全文获取类型
收费全文 | 6957篇 |
免费 | 633篇 |
国内免费 | 295篇 |
专业分类
电工技术 | 379篇 |
技术理论 | 3篇 |
综合类 | 497篇 |
化学工业 | 1199篇 |
金属工艺 | 342篇 |
机械仪表 | 448篇 |
建筑科学 | 555篇 |
矿业工程 | 246篇 |
能源动力 | 202篇 |
轻工业 | 388篇 |
水利工程 | 143篇 |
石油天然气 | 439篇 |
武器工业 | 56篇 |
无线电 | 675篇 |
一般工业技术 | 870篇 |
冶金工业 | 430篇 |
原子能技术 | 78篇 |
自动化技术 | 935篇 |
出版年
2024年 | 43篇 |
2023年 | 129篇 |
2022年 | 239篇 |
2021年 | 341篇 |
2020年 | 250篇 |
2019年 | 207篇 |
2018年 | 235篇 |
2017年 | 257篇 |
2016年 | 228篇 |
2015年 | 312篇 |
2014年 | 351篇 |
2013年 | 388篇 |
2012年 | 424篇 |
2011年 | 462篇 |
2010年 | 402篇 |
2009年 | 375篇 |
2008年 | 327篇 |
2007年 | 326篇 |
2006年 | 339篇 |
2005年 | 314篇 |
2004年 | 200篇 |
2003年 | 228篇 |
2002年 | 214篇 |
2001年 | 178篇 |
2000年 | 188篇 |
1999年 | 176篇 |
1998年 | 157篇 |
1997年 | 110篇 |
1996年 | 111篇 |
1995年 | 82篇 |
1994年 | 69篇 |
1993年 | 41篇 |
1992年 | 42篇 |
1991年 | 41篇 |
1990年 | 25篇 |
1989年 | 24篇 |
1988年 | 16篇 |
1987年 | 12篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1975年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有7885条查询结果,搜索用时 15 毫秒
1.
There is growing evidence that the amino-terminal globular domain of apolipoprotein B (apoB) is essential for lipoprotein particle formation in the hepatic endoplasmic reticulum. To identify the structural requirements for its function in lipoprotein assembly, cysteine (Cys) pairs required to form the seven disulfide bonds within the amino-terminal 21% of apoB were replaced in groups or individually by serine. Substitution of Cys pairs required for formation of disulfide bonds 1-3 or 4-7 (numbered from amino to carboxyl terminus) completely blocked the secretion of apoB28 in transfected HepG2 cells. To identify the specific disulfide bonds required for secretion, Cys pairs were mutated individually. Substitution of Cys pairs required for disulfide bonds 1, 3, 5, 6, or 7 had little or no impact on apoB28 secretion or buoyant density. In contrast, individual substitution of Cys pair 2 (amino acid residues 51 and 70) or 4 (218 and 234) severely inhibited apoB28 secretion and its capacity to undergo intracellular assembly with lipid. The same assembly and secretion defects were observed when these mutations were expressed as part of apoB50. These studies provide direct evidence that the ability of the internal lipophilic regions of apoB to engage in the recruitment and sequestration of lipid during translation is critically dependent upon a structural configuration contained within or affected by the amino-terminal 5% of the protein. 相似文献
2.
Weijia Shang O'Keefe M.T. Fortes J.A.B. 《Parallel and Distributed Systems, IEEE Transactions on》1994,5(2):193-204
This paper describes several loop transformation techniques for extracting parallelism from nested loop structures. Nested loops can then be scheduled to run in parallel so that execution time is minimized. One technique is called selective cycle shrinking, and the other is called true dependence cycle shrinking. It is shown how selective shrinking is related to linear scheduling of nested loops and how true dependence shrinking is related to conflict-free mappings of higher dimensional algorithms into lower dimensional processor arrays. Methods are proposed in this paper to find the selective and true dependence shrinkings with minimum total execution time by applying the techniques of finding optimal linear schedules and optimal and conflict-free mappings proposed by W. Shang and A.B. Fortes 相似文献
3.
W. Shang B. Robrahn F. Golding M. H. J. Koch 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2004,530(3):513-520
A data acquisition system for time resolved X-ray scattering experiments using linear, quadrant or area gas proportional detectors with delay line readout based on commercially available hardware (National Instruments) is described. The system can easily be configured for recording data from point detectors (e.g. photomultipliers and photodiodes) and/or ancillary data only. Applications involving measurements with two different types of time to digital converters illustrate the features and performances of the system. 相似文献
4.
本文介绍了笔者设计并实现的一种新型的面向对象的程序设计语言,着重讨论了在设计过程中采用的新的概念,并和其它类似语言作了比较. 相似文献
5.
氧气生产单位保用户用气一旦出现较为紧张的局面时,如何正确处理保安全生产运行、保用户生产、安排抢修时间三者之间的关系,值得关注与研究。 相似文献
6.
DESP: a distributed economics-based subcontracting protocol for computation distribution in power-aware mobile ad hoc networks 总被引:1,自引:0,他引:1
In this paper, we present a new economics-based power-aware protocol, called the distributed economic subcontracting protocol (DESP) that dynamically distributes task computation among mobile devices in an ad hoc wireless network. Mobile computation devices may be energy buyers, contractors, or subcontractors. Tasks are transferred between devices via distributed bargaining and transactions. When additional energy is required, buyers and contractors negotiate energy prices within their local markets. Contractors and subcontractors spend communication and computation energy to relay or execute buyers' tasks. Buyers pay the negotiated price for this energy. Decision-making algorithms are proposed for buyers, contractors, and subcontractors, each of which has a different optimization goal. We have built a wireless network simulator, called ESIM, to assist in the design and analysis of these algorithms. When the average communication energy required transferring a task is less than the average energy required to execute a task, our experimental results indicate that markets based on our protocol and decision-making algorithms fairly and effectively allocate energy resources among different tasks in both cooperative and competitive scenarios. 相似文献
7.
本文简单介绍NexGen公司最新设计出的Nx586CPU。它是一种80×86兼容的处理器,文中介绍了它的微体系结构,RISC86指令等。 相似文献
8.
9.
住宅厨房共用排烟系统性能比较 总被引:3,自引:1,他引:2
介绍了当地住宅厨房通风设计的发展简况,比较了两种房共用排烟系统的构造,尺寸,性能,造价及能耗,对厨房通风设计和施工提出了建议。 相似文献
10.