全文获取类型
收费全文 | 2054篇 |
免费 | 243篇 |
国内免费 | 1篇 |
出版年
2021年 | 27篇 |
2020年 | 18篇 |
2019年 | 19篇 |
2018年 | 20篇 |
2017年 | 18篇 |
2016年 | 25篇 |
2015年 | 59篇 |
2014年 | 71篇 |
2013年 | 81篇 |
2012年 | 96篇 |
2011年 | 95篇 |
2010年 | 53篇 |
2009年 | 49篇 |
2008年 | 64篇 |
2007年 | 84篇 |
2006年 | 79篇 |
2005年 | 81篇 |
2004年 | 70篇 |
2003年 | 63篇 |
2002年 | 63篇 |
2001年 | 64篇 |
2000年 | 54篇 |
1999年 | 62篇 |
1998年 | 41篇 |
1997年 | 27篇 |
1996年 | 19篇 |
1995年 | 18篇 |
1994年 | 13篇 |
1993年 | 22篇 |
1992年 | 48篇 |
1991年 | 45篇 |
1990年 | 56篇 |
1989年 | 43篇 |
1988年 | 37篇 |
1987年 | 33篇 |
1986年 | 32篇 |
1985年 | 33篇 |
1984年 | 24篇 |
1983年 | 33篇 |
1982年 | 40篇 |
1981年 | 22篇 |
1980年 | 19篇 |
1979年 | 28篇 |
1978年 | 34篇 |
1977年 | 26篇 |
1976年 | 26篇 |
1975年 | 17篇 |
1974年 | 16篇 |
1973年 | 22篇 |
1968年 | 15篇 |
排序方式: 共有2298条查询结果,搜索用时 15 毫秒
111.
112.
Sil H. J. van Lieshout Amanda Bretman Chris Newman Christina D. Buesching David W. Macdonald Hannah L. Dugdale 《Molecular ecology》2019,28(18):4152-4165
Individual variation in survival probability due to differential responses to early‐life environmental conditions is important in the evolution of life histories and senescence. A biomarker allowing quantification of such individual variation, and which links early‐life environmental conditions with survival by providing a measure of conditions experienced, is telomere length. Here, we examined telomere dynamics among 24 cohorts of European badgers (Meles meles). We found a complex cross‐sectional relationship between telomere length and age, with no apparent loss over the first 29 months, but with both decreases and increases in telomere length at older ages. Overall, we found low within‐individual consistency in telomere length across individual lifetimes. Importantly, we also observed increases in telomere length within individuals, which could not be explained by measurement error alone. We found no significant sex differences in telomere length, and provide evidence that early‐life telomere length predicts lifespan. However, while early‐life telomere length predicted survival to adulthood (≥1 year old), early‐life telomere length did not predict adult survival probability. Furthermore, adult telomere length did not predict survival to the subsequent year. These results show that the relationship between early‐life telomere length and lifespan was driven by conditions in early‐life, where early‐life telomere length varied strongly among cohorts. Our data provide evidence for associations between early‐life telomere length and individual life history, and highlight the dynamics of telomere length across individual lifetimes due to individuals experiencing different early‐life environments. 相似文献
113.
114.
