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   326篇
  免费   18篇
  2024年   1篇
  2023年   3篇
  2022年   2篇
  2021年   6篇
  2020年   3篇
  2019年   8篇
  2018年   7篇
  2017年   2篇
  2016年   8篇
  2015年   18篇
  2014年   14篇
  2013年   23篇
  2012年   37篇
  2011年   26篇
  2010年   15篇
  2009年   14篇
  2008年   17篇
  2007年   19篇
  2006年   18篇
  2005年   16篇
  2004年   11篇
  2003年   12篇
  2002年   18篇
  2001年   3篇
  2000年   3篇
  1999年   3篇
  1998年   3篇
  1997年   1篇
  1996年   3篇
  1995年   2篇
  1994年   5篇
  1991年   4篇
  1990年   2篇
  1988年   3篇
  1986年   1篇
  1985年   1篇
  1982年   1篇
  1981年   2篇
  1980年   1篇
  1978年   1篇
  1973年   2篇
  1968年   1篇
  1930年   2篇
  1928年   1篇
  1927年   1篇
排序方式: 共有344条查询结果,搜索用时 15 毫秒
281.

Objective

To identify current risk factors for hepatitis C virus (HCV) transmission in Greater Cairo.

Design and Setting

A 1∶1 matched case-control study was conducted comparing incident acute symptomatic hepatitis C patients in two “fever” hospitals of Greater Cairo with two control groups: household members of the cases and acute hepatitis A patients diagnosed at the same hospitals. Controls were matched on the same age and sex to cases and were all anti-HCV antibody negative. Iatrogenic, community and household exposures to HCV in the one to six months before symptoms onset for cases, and date of interview for controls, were exhaustively assessed.

Results

From 2002 to 2007, 94 definite acute symptomatic HCV cases and 188 controls were enrolled in the study. In multivariate analysis, intravenous injections (OR = 5.0; 95% CI = 1.2–20.2), medical stitches (OR = 4.2; 95% CI = 1.6–11.3), injection drug use (IDU) (OR = 7.9; 95% CI = 1.4–43.5), recent marriage (OR = 3.3; 95% CI = 1.1–9.9) and illiteracy (OR = 3.9; 95% CI = 1.8–8.5) were independently associated with an increased HCV risk.

Conclusion

In urban Cairo, invasive health care procedures remain a source of HCV transmission and IDU is an emerging risk factor. Strict application of standard precautions during health care is a priority. Implementation of comprehensive infection prevention programs for IDU should be considered.  相似文献   
282.
283.
284.
285.
Cereal embryos are a model system to study desiccation tolerance due to their ability to survive extreme water loss during late embryogenesis. To identify proteins accumulating in mature embryos which can be used as potential markers for dehydration tolerance, we compared the embryo proteome from two durum wheat genotypes (Triticum durum Desf.), Mahmoudi (salt and drought sensitive) and Om Rabia3 (salt and drought tolerant). Total protein extracts from wheat embryos were analyzed by using conventional 2-DE and ProteomeLab PF-2D. Analysis using different pH ranges showed that a larger number of fractions were solved by LC, than by conventional 2-DE at extreme technical pHs (pH 4.0–5.0 and pH 6.5–8.0). In contrast, at intermediate pHs (pH 5.0–6.5), resolution was better in 2-DE gels. The two techniques were used in parallel to analyze total protein extracts from embryos of the two wheat varieties. Several proteins belonging to the seed storage family, LEA-type/heat shock proteins, enzyme metabolism and radical scavengers were identified by analysis of trypsin digested peptides via mass spectrometry. These proteins accumulate in different amounts in embryos of tolerant and sensitive wheat varieties. The differences in expression pattern were further validated by enzyme activity, western blotting analysis and correlated with their corresponding mRNA expression by RT-PCR analyses for the corresponding protein. We suggest that the differential expression pattern could be used as a basis for a biochemical screen of tolerance/sensitivity to drought and salt stress in wheat embryos and germplasm.  相似文献   
286.
Rabbit pups are only nursed for about 3 min once a day. They depend on a pheromone on the mother's ventrum to locate nipples and on tactile stimulation of the muzzle to grasp them. In a continuing study of the sensory input guiding suckling behavior we investigated the whisker array in newborn pups and the possible contribution of the whiskers to suckling. Rabbits are born with approximately 76 whiskers arranged in seven to nine rows and increasing in length from rostral to caudal. No significant difference was found between pups with whiskers cut and intact controls in latency to perform the stereotyped nipple-search behavior, latency to attach to nipples, time spent on nipples, milk ingested, or in the strength of conditioning to a novel odor paired with suckling. Thus, the whiskers do not seem important for suckling in newborn rabbits.

