全文获取类型
收费全文 | 1320篇 |
免费 | 89篇 |
国内免费 | 1篇 |
出版年
2023年 | 8篇 |
2022年 | 23篇 |
2021年 | 34篇 |
2020年 | 28篇 |
2019年 | 24篇 |
2018年 | 35篇 |
2017年 | 27篇 |
2016年 | 43篇 |
2015年 | 50篇 |
2014年 | 83篇 |
2013年 | 93篇 |
2012年 | 89篇 |
2011年 | 104篇 |
2010年 | 67篇 |
2009年 | 48篇 |
2008年 | 59篇 |
2007年 | 56篇 |
2006年 | 52篇 |
2005年 | 50篇 |
2004年 | 32篇 |
2003年 | 35篇 |
2002年 | 29篇 |
2001年 | 29篇 |
2000年 | 23篇 |
1999年 | 22篇 |
1998年 | 10篇 |
1997年 | 6篇 |
1996年 | 10篇 |
1995年 | 7篇 |
1994年 | 8篇 |
1992年 | 15篇 |
1991年 | 9篇 |
1990年 | 10篇 |
1989年 | 10篇 |
1988年 | 12篇 |
1987年 | 7篇 |
1986年 | 14篇 |
1985年 | 7篇 |
1984年 | 12篇 |
1983年 | 7篇 |
1982年 | 9篇 |
1980年 | 8篇 |
1979年 | 13篇 |
1978年 | 11篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1975年 | 8篇 |
1973年 | 10篇 |
1972年 | 6篇 |
1969年 | 5篇 |
排序方式: 共有1410条查询结果,搜索用时 250 毫秒
111.
Aminopeptidase N (APN) isoforms were identified as candidate receptors for Bacillus thuringiensis Cry toxins from the midgut of several insect species. In this study a partial cDNA encoding aminopeptidase (slfbAPN) was
cloned from fat body of the moth Spodoptera litura. In the deduced amino acid sequence the characteristic metallopeptidase sequences, HEXXHX18E and GAMENWG were conserved but the sequence showed only 33–39% identity to other insect APNs, which were also reported to
be Cry toxin receptors. The presence of a putative GPI anchor signal sequence at the C-terminus indicated that it is a membrane-anchored protein. The slfbAPN expression was restricted to the fat body as suggested
by northern blot analysis of different tissues. Biochemical analyses including immunoblotting, ligand blotting and lectin
blotting, demonstrated that slfbAPN is a membrane-anchored glycoprotein in the fat body and it binds to Cry toxins.
The nucleotide sequence shown here has been submitted to the GenBank sequence data bank and is available under accession number
EF372603. 相似文献
112.
113.
Dutta T Sengupta R Sahoo R Sinha Ray S Bhattacharjee A Ghosh S 《Letters in applied microbiology》2007,44(2):206-211
AIMS: The enzymatic hydrolysis of xylan has potential economic and environment-friendly applications. Therefore, attention is focused here on the discovery of new extremophilic xylanase in order to meet the requirements of industry. METHODS AND RESULTS: An extracellular xylanase was purified from the culture filtrate of P. citrinum grown on wheat bran bed in solid substrate fermentation. Single step purification was achieved using hydrophobic interaction chromatography. The purified enzyme showed a single band on SDS-PAGE with an apparent molecular weight of c. 25 kDa and pI of 3.6. Stimulation of the activity by beta mercaptoethanol, dithiotheritol (DTT) and cysteine was observed. Moderately thermostable xylanase showed optimum activity at 50 degrees C at pH 8.5. CONCLUSION: Xylanase purified from P. citrinum was alkaliphilic and moderately thermostable in nature. SIGNIFICANCE AND IMPACT OF THE STUDY: The present work reports for the first time the purification and characterization of a novel endoglucanase free alkaliphilic xylanase from the alkali tolerant fungus Penicillium citrinum. The alkaliphilicity and moderate thermostability of this xylanase may have potential implications in paper and pulp industries. 相似文献
114.
Aloe vera has wide spread use in health products, and despite several reports on the whole plant and inner gel, little work has been
performed on the leaf exudate. Our aim was to evaluate the in vitro efficacy of Aloe vera leaf exudate (AVL) in leishmaniasis. Irrespective of the disease manifestation, promastigotes from strains responsible for
cutaneous, mucocutaneous, and visceral leishmaniasis were susceptible to AVL and their IC50 ranged from 100 to 180 μg/ml. In axenic amastigotes cultured from a L. donovani strain 2001 responsible for visceral leishmaniasis, the IC50 was 6.0 μg/ml. AVL caused activation of host macrophages evident by an increased release of members of reactive oxygen species
that was attenuated by preincubation with free radical scavengers. Collectively, our data indicates that AVL, via its direct
leishmanicidal activity which can be further enhanced by activation of host macrophages, is an effective antileishmanial agent
meriting further pharmacological investigations. 相似文献
115.
