首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   197篇
  免费   24篇
  221篇
  2024年   1篇
  2023年   2篇
  2022年   1篇
  2021年   5篇
  2020年   2篇
  2019年   3篇
  2018年   8篇
  2016年   4篇
  2015年   2篇
  2014年   6篇
  2013年   11篇
  2012年   16篇
  2011年   12篇
  2010年   7篇
  2009年   6篇
  2008年   7篇
  2007年   6篇
  2006年   6篇
  2005年   8篇
  2004年   11篇
  2003年   11篇
  2002年   13篇
  2001年   7篇
  2000年   5篇
  1999年   4篇
  1998年   2篇
  1996年   2篇
  1995年   3篇
  1994年   1篇
  1992年   7篇
  1991年   7篇
  1990年   6篇
  1989年   1篇
  1988年   3篇
  1987年   3篇
  1986年   1篇
  1984年   5篇
  1983年   1篇
  1978年   1篇
  1977年   1篇
  1976年   1篇
  1975年   1篇
  1974年   1篇
  1973年   1篇
  1971年   2篇
  1970年   2篇
  1969年   3篇
  1961年   2篇
排序方式: 共有221条查询结果,搜索用时 0 毫秒
51.
The effects of laundering with both anionic and nonionic detergents in cold, warm, and hot water on poliovirus-contaminated cotton sheeting, cotton terry cloth, washable wool shirting, wool blanketing, dull nylon jersey, and dacron/cotton shirting were determined. The fabrics were exposed to virus by aerosolization and direct contact (pipette) in separate studies. Although the results varied with each factor used in the study, virus titers on all the fabrics were generally reduced considerably by the laundering process. When the fabrics were dried for 20 hr after laundering, an additional decline in virus titers was seen, often to below detectable levels. The type of detergent used made little difference in effect on virus titer reduction, but the hot wash water markedly reduced the detectable virus. Fabric type was not a major factor in the majority of the experiments, although virus tended to be eliminated more readily from the nylon jersey, and in warm water the virus persisted longer on wool blanketing material laundered in anionic detergent. Sterile fabrics of each type laundered with similar fabrics which contained virus often became contaminated by the virus during the laundering process. Virus titers ranging from undetectable to 10(3.9) cell culture 50% infectious doses/ml were obtained from samples of the rinse water after warm- and cold-water laundering.  相似文献   
52.
A quantitative, reproducible method was developed for the evaluation of the virucidal activity of test gases. Using this method, we determined the virucidal effectiveness of a Steri-Vac ethylene oxide gas sterilizer. Wool gabardine material was exposed to high concentrations of herpes simplex, vaccinia, parainfluenza, or polio viruses and was processed through the sterilizer. Two time-temperature cycles of the machine, 29 C for 180 min and 60 C for 48 min, were used in separate experiments. The viruses were exposed to the gas when freshly pipetted onto the fabric or when pipetted on the material and allowed to dry 16 to 24 hr. In two experiments carried out under each condition, the virus titers were reduced by the sterilization process to less than detectable limits. These titer reductions were for the herpes virus >/= 2.7 to 5.0 log, for vaccinia virus >/= 4.0 to 6.1 log, for parainfluenza virus >/= 1.8 to 4.9 log, and for poliovirus >/= 4.9 to 7.7 log. The observed reductions in virus titers were the same whether the virus-contaminated fabrics were sealed in polyethylene packages or held in open petri dishes during exposure to ethylene oxide.  相似文献   
53.
