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91.
F. Musshoff Th. Daldrup W. Bonte A. Leitner O.M. Lesch 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》1996,683(2):163
Human urine samples were examined for the occurrence of formaldehyde-derived tetrahydroisoquinolines and tetrahydro-β-carbolines generated by condensation of the methanol oxidation product with biogenic amines. Positive results were obtained for the tryptamine condensation product 1,2,3,4-tetrahydro-β-carboline and the serotonine condensation product 6-hydroxy-1,2,3,4-tetrahydro-β-carboline as well as for the condensation products with tyramine, dopamine, adrenaline and noradrenaline 1,2,3,4-tetrahydroisoquinoline, 6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline, N-methyl-4,6,7-trihydroxy-1,2,3,4-tetrahydroisoquinoline, 4,6,7-trihydroxy-1,2,3,4-tetrahydroisoquinoline, and the metabolite 6-methoxy-7-hydroxy-1,2,3,4-tetrahydroisoquinoline. Negative results were obtained for N-methyl-1,2,3,4-tetrahydroisoquinoline and 6,7-di-methoxy-1,2,3,4-tetrahydroisoquinoline, N-methyl-1,2,3,4-tetrahydro-β-carboline, 6-methyl-1,2,3,4-tetrahydro-β-carboline, and 6-methoxy-1,2,3,4-tetrahydro-β-carboline in samples of chronic alcoholics as well as in the urine of healthy volunteers. No correlation between alcohol ingestion or state of alcoholization could be demonstrated. 相似文献
92.
利用单克隆抗体免疫磁珠吸附方法分离脐血CD34+细胞,并观察了IL3/GMCSF融合蛋白(PIXY321)对脐血CD34+细胞的刺激作用。PIXY321对脐血CD34+细胞扩增作用大于IL3和GMCSF单独及联合应用。在液体培养条件下,每毫升20ngPIXY321可有效地扩增脐血造血祖细胞,适宜扩增时间为5-8天,扩增后造血祖细胞的数量可达扩增前的8-10倍,从而初步建立了一种简单可行的脐血造血细胞扩增方法。 相似文献
93.
用闪光动力学光谱仪测量了酰化紫膜LB膜中M衰减速率的变化。酰化紫膜LB膜的衰减无论是悬浮液状态,还是LB膜中,均比未修饰的要慢。在温度为20℃时,酰化紫膜LB随着相对湿度的增加,M衰减加快。在相对湿度较低时(RH34—75%),变化较平缓,即M的衰减加快不明显;在相对湿度较高时(RH84—95%),M衰减明显加快。温度的变化则随相对湿度不同而不同。相对湿度较低时,随着温度的升高,M衰减加快;相对湿度较高时,M衰减反而减慢。酰化紫膜悬浮液的M衰减随着温度的升高而明显加快.这说明酰化紫膜LB膜中BR水合程度可能是直接影响M衰减的因素之一。 相似文献
94.
Joachim Messing 《Molecular biotechnology》1996,5(1):39-47
DNA sequence and expression analyses have greatly benefited from using M13 and pUC derived cloning vectors and their polycloning
sites. A chronology of the original concepts and experiments is reviewed. 相似文献
95.
Nishijima K Hisatsune T Kato H Kohyama M Kakehi M Hachimura S Kaminogawa S 《Cytotechnology》1997,25(1-3):89-100
Feeding of a whole casein diet, which abolished the αs1-casein-specific proliferation and IFN-γ productivity of CD4+ T cells, did not affect the proliferative response of CD8+ T cells with regard to the antigen dose response, cell dose response, kinetics of the proliferation and epitope specificity,
as well as IFN-γ production. To assess the characteristics of the CD8+ T cells, we established αs1-casein-specific CD8+ T cell clones from both casein-fed and control mice. The established clones produced different amount of IFN-γ and IL-10,
and one clone derived from the casein-fed mice produced a remarkable amount of IL-10. The clones from casein-fed mice produced
considerable amounts of TGF-β, while those from control mice produced only small amounts. The possible role of CD8+ T cells in oral tolerance is discussed.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
96.
François-Yves Dupradeau Guillaume Le Flem Jean-Michel Wieruszeski Manuel Dauchez Alain Alix Véronique Larreta-Garde Jean-Pierre Monti 《Letters in Peptide Science》1997,4(4-6):489-495
H-NMR studies of the bovine insulin S-sulfonatedB-chain are reported in H2O/D2O (9/1) and inglycerol-d5 (5 M) using two-dimensional NMRspectroscopy. The first results show that the oxidizedinsulin B-chain secondary structure differs from thatof native insulin by a loss of the -helixbetween the two disulfide bridges and that theglycerol favours the structuring of the peptide. 相似文献
97.
