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21.
Summary A cDNA clone in pBR322 that cross-hybridizes with a mouse carbonic anhydrase form II (CAII) probe has been sequenced and identified as mouse carbonic anhydrase form I (CAI). The 1224-base-pair clone encodes the entire 260-amino-acid protein and appears to contain an Alu-like element in the 3 untranslated region. The deduced amino acid sequence exhibits 77% homology to human CAI and contains 17 of the 20 residues that are considered unique to and invariant for all mammalian CAI isozymes. The results of a detailed comparison of the nucleic acid sequences spanning the coding regions of mouse CAI and rabbit CAI have been used to calibrate an evolutionary clock for the carbonic anhydrases (CAs). These data have been applied to a comparison of the mouse CAI and CAII nucleic acid sequences to calculate the divergence time between the two genes. The divergence-time calculation provides the first estimation of the evolutionary relationship between CAs based entirely on nucleotide sequence comparison. 相似文献
22.
Swantje Vellguth Priv.-Doz. Dr. Brita von Gaudecker Hans-Konrad Müller-Hermelink 《Cell and tissue research》1985,242(3):579-592
Summary Splenic tissue of human fetuses from the 14th to the 24th week of gestation (menstrual age) were investigated by light- and electron microscopy to describe the development of the red and white pulp in close relationship to the differentiation of the vascular tree. Special interest is focussed on the differentiation of the T-cell- and the B-cell regions and their specific stationary cells.The preliminary stage, here called the primary vascular reticulum, lasts up to the 14th gestational week (gw). Numerous erythrocytes, normoblasts and macrophages are seen among a network of mesenchymal cells and argyrophilic fibers. Hematopoiesis, especially erythropoiesis, can be recognized.The characteristic organ structure becomes established during the subsequent transformation stage of the fetal spleen, beginning with the 15th gw. Splenic lobules begin to form during the 15th to 17th gw. They consist of a central artery, surrounded by a sheath of lightly stained stationary cells which resemble myofibroblasts. At the periphery of these lobules the red pulp forms. Initially mobile cells are distributed throughout the reticulum. Soon they begin to accumulate in the venous sinuses, which develop from lacunae among the reticular network and come into contact with the venous system. The endothelial wall of these sinuses remains discontinuous, confirming the theory of the open vascularization of the spleen. The development of the larger veins is correlated with the differentiation of the splenic trabeculae.The development of the white pulp is correlated with the stage of lymphoid colonization within the spleen, beginning around the 18th gw. An accumulation of lymphocytes around the central arteries can be recognized during the 19th and 20th gw. These lymphoid cells show morphological and immunohistochemical characteristics of T-precursor cells. Within the now assembling periarterial lymphoid sheath (PALS) a few precursors of interdigitating cells (IDC) are recognizable, giving evidence for the differentiation of the T-cell region.Around the 23rd gw the assemblage of primary follicles is discernible at the periphery of the PALS. Precursors of the follicular dendritic reticulum cell (FDRC), the specific stationary cell of the B-cell region, have been recognized. This observation leads to the conclusion that the small primary follicles represent the beginning formation of the B-cell region.The significance of the vascular system for the differentiation of the specific splenic organization is discussed.This investigation was supported by grants from the Deutsche Forschungsgemeinschaft (Sonderforschungsbereich 111)The authors appreciate the contribution of human fetal material from Dr. von Hollweg and Dr. Körner from the Hospital Heidberg, Hamburg, and the excellent technical assistance of Mrs. H. Hansen, Mrs. I. Knauer, Mrs. M.v. Kolszynski, Mrs. J. Quitzau, Mrs. H. Siebke and Mrs. H. Waluk 相似文献
23.
The araBAD operon of Salmonella typhimurium LT2. I. Nucleotide sequence of araB and primary structure of its product, ribulokinase 总被引:6,自引:0,他引:6
Hybrid plasmids containing the araBAD operon of Salmonella typhimurium LT2 were characterized by Southern blot and genetic analyses. The nucleotide sequence of araB was determined. The araB gene product, ribulokinase (EC 2.7.1.16), was purified and the results of amino acid composition analysis and partial amino acid sequence are in agreement with predictions from the DNA sequence. Ribulokinase is 569 amino acid residues long and has a calculated Mr of 61 793. Ribulokinase shares significant homology with xylulose kinase from Escherichia coli. Codon usage in the araB gene does not favor those codons which have intermediate codon-anticodon binding energy. 相似文献
24.
