全文获取类型
收费全文 | 4376篇 |
免费 | 396篇 |
国内免费 | 7篇 |
专业分类
耳鼻咽喉 | 57篇 |
儿科学 | 77篇 |
妇产科学 | 110篇 |
基础医学 | 580篇 |
口腔科学 | 74篇 |
临床医学 | 666篇 |
内科学 | 784篇 |
皮肤病学 | 28篇 |
神经病学 | 482篇 |
特种医学 | 120篇 |
外科学 | 627篇 |
综合类 | 83篇 |
一般理论 | 1篇 |
预防医学 | 523篇 |
眼科学 | 56篇 |
药学 | 359篇 |
中国医学 | 4篇 |
肿瘤学 | 148篇 |
出版年
2021年 | 65篇 |
2020年 | 45篇 |
2019年 | 62篇 |
2018年 | 70篇 |
2017年 | 65篇 |
2016年 | 56篇 |
2015年 | 65篇 |
2014年 | 90篇 |
2013年 | 127篇 |
2012年 | 195篇 |
2011年 | 186篇 |
2010年 | 99篇 |
2009年 | 86篇 |
2008年 | 164篇 |
2007年 | 207篇 |
2006年 | 197篇 |
2005年 | 173篇 |
2004年 | 172篇 |
2003年 | 171篇 |
2002年 | 155篇 |
2001年 | 128篇 |
2000年 | 132篇 |
1999年 | 106篇 |
1998年 | 51篇 |
1997年 | 39篇 |
1996年 | 38篇 |
1995年 | 50篇 |
1994年 | 41篇 |
1993年 | 47篇 |
1992年 | 87篇 |
1991年 | 95篇 |
1990年 | 103篇 |
1989年 | 118篇 |
1988年 | 118篇 |
1987年 | 89篇 |
1986年 | 95篇 |
1985年 | 107篇 |
1984年 | 77篇 |
1983年 | 77篇 |
1982年 | 45篇 |
1981年 | 39篇 |
1980年 | 49篇 |
1979年 | 66篇 |
1978年 | 48篇 |
1977年 | 51篇 |
1976年 | 47篇 |
1975年 | 46篇 |
1974年 | 57篇 |
1973年 | 47篇 |
1972年 | 30篇 |
排序方式: 共有4779条查询结果,搜索用时 15 毫秒
1.
Aim : The study was designed to determine the effect of computerized nutrition information on consumer food choice in two workplace restaurants, one in which customers had to pay for their lunch and the other providing a free lunch. Methods : Customers entering the restaurants were asked to make selections from the menu on a computer screen. The energy, saturated fatty acids, non-milk extrinsic sugars and non-starch polysaccharide content of the meal selected was displayed graphically in proportion to the dietary reference values. They were given the opportunity to change their selected meal and the composition of all meals was recorded. Results : The nutritional composition of the first meal provoked 16% of customers to make a second selection. The proportion of energy in the first selection had been 31% higher for saturated fatty acids and 23% higher for non-milk extrinsic sugars than the first selection made by people who were satisfied with their first choice. In their second attempt they succeeded in reducing both nutrients to levels similar to those present in the meals selected by people who had been satisfied with their first selection. Customers>> selections for non-starch polysaccharide and energy did not differ between the groups. The main changes made by customers to achieve improved second choices were to omit dishes (44%), add dishes (19%), make changes within a menu category (46%), and make changes from one menu category to another (26%). Conclusion : It was concluded that provision of graphical nutrition information on a computer screen could be used by a subset of the users of both restaurants to enable them to improve their menu selections to a similar composition to that selected by the other people who used the computer system. 相似文献
2.
Nerve growth factor (NGF) and NGF receptors were measured in cortex and hippocampus of rats treated with drugs affecting cholinergic neurotransmission. High (Kd= 0.045nM) and low (Kd= 21nM) affinity125I-NGF binding sites were present in both cortical and hippocampal membranes with hippocampus containing higher numbers of both sites than cortex. Chronic treatment of rats with the muscarinic receptor antagonist scopolamine (5 mg/kg, twice daily) decreased the density of high- and low-affinity sites by 50–90% in cortical and hippocampal membranes. These changes were seen after 7 days, but not 3 days, of scopolamine treatment. Chronic infusion of physostigmine (1 mg/kg/day) using minipumps increased the number of high- and low-affinity sites in cortex 3- and 6-fold, respectively. The changes in receptor-binding parameters induced by physostigmine were transient as they were evident after 3 days of treatment, but returned to control levels after 7 days. NGF content in cortex and hippocampus was reduced by about 50% following 7, but not 3, days of chronic physostigmine infusion. In contrast, scopolamine treatment failed to change NGF levels in the cholinergic neuronal target regions but it decreased NGF content in the septal area. The content of NGF mRNA in the cortex measured by Northern blot analysis failed to change following either scopolamine or physostigmine treatment. The results suggest that levels of NGF and NGF receptors in the target regions of cholinergic neurons are regulated by the extent of cholinergic neurotransmitter activity. 相似文献
3.
