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排序方式: 共有1630条查询结果,搜索用时 15 毫秒
1.
针对移动机器人在海水环境中的三维路径规划问题容易陷入局部最优和收敛慢等瑕疵,根据三维环境全局信息来改进蚁群算法以提高实时性和收敛速度。改进蚁群算法的启发函数,采用局部信息和全局信息结合动态地改进信息素更新方式,以及根据三维空间中路径的平坦程度和光滑度二阶微分分别增加了一阶微分和二阶微分来再次修改信息素更新规则。仿真对比实验结果显示改进后的蚁群算法克服了收敛速度慢、容易陷入局部最优的缺点。 相似文献
2.
Adults of Tribolium castaneum (Herbst) and Rhyzopertha dominica (F.) biosynthesize aggregation pheromones 4,8-dimethyldecanal and dominicalure-1/dominicalure-2, respectively. These pheromones are commonly used independently, and their simultaneous use has not been adequately studied. Furthermore, information on trapping flying R. dominica in pheromone traps is minimum. Therefore, the objectives were to evaluate distance of attraction of T. castaneum and R. dominica adults to traps having both pheromones, and height of R. dominica adult attraction to traps with its pheromone lure alone. In first experiment, both pheromones were deployed simultaneously inside a commercial pitfall trap. One-month-old 20 T. castaneum and R. dominica adults were released every 30 cm from the pheromone trap. The adults trapped were recorded at 4 and 24 h following their release. Adults of both species released were captured in higher percentages at 24 h than 4 h. At 30 cm distance, these values were 45.5% for T. castaneum and 10–12% for R. dominica for 24 h whereas they were 40.5% for T. castaneum and 5–7.5% for R. dominica following 4 h exposure. The maximum trap capture was at 30 cm for T. castaneum and 30–60 cm for R. dominica. In second experiment, a trap with two rubber septa containing dominicalure-1 and dominicalure-2 was placed at different heights inside cage, and R. dominica adults were released at the bottom. In each experiment, four replicates were tested. After 24 h, flying R. dominica adults were captured in progressively lower percentages as trap height increased up to 40 cm above the bottom of cage. Trap heights above 10 cm exhibited decreased trap capture of R. dominica compared to those at 3 cm. We conclude that simultaneous use of both aggregation pheromones better facilitates trapping of walking T. castaneum and R. dominica. Traps above 10 cm show decreased captures of flying R. dominica. 相似文献
3.
The Yeast ATF1 Acetyltransferase Efficiently Acetylates Insect Pheromone Alcohols: Implications for the Biological Production of Moth Pheromones 下载免费PDF全文
Bao-Jian Ding Ida Lager Sunil Bansal Timothy P. Durrett Sten Stymne Christer Löfstedt 《Lipids》2016,51(4):469-475
Many moth pheromones are composed of mixtures of acetates of long‐chain (≥10 carbon) fatty alcohols. Moth pheromone precursors such as fatty acids and fatty alcohols can be produced in yeast by the heterologous expression of genes involved in insect pheromone production. Acetyltransferases that subsequently catalyze the formation of acetates by transfer of the acetate unit from acetyl‐CoA to a fatty alcohol have been postulated in pheromone biosynthesis. However, so far no fatty alcohol acetyltransferases responsible for the production of straight chain alkyl acetate pheromone components in insects have been identified. In search for a non‐insect acetyltransferase alternative, we expressed a plant‐derived diacylglycerol acetyltransferase (EaDAcT) (EC 2.3.1.20) cloned from the seed of the burning bush (Euonymus alatus) in a yeast system. EaDAcT transformed various fatty alcohol insect pheromone precursors into acetates but we also found high background acetylation activities. Only one enzyme in yeast was shown to be responsible for the majority of that background activity, the acetyltransferase ATF1 (EC 2.3.1.84). We further investigated the usefulness of ATF1 for the conversion of moth pheromone alcohols into acetates in comparison with EaDAcT. Overexpression of ATF1 revealed that it was capable of acetylating these fatty alcohols with chain lengths from 10 to 18 carbons with up to 27‐ and 10‐fold higher in vivo and in vitro efficiency, respectively, compared to EaDAcT. The ATF1 enzyme thus has the potential to serve as the missing enzyme in the reconstruction of the biosynthetic pathway of insect acetate pheromones from precursor fatty acids in yeast. 相似文献
4.