Abstract 3 new shuttle cloning vectors for gene transfer into Escherichia coli and Anacystis nidulans have been constructed by utilizing the cyanobacterial origin of replication of the small plasmid pANS from A. nidulans . 2 of these new vectors, pXB7 (pDPL13 derivative) and pECAN8 (pUC8 derivative), convey ampicillin resistance, and transform A. nidulans with relatively high frequencies. Vector pXB7 has 10 unique cloning sites; pECAN8 contains 4 cloning sites within the lacZ gene permitting rapid detection of DNA inserts in the presence of Xgal. The third vector, pKBX, has a lower transformation frequency but adds kanamycin resistance as a selectable gene for shuttle vectors of cyanobacteria. 相似文献
25.
Abstract Listeriolysin, an SH-activated haemolysin probably involved in Listeria pathogenicity, has been cloned into the cosmid vector pHC79 and was expressed in Escherichia coli HB101 cells. Chromosomal DNA of Listeria monocytogenes serovar 1/2 was partially digested with Mbo I and ligated to the Bam HI cleaved cosmid. From 2000 recombinant clones examined, 12 (0.6%) produced haemolysin in solid and liquid media. All of them contained chromosome fragments of Listeria of about 40 kb. The cloning of the listeriolysin determinant will lead to a better understanding of the basis of Listeria pathogenicity. 相似文献
26.
Robert T. Przygoda K. Takayama Karl A. Traul A. Tummey 《In vitro cellular & developmental biology. Plant》1985,21(1):32-38
Summary An atmosphere containing 10% CO2 has been generally accepted as optimal for the growth of Syrian hamster embryo cells in a clonal transformation assay. Data
presented in this paper show that 10% CO2 may not be the optimum environment for this assay.
Using 10 or 20% (analytically measured) CO2 in air (1 atm pressure), hamster embryo cell pools were examined for clonal growth characteristics and transformability using
five known carcinogens and a single noncarcinogenic compound. At 10% CO2, only 2 of 11 pools weee transformed by the five carcinogens but not by the noncarcinogen. At 20% CO2, six of seven pools were transformed by the five carcinogens and not by the noncarcinogen. Further, the transformation frequencies
were found to be greater in cultures incubated in an atmosphere consisting of 20% CO2 in air. The data also show that 20% CO2 increased the cloning efficiency of these cells.
A comparison of the 10 and 20% CO2 data to results reported from other conflicting interlaboratory results with this assay system may be due, in part, to variations
of CO2 concentrations. In some instances, the CO2 levels indicated by incubator flow meters vary considerably from analytically determined CO2 values. To prevent these CO2 discrepancies and their resultant effects on transformation and cloning efficiency, methods for monitoring the CO2 environment other than flow meters are recommended.
The observation of increased cloning efficiencies and transformation rates strongly suggests that culture incubation at 20%
CO2 is a preferred environment for the conduct of this assay. 相似文献
27.
Improved clonal and nonclonal growth of human,rat and bovine adrenocortical cells in culture 总被引:2,自引:0,他引:2
Jan M. McAllister Peter J. Hornsby 《In vitro cellular & developmental biology. Plant》1987,23(10):677-685
Summary This report describes the development of a culture system for long-term growth and cloning of human fetal adrenocortical cells.
Optimal conditions for stimulating clonal growth were determned by testing the efficacy of horse serum (HS), fetal bovine
serum (FBS), fibroblast growth factor (FGF), epidermal growth factor (EGF), fibronectin, and a combination of growth factors,
UltroSer G, in stimulating growth from low density. Optimal conditions for clonal growth were achieved using fibronectin-coated
dishes and DME/F12 medium with 10% FEBS, 10% HS, 2% UltroSer G, and 100 ng/ml FGF or 100 pM EGF. Conditions for growth at clonal density were found to be optimal for growth of early passage, nonclonal cultures at
higher densities. The improved growth conditions used for cloning were shown to allow continued long-term growth of nonclonal
human adrenocortical cells without fibroblasts overgrowth. All cells in cultures grown in HS, FBS, and UltroSer G had morphologic
characteristics of adrenocortical cells, whereas cells grown in FBS only rapidly became overgrown with fibroblasts. Clonal
and nonclonal early passage human adrenocortical cells had smilar mitogenic responses to FGF and EGF. Whereas FGF, EGF, and
UltroSer G showed similar stimulation of DNA synthesis and clonal growth in human adrenocortical cells and human adrenal gland
fibroblasts, the tumor promoter 12-O-teradecanoylphorbol-13-acetate stimulated growth only in adrenocortical cells and was strongly inhibitory to growth in fibroblasts.
