全文获取类型
收费全文 | 237篇 |
免费 | 8篇 |
国内免费 | 4篇 |
专业分类
化学 | 160篇 |
晶体学 | 1篇 |
力学 | 5篇 |
数学 | 26篇 |
物理学 | 34篇 |
综合类 | 23篇 |
出版年
2021年 | 2篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 4篇 |
2014年 | 4篇 |
2013年 | 12篇 |
2012年 | 10篇 |
2011年 | 15篇 |
2010年 | 11篇 |
2009年 | 4篇 |
2008年 | 13篇 |
2007年 | 5篇 |
2006年 | 9篇 |
2005年 | 15篇 |
2004年 | 3篇 |
2003年 | 7篇 |
2002年 | 14篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 6篇 |
1996年 | 15篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 7篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 5篇 |
1980年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1966年 | 1篇 |
1959年 | 1篇 |
1958年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有249条查询结果,搜索用时 15 毫秒
1.
Simon R. Blackburn 《Journal of Combinatorial Theory, Series A》2006,113(7):1572-1581
The paper contains proofs of the following results. For all sufficiently large odd integers n, there exists a set of 2n−1 permutations that pairwise generate the symmetric group Sn. There is no set of 2n−1+1 permutations having this property. For all sufficiently large integers n with n≡2mod4, there exists a set of 2n−2 even permutations that pairwise generate the alternating group An. There is no set of 2n−2+1 permutations having this property. 相似文献
2.
In quasi-steady operation, convection currents in a Bridgmandevice, used for producing a semi-conductor crystal, createinhomogeneities that may make the crystal unusable. It has oftenbeen suggested that additional forces due to rotation or magnetismmight be efficacious in reducing the segregation of the elementsof the alloy. It has been found that, over a wide range of rotationrates, there is no improvement in performance due to rotationabout the vertical axis. However, numerical results that havebeen obtained previously (Lee & Pearlstein, J. Crys. Growth240, 2002) indicate that, when effects of centrifugal buoyancyare introduced, a substantial reduction in segregation is achieved.In the work reported here, by contrast, in which we extend previouslarge-Rayleigh-number asymptotic analysis to include centrifugalbuoyancy, we find no improvement in radial segregation, butrather increasing segregation with increasing rotation rate. 相似文献
3.
4.
We have prepared glucose and cellobiose conjugates at the phenolic 3- and hydroxylic 17-positions of the pure anti-estrogenic compound fulvestrant (ICI 182,780), which has recently been approved in the USA for the treatment of advanced postmenopausal breast cancer. Glycosylation at the 17-position was achieved most effectively using pivaloyl protection of the sugar imidates employed, which we found suppressed the competing transacylation reaction and led to improved yields of the product glycosides. 相似文献
5.
6.
Digrazia Philip M. Blackburn James W. Bienkowski Paul R. Hilton Barry Reed Gregory D. King J. M. Henry Sayler Gary S. 《Applied biochemistry and biotechnology》1990,(1):237-252
An experimental and mathematical method is developed for the microbial systems analysis of polyaromatic hydrocarbon (PAH)-degrading
mixed cultures in PAH-contaminated “town gas” soil systems. Frequency response is the primary experimental and data analysis
tool used to probe the structure of these complicated systems. The objective is to provide a fundamental protocol for evaluating
the performance of specific mixed microbial cultures on specific soil systems by elucidating the salient system variables
and their interactions. Two well-described reactor systems, a constant volume stirred tank reactor (CSTR) and a plug flow
differential volume reactor, are used in order to remove performance effects that are related to reactor type as opposed to
system structure. These two reactor systems are well-defined systems that can be described mathematically and represent the
two extremes of one potentially important system variable, macroscopic mass transfer. The experimental and mathematical structure
of the protocol is described, experimental data is presented, and data analysis is demonstrated for the stripping, sorption,
and biodegradation of napththalene. 相似文献
7.
Kenneth Turnbull Thomas L. Blackburn Daniel T. Esterline 《Journal of heterocyclic chemistry》1990,27(5):1259-1263
Bromination of the sydnone ring of several ortho-substituted N-arylsydnones is reported. Subsequent side-chain modification generally can be achieved without concomitant removal of the 4-bromo protective group. 相似文献
8.
