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91.
JP Herv s J. Martí -Clú a A. Mu oz-Garcí a MC Santa-Cruz 《Biotechnic & histochemistry》2002,77(1):27-35
We have optimised an indirect immunoperoxidase technique demonstrating bromodeoxyuridine (BrdU) incorporation into dividing cells for cerebellar tissue sections of four-day-old rats injected with this marker. This permits confident identification of granule-cell precursors engaged in DNA synthesis in the external granular layer of the developing cerebellum. Preservation of BrdU immunoreactivity is attained using methanol/acetic acid fixation and different pretreatments before immunostaining, while unlabeled nuclei can be recognized clearly after Feulgen or hematoxylin counterstaining. We established conditions to ensure satisfactory BrdU uptake without affecting cell-cycle progression during the postlabeling time period. The dose of BrdU employed provides saturation S-phase labeling from at least 1 h after BrdU delivery. Various kinetic parameters and phase durations have been determined in experiments involving a single injection or cumulative labeling sequences, and the cycle time was calculated based on two models of generative behavior: steady-state and exponential growth. The working hypothesis of steadystate kinetics can be adopted successfully if the existence of neuroblasts with different proliferation rates is taken into account. 相似文献
92.
M I Luster L H Hong R Osborne J A Blank G Clark M T Silver G A Boorman W F Greenlee 《Biochemical and biophysical research communications》1986,139(2):747-756
It was recently reported that suppression of murine bone marrow hematopoiesis is a very sensitive indicator for 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) toxicity (1). We report here that a structural analog of TCDD, 1-NH2-3,7,8-trichlorodibenzo-p-dioxin (NH2-TriCDD), is a specific and effective antagonist for TCDD-induced myelotoxicity and enzyme induction. When administered to mice or added directly into culture at a 100-fold excess, relative to TCDD, NH2-TriCDD completely abrogated the ability of TCDD to inhibit granulocyte-macrophage progenitor cells (CFU-C) formation, an indicator of hematopoiesis. Further, NH2-TriCDD inhibited TCDD-induced activation of cytochrome P1-450 monooxygenase activity. Studies designed to measure specific binding of TCDD to the cytosolic Ah receptor indicated that NH2-TriCDD effectively inhibited binding of TCDD to the receptor by acting as a competitive antagonist (Ki = 0.72 nM). 相似文献
93.
Transmissible spongiform encephalopathies (TSEs), including scrapie in sheep (Ovis aries), are fatal neurodegenerative diseases caused by the misfolding of the cellular prion protein (PrP(C)) into a a-rich conformer (PrP(Sc)) that accumulates into higher-order structures in the brain and other tissues. Distinct strains of TSEs exist, characterized by different pathologic profiles upon passage into rodents and representing distinct conformations of PrP(Sc). One biochemical method of distinguishing strains is the stability of PrP(Sc) as determined by unfolding in guanidine hydrochloride (GdnHCl), which is tightly and positively correlated with the incubation time of disease upon passage into mice. Here, we utilize a rapid, protease-free version of the stability assay to characterize naturally occurring scrapie samples, including a fast-acting scrapie inoculum for which incubation time is highly dependent on the amino acid at codon 136 of the prion protein. We utilize the stability methodology to identify the presence of two distinct isolates in the inoculum, and compare isolate properties to those of a host-stabilized reference scrapie isolate (NADC 13-7) in order to assess the stability/incubation time correlation in a natural host system. We demonstrate the utility of the stability methodology in characterizing TSE isolates throughout serial passage in livestock, which is applicable to a range of natural host systems, including strains of bovine spongiform encephalopathy and chronic wasting disease. 相似文献
94.
Sander G. Mills Mu Tsu Wu Malcolm MacCoss Richard J. Budhu Conrad P. Dorn Jr. Margaret A. Cascieri Sharon Sadowski Catherine D. Strader William J. Greenlee 《Bioorganic & medicinal chemistry letters》1993,3(12):2707-2712
A series of N,N′-diacylpiperazine-2-carboxamides are shown to be antagonists of the NK-1 (Substance P) receptor. Elaboration of the C2 sidechain with aminoalkyl groups leads to two series of potent antagonists, one containing simple dialkylamino groups and the second featuring 2-methoxybenzylamino derivatives with divergent SARs with respect to substitution at the C2 amide bond. 相似文献
95.
Attachment and extracellular matrix differences between tendon and synovial fibroblastic cells 总被引:3,自引:0,他引:3
M. A. Riederer-Henderson A. Gauger L. Olson C. Robertson T. K. Greenlee Jr. 《In vitro cellular & developmental biology. Plant》1983,19(2):127-133
Summary Fibroblasts of the synovium of sheathed tendons were isolated, and their biochemical properties were compared with those of
the fibroblasts of the remaining tendon. The synovial cells had a lower attachment efficiency than did the tendon cells. On
the day of cell isolation the synovial cells synthesized collagen as 10% of their total protein, whereas the tendon cells
synthesized 30% collagen. After growth in fetal bovine serum (FBS), the percentage of collagen synthesized by both populations
decreased; however, the synovial cells still made less collagen than did the tendon cells (5 versus 11%). On the basis of
cyanogen bromide peptide analysis, the synovial cells were found to synthesize Types I and III collagen in primary culture,
whereas the tendon cells synthesized only Type I. The synovial cells aslo synthesized two to three times less sulfated glycosaminoglycans
in culture than did the tendon cells. Thus, the two cell, populations differed in attachment efficiency and in their biosynthesis
of collagen and sulfated glycosaminoglycans. These differences reflect extracellular matrix differences that have been observed
in the tendon in vivo. In addition, the results augment existing data showing that not all fibroblasts have identical phenotypes.
