全文获取类型
收费全文 | 96875篇 |
免费 | 6066篇 |
国内免费 | 738篇 |
专业分类
耳鼻咽喉 | 1109篇 |
儿科学 | 2879篇 |
妇产科学 | 2379篇 |
基础医学 | 13159篇 |
口腔科学 | 2128篇 |
临床医学 | 8229篇 |
内科学 | 21231篇 |
皮肤病学 | 2022篇 |
神经病学 | 8942篇 |
特种医学 | 3797篇 |
外国民族医学 | 23篇 |
外科学 | 13485篇 |
综合类 | 1657篇 |
一般理论 | 49篇 |
预防医学 | 5686篇 |
眼科学 | 1504篇 |
药学 | 7843篇 |
3篇 | |
中国医学 | 515篇 |
肿瘤学 | 7039篇 |
出版年
2023年 | 393篇 |
2022年 | 969篇 |
2021年 | 1743篇 |
2020年 | 1122篇 |
2019年 | 1620篇 |
2018年 | 2015篇 |
2017年 | 1531篇 |
2016年 | 1624篇 |
2015年 | 1910篇 |
2014年 | 2536篇 |
2013年 | 3706篇 |
2012年 | 4982篇 |
2011年 | 5186篇 |
2010年 | 3354篇 |
2009年 | 2940篇 |
2008年 | 4629篇 |
2007年 | 4797篇 |
2006年 | 4561篇 |
2005年 | 4433篇 |
2004年 | 4768篇 |
2003年 | 4594篇 |
2002年 | 4601篇 |
2001年 | 3713篇 |
2000年 | 3667篇 |
1999年 | 2986篇 |
1998年 | 1176篇 |
1997年 | 898篇 |
1996年 | 836篇 |
1995年 | 804篇 |
1994年 | 702篇 |
1993年 | 691篇 |
1992年 | 1784篇 |
1991年 | 1770篇 |
1990年 | 1497篇 |
1989年 | 1444篇 |
1988年 | 1330篇 |
1987年 | 1188篇 |
1986年 | 1171篇 |
1985年 | 1038篇 |
1984年 | 763篇 |
1983年 | 696篇 |
1982年 | 453篇 |
1981年 | 388篇 |
1979年 | 568篇 |
1978年 | 419篇 |
1975年 | 430篇 |
1974年 | 481篇 |
1973年 | 462篇 |
1972年 | 425篇 |
1971年 | 393篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
R De Schrijver 《The Journal of nutrition》1990,120(12):1624-1632
In two feeding experiments immature (180 g) and mature rats (370 g) were fed a semi-purified diet containing 20% of a protein source (casein, wheat gluten, soybean or potato protein) for 4 wk. Food supply was restricted to 15 g daily. As compared to casein, plant proteins induced significantly lower concentrations of plasma total cholesterol and high density lipoprotein (HDL) cholesterol. The plasma cholesterol increase associated with aging was not prevented by consumption of casein, soybean or potato protein, but wheat gluten seemed to be effective. Lecithin-cholesterol acyltransferase (LCAT) activity was not significantly different in rats of the same age fed different plant proteins, whereas the esterification rate was lower in rats fed casein. With aging the LCAT activity generally decreased. As compared to the casein groups, the rats fed plant proteins showed higher excretion of fecal neutral and acidic steroids. Among the groups fed plant proteins, the fecal output of steroids was variable. Significantly negative correlations were found between fecal total sterol excretion and plasma total cholesterol or HDL cholesterol, respectively. Plant proteins showed a faster migration rate in the stomach, whereas their migration and absorption were slower in the first half of the small intestine. A relation between nonabsorbed nitrogen-containing substances and sterol excretion was hypothesized. 相似文献
92.
