全文获取类型
收费全文 | 513篇 |
免费 | 21篇 |
国内免费 | 34篇 |
专业分类
儿科学 | 42篇 |
妇产科学 | 4篇 |
基础医学 | 33篇 |
口腔科学 | 4篇 |
临床医学 | 39篇 |
内科学 | 137篇 |
皮肤病学 | 6篇 |
神经病学 | 11篇 |
特种医学 | 123篇 |
外科学 | 39篇 |
综合类 | 38篇 |
一般理论 | 2篇 |
预防医学 | 38篇 |
眼科学 | 4篇 |
药学 | 38篇 |
肿瘤学 | 10篇 |
出版年
2021年 | 4篇 |
2020年 | 5篇 |
2018年 | 5篇 |
2017年 | 4篇 |
2016年 | 6篇 |
2015年 | 6篇 |
2014年 | 10篇 |
2013年 | 15篇 |
2012年 | 18篇 |
2011年 | 9篇 |
2010年 | 6篇 |
2009年 | 16篇 |
2008年 | 17篇 |
2007年 | 40篇 |
2006年 | 8篇 |
2005年 | 12篇 |
2004年 | 11篇 |
2003年 | 13篇 |
2002年 | 13篇 |
2001年 | 18篇 |
2000年 | 22篇 |
1999年 | 13篇 |
1998年 | 30篇 |
1997年 | 24篇 |
1996年 | 15篇 |
1995年 | 23篇 |
1994年 | 29篇 |
1993年 | 15篇 |
1992年 | 10篇 |
1991年 | 13篇 |
1990年 | 9篇 |
1989年 | 14篇 |
1988年 | 15篇 |
1987年 | 16篇 |
1986年 | 13篇 |
1985年 | 17篇 |
1984年 | 10篇 |
1983年 | 2篇 |
1982年 | 9篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 2篇 |
排序方式: 共有568条查询结果,搜索用时 15 毫秒
51.
A previous report of elevated dual-energy X-ray absorptiometry (DXA) bone mineral density (BMD) Z scores suggests that Hutterite females might be significantly less likely to develop osteoporosis compared with other U.S. females. In the present study, we sought to determine if high Hutterite DXA BMD Z scores were elevated because of larger bone size. Hutterites reside in isolated, self-sufficient colonies with an emphasis on agricultural production, and girls enter a strenuous task rotation at age 15 years. We obtained cross-sectional bone measurements of the 66% distal tibia using peripheral quantitative computed tomography (pQCT) to compare bone size and geometry on 97 Hutterite and 30 non-Hutterite women, aged 35-60 years. Total body (TB) and lumbar bone mineral content (BMC), BMD, and bone area measurements by DXA were available on a subset of the study population. We identified no differences between groups in pQCT total bone area, cortical bone area, or cortical bone density. Larger bone area by DXA was apparent in Hutterites compared with non-Hutterites at the TB (least square means: 2038 +/- 8 cm2 vs. 1953 +/- 19 cm2, p < 0.05) and lumbar (least square means: 58 +/- 0.5 cm2 vs. 57 +/- 2 cm2, p < 0.01) sites. TB BMC adjusted for TB bone area was marginally higher in Hutterites compared with non-Hutterites (least square means: 2341 +/- 15 g vs. 2281 +/- 30 g, p = 0.08). Hutterites had marginally higher TB BMD Z scores when controlling for weight and age (least square means: 1.3 +/- 0.1 vs. 0.8 +/- 0.2, p = 0.07). Hutterites had higher lumbar BMC adjusted for lumbar bone area and weight (least square means: 65 +/- 1 g vs. 58 +/- 2 g, p < 0.01) and higher weight-and age-adjusted lumbar BMD Z scores (least square means: 1.1 +/- 0.1 vs. 0.1 +/- 0.4, p = 0.01). Our data indicate that a true advantage in trabecular bone density probably exists among Hutterite women aged 35-60 years. Hutterite women might be protected against age-related fractures because of their larger bone size and higher bone density at normally susceptible trabecular sites. 相似文献
52.
