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81.
W. L. Li P. D. Chen L. L. Qi D. J. Liu 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1995,90(3-4):526-533
A species-specific repeated sequence, pHvNAU62, was cloned from Haynaldia villosa, a wheat relative of great importance. It strongly hybridized to H. villosa, but not to wheat. In situ hybridization localized this sequence to six of seven H. villosa chromosome pairs in telomeric or sub-telomeric regions. Southern hybridization to whea-H. villosa addition lines showed that chromosomes 1V through 6V gave strong signals in ladders while chromosome 7V escaped detection. In addition to H. villosa, several Triticeae species were identified for a high abundance of the pHvNAU62 repeated sequence, among which Thinopyrum bassarabicum and Leymus racemosus produced the strongest signals. Sequence analysis indicated that the cloned fragment was 292 bp long, being AT rich (61%), and showed 67% homology of pSc7235, a rye repeated sequence. Isochizomer analysis suggested that the present repeated sequence was heavily methylated at the cytosine of the CpG dimer in the genome of H. villosa.It was also demonstrated that pHvNAU62 is useful in tagging the introduced 6VS chromosome arm, which confers a resistance gene to wheat powdery mildew, in the segregating generations. 相似文献
82.
W. B. Curry M. D. Grabe I. V. Kurnikov S. S. Skourtis D. N. Beratan J. J. Regan A. J. A. Aquino P. Beroza J. N. Onuchic 《Journal of bioenergetics and biomembranes》1995,27(3):285-293
The simplest views of long-range electron transfer utilize flat one-dimensional barrier tunneling models, neglecting structural details of the protein medium. The pathway model of protein electron transfer reintroduces structure by distinguishing between covalent bonds, hydrogen bonds, and van der Waals contacts. These three kinds of interactions in a tunneling pathway each have distinctive decay factors associated with them. The distribution and arrangement of these bonded and nonbonded contacts in a folded protein varies tremendously between structures, adding a richness to the tunneling problem that is absent in simpler views. We review the pathway model and the predictions that it makes for protein electron transfer rates in small proteins, docked proteins, and the photosynthetic reactions center. We also review the formulation of the protein electron transfer problem as an effective two-level system. New multi-pathway approaches and improved electronic Hamiltonians are described briefly as well. 相似文献
83.
Phosphorylation and dephosphorylation of ribosomal proteins have been suggested to participate in the regulation of protein synthesis in eukaryotic organisms. The present research focuses on the purification and partial characterization of a protein kinase from maize ribosomes that specifically phosphorylates acidic ribosomal proteins. Ribosomes purified from maize axes were used as the enzyme source. Purification of ribosomes was performed by centrifugation through a 0.5 M sucrose, 0.8 M KCl cushion. A protein kinase activity present in this fraction was released by extraction with 1.5 M KCl and further purified by diethylaminoethyl cellulose column chromatography. A peak containing protein kinase activity was eluted around 400 m M KCl. Analysis of this fraction by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed one band of 38 kDa molecular mass, which cross-reacted in a western blot with antibodies raised against proteins from the large ribosomal subunit. This enzyme specifically phosphorylates one of the acidic ribosomal proteins (P2 ). Its activity is inhibited by Ca2+ and Zn2+ and is activated by Mg2+ , polylysine and spermine. The relevance of this protein kinase in reinitiating the protein synthesis process during germination is discussed. 相似文献
84.
