全文获取类型
收费全文 | 581篇 |
免费 | 34篇 |
出版年
2023年 | 3篇 |
2022年 | 3篇 |
2021年 | 6篇 |
2020年 | 3篇 |
2019年 | 9篇 |
2018年 | 15篇 |
2017年 | 5篇 |
2016年 | 18篇 |
2015年 | 25篇 |
2014年 | 25篇 |
2013年 | 47篇 |
2012年 | 37篇 |
2011年 | 55篇 |
2010年 | 30篇 |
2009年 | 24篇 |
2008年 | 25篇 |
2007年 | 32篇 |
2006年 | 30篇 |
2005年 | 35篇 |
2004年 | 39篇 |
2003年 | 20篇 |
2002年 | 26篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 10篇 |
1995年 | 6篇 |
1994年 | 5篇 |
1993年 | 2篇 |
1991年 | 4篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1984年 | 8篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1974年 | 4篇 |
1973年 | 3篇 |
1972年 | 2篇 |
1965年 | 1篇 |
1933年 | 2篇 |
1930年 | 1篇 |
1908年 | 1篇 |
1897年 | 2篇 |
1896年 | 1篇 |
排序方式: 共有615条查询结果,搜索用时 15 毫秒
181.
Gianluca Iacobellis Filippo Assael Maria Cristina Ribaudo Alessandra Zappaterreno Giuseppe Alessi Umberto Di Mario Frida Leonetti 《Obesity (Silver Spring, Md.)》2003,11(2):304-310
Objective: To validate transthoracic echocardiography as an easy and reliable imaging method for visceral adipose tissue (VAT) prediction. VAT is recognized as an important indicator of high cardiovascular and metabolic risk. Several methods are applied to estimate VAT, with different results. Research Methods and Procedures: We selected 60 healthy subjects (29 women, 31 men, 49.5 ± 16.2 years) with a wide range of body mass indexes. Each subject underwent transthoracic echocardiogram and magnetic resonance imaging (MRI) to measure epicardial fat thickness on the right ventricle. Measurements of epicardial adipose tissue thickness were obtained from the same echocardiographic and MRI views and points. MRI was also used to measure VAT cross‐sectional areas at the level of L4 to L5. Anthropometric indexes were also measured. Results: Subjects with predominant visceral fat accumulation showed higher epicardial adipose tissue thickness than subjects with predominant peripheral fat distribution: 9.97 ± 2.88 vs. 4.34 ± 1.98 (p = 0.005) and 7.19 ± 2.74 vs. 3.43 ± 1.64 (p = 0.004) in men and women, respectively. Simple linear regression analysis showed an excellent correlation between epicardial adipose tissue and waist circumference (r = 0.895, p = 0.01) and MRI abdominal VAT (r = 0.864, p = 0.01). Multiple regression analysis showed that epicardial adipose tissue thickness (r2 = 0.442, p = 0.02) was the strongest independent variable correlated to MRI VAT. Bland test confirmed the good agreement between the two methods. Discussion: Epicardial adipose tissue showed a strong correlation with anthropometric and imaging measurements of VAT. Hence, transthoracic echocardiography could be an easy and reliable imaging method for VAT prediction. 相似文献
182.
Ori Braitbard Janette Bishara-Shieban Hava Glickstein Miriam Kott-Gutkowski Umberto Pace Deborah G Rund Wilfred D Stein 《Proteome science》2006,4(1):14-12
Background
We describe the application of an ELISA-based assay (the Peptidomatrix) that can be used to simultaneously identify and quantitate a number of proteins in biological samples. The biological sample (blood component, biopsy, culture or other) is first lysed to release all the proteins, without any additional separation. The denatured proteins in the sample are then digested in bulk with the desired proteolytic enzyme(s). The peptides in the digest are then assayed by appropriate antibodies, using a competition ELISA protocol. 相似文献183.
Marina M. Carrozzo Giuseppe Cannazza Umberto Battisti Daniela Braghiroli Carlo Parenti 《Chirality》2010,22(4):389-397
On‐column stopped flow multidimensional HPLC (sfMDHPLC) and dynamic high‐performance liquid chromatography were applied to investigate the influence of alkyl substituents at the sulfonamidic and amino moieties of benzothiadiazine 1,1‐dioxide derivatives on hydrolysis and enantiomerization rate constants. The data obtained indicate the presence of pyrrolo substituent at the 3,4 positions on benzothiadiazine rings inhibits the hydrolysis, whereas the enantiomerization occurs in acidic medium. Hydrolysis rates are quite similar for the two benzothiadiazines methyl substituted to nitrogen at 2‐ and 4‐positions. Conversely, enantiomerization rate of 4‐N‐methyl substituted is significantly higher than 2‐N‐methyl substituted. Chirality 2010. © 2009 Wiley‐Liss, Inc. 相似文献
184.
