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101.
Membrane potentials, cable parameters, and component resting conductances were measured in extensor digitorum longus (EDL) muscle fibers from adult rats in vitro at 24 degrees C, after 15 to 18 days of denervation by nerve section, and at seven to ten days following epineural injection of 100 to 450 mug of colchicine in the peroneal nerve. The denervated muscles were paralyzed throughout the experimental period, whereas the colchicine-treated preparations showed no clinical paralysis except for the first day or two. The EDL from the untreated side served as a control. Both the denervated and colchicine-treated fibers were depolarized, showed signs of fibrillation, had tetrodotoxin-resistant potentials, and membrane resistance was increased two- to sevenfold. In the denervated fibers, mean chloride conductance GC1 dropped from a control value of 3196 to 596 mumhos/cm2 while mean potassium conductance GK showed a tendency to rise from 260 to 332 muhos/cm2. Colchicine-treated fibers while showing a similar fall in mean GC1 from 2993 to 1066 mumhos/cm2, also showed a significant fall in mean GK from 213 to 116 mumhos/cm2. It was concluded that factors transported by the microtubular system are important for the maintenance of the high resting GC1 of mammalian skeletal muscle fibers. 相似文献
102.
Donald A. Bryant Alexander N. Glazer Frederick A. Eiserling 《Archives of microbiology》1976,110(1):61-75
Studies are presented of the biliproteins of Anabaena sp. This filamentous cyanobacterium contains three major biliproteins. Whereas two of these, C-phycocyanin and allophycocyanin, are common to all cyanobacteria, the third, phycoerythrocyanin (max568nm) has hitherto not been described and its distribution among cyanobacteria appears to be limited.
Anabaena variabilis and Anabaena sp. 6411 allophycocyanin, C-phycocyanin, and phycoerythrocyanin were purified to homogeneity and characterized with respect to molecular weight, isoelectric point, absorption spectrum and amino acid composition. The and subunits of each of these proteins were also purified to homogeneity and characterized in the same manner. The tetrapyrrole chromophore content was determined for each of the proteins and subunits. The subunit of phycoerythrocyanin carries a novel phycobiliviolin-like chromophore. This chromophore has not previously been detected in cyanobacterial biliproteins, but has been noted as a prosthetic group of a cryptophytan phycocyanin.Sedimentation equilibrium studies show that at pH 7.0, at protein concentrations of 0.2–0.6 mg/ml, allophycocyanin, C-phycocyanin and phycoerythrocyanin, each exists as a trimeric aggregate, ()3, of molecular weight of approximately 105000. Structural studies of microcrystals of these three biliproteins by electron microscopy and X-ray diffraction reveal a common plan for the construction of higher assembly forms. The major building block appears to be the trimer ()3. It is proposed that this is a dise-like structure about 3.0×12.0 nm. The individual or subunits are roughly spherical, 3 nm in diameter. Allophycocyanin trimers stack to form bundles of rods which form long needles. Both phycocyanin and phycoerythrocyanin form double dises ()6 which are visible as ring-shaped structures by electron microscopy. The mode of assembly of the biliproteinstructures in the phycobilisome is, as yet, unknown.Abbreviation Used SDS
sodium dodecyl sulfate
Dedicated to Prof. Dr. Roger Y. Stanier on the occasion of his 60th birthday. 相似文献
103.
A polyurethane-foam enlarged reconstruction was made from serial sections of a portion of young adult human lung parenchyman. Study of the progeny of a terminal bronchiole disclosed three generations of respiratory bronchioles and an irregular branching pattern of eight generations of alveolar ducts. Sacs and alveoli arose from the lateral and distal aspects of all generations of ducts. There were an average of 3.5 alveoli per sac. Considering the terminal bronchiole as the first generation branch of the acinus, over 60 per cent of the alveoli counted and predicted were members of the 10-12th generations. The acinus contained one terminal bronchiole and approximately 14 respiratory bronchioles, 1,200-1,500 ducts, 2,500-4,500 sacs, and 14,000-20,000 alveoli. 相似文献
104.
Studies of regulatory metabolism in Moniezia expansa: the role of phosphoenolpyruvate carboxykinase.
Phosphoenolpyruvate carboxykinase (PEPCK) from M. expansa has been partially purified and its behaviour in a range of different assay conditions has been determined. Different PEPCK's were found in the cytosol and mitochondria. Some kinetic parameters for each are presented. Both enzymes are activated by Mn2+; cytosolic PEPCK is also activated by Mg2+. The enzymes have pH optima in the range 6·4–7·0. They do not differ with respect to their apparent affinities for inosine and guanosine diphosphates, but the latter allows higher maximal activity. Little activity is observed with adenosine diphosphate. Adenosine and inosine triphosphates exert weak inhibitory effects on the Mn2+ activated enzymes; a much strongsr inhibition is exerted on the cytosolic enzyme when activated by Mg2+. A number of non-nucleotide compounds were tested for possible inhibitory effects with no success. The forward and back reactions catalyzed by PEPCK proceed at similar rates, suggesting that the enzyme may be readily raversible in vivo. 相似文献
105.
106.
