全文获取类型
收费全文 | 272篇 |
免费 | 25篇 |
专业分类
297篇 |
出版年
2023年 | 1篇 |
2021年 | 3篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2018年 | 6篇 |
2015年 | 6篇 |
2014年 | 4篇 |
2013年 | 10篇 |
2012年 | 9篇 |
2011年 | 17篇 |
2010年 | 7篇 |
2009年 | 10篇 |
2008年 | 14篇 |
2007年 | 8篇 |
2006年 | 12篇 |
2005年 | 17篇 |
2004年 | 22篇 |
2003年 | 11篇 |
2002年 | 16篇 |
2001年 | 7篇 |
2000年 | 3篇 |
1999年 | 3篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 7篇 |
1995年 | 6篇 |
1994年 | 3篇 |
1993年 | 9篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 9篇 |
1981年 | 2篇 |
1980年 | 6篇 |
1979年 | 2篇 |
1977年 | 5篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 5篇 |
1969年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有297条查询结果,搜索用时 14 毫秒
181.
OBJECTIVE--To quantify the effectiveness of home visiting programmes in the prevention of child injury and child abuse. DESIGN--Systematic review of 11 randomised controlled trials of home visiting programmes. Pooled odds ratios were estimated as an inverse variance weighted average of the study specific odds ratios. SETTING--Randomised trials that were available by April 1995. SUBJECTS--The trials comprised 3433 participants. RESULTS--Eight trials examined the effectiveness of home visiting in the prevention of childhood injury. The pooled odds ratio for the eight trials was 0.74 (95% confidence interval 0.60 to 0.92). Four studies examined the effect of home visiting on injury in the first year of life. The pooled odds ratio was 0.98 (0.62 to 1.53). Nine trials examined the effect of home visiting on the occurrence of suspected abuse, reported abuse, or out of home placement for child abuse. Because of the potential for bias in outcome reporting in these studies, pooled effect estimates were not calculated. CONCLUSIONS--Home visiting programmes have the potential to reduce significantly the rates of childhood injury. The problem of differential surveillance for child abuse between intervention and control groups precludes the use of reported abuse as a valid outcome measure in controlled trials of home visiting. 相似文献
182.
Teresa A. Simon Adam Thompson Kunal K. Gandhi Marc C. Hochberg Samy Suissa 《Arthritis research & therapy》2015,17(1)
IntroductionPatients with rheumatoid arthritis (RA) are at an increased risk of malignancies compared with the general population. This has raised concerns regarding these patients, particularly with the widespread use of immunomodulating therapies, including biologic disease-modifying antirheumatic drugs (DMARDs). We performed a systematic literature review and analysis to quantify the incidence of malignancies in patients with RA and the general population to update previously published data.MethodsA literature search was conducted that was consistent with and similar to that in a meta-analysis published in 2008. MEDLINE, BIOSIS Previews, Embase, Derwent Drug File and SciSearch databases were searched using specified search terms. Predefined inclusion criteria identified the relevant observational studies published between 2008 and 2014 that provided estimates of relative risk of malignancy in patients with RA compared with the general population. Risk data on overall malignancy and site-specific malignancies (lymphoma, melanoma and lung, colorectal, breast, cervical and prostate cancer) were extracted. The standardized incidence ratios (SIRs; a measure of risk) relative to the general population were evaluated and compared with published rates.ResultsA total of nine publications met the inclusion criteria. Seven of these reported SIRs for overall malignancy; eight for lymphoma, melanoma, and lung, colorectal and breast cancer; seven for prostate cancer; and four for cervical cancer. Compared with those in the general population, the SIR estimates for patients with RA suggest a modest increased risk in overall malignancy, as previously observed. Patients with RA continued to show an increased risk of lymphoma and lung cancer compared with the general population. Overall, SIR estimates for colorectal and breast cancers continued to show a decrease in risk, whereas cervical cancer, prostate cancer and melanoma appeared to show no consistent trend in risk among patients with RA compared with the general population.ConclusionsThe additional data evaluated here are consistent with previously reported data. Patients with RA are at an increased risk of lung and lymphoma malignancies compared with the general population. Quantifying differences in malignancy rates between non-biologic and biologic DMARD-treated patients with RA may further highlight which malignancies may be related to treatment rather than to the underlying disease. 相似文献
183.