一种改进的自适应进化粒子群优化算法 总被引:1,自引:0,他引:1
针对粒子群优化算法容易陷入局部极值点以及进化后期收敛慢和优化精度较差等缺点,提出一种改进的自适应进化算法.该算法引入信息扩散函数,根据不同粒子的位置及对应适应值与当前群体最佳位置和最佳适应值的关系,控制粒子变尺度向群体当前最佳位置移动;基于多样性反馈机制动态调节惯性权值和控制粒子群的微变异.通过复杂基准函数的仿真优化结果表明,改进算法具有抑制早熟、收敛速度快、求解精度高的特点. 相似文献
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7.
针对单一探测机器人在复杂环境下可靠性和容错能力较低难以完成探测任务的问题,采用了多机器人协作探测的方法,利用吸引素和排斥素将引力和斥力之间的平衡点作为机器人队形控制及避障行为的约束条件,同时利用信息素之间的反应,计算出指引机器人到达目标点的目标信息素及返回初终点的返回信息素的数值,实现缩小机器人的搜索空间,形成最优路径,提高多机器人的协作探测能力。实验证明,引入信息素反应理论,减化机器人相互协作模型,同时能够完成复杂环境下的机器人探测任务,达到了预期效果。 相似文献
8.
针对传统蚁群算法在无人机3 维航路规划中存在搜索时间长、容易陷入局部最优解的问题,提出一种蚁
群算法的改进策略。将固定翼无人机的性能约束条件作为待扩展节点是否可行的判断条件,减小计算量和算法搜索
时间;对航路点的高度规划采用直接设定策略,将3 维航路规划问题简化为2 维航路规划问题,减小算法的复杂性;
改进全局信息素更新规则和安全启发因子,解决了局部最优解和威胁源规避问题。仿真结果表明:改进蚁群算法与
传统蚁群算法相比,能够有效规划出一条从起点到终点的飞行航路,具有更高的有效性和实用性。 相似文献
9.
主要研究了β21S钛合金的工艺塑性图,制定了该合金的锻造工艺参数。通过该合金的工艺塑性图,确定变形温度为750-1050℃,最大变形量为75%-80%,终缎温度为700℃。从合金的工艺塑性角度来看,以上 数据是合理的。 相似文献
10.
David C. Robacker Martin Aluja Robert J. Bartelt Joseph Patt 《Journal of chemical ecology》2009,35(5):601-609
Emissions from sexually active Anastrepha serpentina males were collected by solid-phase microextraction. Calling behavior of wild-type males showed no clear peak during the
day, except that it was evident less frequently immediately after daybreak and just before dark. Calling by laboratory males
was highest between 8 and 11 h after onset of the photophase, and mating by wild flies occurred mostly between 6 and 10 h
after onset of the photophase. Two major components of male emissions were identified as 2,5-dimethylpyrazine (DMP) and 3,6-dihydro-2,5-dimethylpyrazine
(DHDMP). DHDMP was synthesized, and the identity of the natural product confirmed by comparison of gas chromatographic retention
times and mass spectrum. Emissions of DMP and DHMP were greatest during peak calling behavior, with males emitting up to 1.8
and 3.3 μg/h of DMP and DHDMP, respectively. A minor component, which did not vary with time of day, was identified as 2,3,5-trimethylpyrazine.
To our knowledge, this is the first report of 3,6-dihydro-2,5-dimethylpyrazine in nature.
D. C. Robacker and R. J. Bartelt are now retired. 相似文献