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971.
Identification of mutations in Caenorhabditis elegans that cause resistance to high levels of dietary zinc and analysis using a genomewide map of single nucleotide polymorphisms scored by pyrosequencing 总被引:1,自引:0,他引:1
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Zinc plays many critical roles in biological systems: zinc bound to proteins has structural and catalytic functions, and zinc is proposed to act as a signaling molecule. Because zinc deficiency and excess result in toxicity, animals have evolved sophisticated mechanisms for zinc metabolism and homeostasis. However, these mechanisms remain poorly defined. To identify genes involved in zinc metabolism, we conducted a forward genetic screen for chemically induced mutations that cause Caenorhabditis elegans to be resistant to high levels of dietary zinc. Nineteen mutations that confer significant resistance to supplemental dietary zinc were identified. To determine the map positions of these mutations, we developed a genomewide map of single nucleotide polymorphisms (SNPs) that can be scored by the high-throughput method of DNA pyrosequencing. This map was used to determine the approximate chromosomal position of each mutation, and the accuracy of this approach was verified by conducting three-factor mapping experiments with mutations that cause visible phenotypes. This is a generally applicable mapping approach that can be used to position a wide variety of C. elegans mutations. The mapping experiments demonstrate that the 19 mutations identify at least three genes that, when mutated, confer resistance to toxicity caused by supplemental dietary zinc. These genes are likely to be involved in zinc metabolism, and the analysis of these genes will provide insights into mechanisms of excess zinc toxicity. 相似文献
972.
Cancer immunosurveillance failure is largely attributed to insufficient activation signals and dominant inhibitory stimuli for tumor Ag (TAg)-specific CD8 T cells. CD4 T cells have been shown to license dendritic cells (DC), thereby having the potential for converting CD8 T cell responses from tolerance to activation. To understand the potential cooperation of TAg-specific CD4 and CD8 T cells, we have characterized the responses of naive TCR transgenic CD8 and CD4 T cells to poorly immunogenic murine tumors. We found that whereas CD8 T cells sensed TAg and were tolerized, the CD4 T cells remained ignorant throughout tumor growth and did not provide help. This disparity in responses was due to normal TAg MHC class I cross-presentation by immature CD8alpha+ DC in the draining lymph node, but poor MHC class II presentation on all DC subsets due to selective inhibition by the tumor microenvironment. Thus, these results reveal a novel mechanism of cancer immunosubversion, in which inhibition of MHC-II TAg presentation on DC prevents CD4 T cell priming, thereby blocking any potential for licensing CD8alpha+ DC and helping tolerized CD8 T cells. 相似文献
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976.
Pippa Oakeshott Phillip Hay Sima Hay Frances Steinke Elizabeth Rink Sally Kerry 《BMJ (Clinical research ed.)》2002,325(7376):1334
ObjectivesTo assess whether bacterial vaginosis or chlamydial infection before 10 weeks'' gestation is associated with miscarriage before 16 weeks.DesignProspective cohort study.Setting32 general practices and five family planning clinics in south London.Participants1216 pregnant women, mean age 31, presenting before 10 weeks'' gestation.Results121 of 1214 women (10.0%, 95% confidence interval 8.3% to 11.7%) miscarried before 16 weeks. 174 of 1201 women (14.5%, 12.5% to 16.5%) had bacterial vaginosis. Compared with women who were negative for bacterial vaginosis those who were positive had a relative risk of miscarriage before 16 weeks'' gestation of 1.2 (0.7 to 1.9). Bacterial vaginosis was, however, associated with miscarriage in the second trimester at 13-15 weeks (3.5, 1.2 to 10.3). Only 29 women (2.4%, 1.5% to 3.3%) had chlamydial infection, of whom one miscarried (0.32, 0.04 to 2.30).ConclusionBacterial vaginosis is not strongly predictive of early miscarriage but may be a predictor after 13 weeks'' gestation. The prevalence of Chlamydia was too low to assess the risk, but it is unlikely to be a major risk factor in pregnant women.
What is already known on this topic
Miscarriages are common and associated with considerable morbidity and costsBacterial vaginosis is associated with miscarriage after 16 weeks'' gestation and preterm birth but the role of chlamydial infection is uncertainWhat this study adds
Bacterial vaginosis is not a strong predictor of miscarriage before 16 weeks'' gestation but may be associated with miscarriage at 13-15 weeks'' gestationThe prevalence of chlamydial infection was too low for it to be a major risk factor for miscarriage in this population of healthy pregnant womenNon-invasive screening for bacterial vaginosis and chlamydial infection by using self administered vaginal swabs is feasible in pregnant women in the community 相似文献977.
