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81.
Optimal maintenance scheduling of a gas engine power plant using generalized disjunctive programming 下载免费PDF全文
Pedro M. Castro Ignacio E. Grossmann Patrick Veldhuizen Douglas Esplin 《American Institute of Chemical Engineers》2014,60(6):2083-2097
A new continuous‐time model for long‐term scheduling of a gas engine power plant with parallel units is presented. Gas engines are shut down according to a regular maintenance plan that limits the number of hours spent online. To minimize salary expenditure with skilled labor, a single maintenance team is considered which is unavailable during certain periods of time. Other challenging constraints involve constant minimum and variable maximum power demands. The objective is to maximize the revenue from electricity sales assuming seasonal variations in electricity pricing by reducing idle times and shutdowns in high‐tariff periods. By first developing a generalized disjunctive programming model and then applying both big‐M and hull reformulation techniques, we reduce the burden of finding the appropriate set of mixed‐integer linear constraints. Through the solution of a real‐life problem, we show that the proposed formulations are very efficient computationally, while gaining valuable insights about the system. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2083–2097, 2014 相似文献
82.
Integration of scheduling and control for batch processes using multi‐parametric model predictive control 下载免费PDF全文
Jinjun Zhuge Marianthi G. Ierapetritou 《American Institute of Chemical Engineers》2014,60(9):3169-3183
Integration of scheduling and control results in Mixed Integer Nonlinear Programming (MINLP) which is computationally expensive. The online implementation of integrated scheduling and control requires repetitively solving the resulting MINLP at each time interval. (Zhuge and Ierapetritou, Ind Eng Chem Res. 2012;51:8550–8565) To address the online computation burden, we incorporare multi‐parametric Model Predictive Control (mp‐MPC) in the integration of scheduling and control. The proposed methodology involves the development of an integrated model using continuous‐time event‐point formulation for the scheduling level and the derived constraints from explicit MPC for the control level. Results of case studies of batch processes prove that the proposed approach guarantees efficient computation and thus facilitates the online implementation. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3169–3183, 2014 相似文献
83.
You-Lin Tain Chien-Te Lee Li-Tung Huang 《International journal of molecular sciences》2014,15(12):23255-23268
84.
You-Lin Tain Li-Tung Huang Julie Y. H. Chan 《International journal of molecular sciences》2014,15(10):18484-18495
Melatonin is an endogenously produced indoleamine and secreted by the pineal gland. Melatonin has pleiotropic bioactivities and is involved in epigenetic regulation. Suboptimal conditions during maternal and perinatal phases can elicit epigenetic regulation of genes for nephrogenesis and reset physiological responses to develop programmed hypertension. This review discusses the early utility of melatonin to prevent programmed hypertension in later life by epigenetic regulation in the kidney, with an emphasis on: (1) the role of melatonin in epigenetic regulation; (2) the beneficial effects of melatonin on programmed hypertension; (3) epigenetic regulation of maternal melatonin therapy in different developmental windows of offspring kidneys analyzed by whole-genome RNA next-generation sequencing; and (4) current blocks in the application of melatonin in preventing programmed hypertension. 相似文献
85.
分析各种管道评定标准给出不同裂纹情况相应的评价方法,采用GB/T 19624-2004对壁厚为18mm的X80管段长输管道工程实测裂纹进行简化评定,绘制出失效评定图,得出该管道可以安全运行,并给出了最大容许等效裂纹尺寸。对评定过程中的复杂汁算公式进行Matlab软件编程,使得计算过程程序化,提高计算准确率,降低评定难度。 相似文献
86.
This article develops an improved seismic risk assessment formulation exhibiting both random and bounded uncertainties using a probability and parallelepiped convex set mixed model. Limit thresholds for different types of components are described via a probabilistic model. The distribution parameters of limit thresholds are originally treated by employing a multidimensional parallelepiped convex model, in which marginal intervals are utilised to represent scattering levels for the distribution parameters, while relevant angle are employed to express the correlation between uncertain distribution parameters. The structural responses, i.e., engineering demand parameters (EDPs), are considered as correlated random variables and are assumed to follow a multidimensional lognormal distribution. A performance limit state function, which allows considering the relationship between the EDPs and the corresponding limit thresholds, is employed to reflect the coexistence of both random and parallelepiped convex variables. The limit state function is mapped into the standard parameter space via a transformation technique. Then, the improved seismic risk formulation, characterised through a probability and parallelepiped convex mixed variables, can be derived with the combination of the seismic fragility function and the ground motion hazard curve. The main purpose is to illustrate that the performance limit states should be properly modeled as random and parallelepiped convex mixed variables rather than only random or deterministic quantities. A six-story reinforced concrete building designed according to Chinese codes are used to illustrate the proposed approach for constructing hazard curves. The interstory drift and the peak floor acceleration are the selected EDPs, calculated through incremental dynamic analysis. The results demonstrate that the calculated failure probabilities for different limit states in 50?years are found capable of meeting the requirements of Chinese seismic norms after the proposed seismic risk formulation is adopted. 相似文献
87.
Martine van den Boomen Pieter L. van den Berg A. Rogier M. Wolfert 《Structure and Infrastructure Engineering》2019,15(2):193-205
In the next decades, many public infrastructure assets will reach the end of their life that they were originally designed for. Replacement costs are high, and therefore increasing effort is put into lifetime-extending maintenance, including major overhauls and renovations. A key question is whether the investments in lifetime-extending maintenance justify the postponement of a full replacement. This question becomes more complicated when future life cycle cash flows are non-repeatable. Differential inflation and technological change, including multiple intervention strategies to maintain a desired functionality, cause such non-repeatability. In this case, classic replacement analysis techniques will not suffice in answering this question. Literature demonstrates that case-specific modelling with dynamic or linear programming techniques is required to find economic optimisation. However, such literature primarily addresses replacement interval optimisation of new investments within relative short time horizons, whereas the current research develops a nested dynamic programming (DP) approach for typical ageing infrastructure assets over long service life periods. The model can deal with multiple and various successive intervention strategies and addresses differential inflation and age-related cost increases. Finally, it is shown in an infrastructure case study that this DP approach leads to a better decision in comparison to the application of classical replacement techniques. 相似文献
88.
89.
90.
Mehrdad Soltani
Ross B. Corotis
《Structural Safety》1988,5(4):239-252A systematic design approach based on applying weights to modes of failure is proposed. Representative individual failure modes are identified on the limit state surface using a nonlinear structural analysis program. Modal failure probabilities are computed in load space (in which randomness in structural resistance is included), and linearized around mean plastic moment capacities. Single- and multi-objective formulations with objectives of failure cost and initial cost, and with mean plastic moment capacities of structural members as decision variables are used. An iterative procedure with successively tighter bounds on the decision variables is employed. The procedure is applied to a simple frame for which optimum plastic moment capacities (single-objective case) and a trade-off curve between future (failure) cost and initial cost (multi-objective case) are found. 相似文献