全文获取类型
收费全文 | 3030篇 |
免费 | 257篇 |
国内免费 | 9篇 |
专业分类
耳鼻咽喉 | 20篇 |
儿科学 | 94篇 |
妇产科学 | 77篇 |
基础医学 | 523篇 |
口腔科学 | 81篇 |
临床医学 | 329篇 |
内科学 | 622篇 |
皮肤病学 | 28篇 |
神经病学 | 293篇 |
特种医学 | 55篇 |
外科学 | 249篇 |
综合类 | 16篇 |
一般理论 | 1篇 |
预防医学 | 328篇 |
眼科学 | 107篇 |
药学 | 251篇 |
中国医学 | 4篇 |
肿瘤学 | 218篇 |
出版年
2024年 | 10篇 |
2023年 | 33篇 |
2022年 | 81篇 |
2021年 | 135篇 |
2020年 | 66篇 |
2019年 | 102篇 |
2018年 | 105篇 |
2017年 | 76篇 |
2016年 | 80篇 |
2015年 | 85篇 |
2014年 | 107篇 |
2013年 | 147篇 |
2012年 | 210篇 |
2011年 | 209篇 |
2010年 | 109篇 |
2009年 | 91篇 |
2008年 | 159篇 |
2007年 | 178篇 |
2006年 | 163篇 |
2005年 | 153篇 |
2004年 | 140篇 |
2003年 | 121篇 |
2002年 | 122篇 |
2001年 | 50篇 |
2000年 | 25篇 |
1999年 | 47篇 |
1998年 | 27篇 |
1997年 | 28篇 |
1996年 | 22篇 |
1995年 | 21篇 |
1994年 | 20篇 |
1993年 | 14篇 |
1992年 | 26篇 |
1991年 | 21篇 |
1990年 | 18篇 |
1989年 | 20篇 |
1988年 | 21篇 |
1987年 | 20篇 |
1986年 | 23篇 |
1985年 | 15篇 |
1984年 | 12篇 |
1983年 | 9篇 |
1982年 | 22篇 |
1980年 | 8篇 |
1979年 | 20篇 |
1978年 | 8篇 |
1976年 | 13篇 |
1975年 | 10篇 |
1974年 | 12篇 |
1972年 | 14篇 |
排序方式: 共有3296条查询结果,搜索用时 15 毫秒
61.
Melatonin suppresses NO-induced apoptosis via induction of Bcl-2 expression in PGT-beta immortalized pineal cells 总被引:2,自引:0,他引:2
Yoo YM Yim SV Kim SS Jang HY Lea HZ Hwang GC Kim JW Kim SA Lee HJ Kim CJ Chung JH Leem KH 《Journal of pineal research》2002,33(3):146-150
In the present study, we investigated whether melatonin would prevent nitric oxide (NO)-induced apoptotic death of PGT-beta immortalized pineal cells. To examine the protective effect of melatonin, cytotoxicity assay, DNA fragmentation analysis, caspase-3 activity assay, and Western blotting for caspase-3 and poly(ADP-ribose) polymerase (PARP) were performed. Treatment of cells with S-nitroso-N-acetylpenicillamine (SNAP), an NO donor, was shown to induce apoptotic cell death in a dose-dependent manner, and pretreatment with melatonin (0.1 mm) attenuated the occurrence of NO-induced apoptotic cell death. DNA fragmentation in response to NO was also arrested by melatonin. Caspase-3 activity induced by NO was decreased with melatonin treatment. Furthermore, the active fragments of caspase-3 and PARP were almost completely absent following exposure to melatonin. To elucidate the protective mechanisms of action of melatonin, Western blot analyses for Bcl-2 expression and cytochrome c release were carried out. Pretreatment with melatonin (0.1 mm) induced the expression of Bcl-2 and suppressed the release of cytochrome c into the cytosol, thereby arresting NO-induced apoptotic cell death. These results suggest that the antiapoptotic effect of melatonin is associated with induction of Bcl-2 expression in PGT-beta cells, which in turn blocks caspase-3 activation and inhibits cytochrome c release into the cytosol. 相似文献
62.
Beverley M Essue Merel Kimman Nina Svenstrup Katharina Lindevig Kjoege Tracey Lea Laba Maree L Hackett Stephen Jan 《Bulletin of the World Health Organization》2015,93(2):102-112B
Objective
To determine the nature, scope and effectiveness of interventions to reduce the household economic burden of illness or injury.Methods
We systematically reviewed reports published on or before 31 January 2014 that we found in the CENTRAL, CINAHL, Econlit, Embase, MEDLINE, PreMEDLINE and PsycINFO databases. We extracted data from prospective controlled trials and assessed the risk of bias. We narratively synthesized evidence.Findings
Nine of the 4330 studies checked met our inclusion criteria – seven had evaluated changes to existing health-insurance programmes and two had evaluated different modes of delivering information. The only interventions found to reduce out-of-pocket expenditure significantly were those that eliminated or substantially reduced co-payments for a given patient population. However, the reductions only represented marginal changes in the total expenditures of patients. We found no studies that had been effective in addressing broader household economic impacts – such as catastrophic health expenditure – in the disease populations investigated.Conclusion
In general, interventions designed to reduce the complex household economic burden of illness and injury appear to have had little impact on household economies. We only found a few relevant studies using rigorous study designs that were conducted in defined patient populations. The studies were limited in the range of interventions tested and they evaluated only a narrow range of household economic outcomes. There is a need for method development to advance the measurement of the household economic consequences of illness and injury and facilitate the development of innovative interventions to supplement the strategies based on health insurance. 相似文献63.
