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71.
G Rapp J Mucha R Einspanier M Luck K H Scheit 《Biological chemistry Hoppe-Seyler》1988,369(4):247-250
A cDNA clone, pHGR81, encoding 358 amino-acid residues of the C-terminal region of human elongation factor 2 (EF-2), was isolated from a human ovarian granulosa cell cDNA library. The deduced amino-acid sequence of pHGR81, when compared with the known identical amino-acid sequences of hamster as well as rat EF-2 revealed a substitution of a glutamine by an alanine residue in the partially determined human sequence. The 15 amino-acid-residue sequence comprising the histidine-715, supposed to be of importance for the biological function of EF-2, is preserved in human EF-2. The coding region of the cDNA insert of pHGR81 displays a homology of 87% to hamster and of 88% to rat EF-2 cDNA. In Northern-transfer analysis, pHGR81 specifically hybridizes with an mRNA species of 3.1 kb. 相似文献
72.
A PARACRYSTALLINE INCLUSION IN NEUROSPORA CRASSA : Induction by Ethidium and Acridine, Isolation, and Characterization 总被引:1,自引:0,他引:1 下载免费PDF全文
A paracrystal indistinguishable from the one which occurs in the mitochondrial mutant abnormal-1 can be induced in wild-type Neurospora crassa after growth in either ethidium or euflavine. This paracrystal has been isolated and partially characterized. It appears to be composed of a single polypeptide (mol wt 68,000) which can be reversibly crystallized and dissociated by changes in the pH and ionic strength. When aggregated, the polypeptide forms oligomers which are arranged end-to-end into fibers. During the characterization of the polypeptide, it was found that the polypeptide's electrophoretic and immunological properties could be used as assays. Using these methods it was found that the polypeptide normally accumulates in a soluble form in the cytoplasm of wild-type Neurospora at the end of the log-phase of growth. 相似文献
73.
Protection of (dA.dT) cluster regions in the DNAase I cleavage of DNA by specific interaction with netropsin 总被引:1,自引:1,他引:0 下载免费PDF全文
The specific DNA binding ligand netropsin selectively blocks dA-dT base pairs in clusters containing two or more consecutive thymine residues at the dNAase I cleavage sites of DNA. Using CD and UV absorption measurements it is shown, that at various ratios of netropsin to nucleotide concentrations and even at satuation of ligand interaction the enzyme cuts along regions containing dG-dC pairs sandwiched between dA-dT pairs. This follows a slow kinetics and is associated with a release of netropsin from those segments. These facts suggests the usefulness of the partial protection of certain DNA sequences in DNAase I cleavage sites in producing DNA fragments in structural studies of the genome. A possible interpretation of the effect of netropsin binding on the enzymatic hydrolysis of phosphodiester bonds of the helix is discussed. 相似文献
74.
Baorong Bai Robert F. Luck Lisa Forster Beth Stephens J. A. M. Janssen 《Entomologia Experimentalis et Applicata》1992,64(1):37-48
In a study of the quality ofTrichogramma pretiosum Riley (Hymenoptera: Trichogrammidae), we compared female wasps emerging from natural hosts, parasitized in the laboratory or the field with those emerging from factitious hosts used for commercial mass production. Females from the natural hosts were larger, more fecund, and longer lived than those from the factitious hosts. Compared to small females, large female wasps are substantially more fecund when honey (carbohydrate) is available but marginally more fecund when honey is unavailable. The size of a femaleT. pretiosum depends on two factors: the size of the host egg from which it emerges even when the wasp was gregarious, and the number of conspecifics that emerge with it. The similarities in the size distribution of female wasps emerging from natural hosts, in conjunction with the mechanism by whichTrichogramma measure host size and allocate eggs accordingly, suggests the hypothesis that size related components of fitness in femaleT. pretiosum are under strong selection in the field. 相似文献
75.
Gary W. Luck Lisa Smallbone Simon McDonald Deanna Duffy 《Global Ecology and Biogeography》2010,19(5):673-683
Aim To test six hypotheses that could explain or mediate the positive correlation between human population density (HPD) and bird species richness while controlling for biased sampling effort. These hypotheses were labelled as follows: productivity (net primary productivity, NPP); inherent heterogeneity (diversity of vegetation types); anthropogenic heterogeneity (diversity of land uses); conservation policy (proportion of conservation land); increased productivity (human‐induced productivity increases); and the reduced‐slope hypothesis (which predicts that humans have a negative impact on species numbers across the full range of variation in HPD). Location Australia. Methods All data were collected at a spatial resolution of 1° across mainland Australia. Bird species richness was from 2007 atlas data and random subsampling was used to account for biased sampling effort. HPD was from the 2006 census. All other data were from government produced geographic information system layers. The most important biotic or abiotic factors influencing patterns in both species richness and HPD were assessed using simultaneous autoregressive models and an information theoretic approach. Results NPP appeared to be one of the main factors driving spatial congruence between bird species richness and HPD. Inherent habitat heterogeneity was weakly related to richness and HPD, although an interaction between heterogeneity and NPP indicated that the former may be an important determinant of species richness in low‐productivity regions. There was little evidence that anthropogenic landscape heterogeneity or human‐induced changes in productivity influenced the relationship between species richness and HPD, but conservation policy appeared to act as an important mediating factor and species richness was positively related to the proportion of conservation land only in regions of high HPD. Main conclusions The spatial congruence between bird species richness and HPD occurs because both respond positively to productivity and, in certain circumstances, habitat heterogeneity. Our results suggest that conservation policy could mediate this relationship, but further research is required to determine the importance of conservation reserves in supporting species in regions densely populated by humans. 相似文献
76.
