全文获取类型
收费全文 | 26832篇 |
免费 | 805篇 |
国内免费 | 32篇 |
专业分类
电工技术 | 330篇 |
综合类 | 15篇 |
化学工业 | 5904篇 |
金属工艺 | 527篇 |
机械仪表 | 471篇 |
建筑科学 | 1173篇 |
矿业工程 | 332篇 |
能源动力 | 658篇 |
轻工业 | 1783篇 |
水利工程 | 230篇 |
石油天然气 | 250篇 |
无线电 | 1719篇 |
一般工业技术 | 4115篇 |
冶金工业 | 6159篇 |
原子能技术 | 265篇 |
自动化技术 | 3738篇 |
出版年
2021年 | 420篇 |
2020年 | 277篇 |
2019年 | 363篇 |
2018年 | 445篇 |
2017年 | 383篇 |
2016年 | 497篇 |
2015年 | 402篇 |
2014年 | 636篇 |
2013年 | 1673篇 |
2012年 | 964篇 |
2011年 | 1220篇 |
2010年 | 941篇 |
2009年 | 982篇 |
2008年 | 1162篇 |
2007年 | 1074篇 |
2006年 | 981篇 |
2005年 | 884篇 |
2004年 | 749篇 |
2003年 | 717篇 |
2002年 | 710篇 |
2001年 | 490篇 |
2000年 | 394篇 |
1999年 | 448篇 |
1998年 | 441篇 |
1997年 | 427篇 |
1996年 | 473篇 |
1995年 | 445篇 |
1994年 | 454篇 |
1993年 | 437篇 |
1992年 | 433篇 |
1991年 | 273篇 |
1990年 | 411篇 |
1989年 | 387篇 |
1988年 | 337篇 |
1987年 | 404篇 |
1986年 | 351篇 |
1985年 | 441篇 |
1984年 | 465篇 |
1983年 | 398篇 |
1982年 | 376篇 |
1981年 | 298篇 |
1980年 | 298篇 |
1979年 | 357篇 |
1978年 | 299篇 |
1977年 | 238篇 |
1976年 | 216篇 |
1975年 | 245篇 |
1974年 | 216篇 |
1973年 | 223篇 |
1972年 | 167篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
L Robert 《Canadian Metallurgical Quarterly》1995,189(6):959-966
A distinction is made between atheromatous plaque formation and arteriosclerosis, only this second process is strictly age-dependent. Interactions between lipids and constituents of the vascular wall are however involved in both processes, although by different mechanisms. The progressive increase with age of elastase activity is a second important factor in the age-dependent progression of arteriosclerosis. The fragmentation of elastic fibers produces elastin peptides, present in the circulating blood in microgram/ml conc-s, increasing in several arteriopathies. The constant presence of elastin peptides in the circulation maintains activated the elastin receptor (16) on endothelial cells producing NO* with vasorelaxing activity (18). The simultaneous production of superoxyde leads to the formation of peroxynitrate, neutralized by reduced glutathion. This process, maintained over decades may well impair the antiradical defense mechanisms of the cells and deprive the endothelium from the vasorelaxing activity of NO*. We propose therefore that the maintained activation of the elastin receptor with free radical and lytic enzyme production might well represent the initiating process underlying atherogenesis. 相似文献
92.
93.
94.
Robert D. Cook 《Thin》1985,3(4):365-372
A cylindrical tank is mounted with its axis horizontal. Supports on either side run lengthwise. If the tank wall is thin, deformations significantly affect the stresses, so that standard stress formulae (which ignore deformations) may over-estimate stresses by a factor of ten or more. In this paper, deformations are accounted for by a nonlinear analysis. Stresses and deformed shapes are reported for various positions of the supports, radius to thickness ratios, and depths of fill. 相似文献
95.
96.
Preacher Kristopher J.; Rucker Derek D.; MacCallum Robert C.; Nicewander W. Alan 《Canadian Metallurgical Quarterly》2005,10(2):178
Analysis of continuous variables sometimes proceeds by selecting individuals on the basis of extreme scores of a sample distribution and submitting only those extreme scores to further analysis. This sampling method is known as the extreme groups approach (EGA). EGA is often used to achieve greater statistical power in subsequent hypothesis tests. However, there are several largely unrecognized costs associated with EGA that must be considered. The authors illustrate the effects EGA can have on power, standardized effect size, reliability, model specification, and the interpretability of results. Finally, the authors discuss alternative procedures, as well as possible legitimate uses of EGA. The authors urge researchers, editors, reviewers, and consumers to carefully assess the extent to which EGA is an appropriate tool in their own research and in that of others. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
97.
98.
Niklas Schlimm Mirko Novakovic Robert Spielmann Tobias Knierim 《Informatik-Spektrum》2007,48(6):251-258
Nicht-funktionale Anforderungen an ein Softwaresystem beschreiben Aspekte, die nicht direkt die Funktionalit?t, wie sie der
Benutzer sieht, betreffen. 相似文献
99.
Abe Schwartz Lili Wang Edward Early Adolfas Gaigalas Yu-zhong Zhang Gerald E. Marti Robert F. Vogt 《Journal of research of the National Institute of Standards and Technology》2002,107(1):83-91
The quantitation of fluorescence radiance may at first suggest the need to obtain the number of fluorophore that are responsible for the measured fluorescence radiance. This goal is beset by many difficulties since the fluorescence radiance depends on three parameters 1) the probability of absorbing a photon (molar extinction), 2) the number of fluorophores, and 3) the probability of radiative decay of the excited state (quantum yield). If we use the same fluorophore in the reference solution and the analyte then, to a good approximation, the molar extinction drops out from the comparison of fluorescence radiance and we are left with the comparison of fluorescence yield which is defined as the product of fluorophore concentration and the molecular quantum yield. The equality of fluorescence yields from two solutions leads to the notion of equivalent number of fluorophores in the two solutions that is the basis for assignment of MESF (Molecules of Equivalent Soluble Fluorophore) values. We discuss how MESF values are assigned to labeled microbeads and by extension to labeled antibodies, and how these assignments can lead to the estimate of the number of bound antibodies in flow cytometer measurements. 相似文献
100.
Robert L. Hirsch 《Journal of Fusion Energy》2002,21(2):113-116
Assuming significant technical success in the ITER project by the year 2015, it is likely that governments will want to develop a more comprehensive plan for DT tokamak fusion power commercialization. To provide a glimpse into many of the related issues, we construct conversations between the director of the U.S. fusion program and three specialists key to commercial fusion success: an environment and safety regulator, an environmentalist, and an electric generation investor. The insights from these imagined conversations will hopefully be of value as tokamak fusion power proponents plan beyond ITER. 相似文献