The persistence of Staphylococcus aureus (Smith) on wool blanket, wool gabardine, cotton sheeting, cotton knit jersey, cotton terry cloth, and cotton wash-and-wear fabrics was studied. The fabrics were exposed to bacterial populations by three methods: direct contact, aerosol, and a lyophilized mixture of bacteria and dust having a high content of textile fibers. The contaminated fabrics were held in 35 or 78% relative humidities at 25 C. In general, the persistence time of S. aureus populations on fabrics held in 35% relative humidity was substantially longer when the fabrics were contaminated by exposure to aerosolized cultures or to dust containing bacteria than when contaminated by direct contact. In a 78% relative humidity, bacterial populations on the fabrics persisted for substantially shorter periods of time regardless of the mode of contamination or fabric type. Cotton wash-and-wear fabric (treated with a modified triazone resin) was the material on which populations of S. aureus persisted for the shortest time. This organism retained its virulence for Swiss mice after being recovered from wool gabardine swatches held 4 weeks in 35% relative humidity and 6 weeks in 78% relative humidity.  相似文献   
54.
Nonneuronal cells mediate neurotrophic action of vasoactive intestinal peptide   总被引:10,自引:0,他引:10  
The developmental regulation of neuronal survival by vasoactive intestinal peptide (VIP) was investigated in dissociated spinal cord-dorsal root ganglion (SC-DRG) cultures. Previous studies demonstrated that VIP increased neuronal survival in SC-DRG cultures when synaptic transmission was blocked with tetrodotoxin (TTX). This effect was further investigated to determine if VIP acted directly on neurons or via nonneuronal cells. For these studies, SC-DRG cells were cultured under conditions designed to provide preparations enriched for a particular cell type: astrocyte-enriched background cell (BG) cultures, meningeal fibroblast cultures, standard mixed neuron-nonneuron (STD) cultures, and neuron-enriched (N) cultures. Addition of 0.1 nM VIP to TTX-treated STD cultures for 5 d prevented the TTX-mediated death and the death that occurred naturally during development in culture, whereas the same treatment on N cultures did not prevent neuronal cell death. Conditioned medium from VIP-stimulated BG cultures prevented neuronal cell death when added to the medium (10% of total volume) of N cultures treated with TTX. The same amount of conditioned medium from BG cultures that were not treated with VIP had no protective action on N cultures. Conditioned medium from N or meningeal fibroblast cultures, either with or without VIP treatment, did not prevent TTX-mediated cell death in N test cultures. These data indicate that VIP increases the availability of neurotrophic survival-promoting substances derived from nonneuronal cultures, the most likely source being astroglial cells. This study suggests that VIP has a role in mediating a neuron-glia-neuron interaction that influences the trophic regulation of neuronal survival.  相似文献   
55.
56.
Summary We have determined the s haplotypes in 709 patients with sickle cell anemia, 30 with SC disease, 91 with S--thalassemia, and in 322 Hb S heterozygotes from different countries. The methodology concerned the detection of mutations in the promoter sequences of the G- and A-globin genes through dot blot analysis of amplified DNA with 32P-labeled probes, and an analysis of isolated Hb F by reversed phase high performance liquid chromatography to detect the presence of the AT chain [A75 (E19) IleThr] that is characteristic for haplotype 17 (Cameroon). The results support previously published data obtained with conventional methodology that indicates that the s gene arose separately in different locations. The present methodology has the advantage of being relatively inexpensive and fast, allowing the collection of a vast body of data in a short period of time. It also offers the opportunity of identifying unusual s haplotypes that may be associated with a milder expression of the disease. The numerous blood samples obtained from many SS patients living in different countries made it possible to compare their hematological data. Such information is included (as average values) for 395 SS patients with haplotype 19/19, for 2 with haplotype 17/17, for 50 with haplotype 20/20, for 2 with haplotype 3/3, and for 37 with haplotype 31/31. Some information on haplotype characteristics of normal A chromosomes is also presented.  相似文献   
57.