Effect of a glutamine-supplemented enteral diet on methotrexate-induced enterocolitis 总被引:15,自引:0,他引:15
A D Fox S A Kripke J De Paula J M Berman R G Settle J L Rombeau 《JPEN. Journal of parenteral and enteral nutrition》1988,12(4):325-331
Administration of an elemental diet to rats given methotrexate (MTX), 20 mg/kg intraperitoneally (ip), results in 100% mortality from severe enterocolitis. Previous studies indicate that glutamine (GLN), which is not present in elemental diets, is the preferred oxidative substrate for the gut and may facilitate intestinal recovery after injury. This study investigated the effects of a glutamine-supplemented elemental diet (GLN-ED) on nutritional status, intestinal morphometry, bacterial translocation and survival in this lethal model of intestinal injury. Three experiments were performed. In the first experiment, rats received an intragastric elemental diet supplemented with either 2% GLN or an equivalent amount of glycine (Control). After 4 days animals received either MTX, 20 mg/kg ip, or saline ip and were killed 3 days later. The GLN-ED resulted in significantly decreased weight loss, improved nitrogen retention, and increased mucosal weight, protein, and DNA content of the jejunum and colon. In the second experiment rats were assigned to diet as in the first experiment, but all animals received MTX. Control diet animals died within 120 hrs of MTX administration. The GLN-ED group had significantly longer survival time and decreased mortality. In the third experiment animals were assigned to diet and MTX as in the first experiment. Ninety-six hrs later aortic blood cultures revealed enteric bacteremia in animals administered MTX. GLN-ED resulted in a significant reduction in the incidence of bacteremia. These experiments showed that a GLN-ED significantly improved nutritional status, decreased intestinal injury, decreased bacterial translocation, and resulted in improved survival in a lethal model of enterocolitis. 相似文献
93.
94.
G. Vacca E. Marano V. Brescia Morra R. Lanzillo M. De Vito E. Parente G. Orefice 《Neurological sciences》2007,28(3):133-135
The prevalence of primary headache (PH) in a multiple sclerosis (MS) sample vs. control healthy subjects was investigated at a neurological clinic in 2004–2005: 122 of 238 (51%) MS patients and 57 of
238 (23%) controls proved to be affected by headache. The groups did not differ for the rates of PH types. Headache types
of MS patients were comparable to those of PH patients that were observed at the same institute in a case-control comparison.
First symptoms of headache preceded those of MS in two thirds of cases. Headache features did not significantly change after
MS onset. Comorbidity of MS and PH could be explained by some common clinical and biological traits. 相似文献
95.
Daily nutrient intake represents a modifiable determinant of nutritional status in chronic haemodialysis patients. 总被引:2,自引:0,他引:2
Vincenzo Bellizzi Biagio R Di Iorio Vincenzo Terracciano Roberto Minutolo Carmela Iodice Luca De Nicola Giuseppe Conte 《Nephrology, dialysis, transplantation》2003,18(9):1874-1881
BACKGROUND: In maintenance haemodialysis patients, daily food intake is changeable; however, its relationship with nutritional status is unexplored. This study aimed to evaluate the isolated, long-term effect of daily nutrient intake on nutritional status in haemodialysis patients. METHODS: We performed a prospective 1-year controlled study in 27 chronic haemodialysis patients, without recognized risk factors for malnutrition. Each day for 1 week, four times in the year, we measured protein nitrogen appearance, and assessed dietary protein (DPI) and energy (DEI) intake from dietary diaries. We compared the nutritional outcome of patients spontaneously reducing nutrient intake below the threshold of 0.8 g/kg body weight/day for DPI and 25 kcal/kg body weight/day for DEI during the week (LOW, n = 8), with controls at adequate nutrient intake (CON, n = 19). An interventional 6-month study was then carried out in LOW to verify the cause-effect relationship. RESULTS: All patients showed a day-by-day reduction of whole nutrient intake during interdialytic period, which was mostly relevant in the third interdialytic day (L3). During the 1-year study, even in the presence of adequate dialysis dose and normal inflammatory indexes, body weight (68.0 +/- 5.5 to 65.8 +/- 5.9 kg), serum albumin (3.96 +/- 0.07 to 3.66 +/- 0.06 g/dl) and creatinine (9.2 +/- 1.1 to 8.1 +/- 0.7 mg/dl) significantly decreased in LOW but not in CON. Diaries evidenced in LOW a reduced number of meals at L3 that was explained by the fear of excessive interdialytic weight gain. During the interventional study, daily DPI and DEI increased at L3; this was associated with a significant increment of body weight, and serum albumin and creatinine levels. CONCLUSIONS: In maintenance haemodialysis patients the persistent, marked reduction of daily nutrient intake, even if limited to a single day of the week, is an independent determinant of reversible impairment of nutritional status. 相似文献
96.
