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921.
Function of 90-kDa heat shock protein in cellular differentiation of human embryonal carcinoma cells
Yamada T Hashiguchi A Fukushima S Kakita Y Umezawa A Maruyama T Hata J 《In vitro cellular & developmental biology. Animal》2000,36(2):139-146
Summary Heat shock proteins (HSPs) have been recognized as molecules that maintain cellular homeostasis during changes in the environment.
Here we report that HSP90 functions not only in stress responses but also in certain aspects of cellular differentiation.
We found that HSP90 slowed remarkably high expression in undifferentiated human embryonal carcinoma (EC) cells, which were
subsequently dramatically down-regulated during in vitro cellular differentiation, following retinoic acid (RA) treatment,
at the protein level. Surprisingly, heat shock treatment also triggered the down-regulation of HSP90 within 48 h at the protein
level. Furthermore, the heat treatment induced cellular differentiation into neural cells. This down-regulation of HSP90 by
heat treatment was shifted to an up-regulation attern after cellular differentiation in response to RA treatment. In order
to clarify the functions of HSP90 in cellular differentiation, we conducted various experiments, including overexpression
of HSP90 via gene transfer. We showed that the RA-induced differentiation of EC cells into a neural cell lineage was inhibited
by overexpression of the HSP90α or-β isoform via the gene transfer method. On the other hand, the overexpression of HSP90β
alone impaired cellular differentiation into trophoectoderm. These results show that down-regulation of HSP90 is a physiological
critical event in the differentiation of human EC cells and that specific HSP90 isoforms may be involved in differentiation
into specific cell lineages. 相似文献
922.
Binding to a specific receptor is an essential step for most enteropathogens to initiate an intestinal infection. We analyzed the inhibitory effect of human milk and its protein components on adhesion of two diarrheagenic Escherichia coli strains, diffusely adherent E. coli (DAEC) and enteroaggregative E. coli (EAEC), to HeLa cells. Defatted milk, whey proteins, immunoglobulin and non-immunoglobulin fractions, in concentrations lower than usually found in whole milk, inhibited both DAEC and EAEC adhesion, indicating that human milk components may contribute to the defense of the infants against enteropathogens. 相似文献
923.
Suzuki K Tsuyuguchi K Matsumoto H Niimi A Tanaka E Amitani R 《FEMS microbiology letters》2000,184(1):69-72
The effect of omeprazole, a clinically used proton pump inhibitor, alone or in combination with clarithromycin was evaluated against Mycobacterium avium, Mycobacterium intracellulare and Mycobacterium tuberculosis, using a human alveolar macrophage model of infection. Omeprazole exhibited no significant effect on the growth of the two M. avium complex strains or on the mycobactericidal activity of clarithromycin against them. In contrast, omeprazole significantly promoted the growth of Mycobacterium tuberculosis and the anti-mycobacterial activity of clarithromycin against it in human alveolar macrophages. It was speculated that intracellular acidic milieu around M. tuberculosis might be one reason for the lower activity of clarithromycin in the treatment of human tuberculosis. 相似文献
924.
In this paper, we present new nonparametric estimators of the stage-occupation probabilities in the three-stage irreversible illness-death model. These estimators use a fractional risk set and a reweighting approach and are valid under stage-dependent censoring. Using a simulated data set, we compare the behavior of our estimators with previously proposed estimators. We also apply our estimators to data on time to Pneumocystis pneumonia and death obtained from an AIDS cohort study. 相似文献
925.
Novel mechanism that Trypanosoma cruzi uses to adhere to the extracellular matrix mediated by human galectin-3 总被引:1,自引:0,他引:1
Binding of Trypanosoma cruzi trypomastigotes to laminin is enhanced by galectin-3, a beta-galactoside binding lectin. The galectin-3 enhanced binding of trypanosomes to laminin is inhibited by lactose. Co-immunoprecipitations indicate that galectin-3 binds to the 45, 32 and 30 kDa trypanosome surface proteins. Binding of galectin-3 to the 45, 32 and 30 kDa surface proteins is inhibited by lactose. Polyclonal and a monoclonal antibodies to galectin-3 immunoprecipitated a major 64 kDa trypanosome surface protein. T. cruzi monoclonal antibody to mucin recognized the 45 kDa surface protein. The 45, 32 and 30 kDa surface proteins interact with galectin-3 in order to enhance trypanosome adhesion to laminin. 相似文献
926.
The Middle Stone Age (MSA) layers at Blombos Cave contain abundant bifacial Still Bay points, formal and ad hoc bone artefacts, and an intentionally incised bone piece. These artefacts add weight to arguments that some aspects of modern human behavior developed earlier in sub-Saharan Africa than elsewhere. Four human teeth were recovered from the MSA strata at Blombos during the 1997-1998 excavations. Two are heavily worn deciduous teeth, and two are incomplete permanent premolar crowns. The Blombos di(1)is comparatively large in relation to modern African homologues, falling within the lower part of the observed Neandertal range. The dm(1)and P(3)are comparable to modern teeth and smaller than most Neandertal crowns. The premolars preserve horizontal circum-cervical striae that suggest palliative toothpick use. The di(1)evinces labial scratches that resemble neither the "cutmarks" that have been observed on Neandertal incisors, nor the striae that have been recorded on modern human teeth. 相似文献
927.
