全文获取类型
收费全文 | 45758篇 |
免费 | 4697篇 |
国内免费 | 3212篇 |
专业分类
电工技术 | 2118篇 |
综合类 | 4190篇 |
化学工业 | 7403篇 |
金属工艺 | 2404篇 |
机械仪表 | 2287篇 |
建筑科学 | 5102篇 |
矿业工程 | 2343篇 |
能源动力 | 1718篇 |
轻工业 | 3518篇 |
水利工程 | 1469篇 |
石油天然气 | 2478篇 |
武器工业 | 476篇 |
无线电 | 5439篇 |
一般工业技术 | 6819篇 |
冶金工业 | 2307篇 |
原子能技术 | 980篇 |
自动化技术 | 2616篇 |
出版年
2024年 | 213篇 |
2023年 | 746篇 |
2022年 | 1296篇 |
2021年 | 1590篇 |
2020年 | 1653篇 |
2019年 | 1483篇 |
2018年 | 1292篇 |
2017年 | 1693篇 |
2016年 | 1675篇 |
2015年 | 1744篇 |
2014年 | 2625篇 |
2013年 | 2766篇 |
2012年 | 3143篇 |
2011年 | 3351篇 |
2010年 | 2597篇 |
2009年 | 2700篇 |
2008年 | 2497篇 |
2007年 | 3030篇 |
2006年 | 2790篇 |
2005年 | 2299篇 |
2004年 | 1952篇 |
2003年 | 1727篇 |
2002年 | 1490篇 |
2001年 | 1186篇 |
2000年 | 1081篇 |
1999年 | 825篇 |
1998年 | 669篇 |
1997年 | 634篇 |
1996年 | 516篇 |
1995年 | 444篇 |
1994年 | 385篇 |
1993年 | 323篇 |
1992年 | 264篇 |
1991年 | 213篇 |
1990年 | 185篇 |
1989年 | 141篇 |
1988年 | 104篇 |
1987年 | 66篇 |
1986年 | 47篇 |
1985年 | 35篇 |
1984年 | 36篇 |
1983年 | 23篇 |
1982年 | 19篇 |
1981年 | 12篇 |
1980年 | 19篇 |
1979年 | 22篇 |
1965年 | 5篇 |
1963年 | 5篇 |
1959年 | 9篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
PowerPoint2000是Microsoft公司办公自动化软件Office2000的重要构件之一。其自身具有强大的处理功能,尤其是PowerPoint2000所提供的基本动画效果,更是给演示文稿增添了很多色彩。如果能将这些基本动画效果巧妙地组合在一起,就会创作出更富感染力的作品。就创作中的技巧并结合应用举例分析如下。相信人们可以利用这些设计思想,创作出更加精彩的作品。 相似文献
83.
The cost of maintaining a software system over a long period of time far exceeds its initial development cost. Much of the maintenance cost is attributed to the time required by new developers to understand legacy systems. High-level structural information helps maintainers navigate through the numerous low-level components and relations present in the source code. Modularization tools can be used to produce subsystem decompositions from the source code but do not typically produce high-level architectural relations between the newly found subsystems. Controlling subsystem interactions is one important way in which the overall complexity of software maintenance can be reduced.We have developed a tool, called ARIS (Architecture Relation Inference System), that enables software engineers to define rules and relations for regulating subsystem interactions. These rules and relations are called Interconnection Styles and are definedusing a visual notation. The style definition is used by our tool to infer subsystem-level relations in designs being reverse engineered from source code.In this paper we describe our tool and its underlying techniques and algorithms. Using a case study, we describe how ARIS is used to reverse engineer high-level structural information from a real application. 相似文献
84.
85.
王芬 《武汉理工大学学报(材料科学英文版)》2005,20(Z1)
1Introduction Harmfulbacteriaexistanywhereintheworldsuchas soil,air,water,surfacesofobjectsandourskins,etc.Thenumberofbacteriumisenormous,withmanydiffer entspecies.Theyhavethreatenedthehealthofhuman beingsseriously.Withthedevelopmentofeconomyand environme… 相似文献
86.
针对武钢热轧厂层流冷却系统能耗高,水压不稳,系统反应慢,供水泵工作效率低等缺陷,进行系统改造。提高了系统的控制精度和产品质量,节能降耗取得了明显的效果。 相似文献
87.
Tang Helen H. Y.; McNally Gavan P.; Richardson Rick 《Canadian Metallurgical Quarterly》2007,121(6):1421
The authors studied the role of gamma-aminobutyric acid (GABA) in 2 types of forgetting of fear in the developing rat. One type of forgetting studied was that observed after an intermediate retention interval (the "Kamin effect"); the other type studied was that observed after a longer interval (infantile amnesia). Rats were given pairings of an auditory conditioned stimulus with shock, and learned fear was assessed by freezing. Forgetting at an intermediate retention interval (1 hr) was not alleviated by the GABAA receptor partial inverse agonist FG7142 (0, 1, 5, or 10 mg/kg), whereas forgetting at a longer retention interval (48 hr) was alleviated. These results suggest that in the developing rat, forgetting observed at different retention intervals is mediated by different physiological mechanisms. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
88.
The effect of ductile crack growth on the near tip stress field in two different specimen geometries has been investigated. For homogeneous specimens it is observed that the peak stress level increases with ductile crack growth. The effect is most pronounced up to about 1 mm of crack growth. For low and intermediate hardening there is a significant effect of specimen size on the stress level. In case of mismatch in yield stress, the simulations show that the increase in stress level in the material with the lower yield stress is of a similar magnitude as is the case for stationary cracks. In case of ductile crack growth deviation from the original crack plane occurs, the highest stresses are still found close to the interface, and not in front of the current crack tip. 相似文献
89.
反渗透膜仓用韧性环氧树脂基体研究 总被引:1,自引:0,他引:1
工业上广泛使用反渗透膜仓制备高纯水,为了用玻璃钢替代不锈钢,研究了一种适合湿法缠绕的反渗透膜仓用韧性环氧基体。在配方中采用液体酸酐固化剂甲基四氢邻苯二甲酸酐和高效活性增韧剂,对树脂基体和复合材料力学性能及耐水性能的研究表明该树脂基体具有许多优良性能,如拉伸强度≥86.2MPa,断裂延伸率≥5.2%,弯曲强度≥139MPa,制得膜仓爆破时纤维强度转化率高达88.7%,耐疲劳达10万次而无损伤。此外,配方体系室温下粘度为0.35~0.4Pa·s,适用期≥8h,室温下在水中浸泡180d后吸水率低于0.5%,同不锈钢相比成本降低1/2。实验结果表明,该韧性环氧基体完全适用于反渗透膜仓使用。 相似文献
90.
J Schlipf 《Bulletin of Materials Science》1989,12(3-4):185-193
A model for propagating deformation bands is developed, based on a mechanical equation of state and on evolution equations
for the structure parameters. It is shown that, contrary to normal deformation, it is necessary to discriminate between global
parameters which depend solely on time elapsed and local parameters which are functions of the strain history. Correspondingly,
two sets of equations are presented, one describing the development of the global parameters in the course of time, the other
giving the evolution of the local state parameters in the course of deformation, i.e. as a function of strain. Measurable
quantities derived from the first set are the load serrations and the band velocity, while the second set yields the flow
stress and the strain profile of the propagating band. 相似文献