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871.
Immunosuppressive properties of leukotriene D4 and E4 in vitro 总被引:4,自引:0,他引:4
D R Webb I Nowowiejski C Healy T J Rogers 《Biochemical and biophysical research communications》1982,104(4):1617-1622
Leukotrienes D4 and E4 whose physiological function has been associated with smooth muscle contraction, are demonstrated to be potent suppressors of immunocompetent cell function. In concentrations as low as 10?12 M both leukotriene D4 and E4 can inhibit mitogen-induced lymphocyte transformation. Higher concentrations of leukotrienes E4 and D4 will inhibit appearance of antibody-forming cells in tissue culture. These data suggest another role for the leukotrienes in addition to their function as slow-reacting substances. 相似文献
872.
Binding, internalization and intracellular processing of 125I-epidermal growth factor purified by isoelectric focusing 总被引:1,自引:0,他引:1
B E Magun S R Planck L M Matrisian J S Finch 《Biochemical and biophysical research communications》1982,108(1):299-306
When epidermal growth factor (EGF) which had been extensively purified by HPLC was subjected to iodination with sodium 125iodide, 5 major species of differing isoelectric points were produced. Some of these species bound to rat fibroblasts with different affinities but were internalized with equal efficiency. Examination of the internalized 125I-labelled molecules revealed processing of all the 125I-EGF species to macromolecules with more acidic isoelectric points. The 125I-EGF species with a pI of 4.5 corresponded in electrofocusing behavior with intact non-iodinated EGF. Other EGF species probably represented molecules which were covalently modified as a result of the iodination procedure. 相似文献
873.
Jayalakshmi Kumpati 《Biochemical and biophysical research communications》1982,105(2):482-487
To investigate the role of phenylalanine and tryptophane as potential antisickling agents in intact human SS-red blood cells a liposomal transport system was employed to transfer phenyl-alanine or tryptophane into intact SS-red blood cells. Aromatic amino acids and short peptides containing phenylalanine have been demonstrated to increase the minimum gelling concentration and solubility of deoxy-hemoglobin S in aqueous solution. However, these compounds do not cross the red blood cell membrane under usual incubation conditions. Incorporation of phenylalanine or tryptophane into intact SS-red blood cells liposomal transport system markedly inhibited the sickling of deoxy-hemoglobin S. These findings raise the possibility that a nontoxic liposomal transport system which facilitates incorporation of antisickling agents into intact SS-RBC may have significant therapeutic implications in the treatment of sickle cell disease. 相似文献
874.
Gary L. Bradshaw George R. Dubes 《In vitro cellular & developmental biology. Plant》1983,19(10):735-742
Summary Factors requred as supplements to basal tissue culture medium for the multiplication of cells of the cloned rat fibroblast
line called normal rat kidney 49F (NRK-49F) were identified as epidermal growth factor, fibronectin, insulin, and retinoic
acid. The requirement for fibronectin was manifested on a clean glass surface but not on the polystyrene plastic surface tested.
This set of required factors differs substantially from the factor sets required by the Madin-Darby, canine kidney (MDCK)
and LLC-PK1 pig kidney lines of epithelial cells and the baby hamster kidney 21 (BHK-21) line of fibroblasts. The serum-free medium supplemented
with the four factors supported rapid growth of NRK-49F cells when the initial cell population density was about 8,000 cells/cm2 or greater. At lower initial densities, cell multiplication was markedly increased by adding serum-free medium that had been
conditioned by NRK-49F cells. Cell growth rate in the defined serum-free medium stayed high through two serial passages but
declined in the third serial passage unless the cell-conditioned medium was added. 相似文献
875.
The DNA-dependent RNA polymerases of Schneider 2-L cells of Drosophila melanogaster are described. These cells contain five readily detectable forms of this enzyme, polymerases Ia, Ib, IIIa, II, and IIIb, which elute from DEAE-Sephadex at 0.08, 0.12, 0.15, 0.20, and 0.22 m ammonium sulfate, respectively. RNA polymerases IIIa and IIIb, which each constitute about 5–10% of the total RNA polymerase activity in Drosophila embryos, are found to constitute 30 and 10%, respectively, of the total polymerase activity in cultured cells. The two form III polymerases are further characterized by in vitro response to divalent cations and ionic strength, template utilization, and sensitivity to -amanitin. Verification of the class III designation of these two polymerases is provided by their sensitivity to only very high levels of -amanitin (50% inhibition at approximately 800 µg/ml), their 10-fold greater activity on poly[d(A–T)], and their elution from DEAE-cellulose at lower ionic strengths than from DEAE-Sephadex.This work was supported by the Natural Sciences and Engineering Research Council. 相似文献
876.