BACKGROUND: Display technologies which allow peptides or proteins to be physically associated with the encoding DNA are central to procedures which involve screening of protein libraries in vitro for new or altered function. Here we describe a new system designed specifically for the display of libraries of diverse, functional proteins which utilises the DNA binding protein nuclear factor kappa B (NF-kappa B) p50 to establish a phenotype-genotype link between the displayed protein and the encoding gene. RESULTS: A range of model fusion proteins to either the amino- or carboxy-terminus of NF-kappa B p50 have been constructed and shown to retain the picomolar affinity and DNA specificity of wild-type NF-kappa B p50. Through use of an optimal combination of binding buffer and DNA target sequence, the half-life of p50-DNA complexes could be increased to over 47 h, enabling the competitive selection of a variety of protein-plasmid complexes with enrichment factors of up to 6000-fold per round. The p50-based plasmid display system was used to enrich a maltose binding protein complex to homogeneity in only three rounds from a binary mixture with a starting ratio of 1:10(8) and to enrich to near homogeneity a single functional protein from a phenotype-genotype linked Escherichia coli genomic library using in vitro functional selections. CONCLUSIONS: A new display technology is described which addresses the challenge of functional protein display. The results demonstrate that plasmid display is sufficiently sensitive to select a functional protein from large libraries and that it therefore represents a useful addition to the repertoire of display technologies. 相似文献
9.
Vissers JP Blackburn RK Moseley MA 《Journal of the American Society for Mass Spectrometry》2002,13(7):760-771
A variable flow "peak trapping" liquid chromatography (LC) interface has been developed for the coupling of nanoscale LC to electrospray ionization mass spectrometry (ESI-MS). The presented peak trapping LC interface allows for the extended analysis time of co-eluting compounds and has been employed for the identification of proteins via tandem mass spectrometry (MS/MS). The variable flow process can be controlled either manually or in a completely automated manner where the mass spectrometer status determines the status of the variable flow interface. When the mass spectrometer operates in MS survey mode, the interface is operated in a so-called "high-flow" mode. Alternatively, the interface is operated in a "low-flow" mode during MS/MS analysis. In the "high-flow" mode of the variable flow process the column flow rate is typically around 200 nL/min, whereas in the "low-flow" mode the column effluent is introduced into the source of the mass spectrometer at 25 nL/min. In addition to the flow reduction during MS/MS analysis, the gradient is paused to preserve the peptide separation on the analytical nanoscale LC column. The performance of the variable flow nanoscale LC/MS/MS interface is demonstrated by the automated analysis of standard peptide mixtures and protein digests utilizing variable flow, data-dependent scanning MS/MS techniques, and automated database searching. 相似文献
10.
Environmental light is the 'zeitgeber' (time-giver) of circadian behaviour. Constant darkness is considered a 'free-running' circadian state. Mammals encounter constant darkness during hibernation. Ablation of the master clock synchronizer, the suprachiasmatic nucleus, abolishes torpor, a hibernation-like state, implicating the circadian clock in this phenomenon. Here we report a mechanism by which constant darkness regulates the gene expression of fat catabolic enzymes in mice. Genes for murine procolipase (mClps) and pancreatic lipase-related protein 2 (mPlrp2) are activated in a circadian manner in peripheral organs during 12 h dark:12 h dark (DD) but not light-dark (LD) cycles. This mechanism is deregulated in circadian-deficient mPer1-/-/mPer2m/m mice. We identified circadian-regulated 5'-AMP, which is elevated in the blood of DD mice, as a key mediator of this response. Synthetic 5'-AMP induced torpor and mClps expression in LD animals. Torpor induced by metabolic stress was associated with elevated 5'-AMP levels in DD mice. Levels of glucose and non-esterified fatty acid in the blood are reversed in DD and LD mice. Induction of mClps expression by 5'-AMP in LD mice was reciprocally linked to blood glucose levels. Our findings uncover a circadian metabolic rhythm in mammals. 相似文献