Júlia Tandori László Nagy Ágnes Puskás Magdolna Droppa Gábor Horváth Péter Maróti 《Photosynthesis research》1995,45(2):135-146
A spontaneous mutant (R/89) of photosynthetic purple bacterium Rhodobacter sphaeroides R-26 was selected for resistance to 200 M atrazin. It showed increased resistance to interquinone electron transfer inhibitors of o-phenanthroline (resistance factor, RF=20) in UQo reconstituted isolated reaction centers and terbutryne in reaction centers (RF=55) and in chromatophores (RF=85). The amino acid sequence of the QB binding protein of the photosynthetic reaction center (the L subunit) was determined by sequencing the corresponding pufL gene and a single mutation was found (IleL229 Met). The changed amino acid of the mutant strain is in van der Waals contact with the secondary quinone QB. The binding and redox properties of QB in the mutant were characterized by kinetic (charge recombination) and multiple turnover (cytochrome oxidation and semiquinone oscillation) assays of the reaction center. The free energy for stabilization of QAQB
– with respect to QA
–QB was GAB=–60 meV and 0 meV in reaction centers and GAB=–85 meV and –46 meV in chromatophores of R-26 and R/89 strains at pH 8, respectively. The dissociation constants of the quinone UQo and semiquinone UQo
– in reaction centers from R-26 and R/89 showed significant and different pH dependence. The observed changes in binding and redox properties of quinones are interpreted in terms of differential effects (electrostatics and mesomerism) of mutation on the oxidized and reduced states of QB.Abbreviations BChl
bacteriochlorophyll
- Ile
isoleucine
- Met
methionin
- P
primary donor
- QA
primary quinone acceptor
- QB
secondary quinone acceptor
- RC
reaction center protein
- UQo
2,3-dimethoxy-5-methyl benzoquinone
- UQ10
ubiquinone 50
This work is dedicated to the memory of Randall Ross Stein (1954–1994) and is, in a small way, a testament to the impact which Randy's ideas have had on the development of the field of competitive herbicide binding. 相似文献
85.
86.
The ability of aras protein to associate with proteins present in rat brain cytosolin vitro was investigated using chemical cross-linking agents and the125I-labelled v-H-ras protein. Two iodinated protein complexes with apparent molecular weights of 40 and 85 kDa were observed when a mixture of rat brain cytosol and [125I]ras was treated with the cross-linking agent disuccinimidyl suberate and subjected to SDS-PAGE. Formation of the [125I] 85 kDa complex was enhanced by a high concentration of EDTA while generation of the 40 kDa species was abolished by this treatment. Formation of the [125I] 85 kDa complex was inhibited by unlabelledras protein, GTP, GTPS, and GDP but not by ATPS and GMP.Chromatography of the cross-linked brain cytosol-[125I]ras mixture on DEAE cellulose partially resolved the [125I] 85 kDa complex from the [125I]ras protein. The [125I] 85 kDa complex (formed using ethyleneglycolbis (succinimidylsuccinate) as the cross-linking agent) could be immunoprecipitated using a rabbit anti-ras polyclonal antibody. Treatment of the immunoprecipitate with hydroxylamine to cleave the cross-link yielded [125I]-labelledras. A substantial enrichment of the proportion of the [125I] 85 kDa complex in the cross-linked extract was achieved by preparative SDS-PAGE. It is concluded that thein vitro chemical cross-linking approach employed here has detected tworas binding proteins in rat brain cytosol: a 65 kDa heat-sensitive and a 20 kDa heat-stable protein. The possibility that the 65 kDaras binding protein is aras regulatory orras effector protein which has not so far been characterised is briefly discussed.Abbreviations DSS
disuccinimidyl suberate
- EGS
ethyleneglycolbis (succinimidylsuccinate)
- GTPS
guanosine 5-[-thio] triphosphate
- ATPS
adenosine 5-[-thio] triphosphate 相似文献
87.
Summary Versatile three-step procedures for syntheses of seven racemi-fluoro-a-amino acids are described. Alkylation oftert-butyl N-(diphenylmethylene) glycinate with 1-bromo-2-fluoroalkanes gave N-protected aminoacid esters both in anhydrous medium using lithium-diisopropylamide as base at low temperature or in a two phase system of 50% aqueous sodium hydroxide and methylene chloride with triethylbenzylammonium chloride as the phase transfer catalyst at room temperature. Subsequent two-step deprotection with citric acid and hydrochloric acid gave the title compounds in 13–33% overall yields.Dedicated to Professor Dr.mult., Dr.h.c. Alois Haas on the occasion of his 65th birthday 相似文献
88.