本文研究TSH和forskolin对原代培养的猪甲状腺细胞[Ca~(2+)]_i和钙调蛋白的影响。结果表明,TSH可引起甲状腺细胞[Ca~(2+)]_1急性升高。此反应是剂量依赖关系,而与细胞外钙的存在与否无关。其反应性在细胞单层高于细胞是液,近汇合细胞单层高于汇合细胞单层。TSH作用3天,可使甲状腺细胞的钙调蛋白含量增高,此作用与TSH对甲状腺细胞数的影响无关。Forskolin对甲状腺细胞的[Ca~(2+)]_i和钙调蛋白均无明显的影响。 相似文献
877.
Q Y Liu L F Wang S Y Miao M Zhao S D Zong Y C Yan S S Koide 《Molecular reproduction and development》1992,31(1):9-13
A general mammalian expression vector designated pSV2-EP was reconstructed by inserting an oligonucleotide fragment into pSV2-dhfr. This vector allowed insertion of cDNAs with EcoRI cohesive ends. The pSV2-EP contains a simian virus 40 (SV40) early promoter, origin for DNA replication, SV40 poly-A site, splicing site, an initiator ATG downstream from the promoter and an EcoRI site for the insertion of cDNA fragment screened from lambda gt11 expression libraries. A recombinant plasmid (pS-VRS-1) was constructed by inserting RSD-1, a cDNA encoding a rabbit sperm tail protein, into the EcoRI site of the pSV2-EP vector. Chinese hamster ovarian (CHO) dhfr-negative cells were cotransformed with pSV2-dhfr and pSVRS-1 by the calcium phosphate method. In selective culture medium without thymidine and hypoxanthine, several cell lines were obtained containing mRNA and DNA that hybridized with RSD-1. One of these transformed cell lines stained intensely with anti-rSMP-B antibodies, demonstrating that the RSD-1 was expressed in the transformed CHO cells. 相似文献
878.
用三步纯化法从人M_3型白血病细胞中分离纯化出人类肿瘤癌性促凝物(CP)。促凝活性回收率为24%,CP纯化倍数为2481倍。纯化CP在SDS-PAGE上为单一区带,其理化和酶学特性类似于动物肿瘤CP,分子量约为70 000,PI为4.8,在FVⅡ缺乏血浆中以及在含有组织因子(TF)抑制剂情况下仍能激活FX。CP促凝活性能被半胱氨酸蛋白酶抑制剂HgCl_2抑制,纯化CP能与抗动物肿瘤CP抗体形成免疫沉淀反应。 相似文献
879.
Y Fukui K Sawai M Furudate N Sato Y Iwazumi K Ohsaki 《Molecular reproduction and development》1992,33(3):357-362
The present study was conducted to investigate the effects of different culture durations (24-36 hr) on bovine oocyte maturation in vitro and the effect of the presence or absence of cumulus cells at the time of treatment to induce parthenogenetic activation (exposure to ethanol and cytochalasin B; CB) (experiment I). The effects of dosage (2.5 or 5.0 micrograms/ml) and incubation time (2.5, 5, or 10 hr) in CB (experiment II) on the subsequent development to the blastocyst stage in vitro was also investigated. In experiment I, cleavage and development to the blastocyst stage were not affected by the presence or absence of cumulus cells at the time of parthenogenetic activation. However, the 24-hr culture duration for in vitro maturation had a significantly lower rate of development to the blastocyst stage than the longer culture durations (27-36 hr). In experiment II, treatment with 5 micrograms/ml CB for 5 hr showed the highest percentage of development to blastocyst in the oocytes matured for both 27 and 30 hr. To determine the viability of the parthenogenetic embryos (morulae and blastocysts), four recipient heifers received two embryos each, and one heifer was found to be pregnant on day 35 following transfer. Although fetal heartbeat was not observed, the subsequent estrus was prolonged in all heifers. The present results demonstrate development of in vitro-matured, parthenogenetically activated bovine embryos up to the preimplantation stage. 相似文献
880.