全文获取类型
收费全文 | 1036篇 |
免费 | 76篇 |
国内免费 | 4篇 |
出版年
2021年 | 7篇 |
2020年 | 19篇 |
2019年 | 41篇 |
2018年 | 30篇 |
2017年 | 8篇 |
2016年 | 16篇 |
2015年 | 18篇 |
2014年 | 27篇 |
2013年 | 44篇 |
2012年 | 70篇 |
2011年 | 102篇 |
2010年 | 84篇 |
2009年 | 41篇 |
2008年 | 33篇 |
2007年 | 28篇 |
2006年 | 35篇 |
2005年 | 22篇 |
2004年 | 21篇 |
2003年 | 21篇 |
2002年 | 17篇 |
2001年 | 35篇 |
2000年 | 22篇 |
1999年 | 28篇 |
1998年 | 24篇 |
1997年 | 15篇 |
1996年 | 22篇 |
1995年 | 19篇 |
1994年 | 8篇 |
1993年 | 20篇 |
1992年 | 15篇 |
1991年 | 11篇 |
1990年 | 16篇 |
1989年 | 24篇 |
1988年 | 9篇 |
1987年 | 14篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1984年 | 8篇 |
1983年 | 9篇 |
1981年 | 7篇 |
1980年 | 10篇 |
1979年 | 10篇 |
1978年 | 12篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1975年 | 6篇 |
1974年 | 8篇 |
1973年 | 10篇 |
1971年 | 7篇 |
1970年 | 9篇 |
排序方式: 共有1116条查询结果,搜索用时 218 毫秒
41.
42.
Sandra Y. Valencia C Carlos A. Isaza M Julieta Henao B Leonardo Beltrán A Nelsy Loango Patricia Landázuri 《Biochemistry and Biophysics Reports》2021
BackgroundControversy exists regarding the role of the subfractions of high-density lipoproteins (HDL2 and HDL3) in cardiovascular disease. The functionality of these particles, and their protective role, is due in part to the paraoxonase 1 (PON1) presence in them. The polymorphisms rs662 (Q192R, A/G), rs854560 (L55 M, T/A), and rs705379 (C-108T) of the PON1 gene have been related to enzyme activity and, with the anti-oxidative capacity of the HDL. The objective was to determine the arylesterase PON1 activity in HDL3 and HDL2 and its relationship with the polymorphisms mentioned, in a young population.MethodsThe polymorphisms were determined through mini-sequencing (SnaPshot). The HDL subpopulations were separated via ionic precipitation, cholesterol was measured with enzymatic methods, and PON1 activity was measured through spectrophotometry.ResultsThe results show that the PON1 polymorphisms do not influence the cholesterol in the HDL. A variation between 40.02 and 43.9 mg/dL was in all the polymorphisms without significant differences. Additionally, PON1 activity in the HDL3 subfractions was greater (62.83 ± 20 kU/L) than with HDL2 (35.8 ± 20.8 kU/L) in the whole population and in all the polymorphisms (p < 0.001), and it was independent of the polymorphism and differential arylesterase activity in the Q192R polymorphism (QQ > QR > RR). Thus, 115.90 ± 30.7, 88.78 ± 21.3, 65.29 ± 10.2, respectively, for total HDL, with identical behavior for HDL3 and HDL2.ConclusionsPON1 polymorphisms do not influence the HDL-c, and the PON activity is greater in the HDL3 than in the HDL2, independent of the polymorphism, but it is necessary to delve into the functionality of these findings in different populations. 相似文献
43.
Prashant G. Bhat Ajay M. V. Kumar Balaji Naik Srinath Satyanarayana Deepak KG Sreenivas A. Nair Suryakanth MD Einar Heldal Donald A. Enarson Anthony J. Reid 《PloS one》2013,8(12)
Background
Severe acute malnutrition (SAM) is the most serious form of malnutrition affecting children under-five and is associated with many infectious diseases including Tuberculosis (TB). In India, nutritional rehabilitation centres (NRCs) have been recently established for the management of SAM including TB. The National TB Programme (NTP) in India has introduced a revised algorithm for diagnosing paediatric TB. We aimed to examine whether NRCs adhered to these guidelines in diagnosing TB among SAM children.Methods
A cross-sectional study involving review of records of all SAM children identified by health workers during 2012 in six tehsils (sub-districts) with NRCs (population: 1.8 million) of Karnataka, India.Results
Of 1927 identified SAM children, 1632 (85%) reached NRCs. Of them, 1173 (72%) were evaluated for TB and 19(2%) were diagnosed as TB. Of 1173, diagnostic algorithm was followed in 460 (37%). Among remaining 763 not evaluated as per algorithm, tuberculin skin test alone was conducted in 307 (41%), chest radiography alone in 99 (13%) and no investigations in 337 (45%). The yield of TB was higher among children evaluated as per algorithm (4%) as compared to those who were not (0.3%) (OR: 15.3 [95%CI: 3.5-66.3]). Several operational challenges including non-availability of a full-time paediatrician, non-functioning X-ray machine due to frequent power cuts, use of tuberculin with suboptimal strength and difficulties in adhering to a complex diagnostic algorithm were observed.Conclusion
This study showed that TB screening in NRCs was sub-optimal in Karnataka. Some children did not reach the NRC, while many of those who did were either not or sub-optimally evaluated for TB. This study pointed to a number of operational issues that need to be addressed if this collaborative strategy is to identify more TB cases amongst malnourished children in India. 相似文献44.
