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121.
122.
Kandzia R Stumpe M Berndt E Szalata M Matsui K Feussner I 《Journal of plant physiology》2003,160(7):803-809
Fatty acid hydroperoxide lyase (HPL) is a membrane associated P450 enzyme that cleaves fatty acid hydroperoxides into aldehydes and omega-oxo fatty acids. One of the major products of this reaction is (3Z)-hexenal. It is a constituent of many fresh smelling fruit aromas. For its biotechnological production and because of the lack of structural data on the HPL enzyme family, we investigated the mechanistic reasons for the substrate specificity of HPL by using various structural analogues of HPL substrates. To approach this 13-HPL from Arabidopsis thaliana was cloned and expressed in E. coli utilising a His-Tag expression vector. The fusion protein was purified by affinity chromatography from the E. coli membrane fractions and its pH optimum was detected to be pH 7.2. Then, HPL activity against the respective (9S)- and (13S)-hydroperoxides derived either from linoleic, alpha-linolenic or gamma-linolenic acid, respectively, as well as that against the corresponding methyl esters was analysed. Highest enzyme activity was observed with the (13S)-hydroperoxide of alpha-linolenic acid (13alpha-HPOT) followed by that with its methyl ester. Most interestingly, when the hydroperoxy isomers of gamma-linolenic acid were tested as substrates, 9gamma-HPOT and not 13gamma-HPOT was found to be a better substrate of the enzyme. Taken together from these studies on the substrate specificity it is concluded that At13HPL may not recognise the absolute position of the hydroperoxy group within the substrate, but shows highest activities against substrates with a (1Z4S,5E,7Z)-4-hydroperoxy-1,5,7-triene motif. Thus, At13HPL may not only be used for the production of C6-derived volatiles, but depending on the substrate may be further used for the production of Cg-derived volatiles as well. 相似文献
123.
Tailoring host immune responses to Listeria by manipulation of virulence genes -- the interface between innate and acquired immunity 总被引:2,自引:0,他引:2
Peters C Domann E Darbouche A Chakraborty T Mielke ME 《FEMS immunology and medical microbiology》2003,35(3):243-253
Although attenuated strains of microbial pathogens have triggered vaccine development from its origin, the role of virulence factors in determining host immunity has remained largely unexplored. Using the murine listeriosis model, we investigated whether the induction and expansion of protective and inflammatory T cell responses may be modified by selective manipulation of virulence genes. We intentionally deleted specific genes of Listeria monocytogenes, including those encoding the positive regulatory factor (prfA), hemolysin (hly), the actin nucleator (actA), and phospholipase B (plcB). The resulting strains showed decisive differences in their immunogenic properties. In particular, we identified a double-deletion mutant that retained Listeria's profound ability to induce protective CD8(+) T cells, but that is strongly attenuated and exhibits a significantly reduced ability to induce CD4(+) T cell-mediated inflammation. We conclude that this mutant, L. monocytogenes DeltaactADeltaplcB, is at present the most promising mutant for a bacterial vaccine vector and is able to safely induce potent CD8(+) T cell-mediated immunity. 相似文献
124.
The biotransformation of baccatin VI (1) and 1β-hydroxybaccatin I (2) with the filamentous fungus Aspergillus niger produced four new taxane diterpenoids taxumairol S1 (3), taxumairol T1 (4) and taxumairol S (5), taxumairol T (6), respectively. 1β-Dehydroxybaccatin VI (7) remained unreacted under the same condition. 相似文献
125.
Chakraborty S Bhattacharya S Ghosh S Bera AK Haldar U Pal AK Mukhopadhyay BP Banerjee A 《Protein engineering》2000,13(8):551-555
Several trypsin inhibitor peptides (with 28-32 amino acid residues) belonging to the Cucurbitaceae (LA-1, LA-2, MCTI-I, CMTI-I, CMTI-III, CMTI-IV), characterized by a distinctive tertiary fold with three conserved disulphide bonds and with mostly arginine at their active centre, were modelled using the high-resolution X-ray structure of a homologous inhibitor, MCTI-II, isolated from bitter gourd. All the inhibitors were modelled in both their native and complexed state with the trypsin molecule, keeping the active site the same as was observed in the trypsin-MCTI-II complex, by homology modelling using the InsightII program. The minimized energy profile supported the binding constants (binding behaviour) of the inhibitor-trypsin complexes in the solution state. A difference accessible surface area (DASA) study of the trypsin with and without inhibitors revealed the subsites of trypsin where the inhibitors bind. It revealed that the role of mutation of these peptides through evolution is to modulate their inhibitory function depending on the biological need rather than changing the overall structural folding characteristics which are highly conserved. The minor changes of amino acids in the non-conserved regions do not influence significantly the basic conformational and interactional sequences at the trypsin binding subsites during complex formation. 相似文献
126.
