全文获取类型
收费全文 | 2668篇 |
免费 | 209篇 |
国内免费 | 1篇 |
出版年
2023年 | 9篇 |
2022年 | 19篇 |
2021年 | 48篇 |
2020年 | 25篇 |
2019年 | 24篇 |
2018年 | 41篇 |
2017年 | 32篇 |
2016年 | 83篇 |
2015年 | 131篇 |
2014年 | 148篇 |
2013年 | 178篇 |
2012年 | 235篇 |
2011年 | 239篇 |
2010年 | 147篇 |
2009年 | 129篇 |
2008年 | 166篇 |
2007年 | 183篇 |
2006年 | 138篇 |
2005年 | 142篇 |
2004年 | 138篇 |
2003年 | 117篇 |
2002年 | 111篇 |
2001年 | 28篇 |
2000年 | 20篇 |
1999年 | 20篇 |
1998年 | 31篇 |
1997年 | 24篇 |
1996年 | 17篇 |
1995年 | 24篇 |
1994年 | 17篇 |
1993年 | 13篇 |
1992年 | 16篇 |
1991年 | 19篇 |
1990年 | 10篇 |
1989年 | 12篇 |
1988年 | 6篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 9篇 |
1984年 | 6篇 |
1983年 | 12篇 |
1982年 | 10篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 9篇 |
1975年 | 6篇 |
1974年 | 6篇 |
1971年 | 5篇 |
排序方式: 共有2878条查询结果,搜索用时 703 毫秒
21.
Xavier Khawaja Non Evans Yvonne Reilly Christine Ennis Michael C. W. Minchin 《Journal of neurochemistry》1995,64(6):2716-2726
Abstract: The specific binding of [3H]WAY-100635 {N-[2-[4-(2-[O-methyl-3H]methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohexane carboxamide trihydrochloride} to rat hippocampal membrane preparations was time, temperature, and tissue concentration dependent. The rates of [3H]WAY-100635 association (k+1 = 0.069 ± 0.015 nM?1 min?1) and dissociation (k?1 = 0.023 ± 0.001 min?1) followed monoexponential kinetics. Saturation binding isotherms of [3H]WAY-100635 exhibited a single class of recognition site with an affinity of 0.37 ± 0.051 nM and a maximal binding capacity (Bmax) of 312 ± 12 fmol/mg of protein. The maximal number of binding sites labelled by [3H]WAY-100635 was ~36% higher compared with that of 8-hydroxy-2-(di-n-[3H]-propylamino)tetralin ([3H]8-OH-DPAT). The binding affinity of [3H]WAY-100635 was significantly lowered by the divalent cations CaCl2 (2.5-fold; p < 0.02) and MnCl2 (3.6-fold; p < 0.05), with no effect on Bmax. Guanyl nucleotides failed to influence the KD and Bmax parameters of [3H]WAY-100635 binding to 5-HT1A receptors. The pharmacological binding profile of [3H]WAY-100635 was closely correlated with that of [3H]8-OH-DPAT, which is consistent with the labelling of 5-hydroxytryptamine1A (5-HT1A) sites in rat hippocampus. [3H]WAY-100635 competition curves with 5-HT1A agonists and partial agonists were best resolved into high- and low-affinity binding components, whereas antagonists were best described by a one-site binding model. In the presence of 50 µM guanosine 5′-O-(3-thiotriphosphate) (GTPγS), competition curves for the antagonists remained unaltered, whereas the agonist and partial agonist curves were shifted to the right, reflecting an influence of G protein coupling on agonist versus antagonist binding to the 5-HT1A receptor. However, a residual (16 ± 2%) high-affinity agonist binding component was still apparent in the presence of GTPγS, indicating the existence of GTP-insensitive sites. 相似文献
22.
Yvonne M. van Houten Pam van Stratum Jan Bruin Alfred Veerman 《Entomologia Experimentalis et Applicata》1995,77(3):289-295
In Europe and North America the western flower thrips,Frankliniella occidentalis, is an important pest in various greenhouse crops, such as sweet pepper and cucumber. Two species of predatory mite are commercially
applied for biological control of this pest:Amblyseius cucumeris andA. barkeri. Thrips control is generally successful from March onwards. During winter, however, thrips control by these predatory mites
is less effective. An important reason for this is that the commercially applied strains of both mite species enter reproductive
diapause under short-day photoperiods, whereas the western flower thrips does not enter diapause. In this paper we report
on selection experiments for non-diapause in strains of both mite species, aimed at obtaining predators that do not enter
diapause under light- and temperature conditions prevailing in winter. Additional experiments were done to estimate the potential
of the selected lines as control agents ofF. occidentalis. Selection for non-diapause proved highly successful in both predatory mite species. In a New Zealand strain ofA. cucumeris diapause incidence decreased from 41% to 0% in about ten generations; in a Dutch strain ofA. barkeri diapause incidence decreased from 67% to 0% in about six generations. Furthermore, selection for non-diapause had no influence
on predator performance, measured as predation rate and oviposition rate on a diet of first instar thirps larvae. Rates of
predation and oviposition were the same for selected and unselected lines in both species; rates of predation and oviposition
were higher forA. cucumeris than forA. barkeri. After 18 months under non-diapause conditions, no less than 92% of a sample of the selected non-diapause line ofA. cucumeris did not enter diapause when tested under diapause-inducing conditions. This indicates that ‘non-diapause’ is a stable trait
in these predatory mites. Finally, a small-scale greenhouse experiment in a sweet pepper crop showed that the selected non-diapause
line ofA. cucumeris established successfully under diapause-inducing short-day conditions. 相似文献
23.
