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71.
S Saika S Saika C Y Liu M Azhar L P Sanford T Doetschman R L Gendron C W Kao W W Kao 《Developmental biology》2001,240(2):419-432
To examine the roles of TGFbeta isoforms on corneal morphogenesis, the eyes of mice that lack TGFbetas were analyzed at different developmental stages for cell proliferation, migration and apoptosis, and for expression patterns of keratin 12, lumican, keratocan and collagen I. Among the three Tgfb(-/-) mice, only Tgfb2(-/-) mice have abnormal ocular morphogenesis characterized by thin corneal stroma, absence of corneal endothelium, fusion of cornea to lens (a Peters'-like anomaly phenotype), and accumulation of hyaline cells in vitreous. In Tgfb2(-/-) mice, fewer keratocytes were found in stroma that has a decreased accumulation of ECM; for example, lumican, keratocan and collagen I were greatly diminished. The absence of TGFbeta2 did not compromise cell proliferation, nor enhance apoptosis. The thinner stroma resulting from decreased ECM synthesis may account for the decreased cell number in the stroma of Tgfb2 null mice. Keratin 12 expression was not altered in Tgfb2(-/-) mice, implicating normal corneal type epithelial differentiation. Delayed appearance of macrophages in ocular tissues was observed in Tgfb2(-/-) mice. Malfunctioning macrophages may account for accumulation of cell mass in vitreous of Tgfb2 null mice. 相似文献
72.
73.
The protective effect of polyamines against Cd toxicity of rice (Oryza sativa) leaves was investigated. Cd toxicity to rice leaves was determined by the decrease in protein content. CdCl2 treatment results in (1) increased Cd content, (2) induction of Cd toxicity, (3) increase in H2O2 and malondialdehyde (MDA) contents, (4) decrease in ascorbic acid (ASC) and reduced glutathione (GSH) contents, and (5) increase
in the activities of antioxidative enzymes (superoxide dismutase, glutathione reductase, ascorbate peroxidase, catalase, and
peroxidase). Spermidine (Spd) and spermine (Spm), but not putrescine (Put), were effective in reducing CdCl2-induced toxicity. Spd and Spm prevented CdCl2-induced increase in the contents of H2O2 and MDA, decrease in the contents of ASC and GSH, and increase in the activities of antioxidative enzymes. Spd and Spm pretreatments
resulted in a decrease in Cd content when compared with H2O pretreatment, indicating that Spd and Spm may reduce the uptake of Cd. Results of the present study suggest that Spd and
Spm are able to protect Cd-induced oxidative damage and this protection is most likely related to the avoidance of H2O2 generation and the reduction of Cd uptake. 相似文献
74.
The role of hydrogen peroxide (H(2)O(2)) in abscisic acid (ABA)-induced anthocyanin accumulation in detached and intact leaves of rice seedlings was investigated. Treatment with ABA resulted in an accumulation of anthocyanins in detached rice leaves. Dimethylthiourea, a chemical trap for H(2)O(2), was observed to be effective in inhibiting ABA-induced accumulation of anthocyanins. Inhibitors of NADPH oxidase (diphenyleneiodonium chloride and imidazole), phosphatidylinositol 3-kinase (wortmannin and LY 294002), and a donor of nitric oxide (N-tert-butyl-alpha-phenylnitrone), which have previously been shown to prevent ABA-induced H(2)O(2) accumulation in detached rice leaves, inhibited ABA-induced anthocyanin increase. Exogenous application of H(2)O(2), however, was found to increase the anthocyanin content of detached rice leaves. In terms of H(2)O(2) accumulation, intact (attached) leaves of rice seedlings of cultivar Taichung Native 1 (TN1) are ABA sensitive and those of cultivar Tainung 67 (TNG67) are ABA insensitive. Upon treatment with ABA, H(2)O(2) and anthocyanins accumulated in leaves of TN1 seedlings but not in leaves of TNG67. Our results, obtained from detached and intact leaves of rice seedlings, suggest that H(2)O(2) is involved in ABA-induced anthocyanin accumulation in this species. 相似文献
75.
