全文获取类型
收费全文 | 1387篇 |
免费 | 177篇 |
国内免费 | 63篇 |
出版年
2024年 | 5篇 |
2023年 | 24篇 |
2022年 | 29篇 |
2021年 | 35篇 |
2020年 | 48篇 |
2019年 | 47篇 |
2018年 | 42篇 |
2017年 | 41篇 |
2016年 | 31篇 |
2015年 | 40篇 |
2014年 | 74篇 |
2013年 | 103篇 |
2012年 | 66篇 |
2011年 | 79篇 |
2010年 | 56篇 |
2009年 | 73篇 |
2008年 | 88篇 |
2007年 | 61篇 |
2006年 | 61篇 |
2005年 | 69篇 |
2004年 | 56篇 |
2003年 | 41篇 |
2002年 | 35篇 |
2001年 | 18篇 |
2000年 | 23篇 |
1999年 | 28篇 |
1998年 | 21篇 |
1997年 | 21篇 |
1996年 | 16篇 |
1995年 | 20篇 |
1994年 | 20篇 |
1993年 | 21篇 |
1992年 | 18篇 |
1991年 | 11篇 |
1990年 | 12篇 |
1989年 | 13篇 |
1988年 | 17篇 |
1987年 | 10篇 |
1986年 | 8篇 |
1985年 | 20篇 |
1984年 | 17篇 |
1983年 | 12篇 |
1982年 | 13篇 |
1981年 | 22篇 |
1980年 | 13篇 |
1979年 | 13篇 |
1978年 | 14篇 |
1976年 | 4篇 |
1974年 | 8篇 |
1973年 | 5篇 |
排序方式: 共有1627条查询结果,搜索用时 15 毫秒
1.
《Cytokine》2015,71(2):194-197
Osteopontin (OPN) acts as an osteoclast activator, a proinflammatory cytokine, and a chemokine attracting histiocytes/monocytes and is abundantly expressed in Langerhans cell histiocytosis (LCH). We investigated whether serum OPN levels are related to disease types in LCH. Fifty-eight newly diagnosed LCH patients were studied; eight with risk organ (liver, spleen and/or hematopoietic) involvements positive multisystem (MS+) disease, 27 with risk organ involvement negative multisystem (MS−) disease and 23 with single system (SS) disease. Pediatric patients with non-inflammatory disease (n = 27) were used as controls. All of patients with MS+ disease were younger than 3 years. Serum OPN levels and 44 kinds of humoral factors were measured by ELISA and Bio-Plex suspension array system, respectively. In the patients younger than 3 years, the median serum OPN level (interquartile range) was 240.3 ng/ml (137.6–456.0) in MS+ (n = 8); 92.7 ng/ml (62.0–213.8) in MS− (n = 14) and 72.5 ng/ml (55.6–94.0) in SS (n = 9) and 74.4 ng/ml (42.2–100.0) in control (n = 12). The OPN values were significantly higher in the MS+ group than the MS−, SS and control groups (p = 0.044, p = 0.001 and p = 0.002, respectively), but not different between the MS−, SS and control groups. In the patients older than 3 years, the median level of serum OPN (IQR) was 56.2 ng/ml (22.9–77.5) in MS− (n = 13), 58.9 ng/ml (31.0–78.7) in SS (n = 14) and 41.9 (28.9–54.1) in control (n = 15). These values did not differ significantly between each group. The serum OPN levels were positively correlated with the serum IL-6, CCL2, IL-18, IL-8 and IL-2 receptor concentration. OPN may be involved in risk organ dissemination and poor prognosis of LCH through the function as inflammatory cytokine/chemokine. 相似文献
2.
