全文获取类型
收费全文 | 1475篇 |
免费 | 108篇 |
国内免费 | 10篇 |
专业分类
耳鼻咽喉 | 37篇 |
儿科学 | 73篇 |
妇产科学 | 14篇 |
基础医学 | 150篇 |
口腔科学 | 31篇 |
临床医学 | 117篇 |
内科学 | 347篇 |
皮肤病学 | 23篇 |
神经病学 | 91篇 |
特种医学 | 245篇 |
外科学 | 122篇 |
综合类 | 59篇 |
预防医学 | 101篇 |
眼科学 | 20篇 |
药学 | 106篇 |
中国医学 | 9篇 |
肿瘤学 | 48篇 |
出版年
2022年 | 2篇 |
2021年 | 8篇 |
2020年 | 6篇 |
2019年 | 10篇 |
2018年 | 20篇 |
2017年 | 20篇 |
2016年 | 20篇 |
2015年 | 25篇 |
2014年 | 48篇 |
2013年 | 79篇 |
2012年 | 49篇 |
2011年 | 44篇 |
2010年 | 53篇 |
2009年 | 71篇 |
2008年 | 50篇 |
2007年 | 70篇 |
2006年 | 53篇 |
2005年 | 53篇 |
2004年 | 37篇 |
2003年 | 41篇 |
2002年 | 46篇 |
2001年 | 30篇 |
2000年 | 27篇 |
1999年 | 34篇 |
1998年 | 87篇 |
1997年 | 56篇 |
1996年 | 66篇 |
1995年 | 48篇 |
1994年 | 53篇 |
1993年 | 53篇 |
1992年 | 17篇 |
1991年 | 14篇 |
1990年 | 13篇 |
1989年 | 44篇 |
1988年 | 32篇 |
1987年 | 35篇 |
1986年 | 20篇 |
1985年 | 13篇 |
1984年 | 17篇 |
1983年 | 17篇 |
1982年 | 17篇 |
1981年 | 20篇 |
1980年 | 15篇 |
1979年 | 10篇 |
1978年 | 9篇 |
1977年 | 16篇 |
1976年 | 8篇 |
1975年 | 11篇 |
1973年 | 2篇 |
1942年 | 1篇 |
排序方式: 共有1593条查询结果,搜索用时 0 毫秒
991.
DA Sanghvi CA Sanghvi NC Purandare 《Journal of Medical Imaging and Radiation Oncology》2005,49(1):72-74
We report a case of bilateral persistent hyperplastic primary vitreous (PHPV) in a 5-month-old infant who presented with bilateral leukokoria. The child was referred for occular ultrasound with a clinical suspicion of retinoblastoma. Grey-scale evaluation revealed an echogenic band in the posterior segment of the left globe extending from the posterior surface of the lens capsule to the optic disc. Doppler examination revealed the presence of blood flow in the band. Ultrasound assessment of the contralateral globe showed an elevated mass of echogenic tissue in the posterior segment, in contact with the optic disc. Most cases of PHPV are sporadic and unilateral. Bilateral PHPV is rare. In a study by Pollard of 83 cases, only two patients (2.4%) had bilateral PHPV. The imaging features in this case point toward the diagnosis of bilateral PHPV. We suggest that this entity, although rare, should be considered in the differential diagnosis while evaluating bilateral leukokoria. 相似文献
992.
壳聚糖-5-氟尿嘧啶前药的合成与释放性研究 总被引:6,自引:0,他引:6
目的:合成5-氟尿嘧啶(5FU)的壳聚糖大分子前药,并评价其定量方法。方法:将5FU与壳聚糖通过氯乙酸连接,合成5FU大分子前药,并通过红外分光光度法、差示扫描量热法及氧瓶燃烧法分别进行了定性和定量分析。结果:合成的5FU大分子前药中5FU的含量约为28%(文献值为7%~27%),并在人工体液中缓慢释放出5FU。采用的氧瓶燃烧法定量结果准确可靠。结论:该合成方法与文献相比,工艺简化,成本低廉。 相似文献
993.
