全文获取类型
收费全文 | 22563篇 |
免费 | 2826篇 |
国内免费 | 1855篇 |
专业分类
电工技术 | 1368篇 |
技术理论 | 1篇 |
综合类 | 2987篇 |
化学工业 | 1200篇 |
金属工艺 | 1392篇 |
机械仪表 | 2197篇 |
建筑科学 | 2356篇 |
矿业工程 | 738篇 |
能源动力 | 602篇 |
轻工业 | 865篇 |
水利工程 | 736篇 |
石油天然气 | 1435篇 |
武器工业 | 167篇 |
无线电 | 1896篇 |
一般工业技术 | 2033篇 |
冶金工业 | 711篇 |
原子能技术 | 219篇 |
自动化技术 | 6341篇 |
出版年
2024年 | 87篇 |
2023年 | 260篇 |
2022年 | 535篇 |
2021年 | 646篇 |
2020年 | 736篇 |
2019年 | 580篇 |
2018年 | 570篇 |
2017年 | 794篇 |
2016年 | 828篇 |
2015年 | 983篇 |
2014年 | 1428篇 |
2013年 | 1386篇 |
2012年 | 1684篇 |
2011年 | 1786篇 |
2010年 | 1440篇 |
2009年 | 1475篇 |
2008年 | 1458篇 |
2007年 | 1676篇 |
2006年 | 1487篇 |
2005年 | 1196篇 |
2004年 | 986篇 |
2003年 | 856篇 |
2002年 | 682篇 |
2001年 | 574篇 |
2000年 | 521篇 |
1999年 | 426篇 |
1998年 | 352篇 |
1997年 | 282篇 |
1996年 | 326篇 |
1995年 | 274篇 |
1994年 | 207篇 |
1993年 | 140篇 |
1992年 | 132篇 |
1991年 | 88篇 |
1990年 | 75篇 |
1989年 | 78篇 |
1988年 | 55篇 |
1987年 | 38篇 |
1986年 | 23篇 |
1985年 | 24篇 |
1984年 | 17篇 |
1983年 | 16篇 |
1982年 | 10篇 |
1981年 | 2篇 |
1980年 | 6篇 |
1979年 | 10篇 |
1978年 | 3篇 |
1959年 | 1篇 |
1956年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Value stream mapping (VSM) is a useful tool for describing the manufacturing state, especially for distinguishing between those activities that add value and those that do not. It can help in eliminating non-value activities and reducing the work in process (WIP) and thereby increase the service level. This research follows the guidelines for designing future state VSM. These guidelines consist of five factors which can be changed simply, without any investment. These five factors are (1) production unit; (2) pacemaker process; (3) number of batches; (4) production sequence; and (5) supermarket size. The five factors are applied to a fishing net manufacturing system. Using experimental design and a simulation optimizing tool, the five factors are optimized. The results show that the future state maps can increase service level and reduce WIP by at least 29.41% and 33.92% respectively. For the present study, the lean principles are innovatively adopted in solving a fishing net manufacturing system which is not a well-addressed problem in literature. In light of the promising empirical results, the proposed methodologies are also readily applicable to similar industries. 相似文献
2.
Data fitting with B-splines is a challenging problem in reverse engineering for CAD/CAM, virtual reality, data visualization, and many other fields. It is well-known that the fitting improves greatly if knots are considered as free variables. This leads, however, to a very difficult multimodal and multivariate continuous nonlinear optimization problem, the so-called knot adjustment problem. In this context, the present paper introduces an adapted elitist clonal selection algorithm for automatic knot adjustment of B-spline curves. Given a set of noisy data points, our method determines the number and location of knots automatically in order to obtain an extremely accurate fitting of data. In addition, our method minimizes the number of parameters required for this task. Our approach performs very well and in a fully automatic way even for the cases of underlying functions requiring identical multiple knots, such as functions with discontinuities and cusps. To evaluate its performance, it has been applied to three challenging test functions, and results have been compared with those from other alternative methods based on AIS and genetic algorithms. Our experimental results show that our proposal outperforms previous approaches in terms of accuracy and flexibility. Some other issues such as the parameter tuning, the complexity of the algorithm, and the CPU runtime are also discussed. 相似文献
3.
