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41.
42.
Patricia L. Kilian Carolyn R. Dunlap Paul Mueller Mark A. Schell Richard L. Huganir Efraim Racker 《Biochemical and biophysical research communications》1980,93(2):409-414
Acetylcholine receptor from can be incorporated by the cholate dialysis procedure into liposomes prepared with crude soybean phospholipids (asolectin). Vesicles reconstituted with asolectin depleted of neutral lipids or with a mixture of pure phospholipids, are less active in catalyzing carbamylcholine-sensitive Na+ flux. Inclusion of α-tocopherol or certain quinones such as coenzyme Q10 or vitamin K1 during reconstitution yields vesicles with carbamylcholine-sensitive Na+ flux which, under optimal conditions, was considerably higher than that observed with vesicles reconstituted with crude phospholipid mixtures. 相似文献
43.
Structure of internalin,a major invasion protein of Listeria monocytogenes,in complex with its human receptor E-cadherin 总被引:13,自引:0,他引:13
Schubert WD Urbanke C Ziehm T Beier V Machner MP Domann E Wehland J Chakraborty T Heinz DW 《Cell》2002,111(6):825-836
Listeria monocytogenes, a food-borne bacterial pathogen, enters mammalian cells by inducing its own phagocytosis. The listerial protein internalin (InlA) mediates bacterial adhesion and invasion of epithelial cells in the human intestine through specific interaction with its host cell receptor E-cadherin. We present the crystal structures of the functional domain of InlA alone and in a complex with the extracellular, N-terminal domain of human E-cadherin (hEC1). The leucine rich repeat (LRR) domain of InlA surrounds and specifically recognizes hEC1. Individual interactions were probed by mutagenesis and analytical ultracentrifugation. These include Pro16 of hEC1, a major determinant for human susceptibility to L. monocytogenes infection that is essential for intermolecular recognition. Our studies reveal the structural basis for host tro-pism of this bacterium and the molecular deception L. monocytogenes employs to exploit the E-cadherin system. 相似文献
44.
Impact of a Genetically Engineered Bacterium with Enhanced Alkaline Phosphatase Activity on Marine Phytoplankton Communities 下载免费PDF全文
An indigenous marine Achromobacter sp. was isolated from coastal Georgia seawater and modified in the laboratory by introduction of a plasmid with a phoA hybrid gene that directed constitutive overproduction of alkaline phosphatase. The effects of this "indigenous" genetically engineered microorganism (GEM) on phosphorus cycling were determined in seawater microcosms following the addition of a model dissolved organic phosphorus compound, glycerol 3-phosphate, at a concentration of 1 or 10 (mu)M. Within 48 h, a 2- to 10-fold increase in the concentration of inorganic phosphate occurred in microcosms containing the GEM (added at an initial density equivalent to 8% of the total bacterial population) relative to controls containing only natural microbial populations, natural populations with the unmodified Achromobacter sp., or natural populations with the Achromobacter sp. containing the plasmid but not the phoA gene. Secondary effects of the GEM on the phytoplankton community were observed after several days, evident as sustained increases in phytoplankton biomass (up to 14-fold) over that in controls. Even in the absence of added glycerol 3-phosphate, a numerically stable GEM population (averaging 3 to 5% of culturable bacteria) was established within 2 to 3 weeks of introduction into seawater. Moreover, alkaline phosphatase activity in microcosms with the GEM was substantially higher than that in controls for up to 25 days, and microcosms containing the GEM maintained the potential for net phosphate accumulation above control levels for longer than 1 month. 相似文献
45.
M. B. Slabaugh G. M. Huestis J. Leonard J. L. Holloway C. Rosato V. Hongtrakul N. Martini R. Toepfer M. Voetz J. Schell S. J. Knapp 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1997,94(3-4):400-408
Gene sequences are rapidly accumulating for many commercially and scientifically important plants. These resources create
the basis for developing sequence-based markers for mapping and tracking known (candidate) genes, thereby increasing the utility
of genetic maps. Members of most of the gene families underlying the synthesis of seed oil fatty acids have been cloned from
the medium-chain oilseed Cuphea. Allele-specific-PCR (AS-PCR) and single-strand conformational polymorphism (SSCP) markers were developed for 22 fatty acid
synthesis genes belonging to seven gene families of Cuphea using homologous and heterologous DNA sequences. Markers were developed for 4 fatty-acyl-acyl carrier protein thioesterase,
2 β-ketoacyl-acyl carrier protein synthase I, 4 β-ketoacyl-acyl carrier protein synthase II, 3 β-ketoacyl-acyl carrier protein
synthase III, 3 acyl carrier protein, 2 β-ketoacyl-acyl carrier protein reductase, and 4 enoyl-acyl carrier protein reductase
loci. Eighty-eight percent (14 of 16) of the SSCP loci were polymorphic, whereas only 9% (2 of 22) of the AS-PCR loci were
polymorphic. These markers were mapped using a Cuphea viscosissima×C. lanceolata F2 population and produced linkage groups of 10, 3, and 2 loci (3 loci segregated independently). The 10-locus linkage group
had every gene but one necessary for the synthesis of 2- to 16-carbon fatty acids from acetyl-CoA and malonyl-ACP (the missing
gene family was not mapped). SSCP analysis has broad utility for DNA fingerprinting and mapping genes and gene families.