97.
98.
Objectives: To investigate the effect of the type instrumentation used and the age and gender characteristics of patients on postoperative haemorrhage rates following tonsil and adenoid surgery. Design: A retrospective analysis of 13 593 procedures was performed from The Patient Episode Database for Wales between 1 January 1999 and 31 March 2004. Setting: National health policy changes created four periods of different instrument usage (reusable, single‐use with diathermy, single‐use alone, specified single‐use with diathermy). These and the age and gender distribution of the patients were examined against four categories of postoperative haemorrhage. Main outcome measures: Postoperative haemorrhage rates were expressed as the number of complications per operations performed. Primary postoperative haemorrhage that occurred during the initial admission either required a return to theatre [R1] or was managed conservatively [N1]; secondary postoperative haemorrhage that required a return to hospital either returned to theatre [R2] or was managed conservatively [N2], were compared. Results: Primary haemorrhage with return to theatre doubled, from the baseline rate with reusable instruments, from 0.6% (CI 0.5–0.8) to 1.2% (CI 0.7–1.9) when single‐use instruments were introduced and remained high at 1.4% (CI 0.9–2.1) after the withdrawal of single‐use diathermy. This haemorrhage rate returned to the baseline rate (0.6% CI 0.3–1.0) when specified single‐use instruments were introduced. None of the other haemorrhage rates changed significantly throughout the four observation periods. Adenotonsillectomy and tonsillectomy patients have different age and gender patterns. In a univariate analysis, males over the age of 12 years were twice as likely to have haemorrhage with return to theatre than girls of the same age, 3.8% (CI 3.0–4.7) versus 1.7% (CI 1.4–2.1). Conclusions: A significant rise in serious postoperative primary haemorrhage but not secondary haemorrhage was seen following the initial introduction of single‐use instruments that reverted to baseline with the introduction of specified single‐use instruments. Diathermy does not appear to have affected the haemorrhage rates. There is a distinct age and gender pattern for tonsil and adenoid surgery and risk of postoperative haemorrhage. The use of arbitrary divisions of age may be misleading in studies that examine post‐tonsillectomy haemorrhage. 相似文献
99.
K Decaestecker E Decaestecker C Castellani M Jaspers H Cuppens K De Boeck 《The European respiratory journal》2004,23(5):679-684
In this European study, the phenotype in 68 patients, homozygous or compound heterozygous for the G85E mutation, was investigated. Each index case was compared with two cystic fibrosis (CF) patients from the same clinic, matched for age and sex: one with pancreatic sufficiency (PS) and one with pancreatic insufficiency (PI). When comparing 31 G85E/F508del and F508del/F508del patients, there were no differences in median age at diagnosis, mean sweat chloride value, most recent weight for height, most recent forced expiratory volume in one second % predicted, prevalence of chronic Pseudomonas aeruginosa colonisation and typical CF complications. However, PI was less frequent in the G85E/F508del group. Comparison of 55 G85E patients (with second mutation known and not classified as mild) with PS controls (n=44) showed that the G85E patients had a significantly higher sweat chloride, more often failure to thrive at diagnosis, higher prevalence of PI, worse current weight for height, higher prevalence of chronic P. aeruginosa colonisation and liver cirrhosis. Pulse-chase experiments revealed that G85E cystic fibrosis transmembrane conductance regulator failed to mature on a M470 as well as on a V470 background. Therefore, G85E is a class II mutation. Although there is variability in its clinical presentation, G85E mutation results in a severe phenotype. 相似文献
100.
Transcriptional downregulation of tight junction protein ZO-1 in active coeliac disease is reversed after a gluten-free diet 总被引:1,自引:0,他引:1