全文获取类型
收费全文 | 425篇 |
免费 | 20篇 |
出版年
2022年 | 7篇 |
2021年 | 10篇 |
2020年 | 5篇 |
2019年 | 6篇 |
2018年 | 13篇 |
2017年 | 7篇 |
2016年 | 17篇 |
2015年 | 25篇 |
2014年 | 28篇 |
2013年 | 21篇 |
2012年 | 50篇 |
2011年 | 55篇 |
2010年 | 28篇 |
2009年 | 15篇 |
2008年 | 28篇 |
2007年 | 23篇 |
2006年 | 18篇 |
2005年 | 15篇 |
2004年 | 29篇 |
2003年 | 16篇 |
2002年 | 8篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 3篇 |
1998年 | 2篇 |
1997年 | 2篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1975年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有445条查询结果,搜索用时 127 毫秒
91.
This paper describes some of the results of the first national-level survey on sexual behaviour and the distribution of risks to sexually transmitted infections (STIs), including human immunodeficiency virus infection (HIV), among youth in Croatia, and the nature and the extent of their vulnerability to these adverse health outcomes. The study was a cross-sectional, probability-based household survey conducted in 2005, and included 1093 respondents aged 18-24. This paper aims to describe the findings related to the knowledge of HIV transmission, key behavioural outcomes relevant for potential transmission of HIV and STIs, and correlates of genital discharge in young men and young women. More than 80% of young people know that the correct use of condoms protects against HIV and that HIV can be transmitted by someone who looks healthy. Fifty-nine percent of young men and 52.4% of young women reported using condoms during the first sexual intercourse, and 59.3% of men and 46.1% of women used condoms during the last sexual intercourse with a casual partner. This points to the gap between knowledge of condom use and the actual use of condoms as a high proportion of risky sexual contact remain unprotected. Having sexual intercourse frequently or regularly while consuming alcohol was reported by 19.2% of men and 7.6% of women. Much lower proportion are using drugs frequently or regularly during sexual intercourse (3.7% of men and 2.1% of women). Among those sexually experienced, 11.8% of men and 44.1% of women reported ever having a genital discharge. Higher presence of genital discharge in women is suggestive of reproductive tract infections that are not necessarily sexually transmitted. In the multivariate analysis, the lack of knowledge of whether chlamydial infections is an STI and having more than five partners in life were correlates of genital discharge in men, while in women the correlates included having more than five partners in life and not using condoms during the first sexual intercourse. Higher burden of STI-related symptoms was found among men who have men as sexual partners, those who paid for sex, and those with concurrent partnerships. These findings point out to the immediate need to strengthen sexual health education among young people and to the necessity for further development of other broad-based interventions to prevent adverse sexual health outcomes among both men and women, as well as those targeted towards more vulnerable subgroups. 相似文献
92.
Sandro Bertolino Luc Wauters Aleksandar Pizzul Ambrogio Molinari Peter Lurz Guido Tosi 《Mammalian Biology》2009,74(3):210-219
Monitoring constitutes a key element in the management and conservation of many mammal species. We describe a technique to obtain population indices for red squirrels (Sciurus vulgaris) using hair-tubes and compare these indices to population estimates obtained by live trapping. Data were collected in seven study areas in the Western and Central Alps in Italy and compared with data previously collected in 11 sites in northern England. The aim was to test if hair-tube census could be used to derive a general predictive model allowing accurate predictions of squirrel numbers in different years, habitats and geographic regions. We used model equations developed from the proportion of hair-tubes visited to predict densities obtained from live-trapping. Hair-tube data gathered in the Central Alps correctly predicted squirrel densities in the Western Alps. A combined data set pooling the sites of these two regions based on the first three years successfully predicted the two successive years. In addition, a combined model derived from areas monitored for five years had a high predictive value locally (89%) and internationally (73%) when applied to the English data set. We therefore believe that the predictive model developed in this study could be of general value and be used to monitor squirrel populations in European low density conifer habitats (0.1–0.5 squirrels/ha). The approach may also be suitable for many tree squirrel populations in North America and other arboreal rodents that occur at similar densities. 相似文献
93.
