全文获取类型
收费全文 | 50833篇 |
免费 | 3719篇 |
国内免费 | 21篇 |
专业分类
54573篇 |
出版年
2024年 | 52篇 |
2023年 | 186篇 |
2022年 | 598篇 |
2021年 | 970篇 |
2020年 | 602篇 |
2019年 | 738篇 |
2018年 | 1117篇 |
2017年 | 974篇 |
2016年 | 1592篇 |
2015年 | 2479篇 |
2014年 | 2851篇 |
2013年 | 3219篇 |
2012年 | 4228篇 |
2011年 | 4035篇 |
2010年 | 2585篇 |
2009年 | 2332篇 |
2008年 | 3244篇 |
2007年 | 3116篇 |
2006年 | 2746篇 |
2005年 | 2524篇 |
2004年 | 2325篇 |
2003年 | 2023篇 |
2002年 | 1739篇 |
2001年 | 1377篇 |
2000年 | 1297篇 |
1999年 | 1034篇 |
1998年 | 423篇 |
1997年 | 370篇 |
1996年 | 268篇 |
1995年 | 229篇 |
1994年 | 226篇 |
1993年 | 181篇 |
1992年 | 357篇 |
1991年 | 321篇 |
1990年 | 289篇 |
1989年 | 246篇 |
1988年 | 197篇 |
1987年 | 178篇 |
1986年 | 148篇 |
1985年 | 120篇 |
1984年 | 91篇 |
1983年 | 96篇 |
1982年 | 74篇 |
1981年 | 67篇 |
1980年 | 63篇 |
1979年 | 79篇 |
1978年 | 58篇 |
1977年 | 55篇 |
1974年 | 67篇 |
1973年 | 48篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Pseudomonas putida E41 was isolated from oil-contaminated soil and showed its ability to grow on ethyl-benzene as the sole carbon and energy
source. Moreover, P. putida E41 show the activity of biodegradation of ethylbenzene in the batch culture. E41 showed high efficiency of biodegradation
of ethylbenzene with the optimum conditions (a cell concentration of 0.1 g wet cell weight/L, pH 7.0, 25°C, and ethylbenzene
concentration of 50 mg/L) from the results of the batch culture. The maximum degradation rate and specific growth rate (μmax) under the optimum conditions were 0.19+0.03 mg/mg-DCW (Dry Cell Weight)/h and 0.87+0.13 h−1, respectively. Benzene, toluene and ethylbenzene were degraded when these compounds were provided together; however, xylene
isomers persisted during degradation by P. putida E41. When using a bioreactor batch system with a binary culture with P. putida BJ10, which was isolated previously in our lab, the degradation rate for benzene and toluene was improved in BTE mixed medium
(each initial concentration: 50 mg/L). Almost all of the BTE was degraded within 4 h and 70–80% of m-, p-, and o-xylenes within 11 h in a BTEX mixture (initial concentration: 50 mg/L each). In summary, we found a valuable new strain of
P. putida, determined the optimal degradation conditions for this isolate and tested a mixed culture of E41 and BJ10 for its ability
to degrade a common sample of mixed contaminants containing benzene, toluene, and xylene. 相似文献
992.
Yeo Dae Yoon Eun Sook Lee Jong Pil Park Mee Ree Kim Jun Won Lee Tae Hoon Kim Min Kyun Na Jin Hee Kim 《Biotechnology and Bioprocess Engineering》2011,16(6):1099-1105
Hizikia fusiforme is a commonly used food that possesses potent anti-bacterial, anti-fungal, and anti-inflammatory activities. The immunostimulatory
activities of aqueous extract of Hizikia fusiforme (HFAE) in RAW 264.7 macrophages and whole spleen cells were investigated. HFAE activated RAW 264.7 macrophages to produce
cytokines such as nitric oxide (NO), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin-6 (IL-6) in
a dose-dependent manner. In addition, HFAE induced the mRNA expression of TNF-α, IL-1β, and IL-6 in RAW 264.7 macrophages.
Moreover, HFAE stimulated proliferation of whole spleen cells and reference mitogen. Taken together, the results demonstrate
that HFAE potently activates the immune function by regulating NO, TNF-α, IL-1β, and IL-6 in RAW 264.7 macrophage and promoting
spleen cell proliferation. 相似文献
993.
