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121.
Brachat S Dietrich FS Voegeli S Zhang Z Stuart L Lerch A Gates K Gaffney T Philippsen P 《Genome biology》2003,4(7):R45
Background
The recently sequenced genome of the filamentous fungus Ashbya gossypii revealed remarkable similarities to that of the budding yeast Saccharomyces cerevisiae both at the level of homology and synteny (conservation of gene order). Thus, it became possible to reinvestigate the S. cerevisiae genome in the syntenic regions leading to an improved annotation. 相似文献122.
Dennis?M?Maddox Anna?Manlapat Penny?Roon Puttur?Prasad Vadivel?Ganapathy Sylvia?B?SmithEmail author 《BMC developmental biology》2003,3(1):6
Background
Folate is essential for cellular proliferation and tissue regeneration. As mammalian cells cannot synthesize folates de novo, tightly regulated cellular uptake processes have evolved to sustain sufficient levels of intracellular tetrahydrofolate cofactors to support biosynthesis of purines, pyrimidines, and some amino acids (serine, methionine). Though reduced-folate carrier (RFC) is one of the major proteins mediating folate transport, knowledge of the developmental expression of RFC is lacking. We utilized in situ hybridization and immunolocalization to determine the developmental distribution of RFC message and protein, respectively. 相似文献123.
Vaughan S 《Alternatives to laboratory animals : ATLA》2003,31(2):207-212
The Animal Welfare Advisory Committee (AWAC) was established in July 1996, to consider the care, welfare and use of animals involved in procedures for defence research purposes at Defence and Evaluation Research Agency (DERA) establishments in the UK. Two of the objectives of AWAC are to examine the broad trends in animal use at DERA establishments, and to implement and audit the application of the Three Rs principle. AWAC's sixth report addressed the period from 31 October 2000 to 28 February 2002. The statistics of animal use within the report are briefly examined, and some of the actions undertaken by defence research establishments to facilitate the application of the Three Rs are highlighted. It is recommended that, if possible (subject to security constraints), figures detailing the severity of the procedures undertaken should be included in future issues of the report, in order to provide a more-detailed account. It is concluded that Defence Science and Technology Laboratory establishments have made a contribution to the Three Rs, and that other establishments may be able to incorporate some of their actions into their own research programmes. There was an overall 36% increase in the number of procedures carried out by defence research establishments between 1995 and 2000, from 8,900 to 12,065. This probably reflects alterations in the research programme, which is, in turn, decided primarily by the Ministry of Defence's customers and the progress made with previous research programmes. It is therefore recommended that the UK Government allocates significantly more financial resources for the development and validation of alternatives, in order to maximise the potential for achieving the Three Rs in defence research, and to complement the existing initiatives within the defence research industry. 相似文献
124.
Increased salt sensitivity secondary to leptin resistance in SHHF rats is mediated by endothelin 总被引:1,自引:0,他引:1
A link between leptin resistance, obesity, and salt sensitivity has been suggested. SHHF/Mcc-fa
cp rats (SHHF) were used to study the effect of gene dosage of a null mutation of the leptin receptor (cp) on salt sensitivity and response to a combined endothelin A and B receptor antagonist (bosentan). Obese (cp/cp), heterozygous (+/cp), and homozygous lean (+/+) male SHHF were fed a low salt diet (0.3% NaCl) for 7 days, followed by a high salt diet (8.0% NaCl) for 7 days. There were no significant differences in systolic blood pressure between genotypes on low salt. In response to high salt, cp/cp had significantly greater systolic pressure than +/cp and +/+. On high salt diet, cp/cp showed a significant increase in 24 h urinary endothelin excretion and increased renal expression of preproendothelin mRNA. There was no effect of high salt diet on renal excretion of nitric oxide (NOx) or on gene expression of endothelial, neuronal, or cytokine-induced nitric oxide synthase isoforms (eNOS, nNOS, iNOS, respectively). Treatment with bosentan prevented the high salt-induced increment in systolic blood pressure in cp/cp. This was associated with a doubling of renal NOx excretion, but without changes in eNOS, nNOS, or iNOS expression. Endothelin receptor antagonism did not normalize systolic pressure in any of the genotypes. Our studies indicate that obesity secondary to leptin resistance (cp/cp) results in increased salt sensitivity that is mediated by endothelin in the SHHF rat. 相似文献
125.
