全文获取类型
收费全文 | 9651篇 |
免费 | 786篇 |
国内免费 | 185篇 |
专业分类
耳鼻咽喉 | 11篇 |
儿科学 | 387篇 |
妇产科学 | 75篇 |
基础医学 | 701篇 |
口腔科学 | 230篇 |
临床医学 | 604篇 |
内科学 | 1687篇 |
皮肤病学 | 83篇 |
神经病学 | 519篇 |
特种医学 | 94篇 |
外科学 | 446篇 |
综合类 | 612篇 |
现状与发展 | 1篇 |
预防医学 | 3761篇 |
眼科学 | 27篇 |
药学 | 563篇 |
5篇 | |
中国医学 | 260篇 |
肿瘤学 | 556篇 |
出版年
2024年 | 12篇 |
2023年 | 185篇 |
2022年 | 891篇 |
2021年 | 1061篇 |
2020年 | 507篇 |
2019年 | 415篇 |
2018年 | 380篇 |
2017年 | 331篇 |
2016年 | 345篇 |
2015年 | 399篇 |
2014年 | 573篇 |
2013年 | 809篇 |
2012年 | 446篇 |
2011年 | 416篇 |
2010年 | 360篇 |
2009年 | 320篇 |
2008年 | 371篇 |
2007年 | 328篇 |
2006年 | 267篇 |
2005年 | 238篇 |
2004年 | 204篇 |
2003年 | 199篇 |
2002年 | 164篇 |
2001年 | 110篇 |
2000年 | 126篇 |
1999年 | 98篇 |
1998年 | 95篇 |
1997年 | 95篇 |
1996年 | 74篇 |
1995年 | 66篇 |
1994年 | 58篇 |
1993年 | 58篇 |
1992年 | 69篇 |
1991年 | 54篇 |
1990年 | 43篇 |
1989年 | 39篇 |
1988年 | 48篇 |
1987年 | 38篇 |
1986年 | 39篇 |
1985年 | 45篇 |
1984年 | 36篇 |
1983年 | 31篇 |
1982年 | 30篇 |
1981年 | 28篇 |
1980年 | 27篇 |
1979年 | 17篇 |
1978年 | 22篇 |
1977年 | 12篇 |
1975年 | 7篇 |
1974年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
BACKGROUND: Because little is known about micronutrient/antioxidant intake and asthma severity, we investigated dietary intake and plasma/serum levels of micronutrients/antioxidants in a group of asthma patients with various degrees of severity, and compared the results with healthy subjects. METHODS: A case control study was carried out on 118 asthma patients and 121 healthy subjects. The severity of the disease was classified by division of patients into four groups. Normal dietary micronutrient/antioxidant intake was estimated from a food frequency questionnaire. Plasma/serum levels of vitamins C, E, and A, selenium, magnesium, zinc, and platelet glutathione peroxidase (GSH-Px) activity were also determined. RESULTS: No differences in daily micronutrient/antioxidant intake were seen between patients and healthy subjects. The severity of the disease showed no significant relationship with micronutrient/antioxidant intake. There were no differences in plasma/serum levels in any of the micronutrients/antioxidants between healthy subjects and asthmatics. Nor were any differences found between asthma groups in severity in the biochemical measures, except in platelet GSH-Px activity, which was significantly lower in the most severe groups. CONCLUSIONS: In this study, we found no evidence of any association between micronutrient/antioxidant intake or plasma/serum levels of micronutrients/antioxidants and asthma. Reduction of platelet GSH-Px activity in the most severe patients suggests that these patients have a diminished capacity to restore part of the antioxidant defences. 相似文献
42.
M G Tordoff 《Physiology & behavior》1985,35(3):455-463
Rats that were neonatally sympathectomized with guanethidine (GUA) and given access to a four-component supermarket diet (SD) when either adolescent or adult gained weight at the same rate as controls. Adrenodemedullation (MDL) of adults, either alone or in combination with GUA treatment, also failed to influence the development of dietary obesity. Neonatal sympathectomy induced small changes in caloric consumption and diet preferences. These results question the notion that the sympathetic nervous system (SNS) is an essential contributor to the control of body weight and the development of dietary obesity. 相似文献
43.