Complex PTSD and its correlates amongst female Yazidi victims of sexual slavery living in post‐ISIS camps 下载免费PDF全文
184.
185.
E. Bogomolny Shaul Mordechai A. Zwielly M. Huleihel 《European biophysics journal : EBJ》2009,38(7):971-980
Light-induced fluorescence (LIF) spectroscopy has demonstrated ability as a novel, noninvasive and sensitive technology for
early detection of cancer. The goal of the present study is to examine the potential of this spectroscopic method for early
detection and characterization of premalignant changes. As a model we used both cell lines and primary cells, which were transformed
to malignant by retrovirus. Fluorescence measurements and morphological observations of the infected cells were performed
at various postinfection times. Our results showed gradual attenuation of fluorescence intensities due to cancer progression
which corresponds to aromatic amino acids and nicotinamide adenine dinucleotide (NADH) molecules. In order to obtain grading
and supervised classifications of the spectral premalignant changes we used approaches of linear discriminant analysis. The
classifications based on Mahalanobis distances allowed us to demonstrate that the accuracy of identification of premalignant
stages varied between 83.1% and 96.4%. In summary, we conclude that LIF in tandem with proper statistical tools may be a promising
technique for early detection of malignant progression. 相似文献
186.
Amphicarpy is a form of diversified bet-hedging expressed mostly in annual plants, where two types of offspring are produced
with two distinct ecological roles: long-range aerial dispersers and highly competitive subterranean, sedentary fruit. Emex spinosa is a semi-arid, amphicarpic annual, inhabiting habitats with different levels of environmental variation. We tested the hypothesis
that, in E. spinosa, bet-hedging may be “fine-tuned” by plasticity in the phenotype ratio (aerial/subterranean fruit mass) as a function of environmental
conditions. We conducted a greenhouse experiment, manipulating nutrient availability and intraspecific density, to determine
the pattern of ratio shifts. In order to determine whether the integrated strategy is an adaptation to variable habitats,
a similar common garden experiment was conducted, comparing two natural populations differing in environmental variability.
The offspring ratio shifted in response to both nutrient availability and plant density. In pots containing single plants
the ratio increased steeply with nutrient availability, while in pots containing eight plants a more moderate increase occurred.
These shifts were the result of plasticity in allocation to both achene types, as well as ontogenetic effects on aerial achene
production. The degree of response increased with the heterogeneity of the habitat of origin. We found evidence for an adaptive
integrated strategy, with bet-hedging “fine-tuned” by phenotypic plasticity. Strenuous conditions tended to shift the offspring
ratio towards securing subterranean reproductive success, while favorable conditions resulted in a shift towards dispersible
achenes.
The authors Asaf Sadeh and Hagai Guterman contributed equally to this study. 相似文献
187.
Eukaryotic Translation Initiation Factor 4E-Dependent Translation Is Not Essential for Survival of Starved Yeast Cells 下载免费PDF全文
The eukaryotic translation initiation factor 4E (eIF4E) interacts with the mRNA 5' cap structure (m(7)GpppX) and is essential for the appropriate translation of the vast majority of eukaryotic mRNAs. Most studies of the yeast Saccharomyces cerevisiae CDC33 gene product, eIF4E, have been carried out with logarithmically growing cells, and little is known about its role in starved, nonproliferating cells that enter the stationary phase (SP). It has previously been found that the rate of translation in SP cells is more than 2 orders of magnitude lower than it is in dividing yeast cells. Here we show that this low rate of translation is essential for maintaining the viability of starved yeast cells that enter SP. Specifically, starved cells whose eIF4A is inactive or treated with cycloheximide rapidly lose viability. Moreover, after heat inactivation of the cdc33 temperature-sensitive product, the synthesis of most proteins is abolished and only a small group of proteins is still produced. Unexpectedly, starved cdc33 mutant cells whose eIF4E is inactive and which therefore fail to synthesize the bulk of their proteins remain viable for long periods of time, indistinguishable from their isogenic wild-type counterparts. Taken together, our results indicate that eIF4E-independent translation is necessary and sufficient for survival of yeast cells during long periods of starvation. 相似文献
188.
