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Derek W. Hood Katherine Makepeace Mary E. Deadman Richard F. Rest Pierre Thibault Adele Martin James C. Richards & E. Richard Moxon 《Molecular microbiology》1999,33(4):679-692
A survey of Haemophilus influenzae strains indicated that around one-third of capsular strains and over two-thirds of non-typeable strains included sialic acid in their lipopolysaccharides (LPS). Mutation of the CMP-Neu5Ac synthetase gene (siaB) resulted in a sialylation-deficient phenotype. Isogenic pairs, wild type and siaB mutant of two non-typeable strains were used to demonstrate that sialic acid influences resistance to the killing effect of normal human serum but has little effect on attachment to, or invasion of, cultured human epithelial cells or neutrophils. We determine for the first time the site of attachment of sialic acid in the LPS of a non-typeable strain and report that a small proportion of glycoforms include two sialic acid residues in a disaccharide unit. 相似文献
105.
Ana Maria Brito Carl Kendall Ligia Kerr Rosa Maria Salani Mota Mark Drew Crosland Guimar?es Inês Dourado Adriana A. Pinho Adele Schwartz Benzaken Sandra Brignol Arthur L. Reingold 《PloS one》2015,10(6)
The aim of this study was to assess risk factors associated with low levels of HIV testing among MSM recruited through respondent driven sampling (RDS) in Brazil. Of 3,617 participants, 48.4% had never tested previously for HIV. A logistic model indicated that younger age, lower socioeconomic class, education, poor HIV/AIDS knowledge, no history of cruising, and having been tested during the study were characteristics independently associated with low levels of previous HIV testing. The HIV testing rate among MSM in Brazil is still low in spite of the availability of a large number services providing universal and free access to HIV/AIDS diagnosis and treatment. To respond to low utilization, the authors propose a higher priority for testing for key populations such as MSM, expanded education, expanding testing sites and a welcoming and nonjudgmental environment in health services. 相似文献
106.
Flash-induced absorbance measurements at 830 nm on both nanosecond and microsecond timescales have been used to characterise the effect of ultraviolet light on Photosystem II core particles. A combination of UV-A and UV-B, closely simulating the spectrum of sunlight below 350 nm, was found to have a primary effect on the donor side of P680. Repetitive measurements indicated reductions in the nanosecond components of the absorbance decay with a concomitant appearance and increase in the amplitude of a component with a 10 s time constant attributed to slow reduction of P680+ by Tyrz when the function of the oxygen evolving complex is inhibited. Single-flash measurements show that the nanosecond components have amplitudes which vary with S-state. Increasing UV irradiation inhibited the amplitude of these components without changing their S-state dependence. In addition, UV irradiation resulted in a reduction in the total amplitude, with no change in the proportion of the 10 s contribution.Abbreviations BBY-
PS II membrane fragments
- P680-
primary electron donor of PS II
- PS II-
Photosystem II
- QA and QB–
primary and secondary quinone electron acceptors of PS II
- S-state-
redox state of the oxygenevolving complex
- Tyrz–
tyrosine residue in PS II
- UV-A-
ultraviolet radiation 320–400 nm
- UV-B-
ultraviolet radiation 280–320 nm 相似文献
107.
The kinetics of P680+ reduction in oxygen-evolving spinach Photosystem II (PS II) core particles were studied using both repetitive and single-flash 830 nm transient absorption. From measurements on samples in which PS II turnover is blocked, we estimate radical-pair lifetimes of 2 ns and 19 ns. Nanosecond single-flash measurements indicate decay times of 7 ns, 40 ns and 95 ns. Both the longer 40 ns and 95 ns components relate to the normal S-state controlled Yz P680+ electron transfer dynamics. Our analysis indicates the existence of a 7 ns component which provides evidence for an additional process associated with modified interactions involving the water-splitting catalytic site. Corresponding microsecond measurements show decay times of 4 s and 90 s with the possibility of a small component with a decay time of 20–40 s. The precise origin of the 4 s component remains uncertain but appears to be associated with the water-splitting center or its binding site while the 90 s component is assigned to P680+-QA
– recombination. An amplitude and kinetic analysis of the flash dependence data gives results that are consistent with the current model of the oxygen-evolving complex.Abbreviations PS II-
Photosystem II-
- P680-
primary donor (Chl-aII dimer) of PS II
- Yz-
Tyr 161 donor to P680
- QA-
quinone secondary acceptor to P680
- LHC-
light-harvesting chlorophyll protein of PS II
- BBY-
Berthold, Babcock and Yocum PS II membrane fragment preparation
- PPBQ-
phenyl-p-benzoquinone 相似文献
108.
Maria Adele Imro Corrado Castagneto Ornella Bosco Paola Modena Lorella Lanza Francesco Puppo Gilberto Filaci Francesco Indiveri Marco Scudeletti 《Cancer immunology, immunotherapy : CII》1995,41(4):210-216
In the present study T lymphocytes isolated from a metastatic lymph node (T-LNL) of a melanoma patient have been cloned. In the attempt to verify whether T-LNL may acquire in vitro functional activities in the absence of tumour-associated antigens, they were cloned utilizing allogeneic lymphocytes as feeder cells. Nineteen clones generated from T-LNL proved to be CD4+ and, among these, five were able to kill autologous and allogeneic human melanoma cells in HLA-class-II-restricted way. On the basis of their cytokine production, these CD4+ cytolytic T-LNL clones were shown to belong to the Th0 subset and three of them expersseed the V17 chain of the T cell receptor. These results suggest the presence of melanomaspecific but functionally inactive lymphocytes with T cell receptor oligoclonality in the lymph node environment. These specific T cells may acquire in vitro the capacity to kill autologous and allogeneic tumours without any induction by autologous melanoma cells. 相似文献
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110.
Prior to the discovery of a minimal ATP‐dependent DNA ligase in Haemophilus influenzae, bacteria were thought to only possess a NAD‐dependent ligase, which was involved in sealing of Okazaki fragments. We now know that a diverse range of bacterial species possess up to six of these accessory bacterial ATP‐dependent DNA ligases (b‐ADLs), which vary in size and enzymatic domain associations. Here we compare the domain structure of different types of b‐ADLs and investigate their distribution among the bacterial domain to describe possible evolutionary trajectories that gave rise to the sequence and structural diversity of these enzymes. Previous biochemical and genetic analyses have delineated three main classes of these enzymes: Lig B, Lig C and Lig D, which appear to have descended from a common ancestor within the bacterial domain. In the present study, we delineate a fourth group of b‐ADLs, Lig E, which possesses a number of unique features at the primary and tertiary structural levels. The biochemical characteristics, domain structure and inferred extracellular location sets this group apart from the other b‐ADLs. The results presented here indicate that the Lig E type ligases were horizontally transferred into bacteria in a separate event from other b‐ADLs possibly from a bacteriophage. 相似文献