Angiogenesis or the generation of new blood vessel, is an important factor in the growth of a solid tumor. Hence, it becomes a necessary parameter of any kind of therapeutic study. Glutamine is an essential nutrient of tumor tissue and glutamine related therapy involves clearance of circulatory glutamine by glutaminase. Therefore, using different murine solid tumor models, the present study was undertaken to find out whether the S-180 cell glutaminase has any effect on angiogenesis of solid tumor, or not. Result indicates that the purified S-180 cell glutaminase reduces tumor volume and restrict the generation of neo blood vessels. Therefore, it can be concluded that this enzyme may be an effective device against the cancer metastasis. 相似文献
127.
Chakraborty S Mukhopadhyay AK Bhadra RK Ghosh AN Mitra R Shimada T Yamasaki S Faruque SM Takeda Y Colwell RR Nair GB 《Applied and environmental microbiology》2000,66(9):4022-4028
The virulence of a pathogen is dependent on a discrete set of genetic determinants and their well-regulated expression. The ctxAB and tcpA genes are known to play a cardinal role in maintaining virulence in Vibrio cholerae, and these genes are believed to be exclusively associated with clinical strains of O1 and O139 serogroups. In this study, we examined the presence of five virulence genes, including ctxAB and tcpA, as well as toxR and toxT, which are involved in the regulation of virulence, in environmental strains of V. cholerae cultured from three different freshwater lakes and ponds in the eastern part of Calcutta, India. PCR analysis revealed the presence of these virulence genes or their homologues among diverse serotypes and ribotypes of environmental V. cholerae strains. Sequencing of a part of the tcpA gene carried by an environmental strain showed 97.7% homology to the tcpA gene of the classical biotype of V. cholerae O1. Strains carrying the tcpA gene expressed the toxin-coregulated pilus (TCP), demonstrated by both autoagglutination analysis and electron microscopy of the TCP pili. Strains carrying ctxAB genes also produced cholera toxin, determined by monosialoganglioside enzyme-linked immunosorbent assay and by passage in the ileal loops of rabbits. Thus, this study demonstrates the presence and expression of critical virulence genes or their homologues in diverse environmental strains of V. cholerae, which appear to constitute an environmental reservoir of virulence genes, thereby providing new insights into the ecology of V. cholerae. 相似文献
128.
Bhattachary-Chatterjee M Nath Baral R Chatterjee SK Das R Zeytin H Chakraborty M Foon KA 《Cancer immunology, immunotherapy : CII》2000,49(3):133-141
Anti-idiotype (Id) vaccine therapy has been tested and shown to be effective, in several animal models, for triggering the
immune system to induce specific and protective immunity against bacterial, viral and parasitic infections. The administration
of anti-Id antibodies as surrogate tumor-associated antigens (TAA) also represents another potential application of the concept
of the Id network. Limited experience in human trials using anti-Id to stimulate immunity against tumors has shown promising
results. In this “counterpoint” article, we discuss our own findings showing the potential of anti-Id antibody vaccines to
be novel therapeutic approaches to various human cancers and also discuss where anti-Id vaccines may perform better than traditional
multiple-epitope antigen vaccines.
Received: 27 December 1999 / Accepted: 27 January 2000 相似文献
129.
Development and evaluation of a multiplex PCR assay for rapid detection of toxigenic Vibrio cholerae O1 and O139 总被引:7,自引:0,他引:7
130.
Joshua?C.?Snyder Thomas?F.?Pack Lauren?K.?Rochelle Subhasish?K.?Chakraborty Ming?Zhang Andrew?W.?Eaton Yushi?Bai Lauren?A.?Ernst Larry?S.?Barak Alan?S.?Waggoner Marc?G.?CaronEmail author 《BMC biology》2015,13(1):107