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991.
Microtubule stability in budding yeast: characterization and dosage suppression of a benomyl-dependent tubulin mutant. 总被引:6,自引:1,他引:5
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To better understand the dynamic regulation of microtubule structures in yeast, we studied a conditional-lethal beta-tubulin mutation tub2-150. This mutation is unique among the hundreds of tubulin mutations isolated in Saccharomyces cerevisiae in that it appears to cause an increase in the stability of microtubules. We report here that this allele is a mutation of threonine 238 to alanine, and that tub2-150 prevents the spindle from elongating during anaphase, suggesting a nuclear microtubule defect. To identify regulators of microtubule stability and/or anaphase, yeast genes were selected that, when overexpressed, could suppress the tub2-150 temperature-sensitive phenotype. One of these genes, JSN1, encodes a protein of 125 kDa that has limited similarity to a number of proteins of unknown function. Overexpression of the JSN1 gene in a TUB2 strain causes that strain to become more sensitive to benomyl, a microtubule-destabilizing drug. Of a representative group of microtubule mutants, only one other mutation, tub2-404, could be suppressed by JSN1 overexpression, showing that JSN1 is an allele-specific suppressor. As tub2-404 mutants are also defective for spindle elongation, this provides additional support for a role for JSN1 during anaphase. 相似文献
992.
993.
S. T. Berry R. J. Allen S. R. Barnes P. D. S. Caligari 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1994,89(4):435-441
cDNA and PstI genomic clones have been used to assess levels of restriction fragment length polymorphism (RFLP) in Helianthus annuus and to determine the inter-relationships between a diverse set of 24 inbred lines. Of the cDNA clones screened 45% were useful as RFLP probes, compared to less than 20% from the PstI library, which showed high levels of redundancy for high copy sequences. Fifty-seven low-copy DNA probes (23 PstI and 34 cDNA clones) were used to fingerprint 12 maintainer (B) lines and 12 restorer (R) lines. The average number of RFLP variants per probe was found to be 3.2, with a mean polymorphic index of 0.49, indicating that high levels of nuclear DNA polymorphism are to be found in cultivated sunflower. Cluster and principal coordinate analysis of the fingerprinting data clearly separated the maintainer and restorer lines, but there was a degree of association between 2 unbranched R-lines and the B-line germ plasm pool. 相似文献
994.
M. A. Fitzgerald S. H. Barnes S. Blackmore D. M. Calder R. B. Knox 《Protoplasma》1994,179(3-4):121-130
Summary The position of the callose wall is related to the position of the primexine matrix that forms around the peripheral tetrads
during microspore development of the compound unit, the pollinium. We report a combined freeze-fracture and freeze-substitution
study of the events associated with early exine development. Stage one of exine development is deposition of protosporopollenin
that is probably synthesised by the microspore and secreted to the primexine matrix where it is polymerised. Enzymes for the
polymerisation of the protosporopollenin may be synthesised by the microspores and then transported, via the endoplasmic reticulum,
to the plasma membrane. Stage two of exine development follows callose dissolution and deposition of tapetally derived sporopollenin.
Hence exine form and exine deposition inDendrobium appear to be the result of intimate cooperation between the microspore, the plasma membrane, the callose and the tapetum. 相似文献
995.
The crude product of deamination of the commercially available
-homoserine was acetylated and the 2-O-acetyl-3-deoxy-
-glycero-tetronolactone (18) formed was used to N-acylate methyl perosaminide (methyl 4-amino-4,6-dideoxy-α-
-mannopyranoside, 12) and its 2,3-O-isopropylidene derivative. The major product isolated from the reaction was the crystalline methyl 4-(4-O-acetyl-3-deoxy-
-glycero-tetronamido)-4,6-dideoxy-α-
-mannopyranoside (1, 70–75%) resulting from acetyl group migration in the initially formed 2'-O-acetyl derivative. O-Deacetylation of 1 gave the title amide 2. Compound 2, obtained crystalline for the first time, was fully characterized, and its crystal structure was determined. Deoxytetronamido derivatives diastereomeric with 1 and 2, respectively, were obtained by the acylation of 12 with 2-O-acetyl-3-deoxy-
-glycero-tetronolactone (prepared from
-homoserine), and subsequent deacetylation. Structures of several byproducts of the reaction of 12 with 18 have been deduced from their spectral characteristics. Since these byproducts were various O-acetyl derivatives of 2, the title compound could be obtained in ≈ 90% yield by deacetylating (Zemplén) the crude mixture of N-acylation products, followed by chromatography. 相似文献
996.
Alteration in the Amino Acid Content of Yeast During Growth Under Various Nutritional Conditions 总被引:4,自引:3,他引:1
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Albert G. Moat Fazal Ahmad James K. Alexander Isabel J. Barnes 《Journal of bacteriology》1969,98(2):573-578
Yeast cells grown under optimal and suboptimal concentrations of biotin were analyzed for the amino acid content of their soluble pool and cellular protein. Optimally grown yeast cells exhibited a maximum amino acid content after 18 hr of growth. Biotin-deficient cells were depleted of all amino acids at 26 and 43 hr, with alanine, arginine, aspartate, cysteine, glutamate, isoleucine, leucine, lysine, methionine, serine, threonine, and valine being present in less than half the concentration observed in biotin-optimal cells. At early time intervals, the amino acid pool of biotin-deficient yeast contained lower concentrations of all amino acids except alanine. After more prolonged incubation, several amino acids accumulated in the pool of biotin-deficient yeast, but citrulline and ornithine accumulated to appreciable levels. The addition of aspartate to the growth medium resulted in a decrease in the amino acid content of biotin-optimal cells but caused a marked increase in the concentration of amino acids in biotin-deficient cells. The pools of biotin-deficient yeast grown in the presence of aspartate displayed a marked reduction in every amino acid with the exception of aspartate itself. These data provide evidence that the amino acid content of yeast cells and their free amino acid pools are markedly affected by biotin deficiency as well as by supplementation with aspartate, indicating that aspartate plays a major role in the nitrogen economy of yeast under both normal as well as abnormal nutritional conditions. 相似文献
997.
