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101.
102.
Malone JC Armento ME Nemeth RM Billington EJ Carpenter CN Andrews KB 《Behavioural processes》2004,65(1):95-109
Pigeons accustomed to food reinforcement for responding in the presence of a 25-Hz flickering light were exposed to several sets of flicker-frequency stimuli arranged as increasing and decreasing series. In the first experiment, food was occasionally delivered for key pecks during 30-s periods of 25-Hz flicker appearing at the beginning, midway, and at the end of an ascending and descending series of nine frequencies, ranging from 13 to 37 Hz. These stimuli appeared for 15-s periods with no food available (extinction). Gradients of responding to flicker values in the ascending series differed from those in the descending series, showing displacements in peak responding toward the lower and higher frequency values, respectively. The same effects occurred when the sequence was changed so that a descending series was followed by an ascending series of frequencies. These effects are consonant with an adaptation level (AL) interpretation and were replicated in a second experiment in which durations of the extinction presentations were increased to 30s. In a final condition, only a descending series was presented and displacement of peak responding from 25 Hz to a higher frequency stimulus, 28 Hz, was observed. 相似文献
103.
Proteomics-based identification of differentially expressed genes in human gliomas: down-regulation of SIRT2 gene 总被引:9,自引:0,他引:9
Hiratsuka M Inoue T Toda T Kimura N Shirayoshi Y Kamitani H Watanabe T Ohama E Tahimic CG Kurimasa A Oshimura M 《Biochemical and biophysical research communications》2003,309(3):558-566
A number of chromosomal abnormalities including 19q deletions have been associated with the formation of human gliomas. In this study, we employed a proteomics-based approach to identify possible genes involved in glioma tumorigenesis which may serve as potential diagnostic molecular markers for this type of cancer. By comparing protein spots from gliomas and non-tumor tissues using two-dimensional (2D) gel electrophoresis, we identified 11 up-regulated proteins and four down-regulated proteins in gliomas. Interestingly, we also discovered that a group of cytoskeleton-related proteins are differentially regulated in gliomas, suggesting the involvement of cytoskeleton modulation in glioma pathogenesis. We then focused on the cytoskeleton-related protein, SIRT2 (sirtuin homologue 2) tubulin deacetylase, which was down-regulated in gliomas. SIRT2 is located at 19q13.2, a region known to be frequently deleted in human gliomas. Subsequent Northern blot analysis revealed that RNA expression of SIRT2 was dramatically diminished in 12 out of 17 gliomas and glioma cell lines, in agreement with proteomic data. Furthermore, ectopic expression of SIRT2 in glioma cell lines led to the perturbation of the microtubule network and caused a remarkable reduction in the number of stable clones expressing SIRT2 as compared to that of a control vector in colony formation assays. These results suggest that SIRT2 may act as a tumor suppressor gene in human gliomas possibly through the regulation of microtubule network and may serve as a novel molecular marker for gliomas. Additional proteins were also identified, whose function in gliomas was previously unsuspected. 相似文献
104.
Vos MD Ellis CA Elam C Ulku AS Taylor BJ Clark GJ 《The Journal of biological chemistry》2003,278(30):28045-28051
Ras proteins regulate a wide range of biological processes by interacting with a broad assortment of effector proteins. Although activated forms of Ras are frequently associated with oncogenesis, they may also provoke growth-antagonistic effects. These include senescence, cell cycle arrest, differentiation, and apoptosis. The mechanisms that underlie these growth-inhibitory activities are relatively poorly understood. Recently, two related novel Ras effectors, NORE1 and RASSF1, have been identified as mediators of apoptosis and cell cycle arrest. Both of these proteins exhibit many of the properties normally associated with tumor suppressors. We now identify a novel third member of this family, designated RASSF2. RASSF2 binds directly to K-Ras in a GTP-dependent manner via the Ras effector domain. However, RASSF2 only weakly interacts with H-Ras. Moreover, RASSF2 promotes apoptosis and cell cycle arrest and is frequently down-regulated in lung tumor cell lines. Thus, we identify RASSF2 as a new member of the RASSF1 family of Ras effectors/tumor suppressors that exhibits a specificity for interacting with K-Ras. 相似文献
105.
