全文获取类型
收费全文 | 1372篇 |
免费 | 81篇 |
出版年
2023年 | 4篇 |
2022年 | 10篇 |
2021年 | 21篇 |
2020年 | 17篇 |
2019年 | 17篇 |
2018年 | 23篇 |
2017年 | 13篇 |
2016年 | 32篇 |
2015年 | 64篇 |
2014年 | 58篇 |
2013年 | 116篇 |
2012年 | 129篇 |
2011年 | 104篇 |
2010年 | 62篇 |
2009年 | 55篇 |
2008年 | 92篇 |
2007年 | 92篇 |
2006年 | 83篇 |
2005年 | 76篇 |
2004年 | 66篇 |
2003年 | 56篇 |
2002年 | 57篇 |
2001年 | 28篇 |
2000年 | 15篇 |
1999年 | 17篇 |
1998年 | 22篇 |
1997年 | 11篇 |
1996年 | 6篇 |
1995年 | 12篇 |
1994年 | 5篇 |
1993年 | 11篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1990年 | 7篇 |
1989年 | 9篇 |
1988年 | 7篇 |
1987年 | 3篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1981年 | 4篇 |
1976年 | 2篇 |
1967年 | 2篇 |
1966年 | 2篇 |
1964年 | 1篇 |
1958年 | 1篇 |
1956年 | 1篇 |
1955年 | 1篇 |
1953年 | 1篇 |
排序方式: 共有1453条查询结果,搜索用时 31 毫秒
151.
Six anaerobic thermophilic strains isolated from various spoiled cans including fish soups and cooked meats were characterized using a polyphasic approach. These strains were closely related to Moorella thermoacetica or Moorella thermoautotrophica species. Except the spacer region between the 16S and the 23S rRNA genes, which exhibited two PCR profiles distinguishing both species, the genotypic and phylogenetic analyses grouped these isolates, the type strains, and all sequences of Moorella thermoacetica and Moorella thermoautotrophica species contained in the GenBank database within a unique cluster. Moreover, all 16S rDNA sequences shared two characteristic DNA fragments, which were highly specific of Moorella thermoacetica/Moorella thermoautotrophica strains. However, taken together, the phenotypic, physiological and genotypic methods were conflicting, and did not enable affiliation of the isolates with one or the other species. To our knowledge, this study represents the first report of characterization of Moorella species isolated from spoiled cans. These results and previous work, very strongly argue in favor of questioning the taxonomic status of the two species. 相似文献
152.
153.
154.
DesGroseilliers M Fortin F Lemyre E Lemieux N 《Cytogenetic and genome research》2006,112(1-2):176-179
Sex reversal is characterized by discordance between genetic and phenotypic sex. Most XX males result from an unequal interchange between X and Y chromosomes during paternal meiosis, therefore transferring SRY to the X chromosome, which explains the male development in the presence of an otherwise normal female karyotype. We present here the case of sex reversed SRY+ male twins with several cell lines. They consulted for infertility. The presence of SRY on an X chromosome was demonstrated by FISH. Their respective karyotypes were: 46,X,der(X)t(X;Y)(p22.3;p11.2)[249]/45,X [12]/45,der(X)t(X;Y)(p22.3;p11.2)[11]/47,XX,der(X)t(X;Y) (p22.3;p11.2)[1]/47,X,der(X)t(X;Y)(p22.3;p11.2)x2[1]/50, XX,der(X)t(X;Y)(p22.3;p11.2)x4[1]/46,XX[1] for the first twin (SH-1) and 46,X,der(X)t(X;Y)(p22.3;p11.2)[108]/45,X [3]/47,XX,der(X)t(X;Y)(p22.3;p11.2)[2]/45,der(X)t(X;Y) (p22.3;p11.2)[1]/47,X,der(X)t(X;Y)(p22.3;p11.2)x2[1] for the second twin (SH-2). There are three different types of XX males: 1) with normal genitalia, 2) with genital ambiguity, and 3) XX true hermaphrodites. The phenotype of the twins presented in this report is consistent with what is generally seen in XX SRY+ males: they have normal genitalia. 相似文献
155.
Positive associations between adult trees and understorey species have been explained either by direct or indirect facilitation. We tested both models by comparing the performance of two understorey species with contrasted stress-tolerance abilities Galium odoratum and Deschampsia flexuosa. Individuals of both species were transplanted in the four combinations of two treatments (gap and removal of an herbaceous competitor, Molinia caerulea). Our experiment demonstrated that direct facilitation of adult trees may explain the restricted occurrence of the shade-demanding Galium within closed forest communities. In contrast, the shade-tolerant Deschampsia was subjected to additional competition within the forest, likely because adult trees had a higher negative effect on light availability and a similar negative effect on nitrogen availability within the forest than did Molinia in the gaps. 相似文献
156.
157.