Joel Ralston Lydia Lorenc Melissa Montes William V. DeLuca Jeremy J. Kirchman Bradley K. Woodworth Stuart A. Mackenzie Amy Newman Hilary A. Cooke Nikole E. Freeman Alex O. Sutton Lila Tauzer D. Ryan Norris 《Ecology and evolution》2019,9(15):8840-8855
Migratory behaviors such as the timing and duration of migration are genetically inherited and can be under strong natural selection, yet we still know very little about the specific genes or molecular pathways that control these behaviors. Studies in candidate genes Clock and Adcyap1 have revealed that both of these loci can be significantly correlated with migratory behaviors in birds, though observed relationships appear to vary across species. We investigated geographic genetic structure of Clock and Adcyap1 in four populations of blackpoll warblers (Setophaga striata), a Neotropical–Nearctic migrant that exhibits geographic variation in migratory timing and duration across its boreal breeding distribution. Further, we used data on migratory timing and duration, obtained from light‐level geolocator trackers to investigate candidate genotype–phenotype relationships at the individual level. While we found no geographic structure in either candidate gene, we did find evidence that candidate gene lengths are correlated with five of the six migratory traits. Maximum Clock allele length was significantly and negatively associated with spring arrival date. Minimum Adcyap1 allele length was significantly and negatively associated with spring departure date and positively associated with fall arrival date at the wintering grounds. Additionally, we found a significant interaction between Clock and Adcyap1 allele lengths on both spring and fall migratory duration. Adcyap1 heterozygotes also had significantly shorter migration duration in both spring and fall compared to homozygotes. Our results support the growing body of evidence that Clock and Adcyap1 allele lengths are correlated with migratory behaviors in birds. 相似文献
115.
METTE SERINE WESMAJERVI TEKLE TAFESE J
RGEN STENVIK KJERSTI TURID FJALESTAD B
RGE DAMSGRD MADJID DELGHANDI 《Molecular ecology resources》2007,7(1):138-140
One hundred and fifty random clones from an enriched genomic library of Atlantic cod were sequenced. Primer pairs were designed for 15 microsatellites containing perfect di‐, tri‐, tetra‐ and hexanucleotide repeats and characterized in 96 unrelated fish. Eight markers were successfully amplified, with the number of alleles ranging from two to nine per locus and observed heterozygosity ranging from 0.341 to 0.977. Loci Gmo‐G13 and Gmo‐G14 had a significant excess of homozygotes. All loci conformed to the Hardy–Weinberg equilibrium. Genetic linkage disequilibrium analysis between all pairs of the loci showed no significant departure from the null hypothesis between any of the loci. 相似文献
116.
Mark C. Derbyshire Toby E. Newman Yuphin Khentry Akeem Owolabi Taiwo 《Molecular Plant Pathology》2022,23(8):1075-1090
Sclerotinia sclerotiorum is a pathogenic fungus that infects hundreds of plant species, including many of the world's most important crops. Key features of S. sclerotiorum include its extraordinary host range, preference for dicotyledonous plants, relatively slow evolution, and production of protein effectors that are active in multiple host species. Plant resistance to this pathogen is highly complex, typically involving numerous polymorphisms with infinitesimally small effects, which makes resistance breeding a major challenge. Due to its economic significance, S. sclerotiorum has been subjected to a large amount of molecular and evolutionary research. In this updated pathogen profile, we review the evolutionary and molecular features of S. sclerotiorum and discuss avenues for future research into this important species. 相似文献
117.
Coordinated expression of matrix Gla protein is required during endochondral ossification for chondrocyte survival 总被引:2,自引:0,他引:2 下载免费PDF全文
Matrix Gla protein (MGP) is a 14-kD extracellular matrix protein of the mineral-binding Gla protein family. Studies of MGP-deficient mice suggest that MGP is an inhibitor of extracellular matrix calcification in arteries and the epiphyseal growth plate. In the mammalian growth plate, MGP is expressed by proliferative and late hypertrophic chondrocytes, but not by the intervening chondrocytes. To investigate the functional significance of this biphasic expression pattern, we used the ATDC5 mouse chondrogenic cell line. We found that after induction of the cell line with insulin, the differentiating chondrocytes express MGP in a stage-specific biphasic manner as in vivo. Treatment of the ATDC5 cultures with MGP antiserum during the proliferative phase leads to their apoptosis before maturation, whereas treatment during the hypertrophic phase has no effect on chondrocyte viability or mineralization. After stable transfection of ATDC5 cells with inducible sense or antisense MGP cDNA constructs, we found that overexpression of MGP in maturing chondrocytes and underexpression of MGP in proliferative and hypertrophic chondrocytes induced apoptosis. However, overexpression of MGP during the hypertrophic phase has no effect on chondrocyte viability, but it does reduce mineralization. This work suggests that coordinated levels of MGP are required for chondrocyte differentiation and matrix mineralization. 相似文献
118.