P DESREUMAUX A LEVY J P VAERMAN M CAPRON A CORTOT J F COLOMBEL 《Clinical and experimental immunology》1996,104(2):293-296
The effects of nutrients on the mucosal immune system are poorly understood. The aim of this work was to study the cellular mucosal immune response to intrajejunal perfusion of an elemental diet (ED) or a control (C) electrolyte solution by measuring jejunal secretion of soluble CD4 (sCD4) and sCD8. sCD4 and sCD8 are markers of helper/inducer and suppressor/cytotoxic regulatory functions of T cells, respectively. A four lumen tube with a proximal occluding balloon at the angle of Treitz was used for jejunal perfusion in seven healthy volunteers (mean age 23 years). The length of the test segment was 40 cm. The jejunum was successively perfused with C for 80 min and then with ED containing 21.3g/l of free amino acids and 104.2g/l of oligosaccharides for 100 min. Jejunal fluid and serum concentrations of sCD4 and sCD8 were measured and their jejunal outputs calculated. When compared with C perfusion, jejunal perfusion with the ED resulted in a significant increase of sCD8 but not sCD4 jejunal secretion rates. sCD8 jejunal values increased early after ED perfusion and stayed at roughly the same level during the perfusion. Serum concentrations of sCD4 and sCD8 were not modified during ED perfusion. These data support the hypothesis that ED suppresses the immunologic tone of the gut, which could explain its beneficial effect in the management of intestinal inflammatory disease. 相似文献
44.
Ninety-one high atopy-risk infants were prospectively followed up to 18 months of age with regard to the development of allergic/atopic manifestations and sensitization. They were randomized into one of two feeding groups, i.e., a hydrolyzed, ultrafiltered cow's milk whey formula, Profylac® ( n = 32), or an ordinary cow's milk formula ( n = 39), for 12 months, started after exclusive breast-feeding for 0–9 (median 6.0) months. Lactating mothers avoided milk, egg, and fish, as did the infants up to 12 months of age. Twenty of the 91 infants were breast-fed exclusively for more than 9 months and regarded as a control group. All infants were followed-up by questionnaires, physical examinations, skin prick tests, and determination of serum total IgE and cow's milk-specific IgE. The frequency of allergic/atopic disease was similar in the three groups. However, all three infants who developed cow's milk allergy with skin symptoms belonged to the cow's milk formula group. The skin prick test with whey hydrolysate was negative in all, while with cow's milk it was positive in eight infants. Growth was similar in the three groups. The study comprises too few infants to allow us to make statistically based statements. However, the difficulties encountered and the limited effects obtained by the use of whey hydrolysate at weaning at about 6 months of age made us conclude that we can spare high atopy-risk families this extra burden. 相似文献
45.
The SLC14 gene family of urea transporters 总被引:3,自引:0,他引:3
Carrier-mediated urea transport allows rapid urea movement across the cell membrane, which is particularly important in the process of urinary concentration and for rapid urea equilibrium in non-renal tissues. Urea transporters mediate passive urea uptake that is inhibited by phloretin and urea analogues. Facilitated urea transporters are divided into two classes: (1) the renal tubular/testicular type of urea transporter, UT-A1 to -A5, encoded by alternative splicing of the SLC14A2 gene, and (2) the erythrocyte urea transporter UT-B1 encoded by the SLC14A1 gene. The primary structure of urea transporters is unique, consisting of two extended, hydrophobic, membrane-spanning domains and an extracellular glycosylated-connecting loop. UT-A1 is the result of a gene duplication of this two-halves-structure, and the duplicated portions are linked together by a large intracellular hydrophilic loop, carrying several putative protein kinase A (PKA) and -C (PKC) phosphorylation sites. UT-A1 is located in the apical membrane of the kidney inner medullary collecting duct cells, where it is stimulated acutely by cAMP-mediated phosphorylation in response to the antidiuretic hormone vasopressin. Vasopressin also up-regulates UT-A2 mRNA/protein expression in the descending thin limb of the loops of Henle. UT-A1 and UT-A2 are regulated independently and respond differently to changes in dietary protein content. UT-A3 and UT-A4 are located in the rat kidney medulla and UT-A5 in the mouse testis. The widely expressed UT-B participates in urea recycling in the descending vasa recta, as demonstrated by a relatively mild "urea-selective" urinary concentrating defect in transgenic UT-B null mice and individuals with the Jknull blood group. 相似文献
46.
D.V. Coscina J.W. Chambers I. Park S. Hogan J. Himms-Hagen 《Brain research bulletin》1985,14(6):585-593
Two experiments were performed to determine if bilateral parasagittal hypothalamic knife-cuts (KCs), which produce long-term overeating and obesity, after biochemical indices of brown adipose tissue (BAT) reactivity to thermogenic stimuli. In the first study, responses to environmental cold were tested. Four weeks after surgery, KC rats had gained 4-5 times more weight than controls and were obese (increased Lee Obesity Index and weight of gonadal white fat). Before being sacrificed, groups of KC and control rats were exposed to 4 degrees C for 21 hr or remained at 28 degrees C. Interscapular BAT weighed 300% more in KC rats, due largely to increased white fat content. Functional indices of BAT thermogenic capacity (protein content, DNA content, cytochrome oxidase activity and mitochondrial guanosine diphosphate (GDP) binding) were normal at 28 degrees C. Exposure to 4 degrees C produced greatly enhanced responses but these were equivalent for both groups. This suggested an intact capacity for non-shivering thermogenesis in obese KC rats. In the second study, the same BAT responses were examined in other rats fed a palatable "cafeteria" diet (CAFE). One week after surgery, KC and control rats were subdivided into groups that received chow alone or chow plus four different palatable foods daily. Before sacrificing 4-5 weeks later, KC rats had gained 3-4 times more weight than controls and were obese. Interscapular BAT weighed 200-300% more in KC rats. CAFE feeding produced larger increments in all variables for KC vs. control rats. Most importantly, GDP binding was reduced in both KC groups, and significantly more so after CAFE feeding.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
47.
