum for 1 week to 3 months before experimental challenge with the parasite. Calves orally challenged with C. parvum at 1 week of age shed oocysts in their feces and had diarrhea after challenge exposure. When these calves were rechallenged at 1 and 3 months of age, they neither shed oocysts nor had diarrhea. There was no significant increase in the mean anticryptosporidium enzyme-linked immunosorbent assay serum antibody titer in these calves following any of the challenge exposures. Calves orally inoculated with C. parvum for the first time at 1 month of age shed oocysts, had diarrhea after challenge exposure, and were resistant to rechallenge at 3 months of age. These calves had a twofold increase in serum antibody titer after the first challenge and no increase after the second challenge. Calves orally inoculated with C. parvum for the first time at 3 months of age shed oocysts, and two of seven animals had diarrhea. These calves had a 10-fold increase in serum antibody to C. parvum after exposure. This study demonstrates that calves raised in isolation from C. parvum remain susceptible to challenge until at least 3 months of age. Furthermore, within this time period, initial exposure and recovery renders calves resistant to further challenge with the parasite. The data also suggest that exposure of young calves to C. parvum may inhibit the development of a serum antibody response to the parasite. 相似文献
995.
Roger P. Farrar S.Mehdi Rezazadeh Jim L. Morris Jo Ellen Dildy Kim Gnau Steven W. Leslie 《Neuroscience letters》1989,100(1-3):319-325
Several lines of experimental evidence support an association between altered Ca2+ regulation and aging. It has been supposed that free cytosolic Ca2+ concentrations ([Ca2+]i) may decrease or increase in aged animals. In this study, both resting and KCl-stimulated [Ca2+]i were measured in purified cortical synaptosomes from young (3 mo.), middle-aged (12 mo.), and old (24 mo.) Fischer 344 rats. Two additional groups of rats were included, one middle-aged and one old which were trained on a treadmill for 6 months prior to experimentation. The [Ca2+]i was determined using the fluorescent Ca2+ chelator fura-2. Net KCl-dependent changes (ΔK) in [Ca2+]i were determined by the difference between stimulatory (100 μM Ca2+/60 mM KCl) and resting (100 μM Ca2+/5 mM KCl buffer) conditions among the 3 age groups. Significant increases in [Ca2+]i were observed in each age group upon depolarization with 60 mM KCl. However, there were no significant age-dependent differences in either resting [Ca2+]i or KCl-stimulated [Ca2+]i. 相似文献
996.
Computed tomography (CT) immediately after double-contrast shoulder arthrography was taken in twenty-two young male patients with anterior shoulder instability including recurrent dislocation and subluxation. This recently developed technique called CT arthrography can provide significant information about patients with glenohumeral instability which is difficult to obtain by conventional arthrography. Information about glenoid labrum pathology is useful for proper management of the shoulder with instability. Lesions identified in this study include anterior labral defects (attenuation, tear, displacement), anterior capsular distension and/or detachment, Hill-Sachs lesion, anterior glenoid rim compression fracture, and fracture of scapula. This article describes the method used in CT arthrography of the glenohumeral joint, reviews the normal cross-sectional anatomy, and emphasizes the importance of the application of CT arthrography in the shoulder disorder with instability. CT arthrography of the glenohumeral joint is easy to perform, is accurate, and has lower radiation dose than arthrotomography. 相似文献
997.
Neonatal injection of BALB/c mice with antibodies specific for the idiotype of TEPC-15 myeloma protein (T15id), which is serologically identical to the major idiotype of anti-phosphorylcholine (PC) antibody, renders the recipients completely unresponsive to PC. C57BL/6, (BALB/c X C57BL/6)F1 and C.B20 mice, similarly treated with anti-T15id antibody, also displayed tolerance to PC although they were relatively more resistant (8-13%) than BALB/c mice (less than 2% control response). When anti-T15id antibody was injected into 15-day-old neonates, the resistance to the tolerance in C57BL/6 and C.B20 mice was much more apparent (up to 80% of the control response) in contrast to that in BALB/c mice, which was not significant. Adoptive transfer of spleen cells from idiotypically suppressed BALB/c mice into 20-day-old, normal C. B20 mice resulted in suppression of T15id but not in tolerance to PC, due to increased production of non-T15id-bearing anti-PC antibody. These results suggest that the ability of clonal compensation for T15id suppression is acquired during early life (2-10 days), under the influence of gene(s) associated or linked with the Igh. 相似文献
998.
999.
Moon EJ Lee JY Kim CK Cho BH 《Journal of biomedical materials research. Part B, Applied biomaterials》2005,73(2):338-346
Various dental restorative composite resins containing 2,2-bis-[4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propane (Bis-GMA) derivatives and spiro orthocarbonates (SOCs) were explored for minimizing the volumetric shrinkage that generally occurs during polymerization. Previous reports suggested mixing Bis-GMA with its derivative TMBis-GMA (2,2-bis[3,5-dimethyl-4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propane) to obtain a dental composite with low volumetric shrinkage. It was hypothesized that spiro orthocarbonates would expand volumetrically during polymerization, because of their sophisticated ring-opening reactions; therefore several of them were added to the mixture of Bis-GMA and TMBis-GMA to bring about further reductions in volumetric shrinkage. It was indeed possible to reduce the extent of volumetric shrinkage of dental composites containing SOCs, and to do so without compromising these resins' mechanical properties. 相似文献
1000.
Kim SN Rhee JH Song YH Park DY Hwang M Lee SL Kim JE Gim BS Yoon JH Kim YJ Kim-Ha J 《Neurobiology of aging》2005,26(7):1083-1091
Previous gene expression profiling studies in Drosophila have provided clues for understanding the aging process at the gene expression level. For a detailed understanding, studies of specific regions of the body are necessary. We therefore employed microarray analysis to examine gene expression changes in the Drosophila head during aging. Six hundred and eighty-four of the 5405 genes present in the microarray showed significant age-dependent changes as determined by significance analysis of microarray (SAM) (q < 0.05). The biological significance of the changes was analyzed using the gene annotations provided by the Gene Ontology Consortium. Major changes involved genes affecting energy metabolism (proton transport, energy pathways, oxidative phosphorylation) and neuronal function, especially responses to light. Genes involved in protein catabolism and several other metabolic processes also showed age-dependent changes. Most of the changes were reductions in gene expression and occurred before day 13 of adult life. After day 13, the age-dependent gene expression changes were relatively smaller than earlier life. Interestingly, the two biological processes of major gene expression changes are related to the two known environmental changes that increase life span in Drosophila: caloric restriction and light reduction. Our findings suggest that light signaling and energy metabolism may be important biological processes affected by aging and be interesting targets for the further investigation related to the longevity in Drosophila. 相似文献