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991.
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993.
In many apicomplexan parasites the entry of electrons from NADH into the electron transport chain is governed by type II NADH dehydrogenases (NDH2s) instead of a canonical complex I. Toxoplasma gondii expresses two NDH2 isoforms, TgNDH2-I and TgNDH2-II with no indication for stage-specific regulation. We dissected the orientation of both isoforms by using a split GFP assay and a protease protection assay after selective membrane permeabilization. The two approaches revealed that both TgNDH2 isoforms are internal enzymes facing with their active sites to the mitochondrial matrix. Single knockout mutants displayed a decreased replication rate and a reduced mitochondrial membrane potential, which were both more severe in the Tgndh2-II-deleted than in the Tgndh2-I-deleted mutant. Complementation with a myc-tagged, ectopic copy of the deleted gene restored the growth rate and the mitochondrial membrane potential. However, an overexpression of the remaining intact isoform could not restore the phenotype, suggesting that the two TgNDH2 isoforms are non-redundant and possess functional differences. Together, our studies indicate that although TgNDH2-I and TgNDH2-II are individually non-essential, the expression of both internal isoforms is required to maintain the mitochondrial physiology in T. gondii tachyzoites. 相似文献
994.
Kleinschnitz EM Heichlinger A Schirner K Winkler J Latus A Maldener I Wohlleben W Muth G 《Molecular microbiology》2011,79(5):1367-1379
It is still an open question how an intracellular cytoskeleton directs the synthesis of the peptidoglycan exoskeleton. In contrast to MreB of rod-shaped bacteria, which is essential for lateral cell wall synthesis, MreB of Streptomyces coelicolor has a role in sporulation. To study the function of the S. coelicolor mre gene cluster consisting of mreB, mreC, mreD, pbp2 and sfr, we generated non-polar replacement mutants. The individual mutants were viable and growth of substrate mycelium was not affected. However, all mutants produced enlarged spores, which frequently germinated prematurely and were sensitive to heat, high osmolarity and cell wall damaging agents. Protein-protein interaction assays by bacterial two-hybrid analyses indicated that the S. coelicolor Mre proteins form a spore wall synthesizing complex, which closely resembles the lateral wall synthesizing complex of rod-shaped bacteria. Screening of a genomic library identified several novel putative components of this complex. One of them (sco2097) was deleted. The Δsco2097 mutant formed sensitive spores with an aberrant morphology, demonstrating that SCO2097 is a new player in cell morphogenesis of Streptomyces. Our results suggest that all Mre proteins cooperate with the newly identified proteins in the synthesis of the thickened spore wall required to resist detrimental environmental conditions. 相似文献
995.
Markus Lange Wolfgang W. Weisser Martin M. Gossner Esther Kowalski Manfred Türke Fernando Joner Carlos Roberto Fonseca 《Biodiversity and Conservation》2011,20(10):2133-2147
Land use intensification in forests is a main driver of global biodiversity loss. Although historical state of land use differs
between subtropical and temperate zones, gradients of land-use intensities similarly range from unmanaged to very intensively
managed forests. Irrespective of similar land use forces in both climate zones, comparative studies on land use effects are
still rare. Such studies are, however, promising in discovering more general impacts and geographical specifics of land use
intensification. We studied litter-dwelling invertebrates along a gradient of increasing land use intensity in subtropical
forests in Southern Brazil and temperate forests in Central Europe using similar sampling designs. Effects of land use intensity
on the entire community were analyzed on the level of orders and feeding guilds. In both climate zones a similar number of
individuals were caught when standardizes to 100 pitfall trap days, but taxa richness was higher in the subtropics. Moreover,
community composition differed between both climate zones. In both regions, land use intensity did not affect taxa richness,
but invertebrate abundance was affected in opposite ways; while increasing land use intensity resulted in a decrease of invertebrate
abundance in the subtropics, an increase was observed in the temperate zone and this was mostly consistent regarding different
feeding guilds. Management practices should take into account that the effect of land use intensity on biodiversity can differ
drastically among climatic regions. 相似文献
996.