《Planning》2019,(6)
减少手术创伤始终是快速康复的决定性因素,这一点在目前的加速康复外科研究尤其是复杂手术,如妇科肿瘤手术中尚未得到充分重视。尊重学习曲线、全面规划手术方案、总结失利经验、开展前瞻性研究是解决此问题的主要方案。本文着重讨论妇科肿瘤手术创伤对术后加速康复的影响及可能的改进措施。 相似文献
4.
《Energy Policy》2015
The low price of lead-acid, the most popular battery, is often used in setting cost targets for emerging energy storage technologies. Future cost reductions in lead acid batteries could increase investment and time scales needed for emerging storage technologies to reach cost-parity. In this paper the first documented model of cost reductions for lead-acid batteries is developed. Regression to a standard experience curve using 1989–2012 data yield a poor fit, with R2 values of 0.17 for small batteries and 0.05 for larger systems. To address this problem, battery costs are separated into material and residual costs, and experience curves developed for residual costs. Depending on the year, residual costs account for 41–86% of total battery cost. Using running-time averages to address volatility in material costs, a 4-year time average experience curve for residual costs yield much higher R2, 0.78 for small and 0.74 for large lead-acid batteries. The learning rate for residual costs in lead-acid batteries is 20%, a discovery with policy implications. Neglecting to consider cost reductions in lead-acid batteries could result in failure of energy storage start-ups and public policy programs. Generalizing this result, learning in incumbent technologies must be understood to assess the potential of emerging ones. 相似文献
5.
介绍了皮带秤秤架响应特性曲线分析方法,对四种结构形式的秤架进行了响应特性曲线分析和比较,得出的结论是:悬浮式秤架的计量特性最好。 相似文献
6.
从扬声器系统的等效类比线路出发,得出了阻抗特性Z(jω)的表达形式及其曲线。采用全面最小二乘法识别扬声器系统的时域函数的全套系数,从而测出扬声器系统的低频特性参数。以计算机仿真技术为基础,通过MATLAB和EWB软件进行系统模拟分析仿真,得到扬声器系统的阶跃响应、阻抗曲线等特性。 相似文献
7.
一种基于Normal基椭圆曲线密码芯片的设计 总被引:3,自引:3,他引:0
文章设计了一款椭圆曲线密码芯片。实现了GF(2^233)域上normal基椭圆曲线数字签名和认证。并支持椭圆曲线参数的用户配置。在VLSI的实现上,提出了一种新的可支持GF(2^233)域和GF(p)域并行运算的normal基椭圆曲线VLSI架构。其架构解决了以往GF(p)CA算迟后于GF(2^233)域运算的问题,从而提高了整个芯片的运算吞吐率。基于SMIC 0.18μm最坏的工艺,综合后关键路径最大时延3.8ns,面积18mm^2;考虑布局布线的影响,芯片的典型的情况下,每秒可实现8000次签名或4500次认证。 相似文献
8.
文章主要介绍了光传送网(OTN)中光传输模块(OTM)的映射、复用结构、光通道数据单元(ODUk)的时分复用以及客户信号的映射方法. 相似文献
9.
10.
一种新型递减曲线的简单求法与应用 总被引:2,自引:2,他引:0
通过对油气藏产量递减的研究、线性最优化方法的分析研究及文献[1]提出的这种新型递减曲线的研究,提出了解这种方程的一个简单求法。通过现场的实例应用表明:提出的方法具有简单、方便、方法可靠的优点。采用此方法时,产量不以年为单位而是以月为单位进行计算,这将使计算更准确、更合理。 相似文献