Responses of somatic embryos of sweet potato (Ipomoea batata (L.) Poir., cv. White Star) at different developmental stages to in vitro inoculation with Glomus etunicatum (Becker and Gerdemann) (isolate INVAM FL329) were evaluated. Somatic embryos were grown in glass tubes containing sterilized vermiculite and sand. A layer of natrosol plus White's medium was used as a carrier for arbuscular mycorrhizal (AM) fungal spores. Survival of embryos inoculated with AM fungi was significantly (P < 0.05) greater than that of noninoculated embryos at the rooted-cotyledonary-torpedo and rooted-elongated-torpedo developmental stages. Mycorrhizae significantly (P < 0.05) increased plantlet formation only when inoculation occurred at the rooted-elongated-torpedo developmental stage. The growth stage at which the embryos were inserted into the glass tubes exerted a significant influence upon plantlet formation, and plantlet formation was further enhanced by inoculation with G. etunicatum. Plantlet formation was greatest at the rooted-elongated-torpedo stage. These results demonstrate that inoculation of somatic embryos with AM fungi improves embryo survival and plantlet formation, and could enhance use of somatic embryos as synthetic seeds. 相似文献
126.
P elements of two different subfamilies designated as M- and O-type are thought to have invaded host species in the Drosophila obscura group via horizontal transmission from external sources. Sequence comparisons with P elements isolated from other species suggested that the horizontal invasion by the O-type must have been a rather recent
event, whereas the M-type invasion should have occurred in the more distant past. To trace the phylogenetic history of O-type
elements, additional taxa were screened for the presence of O- and M-type elements using type-specific PCR primers. The phylogeny
deduced from the sequence data of a 927-bp section (14 taxa) indicate that O-type elements have undergone longer periods of
regular vertical transmission in the lineages of the saltans and willistoni groups of Drosophila. However, starting from a species of the D. willistoni group they were transmitted horizontally into other lineages. First the lineage of the D. affinis subgroup was infected, and finally, in a more recent wave of horizontal spread, species of three different genera were invaded
by O-type elements from the D. affinis lineage: Scaptomyza, Lordiphosa, and the sibling species D. bifasciata/D. imaii of the Drosophila obscura subgroup. The O-type elements isolated from these taxa are almost identical (sequence divergence <1%). In contrast, no such
striking similarities are observed among M-type elements. Nevertheless, the sequence phylogeny of M-type elements is also
not in accordance with the phylogeny of their host species, suggesting earlier horizontal transfer events. The results imply
that P elements cross species barriers more frequently than previously thought but require a particular genomic environment and
thus seem to be confined to a rather narrow spectrum of host species. Consequently, different P element types acquired by successive horizontal transmission events often coexist within the same genome.
Received: 15 May 2000 / Accepted: 19 July 2000 相似文献
127.
128.
Birgitta Gläser Frank Grützner Ulrike Willmann Roscoe Stanyon Norbert Arnold Kay Taylor Wolfgang Rietschel Sylvia Zeitler Roland Toder Werner Schempp 《Mammalian genome》1998,9(3):226-231
The three human male specific expressed gene families DAZ, RBM, and TSPY are known to be repetitively clustered in the Y-specific
region of the human Y Chromosome (Chr). RBM and TSPY are Y-specifically conserved in simians, whereas DAZ cannot be detected on the Y chromosomes of New World monkeys. The proximity of SRY to the pseudoautosomal region (PAR) is highly conserved and thus most effectively stabilizes the pseudoautosomal boundary
on the Y (PABY) in simians. In contrast, the non-recombining part of the Y Chrs, including DAZ, RBM, and TSPY, was exposed to species-specific amplifications, diversifications, and rearrangements. Evolutionary fast fixation of any of
these variations was possible as long as they did not interfere with male fertility.
