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991.
B. Hwang J. Kwon M. Lee S.J. Lim S. Jeon S. Kim U. Ham Y.J. Song Y. Kuk 《Current Applied Physics》2013,13(7):1365-1369
It has been known that a good quality h-BN layer can only be grown within a narrow temperature window of 1020–1100 K on a copper substrate. We found that the growth temperature window on Cu(111) surface could be lowered up to 100 K by ionizing and/or exciting borazine precursor gas with an electron-beam. The structures of a hexagonal boron nitride (h-BN) layers grown at various substrate temperatures on a Cu(111) were examined using scanning tunneling microscopy. We found that the grown h-BN film exhibits highly inert behavior with wide bandgap semiconductor characteristics. 相似文献
992.
Dong Eok Kim Ki Hoon YangKyung Won Hwang Young Ho HaMoo Hwan Kim 《International Journal of Multiphase Flow》2011
A new physical model for calculating the liquid film thickness and condensation heat transfer coefficient in a vertical condenser tube is proposed by considering the effects of gravity, liquid viscosity, and vapor flow in the core region of the flow. To estimate the velocity profile in the liquid film, the liquid film was assumed to be in Couette flow forced by the interfacial velocity at the liquid–vapor interface. For simplifying the calculation procedures, the interfacial velocity was estimated by introducing an empirical power-law velocity profile. The resulting film thickness and heat transfer coefficient from the model were compared with the experimental data and the results obtained from the other condensation models. The results demonstrated that the proposed model described the liquid film thinning effect by the vapor shear flow and predicted the condensation heat transfer coefficient from experiments reasonably well. 相似文献
993.
Suk-Geun Hwang 《Linear algebra and its applications》2011,434(2):475-479
A family F of square matrices of the same order is called a quasi-commuting family if (AB-BA)C=C(AB-BA) for all A,B,C∈F where A,B,C need not be distinct. Let fk(x1,x2,…,xp),(k=1,2,…,r), be polynomials in the indeterminates x1,x2,…,xp with coefficients in the complex field C, and let M1,M2,…,Mr be n×n matrices over C which are not necessarily distinct. Let and let δF(x1,x2,…,xp)=detF(x1,x2,…,xp). In this paper, we prove that, for n×n matrices A1,A2,…,Ap over C, if {A1,A2,…,Ap,M1,M2,…,Mr} is a quasi-commuting family, then F(A1,A2,…,Ap)=O implies that δF(A1,A2,…,Ap)=O. 相似文献
994.
Hyung Ju Hwang Alan D. Rendall Juan J. L. Velázquez 《Archive for Rational Mechanics and Analysis》2011,200(1):313-360
The Vlasov–Poisson system describes interacting systems of collisionless particles. For solutions with small initial data
in three dimensions it is known that the spatial density of particles decays as t
−3 at late times. In this paper this statement is refined to show that each derivative of the density which is taken leads to
an extra power of decay, so that in N dimensions for
N \geqq 3{N \geqq 3} the derivative of the density of order k decays as t
−N-k
. An asymptotic formula for the solution at late times is also obtained. 相似文献
995.
Chao-Ming Hwang Miin-Shen Yang Wen-Liang Hung E. Stanley Lee 《Mathematical and Computer Modelling》2011,53(9-10):1788-1797
Similarity measures of type-2 fuzzy sets are used to indicate the similarity degree between type-2 fuzzy sets. Inclusion measures for type-2 fuzzy sets are the degrees to which a type-2 fuzzy set is a subset of another type-2 fuzzy set. The entropy of type-2 fuzzy sets is the measure of fuzziness between type-2 fuzzy sets. Although several similarity, inclusion and entropy measures for type-2 fuzzy sets have been proposed in the literatures, no one has considered the use of the Sugeno integral to define those for type-2 fuzzy sets. In this paper, new similarity, inclusion and entropy measure formulas between type-2 fuzzy sets based on the Sugeno integral are proposed. Several examples are used to present the calculation and to compare these proposed measures with several existing methods for type-2 fuzzy sets. Numerical results show that the proposed measures are more reasonable than existing measures. On the other hand, measuring the similarity between type-2 fuzzy sets is important in clustering for type-2 fuzzy data. We finally use the proposed similarity measure with a robust clustering method for clustering the patterns of type-2 fuzzy sets. 相似文献
996.