Past studies have suggested a fundamental difference in testosterone concentrations between tropical and northern latitude male birds, with the convention being that males in the tropics express much lower levels of testosterone. However, recent comparative studies have shown that tropical males with a short and synchronous breeding season (i.e. a breeding season typical of northern species) express maximum testosterone levels similar to those of northern latitude birds. Here, we ask the converse: do northern latitude songbirds that express a defining life‐history characteristic typical of the tropics, i.e. year‐round territoriality, have an annual testosterone profile similar to that of tropical songbirds? For the few year‐round territorial species for which data are available, we found that seasonal testosterone profiles and seasonal maxima in plasma testosterone were similar between males of tropical and non‐tropical species. For example, males of both groups expressed seasonal maxima during the period when females were fertile, and testosterone levels at this time were similar. In contrast, this and other studies show that species with seasonal territories typically express maximum testosterone levels earlier in the breeding cycle, when territories are first being established. Taken together, we suggest that specific life‐history traits may play a more important role in determining testosterone profiles of tropical and non‐tropical birds than breeding latitude and encourage further studies to allow for more formal comparisons. 相似文献
997.
Sielaff F Böttcher-Friebertshäuser E Meyer D Saupe SM Volk IM Garten W Steinmetzer T 《Bioorganic & medicinal chemistry letters》2011,21(16):4860-4864
A series of substrate analogue inhibitors of the serine protease HAT, containing a 4-amidinobenzylamide moiety as the P1 residue, was prepared. The most potent compounds possess a basic amino acid in the d-configuration as P3 residue. Whereas inhibitor 4 (Ki 13 nM) containing proline as the P2 residue completely lacks selectivity, incorporation of norvaline leads to a potent inhibitor (15, Ki 15 nM) with improved selectivity for HAT in comparison to the coagulation proteases thrombin and factor Xa or the fibrinolytic plasmin. Selected inhibitors were able to suppress influenza virus replication in a HAT-expressing MDCK cell model. 相似文献
998.
Kuhn-Nentwig L Largiadèr CR Streitberger K Chandru S Baumann T Kämpfer U Schaller J Schürch S Nentwig W 《Insect biochemistry and molecular biology》2011,41(11):891-901
Cupiennius salei single insulin-like growth factor-binding domain protein (SIBD-1), which exhibits an IGFBP N-terminal domain-like profile, was identified in the hemocytes of the spider C. salei. SIBD-1 was purified by RP-HPLC and the sequence determined by a combination of Edman degradation and 5′–3′- RACE PCR. The peptide (8676.08 Da) is composed of 78 amino acids, contains six intrachain disulphide bridges and carries a modified Thr residue at position 2. SIBD-1 mRNA expression was detected by quantitative real-time PCR mainly in hemocytes, but also in the subesophageal nerve mass and muscle. After infection, the SIBD-1 content in the hemocytes decreases and, simultaneously, the temporal SIBD-1 expression seems to be down-regulated. Two further peptides, SIBD-2 and IGFBP-rP1, also exhibiting IGFBP N-terminal domain variants with unknown functions, were identified on cDNA level in spider hemocytes and venom glands. We conclude that SIBD-1 may play an important role in the immune system of spiders. 相似文献
999.
Labroli M Paruch K Dwyer MP Alvarez C Keertikar K Poker C Rossman R Duca JS Fischmann TO Madison V Parry D Davis N Seghezzi W Wiswell D Guzi TJ 《Bioorganic & medicinal chemistry letters》2011,21(1):471-474
Previous efforts by our group have established pyrazolo[1,5-a]pyrimidine as a viable core for the development of potent and selective CDK inhibitors. As part of an effort to utilize the pyrazolo[1,5-a]pyrimidine core as a template for the design and synthesis of potent and selective kinase inhibitors, we focused on a key regulator in the cell cycle progression, CHK1. Continued SAR development of the pyrazolo[1,5-a]pyrimidine core at the C5 and C6 positions, in conjunction with previously disclosed SAR at the C3 and C7 positions, led to the discovery of potent and selective CHK1 inhibitors. 相似文献
1000.