全文获取类型
收费全文 | 1361432篇 |
免费 | 104272篇 |
国内免费 | 5562篇 |
专业分类
耳鼻咽喉 | 17159篇 |
儿科学 | 44036篇 |
妇产科学 | 36826篇 |
基础医学 | 201092篇 |
口腔科学 | 36399篇 |
临床医学 | 132650篇 |
内科学 | 262626篇 |
皮肤病学 | 26978篇 |
神经病学 | 113705篇 |
特种医学 | 49088篇 |
外国民族医学 | 379篇 |
外科学 | 187517篇 |
综合类 | 32501篇 |
现状与发展 | 5篇 |
一般理论 | 478篇 |
预防医学 | 116070篇 |
眼科学 | 30015篇 |
药学 | 101157篇 |
25篇 | |
中国医学 | 4223篇 |
肿瘤学 | 78337篇 |
出版年
2021年 | 12192篇 |
2019年 | 12511篇 |
2018年 | 17270篇 |
2017年 | 13142篇 |
2016年 | 14119篇 |
2015年 | 16333篇 |
2014年 | 22236篇 |
2013年 | 33402篇 |
2012年 | 46309篇 |
2011年 | 49010篇 |
2010年 | 28286篇 |
2009年 | 25938篇 |
2008年 | 44170篇 |
2007年 | 46535篇 |
2006年 | 46600篇 |
2005年 | 45041篇 |
2004年 | 42585篇 |
2003年 | 40385篇 |
2002年 | 39085篇 |
2001年 | 61427篇 |
2000年 | 63119篇 |
1999年 | 52892篇 |
1998年 | 14975篇 |
1997年 | 13601篇 |
1996年 | 13363篇 |
1995年 | 12719篇 |
1994年 | 11833篇 |
1993年 | 11066篇 |
1992年 | 41808篇 |
1991年 | 40980篇 |
1990年 | 39664篇 |
1989年 | 37547篇 |
1988年 | 34746篇 |
1987年 | 33827篇 |
1986年 | 32302篇 |
1985年 | 30752篇 |
1984年 | 23112篇 |
1983年 | 19634篇 |
1982年 | 11789篇 |
1979年 | 20861篇 |
1978年 | 14856篇 |
1977年 | 12108篇 |
1976年 | 11912篇 |
1975年 | 12140篇 |
1974年 | 14853篇 |
1973年 | 14514篇 |
1972年 | 13403篇 |
1971年 | 12443篇 |
1970年 | 11512篇 |
1969年 | 10442篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The authors describe an original application of real time transducers--initially intended for intracavitary sonography--in thoraco-abdominal scanning. The stic-form probe can be easily slipped under the patient. It is then possible to realize a scan with an upward beam. In the postero-anterior scan, the patient is placed in a supine position. He is motionless. We achieve a better visualization of the liquid collections, since their accumulation is declivious. The method allows a wider sonographic window for thoraco-abdominal and diaphragmatic investigation in sonography. 相似文献
992.
The livers of 26 adult males with acquired immune deficiency syndrome (AIDS) were reviewed. The occurrence of portal tracts with diminished lymphocytes, probably reflecting generalized exhaustion of the lymphoid system, was a characteristic morphologic change, and was found in all cases. Kupffer cell hyperplasia was also a frequent finding and probably reflected generalized infection(s). Punched-out clusters of foamy histiocytes filled with acid-fast bacilli, typical for infection with Mycobacterium avium intracellulare (MAC), were found in three patients. In addition, MAC was cultured from two livers without the foamy histiocytic changes. Chronic viral hepatitis (three cases) and deposition of polarizable materials (one case) in the liver might be related to unusual habits of patients with AIDS. In conclusion, livers from patients with AIDS disclosed several kinds of lesions reflecting underlying or associated conditions in AIDS, but these did not contribute to the cause of death in our patients. 相似文献
993.
Pure motor hemiplegia (PMH) is, in most cases, caused by a lacunar infarction. However, pure motor monoparesis (PMM), i.e., isolated motor involvement with spasticity in one limb, has drawn little attention. We studied prospectively 5 patients with PMM and found that it was always due to a mass lesion in the contralateral superficial cerebral hemisphere. Our observation suggests that PMM should not be regarded as simply a variant of PMH. 相似文献
994.
Lack of effect of the calcium antagonist isradipine on cyclosporine pharmacokinetics in renal transplant patients. 总被引:1,自引:0,他引:1
L Endresen S Bergan H Holdaas T Pran B Sinding-Larsen K J Berg 《Therapeutic drug monitoring》1991,13(6):490-495
Hypertension has emerged as a frequent side effect in transplant recipients on effective doses of cyclosporine (CsA). To control hypertension in renal transplant patients, calcium channel blockers have been used; some of these, however, have been shown to cause significant increases in CsA levels. These findings point out that possible interactions of each calcium antagonist with CsA deserve investigation. We performed an open, placebo-controlled study in 12 stable renal transplant recipients to determine whether short-term isradipine influences CsA pharmacokinetics. All patients had mild to moderate hypertension and received triple immunosuppressive therapy with CsA, azathioprine, and prednisolone. Throughout a 4-week period of isradipine treatment, blood CsA levels (specific and nonspecific monoclonal antibodies) remained stable. The mean trough specific level was 121 +/- 14 micrograms/L following placebo, compared to 120 +/- 14 micrograms/L during isradipine. Corresponding non-specific values were 465 +/- 68 and 474 +/- 63 micrograms/L. Also, values for Cmax, AUC, and t1/2 were not significantly changed following 4 weeks of isradipine. Mean arterial pressure was significantly reduced at the end of the study. This study implies that isradipine does not influence CsA metabolism. Further studies should be carried out to determine its long-term effects on CsA pharmacokinetics and renal function in transplanted patients. 相似文献
995.