James R Bell Antonia JA Raaijmakers Johannes V Janssens Lea MD Delbridge 《Clinical and experimental pharmacology & physiology》2015,42(12):1327-1332
Control of cardiomyocyte cytosolic Ca2+ levels is crucial in determining inotropic status and ischemia/reperfusion stress response. Responsive to fluctuations in cellular Ca2+, Ca2+/calmodulin‐dependent protein kinase II (CaMKII) is a serine/threonine kinase integral to the processes regulating cardiomyocyte Ca2+ channels/transporters. CaMKII is primarily expressed either in the δB or δC splice variant forms, which may mediate differential influences on cardiomyocyte function and pathological response mechanisms. Increases in myocyte Ca2+ levels promote the binding of a Ca2+/calmodulin complex to CaMKII, to activate the kinase. Activity is also maintained through a series of post‐translational modifications within a critical region of the regulatory domain of the protein. Recent data indicate that the post‐translational modification status of CaMKIIδB/δC variants may have an important influence on reperfusion outcomes. This study provided the first evidence that the specific type of CaMKII post‐translational modification has a role in determining target selectivity of downstream Ca2+ transporters. The study was also able to demonstrate that the phosphorylated form of CaMKII closely co‐localizes with CaMKIIδB in the nuclear/myofilament fraction, contrasting with a co‐enrichment of oxidized CaMKII in the membrane fraction with CaMKIIδC. It has also been possible to conclude that a hyper‐phosphorylation of CaMKII (Thr287) in reperfused hearts represents a hyper‐activation of the CaMKIIδB, which exerts anti‐arrhythmic actions through an enhanced capacity to selectively increase sarcoplasmic reticulum Ca2+ uptake and maintain cytosolic Ca2+ levels. This suggests that suppression of global CaMKIIδ may not be an efficacious approach to developing optimal pharmacological interventions for the vulnerable heart. 相似文献
64.
Background
Colorectal cancer (CRC) early detection improves health outcomes; screening programmes invest efforts in initiating invitations to target populations to be tested. Enhanced adherence is essential for reduction of morbidity and mortality. Participation rates in Israel are still relatively low.Objective
To explore lay views regarding the concept of receiving material incentives in exchange for enhanced adherence to CRC screening.Research design
Qualitative study. Between November 2009 and February 2010 six focus group discussions were carried out in two urban, middle and low socio‐economic status primary care clinics in a Northern city in Israel. Participants were eligible individuals for CRC screening, aged 50–68 (N = 24). Data analysis followed the principles of grounded theory, supported by qualitative software.Results
Participants found administering incentives in exchange for CRC screening inappropriate on rational and moral grounds. They valued their relations with the medical team and the health system more than the potential gain expected. Individuals eligible for CRC screening perceived themselves as responsible for their health, admitting difficulties in realizing this responsibility. Incentives were reported unsuitable for solving reported screening difficulties and a potential harm to the doctor–patient relationship.Conclusions
Focus group participants expressed an unconventional voice towards the use of material incentives. They pointed to the need for focused support of health behaviour change and valued their autonomy. While a proportion of the invitees in the target population see the importance of screening and appreciate the HMO''s initiative to invite them for testing, they also expressed their need for support from the HMO in realizing the recommended health behaviour. 相似文献65.
Michael M Havranek Matthias Vonmoos Christian P Müller Jessica R Büetiger Eve Tasiudi Lea M Hulka Katrin H Preller Rainald M?ssner Edna Grünblatt Erich Seifritz Boris B Quednow 《Neuropsychopharmacology》2015,40(13):2929-2937
Cocaine users consistently develop working memory (WM) impairments but the mediating molecular mechanisms are unknown so far. Recent evidence suggests that the serotonin (5-HT) system is altered by chronic cocaine use, while also being involved in WM processing. Thus, we investigated the effects of genetic variations impacting 5-HT activity and of peripheral 5-HT transporter (5-HTT) mRNA expression on WM performance in cocaine users and stimulant naive controls. Two hundred twenty participants (126 cocaine users, 94 controls) were assessed with visuospatial, spatial, and verbal WM tasks, genotyped for the length polymorphism in the promoter region of the 5-HTT (5-HTTLPR), the variable number of tandem repeats in the second intron of the 5-HTT (VNTR In2), two single-nucleotide polymorphisms (rs4570625 and rs1386497) in the tryptophan hydroxylase-2 (TPH2) gene and quantified for peripheral 5-HTT mRNA expression in whole-blood samples. Several significant gene × environment interactions between 5-HT genotypes and cocaine use on WM emerged: in cocaine users, the long/long (5-HTTLPR), 9+10/9+10 (VNTR In2) and C/C (TPH2 rs1386497) genotypes were risk alleles for WM impairments, whereas in healthy controls these polymorphisms were associated with improved WM performance. Analogously, high 5-HTT mRNA levels were associated with worse executive WM performance in cocaine users but with increased performance in controls. These gene × environment interactions suggest that the 5-HT system has an important role in the development of cognitive deficits in chronic cocaine users. Hence, pharmacological compounds targeting 5-HT neurotransmission might be promising for the treatment of cognitive deficits in cocaine dependence. 相似文献
66.