AA Lapillonne FH Glorieux BL Salle PM Braillon M Chambon J Rigo G Putet J Senterre 《Acta paediatrica (Oslo, Norway : 1992)》1994,83(S405):117-122
Fat and mineral metabolic balance studies were performed in 25 normal very low-birth-weight infants ( 1500 g at birth) fed either pooled pasteurized human milk supplemented with calcium, phosphorus and magnesium, or a preterm formula. Calcium, phosphorus and magnesium intake were similar in both groups and averaged 100mg/kg/day, 72 mg/kg/day and 8 mg/kg/day, respectively. Calcium and phosphorus retention was higher in the subjects fed fortified human milk than in those receiving a preterm formula (65±14 and 62±9mg/kg/day versus 55±12 and 47±7mg/kg/day respectively). The difference was only significant for phosphorus. Magnesium retention was similar in the two groups and averaged 3 mg/kg/day. Fat intake and absorption was significantly higher in the preterm formula fed group than in the one fed fortified human milk (5.5±0.4 g/kg/day and 88±4% versus 4.2±1 g/kg/day, 79±6% respectively). Assessment of the whole body bone mineral content by dual energy X-ray absorptiometry was performed at 3 and 6 months of age in another group of 25 low-birth-weight infants fed either fortified human milk or a preterm formula. Whole body bone mineral content (BMCt) was low (43.3±30.8 g of hydroxyapatite) at 3 months of age (theoretical term) compared to normal full-term newborns at birth. There was no significant influence of the diet. At 6 months of age, BMCt reached 168.6±36.6g, a value similar to that of full-term newborns, with no significant difference between the two regimen groups. The deficit in the 12 subjects who had a BMCt under 30 g at 3 months of age had been corrected at age 6 months. Premature babies fed a pooled pasteurized human milk enriched with calcium, phosphorus and magnesium favored a better retention of calcium and phosphorus. However, no significant influence of the two diets studied was observed on the gain in BMCt over the first 6 months of life. 相似文献
53.
Cortisol is necessary for seawater tolerance in larvae of a marine teleost the summer flounder 总被引:1,自引:0,他引:1
Veillette PA Merino M Marcaccio ND Garcia MM Specker JL 《General and comparative endocrinology》2007,151(1):116-121
Larval-stage summer flounder (Paralichthys dentatus) were immersed in the corticosteroid-receptor blocker RU486 to test the effects of cortisol deficiency on salinity tolerance. Premetamorphic larvae held at 10 (near isosmotic) or 30 (hyperosmotic) parts per thousand ( per thousand) seawater survived well over 5d in 0, 0.012, or 0.12 microM RU486. However, at concentrations of 1.2 or 3.6 microM RU486, mortality was significantly greater for larvae in 30 per thousand compared to larvae in 10 per thousand. In a separate experiment, the ability of RU486 to inhibit tolerance to hyperosmotic medium (30 per thousand) was confirmed; immersion at 1.2 microM RU486 induced mortality of larvae in the metamorphic climax stage held at 30 per thousand, but not 0 or 10 per thousand. Mortality due to RU486 in pre- or prometamorphic stage larvae was prevented by concurrent immersion in cortisol at concentrations approximately 10-200 times greater than RU486, indicating that the action of RU486 was specific to antagonism of cortisol. The efficacy of 1.2 microM RU486 in reducing survival in 30 per thousand was found to be stage-dependent and exhibited the following hierarchy for fastest time to 50% mortality: prometamorphosis>metamorphic climax>premetamorphosis. In a 5-d pretreatment of pre- or prometamorphic larvae by immersion in 20 microM cortisol and/or 0.12 microM RU486 at 30 per thousand, only RU486 had a limited effect on decreasing survival when larvae were challenged with abrupt exposure to 50 per thousand. In total, the results evidence for the first time a necessary role for cortisol in seawater tolerance of a larval marine teleost. 相似文献
54.