Temperature-Sensitive, Assembly-Defective Flagella Mutants of CHLAMYDOMONAS REINHARDTII 总被引:7,自引:2,他引:7 下载免费PDF全文
We describe an efficient selection procedure for the isolation of mutants of Chlamydomonas reinhardtii with temperature sensitive flagella defects, with final yields of up to 11% of the population being mutant. Several mutants, all showing an inability to maintain flagellar integrity at the restrictive temperature, are described. We have examined flagellar stability and reassembly at various temperatures in the mutants. Mapping data are provided for these, as well as for some previously described mutants. 相似文献
77.
Ribosomal RNA synthesis in mitochondria of Neurospora crassa 总被引:10,自引:0,他引:10
Ribosomal RNA synthesis in Neurospora crassa mitochondria has been investigated by continuous labeling with [5-3H]uracil and pulse-chase experiments. A short-lived 32 S mitochondrial RNA was detected, along with two other short-lived components; one slightly larger than large subunit ribosomal RNA, and the other slightly larger than small subunit ribosomal RNA. The experiments give support to the possibility that 32 S RNA is the precursor of large and small subunit ribosomal RNA's. Both mature ribosomal RNA's compete with 32 S RNA in hybridization to mitochondrial DNA. Quantitative results from such hybridization-competition experiments along with measurements of electrophoretic mobility have been used to construct a molecular size model for synthesis of mitochondrial ribosomal RNA's. The large molecular weight precursor (32 S) of both ribosomal RNA's appears to be 2.4 × 106 daltons in size. Maturation to large subunit RNA (1.28 × 106 daltons) is assumed to involve an intermediate ~1.6 × 106 daltons in size, while cleavage to form small subunit RNA (0.72 × 106 daltons) presumably involves a 0.9 × 106 dalton intermediate. In the maturation process ~22% of the precursor molecule is lost. As is the case for ribosomal RNA's, the mitochondrial precursor RNA has a strikingly low G + C content. 相似文献
78.
The murid rodent subfamily Sigmodontinae contains 79 genera which are
distributed throughout the New World. The time of arrival of the first
sigmodontines in South America and the estimated divergence time(s) of the
different lineages of South American sigmodontines have been controversial
due to the lack of a good fossil record and the immense number of extant
species. The "early-arrival hypothesis" states that the sigmodontines must
have arrived in South America no later than the early Miocene, at least 20
MYA, in order to account for their vast present-day diversity, whereas the
"late-arrival hypothesis" includes the sigmodontines as part of the
Plio-Pleistocene Great American Interchange, which occurred approximately
3.5 MYA. The phylogenetic relationships among 33 of these genera were
reconstructed using mitochondrial DNA (mtDNA) sequence data from the ND3,
ND4L, arginine tRNA, and ND4 genes, which we show to be evolving at the
same rate. A molecular clock was calibrated for these genes using published
fossil dates, and the genetic distances were estimated from the DNA
sequences in this study. The molecular clock was used to estimate the dates
of the South American sigmodontine origin and the main sigmodontine
radiation in order to evaluate the "early-" and "late-arrival" scenarios.
We estimate the time of the sigmodontine invasion of South America as
between approximately 5 and 9 MYA, supporting neither of the scenarios but
suggesting two possible models in which the invading lineage was either (1)
ancestral to the oryzomyines, akodonts, and phyllotines or (2) ancestral to
the akodonts and phyllotines and accompanied by the oryzomyines. The
sigmodontine invasion of South America provides an example of the advantage
afforded to a lineage by the fortuitous invasion of a previously
unexploited habitat, in this case an entire continent.
相似文献
79.
Thorsten Mosler H Irem Baymaz Justus F Grf Ivan Mikicic Georges Blattner Edward Bartlett Matthias Ostermaier Rossana Piccinno Jiwen Yang Andrea Voigt Marco Gatti Stefania Pellegrino Matthias Altmeyer Katja Luck Ivan Ahel Vassilis Roukos Petra Beli 《Nucleic acids research》2022,50(20):11600
PARP1 mediates poly-ADP-ribosylation of proteins on chromatin in response to different types of DNA lesions. PARP inhibitors are used for the treatment of BRCA1/2-deficient breast, ovarian, and prostate cancer. Loss of DNA replication fork protection is proposed as one mechanism that contributes to the vulnerability of BRCA1/2-deficient cells to PARP inhibitors. However, the mechanisms that regulate PARP1 activity at stressed replication forks remain poorly understood. Here, we performed proximity proteomics of PARP1 and isolation of proteins on stressed replication forks to map putative PARP1 regulators. We identified TPX2 as a direct PARP1-binding protein that regulates the auto-ADP-ribosylation activity of PARP1. TPX2 interacts with DNA damage response proteins and promotes homology-directed repair of DNA double-strand breaks. Moreover, TPX2 mRNA levels are increased in BRCA1/2-mutated breast and prostate cancers, and high TPX2 expression levels correlate with the sensitivity of cancer cells to PARP-trapping inhibitors. We propose that TPX2 confers a mitosis-independent function in the cellular response to replication stress by interacting with PARP1. 相似文献
80.