In both cell types, forskolin inhibited DNA synthesis. Human adrenocortical cell cultures were functional and synthesized
cortisol, dehydroepiandrosterone, and dehydroepiandrosterone sulfate. The improved growth conditions for clonal growth of
human adrenocortial cells also provided optimal conditions for long-term growth of cultured rat adrenocortical cells and ncreased
the cloning efficiency of cultured bovine adrenocortical cells.
This work was supported by Research grants AG-00936 and AG-06108 from the National Institute on Aging, Bethesda, MD. 相似文献
28.
Summary Earlier studies found that cotton (Gossypium hirsutum L.) cotyledons contain several mRNAs which are more abundant during late embryogenesis than in mid-embryogenesis or early germination. They are here termed Late embryogenesis-abundant mRNAs, encoded by Lea loci. Complementary DNA clones for 18 such mRNA sequences, defined at a hybridization criterion of Tm-15°C, were identified in a mature embryo cDNA library by differential cDNA hybridization. At a lower hybridization criterion, some sequence homology was found within several of these cloned Lea mRNA sequences. Each Lea mRNA sequence comprises 0.04–1.3% of mature embryo poly(A)+ mRNA, a level ten-fold to several hundred-fold higher than in young embryo or 24 h seedling poly(A)+ mRNA. Of 18 Lea mRNA sequences examined in cultured young embryos, the level of at least 13 are specifically increased by exogenous abscisic acid (ABA), several to a level near that in normal mature embryos. However, the abundance of several of the sequences does not appear to be significantly modulated by ABA. The LEA polypeptides encoded by 10 Lea mRNA sequences were identified by hybrid-arrested translation. They include most of the late embryogenesis-abundant, ABA-inducible, polypeptides previously identified. Preliminary results suggest that many of the individual Lea mRNA sequences are transcribed from 1–3 genes in each of cotton's two subgenomes. 相似文献
29.
Dilip M. Shah Cathy M. Hironaka Roger C. Wiegand Elizabeth I. Harding Gwen G. Krivi David C. Tiemeier 《Plant molecular biology》1986,6(4):203-211
Summary We have used the cDNA clone encoding maize glutathione-S-transferase (GST I) to isolate a genomic DNA clone containing the complete GST I gene. Nucleotide sequence analysis of the cDNA and genomic clones has yielded a complete amino acid sequence for maize GST I and provided the exon-intron map of its gene. The mRNA homologous sequences in the maize GST I gene consist of a 107 bp 5 untranslated region, a 642 bp coding region and 340 bp of the 3 untranslated region. They are divided into three exons by two introns which interrupt the coding region. The 5 untranslated spacer contains an unusual sequence of pentamer AGAGG repeated seven times. The inbred maize line (Missouri 17) contains a single gene for GST I, whereas the hybrid line (3780A) contains two genes. Nucleotide sequence analysis of the primer extended cDNA products reveals that the 5 untranslated regions of the two genes in the hybrid 3780A are identical except for a 6 bp internal deletion (or insertion). The amino acid sequence of maize GST I shares no apparent sequence homology with the published sequences of animal GST's and represents the first published sequence of a plant GST. re]19850813 ac]19851126 相似文献
30.
Robert A. MacLeod 《FEMS microbiology letters》1986,39(1-2):109-113
Abstract Many species of bacteria isolated from saline environments require Na+ specifically for membrane transport. Transport occurs by a Na+ symport process energized by an electrochemical gradient of Na+ ions. The gradient at neutral pH appears to be produced by a primary electrogenic extrusion of protons coupled to a secondary, outwardly directed Na+ pump, a Na+ /proton antiporter. At alkaline pH Vibrio alginolyticus may also produce the gradient by an energy-dependent primary extrusion of Na+ ions. Alteromonas haloplanktis and Vibrio costicola require salts in the medium to retain intracellular solutes. For A. haloplanktis the effects of the salts are primarily osmotic. For V. costicola , only NaCl is effective in retaining solutes and Na+ is required by this organism to maintain the membrane potential. In Escherichia coli a single substitution in the nucleotide sequence of the gene coding for the melibiose transport protein changed the cation specificity of the transport system. The possible ecological significance of this finding has been considered. 相似文献