全文获取类型
收费全文 | 711篇 |
免费 | 89篇 |
国内免费 | 3篇 |
专业分类
803篇 |
出版年
2023年 | 3篇 |
2022年 | 5篇 |
2021年 | 22篇 |
2020年 | 10篇 |
2019年 | 15篇 |
2018年 | 17篇 |
2017年 | 15篇 |
2016年 | 23篇 |
2015年 | 44篇 |
2014年 | 39篇 |
2013年 | 52篇 |
2012年 | 50篇 |
2011年 | 52篇 |
2010年 | 31篇 |
2009年 | 30篇 |
2008年 | 51篇 |
2007年 | 31篇 |
2006年 | 18篇 |
2005年 | 23篇 |
2004年 | 24篇 |
2003年 | 15篇 |
2002年 | 7篇 |
2001年 | 13篇 |
2000年 | 18篇 |
1999年 | 9篇 |
1998年 | 10篇 |
1997年 | 5篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 12篇 |
1993年 | 6篇 |
1992年 | 12篇 |
1991年 | 9篇 |
1990年 | 14篇 |
1989年 | 7篇 |
1988年 | 10篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1976年 | 5篇 |
1973年 | 5篇 |
1971年 | 4篇 |
1970年 | 5篇 |
1940年 | 3篇 |
1927年 | 2篇 |
1922年 | 2篇 |
排序方式: 共有803条查询结果,搜索用时 15 毫秒
31.
Jeltsje S Cnossen Karlijn C Vollebregt Nynke de Vrieze Gerben ter Riet Ben W J Mol Arie Franx Khalid S Khan Joris A M van der Post 《BMJ (Clinical research ed.)》2008,336(7653):1117-1120
Objective To determine the accuracy of using systolic and diastolic blood pressure, mean arterial pressure, and increase of blood pressure to predict pre-eclampsia.Design Systematic review with meta-analysis of data on test accuracy.Data sources Medline, Embase, Cochrane Library, Medion, checking reference lists of included articles and reviews, contact with authors.Review methods Without language restrictions, two reviewers independently selected the articles in which the accuracy of blood pressure measurement during pregnancy was evaluated to predict pre-eclampsia. Data were extracted on study characteristics, quality, and results to construct 2×2 tables. Summary receiver operating characteristic curves and likelihood ratios were generated for the various levels and their thresholds.Results 34 studies, testing 60 599 women (3341 cases of pre-eclampsia), were included. In women at low risk for pre-eclampsia, the areas under the summary receiver operating characteristic curves for blood pressure measurement in the second trimester were 0.68 (95% confidence interval 0.64 to 0.72) for systolic blood pressure, 0.66 (0.59 to 0.72) for diastolic blood pressure, and 0.76 (0.70 to 0.82) for mean arterial pressure. Findings for the first trimester showed a similar pattern. Second trimester mean arterial pressure of 90 mm Hg or more showed a positive likelihood ratio of 3.5 (95% confidence interval 2.0 to 5.0) and a negative likelihood ratio of 0.46 (0.16 to 0.75). In women deemed to be at high risk, a diastolic blood pressure of 75 mm Hg or more at 13 to 20 weeks’ gestation best predicted pre-eclampsia: positive likelihood ratio 2.8 (1.8 to 3.6), negative likelihood ratio 0.39 (0.18 to 0.71). Additional subgroup analyses did not show improved predictive accuracy.Conclusion When blood pressure is measured in the first or second trimester of pregnancy, the mean arterial pressure is a better predictor for pre-eclampsia than systolic blood pressure, diastolic blood pressure, or an increase of blood pressure. 相似文献
32.
Genetic manipulation of floral pigmentation genes 总被引:4,自引:0,他引:4
Joseph N. M. Mol Antoine R. Stuitje Alexander van der Krol 《Plant molecular biology》1989,13(3):287-294
33.
Tanya M. Smith Paul Tafforeau Adeline Le Cabec Anne Bonnin Alexandra Houssaye Joane Pouech Jacopo Moggi-Cecchi Fredrick Manthi Carol Ward Masrour Makaremi Colin G. Menter 《PloS one》2015,10(2)
Until recently, our understanding of the evolution of human growth and development derived from studies of fossil juveniles that employed extant populations for both age determination and comparison. This circular approach has led to considerable debate about the human-like and ape-like affinities of fossil hominins. Teeth are invaluable for understanding maturation as age at death can be directly assessed from dental microstructure, and dental development has been shown to correlate with life history across primates broadly. We employ non-destructive synchrotron imaging to characterize incremental development, molar emergence, and age at death in more than 20 Australopithecus anamensis, Australopithecus africanus, Paranthropus robustus and South African early Homo juveniles. Long-period line periodicities range from at least 6–12 days (possibly 5–13 days), and do not support the hypothesis that australopiths have lower mean values than extant or fossil Homo. Crown formation times of australopith and early Homo postcanine teeth fall below or at the low end of extant human values; Paranthropus robustus dentitions have the shortest formation times. Pliocene and early Pleistocene hominins show remarkable variation, and previous reports of age at death that employ a narrow range of estimated long-period line periodicities, cuspal enamel thicknesses, or initiation ages are likely to be in error. New chronological ages for SK 62 and StW 151 are several months younger than previous histological estimates, while Sts 24 is more than one year older. Extant human standards overestimate age at death in hominins predating Homo sapiens, and should not be applied to other fossil taxa. We urge caution when inferring life history as aspects of dental development in Pliocene and early Pleistocene fossils are distinct from modern humans and African apes, and recent work has challenged the predictive power of primate-wide associations between hominoid first molar emergence and certain life history variables. 相似文献
34.