Saccharomyces cerevisiae strains tolerant to ethanol and heat stresses are important for industrial ethanol production. In this study, five strains
(Tn 1–5) tolerant to up to 15% ethanol were isolated by screening a transposon-mediated mutant library. Two of them displayed tolerance
to heat (42 °C). The determination of transposon insertion sites and Northern blot analysis identified seven putative genes
(CMP2, IMD4, SSK2, PPG1, DLD3, PAM1, and MSN2) and revealed simultaneous down-regulations of CMP2 and IMD4, and SSK2 and PPG1, down-regulation of DLD3, and disruptions of the open reading frame of PAM1 and MSN2, indicating that ethanol and/or heat tolerance can be conferred. Knockout mutants of these seven individual genes were ethanol
tolerant and three of them (SSK2, PPG1, and PAM1) were tolerant to heat. Such tolerant phenotypes reverted to sensitive phenotypes by the autologous or overexpression of
each gene. Five transposon mutants showed higher ethanol production and grew faster than the control strain when cultured
in rich media containing 30% glucose and initial 6% ethanol at 30 °C. Of those, two thermotolerant transposon mutants (Tn
2 and Tn 3) exhibited significantly enhanced growth and ethanol production compared to the control at 42 °C. The genes identified in
this study may provide a basis for the application in developing industrial yeast strains. 相似文献
994.
995.
Yun BY Jun SY Kim NA Yoon BY Piao S Park SH Jeong SH Lee H Ha NC 《Biochemical and biophysical research communications》2011,416(1-2):92-98
Glycoside hydrolase family 4 (GH4) represents an unusual group of glucosidases with a requirement for NAD(+), Mn(2+), and reducing conditions. We found a putative α-glucosidase belonging to GH4 in hyperthermophilic Gram-negative bacterium Thermotoga neapolitana. In this study, we recombinantly expressed the putative α-glycosidase from T. neapolitana, and determined the crystal structure of the protein at a resolution of 2.0? in the presence of Mn(2+) but in the absence of NAD(+). The structure showed the dimeric assembly and the Mn(2+) coordination that other GH4 enzymes share. In comparison, we observed structural changes in T. neapolitana α-glucosidase by the binding of NAD(+), which also increased the thermostability. Numerous arginine-mediated salt-bridges were observed in the structure, and we confirmed that the salt bridges correlated with the thermostability of the proteins. Disruption of the salt bridge that linked N-terminal and C-terminal parts at the surface dramatically decreased the thermostability. A mutation that changed the internal salt bridge to a hydrogen bond also decreased the thermostability of the protein. This study will help us to understand the function of the putative glucosidase and the structural features that affect the thermostability of the protein. 相似文献
996.
Being different from anti-phosphotyrosine antibodies, anti-phosphoserine- or anti-phosphothreonine-specific antibodies with high affinity for the detection of serine/threonine kinase substrates are not readily available. Therefore, chemical modification methods were developed for the detection of phosphoserine or threonine in the screening of protein kinase substrates based on β-elimination and Michael addition. We have developed a biotin-based detection probe for identification of the phosphorylated serine or threonine residue. A biotin derivative induced a color reaction using alkaline phosphate-conjugated streptavidin that amplified the signal. It was effective for the detection and separation of the target peptide on the resin. The detection probe was successfully used in identifying PKA substrates from peptide libraries on resin beads. The peptide library was prepared as a ladder-type, such that the active peptides on the colored resin beads were readily sequenced with the truncated peptide fragments by MALDI-TOF/MS analysis after releasing the peptides from the resin bead through photolysis. 相似文献
997.
998.
Molecular cloning and biochemical characterization of a heat-stable type I pullulanase from Thermotoga neapolitana 总被引:1,自引:0,他引:1
Kang J Park KM Choi KH Park CS Kim GE Kim D Cha J 《Enzyme and microbial technology》2011,48(3):260-266
The gene encoding a type I pullulanase from the hyperthermophilic anaerobic bacterium Thermotoga neapolitana (pulA) was cloned in Escherichia coli and sequenced. The pulA gene from T. neapolitana showed 91.5% pairwise amino acid identity with pulA from Thermotoga maritima and contained the four regions conserved in all amylolytic enzymes. pulA encodes a protein of 843 amino acids with a 19-residue signal peptide. The pulA gene was subcloned and overexpressed in E. coli under the control of the T7 promoter. The purified recombinant enzyme (rPulA) produced a 93-kDa protein with pullulanase activity. rPulA was optimally active at pH 5-7 and 80°C and had a half-life of 88 min at 80°C. rPulA hydrolyzed pullulan, producing maltotriose, and hydrolytic activities were also detected with amylopectin, starch, and glycogen, but not with amylose. This substrate specificity is typical of a type I pullulanase. Thin layer chromatography of the reaction products in the reaction with pullulan and aesculin showed that the enzyme had transglycosylation activity. Analysis of the transfer product using NMR and isoamylase treatment revealed it to be α-maltotriosyl-(1,6)-aesculin, suggesting that the enzyme transferred the maltotriosyl residue of pullulan to aesculin by forming α-1,6-glucosidic linkages. Our findings suggest that the pullulanase from T. neapolitana is the first thermostable type I pullulanase which has α-1,6-transferring activity. 相似文献
999.
