全文获取类型
收费全文 | 464篇 |
免费 | 31篇 |
国内免费 | 14篇 |
专业分类
儿科学 | 21篇 |
妇产科学 | 9篇 |
基础医学 | 55篇 |
口腔科学 | 5篇 |
临床医学 | 48篇 |
内科学 | 74篇 |
皮肤病学 | 8篇 |
神经病学 | 15篇 |
特种医学 | 139篇 |
外科学 | 18篇 |
综合类 | 33篇 |
预防医学 | 26篇 |
眼科学 | 12篇 |
药学 | 26篇 |
中国医学 | 1篇 |
肿瘤学 | 19篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 3篇 |
2020年 | 2篇 |
2019年 | 5篇 |
2018年 | 5篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 2篇 |
2014年 | 7篇 |
2013年 | 10篇 |
2012年 | 10篇 |
2011年 | 8篇 |
2010年 | 13篇 |
2009年 | 20篇 |
2008年 | 15篇 |
2007年 | 8篇 |
2006年 | 14篇 |
2005年 | 11篇 |
2004年 | 6篇 |
2003年 | 9篇 |
2002年 | 11篇 |
2001年 | 11篇 |
2000年 | 7篇 |
1999年 | 15篇 |
1998年 | 27篇 |
1997年 | 40篇 |
1996年 | 26篇 |
1995年 | 22篇 |
1994年 | 23篇 |
1993年 | 19篇 |
1992年 | 5篇 |
1991年 | 12篇 |
1990年 | 5篇 |
1989年 | 23篇 |
1988年 | 16篇 |
1987年 | 17篇 |
1986年 | 9篇 |
1985年 | 11篇 |
1984年 | 5篇 |
1983年 | 10篇 |
1982年 | 9篇 |
1981年 | 11篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 1篇 |
排序方式: 共有509条查询结果,搜索用时 15 毫秒
51.
PJ Smith ; TE Miller ; J Fraser ; JW Smith ; JR Svirbely ; S Rudmann ; PL Strohm ; M Kennedy 《Transfusion》1991,31(4):313-317
Four empirical studies were conducted for better understanding of the nature of problem-solving activities by medical technologists and medical technology students when performing antibody identification tasks. The results indicated the importance of strategies that ensure the collection of converging evidence, as these strategies protect against the fallibility of commonly used heuristics and against errors due to simple slips. The results also indicate that not only do students make significant numbers of errors, but so do practicing technologists. In one of the studies covering a 1-year period, for instance, a group of 16 technologists made a total of 41 errors in 1057 cases. On the basis of these findings, several alternatives are proposed to reduce errors. 相似文献
52.
Function of wild-type or mutant Rac2 and Rap1a GTPases in differentiated HL60 cell NADPH oxidase activation 总被引:5,自引:1,他引:5
Studies of neutrophil nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activation in a cell-free system showed that the low molecular-weight guanosine triphosphatase (GTPase) Rac was required, and that Rap1a may participate in activation of the catalytic complex. Full-length posttranslationally modified Rac2 was active, whereas only the 1-166 truncated form of Rap1a was functional in the cell-free system, and thus, clarification of the function of Rap1a and Rac2 in intact human phagocytes is needed to provide further insight into their roles as signal transducers from plasma membrane receptors. In the present studies, oligonucleotide-directed mutagenesis was used to introduce a series of mutations into human rap1a or rac2 in the mammalian expression vector pSR alpha neo. HL60 cells transfected with wild-type or mutated rac2 or rap1a cDNA constructs and control HL60 cells transfected with the pSR alpha neo vector containing no inserted cDNA were selected in G418-containing media, then subclones were isolated. Compared with the parent HL60 cells, each of the stable transfected cell lines differentiated similarly into neutrophil-like cells and expressed comparable levels of NADPH oxidase components p47- phox, p67-phox and gp91-phox. The differentiated vector control cell line produced O2. in response to receptor stimulation at rates that were not significantly different from parent HL60 cells. O2-. production by differentiated cell lines expressing mutated N17 Rap1a or N17 Rac2 dominant-negative proteins was inhibited, whereas O2-. production by the subline overexpressing wild-type Rap1a was increased by fourfold. O2-. production by the differentiated cell line expressing GTPase-defective V12 Rap1a was also significantly inhibited, a finding that is consistent with a requirement for cycling between guanosine diphosphate- and GTP-bound forms of Rap1a for continuous NADPH oxidase activation in intact neutrophils. A model is proposed in which Rac2 mediates assembly of the p47 and p67 oxidase components on the cytosolic face of the plasma membrane via cytoskeletal reorganization, whereas Rap1a functions downstream as the final activation switch involving direct physical interaction with the transmembrane flavocytochrome component of the NADPH oxidase. 相似文献
53.
