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31.
Peter W. Goodenough Peter J. Kilshaw Fiona McEwan A. Jane Owen 《Bioscience reports》1986,6(8):759-766
The proteinases fromCarica papaya include papain, isoenzymes of chymopapain and two proteinases A and B distinguished by their unusually high pI. The identity of one of the most basic proteinases has been questioned. The present report describes the preparation and characterisation of two monoclonal antibodies that react specifically with papaya proteinases A and B respectively and a third that identifies a common structural feature found in papain and proteinase A. 相似文献
32.
It was found that ethionine partially inhibits the transport of the inducer (TMG) of β-galactosidase into the cells ofEscherichia coli ML-30. The synthesis of β-galactosidase-specific messenger RNA is not inhibited. Ethionine appears to be incorporated into
proteins synthesized by the strains used. The incorporation of ethionine into the molecule of β-galactosidase results in the
synthesis of an enzymically inactive, immunologically cross-reacting protein. 相似文献
33.
Auxin Production by Mycorrhizal Fungi 总被引:5,自引:0,他引:5
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Nathalie Bonnefoy Jane Copsey Michael J. Hynes Mervl A. Davis 《Molecular genetics and genomics : MGG》1995,246(2):223-227
The upstream regulatory region of the amdS gene of Aspergillus nidulans contains a CCAAT sequence known to be important in setting both basal and derepressed levels of expression. We have investigated whether the CCAAT-binding HAP2/3/4 complex of the yeast Saccharomyces cerevisiae can recognise this sequence in an amdS context. Sequences from the 5′ region of amdS were cloned in front of the CYCI-lacZ fusion gene bearing a minimal promoter and transformed into wild-type and hap2 strains of yeast. This study has indicated that amdS sequences are capable of promoting regulated expression of the fusion gene in response to carbon limitation. The yeast HAP2/3/4 complex can recognise the amdS CCAAT sequence and activate expression from this sequence. In addition, the results indicate that other yeast proteins can also regulate expression from the A. nidulans amdS 5′ sequences under carbon-limiting conditions. 相似文献
38.
Abstract. Eragrostis intermedia (Plains lovegrass) is a midheight perennial bunchgrass native to semi-arid grasslands of the southwestern USA, that becomes an abundant and dominant component of these grasslands in areas long protected from livestock grazing. Substantial mortality of plains lovegrass occurred on a large livestock exclosure in southeastern Arizona, after a period of declining precipitation, but only in areas that had not burned in the previous three years. Lovegrass abundance subsequently increased on both undisturbed and burned sites, but remained substantially higher on the burned area. Long-term abundance of plains lovegrass may depend on episodic fire, particularly during periods of reduced precipitation. 相似文献
39.
Luc Malaval Dominique Modrowski Ashwani K. Gupta Jane E. Aubin 《Journal of cellular physiology》1994,158(3):555-572
The regulation of cell surface fibroblast growth factor (FGF) receptors during the differentiation of F9 teratocarcinoma cells was investigated. The capacity of F9 cells to bind 125I-basic FGF (FGF-2) increased upon induction of differentiation with dibutyryl cAMP and retinoic acid. No change in binding capacity was observed in the first 24 h after addition of differentiating agents, but a sixfold increase in binding capacity was observed after 48 h and a fivefold increase after 72 h. Scatchard analysis of the binding data indicated that the increased binding of 125I-FGF-2 was due to an increase in the number of receptors with no change in their affinity. When 125I-FGF-2 was cross-linked to cell surface receptors, an increase in FGF-2-receptor complexes with molecular weights of 140,000–160,000 was also observed in the differentiated F9 cells. Undifferentiated F9 cells are known to secrete FGF-4 and cease expression of this molecule upon differentiation. To determine whether the low level of receptors in undifferentiated cells might be related to their production of FGF ligands, the ability of suramin, a drug that can disrupt FGF-receptor interactions, to modulate receptor number on F9 cells was investigated. Suramin treatment increased 125I-FGF-2 binding capacity of undifferentiated F9 cells threefold but had little effect on the binding capacity of differentiated cells. In addition, antibodies to FGF-4 increased the 125I-FGF-2 binding capacity of undifferentiated F9 cells by 58%. These results suggest that undifferentiated F9 cells might be responding in an autocrine manner to their own FGF ligands resulting in downregulation of cell surface FGF receptors. The increased number of receptors observed in differentiated cells may partly result from the decreased production of FGF ligands by these cells. © 1994 Wiley-Liss, Inc. 相似文献
40.
Effect of tumor necrosis factor-α and interferon-γ on the growth of a human salivary gland cell line
Ava J. Wu Regina H. Kurrasch Joseph Katz Philip C. Fox Bruce J. Baum Jane C. Atkinson 《Journal of cellular physiology》1994,161(2):217-226
Interferon-γ (IFN-γ) is a product of activated T-lymphocytes, and tumor necrosis factor-α (TNF-α) is a product of both lymphocytes and macrophages. These cell types are often present at sites of tissue damage secondary to chronic infection or autoimmune disease. The purpose of this study was to characterize the effects of TNF-α and IFN-γ on a human submandibular gland epithelial cell line (HSG). IFN-γ caused a concentration-dependent decrease in HSG cell growth (~70% in 6 days). Conversely, TNF-α alone had little effect on the growth of these cells. When these cytokines were added in combination (20 units/ml TNF-α and 1,000 units/ml of IFN-γ), there was a synergistic antiproliferative effect; no apparent cell growth was observed. The cytokine-induced antiproliferative effect was reversible. After the apparent cessation of cell growth for 3–6 days, removal of the cytokines permitted complete growth recovery. Further, cells that recovered and exhibited growth patterns that were similar to control cells remained susceptible to the antiproliferative effects of the cytokines. Flow cytometry revealed that the percentage of cells in G0/G1 with the combination of cytokines was significantly increased by 24 h. The antiproliferative effect of IFN-γ alone and that of IFN-γ and TNF-α in combination were blocked completely using an antibody to the IFN-γ receptor. A hypothesized mechanism of tissue damage in autoimmune inflammatory disorders is via up-regulation of cell surface markers such as intercellular adhesion molecule type I (ICAM-1) and histocompatibility antigen HLA-DR which can exacerbate the inflammatory process. Treatment of HSG cells with IFN-γ, with or without TNF-α, resulted in increased levels of ICAM-1 and the acquisition of HLA-DR expression. These aggregate data suggest that IFN-γ alone can regulate the expression of cell surface markers involved in the inflammatory process as well as cause a potent yet reversible inhibition of HSG cell growth that is modulated by the presence of TNF-α. © 1994 Wiley-Liss, Inc. 1 This article is a US Government work and, as such, is in the public domain in the United States of America. 相似文献