Hamdan FF Gauthier J Araki Y Lin DT Yoshizawa Y Higashi K Park AR Spiegelman D Dobrzeniecka S Piton A Tomitori H Daoud H Massicotte C Henrion E Diallo O;SD Group Shekarabi M Marineau C Shevell M Maranda B Mitchell G Nadeau A D'Anjou G Vanasse M Srour M Lafrenière RG Drapeau P Lacaille JC Kim E Lee JR Igarashi K Huganir RL Rouleau GA Michaud JL 《American journal of human genetics》2011,(3):1427-316
Little is known about the genetics of nonsyndromic intellectual disability (NSID). We hypothesized that de novo mutations (DNMs) in synaptic genes explain an important fraction of sporadic NSID cases. In order to investigate this possibility, we sequenced 197 genes encoding glutamate receptors and a large subset of their known interacting proteins in 95 sporadic cases of NSID. We found 11 DNMs, including ten potentially deleterious mutations (three nonsense, two splicing, one frameshift, four missense) and one neutral mutation (silent) in eight different genes. Calculation of point-substitution DNM rates per functional and neutral site showed significant excess of functional DNMs compared to neutral ones. De novo truncating and/or splicing mutations in SYNGAP1, STXBP1, and SHANK3 were found in six patients and are likely to be pathogenic. De novo missense mutations were found in KIF1A, GRIN1, CACNG2, and EPB41L1. Functional studies showed that all these missense mutations affect protein function in cell culture systems, suggesting that they may be pathogenic. Sequencing these four genes in 50 additional sporadic cases of NSID identified a second DNM in GRIN1 (c.1679_1681dup/p.Ser560dup). This mutation also affects protein function, consistent with structural predictions. None of these mutations or any other DNMs were identified in these genes in 285 healthy controls. This study highlights the importance of the glutamate receptor complexes in NSID and further supports the role of DNMs in this disorder. 相似文献
1000.
Hyeong-Kyu Jeon Hansol Park Dongmin Lee Seongjun Choe Kyu-Heon Kim Woon-Mok Sohn Keeseon S. Eom 《The Korean journal of parasitology》2016,54(2):181-185
Human sparganosis is a zoonotic disease caused by infection with larval forms (procercoid/plerocercoid) of Spirometra spp. The purpose of this study was to identify Spirometra spp. of infected snakes using a multiplex PCR assay and phylogenetic analysis of mitochondrial DNA sequence data from the spargana of terrestrial snakes obtained from Korea and China. A total of 283 snakes were obtained that included 4 species of Colubridae comprising Rhabdophis tigrinus tigrinus (n=150), Dinodon rufozonatum rufozonatum (n=64), Elaphe davidi (n=2), and Elaphe schrenkii (n=7), and 1 species of Viperidae, Agkistrodon saxatilis (n=60). The snakes were collected from the provinces of Chungbuk, Chungnam, and Gyeongbuk in Korea (n=161), and from China (n=122). The overall infection rate with spargana was 83% (235/283). The highest was recorded for D. rufozonatum rufozonatum (100%), followed by A. saxatilis (85%) and R. tigrinus tigrinus (80%), with a negative result for E. davidi (0%) and E. schrenkii (0%). The sequence identities between the spargana from snakes (n=50) and Spirometra erinaceieuropaei () or S. decipiens ( KJ599680) control specimens were 90.8% and 99.2%, respectively. Pairwise genetic distances between spargana (n=50) and S. decipiens ranged from 0.0080 to 0.0107, while those between spargana and S. erinaceieuropaei ranged from 0.1070 to 0.1096. In this study, all of the 904 spargana analyzed were identified as S. decipiens either by a multiplex PCR assay (n=854) or mitochondrial cox1 sequence analysis (n=50). KJ599679相似文献