全文获取类型
收费全文 | 1300篇 |
免费 | 60篇 |
出版年
2021年 | 12篇 |
2020年 | 7篇 |
2019年 | 5篇 |
2018年 | 12篇 |
2017年 | 12篇 |
2016年 | 17篇 |
2015年 | 35篇 |
2014年 | 36篇 |
2013年 | 139篇 |
2012年 | 44篇 |
2011年 | 58篇 |
2010年 | 36篇 |
2009年 | 42篇 |
2008年 | 64篇 |
2007年 | 80篇 |
2006年 | 68篇 |
2005年 | 75篇 |
2004年 | 74篇 |
2003年 | 57篇 |
2002年 | 79篇 |
2001年 | 18篇 |
2000年 | 12篇 |
1999年 | 14篇 |
1998年 | 13篇 |
1997年 | 7篇 |
1996年 | 12篇 |
1995年 | 11篇 |
1994年 | 12篇 |
1993年 | 20篇 |
1992年 | 17篇 |
1991年 | 13篇 |
1990年 | 20篇 |
1989年 | 24篇 |
1988年 | 18篇 |
1987年 | 17篇 |
1986年 | 13篇 |
1985年 | 14篇 |
1984年 | 27篇 |
1983年 | 18篇 |
1982年 | 10篇 |
1981年 | 13篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1978年 | 11篇 |
1976年 | 8篇 |
1975年 | 6篇 |
1974年 | 6篇 |
1973年 | 6篇 |
1967年 | 5篇 |
1961年 | 4篇 |
排序方式: 共有1360条查询结果,搜索用时 15 毫秒
941.
Chida T Sawabe E Ono E Nishiyama H Ebina K Sato K Watanabe Y Kuroki T Okamura N 《Microbiology and immunology》2005,49(7):663-665
None of the 58 Moraxella catarrhalis strains grew on nutrient agar without sodium chloride supplementation, whereas 49 of 51 commensal Neisseria spp. strains tested did. Growth on nutrient agar without sodium chloride supplementation could be used for screening between M. catarrhalis and commensal Neisseria spp. 相似文献
942.
Tadao Asami Yong Ki Min Sun Young Han Nobutaka Kitahata Keimei Oh Noboru Murofushi Shigeo Yoshida 《Plant Growth Regulation》2002,38(3):237-241
The preparation of new compounds for exploring the molecular andbiochemical mechanisms of abscisic acid signal perception is described. The4-carbonyl group of abscisic acid was replaced with either benzyloxy orn-octyloxy groups. Both modified products possessedABA-like activity in bioassays using barley aleurone protoplasts. The benzyloxyderivative was active in dehydrin induction tests, but not in inhibition of-amylase induction tests. The difference in the activity of this chemical inthe two assay systems suggests that the perception system for the inhibition ofamylase induction systems differs from that of dehydrin induction. 相似文献
943.
Sexual difference in buccal morphology of the paternal mouthbrooding cardinalfish Apogon doederleini
The buccal morphology was compared between the sexes of the cardinalfish Apogon doederleini, in which males provide mouthbrooding. The brood size increased proportionally with male buccal space, which increased with the fourth power of the standard length. In the breeding season, males had a larger buccal space than females, whereas there was no sexual difference in the non-breeding season, suggesting sexually different flexibility in the buccal morphology. In spite of a selective advantage to males with a larger mouth, they did not show a higher allometric growth of buccal characters or higher body growth than females. In males, the urohyal was shorter and its height to length ratio was greater than in females. This osteological modification, accompanied by depression of the lower jaw and abduction of the suspensorium, would allow males to expand their buccal cavity more effectively. 相似文献
944.
