全文获取类型
收费全文 | 2555篇 |
免费 | 179篇 |
出版年
2023年 | 9篇 |
2022年 | 19篇 |
2021年 | 33篇 |
2020年 | 27篇 |
2019年 | 26篇 |
2018年 | 50篇 |
2017年 | 48篇 |
2016年 | 75篇 |
2015年 | 103篇 |
2014年 | 120篇 |
2013年 | 188篇 |
2012年 | 191篇 |
2011年 | 176篇 |
2010年 | 136篇 |
2009年 | 127篇 |
2008年 | 173篇 |
2007年 | 160篇 |
2006年 | 160篇 |
2005年 | 125篇 |
2004年 | 152篇 |
2003年 | 113篇 |
2002年 | 114篇 |
2001年 | 16篇 |
2000年 | 12篇 |
1999年 | 30篇 |
1998年 | 28篇 |
1997年 | 21篇 |
1996年 | 19篇 |
1995年 | 30篇 |
1994年 | 18篇 |
1993年 | 23篇 |
1992年 | 20篇 |
1991年 | 16篇 |
1990年 | 24篇 |
1989年 | 16篇 |
1988年 | 10篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 11篇 |
1981年 | 16篇 |
1980年 | 8篇 |
1979年 | 5篇 |
1978年 | 10篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1974年 | 12篇 |
1973年 | 4篇 |
排序方式: 共有2734条查询结果,搜索用时 15 毫秒
31.
Georgina W. Hall Maurizio Sampietro Rebecca Barnetson Joan Fitzgerald Shaun McCann SweeLay Thein 《Human genetics》1993,92(1):28-32
Using the technique of allele-specific priming of the polymerase chain reaction (PCR), the C-T substitution in codon 39 was identified as the cause of -thalassaemia in an Irish family. Analysis of the restriction fragment length polymorphisms (RFLPs) in the -globin gene cluster established linkage of the -thalassaemia mutation to a particular -haplotype but indicated that a recombinational event had occurred in the paternal chromosome in the younger of two affected children. Non-paternity was excluded by DNA fingerprinting analysis with hypervariable minisatellite probes. This is the fourth case of recombination in the -globin gene cluster to be reported. The event has occurred 5 of the polymorphic RsaI site at position-550 bp upstream of the -globin gene mRNA Cap site, within the 9.1-kb region that has been shown to be a hot spot for recombination in the -globin gene cluster. 相似文献
32.
Susanna Dolci Maurizio Pesce Massimo De Felici 《Molecular reproduction and development》1993,35(2):134-139
In the present paper we investigated the effects of stem cell factor/mastocyte growth factor (SCF/MGF), leukemia inhibitory factor/differentiating inhibitory activity (LIF/DIA) (two growth factors known to affect primordial germ cell growth in vitro) and forskolin (FRSK) (an activator of adenylate cyclase in many cell types) alone or in combination on the survival and proliferation of primordial germ cells (PGCs) obtained from 8.5, 10.5, and 11.5 days post coitum (dpc) mouse embryos and cultured without pre-formed cell feeder layers. The results showed that both at 1 and 3 days of culture the addition of 100 ng/ml SCF, 20 μM FRSK, or in some instances 20 ng/ml LIF alone caused a significant increase of PGC number as compared with controls. The highest effects were obtained when SCF and/or LIF were used together with FRSK. Moreover, we found that FRSK elevated cAMP levels in purified 11.5 dpc PGCs and that this compound, but not SCF and LIF, stimulated PGC proliferation, as assessed by 5-bromo-2′-deoxyuridin (BrdU) incorporation. These results suggest a mechanism of combined action of cAMP with SCF and/or LIF in the control of proliferation of mouse PGCs in vitro. © 1993 Wiley-Liss, Inc. 相似文献
33.