A classic feature of animals with lateral hypothalamic (LH) lesions is their regulation of body weight at sub-normal levels. The present studies were done to determine whether this is associated with enhanced thermogenic activity of their brown adipose tissue (BAT). Three groups of young chow-fed male Holtzman rats were formed: (1) animals receiving bilateral radiofrequency heat lesions of the dorsal LH and then permitted free access to chow (LH rats); (2) non-lesioned animals that were pair-fed (PF) to the lesioned rats during a 2 week post-operative recovery period (Phase 1); (3) non-lesioned, ad lib fed (NORM) controls. After Phase 1, each group was divided and permitted free access to chow alone or an additional selection of palatable, novel food items (a "cafeteria" diet) for 2-3 weeks (Phase 2) to stimulate diet-induced thermogenesis in BAT. Finally, half of each sub-group was exposed to 4 degrees C for 15 hr to stimulate nonshivering thermogenesis in BAT. During Phase 1 LHs and PFs ate 50% less than NORMs. This resulted in a weight deficit of 16% for LHs and 12% for PFs. After the additional period of feeding palatable foods (Phase 2) LHs collectively weighed 14% less than NORMs whereas previously PFs had a weight deficit of only 4%. They gained less weight than NORMs or PFs despite a similar energy intake. LHs had small deposits of gonadal white adipose tissue [both total amount and expressed per metabolic body mass (kg 0.75)]. The weight of interscapular BAT was less in the LHs but its concentration of protein (mg/g) was higher.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
48.
We identified dish-based dietary patterns for breakfast, lunch, and dinner and assessed the diet quality of each pattern. Dietary data were obtained from 392 Japanese adults aged 20–69 years in 2013, using a 4 d dietary record. K-means cluster analysis was conducted based on the amount of each dish group, separately for breakfasts (n = 1462), lunches (n = 1504), and dinners (n = 1500). The diet quality of each dietary pattern was assessed using the Healthy Eating Index 2015 (HEI-2015) and Nutrient-Rich Food Index 9.3 (NRF9.3). The extracted dietary patterns were as follows: ‘bread-based’ and ‘rice-based’ for breakfast; ‘bread’, ‘rice-based’, ‘ramen’, ‘udon/soba’, and ‘sushi/rice bowl dishes’ for lunch; and ‘miscellaneous’, ‘meat dish and beer’, and ‘hot pot dishes’ for dinner. For breakfast, the HEI-2015 and NRF9.3 total scores were higher in the ‘rice-based’ pattern than the ‘bread-based’ pattern. For lunch, the HEI-2015 and NRF9.3 total scores were relatively high in the ‘rice-based’ pattern and low in the ‘ramen’ pattern. For dinner, the HEI-2015 total score was the highest in the ‘meat dish and beer’ pattern, and the NRF9.3 total score was higher in the ‘hot pot dishes’ than the ‘miscellaneous’ pattern. These results suggested that breakfast, lunch, and dinner have distinctive dietary patterns with different diet qualities. 相似文献
49.
Inflammatory bowel diseases, which include ulcerative colitis and Crohn’s disease, are chronic relapsing and remitting inflammatory diseases of the gastrointestinal tract that are increasing in prevalence and incidence globally. They are associated with significant morbidity, reduced quality of life to individual sufferers and are an increasing burden on society through direct and indirect costs. Current treatment strategies rely on immunosuppression, which, while effective, is associated with adverse events. Epidemiological evidence suggests that diet impacts the risk of developing IBD and modulates disease activity. Using diet as a therapeutic option is attractive to patients and clinicians alike due to its availability, low cost and few side effects. Diet may influence IBD risk and disease behaviour through several mechanisms. Firstly, some components of the diet influence microbiota structure and function with downstream effects on immune activity. Secondly, dietary components act to alter the structure and permeability of the mucosal barrier, and lastly dietary elements may have direct interactions with components of the immune response. This review will summarise the mechanisms of diet–microbial–immune system interaction, outline key studies examining associations between diet and IBD and evidence demonstrating the impact of diet on disease control. Finally, this review will outline current prescribed dietary therapies for active CD. 相似文献
50.