全文获取类型
收费全文 | 3061篇 |
免费 | 308篇 |
国内免费 | 2篇 |
专业分类
3371篇 |
出版年
2023年 | 13篇 |
2022年 | 45篇 |
2021年 | 76篇 |
2020年 | 46篇 |
2019年 | 66篇 |
2018年 | 63篇 |
2017年 | 81篇 |
2016年 | 108篇 |
2015年 | 163篇 |
2014年 | 183篇 |
2013年 | 193篇 |
2012年 | 219篇 |
2011年 | 209篇 |
2010年 | 157篇 |
2009年 | 131篇 |
2008年 | 158篇 |
2007年 | 179篇 |
2006年 | 136篇 |
2005年 | 143篇 |
2004年 | 96篇 |
2003年 | 131篇 |
2002年 | 96篇 |
2001年 | 65篇 |
2000年 | 65篇 |
1999年 | 64篇 |
1998年 | 29篇 |
1997年 | 24篇 |
1996年 | 35篇 |
1995年 | 14篇 |
1994年 | 17篇 |
1993年 | 24篇 |
1992年 | 29篇 |
1991年 | 28篇 |
1990年 | 28篇 |
1989年 | 28篇 |
1988年 | 19篇 |
1987年 | 28篇 |
1986年 | 27篇 |
1985年 | 19篇 |
1984年 | 7篇 |
1983年 | 13篇 |
1981年 | 9篇 |
1980年 | 9篇 |
1979年 | 12篇 |
1978年 | 8篇 |
1977年 | 11篇 |
1976年 | 7篇 |
1975年 | 8篇 |
1974年 | 7篇 |
1973年 | 8篇 |
排序方式: 共有3371条查询结果,搜索用时 15 毫秒
101.
Rotem Kadir Tamar Harel Barak Markus Yonatan Perez Anna Bakhrat Idan Cohen Michael Volodarsky Miora Feintsein-Linial Elana Chervinski Joel Zlotogora Sara Sivan Ramon Y. Birnbaum Uri Abdu Stavit Shalev Ohad S. Birk 《PLoS genetics》2016,12(3)
Primary microcephaly is a congenital neurodevelopmental disorder of reduced head circumference and brain volume, with fewer neurons in the cortex of the developing brain due to premature transition between symmetrical and asymmetrical cellular division of the neuronal stem cell layer during neurogenesis. We now show through linkage analysis and whole exome sequencing, that a dominant mutation in ALFY, encoding an autophagy scaffold protein, causes human primary microcephaly. We demonstrate the dominant effect of the mutation in drosophila: transgenic flies harboring the human mutant allele display small brain volume, recapitulating the disease phenotype. Moreover, eye-specific expression of human mutant ALFY causes rough eye phenotype. In molecular terms, we demonstrate that normally ALFY attenuates the canonical Wnt signaling pathway via autophagy-dependent removal specifically of aggregates of DVL3 and not of Dvl1 or Dvl2. Thus, autophagic attenuation of Wnt signaling through removal of Dvl3 aggregates by ALFY acts in determining human brain size. 相似文献
102.
103.
Avi Z. Rosenberg Michael D. Armani Patricia A. Fetsch Liqiang Xi Tina Thu Pham Mark Raffeld Yun Chen Neil O’Flaherty Rebecca Stussman Adele R. Blackler Qiang Du Jeffrey C. Hanson Mark J. Roth Armando C. Filie Michael H. Roh Michael R. Emmert-Buck Jason D. Hipp Michael A. Tangrea 《PloS one》2016,11(3)
104.
105.
Ian W. Pray Dallas J. Swanson Viterbo Ayvar Claudio Muro Luz M. Moyano Armando E. Gonzalez Hector H. Garcia Seth E. O’Neal Cysticercosis Working Group in Peru 《PLoS neglected tropical diseases》2016,10(4)
Background
Taenia solium, a parasitic cestode that affects humans and pigs, is the leading cause of preventable epilepsy in the developing world. T. solium eggs are released into the environment through the stool of humans infected with an adult intestinal tapeworm (a condition called taeniasis), and cause cysticercosis when ingested by pigs or other humans. A control strategy to intervene within high-risk foci in endemic communities has been proposed as an alternative to mass antihelminthic treatment. In this ring strategy, antihelminthic treatment is targeted to humans and pigs residing within a 100 meter radius of a pig heavily-infected with cysticercosis. Our aim was to describe the roaming ranges of pigs in this region, and to evaluate whether the 100 meter radius rings encompass areas where risk factors for T. solium transmission, such as open human defecation and dense pig activity, are concentrated.Methodology/Principal Findings
In this study, we used Global Positioning System (GPS) devices to track pig roaming ranges in two rural villages of northern Peru. We selected 41 pigs from two villages to participate in a 48-hour tracking period. Additionally, we surveyed all households to record the locations of open human defecation areas. We found that pigs spent a median of 82.8% (IQR: 73.5, 94.4) of their time roaming within 100 meters of their homes. The size of home ranges varied significantly by pig age, and 93% of the total time spent interacting with open human defecation areas occurred within 100 meters of pig residences.Conclusions/Significance
These results indicate that 100 meter radius rings around heavily-infected pigs adequately capture the average pig’s roaming area (i.e., home range) and represent an area where the great majority of exposure to human feces occurs. 相似文献106.