Zusammenfassung

Tragen die Schnurrhaare bei neugeborenen Kaninchen (Oryctolgus cuniculus) zum Zitzensuch- und Saugverhalten bei?Jungkaninchen werden nur einmal am Tag für etwa drei Minuten gesäugt. Für das Auffinden der Zitzen sind sie auf ein Pheromon auf der Bauchhaut der Mutter angewiesen, und für deren Ergreifen auf periorale taktile Reize. In Fortsetzung unserer Untersuchungen zur sensorischen Kontrolle dieses Verhaltens beschreiben wir die Anordnung der Schnurrhaare bei neugeborenen Kaninchen und untersuchen ihren möglichen Beitrag zum Säugeverhalten. Bei der Geburt besitzen Jungkaninchen etwa 76, in 7–9 Reihen angeordnete Schnurrhaare, deren Länge von rostral nach caudal zunimmt. Nach Abschneiden der Schnurrhaare wurden keine signifikanten Unterschiede zwischen Jungen mit und ohne Schnurrhaare beobachtet, sowohl in der Latenz des Zitzensuchens, des Zitzenfassens, wie in der Besaugungsdauer, der erhaltenen Milchmenge oder dem Grad der Konditionierung auf einen neuen Geruchsstoff. Demnach spielen bei neugeborenen Kaninchen die Schnurrhaare keine wesentliche Rolle für das Auffinden und Besaugen von Zitzen.  相似文献   
287.
Although considered effective treatment for many yeast fungi, the therapeutic efficacy of the echinocandin class of antifungals for invasive aspergillosis (IA) is limited. Recent studies suggest intense kinase- and phosphatase-mediated echinocandin adaptation in A. fumigatus. To identify A. fumigatus protein kinases required for survival under echinocandin stress, we employed CRISPR/Cas9-mediated gene targeting to generate a protein kinase disruption mutant library in a wild type genetic background. Cell wall and echinocandin stress screening of the 118 disruption mutants comprising the library identified only five protein kinase disruption mutants displaying greater than 4-fold decreased echinocandin minimum effective concentrations (MEC) compared to the parental strain. Two of these mutated genes, the previously uncharacterized A. fumigatus sepL and sidB genes, were predicted to encode protein kinases functioning as core components of the Septation Initiation Network (SIN), a tripartite kinase cascade that is necessary for septation in fungi. As the A. fumigatus SIN is completely uncharacterized, we sought to explore these network components as effectors of echinocandin stress survival. Our data show that mutation of any single SIN kinase gene caused complete loss of hyphal septation and increased susceptibility to cell wall stress, as well as widespread hyphal damage and loss of viability in response to echinocandin stress. Strikingly, mutation of each SIN kinase gene also resulted in a profound loss of virulence characterized by lack of tissue invasive growth. Through the deletion of multiple novel regulators of hyphal septation, we show that the non-invasive growth phenotype is not SIN-kinase dependent, but likely due to hyphal septation deficiency. Finally, we also find that echinocandin therapy is highly effective at eliminating residual tissue burden in mice infected with an aseptate strain of A. fumigatus. Together, our findings suggest that inhibitors of septation could enhance echinocandin-mediated killing while simultaneously limiting the invasive potential of A. fumigatus hyphae.  相似文献   
288.
289.
Phosphorylation mediates the nuclear targeting of the maize Rab17 protein   总被引:14,自引:2,他引:12  
The maize abscisic acid-responsive Rab17 protein localizes to the nucleus and cytoplasm in maize cells. In-frame fusion of Rab17 to the reporter protein β-glucuronidase (GUS) directed GUS to the nucleus and cytoplasm in transgenic Arabidopsis thaliana and in transiently transformed onion cells. Analysis of chimeric constructs identified one region between amino acid positions 66–96, which was necessary for targeting GUS to the nucleus. This region contains a serine cluster followed by a putative consensus site for protein kinase CK2 phosphorylation, and a stretch of basic amino acids resembling the simian virus 40 large T antigen-type nuclear localization signal (NLS). Mutation of two basic amino acids in the putative NLS had a weak effect on nuclear targeting in the onion cell system and did not modify the percentage of nuclear fusion protein in the Arabidopsis cells. The mutation of three amino acids in the consensus site for CK2 recognition resulted in the absence of in vitro phosphorylated forms of Rab17 and in a strong decrease of GUS enzymatic activity in isolated nuclei of transgenic Arabidopsis. These results suggest that phosphorylation of Rab17 by protein kinase CK2 is the relevant step for its nuclear location, either by facilitating binding to specific proteins or as a direct part of the nuclear targeting apparatus.  相似文献   
290.
Hyperactivated motility was studied in guinea pig spermatozoa. In the presence of the local anesthetic procaine, a high number of sperm cells (64%) showed hyperactivation when incubated in minimal culture medium with pyruvate, lactate, and glucose. Hyperactivated motility was dependent on glucose in the medium. Sperm ATP concentration was increased twofold in hyperactivated sperm when compared to procaine-treated nonhyperactivated cells. cAMP levels were also higher in hyperactivated cells than in control spermatozoa. Thus, in living spermatozoa high levels of ATP appear to be needed to generate hyperactivation. cAMP is present at a high concentration in hyperactivated spermatozoa, therefore a role of cAMP in hyperactivation cannot be excluded. Depletion of external Ca2+ did not inhibit procaine-induced hyperactivated motility. Hence, procaine canceled the requirement of external Ca2+ for sperm to express hyperactivated motility. © 1994 Wiley-Liss, Inc.  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