Kocken PL Eeuwijk J Van Kesteren NM Dusseldorp E Buijs G Bassa-Dafesh Z Snel J 《The Journal of school health》2012,82(3):115-122
BACKGROUND: Vending machines account for food sales and revenue in schools. We examined 3 strategies for promoting the sale of lower‐calorie food products from vending machines in high schools in the Netherlands. METHODS: A school‐based randomized controlled trial was conducted in 13 experimental schools and 15 control schools. Three strategies were tested within each experimental school: increasing the availability of lower‐calorie products in vending machines, labeling products, and reducing the price of lower‐calorie products. The experimental schools introduced the strategies in 3 consecutive phases, with phase 3 incorporating all 3 strategies. The control schools remained the same. The sales volumes from the vending machines were registered. Products were grouped into (1) extra foods containing empty calories, for example, candies and potato chips, (2) nutrient‐rich basic foods, and (3) beverages. They were also divided into favorable, moderately unfavorable, and unfavorable products. RESULTS: Total sales volumes for experimental and control schools did not differ significantly for the extra and beverage products. Proportionally, the higher availability of lower‐calorie extra products in the experimental schools led to higher sales of moderately unfavorable extra products than in the control schools, and to higher sales of favorable extra products in experimental schools where students have to stay during breaks. Together, availability, labeling, and price reduction raised the proportional sales of favorable beverages. CONCLUSION: Results indicate that when the availability of lower‐calorie foods is increased and is also combined with labeling and reduced prices, students make healthier choices without buying more or fewer products from school vending machines. Changes to school vending machines help to create a healthy school environment. 相似文献
54.
Yasser Sakr Vivian PL Maia Clesar Santos Julia Stracke Mohamed Zeidan Ole Bayer Konrad Reinhart 《Critical care (London, England)》2014,18(2):R68
Introduction
Plasma selenium (Se) concentrations are reduced in critically ill surgical patients, and lower plasma Se concentrations are associated with worse outcomes. We investigated whether adjuvant Se supplementation in the form of sodium selenite could improve outcomes in surgical patients with sepsis.Methods
In this retrospective study, all adult patients admitted to a 50-bed surgical ICU with severe sepsis between January 2004 and April 2010 were included and analysed according to whether they had received adjuvant Se supplementation, which was given at the discretion of the attending physician. When prescribed, Se was administered in the form of sodium selenite pentahydrate (Na2SeO3∙5H2O), in which 100 μg of Se corresponds to 333 μg of sodium selenite. A bolus of sodium selenite corresponding to 1,000 μg of Se was injected intravenously through a central venous line for 30 minutes, followed by infusion of 1,000 μg/day for 24 hours for 14 days until ICU discharge or death. We performed logistic regression analysis to investigate the impact of adjuvant Se supplementation on hospital mortality.Results
Adjuvant Se was administered to 413 (39.7%) of the 1,047 patients admitted with severe sepsis. Age and sex were similar between patients who received adjuvant Se and those who did not. Compared with patients who did not receive adjuvant Se supplementation, patients who did had higher scores on the Simplified Acute Physiology Score II, a greater prevalence of cancer upon admission to the ICU and were more commonly admitted after abdominal surgery. Compared with patients who did not receive adjuvant Se, patients who did had higher hospital mortality rates (46% versus 39.1%; P = 0.027), and longer median (interquartile range (IQR)) ICU stays (15 days (6 to 24) versus 11 days (4 to 24); P = 0.01) and hospital lengths of stay (33 days (21 to 52) versus 28 days (17 to 46); P = 0.001). In multivariable analysis, adjuvant Se supplementation was not independently associated with favourable outcome (odds ratio = 1.19, 95% confidence interval = 0.86 to 1.65; P = 0.288).Conclusions
In this retrospective analysis of a large cohort of surgical ICU patients with severe sepsis, adjuvant Se supplementation in the form of sodium selenite had no impact on in-hospital death rates after adjustment for confounders. 相似文献55.
Talmadge JE; Tribble H; Pennington R; Bowersox O; Schneider MA; Castelli P; Black PL; Abe F 《Blood》1989,73(8):2093-2103
Pretreatment of mice with recombinant murine (rM) colony-stimulating factor-granulocyte-macrophage (CSF-gm) or recombinant human (rH) CSF-g provides partial protection from the lethal effects of ionizing radiation or the alkylating agent cyclophosphamide (CTX). In addition, these agents can significantly prolong survival if administered following lethal doses of irradiation or CTX. To induce protective activity, cytokines were injected 20 hours before lethal irradiation or CTX administration. To accelerate recovery from lethal irradiation, the cytokines must be administered shortly following irradiation, and the induction of maximal levels of activity is dependent on chronic administration. In contrast, because of their longer half-lives, accelerated recovery from alkylating agents requires a delay of at least 24 to 48 hours to allow complete clearance of CTX before administration of a CSF. Studies quantitating peripheral blood leukocytes and bone marrow cellularity as well as colony-forming units per culture (CFU-C) frequency and CFU-C per femur revealed a significant correlation between these parameters and the ability to survive lethal irradiation. This is a US government work. There are no restrictions on its use. 相似文献
56.