Effect of Seawater on Photosynthesis and Dry Matter Accumulation in Developing Rice Grains 总被引:1,自引:0,他引:1
To understand the physiology of rice under seawater salinity, potted rice plants were irrigated with different concentrations of Japan seawater (electrical conductivity 0.9, 5.7, 11.5, or 21.5 mS cm-1) from 10 d after transplanting (DAT) to 35 DAT, and from 75 to 100 DAT. Seawater salinity decreased the net photosynthetic rate, stomatal conductance, intercellular CO2 concentration, transpiration rate, leaf water and osmotic potentials, and relative water content, and increased leaf temperature. The contents of chlorophylls, carotenoids, and total sugars significantly decreased in the leaves but content of non-reducing sugars decreased only slightly. With increasing salinity the Na+ concentration increased, while Ca2+, Mn2+, and K+ concentrations decreased. Salinity decreased the contents of sugars and proteins, dry mass, and rate of dry mater accumulation in developing grains. 相似文献
978.
Sadasivam Murali Kerry J. Manton Vinalia Tjong Xiaodi Su Larisa M. Haupt Simon M. Cool Victor Nurcombe 《Journal of cellular biochemistry》2009,108(5):1132-1142
Heparan sulfate (HS) is a linear, highly variable, highly sulfated glycosaminoglycan sugar whose biological activity largely depends on internal sulfated domains that mediate specific binding to an extensive range of proteins. In this study we employed anion exchange chromatography, molecular sieving and enzymatic cleavage on HS fractions purified from three compartments of cultured osteoblasts—soluble conditioned media, cell surface, and extracellular matrix (ECM). We demonstrate that the composition of HS chains purified from the different compartments is structurally non‐identical by a number of parameters, and that these differences have significant ramifications for their ligand‐binding properties. The HS chains purified of conditioned medium had twice the binding affinity for FGF2 when compared with either cell surface or ECM HS. In contrast, similar binding of BMP2 to the three types of HS was observed. These results suggest that different biological compartments of cultured cells have structurally and functionally distinct HS species that help to modulate the flow of HS‐dependent factors between the ECM and the cell surface. J. Cell. Biochem. 108: 1132–1142, 2009. © 2009 Wiley‐Liss, Inc. 相似文献
979.
Rosa H. Manzanilla-López Simon D. Atkins Ian M. Clark Brian R. Kerry 《Biocontrol Science and Technology》2009,19(4):391-406
Abundance, genetic diversity and parasitic ability in the facultative nematode parasite Pochonia chlamydosporia var. chlamydosporia were compared in soils from two sites in Portugal under long-term tomato cultivation where root-knot nematodes (Meloidogyne sp.) were present. Fungal abundance assessed by selective agar or real-time quantitative PCR with specific primers was similar in both soils. PCR fingerprinting of isolates with ERIC primers indicated that the dominant P. c. var. chlamydosporia biotypes (profiles A and B) in both soils were very closely related, although a second biotype (profile C) was detected in one soil. When tomato plants infected with M. incognita were grown in the two soils, only profiles A and B were recovered from eggs. Primers based on polymorphisms in vcp1 demonstrated that isolates with profiles A and B were likely to prefer root-knot nematodes, whereas profile C preferred cyst nematodes. In the soil containing profiles A, B and C, egg parasitism by P. chlamydosporia was estimated at 1% using water agar plates with antibiotics but fewer than 0.2% of M. incognita eggs were shown to be infected with P. c. var. chlamydosporia when using species-specific β-tubulin-PCR primers. In contrast, the soil containing only profile B showed 22% egg parasitism on water agar plates and more than 2.5% of eggs were confirmed as P. c. var. chlamydosporia by species-specific β-tubulin-PCR primers. The results, which reveal limited diversity within the fungus at the two sites, are discussed in relation to biological control of plant-parasitic nematodes. 相似文献
980.
Sharon K. Huang Marlene M. Darfler Michael B. Nicholl Jinsam You Kerry G. Bemis Tony J. Tegeler Mu Wang Jean-Pierre Wery Kelly K. Chong Linhda Nguyen Richard A. Scolyer Dave S. B. Hoon 《PloS one》2009,4(2)