Received: 18 August 1997 / Accepted: 13 November 1997 相似文献
129.
Premature Translation of oskar in Oocytes Lacking the RNA-Binding Protein Bicaudal-C 总被引:1,自引:0,他引:1 下载免费PDF全文
Emma E. Saffman Sylvia Styhler Katherine Rother Weihua Li Stphane Richard Paul Lasko 《Molecular and cellular biology》1998,18(8):4855-4862
Bicaudal-C (Bic-C) is required during Drosophila melanogaster oogenesis for several processes, including anterior-posterior patterning. The gene encodes a protein with five copies of the KH domain, a motif found in a number of RNA-binding proteins. Using antibodies raised against the BIC-C protein, we show that multiple isoforms of the protein exist in ovaries and that the protein, like the RNA, accumulates in the developing oocyte early in oogenesis. BIC-C protein expressed in mammalian cells can bind RNA in vitro, and a point mutation in one of the KH domains that causes a strong Bic-C phenotype weakens this binding. In addition, oskar translation commences prior to posterior localization of oskar RNA in Bic-C− oocytes, indicating that Bic-C may regulate oskar translation during oogenesis. 相似文献
130.
Escherichia coli Mutants Lacking All Possible Combinations of Eight Penicillin Binding Proteins: Viability, Characteristics, and Implications for Peptidoglycan Synthesis 下载免费PDF全文
Sylvia A. Denome Pamela K. Elf Thomas A. Henderson David E. Nelson Kevin D. Young 《Journal of bacteriology》1999,181(13):3981-3993
The penicillin binding proteins (PBPs) synthesize and remodel peptidoglycan, the structural component of the bacterial cell wall. Much is known about the biochemistry of these proteins, but little is known about their biological roles. To better understand the contributions these proteins make to the physiology of Escherichia coli, we constructed 192 mutants from which eight PBP genes were deleted in every possible combination. The genes encoding PBPs 1a, 1b, 4, 5, 6, and 7, AmpC, and AmpH were cloned, and from each gene an internal coding sequence was removed and replaced with a kanamycin resistance cassette flanked by two res sites from plasmid RP4. Deletion of individual genes was accomplished by transferring each interrupted gene onto the chromosome of E. coli via lambda phage transduction and selecting for kanamycin-resistant recombinants. Afterwards, the kanamycin resistance cassette was removed from each mutant strain by supplying ParA resolvase in trans, yielding a strain in which a long segment of the original PBP gene was deleted and replaced by an 8-bp res site. These kanamycin-sensitive mutants were used as recipients in further rounds of replacement mutagenesis, resulting in a set of strains lacking from one to seven PBPs. In addition, the dacD gene was deleted from two septuple mutants, creating strains lacking eight genes. The only deletion combinations not produced were those lacking both PBPs 1a and 1b because such a combination is lethal. Surprisingly, all other deletion mutants were viable even though, at the extreme, 8 of the 12 known PBPs had been eliminated. Furthermore, when both PBPs 2 and 3 were inactivated by the beta-lactams mecillinam and aztreonam, respectively, several mutants did not lyse but continued to grow as enlarged spheres, so that one mutant synthesized osmotically resistant peptidoglycan when only 2 of 12 PBPs (PBPs 1b and 1c) remained active. These results have important implications for current models of peptidoglycan biosynthesis, for understanding the evolution of the bacterial sacculus, and for interpreting results derived by mutating unknown open reading frames in genome projects. In addition, members of the set of PBP mutants will provide excellent starting points for answering fundamental questions about other aspects of cell wall metabolism. 相似文献