Biochemical characterization of lysine auxotrophs of Staphylococcus aureus 总被引:1,自引:1,他引:0
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Lysine biosynthesis in Staphylococcus aureus has been studied by use of a series of lysine auxotrophs. The strains were isolated after chemical mutagenesis. The majority of these mutant strains were classified according to the enzymatic step found to be deficient. Specific enzyme assays as well as nutritional tests were used to group the organisms. The enzymes included were dihydrodipicolinate synthetase, dihydrodipicolinate reductase, diaminopimelate epimerase, and diaminopimelate decarboxylase. The accumulation of diaminopimelate in certain mutants and the demonstration of dihydrodipicolinate synthetase and reductase provide the first detailed evidence that S. aureus utilizes the diaminopimelate pathway for lysine biosynthesis. A cell-free system was used to study the regulation of these enzymes with the exception of diaminopimelate epimerase. Lysine repressed all of the enzymes tested. The repression appeared to be coordinate in nature. The data presented provide suggestive evidence that the lysine biosynthetic region in S. aureus constitutes an operon. 相似文献
998.
Automated Instrument for the Fluorescent Treponemal Antibody-Absorption Test and Other Immunofluorescence Tests 总被引:6,自引:4,他引:2
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Gerald F. Binnings Mel J. Riley Merritt E. Roberts Richard Barnes Thomas C. Pringle 《Applied microbiology》1969,18(5):861-868
An automated diagnostic test instrument and its development program are described. The instrument automates the fluorescent treponemal antibody-absorption test for syphilis to the extent that only 4 hr of technician time is required to conduct approximately 200 tests daily. Evaluation to date suggests its efficacy. In addition, preliminary studies indicate the feasibility of detecting antibodies to Toxoplasma gondii, Plasmodium malariae, and nucleoprotein (antinuclear factor). The instrument would seem to have broad application for routine and research immunofluorescence testing. Two elements comprise the instrument: a slide processor and a microscope attachment. The slide processor is an electro-pneumatically actuated device which automatically feeds special laboratory slides, on which antigen or other reagents are prefixed, through a series of operations which provide reagent application, incubation, washing, drying, and stacking of the finished slides for readout. The instrument provides flexibility in that incubation time and temperature as well as point, sequence, and duration of reagent application can be varied to accommodate a variety of immunofluorescence techniques. The microscope attachment can be fitted to all conventional dark-field fluorescence microscopes and makes possible the reading of three to six slides per minute. The reacted slides from the processor are injected sequentially onto the stage of the microscope by movement of a lever. As injected, slides are automatically in visual focus; fine focus is occasionally required. Scanning of the reacted field is accomplished by means of the normal microscope controls. A buffered glycerol coupling is maintained between the darkfield condenser substage lens and the slide cover glass by means of a pushbutton-actuated feed system. 相似文献
999.
1000.
Harold Barnes 《Helgoland Marine Research》1967,15(1-4):6-26
Summary 1. The definition of the word ecology is considered and the difficulties — both practical and theoretical — associated with a precise formulation outlined.2. Ecology as the study of systems consisting of components, or variables, each made up of a number of vectors is discussed.3. A comparison of the difficulties inherent in the definition with those — less apparent — in abiotic systems is made.4. The meaning of the word experimental is considered and its relation to a series of transformations on a biological system discussed.5. The meaning — in the restricted sense determined by the definitions given — of experimental ecology and the practical problems it poses are dealt with in some detail.6. The meaning of experimental biology and its relation to experimental ecology, as defined above, is discussed in relation to plant and animal systems.7. The future of ecology — experimental and otherwise is discussed.8. The increase in information will call for a greater integrative approach and the possible ways by which this can be achieved are outlined, particularly as they relate to the marine biological sciences.
Ökologie und experimentelle Biologie
Kurzfassung Der Begriff Ökologie wird erörtert und die praktischen sowie theoretischen Schwierigkeiten aufgezeigt, welche einer präzisen Definition im Wege stehen. Ökologie wird als ein Forschungsgebiet aufgefaßt, das sich mit dem Studium von Systemen beschäftigt, welche aus Komponenten oder Variablen bestehen, von denen jede wieder eine Anzahl von Vektoren enthält und Vergleiche mit abiotischen Systemen anstellt. Die Bedeutung des Wortes experimentell wird erörtert und dessen Beziehung zu einer Serie von Transformationen an einem biologischen System diskutiert. Eingehende Überlegungen werden dem auf Grund der gegebenen Definitionen eingeschränkten Begriffsinhalt experimentelle Ökologie und den praktischen Problemen gewidmet, welche dieses Forschungsgebiet uns aufgibt. Die Konotation des Terminus experimentelle Biologie wird behandelt und die Beziehung zwischen experimenteller Biologie und experimenteller Ökologie im Hinblick auf Pflanzen- und Tiersysteme diskutiert. Die Zukunft der Ökologie — experimentell und nichtexperimentell — bedarf besonderer Aufmerksamkeit. Das ständige Anwachsen der pro Zeiteinheit produzierten neuen Informationen macht eine stärkere Integration erforderlich; Vorschläge, wie dies erreicht werden könnte, werden vorgelegt, und zwar unter besonderer Berücksichtigung meeresbiologischer Aspekte.相似文献