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排序方式: 共有575条查询结果,搜索用时 15 毫秒
91.
LL Lukash IS Karpova OS Miroshnichenko TN Tikhonova VV Lylo VG Man'ko EM Sukhorada EL Golynskaia 《Canadian Metallurgical Quarterly》1997,31(5):52-60
Data on separation of purified galactose-specific lectin as well as its two polypeptide chains from inflorescences of European elder Sambucus nigra are represented. Their molecule quaternary structure after the pattern a2 b2 is suggested. It was shown that purified protein in concentration 2.0 mg/ml had mutagenic activity and might enhance mutagenic effect of alkylating substance MNNG. Thus, preparations of lectin from inflorescences of European elder influenced on spontaneous and induced by the alkylating agent mutagenicity in mammalian somatic cells in vitro. 相似文献
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Spontaneous and nitrosoguanidine (NG)-induced rate of reversions to glutamine independence was studied in cultured temperature-sensitive glutamine auxotrophs of Chinese hamster cells. In 3 experiments the spontaneous rate of reversions varied from 0.8-10(-6) to 3.84-10(-6) per cell per generation. A dependence of the yield of NG-induced back mutations upon the time interval between the mutagenic treatment and the transfer to selective conditions (glutamine deficient medium, 40 degrees C) was established. No induced revertants were detected when cells were transferred to selective conditions immediately after the treatment with NG. After 2--3 days cultivation in glutamine containing medium at 36 degrees C and the sunsequent transfer to selective conditions the frequency of induced reversions varied from 0.56-10(-4) to 10.55-10(-4) in different experiments; after 6 days -- from 0.05-10(-4) to 4.0-10(-4). In all cases where induction was detected, the difference, between the frequency of glutamine prototrophs in treated and control plates was significant. Glutamine independence proved to be stable after prolonged cultivation under non-selective conditions, the degree of prototrophy being greatly unequal in different clones. No differnce in this respect was detected between spontaneous and NG-induced revertants. The proposed system of reverse mutations can be used for studying diverse problems of somatic cell genetics. 相似文献
95.
Bleomycin hydrolase (BH) is unusual among cysteine proteinases because it appears to form multihomomeric structures, inactivates the antitumor glycopeptide bleomycin, and contains a unique C-terminal amino acid sequence. We now demonstrate intrinsic endopeptidase activity associated with human BH (hBH) using artificial substrates and intracellular dimerization of hBH using a yeast two-hybrid assay. To determine domains important for homomeric interactions and catalysis, we constructed N- and C-terminal deletion mutants and identified an N-terminal region (hBH1-82) that interacted with two nonoverlaping hBH domains: one near the N-terminus (hBH14-103) and another neighboring the C-terminus (hBH358-455). In vitro hBH aggregated with a molecular mass of 235 kD corresponding to a homotetramer and the C-terminus was critical for this oligomerization since no tetramers were found when the last 40 amino acids were deleted. The penultimate 8 amino acids, which constitute a unique and highly conserved bleomycin hydrolase-like domain (BHYD), were essential for BH and aminopeptidase activity but not for endopeptidase activity or oligomer formation. Thus, the C-terminus of hBH has two independent roles controlling both the catalytic activity and oligomerization of hBH. 相似文献
96.
EL Anderssen DB Diep IF Nes VG Eijsink J Nissen-Meyer 《Canadian Metallurgical Quarterly》1998,64(6):2269-2272
Six bacteriocinlike peptides (plantaricin A [PlnA], PlnE, PlnF, PlnJ, PlnK, and PlnN) produced by Lactobacillus plantarum C11 were detected by amino acid sequencing and mass spectrometry. Since purification to homogeneity was problematic, all six peptides were obtained by solid-phase peptide synthesis and were tested for bacteriocin activity. It was found that L. plantarum C11 produces two two-peptide bacteriocins (PlnEF and PlnJK); a strain-specific antagonistic activity was detected at nanomolar concentrations when PlnE and PlnF were combined and when PlnJ and PlnK were combined. Complementary peptides were at least 10(3) times more active when they were combined than when they were present individually, and optimal activity was obtained when the complementary peptides were present in approximately equal amounts. The interaction between complementary peptides was specific, since neither PlnE nor PlnF could complement PlnJ or PlnK, and none of these peptides could complement the peptides constituting the two-peptide bacteriocin lactococcin G. Interestingly, PlnA, which acts as an extracellular signal (pheromone) that triggers bacteriocin production, also possessed a strain-specific antagonistic activity. No bacteriocin activity could be detected for PlnN. 相似文献
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