Quantitative trait loci for polyamine content in an RFLP-mapped potato population and their relationship to tuberization 总被引:1,自引:0,他引:1
Peter J. Davies Ivan imko Suzanne M. Mueller G. Craig Yencho Candice Lewis Susan McMurry Mark A. Taylor Elmer E. Ewing 《Physiologia plantarum》1999,106(2):210-218
DNA-based genetic markers are now widely used by geneticists to locate genes for quantitative traits, and may also serve as a valuable tool for dissecting complex physiological phenomena. Van den Berg et al. (1996a QTL analysis of potato tuberization. Theor Appl Gen 93: 307–316), using restriction fragment length polymorphism (RFLP)-mapped populations of potato, detected eleven quantitative trait loci (QTLs) for tuberization. Taylor et al. (1992 Expression and sequence analysis of cDNAs induced during the early stages of tuberisation in different organs of the potato plant [ Solanum tuberosum L.]. Plant Mol Biol 20: 641–651) have identified one of the genes associated with tuberization as that for the enzyme S-adenosylmethionine decarboxylase (SAMdc), an enzyme of the polyamine biosynthetic pathway. Chromosomal loci for SAMdc and arginine decarboxylase were established on the potato and tomato chromosomal maps, respectively, by hybridizing cDNA probes for these genes to RFLP digests. The polyamine content of leaves from an RFLP-mapped potato population was analyzed by fluorescence detection following HPLC, with quantitation using an internal standard. The data were analyzed by the 'qGene' statistical program, and QTLs for polyamines were detected on seven chromosomes. At least six QTLs were found for spermine, two for spermidine, and two for putrescine. A spermidine QTL was on chromosome 5 linked to marker TG441 , very close to the place where SAMdc mapped. There was some congruence between QTLs for spermine and those previously detected for tuberization and dormancy, but relationships were not consistent. 相似文献
106.
107.
Thomas A. Emm Candice L. Krauthauser Shiew-Mei Huang 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1996,675(2):273
A sensitive and selective high-performance liquid chromatographic method for the determination of XR510 (I), a new non-peptide angiotensin II (AII) receptor antagonist with balanced affinity for AT1 and AT2 receptor subtypes is described. I and the internal standard, XR513, were extracted from acidified plasma by combined liquid-liquid/solid-phase extraction and chromatographed on a phenyl column with ultraviolet absorbance detection at a wavelength of 272 nm. The mobile phase consisted of a mixture of acetonitrile and sodium phosphate buffer. For both rat and dog plasma, the limit of quantitation was 5 ng/ml. This method has been validated and successfully utilized to investigate the disposition of I. 相似文献
108.
Laura K. Thompson Candice L. Burgess Elizabeth N. Skinner 《American journal of botany》1992,79(7):828-832
Previous studies indirectly indicated that phytochrome plays a role in peanut (Arachis hypogaea L. cv. Virginia) gynophore elongation and in ovule and embryo development. Recent advances in the use of monoclonal antibody procedures used in this study have allowed precise localization of phytochrome in the developing peanut gynophore and ovular tissues. Peanut phytochrome from etiolated tissues was found to have a molecular weight of 124 kD as determined by immunoblotting procedures using a monoclonal antibody to pea (Pisum sativum L. cv. Alaska) phytochrome. Immunoblotting procedures revealed that no detectable phytochrome was present in the gynophore tissues or immature ovules during the elongation of the peanut gynophores. After the gynophores penetrated the soil for 8–12 d, phytochrome was detected in increasing amounts in the ovular tissues but not the gynophore tissues. Immunohistological analysis revealed that phytochrome was localized in the developing embryo and adjacent integument tissues. These findings contradict earlier reports that suggested phytochrome was initially present in the gynophore tissues after fertilization where it was believed to inhibit ovular development and stimulate gynophore elongation. 相似文献
109.
Kim SH Shin DH Liu J Oganesyan V Chen S Xu QS Kim JS Das D Schulze-Gahmen U Holbrook SR Holbrook EL Martinez BA Oganesyan N DeGiovanni A Lou Y Henriquez M Huang C Jancarik J Pufan R Choi IG Chandonia JM Hou J Gold B Yokota H Brenner SE Adams PD Kim R 《Journal of structural and functional genomics》2005,6(2-3):63-70
The initial aim of the Berkeley Structural Genomics Center is to obtain a near-complete structural complement of two minimal
organisms, closely related pathogens Mycoplasma genitalium and M. pneumoniae. The former has fewer than 500 genes and the latter fewer than 700 genes. To achieve this goal, the current protein targets
have been selected starting with those predicted to be most tractable and likely to yield new structural and functional information.
During the past 3 years, the semi-automated structural genomics pipeline has been set up from cloning, expression, purification,
and ultimately to structural determination. The results from the pipeline substantially increased the coverage of the protein
fold space of M. pneumoniae and M. genitalium. Furthermore, about 1/2 of the structures of ‘unique’ protein sequences revealed new and novel folds, and over 2/3 of the
structures of previously annotated ‘hypothetical proteins’ inferred their molecular functions. 相似文献
110.