全文获取类型
收费全文 | 6016篇 |
免费 | 694篇 |
出版年
2021年 | 76篇 |
2018年 | 56篇 |
2016年 | 85篇 |
2015年 | 153篇 |
2014年 | 143篇 |
2013年 | 232篇 |
2012年 | 248篇 |
2011年 | 245篇 |
2010年 | 151篇 |
2009年 | 156篇 |
2008年 | 204篇 |
2007年 | 231篇 |
2006年 | 227篇 |
2005年 | 200篇 |
2004年 | 209篇 |
2003年 | 178篇 |
2002年 | 209篇 |
2001年 | 189篇 |
2000年 | 193篇 |
1999年 | 174篇 |
1998年 | 99篇 |
1997年 | 84篇 |
1995年 | 80篇 |
1994年 | 66篇 |
1993年 | 92篇 |
1992年 | 157篇 |
1991年 | 130篇 |
1990年 | 141篇 |
1989年 | 117篇 |
1988年 | 106篇 |
1987年 | 108篇 |
1986年 | 95篇 |
1985年 | 107篇 |
1984年 | 100篇 |
1983年 | 82篇 |
1982年 | 71篇 |
1981年 | 62篇 |
1980年 | 76篇 |
1979年 | 90篇 |
1978年 | 72篇 |
1977年 | 75篇 |
1976年 | 65篇 |
1975年 | 71篇 |
1974年 | 81篇 |
1973年 | 88篇 |
1972年 | 61篇 |
1971年 | 54篇 |
1970年 | 58篇 |
1968年 | 48篇 |
1967年 | 47篇 |
排序方式: 共有6710条查询结果,搜索用时 31 毫秒
991.
992.
Christopher J. Rhodes Chantal S. Hinds Harry Morris Ivan D. Reid 《Free radical research》1997,27(4):347-352
Thiyl radicals (RS.) are formed when positive muons (μ+) are implanted into solutions of thiocarbonyl compounds (C = S) in ethanol, tetrahydrofuran or formamide solvents. A solvent dependence is found, which reflects changing electronic interactions and overall conformations, suggesting that the properties of RS. radicals may be dependent on the polarity (philicity) of the environment in which they are formed. 相似文献
993.
D. A. Willins B. Liu X. Xiang N. R. Morris 《Molecular genetics and genomics : MGG》1997,255(2):194-200
To identify proteins that interact directly or indirectly with the NUDF protein, which is required for nuclear migration in Aspergillus nidulans, we initiated a screen for extragenic suppressors of the heat-sensitive nudF6 mutation. Suppressor mutations in at least five genes, designated snfA–snfE, caused improved growth and nuclear migration at high temperatures compared to the nudF6 parent. Two snfC mutations mapped near the nudA gene, which encodes the cytoplasmic dynein heavy chain, and could be repaired by transformation with wild-type nudA DNA, demonstrating that they are mutations in nudA. The snfC mutations are bypass suppressors of nudF and genetic evidence indicated that NUDA and NUDF act in the same nuclear migration pathway. Taken together, our data suggests that NUDF affects nuclear migration by acting on the dynein motor system. 相似文献
994.
We describe a method for the detection of specific antibody-producing cells from either in vitro or in vivo immunization.
These techniques are especially useful for detecting antibodies from developing hybridomas. We have successfully used the
system to detect isotype-specific antibodies to a variety of bacterial antigens which were produced by heterohybridomas. 相似文献
995.
David M Baekey Kendall F Morris Sarah C Nuding Lauren S Segers Bruce G Lindsey Roger Shannon 《Journal of applied physiology》2004,96(6):2057-2072
The expiration reflex is a distinct airway defensive response characterized by a brief, intense expiratory effort and coordinated adduction and abduction of the laryngeal folds. This study addressed the hypothesis that the ventrolateral medullary respiratory network participates in the reflex. Extracellular neuron activity was recorded with microelectrode arrays in decerebrated, neuromuscular-blocked, ventilated cats. In 32 recordings (17 cats), 232 neurons were monitored in the rostral (including B?tzinger and pre-B?tzinger complexes) and caudal ventral respiratory group. Neurons were classified by firing pattern, evaluated for spinal projections, functional associations with recurrent laryngeal and lumbar nerves, and firing rate changes during brief, large increases in lumbar motor nerve discharge (fictive expiration reflex, FER) elicited during mechanical stimulation of the vocal folds. Two hundred eight neurons were respiratory modulated, and 24 were nonrespiratory; 104 of the respiratory and 6 of the nonrespiratory-modulated neurons had altered peak firing rates during the FER. Increased firing rates of bulbospinal neurons and expiratory laryngeal premotor and motoneurons during the expiratory burst of FER were accompanied by changes in the firing patterns of putative propriobulbar neurons proposed to participate in the eupneic respiratory network. The results support the hypothesis that elements of the rostral and caudal ventral respiratory groups participate in generating and shaping the motor output of the FER. A model is proposed for the participation of the respiratory network in the expiration reflex. 相似文献
996.
