全文获取类型
收费全文 | 1514篇 |
免费 | 137篇 |
国内免费 | 37篇 |
专业分类
耳鼻咽喉 | 11篇 |
儿科学 | 58篇 |
妇产科学 | 20篇 |
基础医学 | 130篇 |
口腔科学 | 37篇 |
临床医学 | 239篇 |
内科学 | 321篇 |
皮肤病学 | 13篇 |
神经病学 | 86篇 |
特种医学 | 172篇 |
外科学 | 288篇 |
综合类 | 40篇 |
预防医学 | 112篇 |
眼科学 | 9篇 |
药学 | 87篇 |
中国医学 | 1篇 |
肿瘤学 | 64篇 |
出版年
2021年 | 13篇 |
2020年 | 16篇 |
2019年 | 22篇 |
2018年 | 35篇 |
2017年 | 22篇 |
2016年 | 15篇 |
2015年 | 24篇 |
2014年 | 32篇 |
2013年 | 48篇 |
2012年 | 68篇 |
2011年 | 70篇 |
2010年 | 60篇 |
2009年 | 66篇 |
2008年 | 62篇 |
2007年 | 75篇 |
2006年 | 43篇 |
2005年 | 47篇 |
2004年 | 24篇 |
2003年 | 25篇 |
2002年 | 37篇 |
2001年 | 30篇 |
2000年 | 26篇 |
1999年 | 22篇 |
1998年 | 49篇 |
1997年 | 50篇 |
1996年 | 52篇 |
1995年 | 53篇 |
1994年 | 47篇 |
1993年 | 32篇 |
1991年 | 17篇 |
1990年 | 22篇 |
1989年 | 45篇 |
1988年 | 43篇 |
1987年 | 25篇 |
1986年 | 34篇 |
1985年 | 28篇 |
1984年 | 28篇 |
1983年 | 21篇 |
1982年 | 17篇 |
1981年 | 16篇 |
1980年 | 25篇 |
1979年 | 20篇 |
1978年 | 14篇 |
1977年 | 14篇 |
1976年 | 12篇 |
1975年 | 11篇 |
1974年 | 17篇 |
1973年 | 16篇 |
1972年 | 13篇 |
1969年 | 13篇 |
排序方式: 共有1688条查询结果,搜索用时 31 毫秒
1.
Martha A. Warpehoski Paul J. Buscemi David C. Osborn Birdwell Finlayson Eugene P. Goldberg 《Calcified tissue international》1981,33(1):211-222
Summary The quantity of protein and carbohydrate comprising the matrix of calcium oxalate monohydrate (COM) renal stones was found
to decrease with distance from the surface of the stone. The average organic concentration of stones 3 to 30 mm in diameter
ranged from 5.7% at the surface to 2.7% at the core. This concentration gradient suggests matrix involvement in a “growth
front” on stone surfaces with migration of organic material from the “older” interior. The matrix distribution was not readily
correlated with density variations or with the presence of hydroxyapatite or calcium oxalate dihydrate. Surface matrix concentrations
were greater than amounts predicted by physical adsorption. Electron microscopy confirmed the presence of the organic-rich
surface layer and also suggested that increase in stone size occurs predominantly by crystal growth with microcrystal aggregates
as growth centers. 相似文献
2.
3.
4.
Arianne C Lim Kitty WM Bloemenkamp Kees Boer Johannes J Duvekot Jan Jaap HM Erwich Tom HM Hasaart Pieter Hummel Ben WJ Mol Jos PM Offermans Charlotte M van Oirschot Job G Santema Hubertina CJ Scheepers Willem A Schöls Frank PHA Vandenbussche Maurice GAJ Wouters Hein W Bruinse 《BMC pregnancy and childbirth》2007,7(1):1-6
Background
Adequate vitamin D concentrations during pregnancy are necessary to neonatal calcium homeostasis, bone maturation and mineralization. The aim of study is to evaluate serum vitamin D concentrations in mothers and their newborns and effect of vitamin D deficiency on pregnancy outcomes.Methods
552 pregnant women were recruited from Tehran University educating hospitals in the winter of 2002. Maternal and cord blood samples were taken at delivery. The serum was assayed for 25-hydroxyvitamin D3, calcium, phosphorus and parathyroid hormone.Results
The prevalence of vitamin D deficiency in maternal and cord blood samples were 66.8% and 93.3%, respectively (<35 nmol/l). There was significant correlation between maternal and cord blood serum concentrations of vitamin D. In mothers with vitamin D deficiency, cord blood vitamin D concentrations was lower than those from normal mothers (P = .001). Also, a significant direct correlation was seen between maternal vitamin D intake and weight gain during pregnancy.Conclusion
Consideration to adequate calcium and vitamin D intake during pregnancy is essential. Furthermore, we think it is necessary to reconsider the recommendation for vitamin D supplementation for women during pregnancy. 相似文献5.