H Hoehn E M Bryant K Au T H Norwood H Boman G M Martin 《Cytogenetics and cell genetics》1975,15(5):282-298
The term "variegated translocation mosaicism" is used to describe the repeated occurrence, within cultures of human skin fibroblasts, of a multiplicity of chromosomal rearrangements. With respect to the frequencies of such cytogenetically aberrant clones we found that they (1) were not detectable in routine diagnostic skin fibroblast cultures from 29 subjects with a wide variety of indications for biopsy; (2) were not detectable during in vitro aging of diploid strains with four normal individuals; (3) could be detected after rescue from bacterial contamination of a culture from an otherwise normal diploid male; (4) occurred with high frequencies in independent cultures from another apparently normal subject; (5) occurred with high frequencies in multiple biopsies obtained at autopsy from a patient with Werner's syndrome who died of sepsis; (6) were of pseudodiploid nature; and (7) involved a different spectrum of chromosomes in different individuals. A consistent association with mycoplasma contamination could not be made. 相似文献
107.
108.
Anser C. Azim Joan H. M. Knoll Shirin M. Marfatia David J. Peel Peter J. Bryant Athar H. Chishti 《Genomics》1995,30(3)
The Drosophila discs large tumor suppressor protein, Dlg, is the prototype of a newly discovered family of proteins termed MAGUKs (membrane-associated guanylate kinase homologues). MAGUKs are localized at the membrane-cytoskeleton interface, usually at cell-cell junctions, where they appear to have both structural and signaling roles. They contain several distinct domains, including a modified guanylate kinase domain, an SH3 motif, and one or three copies of the DHR (GLGF/PDZ) domain. Recessive lethal mutations in the discs large tumor suppressor gene interfere with the formation of septate junctions (thought to be the arthropod equivalent of tight junctions) between epithelial cells, and they cause neoplastic overgrowth of imaginal discs, suggesting a role for cell junctions in proliferation control. A homologue of the Dlg protein, named Hdlg, has been isolated from human B lymphocytes. It shows 65-79% identity to Dlg in the different domains, and it binds to the cytoskeletal protein 4.1. Here, we report that the gene for lymphocyte Hdlg, named DLG1, is located at chromosome band 3q29. This finding identifies a novel site for a candidate tumor suppressor on chromosome 3. 相似文献
109.
Michael Abberton Jacqueline Batley Alison Bentley John Bryant Hongwei Cai James Cockram Antonio Costa de Oliveira Leland J. Cseke Hannes Dempewolf Ciro De Pace David Edwards Paul Gepts Andy Greenland Anthony E. Hall Robert Henry Kiyosumi Hori Glenn Thomas Howe Stephen Hughes Mike Humphreys David Lightfoot Athole Marshall Sean Mayes Henry T. Nguyen Francis C. Ogbonnaya Rodomiro Ortiz Andrew H. Paterson Roberto Tuberosa Babu Valliyodan Rajeev K. Varshney Masahiro Yano 《Plant biotechnology journal》2016,14(4):1095-1098
Agriculture is now facing the ‘perfect storm’ of climate change, increasing costs of fertilizer and rising food demands from a larger and wealthier human population. These factors point to a global food deficit unless the efficiency and resilience of crop production is increased. The intensification of agriculture has focused on improving production under optimized conditions, with significant agronomic inputs. Furthermore, the intensive cultivation of a limited number of crops has drastically narrowed the number of plant species humans rely on. A new agricultural paradigm is required, reducing dependence on high inputs and increasing crop diversity, yield stability and environmental resilience. Genomics offers unprecedented opportunities to increase crop yield, quality and stability of production through advanced breeding strategies, enhancing the resilience of major crops to climate variability, and increasing the productivity and range of minor crops to diversify the food supply. Here we review the state of the art of genomic‐assisted breeding for the most important staples that feed the world, and how to use and adapt such genomic tools to accelerate development of both major and minor crops with desired traits that enhance adaptation to, or mitigate the effects of climate change. 相似文献
110.
Loren P. Albert Natalia Restrepo‐Coupe Marielle N. Smith Jin Wu Cecilia Chavana‐Bryant Neill Prohaska Tyeen C. Taylor Giordane A. Martins Philippe Ciais Jiafu Mao M. Altaf Arain Wei Li Xiaoying Shi Daniel M. Ricciuto Travis E. Huxman Sean M. McMahon Scott R. Saleska 《Global Change Biology》2019,25(11):3591-3608
Plant phenology—the timing of cyclic or recurrent biological events in plants—offers insight into the ecology, evolution, and seasonality of plant‐mediated ecosystem processes. Traditionally studied phenologies are readily apparent, such as flowering events, germination timing, and season‐initiating budbreak. However, a broad range of phenologies that are fundamental to the ecology and evolution of plants, and to global biogeochemical cycles and climate change predictions, have been neglected because they are “cryptic”—that is, hidden from view (e.g., root production) or difficult to distinguish and interpret based on common measurements at typical scales of examination (e.g., leaf turnover in evergreen forests). We illustrate how capturing cryptic phenology can advance scientific understanding with two case studies: wood phenology in a deciduous forest of the northeastern USA and leaf phenology in tropical evergreen forests of Amazonia. Drawing on these case studies and other literature, we argue that conceptualizing and characterizing cryptic plant phenology is needed for understanding and accurate prediction at many scales from organisms to ecosystems. We recommend avenues of empirical and modeling research to accelerate discovery of cryptic phenological patterns, to understand their causes and consequences, and to represent these processes in terrestrial biosphere models. 相似文献