Storb R; Weiden PL; Sullivan KM; Appelbaum FR; Beatty P; Buckner CD; Clift RA; Doney KC; Hansen J; Martin PJ 《Blood》1987,70(1):116-121
Sixteen (11%) of 146 consecutive patients with severe aplastic anemia prepared for engraftment with cyclophosphamide (200 mg/kg) rejected marrow grafts from their HLA-identical siblings. They were given a second marrow transplant from either the same (n = 13) or a second (n = 3) HLA-identical sibling between 23 and 743 (median 86) days after the first transplant. The preparation for the second transplant included cyclophosphamide, 50 mg/kg, on each of four successive days. Twelve hours after each of the first three doses of cyclophosphamide, antithymocyte globulin, 30 mg/kg/dose, was infused. One of the 16 patients died from infection too early after the second transplant to be evaluated, two had failure of engraftment and died with infection, one rejected the second graft and is surviving almost 5 years later with full autologous marrow recovery, and 12 had successful and sustained second grafts. Of these 12, six are surviving between 11 months and 7 3/4 years. Four of the six have no graft-v-host disease (GVHD), while two have chronic GVHD requiring treatment. Five have Karnofsky scores of 100% and one of 90%. Six of the 12 patients with sustained grafts died between 63 days and 38 months after transplantation, four with infections (related in two patients to chronic GVHD), one with acute GVHD, and one with hemorrhage. The average interval from first to second transplant was 308 days during the past five years, compared to 61 days in earlier patients. Five of seven recent patients are surviving, compared to two of nine earlier patients. In conclusion, successful second transplants after cyclophosphamide and antithymocyte globulin are possible in most patients with aplastic anemia who have rejected their first marrow grafts; however, mortality remains high, with only 40% of the patients becoming long-term survivors. 相似文献
57.
Mitchell PL; Clutterbuck RD; Powles RL; De Lord C; Morilla R; Hiorns LR; Titley J; Catovsky D; Millar JL 《Blood》1996,87(11):4797-4803
Human interleukin-4 (huIL-4) has been shown to inhibit the growth in vitro of cells from patients with acute lymphoblastic leukemia (ALL). With the aim of determining whether this cytokine might be useful in the treatment of patients with ALL, the effects of huIL-4 on human B- cell precursor ALL engrafted in severe combined immunodeficient (SCID) mice were examined. The inhibition of [3H] thymidine uptake of primary ALL cells by huIL-4 was maintained following engraftment and passage of leukemia in SCID mice. Five of seven xenograft leukemias showed significant inhibition in vitro by huIL-4 at concentrations as low as 0.5 ng/mL; furthermore, huIL-4 counteracted the proliferative effects of IL-7. When used to treat two human leukemias engrafted in SCID mice, huIL-4 200 microgram/kg/d, as a continuous 14-day subcutaneous infusion, suppressed the appearance of circulating lymphoblasts and extended survival of mice by 39% and 108%, respectively, the first demonstration of IL-4 activity against human leukemia in vivo. The mean steady-state huIL-4 level in mouse plasma during the infusion was 1.46 ng/mL (SEM +/- 0.14 ng/mL), which was similar to concentrations found to be effective in vitro. ALL cells obtained from mice relapsing after huIL-4 treatment continued to show inhibition by the cytokine in vitro. These data suggest that IL-4 may be useful in the treatment of patients with ALL. 相似文献
58.
JE Barberie DG Connell PL Munk DL Janzen 《Journal of Medical Imaging and Radiation Oncology》1999,43(3):355-357
Muscle and nerve injuries in the hand may be difficult to detect and diagnose clinically. Two cases are reported in which magnetic resonance imaging showed ulnar nerve injury and intrinsic hand muscle denervation. The clinical, anatomical and radiological features of injury to the deep motor branch of the ulnar nerve and associated muscle denervation are discussed and illustrated. 相似文献
59.
Aim: Although obesity and weight gain generally are anticipated to be caused by an imbalance between energy intake and energy expenditure, the significance of thyroid hormones (TH) remains unclear. Examination of mitochondrial function may reflect intracellular thyroid hormone effect and elucidate whether a lower metabolic rate is present. Methods: In a group of 34 obese adolescents (age <16 years and body mass index above the age‐related 95th percentile), and an age‐ and gender‐matched group of 32 lean adolescent, thyroid stimulating hormone (TSH) and basal oxygen consumption were measured and mitochondrial function in peripheral blood monocytes was determined by flow cytometry. Results: Significant increase in TSH (3.06 ± 1.56 mU/L vs. 2.33 ± 0.91 mU/L, p < 0.05) and a decrease in VO2 (129 ± 16 mL O2/m2*min vs. 146 ± 15 mL O2/m2*min, p < 0.05) were observed in obese adolescents compared with lean adolescents. Flow cytometry analysis demonstrated a lower mitochondrial mass (6385 ± 1962 a.u. vs. 7608 ± 2328 a.u., p < 0.05) and mitochondrial membrane potential (11426 ± 3861 a.u. vs. 14017 ± 5536 a.u., p < 0.05) in obese adolescents compared with lean adolescents. These results are even more pronounced in adolescents with obese mothers. Conclusion: In obese adolescents, the increased TSH and lowered VO2 propose a lowered basal metabolic rate and the impaired mitochondrial function suggests a decreased thyroid hormone stimulation of mitochondrial energy production. The maternal in‐heritage is suggestive of a basal metabolic defect or mitochondrial resistance for TH. 相似文献
60.