Raquel Montero Manuela Grazina Ester López-Gallardo Julio Montoya Paz Briones Aleix Navarro-Sastre John M. Land Iain P. Hargreaves Rafael Artuch Maria del Mar O'Callaghan Cristina Jou Cecilia Jimenez Nuria Buján Mercè Pineda Angels García-Cazorla Andrés Nascimento Plácido Navas 《Mitochondrion》2013,13(4):337-341
We evaluated coenzyme Q10 (CoQ) levels in patients studied under suspicion of mitochondrial DNA depletion syndromes (MDS) (n = 39). CoQ levels were quantified by HPLC, and the percentage of mtDNA depletion by quantitative real-time PCR. A high percentage of MDS patients presented with CoQ deficiency as compared to other mitochondrial patients (Mann–Whitney-U test: p = 0.001). Our findings suggest that MDS are frequently associated with CoQ deficiency, as a possible secondary consequence of disease pathophysiology. Assessment of muscle CoQ status seems advisable in MDS patients since the possibility of CoQ supplementation may then be considered as a candidate therapy. 相似文献
45.
Margreet J. Oosterkamp Teun Veuskens Flávia Talarico Saia Sander A. B. Weelink Lynne A. Goodwin Hajnalka E. Daligault David C. Bruce John C. Detter Roxanne Tapia Cliff S. Han Miriam L. Land Loren J. Hauser Alette A. M. Langenhoff Jan Gerritse Willem J. H. van Berkel Dietmar H. Pieper Howard Junca Hauke Smidt Gosse Schraa Mark Davids Peter J. Schaap Caroline M. Plugge Alfons J. M. Stams 《PloS one》2013,8(6)
The genomes of the Betaproteobacteria Alicycliphilus denitrificans strains BC and K601T have been sequenced to get insight into the physiology of the two strains. Strain BC degrades benzene with chlorate as electron acceptor. The cyclohexanol-degrading denitrifying strain K601T is not able to use chlorate as electron acceptor, while strain BC cannot degrade cyclohexanol. The 16S rRNA sequences of strains BC and K601T are identical and the fatty acid methyl ester patterns of the strains are similar. Basic Local Alignment Search Tool (BLAST) analysis of predicted open reading frames of both strains showed most hits with Acidovorax sp. JS42, a bacterium that degrades nitro-aromatics. The genomes include strain-specific plasmids (pAlide201 in strain K601T and pAlide01 and pAlide02 in strain BC). Key genes of chlorate reduction in strain BC were located on a 120 kb megaplasmid (pAlide01), which was absent in strain K601T. Genes involved in cyclohexanol degradation were only found in strain K601T. Benzene and toluene are degraded via oxygenase-mediated pathways in both strains. Genes involved in the meta-cleavage pathway of catechol are present in the genomes of both strains. Strain BC also contains all genes of the ortho-cleavage pathway. The large number of mono- and dioxygenase genes in the genomes suggests that the two strains have a broader substrate range than known thus far. 相似文献
46.
Zahid MD Khurshidul Rogowski Michael Ponce Christopher Choudhury Mahua Moustaid-Moussa Naima Rahman Shaikh M. 《Molecular and cellular biochemistry》2020,463(1-2):211-223
Molecular and Cellular Biochemistry - Atherosclerosis is associated with deregulated cholesterol metabolism and formation of macrophage foam cells. CCAAT/enhancer-binding protein beta (C/EBPβ)... 相似文献
47.