Abstract It is already known that maternal overweight, obesity, and morbid obesity are associated with adverse obstetric and neonatal outcomes. To assess the prevalence of overweight and obesity, and the impact of body mass index (BMI) on maternal and neonatal outcomes in Turkey. The study population consisted of 698 singleton pregnancies whose height and weight follow up were performed from the first trimester of pregnancy and whose deliveries were monitored in Trabzon, Turkey in July 2014–June 2015. The data obtained during the study were evaluated using SPSS 21 package program. The differences in variables were assessed by Chi-square-test for categorical data or by One-way Anova test for continuous data. The results were evaluated at a confidence interval of 95% and at a significance level of p?<?0.05. According to the BMI of the women in the study, 68.8% were in normal weight, 20.6% were overweight, 3.9% were obese, and the majority was in the 20–29 age group and 8–15.9?kg. The rate of cesarean, instrumental delivery, induction, episiotomy, late breastfeeding, low apgar (<7 at 5?min), neonatal intensive care unit admission requirement, the newborn at 4000?g or more in overweight (BMI 25–29.9) and obese (BMI?≥?30) pregnancies was higher and the first and second phases of labor were longer (p?<?0.05). The study showed that as the pre-pregnancy body mass index and gestational weight gain increased the rates of cesarean section and interventional delivery increased and the neonatal need for neonatal intensive care unit increased.  相似文献   
58.
Most mutations that delay aging and prolong lifespan in the mouse are related to somatotropic and/or insulin signaling. Calorie restriction (CR) is the only intervention that reliably increases mouse longevity. There is considerable phenotypic overlap between long-lived mutant mice and normal mice on chronic CR. Therefore, we investigated the interactive effects of CR and targeted disruption or knock out of the growth hormone receptor (GHRKO) in mice on longevity and the insulin signaling cascade. Every other day feeding corresponds to a mild (i.e. 15%) CR which increased median lifespan in normal mice but not in GHRKO mice corroborating our previous findings on the effects of moderate (30%) CR on the longevity of these animals. To determine why insulin sensitivity improves in normal but not GHRKO mice in response to 30% CR, we conducted insulin stimulation experiments after one year of CR. In normal mice, CR increased the insulin stimulated activation of the insulin signaling cascade (IR/IRS/PI3K/AKT) in liver and muscle. Livers of GHRKO mice responded to insulin by increased activation of the early steps of insulin signaling, which was dissipated by altered PI3K subunit abundance which putatively inhibited AKT activation. In the muscle of GHRKO mice, there was elevated downstream activation of the insulin signaling cascade (IRS/PI3K/AKT) in the absence of elevated IR activation. Further, we found a major reduction of inhibitory Ser phosphorylation of IRS-1 seen exclusively in GHRKO muscle which may underpin their elevated insulin sensitivity. Chronic CR failed to further modify the alterations in insulin signaling in GHRKO mice as compared to normal mice, likely explaining or contributing to the absence of CR effects on insulin sensitivity and longevity in these long-lived mice.  相似文献   
59.
With the accumulation of a large number and variety of molecules in the Protein Data Bank (PDB) comes the need on occasion to review and improve their representation. The Worldwide PDB (wwPDB) partners have periodically updated various aspects of structural data representation to improve the integrity and consistency of the archive. The remediation effort described here was focused on improving the representation of peptide‐like inhibitor and antibiotic molecules so that they can be easily identified and analyzed. Peptide‐like inhibitors or antibiotics were identified in over 1000 PDB entries, systematically reviewed and represented either as peptides with polymer sequence or as single components. For the majority of the single‐component molecules, their peptide‐like composition was captured in a new representation, called the subcomponent sequence. A novel concept called “group” was developed for representing complex peptide‐like antibiotics and inhibitors that are composed of multiple polymer and nonpolymer components. In addition, a reference dictionary was developed with detailed information about these peptide‐like molecules to aid in their annotation, identification and analysis. Based on the experience gained in this remediation, guidelines, procedures, and tools were developed to annotate new depositions containing peptide‐like inhibitors and antibiotics accurately and consistently. © 2013 Wiley Periodicals, Inc. Biopolymers 101: 659–668, 2014.  相似文献   
60.
Report of the chromosome 5 workshop   总被引:1,自引:0,他引:1  
  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号