67.
Mak Lung-Yi Huang Qi Wong Danny Ka-Ho Stamm Luisa Cheung Ka-Shing Ko Kwan-Lung Yan Ran Ouyang Lea Fung James Seto Wai-Kay Yuen Man-Fung 《Journal of gastroenterology》2021,56(5):479-488
Journal of Gastroenterology - We aimed to assess whether residual hepatitis B virus (HBV) viraemia is associated with HCC development. This is a case–control study of 104 patients [52 HCC and... 相似文献
68.
D. Ogston A. G. H. Lea P. L anghorne S. B. Wilson † 《British journal of haematology》1985,60(4):705-713
Preliminary findings suggested that the inhibitory activity on fibrinolysis produced by most varieties of cider is due to their content of polyphenols. In particular, the inhibitory activity co-eluted with the brown coloration on gel filtration, was removed by adsorption with polyvinylpyrrolidine, and was greatly reduced in a type of cider with a low concentration of phenolic compounds. The individual polyphenols of apple juice and ciders were examined for their ability to inhibit tissue activator, urokinase and plasmin. Neither phloridzin nor chlorogenic acid had any inhibitory activity at concentrations of 500 micrograms/ml while epicatechin had only a slight inhibitory effect at this concentration. The procyanidin fractions were markedly inhibitory on urokinase-induced clot lysis, the amidolytic activity of plasmin and on the fibrinolytic activities of plasmin, urokinase and tissue activator on fibrin plates: inhibition was noted at concentrations as low as 0.25 micrograms/ml. The order of inhibition was polymer greater than oligomer greater than trimer greater than dimer. 相似文献
69.
Lea R Bancroft K Whorwell PJ 《European journal of gastroenterology & hepatology》2004,16(12):1269-1272
BACKGROUND AND OBJECTIVES: Both irritable bowel syndrome and some gynaecological diseases can give rise to lower abdominal pain, which may result in diagnostic confusion. Disorders such as endometriosis and chronic pelvic inflammatory disease can be diagnosed definitively only by laparoscopy, which is seldom undertaken in the gastroenterological setting. It was the aim of this study to compare the symptomatology of irritable bowel syndrome with that of laparoscopically confirmed chronic pelvic inflammatory disease and endometriosis. PATIENTS AND METHODS: A symptom questionnaire was administered to 50 women with irritable bowel syndrome and 51 gynaecological patients (30 patients with endometriosis, 21 patients with chronic pelvic inflammatory disease). As the symptoms of the two gynaecological conditions were so similar, the groups were combined for the purposes of comparison with irritable bowel syndrome. RESULTS: Patients with irritable bowel syndrome suffered significantly more upper abdominal pain, colicky pain and exacerbation of pain by food or stress. They also experienced more disturbance of bowel habit, distension and nausea. In contrast, the only gynaecological features that were more common in the gynaecological patients were intermenstrual bleeding, premenstrual exacerbation of pain and forniceal tenderness. CONCLUSION: The presence of gastrointestinal symptomatology, especially bowel dysfunction, in a woman with lower abdominal pain is suggestive of irritable bowel syndrome. However, the history may not be so helpful in detecting gynaecological disease. 相似文献
70.
R W Lea P J Sharp H Klandorf S Harvey I C Dunn D M Vowles 《The Journal of endocrinology》1986,108(3):385-391
Seasonal changes in concentrations of plasma LH, prolactin, thyroxine (T4), GH and corticosterone were measured in captive male ring doves exposed to natural lighting at latitude 56 degrees N. Plasma LH levels decreased steeply in autumn when the daylength fell below about 12.5 h but increased in November as the birds became short-day refractory. In comparison with plasma LH concentrations in a group of short-day refractory birds exposed to 6 h light/day from the winter solstice, plasma LH levels in birds exposed to natural lighting increased further in spring after the natural daylength reached about 12.5 h. There were no seasonal changes in plasma prolactin concentrations and plasma T4 concentrations were at their highest during December, January and February, the coldest months of the year. The seasonal fall in plasma LH levels in September was associated with a transitory increase in plasma T4, a transitory decrease in plasma corticosterone and a sustained increase in plasma GH. It is suggested that in the ring dove, short-day refractoriness develops rapidly in November to allow the bird to breed when the opportunity arises, during the winter and early spring. The annual breeding cycle is synchronized by a short-day induced regression of the reproductive system in the autumn, the primary function of which may be to enable the birds to meet the energy requirements for the annual moult. The changes in plasma T4, corticosterone and especially of GH at this time of year are probably concerned with the control of moult or the associated changes in energy requirements. 相似文献