全文获取类型
收费全文 | 212655篇 |
免费 | 20795篇 |
国内免费 | 12165篇 |
专业分类
电工技术 | 15487篇 |
技术理论 | 8篇 |
综合类 | 21319篇 |
化学工业 | 23377篇 |
金属工艺 | 9244篇 |
机械仪表 | 17321篇 |
建筑科学 | 24667篇 |
矿业工程 | 8440篇 |
能源动力 | 9315篇 |
轻工业 | 16509篇 |
水利工程 | 8712篇 |
石油天然气 | 10318篇 |
武器工业 | 2417篇 |
无线电 | 15006篇 |
一般工业技术 | 23103篇 |
冶金工业 | 9049篇 |
原子能技术 | 3420篇 |
自动化技术 | 27903篇 |
出版年
2024年 | 908篇 |
2023年 | 2808篇 |
2022年 | 5483篇 |
2021年 | 6428篇 |
2020年 | 6760篇 |
2019年 | 5754篇 |
2018年 | 5543篇 |
2017年 | 6851篇 |
2016年 | 7958篇 |
2015年 | 8351篇 |
2014年 | 13374篇 |
2013年 | 13593篇 |
2012年 | 15531篇 |
2011年 | 17100篇 |
2010年 | 12407篇 |
2009年 | 12703篇 |
2008年 | 11877篇 |
2007年 | 14278篇 |
2006年 | 12531篇 |
2005年 | 10480篇 |
2004年 | 8909篇 |
2003年 | 7627篇 |
2002年 | 6285篇 |
2001年 | 5099篇 |
2000年 | 4458篇 |
1999年 | 3660篇 |
1998年 | 3109篇 |
1997年 | 2676篇 |
1996年 | 2212篇 |
1995年 | 1836篇 |
1994年 | 1640篇 |
1993年 | 1254篇 |
1992年 | 1118篇 |
1991年 | 845篇 |
1990年 | 713篇 |
1989年 | 599篇 |
1988年 | 493篇 |
1987年 | 331篇 |
1986年 | 273篇 |
1985年 | 246篇 |
1984年 | 286篇 |
1983年 | 261篇 |
1982年 | 214篇 |
1981年 | 107篇 |
1980年 | 110篇 |
1979年 | 86篇 |
1978年 | 55篇 |
1977年 | 49篇 |
1976年 | 44篇 |
1959年 | 38篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Alexander Vikhansky 《Chemical engineering science》2006,61(15):4966-4972
We consider two stochastic simulation algorithms for the calculation of parametric derivatives of solutions of a population balance equation, namely, forward and adjoint sensitivity methods. The dispersed system is approximated by an N-particle stochastic weighted ensemble. The infinitesimal deviations of the solution are accounted for through infinitesimal deviation of the statistical weights that are recalculated at each coagulation. In the forward method these deviations of the statistical weights immediately give parametric derivatives of the solution. In the second method the deviations of the statistical weights are used to calculate a finite-mode approximation of the linearized version of the population balance equation. The linearized equation allows for the calculation of the eigenmodes and eigenvalues of the process, while the parametric derivatives of the solution are given by a Lagrange formalism. 相似文献
992.
A new functional perturbation method (FPM) for calculating the probabilistic response of stochastically heterogeneous, linear elastic structures is developed. The method is based on treating the governing differential operator as well as the unknown displacement function as a functional of material modulus field. By executing a functional perturbation around the homogeneous case, a set of successive differential equations is obtained and solved, from which the average and variance of any local parameter (displacements, stresses, strains) can be found. For a linear problem, the equations to be solved in each approximation order differ from the one for the homogeneous case by a pseudo external loading (right hand side) part only. Thus, only the Green function for the homogeneous case is needed for an analytical solution of the corresponding heterogeneous problem. A one dimensional stochastically heterogeneous rod embedded in a uniform shear resistant elastic medium is solved as an example. The statistical variance of displacements and stresses are found analytically, including the edge regions. Morphological (grain size) and material (modulus) effects on the stochastic response are demonstrated. The above results are essential for estimating the stochastic features of local stress concentrations, which are the source for many strength-related macro properties of materials. Extensive usage of generalized functions (Dirac operator and its derivatives) is needed for the analysis. 相似文献
993.
Sarrazin Jean-Christophe; Giraudo Marie-Dominique; Pailhous Jean; Bootsma Reinoud J. 《Canadian Metallurgical Quarterly》2004,30(3):411
In 3 experiments, the authors studied the organization of spatiotemporal information in memory. Stimuli consisted of configurations of dots, presented sequentially. The stimuli were either proportional, with interdot distances corresponding to interdot durations, or not proportional, with interdol distances not corresponding to interdot durations. After a learning phase, participants reproduced the spatial (Experiment 1), temporal (Experiment 2), or spatial and temporal (Experiment 3) characteristics of the target 60 times in succession. In the nonproportional conditions, effects of variable interdot durations or distances on the reproduction of, respectively, constant distances (tau effect) or durations (kappa effect) were observed, whereas no such effects were observed when variable distances or durations were to be produced. Tau and kappa effects influenced the accuracy but not the variability of responses. The results are discussed in light of the distinction between properties of the stabilized mental image and the process of stabilization. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
994.
雷康儿 《有色冶金设计与研究》2004,25(2):36-38,41
深圳某银行办公楼的深基坑支护采用了土钉支护,不但保证了施工质量,而且缩短了工期,减少了投资,以此工程为例介绍了土钉支护的土力学参数计算、结构设计、施工方案、技术措施和取得的显著效果。 相似文献
995.
996.
Excessive intermetallic compound (IMC) growth in solder joints will significantly decrease the reliability of the joints.
IMC growth is known to be influenced by numerous factors during the component fabrication process and in service. It is reported
that, other than temperature and holding time, stress can also influence the IMC growth behavior. However, no existing method
can be used to study the effect of stress state on IMC growth in a controlled manner. This paper presents a novel method to
study the effect of stress on interfacial IMC growth between Sn-Ag-Cu solder and a Cu substrate coated with electroless Ni
immersion Au (ENIG). A C-ring was used and in-plane bending induced tensile and compressive stresses were applied by tightening
the C-ring. Results revealed that in-plane compressive stress led to faster IMC growth as compared with in-plane tensile stress. 相似文献
997.
998.
999.
Pipe piles can be classified as either closed- or open-ended piles. In the present paper, the load capacity of both closed- and open-ended piles is related to cone penetration resistance qc through an experimental program using calibration chamber model pile load tests and field pile load tests. A total of 36 calibration chamber pile load tests and two full-scale field pile load tests were analyzed. All the test piles were instrumented for separate measurement of each component of pile load capacity. Based on the test results, the normalized base resistance qb/qc was obtained as a function of the relative density DR for closed-ended piles, and of both the relative density DR and the incremental filling ratio (IFR) for open-ended piles. A relationship between the IFR and the relative density DR is proposed as a function of the pile diameter and driving depth. The relationship between IFR and DR allows the estimation of IFR and thus of the pile load capacity of open-ended piles at the design stage, before pile driving operations. 相似文献
1000.
抗生素后效应系指细菌与抗生素短暂接触后在抗生素被清除的情况下细菌生长仍受抑制的现象。本文对在临床应用中高度重视抗生素后效应的意义和方法作了阐述。 相似文献