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71.
Simon SM Sousa FJ Mohana-Borges R Walker GC 《Proceedings of the National Academy of Sciences of the United States of America》2008,105(4):1152-1157
Products of the umuD gene in Escherichia coli play key roles in coordinating the switch from accurate DNA repair to mutagenic translesion DNA synthesis (TLS) during the SOS response to DNA damage. Homodimeric UmuD(2) is up-regulated 10-fold immediately after damage, after which slow autocleavage removes the N-terminal 24 amino acids of each UmuD. The remaining fragment, UmuD'(2), is required for mutagenic TLS. The small proteins UmuD(2) and UmuD'(2) make a large number of specific protein-protein contacts, including three of the five known E. coli DNA polymerases, parts of the replication machinery, and RecA recombinase. We show that, despite forming stable homodimers, UmuD(2) and UmuD'(2) have circular dichroism (CD) spectra with almost no alpha-helix or beta-sheet signal at physiological concentrations in vitro. High protein concentrations, osmolytic crowding agents, and specific interactions with a partner protein can produce CD spectra that resemble the expected beta-sheet signature. A lack of secondary structure in vitro is characteristic of intrinsically disordered proteins (IDPs), many of which act as regulators. A stable homodimer that lacks significant secondary structure is unusual but not unprecedented. Furthermore, previous single-cysteine cross-linking studies of UmuD(2) and UmuD'(2) show that they have a nonrandom structure at physiologically relevant concentrations in vitro. Our results offer insights into structural characteristics of relatively poorly understood IDPs and provide a model for how the umuD gene products can regulate diverse aspects of the bacterial SOS response. 相似文献
72.
Margarida MC Resende Cleber A Rocha Nely FM Corrêa Renato RG Veiga Sandro JF Passos Neil F Novo Yara Juliano Carlos AV Damasceno 《International wound journal》2016,13(4):526-530
Irrigating wounds with tap water does not increase colonisation, but controlled studies are required for further evidence. Microbial colonisation was assessed in skin wounds, before and after irrigation with tap water, and was compared with irrigation using 0·9% sodium chloride sterile solution. The study included 120 subjects with chronic, traumatic, vascular, pressure or neuropathic wounds. A total of 60 wounds were randomly assigned to be irrigated with tap water (tap water group) and another 60 to be irrigated with 0·9% sodium chloride sterile solution (saline group), at a pressure of 0·46–0·54 PSI. Samples were collected from the centre of each wound using Levine's technique, before and after irrigation, and cultivated in thioglycollate, hypertonic mannitol agar, eosin methylene blue (EMB) agar, blood agar and Sabouraud agar at 37°C for 72 hours. There was concordance (kappa test) and discordance (McNemar test) regarding the count of positive and/or negative samples before and after irrigation in each group. The proportion of reduction of positive samples was similar for both groups in all cultures. Colony‐forming unit count before and after irrigation was similar in both groups and in all cultures, except for the culture in hypertonic mannitol agar from the tap water group, for which the count was lower after irrigation (Wilcoxon z = 2·05, P = 0·041). It is concluded that skin wound irrigation with tap water leads to further reduction of Gram‐positive bacteria compared with 0·9% sodium chloride sterile solution, with no difference in colonisation of haemolytic bacteria, Gram‐negative bacteria and fungi. 相似文献
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Abstract: Until recently, little attention has been directed towards the role the toothbrush may play in human health, even though a report of toothbrush as a significant factor in the infection appeared in 1920. It is common knowledge that the human mouth harbours a wide variety of microorganisms, some of which, at any given time, can be assumed to be potential pathogens. This was not known when toothbrushes were originally designed, yet the common toothbrush has been used in basically the same form for about 200 years. In today's world of organ transplantation and alteration of the immune system, it is important to consider the toothbrush as a source of potential pathogens. Given the fact that very often people will traumatize themselves with their toothbrush, this trauma may become a potential portal of entry for organisms. In this article, we have attempted to demonstrate the importance of toothbrush disinfection, given tips on home toothbrush care and hope to motivate the dentists to educate the patients on the importance of toothbrush disinfection. 相似文献
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77.