Francesco Nugnes Marco Gebiola Maurilia Maria Monti Liberata Gualtieri Massimo Giorgini Jianguo Wang Umberto Bernardo 《PloS one》2015,10(5)
The blue-gum chalcid Leptocybe invasa Fisher & LaSalle (Hymenoptera: Eulophidae) is a gall wasp pest of Eucalyptus species, likely native to Australia. Over the past 15 years it has invaded 39 countries on all continents where eucalypts are grown. The worldwide invasion of the blue gum chalcid was attributed to a single thelytokous morphospecies formally described in 2004. Subsequently, however, males have been recorded in several countries and the sex ratio of field populations has been found to be highly variable in different areas. In order to find an explanation for such sex ratio differences, populations of L. invasa from a broad geographical area were screened for the symbionts currently known as reproductive manipulators, and both wasps and symbionts were genetically characterized using multiple genes. Molecular analyses suggested that L. invasa is in fact a complex of two cryptic species involved in the rapid and efficient spread of the wasp, the first recovered from the Mediterranean region and South America, the latter from China. All screened specimens were infected by endosymbiotic bacteria belonging to the genus Rickettsia. Two closely related Rickettsia strains were found, each infecting one of the two putative cryptic species of L. invasa and associated with different average sex ratios. Rickettsia were found to be localized in the female reproductive tissues and transovarially transmitted, suggesting a possible role of Rickettsia as the causal agent of thelytokous parthenogenesis in L. invasa. Implications for the variation of sex ratio and for the management of L. invasa are discussed. 相似文献
185.
Egg parasitoids of the genus Anagrus Haliday (Hymenoptera: Mymaridae) are natural enemies of many pests around the world. We used an integrative approach to characterize some species belonging to the Anagrus atomus group, using specimens reared from leafhoppers infesting some Lamiaceae. Starting from morphological identifications based on available keys, we carried out a multi-locus genetic characterization using phylogenetic and species delimitation analyses, and integrated it with biological and morphometric evidence. This approach revealed the existence of a new species, A. nepetellae sp. nov., here described along with its phenological traits. The approach also allowed us to characterize the expected taxonomic stability of other putative species within the group. We propose two new species groups called the atomus group sensu stricto and the vilis group, with the goal of streamlining the taxonomy of the atomus group. We also present a key for the identification of females of the European species of the atomus group sensu stricto. Some specimens show heterozygosity in 28S-D2 sequences, suggesting hybridization between A. atomus and A. nepetellae, which, if it is common between other species as well, could partly explain the taxonomic problems in the genus Anagrus. DNA sequencing of specimens reared by the same biofactory at different times suggests involuntary contamination leading to the displacement of a laboratory strain of A. atomus by A. nepetellae, which may have resulted from undetected partial reproductive compatibility.http://zoobank.org/urn:lsid:zoobank.org:pub:DFCD7654-5AA5-4E4F-AE48-24377BAACEFE 相似文献
186.
Maurizio Botta Raffaele Saladino Luigi Stasi Umberto Ciambecchini Rosario Nicoletti 《Nucleosides, nucleotides & nucleic acids》2013,32(4-5):555-556
Abstract A general, selective and efficient synthesis of N,N-dialkyl-cytosine derivatives bearing a vinyl moiety on the C-6 side chain is reported. 相似文献
187.
The Late Triassic—Early Jurassic ichnofauna described mainly by Paul Ellenberger from southern Africa (Lesotho) is a valuable window on first phases of dinosaur diversification. Unfortunately, the present taxonomic status of several forms from that ichnofauna is unclear. The revision of this material has been frequently invoked and partially done without reaching many definitive results. Due to the enormous amount of data, a global revision seems at present impossible and must be accomplished in smaller steps. A small number of Ellenberger's ichnogenera including Tetrasauropus, Pseudotetrasauropus, Pentasauropus, Paratetrasauropus, Sauropodopus and Deuterosauropodopus, which different authors have ascribed to basal sauropodomorphs, are here revised in a consistent manner and their attribution to osteological clades is considered. Tetrasauropus and Pseudotetrasauropus are here validated as the only ichnotaxa related to sauropodomorphs. Pentasauropus is retained as valid, and a therapsid trackmaker is suggested. Paratetrasauropus and Sauropodopus are also validated and ascribed to non-dinosaurian trackmakers, and Deuterosauropodopus is synonymized with Sauropodopus. 相似文献
188.