M G Wise 《Health & social work》1986,11(1):36-41
The vastly increased use of prescribed and nonprescribed drugs in this society means that even such traditional social work activities as assessment and advocacy now frequently require a knowledge of the effects of drugs. Integrating a knowledge of basic concepts of pharmacology into practice will enable the social worker to help clients more effectively and to improve the health care they receive. 相似文献
4.
Patients with hyperparathyroidism appear to be a particular risk for peptic ulcer disease. To test the hypothesis that hypercalcemia or parathyroid hormone plays a role in promoting ulcer disease, we studied the effect of varying concentrations of extracellular calcium on acid secretion using in vitro isolated rabbit gastric glands. Acid secretion was assessed by the accumulation of carbon 14-labeled aminopyrine (14C-AP). Glands were incubated with varying calcium concentrations in the unstimulated state and with histamine or carbachol (10(-7) to 10(-4) mol/L) in 1 or 2 mmol/L calcium medium. The effect of parathyroid hormone was also examined under identical conditions. Compared to 1 mmol/L standard calcium medium, unstimulated 14C-AP accumulation was significantly inhibited (p less than 0.05) at both lower (0.33 mmol/L) and higher (2 and 2.5 mmol/L) calcium concentrations. Accumulation of 14C-AP in response to histamine stimulation was unaffected by alteration of extracellular calcium (p greater than 0.2). Carbachol-stimulated 14C-AP accumulation was significantly augmented (p less than 0.01) by an increase in calcium concentration from 1 to 2 mmol/L. The addition of parathyroid hormone (10(-7) to 10(-4) mmol/L) alone or in combination with carbachol or histamine (10(-6) mmol/L) incubation did not alter 14C-AP accumulation. These data suggest that elevations in extracellular calcium play an active role in the potentiation of cholinergic-mediated gastric gland acid secretion and may thereby play a role in hyperparathyroid-related ulcer disease. 相似文献
5.
Diagnosis Related Group (DRG) hospital payment has begun to squeeze hospitals financially and is likely to do so in the future. This study analyzed the relationship between the volume of urologic procedures by an individual urologist, hospital costs per patient, and outcome. We used a three-year DRG database of urology patients (N = 2,980) at an academic medical center to analyze these. Low-volume urologists (arbitrarily defined by us) had higher hospital costs per patient, financial losses versus profits under DRGs, and a poorer outcome when compared with high-volume urologists. Pearson correlation showed a positive relationship between cost per patient and physician volume for nonemergency patients (-0.129, p less than 0.0001) and emergency patients (-0.368, p less than 0.0001). This may have been explained (in part) by a greater severity of illness for patients of low-volume urologists. These findings suggest, however, that the volume of urologic procedures per urologist may be related to hospital resource consumption. The health care financing environment of the future should provide substantial interest in this finding for those involved in the consumption of urologic services. 相似文献
6.
A review of the complications of urethral instrumentation performed at our institution during the last 15 years revealed 2 cases of urethrorectal perforation. These patients were managed with loop colostomy and suprapubic cystostomy diversion with excellent healing and no evidence of fistula formation at 24-month followup. This rare complication is described and the principles of diagnosis, prevention and prompt aggressive management are emphasized. 相似文献
7.
8.
Fifty-five students and staff at Robert Gordon's Institute of Technology completed a food frequency questionnaire and then weighed their food for one week. Several methods of calculating nutrient intakes from the questionnaire are compared to results from the weighed inventory. Intakes of energy and several nutrients calculated using estimated typical portion weights were less than those derived from the weighed inventory. Food groups contributing to the apparent under-estimation have been identified. A further method of calculation involved derivation of a factor for each food group such that the frequency estimated from the questionnaire multiplied by the factor equalled the average weight of the foods in that group that had been eaten. Using these factors instead of the typical portion weights resulted in closer agreement to the weighed inventory method, but the difference ranged from positive for some groups to negative for others. Use of separate factors for each group of subjects reduced the range of differences to the weighed inventory method. 相似文献
9.
10.