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61.
A 100 MWt reactor design has been conceived to support flux level of the order of 1015 n/cm2/s in selected flux trap zones. The physics design considers high enriched metallic alloy fuel in the form of annular plates
placed in a D2O moderator tank in a hexagonal lattice arrangement. By choosing a tight lattice pitch in the central region and double the
lattice pitch in the outer region, it is possible to have both high fast flux and thermal flux trap zones. By design the flux
level in the seed fuel has been kept lower than in the high flux trap zones so that the burning rate of the seed is reduced.
Another important objective of the design is to maximize the time interval of refueling. As against a typical refueling interval
of a few weeks in such high flux reactor cores, it is desired to maximize this period to as much as six months or even one
year. This is possible to achieve by eliminating the conventional control absorbers and replacing them with a suitable amount
of fertile material loading in the reactor. Requisite number of seedless thorium-aluminum alloy plates are placed at regular
lattice locations vacated by seed fuel in alternate fuel layers. It is seen that these thorium plates are capable of acquiring
asymptotic fissile content of 14 g/kg in about 100 days of irradiation at a flux level of 8 × 1014 n/cm2/s. In summary, the core has a relatively higher fast flux in the central region and high thermal flux in the outer region.
The present physics design envisages a flat core excess reactivity for the longest possible cycle length of 6 months to one
year. It is also possible to modify the design for constant subcriticality for about the same period or longer duration by
considering neutron spallation source at the centre and curtailing the power density in the inner core region by shielding
it with a layer of thoria fuel loading.
相似文献
62.
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64.
Distinguishing the types of partial discharge (PD) caused by different insulation defects in gas-insulated switchgear (GIS) is a great challenge in the power industry, and improving the recognition accuracy of the relevant models is one of the key problems. In this paper, a convolutional neural network and long short-term memory (CNN-LSTM) model is proposed, which can effectively extract and utilize the spatiotemporal characteristics of PD input signals. First, the spatial characteristics of higher-level PD signals can be obtained through the CNN network, but because CNN is a deep feedforward neural network, it does not have the ability to process time-series data. The PD voltage signal is related to the time dimension, so LSTM saves and analyzes the previous voltage signal information, realizes the modeling of the time dependence of the data, and improves the accuracy of the PD signal pattern recognition. Finally, the pattern recognition results based on CNN-LSTM are given and compared with those based on other traditional analysis methods. The results show that the pattern recognition rate of this method is the highest, with an average of 97.9%, and its overall accuracy is better than that of other traditional analysis methods. The CNN-LSTM model provides a reliable reference for GIS PD diagnosis. 相似文献
65.
Štefan Varga 《International journal of quantum chemistry》2008,108(9):1518-1527
Density fitting scheme is analyzed for the Coulomb problem in extended systems from the correctness of long‐range behavior point of view. We show that for the correct cancellation of divergent long‐range Coulomb terms it is crucial for the density fitting scheme to reproduce the overlap matrix exactly. It is demonstrated that from all possible fitting metric choices the Coulomb metric is the only one which inherently preserves the overlap matrix for infinite systems with translational periodicity. Moreover, we show that by a small additional effort any non‐Coulomb metric fit can be made overlap‐preserving as well. The problem is analyzed for both ordinary and Poisson basis set choices. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 相似文献
66.
A fluid queue with ON periods arriving according to a Poisson process and having a long-tailed distribution has long range
dependence. As a result, its performance deteriorates. The extent of this performance deterioration depends on a quantity
determined by the average values of the system parameters. In the case when the the performance deterioration is the most
extreme, we quantify it by studying the time until the amount of work in the system causes an overflow of a large buffer.
This turns out to be strongly related to the tail behavior of the increase in the buffer content during a busy period of the
M/G/∞ queue feeding the buffer. A large deviation approach provides a powerful method of studying such tail behavior.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
67.
This paper deals with the selection and evaluation of statistical techniques for use in the modeling and forecasting of water quality time series. The focus is on statistical concepts relevant to the analysis of flows and concentrations. A selection of time series procedures has been used for auditing water quality archival data, including the screening of data sets, correlation and spectrum calculations, and iterative model fitting. A summary is provided of experience with analyzing archival data on the Niagara River and the use of a fractionally differenced model.This paper is the result of a study performed for the International Joint Commission, United States and Canada. The authors gratefully acknowledge the direction and support provided by Dr. Joel L. Fisher. 相似文献
68.
Albert G. Buckley 《Mathematical Programming》1986,36(3):256-275
This work concerns the derivation of formulae for updating quasi-Newton matrices used in algorithms for computing approximate
minima of smooth unconstrained functions. The paper concentrates strictly on the techniques used to derive update formulae.
It demonstrates a technique in which problems of finding matrices in ℝ
n ×n
of minimum Frobenius norm are converted to equivalent problems, using vector representations in ℝ
n2
and ℝ
n(n+1)/2 of these matrices, and then solvingl
2-minimization problems. These problems are more directly dealt with, and indeed, the paper demonstrates how this technique
may be used to handle weighted sparse updates. 相似文献
69.
70.
探索薄壳塑性动力响应问题的分析与数值方法,是当今力学中的重要课题之一。笔者曾给出联合应用拉普拉斯变换和最小二乘法分析梁、板、壳塑性动力响应的方法。本文分别针对承受中载的短壳和长壳问题,给出只用最小二乘法分析其塑性动力响应的方法。 相似文献