Hao-Ming Liang Ce-Kuen Shieh Tzu-Chi Huang Wen-Shyang Hwang Chih-Heng Ke 《Mathematical and Computer Modelling》2011,53(3-4):443-457
According to previous work, the performance of the Distributed Coordination Function (DCF) (i.e., the basic access method of the IEEE 802.11 protocol) is far from optimum due to use of the binary exponential backoff (BEB) scheme as its collision avoidance mechanism. There has been considerable discussion of DCF issues and its performance analysis. However, most schemes assume an ideal channel, which is contrary to realistic wireless environments. In this paper, we present a simple yet pragmatic distributed algorithm, designated the density based access method (DBM), which allows stations to dynamically optimize the network throughput based on run-time measurements of the channel status. Our simulation results demonstrate that the DBM is highly accurate. The performance in terms of throughput and fairness is nearly optimal by use of the proposed scheme. 相似文献
997.
998.
Kaining Shi Russell LowKen-Pin Hwang Shanglian BaoJingfei Ma 《Magnetic resonance imaging》2011,29(2):293-299
The fast spin echo (FSE) triple-echo Dixon (FTED) sequence uses bipolar triple-echo readout during each echo-spacing period of FSE to collect all the images necessary for Dixon water and fat separation in a single scan. In comparison to other FSE implementations of the Dixon technique, the triple echo readout used in FTED incurs minimal deadtime in the pulse sequence design and thus greatly enhances the overall scan efficiency. A potential drawback of FTED is that the time dependence of the gradient moment along the frequency encode direction becomes more complicated than in FSE and flow compensation based on the gradient moment (GM) nulling is difficult to achieve. In this work, the first order GM along the frequency encode direction of FTED was examined and two different methods to minimize the GM were proposed. The first method nulls the GM at all the locations of the refocusing radiofrequency pulses so that the Carr-Purcell Meiboom-Gill condition is always maintained. The second method minimizes the GM of the spin echo component of the FSE signal at the echo locations. The efficacy of both methods in reducing the first order GM and flow-related artefacts was demonstrated both in phantom and in images in vivo. 相似文献
999.
David J. Hwang Bin Xiang Sang-Gil Ryu Oscar Dubon Andrew M. Minor Costas P. Grigoropoulos 《Applied Physics A: Materials Science & Processing》2011,103(2):317-321
A GaN-to-InGaN interface modification by predeposition of an ultrathin In-rich InGaN incomplete layer followed by a thin triangular
InGaN well layer was employed to overcome the negative effects of polarization field on light emission efficiency of InGaN/GaN
quantum wells as well as to improve the crystalline quality by avoidance of a significant strain generation and enhanced surfactant
effect. Further, the interface modification induced energy band structure engineering reduces the spatial separation of electrons
and holes, and thus increases the carrier recombination rate. The improvement in crystalline quality, localized potential
fluctuation, and energy band engineering contribute to the significant increase of green emission of the InGaN/GaN quantum
wells. 相似文献
1000.
Silica layers with different microstructures were prepared by electrospraying. The microstructure of the layers was changed by controlling the viscosity of the precursor solutions in the electrospray deposition. Precursor solutions of low viscosity produced particulated silica layers, exhibiting superhydrophobicity. In contrast, fibrous silica layers exhibiting superhydrophilicity were attained with viscous precursor solutions. In particular, the particulated silica layers showed a good durability and resistance to ultraviolet illumination. The dramatic change in the wettability of silica layers without any chemical treatment is promising in speeding up their use in many fields. 相似文献