全文获取类型
收费全文 | 948028篇 |
免费 | 87821篇 |
国内免费 | 1081篇 |
出版年
2018年 | 19975篇 |
2017年 | 18624篇 |
2016年 | 18892篇 |
2015年 | 15797篇 |
2014年 | 18278篇 |
2013年 | 26180篇 |
2012年 | 33476篇 |
2011年 | 42796篇 |
2010年 | 32260篇 |
2009年 | 27508篇 |
2008年 | 36831篇 |
2007年 | 39536篇 |
2006年 | 26561篇 |
2005年 | 26254篇 |
2004年 | 26274篇 |
2003年 | 25373篇 |
2002年 | 24756篇 |
2001年 | 35745篇 |
2000年 | 34987篇 |
1999年 | 28347篇 |
1998年 | 11092篇 |
1997年 | 10969篇 |
1996年 | 10490篇 |
1995年 | 9667篇 |
1994年 | 9343篇 |
1993年 | 9341篇 |
1992年 | 22893篇 |
1991年 | 22456篇 |
1990年 | 21896篇 |
1989年 | 21371篇 |
1988年 | 19587篇 |
1987年 | 18807篇 |
1986年 | 17516篇 |
1985年 | 17468篇 |
1984年 | 14604篇 |
1983年 | 12739篇 |
1982年 | 9891篇 |
1981年 | 9018篇 |
1980年 | 8348篇 |
1979年 | 13385篇 |
1978年 | 10679篇 |
1977年 | 9638篇 |
1976年 | 9255篇 |
1975年 | 10184篇 |
1974年 | 10927篇 |
1973年 | 10756篇 |
1972年 | 10273篇 |
1971年 | 9226篇 |
1970年 | 7662篇 |
1969年 | 7506篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Patrizia Vaccino Heinz-Albert Becker Andrea Brandolini Francesco Salamini Benjamin Kilian 《Molecular genetics and genomics : MGG》2009,281(3):289-300
The celiac disease (CD) is an inflammatory condition characterized by injury to the lining of the small-intestine on exposure
to the gluten of wheat, barley and rye. The involvement of gluten in the CD syndrome has been studied in detail in bread wheat,
where a set of “toxic” and “immunogenic” peptides has been defined. For wheat diploid species, information on CD epitopes
is poor. In the present paper, we have adopted a genomic approach in order to understand the potential CD danger represented
by storage proteins in diploid wheat and sequenced a sufficiently large number of cDNA clones related to storage protein genes
of Triticum monococcum. Four bona fide toxic peptides and 13 immunogenic peptides were found. All the classes of storage proteins were shown to contain harmful
sequences. The major conclusion is that einkorn has the full potential to induce the CD syndrome, as already evident for polyploid
wheats. In addition, a complete overview of the storage protein gene arsenal in T. monococcum is provided, including a full-length HMW x-type sequence and two partial HMW y-type sequences.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
993.
J. M. Fryxell T. Crease A. W. Illius 《Proceedings. Biological sciences / The Royal Society》1999,266(1425):1277
The maintenance of genetic variability in morphological traits that affect fitness is poorly understood. We present a simple Mendelian model of genetic traits affecting foraging efficiency in grazing ungulates, based on a trade-off between rates of energy extraction at low versus high levels of plant abundance. The model suggests that variation in foraging efficiency could be maintained via lottery competition arising as a direct consequence of dynamically unstable interactions between consumers and their food resources. Lottery competition is a plausible mechanism for explaining wide variability in foraging efficiency, such as that documented in unstable Soay sheep populations on the St Kilda archipelago. 相似文献
994.