In Caulobacter crescentus, intact cables of the actin homologue, MreB, are required for the proper spatial positioning of MurG which catalyses the final step in peptidoglycan precursor synthesis. Similarly, in the periplasm, MreC controls the spatial orientation of the penicillin binding proteins and a lytic transglycosylase. We have now found that MreB cables are required for the organization of several other cytosolic murein biosynthetic enzymes such as MraY, MurB, MurC, MurE and MurF. We also show these proteins adopt a subcellular pattern of localization comparable to MurG, suggesting the existence of cytoskeletal‐dependent interactions. Through extensive two‐hybrid analyses, we have now generated a comprehensive interaction map of components of the bacterial morphogenetic complex. In the cytosol, this complex contains both murein biosynthetic enzymes and morphogenetic proteins, including RodA, RodZ and MreD. We show that the integral membrane protein, MreD, is essential for lateral peptidoglycan synthesis, interacts with the precursor synthesizing enzymes MurG and MraY, and additionally, determines MreB localization. Our results suggest that the interdependent localization of MreB and MreD functions to spatially organize a complex of peptidoglycan precursor synthesis proteins, which is required for propagation of a uniform cell shape and catalytically efficient peptidoglycan synthesis. 相似文献
94.
The research aim was to investigate and establish the perception of health among population groups with different number of industrial polluters in their living environment. Namely, the Kostrena living area (3250 inhabitants) is situated near big industrial pollutant producers: INA oil refinery Urinj, thermo power plant Rijeka, shipyard "Viktor Lenac", while in Crikvenica living area such pollutant producers do not exist. In this research 146 subjects from Kostrena participated (74 men and 72 women with age average 40.8, SD 9.2 years), and 157 subjects from Crikvenica area (79 men and 78 women with age average 39.4, SD 10.1 years). The perception of health was measured by the means of SF-36 questionnaire variables. Lung function (FEV1, FVC, FEV25/75, PEF), cardiovascular function (systolic and diastolic arterial blood pressure, heart rate were also measured, including body proportion measures by the means of waste and hip circumference and silhouette test, in order to establish the eventual objective physical health parameter difference among examined population groups. Subjects from Kostrena perceived their general health, mental health, and vitality worse than subjects from Crikvenica. Group from Kostrena felt themself more limited in their roles due to emotional problems, perceiving more pain than group from Crikvenica. On the opposite site, social functioning of subjects from Kostrena was better in comparison to Crikvenica group. No signifficant differences between groups were found in physical functioning and in role limitation due to physical problems. In addition, there were no significant differences between groups in objective physical health parameters, such as pulmonary function, arterial blood pressure, pulse, and waist to hip ratio. Subjects using sensoric systems and the mental cognition about harmful environmental factors, perceive their health worse if there are present industrial resources in their environment, even when concentration of the pollutants are within legal ranges. 相似文献
95.
The cockroach, Periplaneta americana represents a basal insect lineage that undergoes the ancestral hemimetabolous mode of development. Here, we examine the embryonic and post-embryonic functions of the hox gene Scr in Periplaneta as a way of better understanding the roles of this gene in the evolution of insect body plans. During embryogenesis, Scr function is strictly limited to the head with no role in the prothorax. This indicates that the ancestral embryonic function of Scr was likely restricted to the head, and that the posterior expansion of expression in the T1 legs may have preceded any apparent gain of function during evolution. In addition, Scr plays a pivotal role in the formation of the dorsal ridge, a structure that separates the head and thorax in all insects. This is evidenced by the presence of a supernumerary segment that occurs between the labial and T1 segments of RNAiScr first nymphs and is attributed to an alteration in engrailed (en) expression. The fact that similar Scr phenotypes are observed in Tribolium but not in Drosophila or Oncopeltus reveals the presence of lineage-specific variation in the genetic architecture that controls the formation of the dorsal ridge. In direct contrast to the embryonic roles, Scr has no function in the head region during post-embryogenesis in Periplaneta, and instead, strictly acts to provide identity to the T1 segment. Furthermore, the strongest Periplaneta RNAiScr phenotypes develop ectopic wing-like tissue that originates from the posterior region of the prothoracic segment. This finding provides a novel insight into the current debate on the morphological origin of insect wings. 相似文献
96.