探讨鸟氨酸α酮戊二酸对负荷肝细胞瘤Morris7777大鼠的作用。大鼠分别接受等氮、热卡的含鸟氨酸α酮戊二酸或甘氨酸的饲料。鸟氨酸α酮戊二酸已用于其它一些分解代谢状态(如创伤、败血症)。肿瘤植入自然生长3周后达11g/(100g体重),此时可以引起进行性的厌食、负氮平衡以及机体和组织的消耗。与甘氨酸比较,鸟氨酸α酮戊二酸既没有影响肿瘤的生长也没有改变肿瘤引起的宿主分解代谢变化。认为本研究以及当肿瘤占宿主体重4%~30%的报告中,强化营养支持效果欠佳的原因是由于肿瘤夺取了宿主的氨基酸。本实验证明肿瘤植入3周后,肿瘤自身的蛋白积累和对氨基酸氧化分解占宿主每日摄入蛋白量的~70%。由于临床工作中肿瘤总是在较小时被诊断并行初次治疗的。本实验进一步研究了手术切除肿瘤以限制疾病阶段后强化营养的作用。大鼠术前3天和术后3天或6天分别接受鸟氨酸α酮戊二酸或甘氨酸的饲料。鸟氨酸α酮戊二酸强化营养的大鼠其氮平衡、肌肉谷氨酰胺和支链氨基酸浓度、小肠蛋白积累高于甘氨酸强化营养的大鼠(P<0.05)。本实验证明不切除肿瘤仅行营养支持其效果欠佳,而且为进一步实验研究建立了恰当的动物模型。 相似文献
994.
995.
Effect of training on the aerobic power and anaerobic performance of prepubertal girls 总被引:2,自引:0,他引:2
The purpose of this study was to investigate the effects of two, three times a week, 8-week training programmes on the aerobic power and anaerobic performance of 30 prepubescent girls, with a mean age of 9.6 y. Peak oxygen uptake assessed by an incremental discontinuous treadmill test, and peak power in 5 s and mean power over 30 s estimated from a Wingate anaerobic test were used as the criterion measures. Twelve girls trained using a continuous cycle ergometer programme, 11 girls followed a sprint running programme and the control group consisted of 7 girls. Both training groups significantly (p < 0.05) increased their peak oxygen uptake and peak power in 5 s. However, the increases reported here are lower than those generally observed in adolescents following training. The control group demonstrated no significant ( p > 0.05) change in either variable. No significant ( p > 0.05) changes in mean power over 30 s were observed in any group. 相似文献
996.
Firing characteristics of deep layer neurons in prefrontal cortex in rats performing spatial working memory tasks 总被引:9,自引:5,他引:4
Single cells were recorded with 'tetrodes' in regions of the rat medial
prefrontal cortex, including those which are targets of hippocampal
afferents, while rats were performing three different behavioral tasks: (i)
an eight-arm radial maze, spatial working memory task, (ii) a figure-eight
track, delayed spatial alternation task, and (iii) a random food search
task in a square chamber. Among 187 recorded units, very few exhibited any
evidence of place-specific firing on any of the behavioral tasks, except to
the extent that different spatial locations were related to distinct phases
of the task. Furthermore, no prefrontal unit showed unambiguous spatially
dependent delay activity that might mediate working memory for spatial
locations. Rather, the cells exhibited diverse correlates that were
generally associated with the behavioral requirements of performing the
task. This included firing related to intertrial intervals, onset or end of
trials, selection of specific arms on the eight-arm radial maze, delay
periods, approach to or departure from goals, and selection of paths on the
figure-eight track. Although a small number of cells showed similar
behavioral correlates across tasks, the majority of cells showed no
consistent correlate when recorded across multiple tasks. Furthermore, some
units did not exhibit altered firing patterns in any of the three tasks,
while others showed changes in firing that were not consistently related to
specific behaviors or task components. These results are in agreement with
previous lesion and behavioral studies in rats that suggest a prefrontal
cortical role in encoding 'rules' (i.e. structural features) or behavioral
sequences within a task but not in encoding allocentric spatial
information. Given that the hippocampal projection to this cortical region
is capable of undergoing LTP, our data lead to the hypothesis that the role
of this projection is not to impose spatial representations upon prefrontal
activity, but to provide a mechanism for learning the spatial context in
which particular behaviors are appropriate.