We theoretically study the antigenic drift of viruses within an infected host, as observed in human immunodeficiency virus
(HIV) and equine infectious anemia virus (EIAV) infections, assuming that a finite number of antigen-determining sites at
the viral envelop gene are responsible for the specific immune response. The pattern of antigen evolution becomes more complex
than that predicted from the previous one-dimensional antigen space models. If the viral growth rate is sufficiently large,
the demographic stochasticity for the fate of a new antigen mutant can be neglected. The high dimensionality in the way a
virus escapes the immune defense in genotype space could then causes a rapid increase in the antigenic diversity and the total
viral density, until finally the whole antigen genotypes are used up. The viral population is then driven to extinction in
a host by the enhanced immune response to all genotypes. In contrast, if the viral growth rate is moderate or small so that
only a small fraction of new antigen mutants can survive during the initial endangered period of random extinction, the viral
antigenic diversity and the total density remain bounded, thereby enabling them to persist for a prolonged period by shifting
the dominant antigen types. The phylogenetic pattern of antigen divergence is well characterized by the mean number of surviving
antigen mutants from an antigen genotype. The substitution rate at antigen-determining sites increases as the efficiency of
host immune response increases.
Received: 11 January 2000 / Accepted: 25 May 2000 相似文献
928.
Silvestre MD Lagarda MJ Farré R Martínez-Costa C Brines J Molina A Clemente G 《Biological trace element research》2000,76(3):217-227
The aim of this study was to establish the possible effects of the sampling protocol (between-breast, within-feed, and diurnal
differences) and the mother’s personal factors (age, parity, iron supple-mentation, smoking habits, and lactation period)
on the copper, iron, and zinc contents in human milk.
One hundred thirty-six human milk samples identified by their origin and sampling conditions were analyzed. The samples were
obtained from the 2nd to 15th d postpartum from 62 women. The data on the individuals required for the study were available.
Mineral determinations were analyzed by flame atomic absorption spectrometry following a standarized protocol.
The results showed that iron contents were higher in hind-milk samples and at the nighttime feeding and depended on the breast
from which the sample was taken. The copper and zinc concentrations showed no significant variations. There was no significant
relationship among the mothers’ age, parity, smoking habits, iron supplementation, and copper content. Milk from older women
had lower zinc contents than that of younger women. Increased amounts of iron were found in multiparous women. Between colostrum
and transitional milk, a sharp decrease in zinc content was observed, whereas copper and iron contents remained constant.
All of these results make it clear that standardized sampling protocols are needed in order to obtain comparable values. 相似文献
929.
An alternative route for multistep tumorigenesis in a novel case of hereditary renal cell cancer and a t(2;3)(q35;q21) chromosome translocation. 总被引:4,自引:0,他引:4
D Bodmer M J Eleveld M J Ligtenberg M A Weterman B A Janssen D F Smeets P E de Wit A van den Berg E van den Berg M I Koolen A Geurts van Kessel 《American journal of human genetics》1998,62(6):1475-1483
Through allele-segregation and loss-of-heterozygosity analyses, we demonstrated loss of the translocation-derivative chromosome 3 in five independent renal cell tumors of the clear-cell type, obtained from three members of a family in which a constitutional t(2;3)(q35;q21) was encountered. In addition, analysis of the von Hippel-Lindau gene, VHL, revealed distinct insertion, deletion, and substitution mutations in four of the five tumors tested. On the basis of these results, we conclude that, in this familial case, an alternative route for renal cell carcinoma development is implied. In contrast to the first hit in the generally accepted two-hit tumor-suppressor model proposed by Knudson, the familial translocation in this case may act as a primary oncogenic event leading to (nondisjunctional) loss of the der(3) chromosome harboring the VHL tumor-suppressor gene. The risk of developing renal cell cancer may be correlated directly with the extent of somatic (kidney) mosaicism resulting from this loss. 相似文献
930.
Hirofumi Usui Rintaro Inoue Osamu Tanabe Yasumasa Nishito Masahiro Shimizu Hideyuki Hayashi Hiroyuki Kagamiyama Masao Takeda 《FEBS letters》1998,430(3)
Human erythrocyte protein phosphatase 2A, which comprises a 34-kDa catalytic C subunit, a 63-kDa regulatory A subunit and a 74-kDa regulatory B″ (δ) subunit, was phosphorylated at serine residues of B″ in vitro by cAMP-dependent protein kinase (A-kinase). In the presence and absence of 0.5 μM okadaic acid (OA), A-kinase gave maximal incorporation of 1.7 and 1.0 mol of phosphate per mol of B″, respectively. The Km value of A-kinase for CAB″ was 0.17±0.01 μM in the presence of OA. The major in vitro phosphorylation sites of B″ were identified as Ser-60, -75 and -573 in the presence of OA, and Ser-75 and -573 in the absence of OA. Phosphorylation of B″ did not dissociate B″ from CA, and stimulated the molecular activity of CAB″ toward phosphorylated H1 and H2B histones, 3.8- and 1.4-fold, respectively, but not toward phosphorylase a. 相似文献