全文获取类型
收费全文 | 14319篇 |
免费 | 728篇 |
国内免费 | 220篇 |
专业分类
电工技术 | 184篇 |
综合类 | 55篇 |
化学工业 | 3069篇 |
金属工艺 | 502篇 |
机械仪表 | 275篇 |
建筑科学 | 521篇 |
矿业工程 | 43篇 |
能源动力 | 373篇 |
轻工业 | 1509篇 |
水利工程 | 81篇 |
石油天然气 | 369篇 |
武器工业 | 15篇 |
无线电 | 947篇 |
一般工业技术 | 1957篇 |
冶金工业 | 3522篇 |
原子能技术 | 142篇 |
自动化技术 | 1703篇 |
出版年
2023年 | 76篇 |
2022年 | 187篇 |
2021年 | 284篇 |
2020年 | 216篇 |
2019年 | 264篇 |
2018年 | 362篇 |
2017年 | 365篇 |
2016年 | 413篇 |
2015年 | 333篇 |
2014年 | 479篇 |
2013年 | 792篇 |
2012年 | 647篇 |
2011年 | 830篇 |
2010年 | 686篇 |
2009年 | 655篇 |
2008年 | 673篇 |
2007年 | 524篇 |
2006年 | 569篇 |
2005年 | 485篇 |
2004年 | 433篇 |
2003年 | 422篇 |
2002年 | 434篇 |
2001年 | 328篇 |
2000年 | 308篇 |
1999年 | 268篇 |
1998年 | 368篇 |
1997年 | 326篇 |
1996年 | 252篇 |
1995年 | 224篇 |
1994年 | 247篇 |
1993年 | 242篇 |
1992年 | 160篇 |
1991年 | 96篇 |
1990年 | 162篇 |
1989年 | 164篇 |
1988年 | 118篇 |
1987年 | 116篇 |
1986年 | 113篇 |
1985年 | 122篇 |
1984年 | 111篇 |
1983年 | 103篇 |
1982年 | 77篇 |
1981年 | 113篇 |
1979年 | 101篇 |
1978年 | 64篇 |
1977年 | 90篇 |
1976年 | 86篇 |
1975年 | 71篇 |
1974年 | 62篇 |
1971年 | 98篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
871.
Fatima Bennour Jacques Rogez Jean Claude Mathieu 《Journal of the American Ceramic Society》1996,79(10):2752-2754
The Na2 O-Cs2O-SiO2 system has been investigated by means of a new differential thermal analysis apparatus. Two compounds have been observed for the first time in the metasilicate and disilicate joins. The CsNaSi2 O5 disilicate melts congruently at 1217 K and the peritectic fusion of the CsNaSiO3 metasilicate occurs at 1120 K. 相似文献
872.
Surendra P. Verma Jean R. Philippot Bernard Bonnet Josette Sainte-Marie Yves Moschetto Donald F. H. Wallach 《Lipids》1985,20(12):890-896
Raman and resonance Raman spectra of plasma lipoproteins ± malondialdehyde were studied at concentrations which block the
normal receptor-mediated uptake by cells. The strong resonance Raman bands at about 1010, 1162 and 1530 cm−1, due to the presence of carotenoids in the lipoproteins, are envisaged as structural probes. High resolution resonance Raman
spectra of the 1500–1600 cm−1 region reveal multiple features suggesting the coexistence of several structural populations of β-carotene whose precise
assignment is complex. When plasma lipoproteins are reacted with malondialdehyde, a complex change occurs in the resonance
Raman banding of β-carotene in the 1500–1600 cm−1 region. Malonaldehyde (MDA) also modifies the acoustical region (70–200 cm−1 of low density lipoprotein (LDL) lipids. We suggest that malondialdehyde association with plasma lipoproteins alters the
lipid structure via apoprotein or apoprotein/lipid associations. 相似文献
873.
874.
Implicit induction in conditional theories 总被引:1,自引:0,他引:1
We propose a new procedure for proof by induction in conditional theories where case analysis is simulated by term rewriting. This technique reduces considerably the number of variables of a conjecture to be considered for applying induction schemes. Our procedure is presented as a set of inference rules whose correctness has been formally proved. Moreover, when the axioms are ground convergent and the functions are completely defined, it is possible to apply the system for refuting conjectures. The procedure is even refutationally complete for conditional equations with Boolean preconditions over free constructors. The method is entirely implemented in the proverSPIKE. This system has solved interesting problems in a completely automatic way, that is, without interaction with the user and without ad hoc heuristics. It has also proved the challenging Gilbreath card trick, with only two easy lemmas.Preliminary versions of the results have been presented at the 13th International Joint Conference on Artificial Intelligence, Chambéry (France), 1993 (Bouhoula and Rusinowith, 1993). 相似文献
875.