In this study thiol-monolayers were used in order to modify gold and provide suitable chemical functionalities for the immobilization of the small redox-active haem-containing peptide, microperoxidase (MP-11). Initially, we assembled a variety of thiol-containing species on the gold electrodes and measured a series of electron transfer reactions, each characteristic of the surface-modifier. Using suitable immobilization strategies, we subsequently covalently bound MP-11 to appropriate monolayers and found two characteristic electrochemical responses (i.e. using MP-11 bound to mercaptopropionic acid, redox peaks were seen at E0′ = −315 mV and at +179 mV versus Ag|AgCl, with the former being attributed to the haem and the latter with the thiol monolayer). Exposure of the peptide-thiol surface to UV irradiation resulted in cleavage of the Au---S bond, leading to a decrease in the magnitude of both responses. Our work is supported by corroborative evidence showing the immobilization of the peptide, obtained using both X-ray photoelectron and reflectance Fourier transform infra-red spectroscopies. We hypothesize that differences in the ionic charges on the protein backbone account for the shift in E0′ for MP-11, as observed in our system, when compared to that found for MP-11 immobilized by different strategies. 相似文献
89.
Mitochondria transfer into mouse ova by microinjection 总被引:10,自引:0,他引:10
A method for mitochondria isolation and interspecific transfer of mitochondria was developed in mice. Mitochondria were isolated from Mus spretus liver samples for microinjection into fertilized ova obtained from superovulated M. musculus domesticus females. Electron microscopic observations of mitochondria preparations used for microinjection demonstrated intact mitochondrial vesicles with little microsomal contamination. Species-specific nested PCR primers complementary to sequence differences in the mitochondrial DNA D-loop region revealed high rates of successful transfer of foreign mitochondria after isolation and injection into zygotes cultured through the blastocyst stage of embryonic development. Of 217 zygotes, 67 survived mitochondria injection and 23 out of 37 zygotes developed were at the blastocyst-stage of embryonic development after 4.5 days of in vitro culture. All 23 of these blastocysts contained detectable levels of foreign mitochondria. These results represent an initial step in developing a model system to study mitochondrial dynamics and development of therapeutic strategies for human metabolic diseases affected by aberrations in mitochondrial function or mutation 相似文献
90.
Abstract: The α subunit of Gz (αz) harbors two N-terminal serine residues (at positions 16 and 27) that serve as protein kinase C-mediated phosphorylation sites. The cognate residues in the α subunit of Gt1 provide binding surfaces for the β1 subunit. We used three serine-to-alanine mutants of αz to investigate the functional importance of the two N-terminal serine residues. Wild-type or mutant αz was transiently coexpressed with different receptors and adenylyl cyclase isozymes in human embryonic kidney 293 cells, and agonist-dependent regulation of cyclic AMP accumulation was examined in a setting where all endogenous α subunits of Gi were inactivated by pertussis toxin. Replacement of one or both serine residues by alanine did not alter the ability of αz to interact with δ-opioid, dopamine D2, or adenosine A1 receptors. Its capacity to inhibit endogenous and type VI adenylyl cyclases was also unaffected. Functional release of βγ subunits from the mutant αz subunits was not impaired because they transduced βγ-mediated stimulation of type II adenylyl cyclase. Constitutively active mutants of all four αz subunits were constructed by the introduction of a Q205L mutation. The activated mutants showed differential abilities to inhibit human choriogonadotropin-mediated cyclic AMP accumulation in luteinizing hormone receptor-transfected cells. Loss of both serine residues, but not either one alone, impaired the receptor-independent inhibition of adenylyl cyclase by the GTPase-deficient mutant. Thus, replacement of the amino-terminal serine residues of αz has no apparent effect on receptor-mediated responses, but these serine residues may be essential for ensuring transition of αz into the active conformation. 相似文献