Background:
Cancer fear and fatalism are believed to be higher in ethnic minorities and may contribute to lower engagement with cancer prevention and early detection. We explored the levels of cancer fear and fatalism in six ethnic groups in the United Kingdom and examined the contribution of acculturation and general fatalism.Methods:
A cross-sectional survey of 720 White British, Caribbean, African, Indian, Pakistani, and Bangladeshi women (120 of each) was conducted. Three items assessed cancer fear and two cancer fatalism. Acculturation was assessed using (self-reported) migration status, ability to speak English, and understanding of health leaflets; general fatalism with a standard measure.Results:
Relative to White British women, African and Indian women were more fearful of cancer, Bangladeshi women less fearful, and Pakistani and Caribbean women were similar to White British women. Cancer fatalism was higher in all the ethnic minority groups compared with White British women. Less acculturated women were less likely to worry (ORs 0.21–0.45, all P<0.05) or feel particularly afraid (ORs 0.11–0.31, all P<0.05) but more likely to feel uncomfortable about cancer (ORs 1.97–3.03, all P<0.05). Lower acculturation (ORs 4.30–17.27, P<0.05) and general fatalism (OR 2.29, P<0.05) were associated with the belief that cancer is predetermined.Conclusions:
In general, cancer fear and fatalism are more prevalent among ethnic minority than White British women and even more so in less acculturated ethnic minorities. This may affect their participation in cancer prevention and early detection. 相似文献78.
79.
80.
Goud PT; Goud AP; Rybouchkin AV; De Sutter P; Dhont M 《Human reproduction (Oxford, England)》1998,13(5):1336-1345
Obtaining karyotypes from human spermatozoa after microinjection into
Syrian golden hamster oocytes is difficult and the hitherto reported
results are unsatisfactory. This may be related to the injection and
culture technique or to the high susceptibility of the hamster oocytes to
undergo parthenogenetic activation or both. Therefore, we investigated the
hamster oocyte-human sperm microinjection model using the following two
approaches: (i) application of contemporary techniques for injection
(touching the sperm tail) and culture (hamster embryo culture medium,
HECM-3, 10% CO2) and (ii) omission of Ca2+ from the injection medium. Thus,
in the first series of experiments, 252 hamster oocytes were injected with
human spermatozoa. Among the 219 (87%) oocytes that survived the injection
procedure, the mean percentages of male pronucleus formation [two pronuclei
(2PN), two polar bodies (PB)], mitotic metaphase entry and sperm chromosome
spreads were 41.4, 27.8 and 18.2% respectively. Analysis of the oocytes
which failed to develop the male pronucleus following injection revealed
that most of them had developed only the hamster female PN while the sperm
nuclei were either intact or swollen (partially decondensed), indicating
that failure of oocyte activation was not the likely reason for the failure
of male PN formation in these oocytes. In the next series of experiments,
sibling oocytes were alternately injected with spermatozoa suspended either
in the regular (1.9 mM Ca2+) or Ca2+-free injection medium (experiment set
2, n=278). A significant improvement was noted in the mean percentages of
oocytes with 2PN, 2PB, metaphase entry and sperm chromosome spreads in the
Ca2+-free group versus the regular group (2PN, 2PB: 51 versus 36.6%,
metaphase entry: 36.3 versus 26.9% and sperm chromosome spreads: 28 versus
20.4%; all P < 0.04). Thus, parthenogenetic activation appears to be one
of the contributing factors for the failure of male PN formation after
heterospecific hamster ICSI. From these experiments it can be concluded
that application of the advanced injection and culture techniques and
omission of Ca2+ from the injection medium are promising for the routine
application of the hamster oocyte microinjection for karyotyping of human
spermatozoa with poor fertilizing capacity.
相似文献