The role of context on alpha-helix stabilization: host-guest analysis in a mixed background peptide model. 总被引:1,自引:1,他引:0 下载免费PDF全文
J. Yang E. J. Spek Y. Gong H. Zhou N. R. Kallenbach 《Protein science : a publication of the Protein Society》1997,6(6):1264-1272
The helix content of a series of peptides containing single substitutions of the 20 natural amino acids in a new designed host sequence, succinyl-YSEEEEKAKKAXAEEAEKKKK-NH2, has been determined using CD spectroscopy. This host is related to one previously studied, in which triple amino acid substitutions were introduced into a background of Glu-Lys blocks completely lacking alanine. The resulting free energies show that only Ala and Glu- prove to be helix stabilizing, while all other side chains are neutral or destabilizing. This agrees with results from studies of alanine-rich peptide modela, but not the previous Glu-Lys block oligomers in which Leu and Met also stabilize helix. The helix propensity scale derived from the previous block oligomers correlated well with the frequencies of occurrence of different side chains in helical sequences of proteins, whereas the values from the present series do not. The role of context in determining scales of helix propensity values is discussed, and the ability of algorithms designed to predict helix structure from sequence is compared. 相似文献
98.
Design, synthesis, expression, and characterization of the genes for mouse Fc gamma RIIb1 and Fc gamma RIIb2 cytoplasmic regions. 下载免费PDF全文
L. Chen N. L. Thompson G. J. Pielak 《Protein science : a publication of the Protein Society》1997,6(5):1038-1046
The cytoplasmic regions of the mouse low-affinity Fc gamma RII isoforms, mFc gamma RIIb1, and mFc gamma RIIb2, play a key role in signal transduction by mediating different cellular functions. mFc gamma RIIb1 has a 94-residue cytoplasmic region, whereas mFc gamma RIIb2 has a 47-residue cytoplasmic region. Genes encoding the cytoplasmic regions of mFc gamma RIIb1 (b1-94) and mFc gamma RIIb2 (b2-47) were designed, synthesized, and expressed as fusion proteins in Escherichia coli. A sequence-specific protease, thrombin, was used to release the b1-94 peptide, which was purified by using HPLC. The b2-47 peptide was synthesized chemically. CD spectropolarimetry was employed to examine the secondary structures of b1-94 and b2-47. These studies were conducted in aqueous solution, in mixtures of water and trifluoroethanol or methanol, and as a function of temperature. The results indicate that the b1-94 and b2-47 structures are sensitive functions of the solvent environment, and that nonaqueous solvents induce significant alpha-helical structure. 相似文献
99.
Probing minimal independent folding units in dihydrofolate reductase by molecular dissection. 总被引:7,自引:5,他引:2 下载免费PDF全文
C. V. Gegg K. E. Bowers C. R. Matthews 《Protein science : a publication of the Protein Society》1997,6(9):1885-1892
Molecular dissection was employed to identify minimal independent folding units in dihydrofolate reductase (DHFR) from Escherichia coli. Eight overlapping fragments of DHFR, spanning the entire sequence and ranging in size from 36 to 123 amino acids, were constructed by chemical cleavage. These fragments were designed to examine the effect of tethering multiple elements of secondary structure on folding and to test if the secondary structural domains represent autonomous folding units. CD and fluorescence spectroscopy demonstrated that six fragments containing up to a total of seven alpha-helices or beta-strands and, in three cases, the adenine binding domain (residues 37-86), are largely disordered. A stoichiometric mixture of the two fragments comprising the large discontinuous domain, 1-36 and 87-159, also showed no evidence for folding beyond that observed for the isolated fragments. A fragment containing residues 1-107 appears to have secondary and tertiary structure; however, spontaneous self-association made it impossible to determine if this structure solely reflects the behavior of the monomeric form. In contrast, a monomeric fragment spanning residues 37-159 possesses significant secondary and tertiary structure. The urea-induced unfolding of fragment 37-159 in the presence of 0.5 M ammonium sulfate was found to be a well-defined, two-state process. The observation that fragment 37-159 can adopt a stable native fold with unique, aromatic side-chain packing is quite striking because residues 1-36 form an integral part of the structural core of the full-length protein. 相似文献
100.
CD4+ T-depleted spleen cells (CD8+ T cells) activated by anti-CD3 antibodies (aCD3) suppressed proliferation of CD8+ T-depleted spleen cells (CD4+ T cells) and fresh normal T cells in response to aCD3. Antigen-nonspecific cytolytic activity was induced in splenic CD8+ T cells by stimulation with aCD3 and showed the peak level on day 3, whereas cytolytic activity induced in CD4+ T cells was weak. Intact Ig but not F(ab')2 of aCD3 induced and mediated cytolytic activity. Correspondingly, the cytolytic activity induced by aCD3 was directed against target cells bearing Ig-binding Fc-receptor activity and cytolysis was inhibited by the addition of free Ig into the assay system. We showed that aCD3-activated T cells carried a high level of aCD3 on their surface at the time after the peak proliferation when they attained high cytolytic activity. This raised the possibility that the anti-CD3-induced aCD3-redirected cytolytic activity eliminated Fc-receptor-bearing costimulatory cells in the culture for down-regulation of the T-cell proliferation. This view was supported by partial restoration of anti-CD3-induced low responsiveness of CD8+ T cells by the addition of fresh costimulatory cells. These results suggested a new pathway of down-regulation of T-cell proliferation by aCD3-activated cytolytic CD8+ T cells. 相似文献