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971.
972.
用纤维素酶处理马尾松磨石磨木浆 (SGW) ,在一定酶活剂量作用下 ,能使纸浆的打浆度明显降低 ,而手抄纸的强度几乎不受影响 相似文献
973.
R.F. Spalding Z.K. U S.W. Hyun G.E. Martin M.E. Burbach S.I.I. Yang M. Kim M.E. Exner S.J. Song 《Nutrient Cycling in Agroecosystems》2001,61(3):237-246
Stable isotopes of nitrogen were used to identify sources of nitrate contamination to groundwater on Cheju, a subtropical
island off the southernmost tip of the Korean peninsula. The δ15N ranges of potential animal waste and fertilizer N sources on the island were similar to those previously reported in the
USA, Europe, and Africa. A total of 108 soil pore water samples were collected between January and October 1998 from fertilized
soils below soybean fields and citrus groves. Low concentrations of nitrate below fertilized soybean fields indicated that
it is highly unlikely that these fields contribute significant N to the groundwater problem on Cheju. The low average δ15N value of +1.9 ± 2.1‰ in pore-water nitrate and the even lower δ15N values after the fertilizer flush suggest that low levels of mineralized N are released from the bean roots or nodules.
Located in the western region, the bean fields received less rainfall than the citrus groves in the southern region. Pore-water
below citrus trees contained considerably higher nitrate levels, and the δ15N values became cyclically enriched after the initial fertilizer flush. Although denitrification can be expected in warm,
wet soils high in organic-C content in the southern region of Cheju, it was not supported by pore-water or groundwater chemistry.
Isotopic enrichment in soil pore-water is caused primarily by volatilization of ammonium-based fertilizers. Since isotopic
fractionation in the soils did not exceed +4‰, source identification was possible. The dominant sources of nitrate contamination
to Cheju groundwater were identified as commercial N-fertilizer applications to citrus, and, in the Seogwipo municipality,
human or animal wastes. 相似文献
974.
通过对纤维缠绕机的结构特性和工作原理的概述,发现目前国内纤维缠绕机存在的问题和不足,然后根据实际生产需要在建模软件Creo中对气瓶纤维缠绕机自动挂纱机构进行设计与装配。利用MECH/PRO接口将挂纱机构模型导入ADAMS中,并对其进行了挂纱运动仿真,对几种常见型号的气瓶芯模进行模拟挂纱,获得了机构的运动特性。研究结果表明,所设计的纤维缠绕机自动挂纱机构满足多种尺寸的芯模挂纱设计要求,对解决目前国内纤维缠绕机存在自动化程度不高的问题有一定的指导意义。 相似文献
975.
Annabel Prause 《Sequential Analysis》2017,36(2):151-178
We study detection methods for multivariable signals under dependent noise. The main focus is on three-dimensional signals; that is, on signals in the space–time domain. Examples for such signals are multifaceted. They include geographic and climatic data as well as image data that are observed over a fixed time horizon. We assume that the signal is observed as a finite block of noisy samples whereby we are interested in detecting changes from a given reference signal. Our detector statistic is based on a sequential partial sum process, related to classical signal decomposition and reconstruction approaches applied to the sampled signal. We show that this detector process converges weakly under the no change null hypothesis that the signal coincides with the reference signal, provided that the spatial–temporal partial sum process associated with the random field of the noise terms disturbing the sampled signal converges to a Brownian motion. More generally, we also establish the limiting distribution under a wide class of local alternatives that allows for smooth as well as discontinuous changes. Our results also cover extensions to the case in which the reference signal is unknown. We conclude with an extensive simulation study of the detection algorithm. 相似文献
976.
977.
ABSTRACT This paper presents a unified model for simulation of cocurrent and countercurrent dispersion-type dryers. The main industrial applications are to pneumatic conveying (flash) dryers and cascading (direct) rotary dryers. The basic model is a one-dimensional incremental (stepwise) simulation, which has been developed over a number of years Equations for particle motion, heat and mass transfer, heat and mass balances and local gas conditions are solved simultaneously over a small increment along the dryer. All workers have previously had considerable difficulty in obtaining a good fit between simulations and actual results from pilot-plants or large-scale industrial dryers. A new “fitting mode” calculation overcomes this by identifying the parameters which need to be adjusted, concentrating on those which cannot be measured accurately. Excellent agreement has been obtained between the model and experimental data by this method. The paper also presents revised formulations for particle motion and heat transfer in rotary dryers. The model has been incorporated into two computer programs for flash and rotary dryers respectively, and results from the former are shown for a case study. 相似文献
978.
Abstract We solve explicitly a Bayesian sequential estimation problem for the drift parameter μ of a fractional Brownian motion under the assumptions that a prior density of μ is Gaussian and that a penalty function is quadratic or Dirac-delta. The optimal stopping time for this case is deterministic. 相似文献
979.
Mirza Trokić 《时间序列分析杂志》2013,34(5):591-601
Regulated (bounded) integrated time series are of significant practical importance and a recent development in the time series literature. Although regulated integrated series are characterized by asymptotic distributions that differ substantially from their unregulated counterparts, most inferential exercises continue to be performed with complete disregard for this potential feature of time series data. To date, only Cavaliere (2005) and Cavaliere and Xu (2011) have attempted to develop a theory for regulated integrated time series, particularly in the context of unit root testing. Unfortunately, no such theory has been developed for regulated fractionally integrated series, which are particularly important in financial time series and also in some unit root testing literature. This article achieves just this: it establishes a framework for regulated fractionally integrated processes and develops their functional central limit distributions. In addition, this article presents some simulation evidence and discusses several algorithms for obtaining the limiting distributions for these processes. 相似文献
980.
This work is focused on the numerical solution of steady natural convection boundary-layer flow of a nanofluid consisting of a pure fluid with nanoparticles along a permeable vertical plate in the presence of magnetic field, heat generation or absorption, and suction or injection effects. The model used for the nanofluid incorporates the effects of Brownian motion and thermophoresis. The governing boundary-layer equations of the problem are formulated and transformed into a non-similar form. The obtained equations are then solved numerically by an efficient, iterative, tri-diagonal, implicit finite-difference method. Comparisons with previously published work are performed and are found to be in excellent agreement. Representative results for the longitudinal velocity, temperature, and nanoparticle volume fraction profiles as well as the local heat transfer rates for various values of the physical parameters are displayed in both graphical and tabular forms. 相似文献