Hendrich AB Wesołowska O Komorowska M Motohashi N Michalak K 《Biophysical chemistry》2002,98(3):275-285
Using fluorescence spectroscopy, calorimetry and ESR the interactions of the phenothiazine derivative 2-trifluoromethyl-10-(4-[methylsulfonylamid]buthyl)-phenothiazine (FPhMS) with lipids were studied. Calorimetry showed biphasic effect of FPhMS on main phase transition of DPPC. At molar ratios up to 0.06 drug induced decrease of transition temperature and enthalpy, while at higher concentrations it caused subsequent increase of these parameters. For all concentrations studied we observed gradual broadening of transition peaks. Fluorescence polarization revealed that in FPhMS/lipid mixtures, order in bilayers is decreased in the gel state and increased in the liquid crystalline state. ESR experiment showed that at molar ratio of 0.06, FPhMS reduces the mobility of spin probes located in both polar and hydrophobic regions. Comparing observed effects with those reported for cholesterol/lipid mixtures, we conclude that at higher concentrations FPhMS presumably induces a new mode of bilayer packing. This structure is less co-operative than an unperturbed bilayer, but locally the mobility of lipid molecules is decreased. 相似文献
945.
Background
When there are no strand-specific biases in mutation and selection rates (that is, in the substitution rates) between the two strands of DNA, the average nucleotide composition is theoretically expected to be A = T and G = C within each strand. Deviations from these equalities are therefore evidence for an asymmetry in selection and/or mutation between the two strands. By focusing on weakly selected regions that could be oriented with respect to replication in 43 out of 51 completely sequenced bacterial chromosomes, we have been able to detect asymmetric directional mutation pressures.Results
Most of the 43 chromosomes were found to be relatively enriched in G over C and T over A, and slightly depleted in G+C, in their weakly selected positions (intergenic regions and third codon positions) in the leading strand compared with the lagging strand. Deviations from A = T and G = C were highly correlated between third codon positions and intergenic regions, with a lower degree of deviation in intergenic regions, and were not correlated with overall genomic G+C content.Conclusions
During the course of bacterial chromosome evolution, the effects of asymmetric directional mutation pressures are commonly observed in weakly selected positions. The degree of deviation from equality is highly variable among species, and within species is higher in third codon positions than in intergenic regions. The orientation of these effects is almost universal and is compatible in most cases with the hypothesis of an excess of cytosine deamination in the single-stranded state during DNA replication. However, the variation in G+C content between species is influenced by factors other than asymmetric mutation pressure.946.
947.
Ogata Y Sakurai T Nakao S Kuboyama N Moriwaki K Furuyama S Sugiya H 《Comparative biochemistry and physiology. Toxicology & pharmacology : CBP》2002,131(3):315-322
4-Bromophenacyl bromide (BPB) is generally used as a phospholipase A(2) (PLA2) inhibitor. In the present study, we demonstrate that BPB induces Ca2+ influx in human gingival fibroblasts. In fura-2-loaded human gingival fibroblasts, BPB evoked a transient increase in intracellular Ca2+ concentration ([Ca2+]i) in a dose-dependent manner. The BPB-induced Ca2+ mobilization was also shown in a single fluo-3-loaded-fibroblast. The BPB-induced increase in [Ca2+]i was completely abolished by the elimination of the external Ca2+. Ca2+ influx induced by the Ca2+-mobilizing agonist histamine was markedly enhanced in the presence of BPB. These suggest that the BPB-induced Ca2+ mobilization is due to the influx of extracellular Ca2+. However, it is unlikely that the effect of BPB is dependent on the inhibition of PLA2 activity, because other PLA2 inhibitors, such as AACOCF3, quinacrine dihydrochloride and manoalide, failed to induce Ca2+ mobilization. Chemical compounds similar to BPB, but which have no -CH2-Br at position 1 in the benzene ring failed to evoke Ca2+ mobilization, indicating that the position of -CH2--Br in BPB is important for causing the Ca2+ influx. 相似文献
948.