Distribution and Subcellular Localization of High-Molecular-Weight Microtubule-Associated Protein-2 Expressing Exon 8 in Brain and Spinal Cord 总被引:1,自引:0,他引:1
Bridget Shafit-Zagardo Nellie Kalcheva Dennis Dickson †Peter Davies Yvonne Kress 《Journal of neurochemistry》1997,68(2):862-873
Abstract: The expression of high-molecular-weight (HMW) microtubule-associated protein-2 (MAP-2) expressing exon 8 (MAP-2+8) was examined by immunoblotting during rat brain development and in sections of human CNS. In rat brain, HMW MAP-2+8 expression was detected at embryonic day 21 and increased during postnatal development. In adult rats, HMW MAP-2+8 comigrated with MAP-2a. In human adult brain, HMW MAP-2+8 was expressed in select neuronal populations, including pyramidal neurons of layers III and V of the neocortex and parahippocampal cortex, pyramidal neurons in the endplate, CA2 and subiculum of the hippocampus, and the medium-sized neurons of the basal ganglia. In the cerebellum, a subpopulation of Golgi neurons in the internal granular cell layer and most Purkinje cells were also stained. In the spinal cord staining was observed in large neurons of the anterior horn. Staining was present in cell bodies and dendrites but not in axons. At the ultra-structural level, HMW MAP-2+8 immunoreactivity was observed on mitochondrial membranes and in postsynaptic densities (PSDs) of some asymmetric synapses in the midfrontal cortex and spinal cord. Immunoblots of proteins isolated from enriched mitochondrial and PSD fractions from adult human frontal lobe and rat brains confirmed the presence of HMW MAP-2+8. The presence of HMW MAP-2+8 in dendrites and in close proximity to PSDs supports a role in structural and functional attributes of select excitatory CNS synapses. 相似文献
24.
Freeman Bradley D.; Quezado Zenaide; Zeni Fabrice; Natanson Charles; Danner Robert L.; Banks Steven; Quezado Marcello; Fitz Yvonne; Bacher John; Eichacker Peter Q. 《Journal of applied physiology》1997,83(5):1467-1475
Freeman, Bradley D., Zenaide Quezado, Fabrice Zeni, CharlesNatanson, Robert L. Danner, Steven Banks, Marcello Quezado, YvonneFitz, John Bacher, and Peter Q. Eichacker. rG-CSF reduces endotoxemia and improves survival during E. coli pneumonia. J. Appl.Physiol. 83(5): 1467-1475, 1997.We investigatedthe effects of recombinant granulocyte colony-stimulating factor(rG-CSF) during canine bacterial pneumonia. Beagles with chronictracheostomies received daily subcutaneous rG-CSF (5 µg/kg body wt)or placebo for 14 days, beginning 9 days before intrabronchialinoculation with E. coli. Animalsreceived antibiotics and fluid support; a subset received humidifiedoxygen (fractional inspired O20.40). Compared with controls, rG-CSF increased circulating neutrophil counts (57.4 vs. 11.0 × 103/mm3,day 1 after infection;P = 0.0001), decreased plasmaendotoxin (7.5 vs. 1.1 EU/ml at 8 h; P < 0.01) and serum tumor necrosis factor- (3,402 vs.729 pg/ml at 2 h; P = 0.01) levels,and prolonged survival (relative risk of death = 0.45, 95% confidenceinterval 0.21-0.97; P = 0.038).Also, rG-CSF attenuated sepsis-associated myocardial dysfunction(P < 0.001). rG-CSF had no effect onpulmonary function or on blood and lung bacteria counts (allP = not significant). Other animalschallenged with endotoxin (4 mg/kg iv) after similar treatment withrG-CSF had lower serum endotoxin levels (7.62 vs. 5.81 log EU/ml at 6 h; P < 0.01) and less cardiovasculardysfunction (P < 0.05 to < 0.002)but similar tumor necrosis factor- levels (P = not significant) compared withcontrols. Thus prophylactic rG-CSF sufficient to increase circulatingneutrophils during bacterial pneumonia may improve cardiovascularfunction and survival by mechanisms that in part enhance the clearanceof bacterial toxins but do not improve lung function. 相似文献
25.
