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1.
Packing forces in ribonuclease crystals 总被引:1,自引:0,他引:1
Packing in Ribonuclease A and Ribonuclease S crystals have been compared in order to determine the possible role of the precipitant on lattice contacts. Both proteins have similar tertiary structures, but they crystallize in different space groups depending on the precipitating agent. It is found that packing differs either by the number of nearest neighbours or by the size of surface areas buried in individual contacts. Ammonium sulfate seems to promote hydrophobic interactions with interfaces similar to those found in oligomeric proteins. Organic precipitants favour electrostatic interactions. 相似文献
2.
Evidence for a novel growth factor in Xenopus oocytes 总被引:1,自引:0,他引:1
C Théry P Jullien D A Lawrence 《Biochemical and biophysical research communications》1989,160(2):615-622
Xenopus oocytes contain a novel growth factor, as determined by its effect on the anchorage-dependent and -independent growth of various rat cells and on a Xenopus cell line; it is destroyed by trypsin, acidification (pH 2.0), heating (100 degrees C, 3 min), 8 M urea but not by dithiothreitol. Gel filtration of this activity in nondissociating conditions suggests the existence of aggregates and the presence of a very high (approximately 2000 Kd) and a much lower (approximately 30 Kd) form. 相似文献
3.
A new kanamycin-resistance gene, detected in Acinetobacter baumannii and designated aphA-6, was sequenced. It specifies a 30319 Dalton 3'-aminoglycoside phosphotransferase (APH(3'] that mediates resistance to kanamycin and structurally related aminoglycosides, including amikacin. Pairwise comparisons of the six types of APH(3') so far detected in human pathogens (types I, II, III and VI) and in amino-glycoside-producing microorganisms (types IV and V), confirm that APH(3') enzymes have diverged from a common ancestor. Three highly retained motifs (1: V--HGD----N; 2: G--D-GR/K-G and 3: D--K/R--Y/F---LDE) located in the C-terminal part of the enzymes were defined. Screening of protein sequence data bases fore each of these motifs revealed that motifs 1 and 2 are both found in nucleotide-binding phosphotransferases associated with a variety of biological processes, namely adenylate kinase, viral oncogenic protein kinases, elongation factors, Na+/K+-transporting ATPase, myosin and antibiotic-modifying enzymes. Motif 2 probably corresponds to the MgATP binding site, while motifs 3 and 1 could be involved in the splitting of the phosphodiester bond and in the phosphate transfer, respectively. Moreover, an additional motif, almost invariably centrally located, was found in all aminoglycoside-modifying enzymes. The occurrence of this motif, possibly a recombination site which would have allowed the association of units of separate functions, is compatible with a modular concept for the structure of aminoglycoside-modifying enzymes. 相似文献
4.
Genetic transformation of peppermint is known to be very difficult essentially because of low efficiency regeneration. A regeneration protocol allowing 51% shooting frequency is proposed. Transient -glucuronidase expression and adjustment of selection pressure with kanamycin are also reported. The final retained method to attempt peppermint transformation is:Agrobacterium inoculation or biolistic treatment of the first apical leaves ofin vitro clones, regeneration in the dark with kanamycin (1 mg l–1) and 6-benzylaminopurine (2 mg l–1), followed by selection of regenerated shoots with 200 mg 1–1 kanamycin.Abbreviations BA
6-benzylaminopurine
- GUS
-glucuronidase
- MS
Murashige and Skoog (1962)
- NAA
-naphthalenacetic acid
- PIG
particle inflow gun
- SEM
scanning electron microscope 相似文献
5.
Summary Somatic embryogenesis from different genotypes of Asparagus officinalis L. could be obtained by in vitro culture of shoot apices. Apices were first cultured on an auxin-rich inducing medium and then transferred onto a hormone-free development medium. All genotypes tested in this way produced a few somatic embryos. In some experiments, during the development phase, a new kind of friable highly embryogenic tissue appeared in a random manner. These tissues could be continuously subcultured on a hormone-free medium and were named embryogenic lines. Five of these embryogenic lines regenerated plants from somatic embryos. These regenerated plants exhibited an increased embryogenic response compared to the parent plants; e.g. apex culture produced somatic embryos without any auxin treatments. For one of the embryogenic lines, a genetic analysis showed that the improved embryogenic response of regenerated plants was controlled by a mendelian dominant monogenic mutation.Abbreviations LSEA
low somatic embryogenesis ability
- HSEA
high somatic embryogenesis ability
- NAA
1-naphthaleneacetic acid 相似文献
6.