《Cytokine》2015,72(2):132-138
The purpose of this study was to determine if vitamin D status before supplementation influences the cytokine response after supplemental vitamin D. Forty-six reportedly healthy adults (mean(SD); age, 32(7) y; body mass index (BMI), 25.3(4.5) kg/m2; serum 25-hydroxyvitamin D (25(OH)D), 34.8(12.2) ng/mL) were randomly assigned (double blind) to one of three groups: (1) placebo (n = 15), or supplemental vitamin D (cholecalciferol) at (2) 4000 (n = 14) or (3) 8000 IU (n = 17). Supplements were taken daily for 35 days. Fasting blood samples were obtained before (Baseline, Bsl) and 35-days after (35-d) supplementation. Serum 25(OH)D, 1,25-dihydroxyvitamin D (1,25(OH)D), cytokines, and intact parathyroid hormone with calcium were measured in each blood sample. Supplemental vitamin D increased serum 25(OH)D (4000 IU, ≈29%; 8000 IU, ≈57%) and 1,25(OH)D (4000 IU, ≈12%; 8000 IU, ≈38%) without altering intact parathyroid hormone or calcium. The vitamin D metabolite increases in the supplemental vitamin D groups (n = 31) were dependent on initial levels as serum 25(OH)D (r = −0.63, p < 0.05) and 1,25(OH)D (r = −0.45, p < 0.05) at Bsl correlated with their increases after supplementation. Supplemental vitamin D increased interferon (IFN)-γ and interleukin (IL)-10 in subjects that were vitamin D insufficient (serum 25(OH)D < 29 ng/mL) compared to sufficient (serum 25(OH)D ⩾ 30 ng/mL) at Bsl. We conclude that supplemental vitamin D increase a pro- and anti-inflammatory cytokine in those with initially low serum 25(OH)D. 相似文献
3.
Activity of salivary glands in secreting honey‐elaborating enzymes in two subspecies of honeybee (Apis mellifera L) 下载免费PDF全文
Aliaa A. Al‐Sherif Adel M. Mazeed Mohamed A. Ewis Emad A. Nafea El‐Seid E. Hagag Ahmed A. Kamel 《Physiological Entomology》2017,42(4):397-403
The activity of invertase, glucose oxidase and amylase in the cephalic (post‐cerebral) and thoracic salivary glands is determined in Egyptian and Carniolan honeybees (Apis mellifera L). For this purpose, three ages of worker bees are selected for enzyme assays. The results show that the three target enzymes are detected in the two glands during the three worker ages, except invertase, which cannot be detected in the cephalic gland of newly emerged bees of both subspecies. In both glands, the secretion of invertase is highest, followed by amylase and then glucose oxidase. In Carniolan bees, invertase secretion of the cephalic and thoracic glands increases gradually with age. In Egyptian bees, invertase increases with age only in the cephalic gland, whereas, in the thoracic gland, the highest secretion activity is detected in 10–15‐day‐old bees. The highest amounts of glucose oxidase and amylase in the cephalic gland are detected in newly emerged individuals of both Egyptian and Carniolan bees. In the thoracic gland, however, the highest activity of both enzymes is recorded only in newly emerged Egyptian bees. The results are discussed in the light of bee management and biological aspects of the two subspecies. 相似文献
4.
《Saudi Journal of Biological Sciences》2019,26(8):2057-2063
ObjectiveThrough metabolomics method, the objective of the paper is to differentially screen serum metabolites of GDM patients and healthy pregnant women, to explore potential biomarkers of GDM and analyze related pathways, and to explain the potential mechanism and biological significance of GDM.MethodsThe serum samples from 30 GDM patients and 30 healthy pregnant women were selected to conduct non-targeted metabolomics study by liquid chromatography-mass spectrometry. The differential metabolites between the two groups were searched and the metabolic pathway was analyzed by KEGG database.ResultsMultivariate statistical analysis found that serum metabolism in GDM patients was different significantly from healthy pregnant women, 36 differential metabolites and corresponding metabolic pathways were identified in serum, which involved several metabolic ways like, fatty acid metabolism, butyric acid metabolism, bile secretion, and amino acid metabolism.ConclusionThe discovery of these biomarkers provided a new theoretical basis and experimental basis for further study of the early diagnosis and pathogenesis of GDM. At the same time, LC-MS-based serum metabolomics methods also showed great application values in disease diagnosis and mechanism research. 相似文献
5.
On the primary structure of amylases 总被引:4,自引:0,他引:4
F Friedberg 《FEBS letters》1983,152(2):139-140
6.
The concept of the blood-aqueous barrier is largely based on the use of horseradish peroxidase (HRP). The present investigation
was designed to check its reliability as a macromolecular tracer, especially with regard to the transport of plasma proteins.
Rabbits were killed 5 min to 24 h after being intravenously injected with HRP. The tracer diffused rapidly, reaching the aqueous
humor of the eye in 3 min or less and was detected at high concentration in the narrow space between the outer epithelial
layer of the ciliary epithelium and the wall of the pervious capillaries in the stroma of the processes. HRP appeared to migrate
from the blood to the posterior chamber, permeating the tight junctions, viz., the anatomical basis of the blood-aqueous barrier.