Kaushal DC Kaushal NA Narula A Kumar N Puri SK Dutta S Lanar DE 《Indian journal of biochemistry & biophysics》2007,44(6):429-436
Plasmodium vivax is one of the most widely distributed human malaria parasites and due to drug-resistant strains, its incidence and prevalence has increased, thus an effective vaccine against the parasites is urgently needed. One of the major constraints in developing P. vivax vaccine is the lack of suitable in vivo models for testing the protective efficacy of the vaccine. P. vivax and P. cynomolgi bastianelli are the two closely related malaria parasites and share a similar clinical course of infection in their respective hosts. The merozoite surface protein-1 (MSP-1) of these parasites has found to be protective in a wide range of host-parasite systems. P. vivax MSP-1 is synthesized as 200 kDa polypeptide and processed just prior to merozoite release from the erythrocytes into smaller fragments. The C- terminal 42 kDa cleavage product of MSP-1 (MSP-1(42)) is present on the surface of merozoites and a major candidate for blood stage malaria vaccine. In the present study, we have biochemically and immunologically characterized the soluble and refolded 42 kDa fragment of MSP-1 of P. vivax (PvMSP-1(42)) and P. cynomolgi B (PcMSP-1(42)). SDS-PAGE analysis showed that both soluble and refolded E. coli expressed P. vivax and P. cynomolgi B MSP-1(42) proteins were homogenous in nature. The soluble and refolded MSP-1(42) antigens of both parasites showed high reactivity with protective monkey sera and conformation-specific monoclonal antibodies against P. cynomolgi B and P. vivax MSP-1(42) antigens. Immunization of BALB/c mice with these antigens resulted in the production of high titres of cross-reactive antibodies primarily against the conformational epitopes of MSP-1(42) protein. The immune sera from rhesus monkeys. immunized with soluble and refolded MSP-1(42) antigens of both parasites also showed high titered cross-reactive antibodies against MSP-1(42) conformational epitopes. These results suggested that the soluble and refolded forms of E. coli expressed P. vivax MSP-1(42) antigens were highly immunogenic and thus a viable candidate for vaccine studies. 相似文献
116.
Ray SS Tejero J Wang ZQ Dutta T Bhattacharjee A Regulski M Tully T Ghosh S Stuehr DJ 《Biochemistry》2007,46(42):11857-11864
Although nitric oxide (NO) is important for cell signaling and nonspecific immunity in the fruit fly Drosophila melanogaster, little is known about its single NO synthase (dNOS). We expressed the oxygenase domain of dNOS (dNOSoxy), characterized its spectroscopic, kinetic, and catalytic properties, and interpreted them in light of a global kinetic model for NO synthesis. Single turnover reactions with ferrous dNOSoxy showed it could convert Arg to N'omega-hydroxy-l-arginine (NOHA), or NOHA to citrulline and NO, when it was given 6R-tetrahydrobiopterin and O2. The dNOSoxy catalyzed Arg hydroxylation and NOHA oxidation at rates that matched or exceeded the rates catalyzed by the three mammalian NOSoxy enzymes. Consecutive heme-dioxy, ferric heme-NO, and ferric heme species were observed in the NOHA reaction of dNOSoxy, indicating that its catalytic mechanism is the same as in the mammalian NOS. However, NO dissociation from dNOSoxy was 4 to 9 times faster than that from the mammalian NOS enzymes. In contrast, the dNOSoxy ferrous heme-NO complex was relatively unreactive toward O2 and in this way was equivalent to the mammalian neuronal NOS. Our data show that dNOSoxy has unique settings for the kinetic parameters that determine its NO synthesis. Computer simulations reveal that these unique settings should enable dNOS to be a more efficient and active NO synthase than the mammalian NOS enzymes, which may allow it to function more broadly in cell signaling and immune functions in the fruit fly. 相似文献
117.
T3 (3,3', 5-triiodo-L-thyronine; 20 microg/100 g body weight/day in 0.01 N NaOH, i.p for 1, 3 and 5 days) treatment modulated reduced (GSH) and oxidized (GSSG) glutathione contents along with the activities of its metabolizing enzymes (such as glutathione peroxidase, glutathione reductase and glutathione S-transferase) in the testis of Wistar rats. However, the magnitude and nature of changes in the above biochemical parameters in response to T3 treatment were noticed to be different between mitochondrial and post-mitochondrial fractions. This was accompanied with elevated levels of lipid hydroperoxide and ascorbic acid in the crude homogenate of testis. The level of hydrogen peroxide in the post-mitochondrial fractions of testes did not change on first day, decreased on 3rd day and increased on 5th day of the hormone treatment when compared to respective controls. Nevertheless, its content in mitochondria was significantly elevated in response to all the three durations of the hormone treatment having the highest induction on 3rd day. The changes observed in the levels of GSH and GSSG and its metabolizing enzymes in response to T3 treatment reflect an alteration in the redox state of testis, which may be a causative factor for the impairment of testicular physiology as a consequence of oxidative stress. 相似文献
118.
119.
Effect of feeding Jerusalem artichoke (Helianthus tuberosus) root as prebiotic on nutrient utilization,fecal characteristics and serum metabolite profile of captive Indian leopard (Panthera pardus fusca) fed a meat‐on‐bone diet 下载免费PDF全文
S.K. Pradhan A. Das S.S. Kullu M. Saini A.K. Pattanaik N. Dutta A.K. Sharma 《Zoo biology》2015,34(2):153-162
120.
Samit Kumar Dutta Pedro Serrano Andrew Proudfoot Michael Geralt Bill Pedrini Kurt Wüthrich 《Journal of biomolecular NMR》2015,61(1):47-53
A standard set of three APSY-NMR experiments has been used in daily practice to obtain polypeptide backbone NMR assignments in globular proteins with sizes up to about 150 residues, which had been identified as targets for structure determination by the Joint Center for Structural Genomics (JCSG) under the auspices of the Protein Structure Initiative (PSI). In a representative sample of 30 proteins, initial fully automated data analysis with the software UNIO-MATCH-2014 yielded complete or partial assignments for over 90 % of the residues. For most proteins the APSY data acquisition was completed in less than 30 h. The results of the automated procedure provided a basis for efficient interactive validation and extension to near-completion of the assignments by reference to the same 3D heteronuclear-resolved [1H,1H]-NOESY spectra that were subsequently used for the collection of conformational constraints. High-quality structures were obtained for all 30 proteins, using the J-UNIO protocol, which includes extensive automation of NMR structure determination. 相似文献