Giacomina Brunetti Angela Oranger Claudia Carbone Giorgio Mori Francesca Rita Sardone Claudio Mori Monica Celi Maria Felicia Faienza Umberto Tarantino Alberta Zallone Maria Grano Silvia Colucci 《Cell biochemistry and biophysics》2013,67(3):1127-1136
Apoptosis can occur throughout the life span of osteoblasts (OBs), beginning from the early stages of differentiation and continuing throughout all stages of their working life. Here, we investigated the effects of tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) on normal human OBs showing for the first time that the expression of TRAIL receptors is modulated during OB differentiation. In particular, the TRAIL receptor ratio was in favor of the deaths because of the low expression of DcR2 in undifferentiated OBs, differently it was shifted toward the decoys in differentiated ones. Undifferentiated OBs treated with TRAIL showed reduced cell viability, whereas differentiated OBs displayed TRAIL resistance. The OB sensitiveness to TRAIL was due to the up-regulation of DR5 and the down-regulation of DcR2. The main death receptor involved in TRAIL-reduced OB viability was DR5 as demonstrated by the rescue of cell viability observed in the presence of anti-DR5 neutralizing antibody. Besides the ratio of TRAIL receptors, the sensitivity of undifferentiated OBs to TRAIL-cytotoxic effect was also associated with low mRNA levels of intracellular anti-apoptotic proteins, such as cFLIP, the activation of caspase-8 and -3, as well as the DNA fragmentation. This study suggests that apoptotic effect exerted by TRAIL/TRAIL-receptor system on normal human OB is strictly dependent upon cell differentiation status. 相似文献
189.
Cinzia Auriti Domenico Umberto De Rose Alessandra Santisi Ludovica Martini Fiammetta Piersigilli Iliana Bersani Maria Paola Ronchetti Leonardo Caforio 《生物化学与生物物理学报:疾病的分子基础》2021,1867(10):166198
Some maternal infections, contracted before or during pregnancy, can be transmitted to the fetus, during gestation (congenital infection), during labor and childbirth (perinatal infection) and through breastfeeding (postnatal infection). The agents responsible for these infections can be viruses, bacteria, protozoa, fungi. Among the viruses most frequently responsible for congenital infections are Cytomegalovirus (CMV), Herpes simplex 1–2, Herpes virus 6, Varicella zoster. Moreover Hepatitis B and C virus, HIV, Parvovirus B19 and non-polio Enteroviruses when contracted during pregnancy may involve the fetus or newborn at birth. Recently, new viruses have emerged, SARS-Cov-2 and Zika virus, of which we do not yet fully know the characteristics and pathogenic power when contracted during pregnancy.Viral infections in pregnancy can damage the fetus (spontaneous abortion, fetal death, intrauterine growth retardation) or the newborn (congenital anomalies, organ diseases with sequelae of different severity). Some risk factors specifically influence the incidence of transmission to the fetus: the timing of the infection in pregnancy, the order of the infection, primary or reinfection or chronic, the duration of membrane rupture, type of delivery, socio-economic conditions and breastfeeding. Frequently infected neonates, symptomatic at birth, have worse outcomes than asymptomatic. Many asymptomatic babies develop long term neurosensory outcomes.The way in which the virus interacts with the maternal immune system, the maternal-fetal interface and the placenta explain these results and also the differences that are observed from time to time in the fetal?neonatal outcomes of maternal infections. The maternal immune system undergoes functional adaptation during pregnancy, once thought as physiological immunosuppression. This adaptation, crucial for generating a balance between maternal immunity and fetus, is necessary to promote and support the pregnancy itself and the growth of the fetus. When this adaptation is upset by the viral infection, the balance is broken, and the infection can spread and lead to the adverse outcomes previously described. In this review we will describe the main viral harmful infections in pregnancy and the potential mechanisms of the damages on the fetus and newborn. 相似文献
190.