Lilian?Rumi?Tsuruta Mariana?Lopes dos Santos Fernanda?Perez?Yeda Oswaldo?Keith?Okamoto Ana?Maria?MoroEmail author 《Applied microbiology and biotechnology》2016,100(23):10031-10041
Genetic characterization of protein-producing clones represents additional value to cell line development. In the present study, ten Per.C6 clones producing a Rebmab100 monoclonal antibody were selected using two cloning methods: six clones originated from limiting dilution cloning and four by the automated colony picker ClonePix FL. A stability program was performed for 50 generations, including 4 batches distributed along the timeframe to determine specific productivity (Qp) maintenance. Four stable clones (two from limiting dilution and two from ClonePix FL) were further evaluated. The relative mRNA expression levels of both heavy chain (HC) and light chain (LC) genes were verified at generations 0, 30–35, and 50–55 of the stability program. At generations 0 and 30–35, LC gene expression level was higher than HC gene, whereas at generation 50–55, the opposite prevailed. A high correlation was observed between Qp and HC or LC mRNA expression level for all clones at each generation analyzed along the continuous culture. The mRNA stability study was performed at steady-state culture. The LC gene displayed a higher half-life and lower decay constant than HC gene, accounting for the higher observed expression level of LC mRNA in comparison to HC mRNA. Clone R6 was highlighted due its high Qp, mRNA expression levels, and mRNA stability. Besides the benefits of applying genetic characterization for the selection of stable and high-producing clones, the present study shows for the first time the correlation between Qp and HC or LC expression levels and also mRNA stability in clones derived from human cell line Per.C6(®). 相似文献
107.
108.
109.
George G. Harrigan Tyamagondlu V. Venkatesh Mark Leibman Jonathan Blankenship Timothy Perez Steven Halls Alexander W. Chassy Oliver Fiehn Yun Xu Royston Goodacre 《Metabolomics : Official journal of the Metabolomic Society》2016,12(5):82
Introduction
Past studies on plant metabolomes have highlighted the influence of growing environments and varietal differences in variation of levels of metabolites yet there remains continued interest in evaluating the effect of genetic modification (GM).Objectives
Here we test the hypothesis that metabolomics differences in grain from maize hybrids derived from a series of GM (NK603, herbicide tolerance) inbreds and corresponding negative segregants can arise from residual genetic variation associated with backcrossing and that the effect of insertion of the GM trait is negligible.Methods
Four NK603-positive and negative segregant inbred males were crossed with two different females (testers). The resultant hybrids, as well as conventional comparator hybrids, were then grown at three replicated field sites in Illinois, Minnesota, and Nebraska during the 2013 season. Metabolomics data acquisition using gas chromatography–time of flight-mass spectrometry (GC–TOF-MS) allowed the measurement of 367 unique metabolite features in harvested grain, of which 153 were identified with small molecule standards. Multivariate analyses of these data included multi-block principal component analysis and ANOVA-simultaneous component analysis. Univariate analyses of all 153 identified metabolites was conducted based on significance testing (α = 0.05), effect size evaluation (assessing magnitudes of differences), and variance component analysis.Results
Results demonstrated that the largest effects on metabolomic variation were associated with different growing locations and the female tester. They further demonstrated that differences observed between GM and non-GM comparators, even in stringent tests utilizing near-isogenic positive and negative segregants, can simply reflect minor genomic differences associated with conventional back-crossing practices.Conclusion
The effect of GM on metabolomics variation was determined to be negligible and supports that there is no scientific rationale for prioritizing GM as a source of variation.110.
Cretaceous angiosperm pollen from the Kachaike Formation,south-western Santa Cruz Province,Argentina
V.S. Perez Loinaze V.D. Barreda S. Archangelsky A. Archangelsky 《Historical Biology》2016,28(7):941-951
Thirty-three angiosperm pollen species are here reported from mid-Cretaceous deposits of the Kachaike Formation, Austral Basin, southern Argentina. Clavatipollenites is the most abundant angiosperm genus, with six well-defined morphological groups recognised on the basis of their reticulum morphology and sculpture. Pollen of eudicots are scarce, represented by tricolpate (Psilatricolpites spp. and Tricolpites spp.), tricolporoidate and tricolporate morphotypes (Dryadopollis spp.). Increasing complexity in the aperture structure is seen throughout the sequence; tricolpate and tricolporoidate forms are recorded in almost all samples, while tricolporate pollen grains are restricted to the middle and upper levels of the unit. The high species richness and abundance of monocolpate-ulcerate angiosperm related to monocots or magnoliids sensu lato recorded in the unit is comparable to that previously recognised in other assemblages from the early and middle Albian of the southern (e.g. Australia) and northern hemispheres (e.g. Western Portuguese basin, Europe). The recorded increase in the number of angiosperm species towards the middle and upper parts of the Kachaike Formation, with the presence of monocolpate, tricolpate, tricolporoidate and tricolporate pollen, suggests an early-early middle Albian age for these parts of the unit, in agreement with the early Albian age proposed for its basal levels on the basis of dinoflagellates. 相似文献