Angiogenic factors stimulate mast-cell migration 总被引:18,自引:1,他引:18
Mast cells accumulate at sites of angiogenesis. The factor(s) that control mast-cell recruitment at these sites have yet to be defined. We sought to determine if angiogenic factors result in mast-cell chemotaxis. In this study, we observed that platelet-derived growth factor-AB (PDGF-AB), vascular endothelial cell growth factor (VEGF), and basic fibroblast growth factor (bFGF) each cause directed migration of murine mast cells at picomolar concentrations, with a typical bell- shaped dose-response curve. Another potent angiogenic factor, platelet- derived endothelial cell growth factor (PD-ECGF), appears to promote chemokinesis of mast cells, whereas tumor necrosis factor-alpha, a weak angiogenic factor, is less robust but still functions as a mast cell chemotactic factor. Epidermal growth factor (EGF), a growth factor with minimal angiogenic properties, was ineffective as a mast cell chemotactic factor. A checkerboard analysis confirmed the directional chemotactic response of PDGF-AB, VEGF, and bFGF, while indicating the chemokinetic response induced by PD-ECGF. Cross-desensitization of growth-factor-induced directed migration was observed between PDGF-AB and bFGF, and also between PDGF-AB and PD-ECGF. Tyrosine kinase- inhibitor genistein effectively dampened the chemotactic responses, whereas pertussis toxin had no effect. In summary, our findings suggest that factors known to act on endothelial cells and stimulate neovascularization may simultaneously serve to recruit mast cells to these sites. The local accumulation of mast cells is believed to facilitate new vessel formation through complex cell:cell interactions. 相似文献
55.
C. Specker S. Bläß C. Meier H.-J. Lakomek M. Schwochau M. Schneider 《Zeitschrift für Rheumatologie》1997,56(2):63-70
Zusammenfassung Die Diagnostik vieler rheumatischer Systemerkrankungen wird heute durch den Nachweis von Autoantik?rpern unterstützt und
erleichtert. Für die Serodiagnostik der Rheumatoiden Arthritis (RA) stehen nur die doch wenig spezifischen Rheumafaktoren
zur Verfügung. Mit dem Ziel, neue krankheitsspezifische Autoantik?rper nachzuweisen, erfolgte eine besondere Proteinaufarbeitung
aus Synovialisbiopsien und anderen Geweben. Western Blots der gewonnenen Proteine wurden eingesetzt, um Seren von RA-Patienten
und solchen mit anderen rheumatischen Erkrankungen zu untersuchen. Die signifikanteste Immunreaktion von RA-Patienten richtete
sich gegen ein 68k-Antigen, welches vermutlich ubiquit?r exprimiert wird, da es nicht nur in Synovialis, sondern in allen
weiteren untersuchten Humangeweben und HeLa-Zellen nachgewiesen werden konnte. Der isoelektrische Punkt liegt bei 5,1, das
Protein ist O-glykosyliert und im endoplasmatischen Retikulum und/oder Cytoplasma lokalisiert. Antik?rper gegen dieses 68k-Antigen
waren bei 110 von 167 RA-Patienten nachzuweisen, was einer Sensitivit?t von 66% entspricht. Ihr Vorkommen war unabh?ngig vom
Rheumafaktornachweis, da sie auch bei 7 von 12 seronegativen RA-Patienten zu finden waren, dagegen nur bei einem Patienten
aus einer Kontrollgruppe von 98 Patienten mit anderen rheumatologischen Krankheitsbildern, bei einem von 22 HIV-Patienten
und überhaupt nicht bei 55 Gesunden. Daraus resultiert eine RA-Spezifit?t für diesen Antik?rper von 99%. Wegen der auff?lligen
Krankheitsspezifit?t der anti-68k-Antik?rper liegt es nahe, nach korrespondierenden autoreaktiven T-Zellen zu suchen, um
die Rolle dieser neuen Autoreaktivit?t in dem Pathomechanismus der RA zu analysieren.
Eingegangen: 20. Mai 1996 Akzeptiert: 13. Februar 1997 相似文献
56.