This investigation was supported by National Institutes of Health Grant AM 25749. 相似文献
96.
Sodium-independent binding of gamma aminobutyric acid (GABA) to receptor-like sites in mammalian brain homogenates was much greater in membrane fractions which had been thoroughly washed with buffer, or detergent, and frozen and thawed several times, than in fresh unwashed membranes. As previously shown (Greenlee, Van Ness, & Olsen, Life Sciences , 1653 (1978), the washing procedure removed endogenous inhibitors of GABA binding which led to an apparent improvement in GABA binding affinity to a low affinity class of sites (KD ? 170 nM), and, additionally, the appearance of a high affinity (KD ? 10 nM) class of sites. This endogenous inhibitory material was found to inhibit both classes of GABA binding sites, but with greater potency towards the high affinity sites for GABA. Biochemical characterization of the inhibitor fraction revealed that the activity was heat-stable, insensitive to trypsin and disulfide reducing compounds, dialyzeable through membrane sieves which would retain molecules with a molecular weight of 5000, and eluted 100% from a molecular sieve column in the position of small molecules (salt volume), clearly separated from a 16,000 molecular weight marker. The inhibitor was over 80% inactivated by the enzyme GABAse, indicating that most, and perhaps all of the endogenous inhibitor of GABA binding was indeed GABA itself. The difficulty in removing endogenous GABA from brain membranes must be considered in studies on benzodiazepine receptors (since they are affected in vitro by GABA) and in any comparison of GABA or benzodiazepine receptors in human neuropsychiatric disorders, drug treatment or lesion studies. 相似文献
97.
98.
The respiratory sensation and some routine cardiorespiratory parameters were studied on native Highlanders from the Argentine
Andes and on Lowlanders from Europe, already tested during previous high altitude expeditions. The tests were performed at
various altitude levels from 2688m e.i., the village altitude for Highlanders, to 5600m during an expedition to Mt. Aconcagua
(6990m). At rest, the perception of 4 external inspiratory resistive loads (ranged between 2.5 and 13 cm.H2O.L-1.s) can allow
us to fix by discrimination the sensitivity index P(A) independently of response bias (B) according to Sensory Decision Theory
(SDT). The Andean highlanders did not experience the respiratory sensation at the same limits as the European lowlanders well
adaptated to high altitude. At higher altitudes than their village altitude, their respiratory sensation presented a lower
threshold of perception and a weaker discrimination which might be partly explained by the evolution of some parameters of
their cardio-respiratory function when altitude increased. Indeed, in response to high altitude hypoxia (5600m), they increased
their respiratory frequency and not their minuteventilation or mouth pressure. This chosen ventilatory pattern was opposite
to the one chosen by the Lowlanders and did not allow for sufficient adaptation to a more important altitude hypoxia than
that of their village altitude. In conclusion, the Andean highlanders wellbeing adapted to their village altitude, exhibited
a difficult acclimatization to higher altitudes which might be due to the characteristics of their respiratory sensation.
These results might explain their weak physical performances during ascent to the Mt. Aconcagua summit in spite of special
training. 相似文献
99.
Variant forms of a group I intron in nuclear small-subunit rRNA genes of the marine red alga Porphyra spiralis var. amplifolia 总被引:3,自引:0,他引:3
A group IC1 intron occurs in nuclear small-subunit (18S) ribosomal RNA (SSU
rRNA) genes of the marine red alga Porphyra spiralis var. amplifolia. This
intron occurs at the same position as the self- splicing group IC1 introns
in nuclear SSU rDNAs of the fungus Pneumocystis carinii and in the green
alga Chlorella ellipsoidea and shares sequence identity with the
Pneumocystis carinii intron in domains L1, P1, P2, and L2, outside the
conserved core. Three size variants, differing in amount of sequence in L1,
exist and are differentially distributed in geographically distinct
populations. Preliminary data suggest that the largest variant can
self-splice in vitro. Short open reading frames are present but do not
correspond to known genes. Repeated nucleotide motifs, reminiscent of
duplicated target sites of transposons or Alu elements, are associated with
the intron and with one of the variant forms of L1. Insertions are present
in nuclear SSU rDNAs of several other Porphyra species and of the red alga
Bangia atropurpurea; insertionless rDNA variants also occur in several
Porphyra species. Our observations are most readily explained by intron
mobility, although it remains unclear how transfer could have been mediated
between genomes of organisms as ecologically diverse as marine red algae,
freshwater green algae, and a mammalian-pathogenic fungus.
相似文献