全文获取类型
收费全文 | 929429篇 |
免费 | 99170篇 |
国内免费 | 1235篇 |
出版年
2018年 | 19288篇 |
2017年 | 18059篇 |
2016年 | 17625篇 |
2015年 | 15313篇 |
2014年 | 17122篇 |
2013年 | 23324篇 |
2012年 | 31607篇 |
2011年 | 40871篇 |
2010年 | 31125篇 |
2009年 | 26699篇 |
2008年 | 34990篇 |
2007年 | 37534篇 |
2006年 | 23583篇 |
2005年 | 23886篇 |
2004年 | 23375篇 |
2003年 | 22711篇 |
2002年 | 21847篇 |
2001年 | 35116篇 |
2000年 | 35389篇 |
1999年 | 28535篇 |
1998年 | 11345篇 |
1997年 | 11812篇 |
1996年 | 11313篇 |
1995年 | 10661篇 |
1994年 | 10547篇 |
1993年 | 10400篇 |
1992年 | 24001篇 |
1991年 | 23219篇 |
1990年 | 22807篇 |
1989年 | 22155篇 |
1988年 | 20382篇 |
1987年 | 20036篇 |
1986年 | 18382篇 |
1985年 | 18451篇 |
1984年 | 15425篇 |
1983年 | 13479篇 |
1982年 | 10862篇 |
1981年 | 9669篇 |
1980年 | 9233篇 |
1979年 | 14755篇 |
1978年 | 11903篇 |
1977年 | 10759篇 |
1976年 | 10155篇 |
1975年 | 10948篇 |
1974年 | 11797篇 |
1973年 | 11559篇 |
1972年 | 10850篇 |
1971年 | 10064篇 |
1970年 | 8221篇 |
1969年 | 7767篇 |
排序方式: 共有10000条查询结果,搜索用时 500 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.
Biogeographical change in the tiger, Panthera tigris 总被引:2,自引:0,他引:2
994.
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
995.
Flushing measurements and a resin cast of a burrow inhabited by Sesarma messa and Alpheus cf macklay were taken from a Rhizophoraspp. forest. The burrow had 9 openings and occupied a swamp surface area of 0.64 m2. Passive irrigation of the burrow was investigated by recording change in conductivity of burrow water in a chamber 45 cm below the swamp surface during tidal inundation of the swamp. The chamber was completely flushed within approximately one hour, i.e. by a single tidal event. Burrow morphology was determined by means of resin casting. The investigated burrow was of discrete structure, with an overall depth of 1.2 m and a total volume of 68 l, i.e. ca. 9% of the volume of swamp soil. The below ground surface area of chambers and tunnels was 3.8 m2. The mean and maximum chamber/tunnel diameter was 7 cm and 11 cm respectively. The soil in the close vicinity of the burrow was extensively penetrated by roots, and any two parts of the burrow were located no further than 20 cm away from each other. By reducing diffusion distances within the soil and by being well flushed, the burrows provide an efficient mechanism for removal of excess salt accumulated in the soil around mangrove roots due to exclusion. 相似文献
996.
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
![点击此处可从《Journal of virology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
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
997.
998.
M Lebl E E Sugg G van Binst P Vander Elst D Tourwé J Slaninová V J Hruby 《International journal of peptide and protein research》1987,30(3):318-322
Analogs of deamino-oxytocin and deamino-oxypressin containing a CH2-NH group instead of an amide bond between positions 8 and 9 were synthesized. All tested compounds exhibit significantly lowered biological activities. 相似文献
999.
I. T. Rass 《Biochemistry. Biokhimii?a》2010,75(3):353-366
Glucocorticoid hormones directly or indirectly control virtually all metabolic and physiological processes. Glucocorticoids
are also shown to act on a multitude of genes, enzyme systems, and proinflammatory factors, but for these hormones there is
no representative index of action on metabolism similar to glucose content in blood for insulin. The absence of such an index
prevents the assessment of tissue provision with these hormones under various conditions and seems to be an essential cause
of complications associated with the clinical use of glucocorticoid preparations. Considering specific features of tyrosine
metabolism and data obtained experimentally and on a clinical model (adrenalectomy in rats and substitution therapy in endocrine
disease), blood content of this amino acid seems promising as such an index. Based on comparing results of glucocorticoid
treatment in patients with systemic lupus erythematosus with changes in their blood tyrosine contents, the pharmacological
effect of glucocorticoid preparations is suggested to be mainly due to compensating a relative shortage of these hormones. 相似文献