Stamatina E. Ziemba Shani Saks Yvonne Janviriya Robert S. Stephenson 《Cell and tissue research》1995,280(2):473-477
Photoreceptor cells that were mostly free of extracellular material and suitable for most electrophysiological study procedures were dissociated from whole heads of the fruit fly, Drosophila melanogaster, by a simple smash technique employing gentle chopping by a razor blade through Parafilm sheets. A variety of commonly available proteolytic and glycolytic digestion enzymes were tested as additions to the basic dissociation procedure described. With the aid of Nomarski interference contrast optics, periodic acid-Schiff staining, and fluorescent labeling and microscopy methods, it was determined that proteolytic enzymatic digestion does little to enhance the dissociation procedure, and instead, often damages the cells that one is attempting to recover. Unexpectedly, certain glycolytic enzymes, when added to the basic procedure, appear to enhance the recovery of intact viable Drosophila photoreceptors that are stripped of most extracellular material. Based on these results, a hypothesis concerning the biochemical nature of the extracellular matrix of the Drosophila retina is proposed. Drosophila photoreceptors are an interesting model system for the study of invertebrate phototransduction and photoreceptor cell biology because of their many well-characterized mutant strains. The technique described here should produce clean viable photoreceptors or ommatidia that respond to light, and that are suitable for patch clamping or cell culture. 相似文献
26.
M. Rita I. Young Joe Ihm Yvonne Lozano Mark A. Wright M. Margaret Prechel 《Cancer immunology, immunotherapy : CII》1995,41(1):37-45
Metastatic Lewis lung carcinoma (LLC-LN7) tumors that secrete granulocyte/macrophage-colonystimulating factor (GM-CSF) stimulate myelopoiesis and induce bone marrow-derived immunosuppressor cells that are homologous to granulocyte/macrophage progenitor cells. In vitro treatment of the LLC-LN7 cells with 1,25-dihydroxyvitamin D3 reduced tumor cell production of suppressor-inducing activity, although suppressor-inducing activity could be restored by reconstituting the tumor supernatants with recombinant GM-CSF. Treatment of mice having LLC-LN7 tumors with vitamin D3 reduced tumor production of GM-CSF and the frequency of myeloid progenitor cells. This was associated with a reduction in immunosuppressor activity and an increase in T cell function. Vitamin D3 treatment of mice having palpable tumors transiently retarded tumor growth, but caused a prominent reduction in tumor metastasis. Treating mice with vitamin D3 after tumor excision resulted in a reduction in the tumor-induced myelopoietic stimulation and associated immunosuppressive activity, and enhanced T cell function. These mice had a markedly reduced incidence of tumor recurrence. The results of this study suggest that vitamin D3 treatment of mice with GM-CSF-secreting tumors can interrupt the myelopoiesis-associated immunosuppressor cascade and, in turn, reduce tumor metastasis and recurrence.This study was supported in part by grants from the Medical Research Service of the Department of Veterans Affairs and by grants CA-45080 and CA-48080 from the National Institutes of Health 相似文献
27.
The Drosophila runt gene, which controls early events in embryogenesis, has been shown to have homologues in human and mouse. The human gene on 21q22 is involved in the t(8;21) associated with acute myeloid leukemia. Two mouse runt-like loci encoding DNA-binding proteins have been identified. We report here the isolation and partial sequence of a molecular clone of a third mouse runt-like locus. By using a panel of somatic cell hybrids and interspecific backcross mice, we map the novel locus to the telomeric region of mouse chromosome 4. 相似文献
28.
29.
B. Collet L. Dazord J. Portoukalian F. Sauvager A. Ruffault C. David 《Cancer immunology, immunotherapy : CII》1983,14(3):207-208
A heat-inactivated rough mutant of B. abortus increased resistance to a transplantable lymphoma when cultured on solid agar (ag) but not when cultured on a fluid medium (fl). The ag organisms were smaller, more toxic and induced more interferon 2 h after injection than fl. They also contained a phospholipid (cardiolipin) absent from fl preparations. 相似文献
30.
A cluster of genes encoding the three cytoplasmic carbonic anhydrase isozymes CAI, CAII, and CAIII lie on the long arm of chromosome 8 (8q22) in humans. These genes have been mapped using pulsed-field gel electrophoresis. The genes lie in the order CA2, CA3, CA1. CA2 and CA3 are separated by 20 kb and are transcribed in the same direction, away from CA1. CA1 is separated from CA3 by over 80 kb and is transcribed in the direction opposite to CA2 and CA3. The arrangement of the genes is consistent with proposals that the duplication event which gave rise to CA1 predated the duplication which gave rise to CA2 and CA3. The order of these three genes differs from that suggested for the mouse based on recombination frequency. 相似文献