Female spawning strategy in Rhinogobius sp. OR: how do females deposit their eggs in the nest? 总被引:1,自引:1,他引:0
We tried to elucidate how females of a paternal nest brooding goby Rhinogohius sp. OR deposit their eggs in a nest, using a marking technique for live eggs under laboratory conditions in which male somatic
condition, nest space, and mating pattern (monogamous or bigamous) were controlled. Whether females rejected mating was independent
of either male quality, such as body size and somatic condition, or nest space. In a situation in which two females were allowed
to spawn sequentially with a male, however, females rejected mating at a higher rate when they were the first to spawn than
when they were the second to spawn; this is because eggs from first females were more vulnerable to cannibalism by parental
males and second females. Even when nest space was limited and thus was occupied by eggs from the first females, second females
could deposit all their eggs in the nest by using the minute interspace of existing eggs. In the presence of the parental
male, such a female seemed less likely to suffer a cost from increased egg mortality due to crowdedness, still holding the
advantage of being the second spawner. Finally, we extrapolated the field breeding ecology of this fish from the laboratory
data. It was suggested that a single monolayer brood of the same age usually consisted of eggs from multiple females and thus
the mating pattern would be more polygynous than previously expected.
Received: March 6, 2002 / Revised: July 11, 2002 / Accepted: August 14, 2002
RID="*"
ID="*" Present address: Center for Marine Environmental Studies, Ehime University, 3 Bunkyo-cho, Matsuyama 790-8577, Japan
(e-mail: nokuda@sci.ehime-u.ac.jp)
Acknowledgments I am grateful to S. Sone and D. Takahashi for giving us useful information and to M. Inoue and H. Miyatake for their field
assistance. This study was financially supported by Research Fellowships of the Japan Society for the Promotion of Science
for Young Scientists.
Correspondence to:Noboru Okuda 相似文献
949.
Sisson TH Hanson KE Subbotina N Patwardhan A Hattori N Simon RH 《American journal of physiology. Lung cellular and molecular physiology》2002,283(5):L1023-L1032
Plasminogen activator inhibitor-1 (PAI-1)-deficient transgenic mice have improved survival and less fibrosis after intratracheal bleomycin instillation. We hypothesize that PAI-1 deficiency limits scarring through unopposed plasminogen activation. If this is indeed true, then we would expect increased urokinase-type plasminogen activator (uPA) expression to result in a similar reduction in scarring and improvement in mortality. To test our hypothesis, using the tetracycline gene regulatory system, we have generated a transgenic mouse model with the features of inducible, lung-specific uPA production. After doxycycline administration, these transgenic animals expressed increased levels of uPA in their bronchoalveolar lavage (BAL) fluid that accelerated intrapulmonary fibrin clearance. Importantly, this increased plasminogen activator production led to a reduction in both lung collagen accumulation and mortality after bleomycin-induced injury. These results suggest that PAI-1 deficiency does protect against the effects of bleomycin-induced lung injury through unopposed plasmin generation. By allowing the manipulation of plasminogen activation at different phases of the fibrotic process, this model will serve as a powerful tool in further investigations into the pathogenesis of pulmonary fibrosis. 相似文献
950.
Arak Y Andoh A Fujiyama Y Hata K Makino J Shimada M Bamba H Okuno T Urushiyama N Bamba T 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2002,766(2):351-356
In a previous study, we reported a novel method for the separation and quantification of a strong negatively charged material, dextran sulfate sodium (DSS), using fluorometric labeling with 2-aminopyridine and size-exclusion high-performance liquid chromatography. In the present study, we developed a method for the separation of pyridylamino-DSS (PA-DSS) using reversed-phase high-performance liquid chromatography (RPLC). In vitro enzymatic degradation of the PA-DSS was carried out using alpha-amylase. In RPLC, depolymerized PA-DSS was eluted on the basis of molecular mass (in the order pentamer, trimer, dimer, and monomer of PA-DSS) and separations were more sharply than in size-exclusion chromatography. The combination of RPLC and size-exclusion chromatography also separated depolymerized PA-DSS as effectively as RPLC alone. 相似文献