全文获取类型
收费全文 | 29003篇 |
免费 | 715篇 |
国内免费 | 34篇 |
专业分类
电工技术 | 346篇 |
综合类 | 14篇 |
化学工业 | 6152篇 |
金属工艺 | 564篇 |
机械仪表 | 500篇 |
建筑科学 | 1279篇 |
矿业工程 | 339篇 |
能源动力 | 712篇 |
轻工业 | 1921篇 |
水利工程 | 239篇 |
石油天然气 | 254篇 |
无线电 | 1880篇 |
一般工业技术 | 4437篇 |
冶金工业 | 6908篇 |
原子能技术 | 276篇 |
自动化技术 | 3931篇 |
出版年
2022年 | 257篇 |
2021年 | 422篇 |
2020年 | 274篇 |
2019年 | 363篇 |
2018年 | 434篇 |
2017年 | 387篇 |
2016年 | 496篇 |
2015年 | 410篇 |
2014年 | 638篇 |
2013年 | 1766篇 |
2012年 | 987篇 |
2011年 | 1280篇 |
2010年 | 989篇 |
2009年 | 1029篇 |
2008年 | 1217篇 |
2007年 | 1139篇 |
2006年 | 1038篇 |
2005年 | 948篇 |
2004年 | 805篇 |
2003年 | 765篇 |
2002年 | 746篇 |
2001年 | 534篇 |
2000年 | 435篇 |
1999年 | 498篇 |
1998年 | 655篇 |
1997年 | 546篇 |
1996年 | 554篇 |
1995年 | 515篇 |
1994年 | 526篇 |
1993年 | 499篇 |
1992年 | 467篇 |
1991年 | 293篇 |
1990年 | 430篇 |
1989年 | 406篇 |
1988年 | 357篇 |
1987年 | 424篇 |
1986年 | 370篇 |
1985年 | 463篇 |
1984年 | 484篇 |
1983年 | 412篇 |
1982年 | 400篇 |
1981年 | 321篇 |
1980年 | 316篇 |
1979年 | 381篇 |
1978年 | 322篇 |
1977年 | 274篇 |
1976年 | 277篇 |
1975年 | 259篇 |
1974年 | 230篇 |
1973年 | 242篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
To enhance the understanding of the behavior and effects of the precipitation of MnO2 particles in the subsurface generated during in situ chemical oxidation (ISCO) using permanganate, laboratory batch experiments were completed to examine the influence that varied reaction matrix conditions have on the generation and properties of manganese oxides. The conditions examined include organic material type and concentration, permanganate concentration, pH, and the presence of calcium (as a representative divalent cation) in solution. Experimental studies included: (1) spectrophotometric examination of permanganate depletion and manganese oxides generation over time during reactions with trichloroethene; (2) scanning electron microscopy analyses of manganese particle morphology; (3) particle size distribution (filtration) characterization studies; and (4) optical particle sizing and numeration studies. Bench-scale, batch experiments were conducted to focus on fundamental chemical properties affecting particle development under varied potential environmental conditions. The amount of manganese oxides particles that develop, grow, and potentially settle as a result of permanganate ISCO of organic contaminants is a function of the particle size and concentration, the time allowed for particle development, and the impact of matrix conditions on the ability of particles to agglomerate. 相似文献
2.
Albrecht Jason E.; O'Brien Edward J.; Mason Robert A.; Myers Jerome L. 《Canadian Metallurgical Quarterly》1995,21(2):364
An implicit assumption of several causal reasoning models is that readers adopt the goals of a narrative's protagonist during text comprehension. In apparent violation of this assumption, readers participating in Experiment 1 of the present study drew inferences relevant to a protagonist's goal even when that goal was already satisfied from the perspective of the protagonist. In Experiments 2 and 3, participants were explicitly asked to view the text situation from the point of view of the protagonist. In this case, the goals of the reader and the protagonist should be the same. In these experiments, participants focused on the goals of the protagonist only when those goals had not been satisfied from the perspective of the protagonist. These results are discussed in terms of reader- and character-based perspectives and in terms of text characteristics that cue perspective taking. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
3.
Andreas Pierratos Michaelene Ouwendyk Robert Franceur 《Hemodialysis international. International Symposium on Home Hemodialysis》1997,1(1):32-35
In order to provide a highly efficient, long-duration form of hemodialysis, we developed nocturnal hemodialysis. Patients were dialyzed nightly at home for 8 – 10 hours, 6 – 7 nights/week. We kept the dialysate flow at 100 mL/min and the blood flow at 250 – 300 mL/min. Patients were monitored remotely from the hospital through a computer connection. An internal jugular line was used as an access. We have trained 12 patients over 30 months and have accumulated 160 patient-months worth of data. The patients tolerated the dialysis very well and slept through the night. There was a significant improvement in their sense of well-being. Nightly Kt/V was 0.99. Weekly removal of phosphate was two times as high and β 2 -microglobulin four times as high as conventional hemodialysis. All patients have discontinued their phosphate binders and have increased their dietary phosphate and protein intake. Hypertension was controlled with fewer medications, and erythropoietin dosages decreased. Complications were infrequent and included catheter occlusion and infections. Reusing the dialyzers decreased the cost of the treatment to levels similar to continuous ambulatory peritoneal dialysis. Nocturnal hemodialysis represents a viable dialysis modality that combines high quality, low cost, and excellent tolerance. 相似文献
4.
5.
Many current implementations of protocols such as the Transmission Control Protocol/Internet Protocol (TCP/IP) are inefficient because data are often accessed more frequently than necessary. Three techniques that reduce the need for memory bandwidth are proposed. The techniques are copy-on-write, page remapping, and single-copy. Afterburner, a network-independent card that provides the services that are necessary for a single-copy protocol stack, is described. The card has 1 MByte of local buffers and provides a simple interface to a variety of network link adapters, including HIPPI and asynchronous transfer mode (ATM). Afterburner can support transfers to and from the link adapter card at rates up to 1 Gbit/s. An implementation of TCP/IP that uses the features provided by Afterburner to reduce the movement of data to a single copy is discussed. Measurements of the end-to-end performance of Afterburner and the single-copy implementation of TCP/IP are presented 相似文献
6.
S. F. Edwards 《Polymer International》1985,17(2):122-125
Elasticity is discussed as an aspect of viscoelasticity, which is described by the tube model. The effects of both crosslinks and entanglements contribute to this model and a discussion of how these effects can be quantified is given. At high enough concentration, entanglements ensure the existence of elastic effects even without crosslinks, and a theory is presented on how this dynamical phase change comes about. 相似文献
7.
8.
9.
Stolorow Robert D.; Atwood George E.; Orange Donna M. 《Canadian Metallurgical Quarterly》2006,23(1):184
In omitting crucial words and sentencees, neglecting relevant citations, and overlooking important distinctions, Jon Mills' (see record 2005-04819-001) critique of relational psychoanalysis significantly misrepresents the authors' viewpoint. This viewpoint seeks to contextualize, but not to nullify, individual worlds of experience and their limiting horizons. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
10.
Two lignite samples, Beulah No. 3 and Big Brown No. 1, were liquefied at 420 °C using H2 and synthesis gas to determine the optimum beneficial amount of H2S in the batch autoclave reactor. Under the conditions employed, 50–100 psi partial pressure of H2S, nominally 4–10 wt% of daf lignite, was optimum for both samples. Synthesis gas outperformed H2 with and without H2S for the liquefaction of the two coals. 相似文献