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51.
Gibbs JM Park SJ Anderson DR Watson KJ Mirkin CA Nguyen ST 《Journal of the American Chemical Society》2005,127(4):1170-1178
The syntheses of several norbornene block copolymers containing oligonucleotide and ferrocenyl side chains and their use in the electrochemical detection of DNA are described. Two kinds of DNA-containing block copolymers with either ferrocenyl or dibromoferrocenyl groups were prepared via ring-opening metathesis polymerization (ROMP). Based on these two distinct ferrocene derivatives, a triblock copolymer labeling strategy was developed. With this strategy, the identity of DNA target can be determined by the E1/2s of the ferrocenyl moieties and the ratio of peak currents. These polymers exhibit predictable and tailorable electrochemical properties, high DNA duplex stability, and unusually sharp melting transitions, which are highly desirable characteristics for DNA detection applications. Significantly, single-base mismatches could be easily detected using two distinct block copolymers as dual-channel detection probes in an electrochemical DNA detection format. 相似文献
52.
Systems of the type MIMIIIS2 (chalcopyrite)-CdS (wurtzite) where MI = Ag, Cu and MIII = Al, Ga, In were investigated to determine the regions of mutual solid solubility. It was found that the chalcopyrite structure could not tolerate extensive CdS substitution. When MIII was Al or Ga the solubility of MIMIIIS2 in CdS was also very limited. However, when MIII = In (rIn3+ ? rGa3+ > rAl3+), the solubility of MIInS2 in CdS was quite extensive (~50%). These results are consistent with a prior study on systems of the type MIMIIIS2ZnS which indicated that in sulfides, larger cations tend to result in the formation of new quaternary, wurtzite phases. 相似文献
53.
The release of nitric oxide (NO) from polymers has proven to be highly effective at inhibiting platelet adhesion and thus enhancing the blood compatibility of medical implants. Micropatterning techniques were used to design surfaces that release NO while preserving the underlying substrate for other applications (e.g., sensors). Micropatterned NO-releasing substrates based on aminosilane-containing methyltrimethoxysilane sol-gels were prepared and characterized in terms of stability, NO surface flux, and resistance to in vitro platelet adhesion. We have found that surface-localized NO release from substrates modified with sol-gel micropatterns exhibit enhanced blood compatibility relative to controls. 相似文献
54.
55.
Robert G.K. Donald Stephen Skwish R. Allyn Forsyth Jennifer W. Anderson Tanya Zhong Colleen Burns Suzy Lee Xin Meng Lynn LoCastro Lisa Wang Jarantow Jesus Martin Sang Ho Lee Ian Taylor David Robbins Cheryl Malone Liangsu Wang Carlos S. Zamudio Philip J. Youngman John W. Phillips 《Chemistry & biology》2009,16(8):826-836
56.
We critically review concepts of self‐organization and self‐assembly, and extract from this analysis consistent and workable definitions of both concepts that are applicable across many scientific disciplines. In essence, we distinguish self‐organization from self‐assembly on a thermodynamic basis, where self‐organization implies a nonequilibrium process and self‐assembly is reserved for spontaneous processes tending toward equilibrium. This discrimination is consistent with early uses of both terms. © 2008 Wiley Periodicals, Inc. Complexity, 2008. 相似文献
57.
We consider the issue of call center scheduling in an environment where arrivals rates are highly variable, aggregate volumes are uncertain, and the call center is subject to a global service level constraint. This paper is motivated by work with a provider of outsourced technical support services where call volumes exhibit significant variability and uncertainty. The outsourcing contract specifies a Service Level Agreement that must be satisfied over an extended period of a week or month. We formulate the problem as a mixed-integer stochastic program. Our model has two distinctive features. Firstly, we combine the server sizing and staff scheduling steps into a single optimization program. Secondly, we explicitly recognize the uncertainty in period-by-period arrival rates. We show that the stochastic formulation, in general, calculates a higher cost optimal schedule than a model which ignores variability, but that the expected cost of this schedule is lower. We conduct extensive experimentation to compare the solutions of the stochastic program with the deterministic programs, based on mean valued arrivals. We find that, in general, the stochastic model provides a significant reduction in the expected cost of operation. The stochastic model also allows the manager to make informed risk management decisions by evaluating the probability that the Service Level Agreement will be achieved. 相似文献
58.
[reaction: see text] Simple thioesters undergo direct aldol addition to aldehydes in the presence of MgBr(2).OEt(2) and i-Pr(2)NEt using untreated, reagent-grade CH(2)Cl(2) under atmospheric conditions. The reactions proceed extremely rapidly and in excellent yield. 相似文献
59.
Let O be a closed geodesic polygon in S~2 . Maps from O into S~2 are said to satisfy tangent boundary conditions if the edges of O are mapped into the geodesics which contain them. Taking O to be an octant of S 2,we compute the infimum Dirichlet energy E(H) for continuous maps satisfying tangent boundary conditions of arbitrary homotopy type H . The expression for E (H ) involves a topological invariant - the spelling length - associated with the (non-abelian) fundamental group of the n-times punctured two-sphere, π 1 (S 2 ? {s 1 , ··· , s n }, ?). The lower bound for E(H) is obtained from combinatorial group theory arguments, while the upper bound is obtained by constructing explicit representa- tives which, on all but an arbitrarily small subset of O, are alternatively locally conformal or anticonformal. For conformal and anticonformal classes (classes containing wholly con- formal and anticonformal representatives respectively), the expression for E (H ) reduces to a previous result involving the degrees of a set of regular values s 1 , ··· , s n in the target S 2 space. These degrees may be viewed as invariants associated with the abelianization of π 1 (S 2 ? {s 1 , ··· , s n }, *). For nonconformal classes, however, E(H) may be strictly greater than the abelian bound. This stems from the fact that, for nonconformal maps, the number of preimages of certain regular values may necessarily be strictly greater than the absolute value of their degrees.This work is motivated by the theoretical modelling of nematic liquid crystals in confined polyhedral geometries. The results imply new lower and upper bounds for the Dirichlet energy (one-constant Oseen-Frank energy) of reflection-symmetric tangent unit- vector fields in a rectangular prism. 相似文献
60.
Chae PS Gotfryd K Pacyna J Miercke LJ Rasmussen SG Robbins RA Rana RR Loland CJ Kobilka B Stroud R Byrne B Gether U Gellman SH 《Journal of the American Chemical Society》2010,132(47):16750-16752
We describe a new type of synthetic amphiphile that is intended to support biochemical characterization of intrinsic membrane proteins. Members of this new family displayed favorable behavior with four of five membrane proteins tested, and these amphiphiles formed relatively small micelles. 相似文献