6.
Marcia Finlayson 《The American journal of occupational therapy》2004,58(1):54-63
Multiple sclerosis (MS) is a chronic, progressive neurological disease that causes demyelination of the central nervous system. Typically diagnosed in adulthood, it does not significantly reduce life expectancy. The goal of this exploratory study was to describe the health-related concerns and service needs of 27 older adults with MS, ages 55 to 81 years. Through in-depth interviews using a phenomenological approach, fear of the future was found to be a predominant concern among the participants. Within this fear, participants expressed particular concerns about experiencing further losses of mobility and independence, becoming a burden on caregivers, and having to move to a nursing home. The findings raise three major challenges for occupational therapists that include: (1) developing or modifying interventions that can enable older adults with MS to gain a sense of control over their future, (2) working with families affected by MS together with other disciplines such as psychology and social work, and (3) advocating for more and better community support options for persons with MS. 相似文献
7.
8.
9.
INVOLVEMENT OF NON-NMDA AND NMDA RECEPTORS IN GLUTAMATE-INDUCED PRESSOR OR DEPRESSOR RESPONSES OF THE PONS AND MEDULLA 总被引:1,自引:0,他引:1
SY Chen WC Wu CJ Tseng JS Kuo CY Chai 《Clinical and experimental pharmacology & physiology》1997,24(1):46-56
1. Fifty-five intact and six baroreceptor denervated and vagotomized cats of either sex were anaesthetized intraperito-neally with urethane (400 mg/kg) and a-chloralose (40 mg/kg). Responses of the systemic arterial pressure (SAP), mean SAP (MSAP) and sympathetic vertebral nerve (VNA) and renal nerve activities (RNA) were recorded. 2. In intact animals, monosodium L-glutamate (Glu, 0.1 mol/L, 50 nL) was microinjected into pressor areas of the locus coeruleus (LC), gigantocellular tegmental field (GTF), rostral ventrolateral medulla (RVLM) and dorsomedial medulla (DM), and the depressor areas of caudal ventrolateral medulla (CVLM). The induced actions were compared before and after microinjection of either glutamate antagonists, glutamate diethylester (GDEE, 0.5 mol/L, 50–100nL), a competitive AMPA receptor blocker, or 2-amino-5-phosphonovaleric acid (D-AP5, 0.025 mol/L, 50–100 nL), a competitive N-methyl-D-aspartate (NMDA) receptor blocker. GDEE completely blocked the increases of SAP and VNA elicited from all pressor areas. D-AP5 only partially blocked the pressor but slightly blocked VNA and RNA responses from LC, GTF and DM, particularly those from RVLM. Neither GDEE nor D-AP5 blocked the depressor responses of SAP and two nerve activities elicited from CVLM. 3. In baroreceptor denervated animals, NMDA (2 mmol/L, 50–100 nL) and AMPA (0.2 mmol/L, 50–100 nL) were micro-injected into the same pressor areas of GTF, RVLM and DM and the depressor area of CVLM responsive to Glu activation (0.1 mol/L, 30 nL). In RVLM, DM and CVLM, the results of either NMDA or AMPA were similar to those induced by Glu. However, in GTF, microinjection of either NMDA or AMPA did not induce similar responses to Glu. This suggests that the nature of GTF may differ from RVLM and DM. 4. The above results suggest that the Glu-induced pressor responses from LC, GTF, DM and especially RVLM, are primarily mediated through AMPA receptors. The Glu-induced depressor responses from CVLM may not be predominantly mediated by either AMPA or NMDA receptors. 5. In both baroreceptor-intact and -denervated cats stimulation of the pressor areas often produced an increase of VNA and a decrease of RNA, while in the depressor CVLM decreased both VNA and RNA. The VNA, but not RNA were positively correlated with the pressor responses, while both VNA and RNA were positively correlated with the depressor responses. This may suggest that neurons of the sympathetic vertebral and renal nerves are topographically organized in the brain. 相似文献
10.