全文获取类型
收费全文 | 2907篇 |
免费 | 515篇 |
国内免费 | 344篇 |
专业分类
电工技术 | 222篇 |
综合类 | 537篇 |
化学工业 | 100篇 |
金属工艺 | 67篇 |
机械仪表 | 216篇 |
建筑科学 | 268篇 |
矿业工程 | 64篇 |
能源动力 | 98篇 |
轻工业 | 96篇 |
水利工程 | 111篇 |
石油天然气 | 70篇 |
武器工业 | 59篇 |
无线电 | 391篇 |
一般工业技术 | 295篇 |
冶金工业 | 170篇 |
原子能技术 | 18篇 |
自动化技术 | 984篇 |
出版年
2024年 | 23篇 |
2023年 | 64篇 |
2022年 | 90篇 |
2021年 | 118篇 |
2020年 | 119篇 |
2019年 | 119篇 |
2018年 | 122篇 |
2017年 | 160篇 |
2016年 | 152篇 |
2015年 | 143篇 |
2014年 | 200篇 |
2013年 | 216篇 |
2012年 | 222篇 |
2011年 | 195篇 |
2010年 | 181篇 |
2009年 | 159篇 |
2008年 | 151篇 |
2007年 | 204篇 |
2006年 | 153篇 |
2005年 | 140篇 |
2004年 | 121篇 |
2003年 | 111篇 |
2002年 | 100篇 |
2001年 | 78篇 |
2000年 | 76篇 |
1999年 | 69篇 |
1998年 | 45篇 |
1997年 | 45篇 |
1996年 | 32篇 |
1995年 | 26篇 |
1994年 | 18篇 |
1993年 | 10篇 |
1992年 | 15篇 |
1991年 | 12篇 |
1990年 | 16篇 |
1989年 | 14篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1978年 | 2篇 |
1975年 | 2篇 |
1965年 | 3篇 |
1963年 | 3篇 |
1962年 | 3篇 |
1961年 | 3篇 |
1960年 | 2篇 |
1958年 | 2篇 |
1957年 | 3篇 |
1955年 | 4篇 |
排序方式: 共有3766条查询结果,搜索用时 15 毫秒
1.
2.
These experiments explored the role of prior experience in 12- to 18-month-old infants' tool-directed actions. In Experiment 1, infants' use of a familiar tool (spoon) to accomplish a novel task (turning on lights inside a box) was examined. Infants tended to grasp the spoon by its handle even when doing so made solving the task impossible (the bowl did not fit through the hole in the box, but the handle did) and even though the experimenter demonstrated a bowl-grasp. In contrast, infants used a novel tool flexibly and grasped both sides equally often. In Experiment 2, infants received training using the novel tool for a particular function; 3 groups of infants were trained to use the tool differently. Later, infants' performance was facilitated on tasks that required infants to grasp the part of the tool they were trained to grasp. The results suggest that (a) infants' prior experiences with tools are important to understanding subsequent tool use, and (b) rather than learning about tool function (e.g., hammering), infants learn about which part of the tool is meant to be held, at least early in their exposure to a novel tool. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
3.
试论就业形势与战略 总被引:5,自引:1,他引:4
刘庆唐 《重庆理工大学学报(自然科学版)》2005,19(1):7-10
论述了就业的特殊重要性、目前我国就业形势的极端严重性,以及所应当采取的战略和措施。 相似文献
4.
5.
在已经得到的描述鱼雷罐喷粉处理基本参数具体表达式的基础上,运用多目标非线性优化方法,对工艺操作参数进行优化。 相似文献
6.
指出当今建筑业良好的市场给建筑师们提供了展示自己作品的广大空间 ,但其精品却为之甚少。为此 ,对建筑业存在的一些问题及制约建筑师出精品的主、客观因素进行了分析 ,指出建筑师应提高自身素质 ,树立精品意识 ,增强市场竞争能力 相似文献
7.
价格不确定情况下炼厂生产计划的优化 总被引:4,自引:0,他引:4
生产计划的编制是炼油企业生产经营管理中的一个关键环节,然而由于市场变化的不确定性,使企业制度长远规划受到限制,笔者将多目标规划应用于炼厂价格不确定情况下生产计划的制定,使所得到的生产计划在一定程度上反映市场的变化并能使企业的生产效益最优,为企业管理决策者进行长远规划给予指导。通过实例验证了该方法的可行性。 相似文献
8.
Claudio Arbib Fabrizio Marinelli 《International Journal of Flexible Manufacturing Systems》2003,15(4):333-354
A cook has to prepare n cakes using an oven with two racks. According to the recipe, the i-th cake has to be baked for exactly a
i minutes. Cakes to be cooked are taken from a table and carried to the oven, and once cooked are carried back to the table by means of a trolley that can carry two cakes at a time. What is the minimum number q
* of round trips required of the cook? This problem has application to the operation scheduling of transportation systems and to material cutting. A different problem arises according to whether the cook accepts or not to stay near the oven for awhile with the trolley. If the trolley cannot be idle at the oven, an optimum schedule with no oven idle-time always exists: consequently, the trolley schedule is trivial, and the problem is transformed into a set packing. For this case, we propose and test a heuristic method which generates all of the promising columns of the set packing, and solves the resulting problem by branch-and-bound. Instead, if the trolley can be idle at the oven for a limited amount of time, a problem arises to find an optimal schedule of the trolley: in this case we show how to use a scaling technique in order to obtain a very good feasible solution by the method above. 相似文献
9.
Allen Holder 《Optimization and Engineering》2006,7(4):501-526
The optimal partition for linear programming is induced by any strictly complementary solution, and this partition is important
because it characterizes the optimal set. However, constructing a strictly complementary solution in the presence of degeneracy
was not practical until interior point algorithms became viable alternatives to the simplex algorithm. We develop analogs
of the optimal partition for linear programming in the case of multiple objectives and show that these new partitions provide
insight into the optimal set (both pareto optimality and lexicographic ordering are considered). Techniques to produce these
optimal partitions are provided, and examples from the design of radiotherapy plans show that these new partitions are useful.
A. Holder. Research conducted at Trinity University, TX, and The University of Mississippi, MS. This research was partially
supported by ONR Grant N00014-01-1-0917. 相似文献
10.
Optimum thermoeconomic and thermodynamic performance characteristics of an irreversible three-heat-source heat pump 总被引:1,自引:0,他引:1
The coefficient of performance and specific heating load of an irreversible three-heat-source heat pump are given by using a general cycle model affected by the finite-rate heat transfer, heat leak and internal irreversibility of the cyclic working fluid. The heat pumping load divided by the total cost per unit time is taken as a new objective function and used to investigate the performance of the heat pump. The thermoeconomic and thermodynamic performance characteristics of the heat pump are discussed in detail. Some important performance parameters such as the thermoeconomic objective function and coefficient of performance are optimized. The optimally operating regions of the heat pump and the bounds of several performance parameters are determined. Finally, it is pointed out that the Carnot heat pump may be taken as a special case of a three-heat-source heat pump and consequently its optimal performance can be directly derived from the results obtained here. 相似文献