It was detected at higher concentration at the anterior surface of the iris, at short time intervals; this was interpreted
as penetration of the tracer from the aqueous humor of the anterior chamber. The choroid was also labeled in continuation
with the reaction in the stroma of the pars plana of the ciliary body which, in turn, sometimes reached the iris root. Therefore,
the pervious blood vessels of the choroid could be a source of macromolecules for the iris root. HRP also induced the formation
of lysosomes in the ciliary epithelium. This can hardly be accepted as the way in which plasma proteins are physiologically
transported to the aqueous humor. However, the pathway of HRP migration over short time intervals seems to be in agreement
with previous research indicating that the entrance of serum albumin into the posterior chamber is the first step of its incorporation
into the aqueous humor.
Received: 7 June 1996 / Accepted: 15 January 1997 相似文献
7.
Purpose: The value of lactate as a screening biomarker in the emergency department is debated. We analysed all unselected patients in the emergency department with serum lactate measured with regard to different outcome parameters.Material and Methods: In a retrospective single centre study, we analysed all digitalized patient data of a two-week period of all patients ≥18 where a serum lactate was measured. The lactate levels as well as demographic and other laboratory data were correlated in a logistic regression analysis, univariable as well as multivariable, with the outcome parameters.Results: A total of 1157 patients contacted the emergency department of which 587 were included. The average lactate level was 2,08?mmol/l (SD ±1.51, median 1.73). A total of 313 patients were admitted to hospital, 274 treated as outpatients. Their median lactate levels were 2.0?mmol/l (min/max 0.6–18?mmol/l) and 1.5?mmol/l (min/max 0.5–7.4?mmol/l), respectively. Univariable regression analysis for hospital admission showed an odds ratio of 1756 (p?0.001), multivariable regression analysis showed a positive correlation for hospital admission for lactate (OR 1532, p?=?0.004). There was no correlation with admission to ICU, length of stay or a relation to a certain diagnostic group.Conclusions: Screening lactate levels in unselected emergency department patients do not have a clinical relevance yet. 相似文献
8.
Sylvia M. Scotland Bengü Said rea Thomas Bernard Rowe 《FEMS microbiology letters》1994,115(2-3):285-289
Abstract Sera, from 17 patients with diarrhoea or haemolytic uraemic syndrome, and six healthy adults, were tested for neutralisation of Vero cytotoxins (VT). For all 17 patients there was evidence of infection with Escherichia coli O157. Sera from two controls but from none of the patients neutralised VT1, although two patients were infected by strains producing VT1 and VT2. Sera from all six controls and 14 patients neutralised VT2 derived from strains 933 and E32511, but not variant forms of VT2 derived from strains E32511, E57, B2F1 and H.1.8. This neutralising activity warrants further investigation, especially as many 0157 VTEC carry both VT2 and VT2 variant genes. 相似文献
9.
The titanium-chelation method has been used to immobilize β-amylase (1,4-α-d-glucan maltohydrolase, EC 3.2.1.2) on to Spheron. On various grades of Spheron, protein coupling yields of 56–76% were obtained with barley and sweet-potato β-amylases. The specific enzymic activities of the immobilized enzymes fell in the range 3.7–7.6% of those of the soluble enzymes. The immobilized enzymes were more stable than the soluble, especially in the presence of l-cysteine and serum albumin. The presence of cysteine and serum albumin brought about increases in activity in the preparations, presumably by regenerating essential thiol groups in the enzyme which had been oxidized during the operations. Maltose could be separated from amylopectin and other large polysaccharides by chromatography on Spheron P100, and a system was developed in which maltose, produced by hydrolysis of amylopectin applied in pulses to a column of immobilized β-amylase, was separated from starting material and by-products on a second column of Spheron P100. 相似文献
10.
《Bioorganic & medicinal chemistry letters》2014,24(1):314-316
Cy-Cl, a cationic near-infrared cyanine dye, readily reacts with hydrogen sulfide (H2S) via nucleophilic thiolation to give dose-dependent ‘turn-off’ fluorescence and colorimetric read-out, allowing selective detection of low levels of H2S in serum and imaging of mitochondrial H2S in living cells. 相似文献