G. Riemekasten M. Aringer C. G. O. Baerwald A. Meyer-Bahlburg R. Bergner M. Feuchtenberger C. Gebhardt B. Hellmich G. Keyßer H.-M. Lorenz C. Kneitz T. Witte U. Müller-Ladner M. Schneider J. Braun J. Rautenstrauch C. Specker H. Schulze-Koops 《Zeitschrift für Rheumatologie》2016,75(5):493-501
The German Society of Rheumatology and the Committee for Student Training investigated what effects the structures in university medicine have on student teaching. In February 2014 a questionnaire was sent to the teaching staff and Deans of each of the 37 medical faculties. Of the locations seven were classified as being independent rheumatological university hospitals and nine universities had a W2/W3/C3 grade professor as head of a department of clinical rheumatology but answerable to superiors. In the 37 faculties in Germany the proportion of lecture hours, the proportion of obligatory lecture hours, the number of hours for practical exercises and the number of hours for bedside teaching were distributed very differently and as a rule higher in universities with academic freedom. Not all medical faculties have obligatory teaching in the field of clinical rheumatology. On average medical students see five patients with rheumatological symptoms during their studies. In summary, over the past years it has not been possible to successfully utilize the great importance of rheumatology for society and the innovation potential of this discipline in order to improve the integration of clinical rheumatology into universities. 相似文献
57.
Metamorphosis in the summer flounder (Paralichthys dentatus) is mediated by thyroid hormones (TH) and is accompanied by changes in gill mitochondria-rich cells (MRCs) and in salinity tolerance. Altered thyroid status during larval development and metamorphosis in this species influences salinity tolerance, though the influence of any hormone on MRCs of larval marine teleosts is not known. This study characterized the effect of altered thyroid status on MRC intracellular membranes, mitochondria size and ultrastructure, immunoreactive (ir)-Na(+),K(+)-ATPase, and cell size and density during metamorphosis in summer flounder. Inhibition of metamorphosis with thiourea (30 ppm) (TU, an inhibitor of TH synthesis) inhibited changes in MRCs, producing large "larval" type MRCs with weak reactivity to osmium; large, electron-lucent mitochondria; and weak ir-Na(+),K(+)-ATPase. Replacement of TH with TU + thyroxine-Na salt (100 ppb) rescued the fish from developmental inhibition, producing smaller "juvenile" type MRCs with strong reactivity to osmium; smaller, electron-opaque mitochondria; and strong ir-Na(+), K(+)-ATPase. The findings suggest that TH are necessary for MRCs to change from larval to juvenile form during metamorphosis. 相似文献
58.
The objective of this study is to ascertain whether the course and severity of Substance Abuse among female patients with comorbid Substance Related Disorder and Eating Disorder (SRD-ED) is similar to or different from the course and severity of SRD among female patients with Substance Related Disorder but no Eating Disorder (SRD). Subjects were voluntary patients, obtained in two addiction programs located within departments of psychiatry in two state university medical centers, and included 66 women with SRD-ED and 211 women with SRD. Data were collected on demography, course and severity of SRD, and associated biomedical conditions. SRD-ED patients were significantly younger and more apt to be single, more highly educated, living with family and friends, employed, and of higher socioeconomic status. SRD-ED and SRD patients were more similar than different on most indicators of course and severity, although several clinical differences prevailed. These clinical differences were primarily ascribed to age. In most respects, patients with comorbid SRD-ED manifest course and severity of SRD similar to patients with SRD. Demographic differences between the two groups can mostly be ascribed to the younger mean age of SRD-ED patients rather than to the comorbid ED. Some biomedical problems are related to the specific consequences of ED. 相似文献
59.
60.
PURPOSE: This study assessed the accuracy with which a rural population reported daily walking distances using a 7-day activity recall questionnaire obtained quarterly compared to pedometer readings. METHODS: Study participants were 48 Hutterite men and women aged 11-66 years. FINDINGS: Pedometer-miles quartiles were associated with self-reported daily miles (P=.008) and self-reported previous-year average miles (P=.03) quartiles. Among males, the relationship between pedometer-miles and self-reported daily miles differed depending upon walking pace, with a stronger correlation at a faster pace (interaction, P=.006). Among females, pedometer-miles correlated with age and remained associated with self-reported daily and previous-year average miles when age was in the statistical model (P=.006 and .008). The difference between pedometer-miles and self-reported previous-year average miles tended to increase with age (P=.06). CONCLUSIONS: SDPAR may be a useful instrument in measuring miles walked/day among rural populations. 相似文献