35.
Summary HIV dynamics studies, based on differential equations, have significantly improved the knowledge on HIV infection. While first studies used simplified short‐term dynamic models, recent works considered more complex long‐term models combined with a global analysis of whole patient data based on nonlinear mixed models, increasing the accuracy of the HIV dynamic analysis. However statistical issues remain, given the complexity of the problem. We proposed to use the SAEM (stochastic approximation expectation‐maximization) algorithm, a powerful maximum likelihood estimation algorithm, to analyze simultaneously the HIV viral load decrease and the CD4 increase in patients using a long‐term HIV dynamic system. We applied the proposed methodology to the prospective COPHAR2–ANRS 111 trial. Very satisfactory results were obtained with a model with latent CD4 cells defined with five differential equations. One parameter was fixed, the 10 remaining parameters (eight with between‐patient variability) of this model were well estimated. We showed that the efficacy of nelfinavir was reduced compared to indinavir and lopinavir. 相似文献
36.
Timea Marton Murielle Chauvel Adeline Feri Corinne Maufrais Christophe Denfert Mlanie Legrand 《Genetics》2021,218(1)
Genomic rearrangements have been associated with the acquisition of adaptive phenotypes, allowing organisms to efficiently generate new favorable genetic combinations. The diploid genome of Candida albicans is highly plastic, displaying numerous genomic rearrangements that are often the by-product of the repair of DNA breaks. For example, DNA double-strand breaks (DSB) repair using homologous-recombination pathways are a major source of loss-of-heterozygosity (LOH), observed ubiquitously in both clinical and laboratory strains of C. albicans. Mechanisms such as break-induced replication (BIR) or mitotic crossover (MCO) can result in long tracts of LOH, spanning hundreds of kilobases until the telomere. Analysis of I-SceI-induced BIR/MCO tracts in C. albicans revealed that the homozygosis tracts can ascend several kilobases toward the centromere, displaying homozygosis from the break site toward the centromere. We sought to investigate the molecular mechanisms that could contribute to this phenotype by characterizing a series of C. albicans DNA repair mutants, including pol32-/-, msh2-/-, mph1-/-, and mus81-/-. The impact of deleting these genes on genome stability revealed functional differences between Saccharomyces cerevisiae (a model DNA repair organism) and C. albicans. In addition, we demonstrated that ascending LOH tracts toward the centromere are associated with intrinsic features of BIR and potentially involve the mismatch repair pathway which acts upon natural heterozygous positions. Overall, this mechanistic approach to study LOH deepens our limited characterization of DNA repair pathways in C. albicans and brings forth the notion that centromere proximal alleles from DNA break sites are not guarded from undergoing LOH. 相似文献
37.
Chakkiyath Madayi Roshith Ranjan Kumar Manna Vettath Raghavan Suresh Srikanta Samanta Raju Baitha Satish K. Koushlesh Sibina Mol Salim Lohith Kumar Shravan Kumar Sharma Ashis Roychowdhury Muttanahalli Eregowda Vijayakumar Rakesh Pal Basanta Kumar Das 《Zeitschrift fur angewandte Ichthyologie》2021,37(5):795-798
The present study estimated length–weight relationships (LWRs) for six indigenous fish species (Barilius gatensis, Salmostoma acinaces, S. boopis, Puntius amphibius, Hemibagrus punctatus and Ambassis miops) based on specimens collected from River Cauvery (including estuary) during July 2017–January 2020. The sampling surveys were carried out in three distinct sampling seasons, viz., the pre-monsoon (March–May), the monsoon (July–October) and the post-monsoon (November–February). Majority of the fish specimens dealt in the study were collected from multi-meshed monofilament gill nets (mesh sizes 18, 30, 45, 60, 90, 110, 120 and 150 mm) operated by local fishers. For those sites situated in the protected areas, sampling was carried out by cast nets with prior permission from the local administration and the collected fishes were released back into river after length–weight measurements. The length measurements were noted as total length (TL) measured to the nearest 0.1 cm by using a digital Vernier caliper. A digital balance was used for weight measurements with an accuracy of 0.01 g. The study recorded a new maximum length of 48 cm for H. punctatus. The LWR data generated from the present study are significant for proper assessment of the stock status and their management, if collected together with other essential biological and physical parameters. 相似文献
38.