Mandana Namayandeh MSc Marzieh Jamalidoust PhD Nahid Heydari Marandi MSc Nasrin Aliabadi PhD student Atoosa Ziyaeyan MASc student Gholamreza Pouladfar MD Mazyar Ziyaeyan PhD 《Microbiology and immunology》2020,64(11):762-767
Hepatitis C is a liver disease caused by the hepatitis C virus (HCV). The treatment of HCV infection has become more complicated due to various genotypes and subtypes of HCV. The treatment of HCV has made significant advances with direct-acting antivirals. However, for the choice of medicine or the combination of drugs for hepatitis C, it is imperative to detect and discriminate the crucial HCV genotypes. The main objective of this study was to determine the pattern of circulating HCV genotypes in southern Iran, from 2016 until 2019. The other aim of the study was to determine possible associations of patients’ risk factors with HCV genotypes. A total of 803 serum samples were collected in 4 years (2016–2019) from patients with HCV antibody positive results. A total of 728 serum samples were HCV-RNA positive. The prevalence of HCV genotypes was detected using the genotype-specific RT-PCR test for serum samples obtained from 615 patients. The HCV genotype 1 (G1) was the most prevalent (48.8%) genotype in the area, with G1a, G1b, and mixed G1a/b representing 38.4%, 10.1%, and 0.3%, respectively. Genotype 3a was the next most prevalent (47.2%). Mixed genotypes 1a/3a were detected in 22 (3.6%) and finally G4 was found in 3 (0.5%) patients. The other HCV genotypes were not detected in any patient. Genotype 1 (1a and 1b alone, 1a/1b and 1a/3a coinfections) is the most prevalent HCV genotype in southern Iran. HCV G1 shows a significantly higher rate in people under 40 years old. 相似文献
48.
Jing Zhou MD Pengfei Wu MM Hongyu Sun MM Hong Zhou BM Yaolei Zhang BM Zhenliang Xiao MD 《Journal of cellular physiology》2020,235(3):2377-2388
This study aimed to examine whether lung tissue extracellular matrix (ECM) hydrogels have protective effects on radiation-induced lung injury (RILI). The cytocompatibility and histocompatibility were tested for the obtained ECM-derived hydrogel. Sprague–Dawley rats were randomly divided into three groups (n = 18): control group (control); rats receiving irradiation and intratracheal injection of normal saline (IR + NS); and rats receiving irradiation and intratracheal injection of lung ECM-derived hydrogel (IR + ECM). The wet/dry weight ratio was used to evaluate the congestion and edema of the lungs. Histopathological analysis of lung tissues was performed using hemotoxylin and eosin staining and Masson's trichrome staining. Immunohistochemical staining and western blot analyses were carried out to determine the expression of epithelial–mesenchymal transition (EMT)-related proteins in lung tissues (E-cadherin, α-smooth muscle actin [α-SMA], and vimentin). In addition, tumor necrosis factor-α (TNF-α), transforming growth factor-β1 (TGF-β1) and interleukin-6 (IL-6), hydroxyproline, malondialdehyde (MDA), and superoxide dismutase (SOD) levels were also evaluated. The ECM-derived hydrogels had good cytocompatibility and histocompatibility. ECM-derived hydrogel treatment improved lung histopathology injury and pulmonary edema. Higher expression of E-cadherin and lower expression of vimentin and α-SMA were found in the IR + ECM group compared with those in the IR + NS group. Hydroxyproline levels were reduced by ECM-derived hydrogel treatment compared with those in the IR + NS group. Obvious increases of TNF-α, IL-6, and TGF-β1 were identified following irradiation. Marked reductions in MDA content and increases in SOD were induced by ECM-derived hydrogel treatment in rats after radiation. ECM-derived hydrogels were shown to protect against RILI, potentially by reducing EMT, inflammation, and oxidative damage. 相似文献
49.
50.
Alfred J. Lewy MD. PhD Jonathan S. Emens Bryan J. Lefler Krista Yuhas Angela R. Jackman 《Chronobiology international》2013,30(6):1093-1106
The specific circadian role proposed for endogenous melatonin production was based on a study of sighted people who took low pharmacological doses (500 µg) of this chemical signal for the “biological night”: the magnitude and direction of the induced phase shifts were dependent on what time of day exogenous melatonin was administered and were described by a phase‐response curve that turned out to be the opposite of that for light. We now report that lower (physiological) doses of up to 300 µg can entrain (synchronize) free‐running circadian rhythms of 10 totally blind subjects that would otherwise drift later each day. The resulting log‐linear dose‐response curve in the physiological range adds support for a circadian function of endogenous melatonin in humans. Efficacy of exogenous doses in the physiological range are of clinical significance for totally blind people who will need to take melatonin daily over their entire lifetimes in order to remain entrained to the 24 h day. Left untreated, their free‐running endocrine, metabolic, behavioral, and sleep/wake cycles can be almost as burdensome as not having vision. 相似文献