Berenshtein Eduard Vaisman Boris Goldberg-Langerman Chaya Kitrossky Nahum Konijn Abraham M. Chevion Mordechai 《Molecular and cellular biochemistry》2002,(1):283-292
Iron and copper play major roles in biological systems, catalyzing free radical production and consequently causing damage. The relatively high levels of these metals, which are mobilized into the coronary flow following prolonged ischemia, have been incriminated as key players in reperfusion injury to the heart. In the present communication we investigated other roles of iron – providing protection to the ischemic heart via preconditioning (PC).PC was accomplished by subjecting isolated rat hearts to three episodes of 2 min ischemia separated by 3 min of reperfusion. Prolonged ischemia followed the PC phase. PC hearts (group I) were compared to hearts subjected to normal perfusion (group II, no ischemia) and to ischemia without PC (group III). Group I showed a marked improvement in the recovery of hemodynamic function vs. group III. Biochemical parameters further substantiated the PC protection provided to group I against prolonged ischemia. Correspondingly, group I presented markedly lower re-distribution and mobilization of iron and copper into the coronary flow, following prolonged ischemia, as evinced from the decrease in total levels, and in the 'free' fraction of iron and copper.During the PC phase no loss of cardiac function was observed. A small wave of re-distribution and mobilization of iron (typically less than 4–8% of the value of 35 min ischemia) was recorded. The cellular content of ferritin (Ft) measured in the heart was significantly higher in group I than in group III (0.90 and 0.54 g/mg, respectively). Also, iron-saturation of Ft was significantly lower for PC hearts, compared to both groups II and III (0.22 vs. 0.32 and 0.31 g/mg, for 35 min ischemia, respectively). These findings are in accord with the proposal that intracellular re-distribution and mobilization of small levels of iron, during PC, cause rapid accumulation of ferritin – the major iron-storage protein.It is proposed that iron play a dual role: (i) It serves as a signaling pathway for the accumulation of Ft following the PC phase. This iron is not involved in cardiac injury, but rather prepares the heart against future high levels of 'free' iron, thus reducing the degree of myocardial damage after prolonged ischemia. (ii) High levels of iron (and copper) are mobilized following prolonged ischemia and cause tissue damage. 相似文献
189.
Brownstein Z Friedman LM Shahin H Oron-Karni V Kol N Abu Rayyan A Parzefall T Lev D Shalev S Frydman M Davidov B Shohat M Rahile M Lieberman S Levy-Lahad E Lee MK Shomron N King MC Walsh T Kanaan M Avraham KB 《Genome biology》2011,12(9):R89-11
Background
Identification of genes responsible for medically important traits is a major challenge in human genetics. Due to the genetic heterogeneity of hearing loss, targeted DNA capture and massively parallel sequencing are ideal tools to address this challenge. Our subjects for genome analysis are Israeli Jewish and Palestinian Arab families with hearing loss that varies in mode of inheritance and severity.Results
A custom 1.46 MB design of cRNA oligonucleotides was constructed containing 246 genes responsible for either human or mouse deafness. Paired-end libraries were prepared from 11 probands and bar-coded multiplexed samples were sequenced to high depth of coverage. Rare single base pair and indel variants were identified by filtering sequence reads against polymorphisms in dbSNP132 and the 1000 Genomes Project. We identified deleterious mutations in CDH23, MYO15A, TECTA, TMC1, and WFS1. Critical mutations of the probands co-segregated with hearing loss. Screening of additional families in a relevant population was performed. TMC1 p.S647P proved to be a founder allele, contributing to 34% of genetic hearing loss in the Moroccan Jewish population.Conclusions
Critical mutations were identified in 6 of the 11 original probands and their families, leading to the identification of causative alleles in 20 additional probands and their families. The integration of genomic analysis into early clinical diagnosis of hearing loss will enable prediction of related phenotypes and enhance rehabilitation. Characterization of the proteins encoded by these genes will enable an understanding of the biological mechanisms involved in hearing loss. 相似文献190.