TReP-132 is a novel progesterone receptor coactivator required for the inhibition of breast cancer cell growth and enhancement of differentiation by progesterone 下载免费PDF全文
Gizard F Robillard R Gross B Barbier O Révillion F Peyrat JP Torpier G Hum DW Staels B 《Molecular and cellular biology》2006,26(20):7632-7644
158.
Watt MS Moore JR Façon JP Downes GM Clinton PW Coker G Davis MR Simcock R Parfitt RL Dando J Mason EG Bown HE 《Annals of botany》2006,98(4):765-775
Background and Aims Although density-specific stiffness,E/, (where E is Young's modulus and is wood density) is oftenassumed constant by the elastic similarity model, and in determinationof critical buckling height (Hcrit), few studies have testedthis assumption within species. Here this assumption is testedfor Pinus radiata growing across an environmental gradient,and theory is combined with data to develop a model of Young'smodulus. Methods Analyses use an extensive series of environmentalplots covering the range of climatic and edaphic conditionsover which P. radiata is grown in New Zealand. Reduced majoraxis regression was used to determine scaling exponents betweenloglog plots of Hcrit vs. groundline diameter (D), andE/ vs. D. Path analysis was used to identify significant directand indirect (through stem slenderness) edaphic and climaticinfluences on E. Key Results Density-specific stiffness exhibited 3-foldvariation. As E/ scaled positively with D, the exponent of 0·95between Hcrit and D exceeded the assumed value of 0·67under constant E/. The final path analysis model included meanair temperature in early autumn (Taut) and slenderness as significant(P < 0·05) positive direct influences on E. Tree leafarea index and Taut were indirectly associated with E throughtheir significant (P < 0·05) positive direct relationshipwith stem slenderness. Young's modulus was most sensitive toTaut, followed by stem slenderness then leaf area index, andthe final model explained 76 % of the variance in E. Conclusions The findings suggest that within speciesE/ variation may influence Hcrit and the scaling exponent betweenD and Hcrit so important in assumptions regarding allometricrelationships. The model presented may provide a useful meansof determining variation in E, E/ and Hcrit across environmentalgradients. 相似文献
159.
An exocellular proteinase synthesized by the geophilic dermatophyte Trichophyton vanbreuseghemii has been purified and characterized. The fungus obtained from soil in Iran was cultivated in modified Czapek–Dox liquid medium
containing 0.1% bacteriological peptone and 1% glucose as the nitrogen and carbon sources. Partial purification of the proteinase
was accomplished by (NH4)2SO4 precipitation, followed by ion exchange chromatography. Analysis of the enzyme by SDS-PAGE revealed a single polypeptide
chain with an apparent molecular mass of 37 kDa. Proteinase activity was optimum at pH 8, but remained high in the range of
pH 7–11. Moreover, the partially purified enzyme presented a keratinolytic activity as evidenced by the keratin azure test.
The inhibition profile and the good activity of the enzyme towards the synthetic substrate N-succinyl-Ala-Ala-Pro-Phe-p-nitroanilide suggested that it belonged to the chymotrypsin/subtilisin group of serine proteinases. The keratinolytic properties
of T. vanbreuseghemii suggest that this fungus may be an alternative for the recycling of industrial keratinic wastes. 相似文献
160.
A glutathione S-transferase catalyzes the dehalogenation of inhibitory metabolites of polychlorinated biphenyls 下载免费PDF全文
BphK is a glutathione S-transferase of unclear physiological function that occurs in some bacterial biphenyl catabolic (bph) pathways. We demonstrated that BphK of Burkholderia xenovorans strain LB400 catalyzes the dehalogenation of 3-chloro 2-hydroxy-6-oxo-6-phenyl-2,4-dienoates (HOPDAs), compounds that are produced by the cometabolism of polychlorinated biphenyls (PCBs) by the bph pathway and that inhibit the pathway's hydrolase. A one-column protocol was developed to purify heterologously produced BphK. The purified enzyme had the greatest specificity for 3-Cl HOPDA (kcat/Km, approximately 10(4) M(-1) s(-1)), which it dechlorinated approximately 3 orders of magnitude more efficiently than 4-chlorobenzoate, a previously proposed substrate of BphK. The enzyme also catalyzed the dechlorination of 5-Cl HOPDA and 3,9,11-triCl HOPDA. By contrast, BphK did not detectably transform HOPDA, 4-Cl HOPDA, or chlorinated 2,3-dihydroxybiphenyls. The BphK-catalyzed dehalogenation proceeded via a ternary-complex mechanism and consumed 2 equivalents of glutathione (GSH) (Km for GSH in the presence of 3-Cl HOPDA, approximately 0.1 mM). A reaction mechanism consistent with the enzyme's specificity is proposed. The ability of BphK to dehalogenate inhibitory PCB metabolites supports the hypothesis that this enzyme was recruited to facilitate PCB degradation by the bph pathway. 相似文献