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91.
《Bioorganic & medicinal chemistry》2014,22(4):1377-1382
Our previous studies indicated that 111In-diethylenetriaminepentaacetic acid (111In-DTPA)-octreotide derivatives with an additional negative charge by replacing N-terminal d-phenylalanine (d-Phe) with an acidic amino acid such as l-aspartic acid (Asp) or its derivative exhibited low renal radioactivity levels when compared with 111In-DTPA-d-Phe1-octreotide. On the basis of the findings, we designed, synthesized and evaluated two Asp-modified 111In-DTPA-conjugated octreotide derivatives, 111In-DTPA-Asp1-octreotide and 111In-DTPA-Asp0-d-Phe1-octreotide. While 111In-DTPA-Asp1-octreotide showed negligible AR42J cell uptake, 111In-DTPA-Asp0-d-Phe1-octreotide exhibited AR42J cell uptake similar to that of 111In-DTPA-d-Phe1-octreotide. When administered to AR42J tumor-bearing mice, 111In-DTPA-Asp0-d-Phe1-octreotide exhibited renal radioactivity levels significantly lower than did 111In-DTPA-d-Phe1-octreotide at 1 and 3 h post-injection. No significant differences were observed in tumor accumulation between 111In-DTPA-Asp0-d-Phe1-octreotide and 111In-DTPA-d-Phe1-octreotide after 1 and 3 h injection. The findings in this study suggested that an interposition of an Asp at an appropriate position in 111In-DTPA-d-Phe1-octreotide would constitute a useful strategy to develop 111In-DTPA-d-Phe1-octreotide derivatives of low renal radioactivity levels while preserving tumor accumulation. 相似文献
92.
Forty normal-achieving and 33 learning disabled (LD) children were assigned randomly to either a negative ion or placebo test condition. On a dichotic listening task using consonant-vowel (CV) combinations, both groups showed an ioninduced increase in the normal right ear advantage (REA). However, the mechanisms for this effect were different for each group. The LDs showed the effect at the right ear/left hemisphere (enhancement). The normal achievers showed the effect at the left ear/right hemisphere (inhibition). The results are consistent with an activation-inhibition model of cerebral function and suggest a functional relationship between arousal, interhemispheric activation-inhibition, and learning disabilities. The LDs may have an interhemispheric dysfunction. Both groups showed superior right ear report and the normal achiever showed overall superiority. Normal achievers showed higher consonant intrusion scores, probably due to a greater cognitive capacity. Age was a significant covariate reflecting developmental capacity changes. Negative air ions are seen to be a tool with potential theoretical and remedial applications. 相似文献
93.
K. Ibara H. Kawate L. -L. Chueh H. Hayakawa M. Sekiguchi 《Molecular & general genetics : MGG》1994,243(4):379-389
O6-Methylguanine-DNA methyltransferase catalyzes transfer of a methyl group from O6-methylguanine and O4-methylthymine of DNA to a cysteine residue of the enzyme protein, thereby repairing the mutagenic and carcinogenic lesions in a single-step reaction. There are highly conserved amino acid sequences around the methyl-accepting cysteine site in eleven molecular species of methyltransferases. To elucidate the significance of the conserved sequence, amino acid substitutions were introduced by site-directed mutagenesis of the cloned DNA for Escherichia coli Ogt methyltransferase, and the activity and stability of mutant forms of the enzyme were examined. When cysteine-139, to which methyl transfer occurs, was replaced by other amino acids, all of the mutants showed the methyltransferase-negative phenotype. Methyltransferase-positive revertants, isolated from one of the negative mutants, had restored codons for cysteine. Thus the cysteine residue is essential for acceptance of the methyl group and is not replaceable by other amino acids. Using this negative and positive selection procedure, the analysis was extended to other residues near the acceptor site. At the histidine-140 and arginine-141 sites, all the positive revertants isolated carried codons for amino acids identical to those of the wild-type protein. At proline-138, five substitutions (serine, glutamine, threonine, histidine, and alanine) exhibited the positive phenotype but levels of methyltransferase activity in extracts of cells harboring these mutant forms were very low. This suggests that the proline residue at this site is important for maintaining the proper conformation of the protein. With valine-142 substitutions there were seven types of positive revertants, among which mutants carrying isoleucine, cysteine, leucine, and alanine showed relatively high levels of methyltransferase activity. These results indicate that the sequence Pro-Cys-His-Arg is a sine qua non for methyltransferase to exert its function. 相似文献
94.
Summary We present some data on drosophilid oviposition and analyse the distribution of egg numbers over patches using an iterated negative binomial. This suggests that there are three different reasons for empty patches; patches are not found, patches are not suitable, or females are not able to lay eggs. This leads to five categories of site which can be disentangled using the iterated negative binomial. Since empty patches have important consequences for population dynamics and coexistence, this analysis will highlight how microscopic processes influence macroscopic behaviour in population biology. 相似文献
95.
空气负离子对自发和环磷酰胺诱发的小鼠骨髓嗜多染性成红细胞微核率的影响 总被引:2,自引:0,他引:2
我们以前的研究表明负离子对~(60)Co-γ线诱发的急性和慢性损伤有明显的防护作用。本文以小鼠骨髓嗜多染性成红细胞(PCE)微核率为指标,探讨负离子对正常小鼠有无细胞毒性和对环磷酰胺(CP)诱发的遗传损伤有无防护作用。用负离子处理昆明小鼠60天后不注射CP直接取样;用负离子分别处理小鼠15天、30天和60天后注射CP,6小时后取样。镜检骨髓PCE微核并做统计处理。结果表明,负离子促进小鼠的生长发育且不导致潜在损伤;负离子对CP诱发的遗传损伤有明显的防护作用。 相似文献
96.