相似文献
997.
The Emery-Dreifuss muscular dystrophy protein, emerin, is a nuclear membrane protein 总被引:13,自引:4,他引:9
A large fragment of emerin cDNA was prepared by PCR and expressed as a
recombinant protein in Escherichia coli. Using this as immunogen, we
prepared a panel of 12 monoclonal antibodies which recognise at least four
different epitopes on emerin in order to ensure that emerin can be
distinguished from non-specific cross-reacting proteins. All the mAbs
recognised a 34 kDa protein in all tissues tested, though minor emerin-
related bands were also detected in some tissues. Immunofluorescence
microscopy showed that emerin is located at the nuclear rim in all tissues
examined. A muscle biopsy from an Emery-Dreifuss muscular dystrophy (EMDM)
patient showed complete absence of emerin by both Western blotting and
immunohistochemistry, suggesting a simple diagnostic antibody test for EDMD
families. Biochemical fractionation of brain and liver tissues showed that
emerin was present in nuclei purified by centrifugation through 65% sucrose
and was absent from soluble fractions (post-100,000 g). From these results,
together with sequence and structural homologies between emerin,
thymopoietins and the nuclear lamina-associated protein, LAP2, we suggest
that emerin will prove to be one member of a family of inner nuclear
membrane proteins.
相似文献
998.
We demonstrate the use of a novel database approach to drive the process of quality improvement in patients admitted under DRG 209, major joint and limb reattachment procedures of lower extremity.
METHODS: (1) Using standardized mapping criteria contained in the Perspective Comparative Databasetm (PCD) provided by Premier, Inc., a peer group of 12 similar institutions were selected. (2) PCD provided standardized cost and usage comparative data, including resource consumption by ICD-9 at the departmental charge code level, attending physician mix by specialty, average charges, costs, length of stay age and gender ratios by ICD-9 code (all payer data including Medicare), readmission to DRG209 and to any DRG at 30,60, and 90 days, primary admitting and discharge mix. (3) A multidisciplinary CQI team was asked to focus improvement efforts on the departmental level costs and use the benchmark peer groups as a comparison.
RESULTS: Analysis of the ICD-9 group that impacted DRG 209 that included total knee replacements (ICD-9 81.54) and total hip replacement (ICD-9 81.51), which represented 80% of all evaluated patients. 70% of the patients were female, 70% were Medicare and 70% were between the ages of 60 and 89. The PCD comparative reports showed that nursing, physician, and resource utilization had dollar variances from 23% to 82%. This enables the team to analyze whether the higher costs were due to over-utilization of resources (test, doses, supplies, critical care nursing days, etc.) or to resources that were properly used but too expensive.
CONCLUSION: CQI processes driven by data produce rapid targeted improvement in clinical outcomes. This is only possible if the database provided is accepted by all participants. 相似文献
METHODS: (1) Using standardized mapping criteria contained in the Perspective Comparative Databasetm (PCD) provided by Premier, Inc., a peer group of 12 similar institutions were selected. (2) PCD provided standardized cost and usage comparative data, including resource consumption by ICD-9 at the departmental charge code level, attending physician mix by specialty, average charges, costs, length of stay age and gender ratios by ICD-9 code (all payer data including Medicare), readmission to DRG209 and to any DRG at 30,60, and 90 days, primary admitting and discharge mix. (3) A multidisciplinary CQI team was asked to focus improvement efforts on the departmental level costs and use the benchmark peer groups as a comparison.
RESULTS: Analysis of the ICD-9 group that impacted DRG 209 that included total knee replacements (ICD-9 81.54) and total hip replacement (ICD-9 81.51), which represented 80% of all evaluated patients. 70% of the patients were female, 70% were Medicare and 70% were between the ages of 60 and 89. The PCD comparative reports showed that nursing, physician, and resource utilization had dollar variances from 23% to 82%. This enables the team to analyze whether the higher costs were due to over-utilization of resources (test, doses, supplies, critical care nursing days, etc.) or to resources that were properly used but too expensive.
CONCLUSION: CQI processes driven by data produce rapid targeted improvement in clinical outcomes. This is only possible if the database provided is accepted by all participants. 相似文献
999.
1000.