Vincent Fraisier Amal Kasri Stéphanie Miserey-Lenkei Jean-Baptiste Sibarita Deepak Nair Adeline Mayeux Sabine Bardin Yusuke Toyoda Ina Poser Andrei Poznyakovskiy Bruno Goud Anthony A. Hyman Ariane Dimitrov 《PloS one》2013,8(12)
The Golgi apparatus is an intracellular compartment necessary for post-translational modification, sorting and transport of proteins. It plays a key role in mitotic entry through the Golgi mitotic checkpoint. In order to identify new proteins involved in the Golgi mitotic checkpoint, we combine the results of a knockdown screen for mitotic phenotypes and a localization screen. Using this approach, we identify a new Golgi protein C11ORF24 (NP_071733.1). We show that C11ORF24 has a signal peptide at the N-terminus and a transmembrane domain in the C-terminal region. C11ORF24 is localized on the Golgi apparatus and on the trans-Golgi network. A large part of the protein is present in the lumen of the Golgi apparatus whereas only a short tail extends into the cytosol. This cytosolic tail is well conserved in evolution. By FRAP experiments we show that the dynamics of C11ORF24 in the Golgi membrane are coherent with the presence of a transmembrane domain in the protein. C11ORF24 is not only present on the Golgi apparatus but also cycles to the plasma membrane via endosomes in a pH sensitive manner. Moreover, via video-microscopy studies we show that C11ORF24 is found on transport intermediates and is colocalized with the small GTPase RAB6, a GTPase involved in anterograde transport from the Golgi to the plasma membrane. Knocking down C11ORF24 does not lead to a mitotic phenotype or an intracellular transport defect in our hands. All together, these data suggest that C11ORF24 is present on the Golgi apparatus, transported to the plasma membrane and cycles back through the endosomes by way of RAB6 positive carriers. 相似文献
39.
Diversity increases with elevation: empidine dance flies (Diptera,Empididae) challenge a predominant pattern 下载免费PDF全文
Paul Chatelain Adrian Plant Adeline Soulier‐Perkins Christophe Daugeron 《Biotropica》2018,50(4):633-640
Tropical mountain forests are important reservoirs of biodiversity. They are usually species‐rich and often support endemic species making them prime targets for conservation effort. The aim of this study was to investigate elevational patterns of species diversity and phenology to provide a meaningful understanding of insects’ spatio‐temporal distributions along a tropical gradient of elevation. Our study focuses on the Empidinae communities (Diptera, Empididae) from Doi Inthanon (north Thailand, gradient 400–2556 m asl), sampled during two entire years (2006–2007, 2014). This group of insects is more diverse in temperate localities than in the tropics and we found that: (1) increase in altitude and latitude has a similar effect, so that the diversity of our model increases with elevation; (2) the phenology is strongly influenced by seasonality with a peak of diversity occurring during the transition between the dry and rainy seasons; (3) there is no phenological shift in the diversity peak with elevations; and (4) the species composition changes along the altitudinal gradient and through the year (high beta diversity). The increase in diversity with increasing elevation and the peak of diversity occurring at the transitional period both strongly coincide with abiotic factors, the decreasing temperature and the arrival of the monsoon, respectively. 相似文献
40.
Inter‐annual variability of fruit timing and quantity at Nouragues (French Guiana): insights from hierarchical Bayesian analyses 下载免费PDF全文
Irene Mendoza Richard S. Condit S. Joseph Wright Adeline Caubère Patrick Châtelet Isabelle Hardy Pierre‐Michel Forget 《Biotropica》2018,50(3):431-441
The timing and quantity of fruit production are major determinants of the functioning of a forest community, but simultaneous analyses of both are rare. We analyzed a ten‐year dataset (2001–2011) of fruit production for 45 tree and liana species from the Nouragues rain forest, French Guiana. We developed a hierarchical Bayesian approach to determine variation in the timing and quantity of fruit production. Our analysis accommodates missing censuses and quantifies variation at seasonal and inter‐annual scales. The fruiting peak of 22 of 45 species occurred during the peak of the rainy season, which is typical for central and eastern Amazon. The timing and quantity of fruit production varied substantially across years in most species, with greater variation in quantity than in timing. The timing of fruit production varied from continuously fruiting species to mast fruiting species that had two or more consecutive years without fruit production. Fully 40% of species were mast fruiting species. The seasonal timing and inter‐annual variation in fruiting were unrelated to seed dispersal mode across species. We saw no evidence for directional change in the level of fruit production, the timing of fruit production, or their variances; however, 10 yr is a short record for such analyses. 相似文献