Ivana Nikolic Tatjana Kastratovic Aleksandar Zivanovic Marina Mitrovic 《Biochemical and biophysical research communications》2010,395(2):225-231
Proteins of the BCL-2 family are important regulators of apoptosis. The BCL-2 family includes three main subgroups: the anti-apoptotic group, such as BCL-2, BCL-XL, BCL-W, and MCL-1; multi-domain pro-apoptotic BAX, BAK; and pro-apoptotic “BH3-only” BIK, PUMA, NOXA, BID, BAD, and SPIKE. SPIKE, a rare pro-apoptotic protein, is highly conserved throughout the evolution, including Caenorhabditis elegans, whose expression is downregulated in certain tumors, including kidney, lung, and breast.In the literature, SPIKE was proposed to interact with BAP31 and prevent BCL-XL from binding to BAP31. Here, we utilized the Position Weight Matrix method to identify SPIKE to be a BH3-only pro-apoptotic protein mainly localized in the cytosol of all cancer cell lines tested. Overexpression of SPIKE weakly induced apoptosis in comparison to the known BH3-only pro-apoptotic protein BIK. SPIKE promoted mitochondrial cytochrome c release, the activation of caspase 3, and the caspase cleavage of caspase’s downstream substrates BAP31 and p130CAS. Although the informatics analysis of SPIKE implicates this protein as a member of the BH3-only BCL-2 subfamily, its role in apoptosis remains to be elucidated. 相似文献
97.
98.
Cristian Coarfa Fuli Yu Christopher A Miller Zuozhou Chen R Alan Harris Aleksandar Milosavljevic 《BMC bioinformatics》2010,11(1):572
Background
Massively parallel sequencing readouts of epigenomic assays are enabling integrative genome-wide analyses of genomic and epigenomic variation. Pash 3.0 performs sequence comparison and read mapping and can be employed as a module within diverse configurable analysis pipelines, including ChIP-Seq and methylome mapping by whole-genome bisulfite sequencing. 相似文献99.
Milosavljevic A 《Nature biotechnology》2010,28(10):1053-1056
Comparative analysis of epigenomes offers new opportunities to understand cellular differentiation, mutation effects and disease processes. But the scale and heterogeneity of epigenetic data present numerous computational challenges. 相似文献
100.
Blomaee accumulation, leaf longevity and growth rate of two spring forest geophytes, Scllla blfolla L. and Arum maculatum L. were estimated separately for three size groups within each population of these species. Despite the differences in leaf longevity, both species showed a similar pattern of blomass accumulation In relation to their phenologles and reproductive demands. Eco-physlological acclimation to changing light environment was assumed through photosynthetic parameters and dynamics of leaf area Index In the predominant size group of each species. A light response curve was measured under natural light for each species through the continuum of Its phenology to quantify the photosynthetic photon flux density at light saturation, light-saturated photosynthetic rate, light compensation point, and dark respiration. Light-saturated assimilation per leaf area basis, dark respiration rate and light compensation points were significantly higher in S. blfolla relative to A. maculatum. However, the acclimation of photosynthesis that would respond to light changes in environment was not found in S. bifolla. In contrast, In A. maculatum a marked shift In the light dependence of photosynthesis through the season was noticed, which resulted In a strong photosynthetic acclimation to the low-light conditions. Accompanied by significant leaf area Index, this efficient low-light photosynthesis enabled greater leaf longevity, and consequently longer accumulative period to A. maculatum. From the different parameters that we determined (both photosynthetic acclimation and growth strategy) it would appear that these species belong to two distinct subgroups: S. blfolla to the early and A. maculatum to the late vernals. 相似文献