F A Dilmanian G M Morris G Le Duc X Huang B Ren T Bacarian J C Allen J Kalef-Ezra I Orion E M Rosen T Sandhu P Sathé X Y Wu Z Zhong H L Shivaprasad 《Cellular and molecular biology, including cyto-enzymology》2001,47(3):485-493
Duck embryo was studied as a model for assessing the effects of microbeam radiation therapy (MRT) on the human infant brain. Because of the high risk of radiation-induced disruption of the developmental process in the immature brain, conventional wide-beam radiotherapy of brain tumors is seldom carried out in infants under the age of three. Other types of treatment for pediatric brain tumors are frequently ineffective. Recent findings from studies in Grenoble on the brain of suckling rats indicate that MRT could be of benefit for the treatment of early childhood tumors. In our studies, duck embryos were irradiated at 3-4 days prior to hatching. Irradiation was carried out using a single exposure of synchrotron-generated X-rays, either in the form of parallel microplanar beams (microbeams), or as non-segmented broad beam. The individual microplanar beams had a width of 27 microm and height of 11 mm, and a center-to-center spacing of 100 microm. Doses to the exposed areas of embryo brain were 40, 80, 160 and 450 Gy (in-slice dose) for the microbeam, and 6, 12 and 18 Gy for the broad beam. The biological end point employed in the study was ataxia. This neurological symptom of radiation damage to the brain developed within 75 days of hatching. Histopathological analysis of brain tissue did not reveal any radiation induced lesions for microbeam doses of 40-160 Gy (in-slice), although some incidences of ataxia were observed in that dose group. However, severe brain lesions did occur in animals in the 450 Gy microbeam dose groups, and mild lesions in the 18 Gy broad beam dose group. These results indicate that embryonic duck brain has an appreciably higher tolerance to the microbeam modality, as compared to the broad beam modality. When the microbeam dose was normalized to the full volume of the irradiated tissue. i.e., the dose averaged over microbeams and the space between the microbeams, brain tolerance was estimated to be about three times higher to microbeam irradiation as compared with broad beam irradiation. 相似文献
997.
Salmonella enterica Serotype Bredeney: Antimicrobial Susceptibility and Molecular Diversity of Isolates from Ireland and Northern Ireland 下载免费PDF全文
Martin Cormican Niall DeLappe Colette OHare Geraldine Doran Dearbhaile Morris Geraldine Corbett-Feeney Samus Fanning Mairead Daly Margaret Fitzgerald John Moore 《Applied microbiology》2002,68(1):181-186
Salmonella enterica serotype Bredeney has emerged as the third most commonly identified serotype among human clinical isolates referred to the Irish National Salmonella Reference Laboratory in the years 1998 to 2000. A collection of 112 isolates of S. enterica serotype Bredeney collected during the period 1995 to 1999 from animal, food, and human sources from both Ireland and Northern Ireland were studied. Antimicrobial susceptibility testing, pulsed-field gel electrophoresis (PFGE), and DNA amplification fingerprinting (DAF) were performed on all isolates. Plasmid profiles were examined on a subset of 33 isolates. A high proportion (74%) of isolates were susceptible to all antimicrobial agents tested. Resistance to both sulfonamide and trimethoprim was observed in 21% of isolates, and resistance to multiple (five) antimicrobial agents was observed in a single isolate (0.9%). Eight different PFGE patterns were obtained, with 87% of isolates grouping as PFGE type A. PFGE type A was predominant in animals, food, and humans. There was good overall concordance between the groups identified by PFGE and DAF. Overall results indicate that most S. enterica serotype Bredeney isolates in Ireland and Northern Ireland from animal and human sources are clonally related. 相似文献
998.
The Schiff base N-(2-hydroxy-3-carboxy-1-naphthylidine)-4-methyl-2-sulphonic acid aniline (bonsaH3) has been found to react with a range of divalent metal ions (Mg2+, Mn2+, Co2+, Ni2+ and Zn2+ and UO22+ to give red-yellow insoluble complexes (bonsaH)m(H2O)n. The solid state diffuse reflectance spectra of all the complexes have an intense visible band at ca. 470 nm. This fact, together with evidence from infrared spectra and room-temperature magnetic-moment measurements, suggests that in all cases the ligand is coordinated to the metal ion in the solid state in the enol-iminium zwitterionic form. The 1H NMR spectra of the Mg2+ and Zn2+ complexes in DMSO-d6 indicate that a different structure is adopted in this solvent. Comparisons with the spectra of bonsa-H3 and (bonsa-H2)K·H2O suggest that the solution structure is that of an enol-imine. 相似文献
999.
Previously the growth of Spartina alterniflora has been found to be limited by nitrogen and correlated with sediment redox potential. In this study we have investigated a possible connection between these two factors. We have found that internal O2 transport is insufficient to saturate NH4+ uptake in short S. alterniflora in hydroponic culture. Rates of NH4+ uptake and root respiration were very sensitive to O2 concentration in the rhizosphere, saturating at about 5% O2. Ammonium uptake continued at a reduced rate for at least 4 hr under anaerobic conditions. Plant to plant variations in anaerobic rates of NH4+ uptake and root respiration were significantly correlated to the diffusion rate of CH4 tracer gas from the leaves to the roots of individual plants. 相似文献
1000.