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101.
N. Amrani M. -E. Dufour N. Bonneaud F. Lacroute 《Molecular & general genetics : MGG》1996,252(5):552-562
In a search for proteins associated with Rna15p in processing the 3 ends of messenger RNAs, we have looked for suppressors that correct, even partially, the thermosensitive growth defect of therna15-2 mutant. Mutations in a single locus that we namedSSM5, were able to suppress both the thermosensitivity of cell growth and the mRNA 3 processing defect associated with therna15-2 mutation, but only slightly alleviated the thermosensitive growth defect of anrna14-1 mutant. Thessm5-1 mutant is sensitive to hydroxyurea at 37° C, a drug that inhibits DNA synthesis. By screening for complementation of the hydroxyurea-sensitive phenotype we cloned the corresponding wild-type gene and found that it corresponds to the essential geneSTS1 (also namedDBF8). Sts1p has an apparent molecular weight of 30 kDa and was confirmed to be a cytosolic protein by immunofluorescence analysis. Western blot analysis indicates that the thermosensitive mutant strainsrna15-2, rna14-1 andpap1-1 present a very low level of the Rna15p at 37° C. Thessm5-1 mutation restores the level of Rna15p in therna15-2 ssm5-1 double mutant. Use of the two-hybrid system suggests that Sts1p does not interact directly with Rna15p, but may be active as a homodimer. The present data suggest that Sts1p may play a role in the transport of Rna15p from the cytoplasm to the nucleus. 相似文献
102.
103.
鲫鱼视网膜谷氨酸受体和GABA受体在爪蟾卵母细胞中的表达 总被引:1,自引:1,他引:0
我们以两栖类卵母细胞为功能表达系统,通过注射鲫鱼(Carassiuscarassius)视网膜mRNA,利用电压箝及药物灌流手段,系统地研究了鲫鱼视网膜内氨基酸受体的类型和特征,结果如下:(1)Glu受体:KA可以诱发明显的去极化电流,而且Diazoxide能增强KA诱导的反应,这提示鲫鱼视网膜内某些Clu受体是AMPA选择性亚型(AMPA-preferringsubtype)。(2)CABA受体:GABA能诱发一个快速、光滑的内向电流,绝大部分对GABA的反应可被bicuculline所压抑,而GABA_B受体的激动剂baclofen则无任何作用,这提示,鲫鱼视网膜内大部分是GABA_A受体。 相似文献
104.
When deprived of combined nitrogen, aerobically-grown filaments ofAnabaena sp. strain PCC7120 differentiate specialized cells called the heterocysts. The differentiation process is an elaborate and
well orchestrated programme involving sensing of environmental and developmental signals, commitment of cells to development,
gene rearrangements, intricate DNA-protein interactions, and differential expression of several genes. It culminates in a
physiological division of labour between heterocysts, which become the sole sites of aerobic nitrogen fixation, and vegetative
cells, that provide photosynthate to the heterocysts in return for nitrogen supplies. We propose a model, to describe the
chronology of the important events and to explain how cell type-specific differential gene expression is facilitated by DNA-protein
interactions leading to the development of heterocysts and constitution of nitrogen-fixing apparatus inAnabaena. 相似文献
105.
Heleń M. Rothnie 《Plant molecular biology》1996,32(1-2):43-61
Our understanding of how the 3 ends of mRNAs are formed in plants is rudimentary compared to what we know about this process in other eukaryotes. The salient features of plant pre-mRNAs that signal cleavage and polyadenylation remain obscure, and the biochemical mechanism is as yet wholly uncharacterised. Nevertheless, despite the lack of universally conserved cis-acting motifs, a common underlying architecture is emerging from functional analyses of plant poly(A) signals, allowing meaningful comparison with components of poly(A) signals in other eukaryotes. A plant poly(A) signal consists of one or more near-upstream elements (NUE), each directing processing at a poly(A) site a short distance downstream of it, and an extensive far-upstream element (FUE) that enhances processing efficiency at all sites. By analogy with other systems, a model for a plant 3-end processing complex can be proposed. Plant poly(A) polymerases have been isolated and partially characterised. These, together with hints that some processing factors are conserved in different organisms, opens promising avenues toward initial characterisation of the trans-acting factors involved in 3-end formation of mRNAs in higher plants. 相似文献
106.