Serafina Perrone Chiara Lembo Maurizio Giordano Chiara Petrolini Laura Cannavò Eloisa Gitto 《Journal of biochemical and molecular toxicology》2023,37(6):e23349
Oxidative stress is a pathological condition characterized by an overload of oxidant products, named free radicals, which are not well counteracted by antioxidant systems. Free radicals induce oxidative damage to many body organs and systems. In neonatal red blood cells, free-radical mediated-oxidative stress leads to eryptosis, a suicidal death process of erythrocytes consequent to alteration of cell integrity. Neonatal red blood cells are targets and at the same time generators of free radicals through the Fenton and Haber-Weiss reactions. Enhanced eryptosis in case of oxidative stress damage may cause anemia if the increased loss of erythrocytes is not enough compensated by enhanced new erythrocytes synthesis. The oxidative disruption of the red cells may cause unconjugated idiopathic hyperbilirubinemia in neonates. High levels of bilirubin are recognized to be dangerous for the central nervous system in newborns, however, many studies have highlighted the antioxidant function of bilirubin. Recently, it has been suggested that physiologic concentration of bilirubin correlates with higher antioxidant status while high pathological bilirubin levels are associated with pro-oxidants effects. The aim of this educational review is to provide an updated understanding of the molecular mechanisms underlying erythrocyte oxidant injury and its reversal in neonatal idiopathic hyperbilirubinemia. 相似文献
34.
35.
Maurizio Sarà Roberto Firmamento Giuseppe Cangemi Luca Pagano Martina Genovese Teresa Romeo Silvestro Greco 《Ibis》2023,165(1):328-339
Birds use stopovers during migration to interrupt endurance flight in order to minimize immediate and/or future fitness costs. Stopovers on ships is considered an exceptional and anecdotal event in the ornithological literature. This does not match the experience we had in the summer of 2021, during an oceanographic campaign in the Central Mediterranean, when we regularly observed on average 2.8 birds, of at least 13 species, stopping on board during the 25 days of the campaign. The median stopping time was 42 min, ranging from a few minutes to overnight stays on board. The probability of finding a bird stopping aboard increased with wind force and cloud cover. Birds also stopped more often in a headwind and did not stop when the wind came from different directions other than the headwind. The Central Mediterranean is one of the busiest sea routes in the world, combining the mean daily number of birds on board with the thousands of ships that pass through it during the 3 months of summer migration; we estimate that nearly 4 million birds could use ships as stopover sites. This behaviour may represent a modern-day strategy that uses ships as stopovers in the event of adverse weather conditions or could act as an ecological trap, increasing the mortality of migrants. This phenomenon deserves more research attention and further studies recording body condition and tagging of individuals on board would be informative. 相似文献
36.
Maurizio Pellecchia Gerhard Wider Hideo Iwai Kurt Wüthrich 《Journal of biomolecular NMR》1997,10(2):193-197
A novel 2D NMR experiment, 2D HE(NE)HGHH, is presented for the assignment ofarginine side chain 1H and 15N resonances inuniformly 15N-labeled proteins. Correlations between1H, 1Hand 1H are established on the basis of3J(15N,1H) heteronuclear scalarcoupling constants, and sequence-specific assignments are obtained by overlapof these fragments with 1H chemical shiftsobtained by assignment procedures starting from the polypeptide backbone.Since guanidino protons exchange quite rapidly with the bulk water, the 2DHE(NE)HGHH pulse scheme has been optimized to avoid saturation and dephasingof the water magnetization during the course of the experiment. As anillustration, arginine side chain assignments are presented for two uniformly15N-labeled proteins of 7 and 23 kDa molecular weight. 相似文献
37.
S. Aime Mauro Botta S. Geninatti Crich Giovanni B. Giovenzana Roberto Pagliarin Maurizio Piccinini Massimo Sisti Enzo Terreno 《Journal of biological inorganic chemistry》1997,2(4):470-479
A novel heptacoordinating ligand consisting of a thirteen-membered tetraazamacrocycle containing the pyridine ring and bearing
three methylenephosphonate groups (PCTP-[13]) has been synthesized. Its Gd(III) complex displays a remarkably high longitudinal
water proton relaxivity (7.7 mM–1 s–1 at 25 °C, 20 MHz and pH 7.5) which has been accounted for in terms of contributions arising from (1) one water molecule
bound to the metal ion, (2) hydrogen-bonded water molecules in the second coordination sphere, or (3) water molecules diffusing
near the paramagnetic chelate. Variable-temperature 17O-NMR transverse relaxation data indicate that the residence lifetime of the metal-bound water molecule is very short (8.0 ns
at 25 °C) with respect to the Gd(III) complexes currently considered as contrast agents for magnetic resonance imaging. Furthermore,
GdPCTP-[13] interacts with human serum albumin (HSA), likely through electrostatic forces. By comparing water proton relaxivity
data for the GdPCTP-[13]-HSA adduct, measured as a function of temperature and magnetic field strength, with those for the
analogous adduct with GdDOTP (a twelve-membered tetraaza macrocyclic tetramethylenephosphonate complex lacking a metal-bound
water molecule), it has been possible to propose a general picture accounting for the main determinants of the relaxation
enhancement observed when a paramagnetic Gd(III) complex is bound to HSA. Basically, the relaxation enhancement in these systems
arises from (1) water molecules in the hydration shell of the macromolecule and protein exchangeable protons which lie close
to the interaction site of the paramagnetic complex and (2) the metal bound water molecule(s). As far as the latter contribution
is concerned, the interaction with the protein causes an elongation of the residence lifetime of the metal-bound water molecule,
which limits, to some extent, the potential relaxivity enhancement expected upon the binding of the paramagnetic complex to
HSA.
