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121.
Purification, immobilization and characterization of tannase from Penicillium variable 总被引:1,自引:0,他引:1
Tannase from Penicillium variable IARI 2031 was purified by a two-step purification strategy comprising of ultra-filtration using 100 kDa molecular weight cutoff and gel-filtration using Sephadex G-200. A purification fold of 135 with 91% yield of tannase was obtained. The enzyme has temperature and pH optima of 50 degrees C and 5 degrees C, respectively. However, the functional temperature range is from 25 to 80 degrees C and functional pH range is from 3.0 to 8.0. This tannase could successfully be immobilized on Amberlite IR where it retains about 85% of the initial catalytic activity even after ninth cycle of its use. Based on the Michaelis-Menten constant (Km) of tannase, tannic acid is the best substrate with Km of 32 mM and Vmax of 1.11 micromol ml(-1)min(-1). Tannase is inhibited by phenyl methyl sulphonyl fluoride (PMSF) and N-ethylmaleimide retaining only 28.1% and 19% residual activity indicating that this enzyme belongs to the class of serine hydrolases. Tannase in both crude and crude lyophilized forms is stable for one year retaining more than 60% residual activity. 相似文献
122.
Kumariah Manoharan Thirupathi Karuppanapandian Pritam Bala Sinha Rajendra Prasad 《Journal of Plant Biology》2005,48(4):394-403
We investigated 2,4-D-induced leaf senescence in young mustard seedlings. A set of morphometric, biochemical and molecular
parameters were analyzed to characterize senescence markers. In accordance with earlier reports, chloroplast-membrane degradation
marked the early phase of leaf senescence based on the analysis of the galactolipid fraction. Degradation of grana occurred
earlier to that of the envelope, as revealed by the relative level of their specific galactolipids, namely, monogalactosyl
diglyceride and digalactosyl diglyceride. Phospholipids showed extensive degradation resulting in the accumulation of lyso-derivatives
of major phospholipids and phosphatidic acid (PA) in senescing leaves. Catalase activity was stimulated by 2,4-D and reflected
scavenging of reactive oxygen species. Nuclear DNA degradation, a previously known death signal that represented a point of
no return from progression of senescence, occurred late on the 4th day subsequent to 2,4-D supplementation. AgNO3, an inhibitor of ethylene biosynthesis, inhibited leaf senescence by ca. 54% based on PA content Involvement of 2,4-D, ethylene
and abscisic acid in leaf senescence is discussed in relation to hormonal interplay. 相似文献
123.
BACKGROUND: Filariasis and its consequences are a major health problem in tropical countries, including the Indian subcontinent. Despite its high incidence, it is unusual to find microfilaria in fine needle aspiration cytology (FNAC) smears. We present a case of subcutaneous firm to cystic swelling, aspiration of which revealed a large number of microfilaria. CASE: A 30-year-old man presented with a chain of intermittent, firm swellings in both arms. FNAC of the swellings revealed a large number of 4 microfilariae with associated giant cell reaction and inflammatory cell-like eosinophils. CONCLUSION: Besides the documented usual mode of presentation of filarial infection, it can present in an atypical manner, so careful examination of aspirates from the subcutaneous swellings, especially in filariasis endemic zones, is very important. 相似文献
124.
Versha Rai Antresh Kumar Sneha Sudha Komath Rajendra Prasad 《生物化学与生物物理学报:生物膜》2008,1778(10):2143-2153
Although essentially conserved, the N-terminal nucleotide-binding domain (NBD) of Cdr1p and other fungal transporters has some unique substitutions of amino acids which appear to have functional significance for the drug transporters. We have previously shown that the typical Cys193 in Walker A as well as Trp326 and Asp327 in the Walker B of N-terminal NBD (NBD-512) of Cdr1p has acquired unique roles in ATP binding and hydrolysis. In the present study, we show that due to spatial proximity, fluorescence resonance energy transfer (FRET) takes place between Trp326 of Walker B and MIANS [2-(4-maleimidoanilino) naphthalene-6-sulfonic acid] on Cys193 of Walker A motif. By exploiting FRET, we demonstrate how these critical amino acids are positioned within the nucleotide-binding pocket of NBD-512 to bind and hydrolyze ATP. Our results show that both Mg2+ coordination and nucleotide binding contribute to the formation of the active site. The entry of Mg2+ into the active site causes the first large conformational change that brings Trp326 and Cys193 in close proximity to each other. We also show that besides Trp326, typical Glu238 in the Q-loop also participates in coordination of Mg2+ by NBD-512. A second conformational change is induced when ATP, but not ADP, docks into the pocket. Asn328 does sensing of the γ-phosphate of the substrate in the extended Walker B motif, which is essential for the second conformational change that must necessarily precede ATP hydrolysis. Taken together our results imply that the uniquely placed residues in NBD-512 have acquired critical roles in ATP catalysis, which drives drug extrusion. 相似文献
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126.
The breast and ovarian cancer suppressor protein BRCA2 controls the RAD51 recombinase in reactions that lead to homologous DNA recombination (HDR). BRCA2 binds RAD51 via eight conserved BRC repeat motifs of approximately 35 amino acids, each with a varying capacity to bind RAD51. BRC repeats both promote and inhibit RAD51 assembly on different DNA substrates to regulate HDR, but the structural basis for these functions is unclear. Here, we demarcate two tetrameric clusters of hydrophobic residues in the BRC repeats, interacting with distinct pockets in RAD51, and show that the co-location of both modules within a single BRC repeat is necessary for BRC–RAD51 binding and function. The two modules comprise the sequence FxxA, known to inhibit RAD51 assembly by blocking the oligomerization interface, and a previously unrecognized tetramer with the consensus sequence LFDE, which binds to a RAD51 pocket distinct from this interface. The LFDE motif is essential in BRC repeats for modes of RAD51 binding both permissive and inhibitory to RAD51 oligomerization. Targeted insertion of point mutations in RAD51 that disrupt the LFDE-binding pocket impair its assembly at DNA damage sites in living cells. Our findings suggest a model for the modular architecture of BRC repeats that provides fresh insight into the mechanisms regulating homologous DNA recombination. 相似文献
127.
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129.
Karl Deacon David Onion Rajendra Kumari Susan A. Watson Alan J. Knox 《The Journal of biological chemistry》2012,287(47):39967-39981
130.
Wighart von Koenigswald Kenneth D. Rose Luke T. Holbrook Kishor Kumar Rajendra S. Rana Thierry Smith 《Pal?ontologische Zeitschrift》2018,92(4):671-680
The dentition of Cambaytherium was investigated in terms of dental wear, tooth replacement and enamel microstructure. The postcanine tooth row shows a significant wear gradient, with flattened premolars and anterior molars at a time when the last molars are only little worn. This wear gradient, which is more intensive in Cambaytherium thewissi than in Cambaytherium gracilis, and the resulting flattened occlusal surfaces, may indicate a preference for a durophagous diet. The tooth replacement (known only in C. thewissi) shows an early eruption of the permanent premolars. They are in function before the third molars are fully erupted. During the dominant phase I of the chewing cycle the jaw movement is very steep, almost orthal, with a slight mesiolingual direction and changes into a horizontal movement during phase II. The enamel microstructure shows Hunter-Schreger-bands (HSB) in the inner zone of the enamel. In some teeth the transverse orientation of the HSB is modified into a zig-zag pattern, possibly an additional indicator of a durophagous diet. 相似文献