Temperature affects both the biology and morphology of mosquito vectors. Geometric morphometrics is a useful new tool for capturing and analyzing differences in shape and size in many morphological parameters, including wings. We have used this technique for capturing the differences in the wings of the malaria vector Anopheles superpictus, using cohorts reared at six different constant temperatures (15°, 20°, 25°, 27°, 30°, and 35° C) and also searched for potential correlations with the life tables of the species. We studied wing shape in both male and female adults, using 22 landmarks on the wing in relation to ecological parameters, including the development rate. The ecological zero was calculated as 9.93° C and the thermal constant as 296.34 day‐degrees. The rearing temperature affects egg, larval, and pupal development and also the total time from egg to adult. As rearing temperatures increased, longevity decreased in both sexes. In An. superpictus, Ro value and productivity correlated with the statistically significant gradual deformations in the wing shape related to size in both sexes. These deformations directly linked to differences in immature rearing temperatures. Analysis using PCA and UPGMA phenograms showed that although wings of females became narrower dorsoventrally as the temperature increased, they became broader in males. Comparisons of the wing landmarks indicated the medial part of the wing was most affected by larval rearing temperatures, showing relatively more deformations. Algorithmic values of the life tables were determined in correlation with the results of geometric morphometrics. Comparisons of centroid sizes in the cohorts showed that overall wing size became smaller in both sexes in response to higher rearing temperatures. 相似文献
995.
The elucidation of the multiple signaling cascades coupled to the TSH receptor has offered new approaches in the understanding of the pathogenesis of Graves' disease. Here we review findings showing that immunoglobulins from Graves' patients are heterogeneous, bind to different epitopes and, similarly to TSH, activate different signaling pathways, including adenylyl cyclase, phospholipase C and phospholipase A2. Evidence that the multiplicity of signals correlates with the different manifestations of the disease is also summarized. We believe that the dissection of the molecular mechanisms involved in the pathogenesis of Graves' disease offers the basis for developing novel therapeutical approaches to this disease. 相似文献
996.
997.
Alterations in catalytic activity and virus maturation produced by mutation of the conserved histidine residues of herpes simplex virus type 1 protease. 下载免费PDF全文
Mutant herpes simplex virus type 1 (HSV-1) viruses were constructed to characterize the roles of the conserved histidine residues (H61 and H148) of HSV-1 protease in the regulation of catalytic activity and virus maturation. Viruses containing mutations at H61 (H61V-V711, H61Y-V715, and H61A-V730) were unable to grow on Vero cells. These mutant viruses could process neither Pra to N0 nor ICP-35cd to ICP-35ef. Transmission electron microscopy studies of H61A-V730-infected Vero cells indicated that capsid maturation is arrested at a state characterized by the predominance of large symmetrical arrays of B capsids within the nucleus. Two mutations at H148 (in viruses H148A-V712 and H148E-V728) gave rise to mutant viruses that grew with a small-plaque phenotype; one of the viruses, H148E-V728, was particularly attenuated when grown at a low multiplicity of infection. The rate of processing of Pra to N0 in infected Vero cells increased in the order H148A-V712 < H148E-V728 < parental strain HSV-1-V731. The observation that H148A-V712 processes Pra to N0 and ICP-35cd to ICP-35ef, whereas H61A does not, establishes H61 as the catalytically essential conserved His assuming that HSV-1 protease, like other serine proteases, utilizes an active-site histidine residue in catalysis. Two of the mutations at H148 (viruses H148K-V729 and H148Y-V716) produced nonviable viruses. H148K-V729 processed neither Pra to N0 nor ICP-35cd to ICP-35ef, whereas H148Y-V716 processed Pra to N0 but did not process ICP-35cd to ICP-35ef. The range of phenotypes observed with the H148 mutant viruses suggests that residue 148 of the HSV-1 protease is a determinant of virus growth rate and viability because of its effects on the activity of the protease and/or the role of the protease domain in capsid assembly and DNA packaging. 相似文献
998.
The different banding patterns produced by restriction endonuclease digestion in mitotic chromosomes of the American and European eel 总被引:1,自引:0,他引:1
S. Salvadori † A. M. Deiana E. Coluccia A. Milia ‡ A. Cau 《Journal of fish biology》1997,50(3):668-671
The detection of three classes of C-heterochromatin by in situ restriction endonuclease digestion allowed a karyotype differentiation between the American and the European eel. 相似文献
999.
1000.