负二项分布与昆虫种群空间格局分析的研究现状 总被引:3,自引:0,他引:3
对农业有害生物及其天敌种群密度的正确估计是实施IPM(有害生物综合治理)方案的先决条件,因此,抽样方法一直被列为昆虫学,生态学和植物保护科学中最重要的基本 相似文献
97.
Disha M. Gandhi Mark W. Majewski Ricardo Rosas Kaitlin Kentala Trevor J. Foster Eric Greve Chris Dockendorff 《Bioorganic & medicinal chemistry》2018,26(9):2514-2529
Several classes of ligands for Protease-Activated Receptors (PARs) have shown impressive anti-inflammatory and cytoprotective activities, including PAR2 antagonists and the PAR1-targeting parmodulins. In order to support medicinal chemistry studies with hundreds of compounds and to perform detailed mode-of-action studies, it became important to develop a reliable PAR assay that is operational with endothelial cells, which mediate the cytoprotective effects of interest. We report a detailed protocol for an intracellular calcium mobilization assay with adherent endothelial cells in multiwell plates that was used to study a number of known and new PAR1 and PAR2 ligands, including an alkynylated version of the PAR1 antagonist RWJ-58259 that is suitable for the preparation of tagged or conjugate compounds. Using the cell line EA.hy926, it was necessary to perform media exchanges with automated liquid handling equipment in order to obtain optimal and reproducible antagonist concentration-response curves. The assay is also suitable for study of PAR2 ligands; a peptide antagonist reported by Fairlie was synthesized and found to inhibit PAR2 in a manner consistent with reports using epithelial cells. The assay was used to confirm that vorapaxar acts as an irreversible antagonist of PAR1 in endothelium, and parmodulin 2 (ML161) and the related parmodulin RR-90 were found to inhibit PAR1 reversibly, in a manner consistent with negative allosteric modulation. 相似文献
98.
Tetsuya Akita 《Population Ecology》2018,60(4):297-308
In this paper, we develop a theory of a new statistic that tests overdispersion in offspring number on the basis of exactly known kinship relationships. The statistic utilizes the sample size and the number of kinship pairs found in a sample, specially the number of mother–offspring (MO) and maternal–half-sibling (MHS) pairs. Given a sufficiently large sample size, the statistic proposed in this paper approximately follows a standard-normal distribution under non-overdispersed conditions (Poisson’s variance). We found that (1) the value of the statistic (\(\ge 2\) or \(<2\)) reasonably indicates whether reproduction is overdispersed at the 5% significance level; (2) the power of the statistic is determined primarily by the balance between the degree of overdispersion and the sample size; (3) in many cases, if the number of kinship pairs can be approximated by a normal distribution, false-positive and false-negative situations can be avoided. The proposed method can detect moderate-weak levels of overdispersion that produce few MHS pairs in a sample because the effect of the population size (which determines the number of detected MHS pairs) is canceled by the detection of the number of MO pairs. Once the kinship determination procedure is established, this indirect measurement will be readily applicable to species even with weak overdispersion, expanding the available opportunities for understanding how overdispersion in offspring number affects ecological processes. 相似文献
99.
杭州郊区菜蚜种群的空间动态 总被引:4,自引:1,他引:3
利用 1 990~ 1 992年杭州郊区菜区 1 0茬结球甘蓝、2 3茬小白菜上菜蚜种群的系统调查数据 ,选择受密度影响较小的负二项分布的K值 ,描述了菜蚜混生种群的空间格局及其时序动态 .2类蔬菜上桃蚜、萝卜蚜混生种群终年呈聚集分布 ,但聚集强度变化有明显的季节规律 .7~ 9月聚集度最高 ,5和 1 1月前后有 2个明显的扩散高峰 .在甘蓝作物上的聚集强度随时间的变化过程因季节而异 ,春夏季为高 低 高 ,夏秋季一直较高 ,秋冬季在年间有较大变化 ,冬春季开始由低向高变化 ,随后上下波动 .萝卜蚜的聚集度较桃蚜为高 .综合了菜蚜混生种群的数量消长规律、环境因子的变化等信息 ,对其空间图式及其时序动态特征的成因进行了讨论 . 相似文献
100.
Yosiaki Itô Masako Nakamura Masaki Kondo Kazuyoshi Miyashita Kazuo Nakamura 《Population Ecology》1962,4(1):35-46
Summary As a part of serial study on population dynamics of the chestnut gall-wasp,Dryocosmus kuriphilus, analyses of the distribution of eggs, gall-cells and emergent holes were made from the statistical point of view. Many of
distributions of the eggs per bud could be described by the truncated Poisson, but some cases showed slight overdispersion
than expected by chance. Because of no linear increase of
with increasing
(expected mean for complete sample), however, the truncated negative binomial seemed to be not so available for whole series.
Distributions of the gall-cells and the emergent holes were, on the other hand, well described by the truncated Poisson distribution
when the observed frequency was calculated for respective trees. Negative-binomial tendency found in distributions from some
stations consisted of a certain number of trees would be resulted from mixture of Poisson populations with different means.
Random or slightly concentrated oviposition and random mortality within galls was thus supposed for future study unless the
proof favouring other distribution models would appear. 相似文献