Ayyanar Manickam Els J. M. Van Damme Kandasamy Kalaiselvi Peter Verhaert Willy J. Peumans 《Physiologia plantarum》1996,97(3):524-530
Until now no 'early-methionine-labelled' (Em) proteins have been reported in the Fabaceae. To check whether a previously isolated low-molecular mass albumin from dry mung bean embryonic axes possibly corresponded to an Em-like protein, the protein was purified, sequenced and its cDNA clone isolated and characterized. N-terminal sequencing of cyanogen bromide cleavage products of the protein revealed homology with previously described Em-like proteins from other species. Analysis of cDNA clones encoding the mung bean Em protein revealed the presence of two classes of Em proteins and confirmed their homology to the previously characterized Em-like proteins. In vivo labelling and northern blot analysis further demonstrated that the mung bean protein is synthesized during early germination of the axes and that abscisic acid (ABA) extends its synthesis. It appears, therefore, that legumes also contain maturation-specific, ABA-responsive Em-like proteins. 相似文献
107.
108.
Physiological aspects of Taxus brevifolia seeds in relation to seed storage characteristics 总被引:1,自引:0,他引:1
Water relations, desiccation tolerance and longevity of Taxus brevifolia (Nutt.) seeds were studied to determine the optimal stage of development and storage conditions for seeds of this species. Seeds equilibrated to a range of relative humidities (RHs) had unusually low water contents which can be accounted for by the high lipid content of gametophyte tissues (71% of the dry mass). Water relations of embryonic tissue were more typical of those reported for other seed species. The water content below which freezing transitions were not observable in the embryo was ca 0.24 g H2 O (g dry weight)−1 (g g−1 ) for all maturity classes studied. Embryos did not achieve significant levels of desiccation tolerance (survival to water contents less than 0.5 g g−1 ) until the latter stages of development when dry matter was maximal. Mature embryos could be dried to 0.025 g g−1 (seed water content of 0.010 g g−1 ) with no loss of viability. Thus, at the latter stages of development, embryo water content could be optimized to avoid both desiccation and freezing damage. Survival of mature seeds declined over a 2-year period when seeds were stored at temperatures between 5 and 35°C and RHs between 14 and 75%, corresponding to seed water contents between 0.015 and 0.07 g g−1 . The deterioration rate was slowest for seeds stored at the lowest RH and temperature. Our data indicate that seeds of Taxus brevifolia show orthodox rather than recalcitrant storage characteristics, but that the optimum water content for storage was extremely low. The results suggest that even if stored at optimal water contents and low temperatures, T. brevifolia seeds will be relatively short lived. The high quantity of lipids or reducing sugars may be contributing factors in the poor storage characteristics. 相似文献
109.
采用地高辛标记生长抑素反意RNA探针经原位杂交和显色后,光学显微镜下观察生长抑素mRNA在大鼠脊髓内的定位。结果显示:脊髓内含有大量呈紫蓝色的生长抑素mRNA阳性神经细胞,岍性磷酸酶反应产生 相似文献
110.
We investigated the effect of flowering time, display size, and local floral density on fruit set in Tolumnia variegata, a pollination-limited orchid that offers no reward to its pollinator(s). During 1990, natural variation in flowering time, display size, and fruit set were monitored in 508 plants at one locality in Puerto Rico. The following season, orchid floral abundance per host tree (Randia aculeata) was manipulated to investigate its effect on fruit set. Four floral abundance treatments were established (700, 500, 300, and 100), each replicated four times. Flowering time was the most important trait affecting fruit set. The proportion of plants setting at least one fruit was significantly high early and late in the season, but low during the flowering peak. Thus, strong disruptive selection differential on flowering phenology was found. Display size had little effect on fruit set. A weak, but significant disruptive selection differential on display size was found. Orchid floral abundance per host tree had a significant effect on fruit set. Early in the season, T. variegata flowers with intermediate number of conspecific flowers exhibited a greater probability of setting fruit than those in host trees with fewer or more flowers. Our results show that flowering phenology may be evolutionarily unstable, possibly a consequence of the deception pollination system. Furthermore, a deception strategy would be relatively unsuccessful in populations where plants are found in either very dense or sparse patches. 相似文献