76.
Ming Lei Daniel Hewitt Christopher Cornell Ken Skidmore Yung‐Hsiang Kao Jimmy Sugahara Diane Beane Junyan Ji 《Biotechnology progress》2013,29(6):1503-1511
Polysorbate 20 (PS‐20) is often included in the formulation for therapeutic proteins to reduce protein aggregation and surface adsorption. During the production process of therapeutic proteins, various membrane filters are used to filter product pools containing PS‐20. The purpose of this study is to quantify the effects of these membrane filtration processes on the concentration and composition of PS‐20. A quantitative understanding of this process provides the knowledge base for better controlling the consistency of formulation excipients in drug products. PS‐20 solutions (without protein) were filtered through either 0.2 µm sterilizing filters or membrane filters with 30 kDa MWCO. The concentration of PS‐20 was measured by a mixed‐mode chromatography method and a nuclear magnetic resonance spectroscopy (NMR) assay. The composition of PS‐20 was characterized by 1H‐NMR and a reverse‐phase chromatography method. Non‐specific adsorption of PS‐20 on both the sterilizing filter and 30 kDa MWCO membrane filter was quantified. Composition of PS‐20 was altered after 30 kDa MWCO membrane filtration, possibly because the different interactions between heterogeneous PS‐20 components and the 30 kDa MWCO membrane were not uniform. As a result, the retentate after the 30 kDa MWCO membrane filtration step contains no POE sorbitan and increased amount of POE sorbitan di‐esters and tri‐esters. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29:1503–1511, 2013 相似文献
77.
The role of glycogen synthase kinase 3beta in insulin-stimulated glucose metabolism. 总被引:3,自引:0,他引:3
S A Summers A W Kao A D Kohn G S Backus R A Roth J E Pessin M J Birnbaum 《The Journal of biological chemistry》1999,274(25):17934-17940
To characterize the contribution of glycogen synthase kinase 3beta (GSK3beta) inactivation to insulin-stimulated glucose metabolism, wild-type (WT-GSK), catalytically inactive (KM-GSK), and uninhibitable (S9A-GSK) forms of GSK3beta were expressed in insulin-responsive 3T3-L1 adipocytes using adenovirus technology. WT-GSK, but not KM-GSK, reduced basal and insulin-stimulated glycogen synthase activity without affecting the -fold stimulation of the enzyme by insulin. S9A-GSK similarly decreased cellular glycogen synthase activity, but also partially blocked insulin stimulation of the enzyme. S9A-GSK expression also markedly inhibited insulin stimulation of IRS-1-associated phosphatidylinositol 3-kinase activity, but only weakly inhibited insulin-stimulated Akt/PKB phosphorylation and glucose uptake, with no effect on GLUT4 translocation. To further evaluate the role of GSK3beta in insulin signaling, the GSK3beta inhibitor lithium was used to mimic the consequences of insulin-stimulated GSK3beta inactivation. Although lithium stimulated the incorporation of glucose into glycogen and glycogen synthase enzyme activity, the inhibitor was without effect on GLUT4 translocation and pp70 S6 kinase. Lithium stimulation of glycogen synthesis was insensitive to wortmannin, which is consistent with its acting directly on GSK3beta downstream of phosphatidylinositol 3-kinase. These data support the hypothesis that GSK3beta contributes to insulin regulation of glycogen synthesis, but is not responsible for the increase in glucose transport. 相似文献
78.