Regulatory control of indoor Rn 总被引:2,自引:0,他引:2
Regulation of indoor Rn is explored in the context of cost-effectiveness of regulatory action. Evaluation of cost (i.e., mitigation expenses) and benefits (i.e., savings associated with medical expenses and lost productivity related to lung cancer) at various action levels indicate that regulatory programs would be economically inefficient and unreasonable if standards were established at or below the current EPA action guide (150 Bq m-3 or less). For the approximately 95% of U.S. homes with Rn levels near or below 150 Bq m-3, government programs should continue to focus on public information and consumer protection. For the small number of homes with high Rn levels, government programs should focus on identifying high risk homes and encouraging homeowners to reduce Rn levels. Because of the potential for substantial risk reduction, such efforts would be cost-effective in these homes. 相似文献
996.
Phosphogypsum is the by-product resulting from phosphoric acid or phosphate fertilizer production. The phosphate are used in these chemical processes contains the naturally occurring radioactive material U and all its subsequent decay products. During processing, the U generally remains in the phosphoric acid product, while the daughter, 226Ra, tends to be concentrated in the phosphogypsum. Phosphogypsum has physical properties that make it useful as a sub-base for roadways, parking lots, and similar construction. A radiological evaluation, to determine exposures to workers mixing this material with a stabilizing agent (portland cement), was performed at a South Louisiana phosphoric acid chemical plant. Measurements of the 226Ra content of the phosphogypsum showed an average of 1.1 +/- 0.3 Bq g-1 (0.7-1.7 Bq g-1). The average measured gross gamma exposure rate on the phosphogypsum pile corresponded to a dose equivalent rate of 0.368 +/- 0.006 mu Sv h-1 (0.32-0.42 mu Sv h-1). Radon daughter concentrations measured on top of the phosphogypsum pile ranged from 0.0006 to 0.001 working levels. An analysis of the airborne 226Ra concentrations showed only background levels. 相似文献
997.
A review of lacrimal drainage surgery 总被引:3,自引:0,他引:3
The advent of improved silicone intubation sets, increased understanding of lacrimal and nasal anatomy and physiology, and refinements in surgical instrumentation and technique have led to higher success rates in lacrimal surgery. Recent clinical studies, combined with new techniques in canalicular reconstruction, have helped identify which patients will benefit from surgical intervention and which techniques are indicated. Fortunately, this has greatly reduced the number of CDCRs necessary. 相似文献
998.
A López Bernal D J Hansell S Alexander A C Turnbull 《British journal of obstetrics and gynaecology》1987,94(11):1052-1058
The production of progesterone from pregnenolone, of cortisol from cortisone and of prostaglandin E (PGE) under basal and arachidonic acid-stimulated conditions was measured in cells dispersed from chorion and decidua. The cells were obtained after delivery from four groups of women: following spontaneous labour at term (38-42 weeks gestation), at elective caesarean section at term before the onset of labour, after induced labour at term, and after uncomplicated preterm (27-36 weeks) labour. Chorionic cells had a high progesterone output with relatively low cortisol and PGE production, whereas decidual cells had a high cortisol and PGE production rate. Free arachidonic acid stimulated PGE production in both decidual and chorionic cells. There were no significant differences in either steroid or PGE production among the four groups studied. These data suggest that steroid dehydrogenase activity in choriodecidual cells is not related to the mode of onset of labour and that the increased prostaglandin production in intrauterine tissues associated with parturition is due to enhanced availability of arachidonic acid. 相似文献
999.
Reactive oxygen species: a breath of life or death? 总被引:7,自引:0,他引:7
New insights into cancer cell-specific biological pathways are urgently needed to promote development of rationally targeted therapeutics. Reactive oxygen species (ROS) and their role in cancer cell response to growth factor signaling and hypoxia are emerging as verdant areas of exploration on the road to discovering cancer's Achilles heel. One of the distinguishing and near-universal hallmarks of cancer growth is hypoxia. Unregulated cellular proliferation leads to formation of cellular masses that extend beyond the resting vasculature, resulting in oxygen and nutrient deprivation. The resulting hypoxia triggers a number of critical adaptations that enable cancer cell survival, including apoptosis suppression, altered glucose metabolism, and an angiogenic phenotype. Ironically, recent investigations suggest that oxygen depletion stimulates mitochondria to elaborate increased ROS, with subsequent activation of signaling pathways, such as hypoxia inducible factor 1alpha, that promote cancer cell survival and tumor growth. Because mitochondria are key organelles involved in chemotherapy-induced apoptosis induction, the relationship between mitochondria, ROS signaling, and activation of survival pathways under hypoxic conditions has been the subject of increased study. Insights into mechanisms involved in ROS signaling may offer novel avenues to facilitate discovery of cancer-specific therapies. Preclinical and clinical evaluation of agents that modify ROS signaling in cancer offers a novel avenue for intervention. This review will cover recent work in ROS-mediated signaling in cancer cells and its potential as a target for developmental therapeutics. 相似文献
1000.
The amount of protein bound per 1 mL of the perfluorocarbon (PFC) emulsion depends on the emulsifier composition and the particle
size. A relationship between the amount of bound protein on the particle surface and the physicochemical parameters of the
PFC emulsion interaction with the blood serum, which indirectly characterize the surface properties of the PFC particles,
is established.
__________
Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 41, No. 12, pp. 40–43, December, 2007. 相似文献