Long-term gene delivery into the livers of immunocompetent mice with E1/E4-defective adenoviruses. 总被引:2,自引:1,他引:1 下载免费PDF全文
J F Dedieu E Vigne C Torrent C Jullien I Mahfouz J M Caillaud N Aubailly C Orsini J M Guillaume P Opolon P Delaere M Perricaudet P Yeh 《Journal of virology》1997,71(6):4626-4637
We have compared the in vitro and in vivo behaviors of a set of isogenic E1- and E1/E4-defective adenoviruses expressing the lacZ gene of Escherichia coli from the Rous sarcoma virus long terminal repeat. Infection of tumor-derived established cell lines of human origin with the doubly defective adenoviruses resulted in (i) a lower replication of the viral backbone that correlated with reduced levels of E2A-specific RNA and protein, (ii) a significant shutoff of late gene and protein expression, and (iii) no apparent virus-induced cytotoxicity. Independently of the extent of the deletion, the additional inactivation of E4 from the viral backbone therefore drastically disabled the virus in vitro, with no apparent effect on transgene expression. A lacZ-transgenic model was used to compare the different recombinant adenoviruses in the livers of C57BL/6 mice. The immune response to the virally encoded beta-galactosidase was minimal in this model, as infusion of the E1-defective adenovirus resulted in a time course of transgene expression that mimicked that in immunodeficient (nu/nu) mice, with very little inflammation and necrosis in the liver. Administration of a doubly defective adenovirus to the transgenic animals led to long-term extrachromosomal persistence of viral DNA in the liver, with no detectable methylation of CpG dinucleotides. However, transient transgene expression was observed independently of the extent of the E4 deletion, suggesting that the choice of the promoter may be critical to maintain transgene expression from these attenuated adenovirus vectors. 相似文献
7.
A D D'Angeac J Dornand X Emonds-Alt P Jullien J A Garcia-Sanz F Erard 《Journal of cellular physiology》1991,147(3):460-469
Transforming growth factor type beta 1 (TGB-beta 1) belongs to a family of polypeptides with regulatory effects on growth and differentiation of a variety of cell types. TGB-beta 1 plays an important role in regulation of immune response by acting as a negative control signal for T cell proliferation through still unknown mechanisms. In this study we have analysed the effects of TGB-beta 1 on EL 4-6.1, a variant of the murine EL 4 thymoma, which can be induced by phorbol 12-myristate 13-acetate (PMA) and/or interleukin 1 (IL-1) to secrete interleukin 2 (IL-2) and express IL-2 receptors (IL-2R). Using this defined model system, we show that TGB-beta 1 simultaneously down-regulates IL-2 expression and up-regulates the number of both high and low affinity IL-2R. These changes correlate with changes at the mRNA level, suggesting an effect at the pre-translational level. The specificity of both TGF-beta 1 effects was demonstrated using a neutralizing antiserum to TGF-beta 1. Our data also suggest that TGF-beta 1 does not interfere with early activation signals of PMA and/or IL-1. This model might be useful for elucidating the complex role of TGF-beta 1 in the regulation of T cell responses. 相似文献
8.
Rumi Zhang Peiyu Zhang Colin Dalton Graham A. Jullien 《Biomechanics and modeling in mechanobiology》2010,9(1):77-86
In this paper, we apply mixture theory to quantitatively predict the transient behavior of drug delivery by using a microneedle
array inserted into tissue. In the framework of mixture theory, biological tissue is treated as a multi-phase fluid saturated
porous medium, where the mathematical behavior of the tissue is characterized by the conservation equations of multi-phase
models. Drug delivery by microneedle array imposes additional requirements on the simulation procedures, including drug absorption
by the blood capillaries and tissue cells, as well as a moving interface along its flowing pathway. The contribution of this
paper is to combine mixture theory with the moving mesh methods in modeling the transient behavior of drug delivery into tissue.
Numerical simulations are provided to obtain drug concentration distributions into tissues and capillaries. 相似文献
9.
Agrobacterium-mediated transformation of Asparagus officinalis L.: molecular and genetic analysis of transgenic plants 总被引:3,自引:0,他引:3
Limanton-Grevet A. Jullien M. 《Molecular breeding : new strategies in plant improvement》2001,7(2):141-150
Four long-term embryogenic lines of Asparagus officinalis were co-cultured with the hypervirulent Agrobacterium tumefaciens strain AGL1Gin carrying a uidA gene and an nptII gene. 233 embryogenic lines showing kanamycin resistance and -glucuronidase (GUS) activity were obtained. Transformation frequencies ranged from 0.8 to 12.8 transformants per gram of inoculated somatic embryos, depending on the line. Southern analysis showed that usually 1 to 4 T-DNA copies were integrated. Regenerated plants generally exhibited the same insertion pattern as the corresponding transformed embryogenic line. T1 progeny were obtained from crosses between 6 transformed plants containing 3 or 4 T-DNA copies and untransformed plants. They were analysed for GUS activity and kanamycin resistance. In three progenies, Mendelian 1:1 segregations were observed, corresponding to one functional locus in the parent transgenic plants. Southern analysis confirmed that T-DNA copies were inserted at the same locus. Non-Mendelian segregations were observed in the other three progenies. T2 progeny also exhibited non-Mendelian segregations. Southern analysis showed that GUS-negative and kanamycin-sensitive plants did not contain any T-DNA, and therefore inactivation of transgene expression could not be responsible for the abnormal segregations. 相似文献
10.
The origin of the light scattered from macromolecular solutions is considered and a discussion is made around the use of laser and light beating spectroscopy to analyze the scattered field spectrum. Several experiments are reviewed where quasi elastic light scattering has been applied. 相似文献