Garnett Trevor P. Shabala Sergey N. Smethurst Philip J. Newman Ian A. 《Plant and Soil》2001,236(1):55-62
Knowledge of the preferred source of N for Eucalyptus nitens will lead to improved fertiliser management practices in plantations. Ion selective microelectrodes were used non-invasively to measure simultaneously net fluxes of NH4
+, NO3
– and H+ along the tap root of solution-cultured E. nitens. Measurements were conducted in solutions containing 100 m NH4NO3. The pattern of fluxes was such that there was a large influx of NH4
+, a smaller influx of NO3
– and large H+ efflux. The ratio of these fluxes was constant, according to the ratio 3:1:–6 (NH4
+:NO3
–:H+). Within the region 20–60 mm from the root apex of E. nitens seedlings there was spatial and temporal variation in fluxes but flux patterns remained constant. Root hair density did not affect fluxes nor did proximity to lateral roots. Variation was less than that found in previous studies of localised root fluxes using similar high-resolution measurement techniques. It was concluded that small-scale spatial variation in fluxes may have confounded previous studies. There were associations between fluxes of all three ions, the strongest associations being between NH4
+ and H+, and NH4
+ and NO3
–. Overall, these results are consistent with NH4
+ being the preferred source N for E. nitens. 相似文献
119.
Single nucleotide polymorphisms (SNPs) in the estrogen receptor gene and breast cancer susceptibility 总被引:8,自引:0,他引:8
Schubert EL Lee MK Newman B King MC 《The Journal of steroid biochemistry and molecular biology》1999,71(1-2):21-27
In order to evaluate the role of inherited variation in the estrogen receptor (ESR1) gene in human breast cancer, we determined intronic sequences flanking each ESRI exon; identified multiple SNPs and length polymorphisms in the ESR1 coding sequence, splice junctions and regulatory regions; and genotyped families at high risk of breast cancer and population-based breast cancer patients and controls. Of 10 polymorphic sites in ESR1, four are synonymous SNPs, two are nonsynonymous SNPs and four are length polymorphisms; five are novel. No ESR1 polymorphisms were associated with breast cancer, either in the high-risk families or the case-control study. We therefore conclude that inherited genetic variation is not a mechanism by which the estrogen receptor is commonly involved in breast cancer development. 相似文献
120.
Paul F. Agris Marie T. Marchbank Winnell Newman Richard Guenther Phyllis Ingram Jacinda Swallow Piotr Mucha Agnieszka Szyk Piotr Rekowski Elena Peletskaya Susan L. Deutscher 《The protein journal》1999,18(4):425-435
Peptides that bind either U1 small nuclear RNA (U1 snRNA) or the anticodon stem and loop of yeast tRNAPhe (tRNA AC Phe ) were selected from a random-sequence, 15-amino acid bacteriophage display library. An experimental system, including an affinity selection method, was designed to identify primary RNA-binding peptide sequences without bias to known amino acid sequences and without incorporating nonspecific binding of the anionic RNA backbone. Nitrocellulose binding assays were used to evaluate the binding of RNA by peptide-displaying bacteriophage. Amino acid sequences of RNA-binding bacteriophage were determined from the foreign insert DNA sequences, and peptides corresponding to the RNA-binding bacteriophage inserts were chemically synthesized. Peptide affinities for the RNAs (K d ? 0.1–5.0 μM) were analyzed successfully using fluorescence and circular dichroism spectroscopies. These methodologies demonstrate the feasibility of rapidly identifying, isolating, and initiating the analyses of small peptides that bind to RNAs in an effort to define better the chemistry, structure, and function of protein–RNA complexes. 相似文献