全文获取类型
收费全文 | 16410篇 |
免费 | 915篇 |
国内免费 | 637篇 |
专业分类
电工技术 | 816篇 |
综合类 | 1124篇 |
化学工业 | 1853篇 |
金属工艺 | 702篇 |
机械仪表 | 977篇 |
建筑科学 | 471篇 |
矿业工程 | 454篇 |
能源动力 | 514篇 |
轻工业 | 1610篇 |
水利工程 | 211篇 |
石油天然气 | 835篇 |
武器工业 | 82篇 |
无线电 | 2049篇 |
一般工业技术 | 846篇 |
冶金工业 | 586篇 |
原子能技术 | 249篇 |
自动化技术 | 4583篇 |
出版年
2024年 | 27篇 |
2023年 | 176篇 |
2022年 | 293篇 |
2021年 | 328篇 |
2020年 | 339篇 |
2019年 | 325篇 |
2018年 | 266篇 |
2017年 | 402篇 |
2016年 | 451篇 |
2015年 | 522篇 |
2014年 | 926篇 |
2013年 | 937篇 |
2012年 | 1209篇 |
2011年 | 1545篇 |
2010年 | 1197篇 |
2009年 | 1324篇 |
2008年 | 1168篇 |
2007年 | 1269篇 |
2006年 | 1148篇 |
2005年 | 810篇 |
2004年 | 649篇 |
2003年 | 568篇 |
2002年 | 450篇 |
2001年 | 325篇 |
2000年 | 235篇 |
1999年 | 194篇 |
1998年 | 137篇 |
1997年 | 109篇 |
1996年 | 80篇 |
1995年 | 66篇 |
1994年 | 70篇 |
1993年 | 49篇 |
1992年 | 24篇 |
1991年 | 31篇 |
1990年 | 22篇 |
1989年 | 32篇 |
1988年 | 10篇 |
1987年 | 10篇 |
1986年 | 7篇 |
1985年 | 14篇 |
1984年 | 19篇 |
1983年 | 17篇 |
1982年 | 24篇 |
1981年 | 21篇 |
1980年 | 74篇 |
1979年 | 13篇 |
1978年 | 5篇 |
1977年 | 10篇 |
1975年 | 6篇 |
1973年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Compared with other flexible energy‐storage devices, the design and construction of the compressible energy‐storage devices face more difficulty because they must accommodate large strain and shape deformations. In the present work, CoNi2S4 nanoparticles/3D porous carbon nanotube (CNT) sponge cathode with highly compressible property and excellent capacitance is prepared by electrodepositing CoNi2S4 on CNT sponge, in which CoNi2S4 nanoparticles with size among 10–15 nm are uniformly anchored on CNT, causing the cathode to show a high compression property and gives high specific capacitance of 1530 F g−1. Meanwhile, Fe2O3/CNT sponge anode with specific capacitance of 460 F g−1 in a prolonged voltage window is also prepared by electrodepositing Fe2O3 nanosheets on CNT sponge. An asymmetric supercapacitor (CoNi2S4/CNT//Fe2O3/CNT) is assembled by using CoNi2S4/CNT sponge as positive electrode and Fe2O3/CNT sponge as negative electrode in 2 m KOH solution. It exhibits excellent energy density of up to 50 Wh kg−1 at a power density of 847 W kg−1 and excellent cycling stability at high compression. Even at a strain of 85%, about 75% of the initial capacitance is retained after 10 000 consecutive cycles. The CoNi2S4/CNT//Fe2O3/CNT device is a promising candidate for flexible energy devices due to its excellent compressibility and high energy density. 相似文献
32.
随着电力、电气设备的日益复杂化,对于其安全性能也有了更高的要求,数字兆欧表作为测量绝缘阻值的重要工具,已在工业领域中广泛应用;为了满足测量精度以及兆欧表的可靠性,通过基于S3C2440的嵌入式平台,提出了一种基于数字兆欧表的自动切换档位的实现方案,以达到更加精确的测量;此方案通过判断采集到的电压值选择相应的采样电阻来实现,并结合硬件平台和软件设计,分别介绍了驱动程序和应用程序的编写与测试,并很好地应用到了实际电路中;经测试,能够达到预期的效果,测量精度高,测量误差控制在±2%。 相似文献
33.
34.
根据成缆生产线的工艺要求,提出了一种基于S7-300 PLC和现场总线的3150型盘绞成缆机控制系统的设计方案,给出了3150型盘绞成缆机的整体结构,详细介绍了系统硬件及软件设计,并给出了盘绞头与放线架的同步控制方法。实际应用表明,该系统结构简单、使用灵活方便、控制精度高、人机对话良好,达到了预期目标。 相似文献
35.
In this paper, we investigate an inexact hybrid projection-proximal method for solving a class of generalized mixed variational inequalities in Hilbert spaces. We construct a general inexact hybrid projection-proximal point algorithm, in which an inexact relaxed proximal point step is followed by a suitable orthogonal projection onto a hyperplane. Under some suitable conditions concerned with the pseudomonotone set-valued mapping T, the nonsmooth convex function f and the step size λk, we prove the convergence of the inexact hybrid projection-proximal point algorithm for solving generalized mixed variational inequalities in Hilbert spaces. 相似文献
36.
For a positive integer d, an L(d,1)-labeling f of a graph G is an assignment of integers to the vertices of G such that |f(u)−f(v)|?d if uv∈E(G), and |f(u)−f(v)|?1 if u and u are at distance two. The span of an L(d,1)-labeling f of a graph is the absolute difference between the maximum and minimum integers used by f. The L(d,1)-labeling number of G, denoted by λd,1(G), is the minimum span over all L(d,1)-labelings of G. An L′(d,1)-labeling of a graph G is an L(d,1)-labeling of G which assigns different labels to different vertices. Denote by the L′(d,1)-labeling number of G. Georges et al. [Discrete Math. 135 (1994) 103-111] established relationship between the L(2,1)-labeling number of a graph G and the path covering number of Gc, the complement of G. In this paper we first generalize the concept of the path covering of a graph to the t-group path covering. Then we establish the relationship between the L′(d,1)-labeling number of a graph G and the (d−1)-group path covering number of Gc. Using this result, we prove that and for bipartite graphs G can be computed in polynomial time. 相似文献
37.
B. Farhadinia 《Information Sciences》2011,181(7):1348-1357
The main aims of this study are to derive the fuzzy Euler-Lagrange conditions for both fuzzy unconstrained and constrained variational problems based on the concepts of differentiability and integrability of a fuzzy mapping that may be parameterized by the left and right-hand functions of its α-level sets. 相似文献
38.
We investigate asymptotic behavior of the C0-semigroup T(t) associated with the mono-tubular heat exchanger equation with output feedback by a perturbation method. It is shown that T(t) is bounded if a constraint is satisfied by the parameters and the spatial distribution function. Further, applying the Arendt-Batty-Lyubich-Vu theorem, a criterion is established to judge strong stability of T(t). 相似文献
39.
40.
简介了电炉法CS2 废气吸附的原理及工艺流程 ,开辟了H2 S利用的新途径 ,具有较好的环境效益和经济效益 相似文献