Received: 27 January 1997 / Accepted: 12 May 1997 相似文献
38.
Maurizio Meta Marco Ponte Marina Guastella Claudia Semino Gabriella Pietra Giovanni Battista Ratto Giovanni Melioli 《Cancer immunology, immunotherapy : CII》1995,40(4):235-240
Despite the combined use of surgery and chemoradiotherapy, the poor prognosis of advanced non-smallcell lung cancer (NSCLC) requires the definition of new therapeutic approaches. The presence of T lymphocytes, with peculiar phenotypic, functional and molecular characteristics within the tumour, suggested the possible use of these cells, expanded in vitro, in protocols of adoptive immunotherapy. We have described how a population of oligoclonal T lymphocytes, derived from advanced NSCLC, can be expanded in vitro and has the capability of lysing autologous cancer cells. What is more important, we observed that patients with advanced NSCLC, treated with TIL expanded in vitro and recombinant interleukin-2, seemed to have a disease-free period longer than that of patients treated with conventional chemoradiotherapy. in an attempt to find new sources of specific lymphocytes for immunotherapy, we describe the analysis of the phenotypic, functional and molecular characteristics of T lymphocytes, derived from lymph nodes draining advanced NSCLC. In this paper we show that these cells, have restriction patterns of T cell receptor chain similar to those detectable in the population of infiltrating T lymphocytes. This finding suggests that T cells derived from draining lymph nodes of advanced NSCLC have peculiar characteristics and can be a suitable source of effector cells for protocols of adoptive immunotherapy in lung cancer treatment. 相似文献
39.
Maurizio Zandomeneghi 《Chirality》1995,7(6):446-451
Complexation of 2-(3′-benzoylphenyl)propionic acid (ketoprofen), 1 , to bovine serum albumin (BSA) results in an intense negative circular dichroism in the ketonic n → π* band of the benzoylphenyl moiety. This high CD contrasts with the weak CD of 1 -enantiomers dissolved in common solvents. Furthermore, a number of chiral and achiral molecules containing the benzophenone moiety are easily complexed to BSA: all these complexes show an intense CD at the same transition. To account for the observed CD intensities of the above molecules, it appears that BSA complexation markedly shifts the equilibrium between strongly asymmetric, antipodic conformers. Dissymmetry of these conformers is connected to the instability of a structure with phenyl rings coplanar to the carbonyl chromophore, as also indicated by molecular mechanics calculations. The magnification of the Cotton effects of the 1 -antipodes, due to the protein, can be used to measure the optical purity of 1 -samples with excellent precision. In contrast with BSA, human SA is unable to recognize the chirality of 1 -antipodes; oleic acid cocomplexation modifies this fact as well as other features of the binding. © 1995 Wiley-Liss, Inc. 相似文献
40.
Maurizio Pacifici 《Matrix biology》1995,14(9)
In comparison to the vast literature on articular cartilage structure and function, relatively little is known about how articular cartilage forms during embryo-genesis and is endowed with unique phenotypic properties, most notably the ability to persist and function throughout postnatal life. In this minireview, we summarize recent studies from our laboratory suggesting that the extracellular matrix protein tenascin-C is involved in the genesis and function of articular chondrocytes. These and other data have led us to propose that tenascin-C may be part of in vivo mechanisms whereby articular chondrocytes develop at the epiphysis of long bone models, remain functional throughout postnatal life, and avoid the endochondral ossification process undertaken by the bulk of chondrocytes located in the metaphysis and diaphysis of skeletal models. 相似文献