Received: 3 May 1996 / Accepted: 30 August 1996 相似文献
46.
Cytotoxic T-Lymphocyte Epitope Immunodominance in the Control of Choroid Plexus Tumors in Simian Virus 40 Large T Antigen Transgenic Mice 下载免费PDF全文
Todd D. Schell Lawrence M. Mylin Ingo Georgoff Angelica K. Teresky Arnold J. Levine Satvir S. Tevethia 《Journal of virology》1999,73(7):5981-5993
The simian virus 40 (SV40) large tumor antigen (Tag) is a virus-encoded oncoprotein which is the target of a strong cytotoxic T-lymphocyte (CTL) response. Three immunodominant H-2(b)-restricted epitopes, designated epitopes I, II/III, and IV, have been defined. We investigated whether induction of CTLs directed against these Tag epitopes might control Tag-induced tumors in SV11(+) (H-2(b)) mice. SV11(+) mice develop spontaneous tumors of the choroid plexus due to expression of SV40 Tag as a transgene. We demonstrate that SV11(+) mice are functionally tolerant to the immunodominant Tag CTL epitopes. CTLs specific for the H-2Kb-restricted Tag epitope IV were induced in SV11(+) mice following adoptive transfer with unprimed C57BL/6 spleen cells and immunization with recombinant vaccinia viruses expressing either full-length Tag or the H-2Kb-restricted epitope IV as a minigene. In addition, irradiation of SV11(+) mice prior to adoptive transfer with unprimed C57BL/6 spleen cells led to the priming of epitope IV-specific CTLs by the endogenous Tag. Induction of epitope IV-specific CTLs in SV11(+) mice by either approach correlated with increased life span and control of the choroid plexus tumor progression, indicating that CTLs specific for the immunodominant Tag epitope IV control the progressive growth of spontaneous tumors induced by this DNA virus oncogene in transgenic mice. 相似文献
47.
48.
49.
Annual and seasonal changes in diets of martens: evidence from stable isotope analysis 总被引:18,自引:0,他引:18
Theory predicts that generalist predators will switch to alternative prey when preferred foods are not readily available.
Studies on the feeding ecology of the American marten (Martes americana) throughout North America suggest that this mustelid is a generalist predator feeding largely on voles (Microtus sp.; Clethrionomys sp.). We investigated seasonal and annual changes in diets of martens in response to the changing abundance of small rodents
(Peromyscus keeni, and Microtus longicaudus) on Chichagof Island, Southeast Alaska, using stable isotope analysis. We hypothesized that martens would feed primarily
on small rodents during years with high abundance of these prey species, whereas during years of low abundance of prey, martens
would switch to feed primarily on the seasonally available carcasses of salmon. We also hypothesized that home-range location
on the landscape (i.e., access to salmon streams) would determine the type of food consumed by martens, and martens feeding
on preferred prey would exhibit better body condition than those feeding on other foods. We live-captured 75 martens repeatedly,
from mid-February to mid-December 1992–1994. We also obtained marten carcasses from trappers during late autumn 1991 and 1992,
from which we randomly sub-sampled 165 individuals. Using stable isotope ratios and a multiple-source mixing model, we inferred
that salmon carcasses composed a large portion of the diet of martens in autumn during years of low abundance of rodents (1991
and 1992). When small rodents were available in high numbers (1993 and 1994), they composed the bulk of the diet of martens
in autumn, despite salmon carcasses being equally available in all years. Selection for small rodents occurred only in seasons
in which abundance of small rodents was low. Logistic regression revealed that individuals with access to salmon streams were
more likely to incorporate salmon carcasses in their diet during years of low abundance of small rodents. Using stable isotope
analysis on repeated samples from the same individuals, we explored some of the factors underlying feeding habits of individuals
under variable ecological conditions. We were unable to demonstrate that body weights of live-captured male and female martens
differed significantly between individuals feeding on marine-derived or terrestrial diets. Therefore, martens, as true generalist
predators, switched to alternative prey when their principal food was not readily available on a seasonal or annual basis.
Although salmon carcasses were not a preferred food for martens, they provided a suitable alternative to maintain body condition
during years when small rodents were not readily available.
Received: 1 May 1996 / Accepted: 24 February 1997 相似文献
50.
Differential expression of two P5CS genes controlling proline accumulation during salt-stress requires ABA and is regulated by ABA1, ABI1 and AXR2 in Arabidopsis 总被引:13,自引:0,他引:13