Liu GY Liao YF Hsu PC Chang WH Hsieh MC Lin CY Hour TC Kao MC Tsay GJ Hung HC 《Apoptosis : an international journal on programmed cell death》2006,11(10):1773-1788
Antizymes delicately regulate ornithine decarboxylase (ODC) enzyme activity and polyamine transportation. One member of the
family, antizyme-1, plays vital roles in molecular and cellular functions, including developmental regulation, cell cycle,
proliferation, cell death, differentiation and tumorigenesis. However, the question of how does it participate in the cell
apoptotic mechanism is still unsolved. To elucidate the contribution of human antizyme-1 in haematopoietic cell death, we
examine whether inducible overexpression of antizyme enhances apoptotic cell death. Antizyme reduced the viability in a dose-
and time-dependent manner of human leukemia HL-60 cells, acute T leukemia Jurkat cells and mouse macrophage RAW 264.7 cells.
The apoptosis-inducing activities were determined by nuclear condensation, DNA fragmentation, sub-G1 appearance, loss of mitochondrial membrane potential (Δψ
m
), release of mitochondrial cytochrome c into cytoplasm and proteolytic activation of caspase 9 and 3. Following conditional antizyme overexpression, all protein
levels of cyclin-dependent kinases (Cdks) and cyclins are not significantly reduced, except cyclin D, before their entrance
into apoptotic cell death. However, introduced cyclin D1 into Jurkat T tetracycline (Tet)-On cell system still couldn’t rescue
cells from apoptosis. Antizyme doesn’t influence the expression of tumor suppressor p53 and its downstream p21, but it interferes
in the expressions of Bcl-2 family. Inducible antizyme largely enters mitochondria resulting in cytochrome c release from mitochondria to cytosol following Bcl-xL decrease and Bax increase. According to these data, we suggest that
antizyme induces apoptosis mainly through mitochondria-mediated and cell cycle-independent pathway. Furthermore, antizyme
induces apoptosis not only by Bax accumulation reducing the function of the Bcl-2 family, destroying the Δψ
m
, and releasing cytochrome c to cytoplasm but also by the activation of apoptosomal caspase cascade. 相似文献
79.
Photosynthetic CO2 uptake and chlorophyll (Chl) a fluorescence of C4 perennial grasses, Miscanthus floridulus (Labill) Warb and M. transmorrisonensis Hayata, from altitudes in central Taiwan
of 390 and 2700 m, respectively, were studied at 10 and 25 °C to find if the species differ in their photosynthetic responses
to a low temperature, and whether their photosystems 2 become more susceptible to the photoinhibition at low temperatures.
For both species, the maximum photosynthetic rate (Pmax) was reduced when the leaves were exposed to 10 °C. At irradiances higher than 400 μmol m-2 s-1, the values of Fv/Fm were reduced in both species at 10 °C but not at 25 °C, which indicated the photoinhibition at 10 °C. Reductions in Pmax and the values of Fv/Fm at 10 °C were lesser in M. transmorrisonensis than in M. floridulus.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
80.
Mitogillin and the related fungal ribotoxins are highly specific ribonucleases which inactivate the ribosome enzymatically by cleaving the 23-28 S RNA of the large ribosomal subunit at a single phosphodiester bond. The site of cleavage occurs between G4325 and A4326 (rat ribosome numbering) which are present in one of the most conserved sequences (the alpha-sarcin loop) among the large subunit ribosomal RNAs of all living species. Amino acid sequence comparison of ribotoxins and guanyl/purine ribonucleases have identified domains or residues likely involved in ribonucleolytic activity or cleavage specificity. Fifteen deletion mutants (each 4 to 8 amino acid deletions) in motifs of mitogillin showing little amino acid sequence homology with guanyl/purine ribonucleases were constructed by site-directed mutagenesis. Analyses of the purified mutant proteins identified those regions in fungal ribotoxins contributing to ribosome targeting and modulating the catalytic activity of the toxin; some of the identified motifs are homologous to sequences in ribosomal proteins and elongation factors. This mutational study of mitogillin together with the recently published x-ray structure of restrictocin (a close relative of mitogillin) supports the hypothesis that the specific cleavage properties of ribotoxins are the result of natural genetic engineering in which the ribosomal targeting elements of ribosome-associated proteins were inserted into nonessential regions of T1-like ribonucleases. 相似文献