No authorship indicated 《Canadian Metallurgical Quarterly》1979,34(1):80b
Ernest Ropiquet Hilgard earned the Gold Medal Award as a gifted generalist, who has made scientific contributions to nearly every field of psychology, most notably in learning and states of consciousness; a deep student of psychological history and systems; a man of conscience, concerned with social issues and the applications of psychology to human welfare; a leader and statesman in social science research policy and education; and above all, a teacher, through his writings, his work with students, and his example. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
876.
In this paper, we present an approach, based on a Markov process, for modelling earthquake aftershocks. From our earthquake aftershock swarm files, we first show our preliminary observations on the phenomenon. Then we present the theoretical basis of a semi-Markovian approach and develop a parametric study of the proposed model. Finally, we discuss the results obtained to date, together with possible improvements of the model. 相似文献
877.
Rosendo PEA-EGUILUZ Jos A LPEZ-FERNNDEZ Antonio MERCADO-CABRERA Bethsabet JARAMILLO-SIERRA Rgulo LPEZ-CALLEJAS Benjamn RODRGUEZ-MNDEZ Ral VALENCIA-ALVARADO Allan A FLORES-FUENTES Arturo E MUOZ-CASTRO 《等离子体科学和技术》2017,19(7)
A new configuration of a resonant full-bridge flying capacitor multicell inverter has been designed and constructed with the aim of achieving an extended output voltage frequency range with low harmonic distortion and reduced semiconductor commutation losses. This configuration was tested as a power supply for two different coaxial dielectric barrier discharge reactors, one of them employed for electric characterization and the other one for inorganic compound elimination in an aqueous solution. Two different gas mixtures, 90% Ar–10% O_2 and80% Ar–20% O_2, were individually supplied during the experiments; the results showed a highefficiency removal of meta-cresol(m-cresol) to the order of 98%, which was obtained by adding more oxygen to the plasma gas mixture. 相似文献
878.
Wei Wu Foutse Khomh Bram Adams Yann-Gaël Guéhéneuc Giuliano Antoniol 《Empirical Software Engineering》2016,21(6):2366-2412
Frameworks are widely used in modern software development to reduce development costs. They are accessed through their Application Programming Interfaces (APIs), which specify the contracts with client programs. When frameworks evolve, API backward-compatibility cannot always be guaranteed and client programs must upgrade to use the new releases. Because framework upgrades are not cost-free, observing API changes and usages together at fine-grained levels is necessary to help developers understand, assess, and forecast the cost of each framework upgrade. Whereas previous work studied API changes in frameworks and API usages in client programs separately, we analyse and classify API changes and usages together in 22 framework releases from the Apache and Eclipse ecosystems and their client programs. We find that (1) missing classes and methods happen more often in frameworks and affect client programs more often than the other API change types do, (2) missing interfaces occur rarely in frameworks but affect client programs often, (3) framework APIs are used on average in 35 % of client classes and interfaces, (4) most of such usages could be encapsulated locally and reduced in number, and (5) about 11 % of APIs usages could cause ripple effects in client programs when these APIs change. Based on these findings, we provide suggestions for developers and researchers to reduce the impact of API evolution through language mechanisms and design strategies. 相似文献
879.
面炮(Arealshot)偏移技术是对实际炮集数据按照不同方向传播的平面波进行时间延迟分解并合成组合炮记录,分别进行组合震源下行波的向下波场外推和组合记录上行波的向下波场延拓,在相遇深度得到该方向平面波的反射波成像。本文基于面炮深度偏移技术,充分利用射线追踪计算量小和波动方程波场延拓的良好振幅特性,提出了用平面波射线追踪法计算平面波组合震源下行波前走时和面炮波场滞后时间成像的深度偏移方法,并着重讨论了程函方程有限差分法计算平面波传播时间和组合记录上行波场时间滞后的深度成像方法。通过对Marmousi模型数据的成像检验,表明该法要比积分法偏移效果优越。 相似文献
880.
We present a new algorithm,
called MCS-M,
for computing minimal triangulations of graphs.
Lex-BFS, a seminal algorithm for recognizing chordal graphs,
was the genesis for two other classical algorithms:
LEX M and MCS.
LEX M extends the fundamental concept used in Lex-BFS,
resulting in an algorithm that not only recognizes chordality,
but also computes a minimal triangulation of an arbitrary graph.
MCS simplifies the fundamental concept used in Lex-BFS,
resulting in a simpler algorithm for recognizing chordal graphs.
The new algorithm MCS-M combines
the extension of LEX M with the simplification of MCS,
achieving all the results of LEX M in the same time complexity. 相似文献