全文获取类型
收费全文 | 5701篇 |
免费 | 208篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 76篇 |
综合类 | 3篇 |
化学工业 | 1211篇 |
金属工艺 | 86篇 |
机械仪表 | 87篇 |
建筑科学 | 188篇 |
矿业工程 | 7篇 |
能源动力 | 137篇 |
轻工业 | 590篇 |
水利工程 | 64篇 |
石油天然气 | 16篇 |
无线电 | 381篇 |
一般工业技术 | 1024篇 |
冶金工业 | 1381篇 |
原子能技术 | 49篇 |
自动化技术 | 618篇 |
出版年
2023年 | 36篇 |
2022年 | 76篇 |
2021年 | 119篇 |
2020年 | 89篇 |
2019年 | 83篇 |
2018年 | 125篇 |
2017年 | 95篇 |
2016年 | 116篇 |
2015年 | 76篇 |
2014年 | 135篇 |
2013年 | 310篇 |
2012年 | 261篇 |
2011年 | 326篇 |
2010年 | 232篇 |
2009年 | 242篇 |
2008年 | 288篇 |
2007年 | 281篇 |
2006年 | 221篇 |
2005年 | 208篇 |
2004年 | 203篇 |
2003年 | 183篇 |
2002年 | 185篇 |
2001年 | 117篇 |
2000年 | 94篇 |
1999年 | 95篇 |
1998年 | 163篇 |
1997年 | 122篇 |
1996年 | 111篇 |
1995年 | 94篇 |
1994年 | 92篇 |
1993年 | 91篇 |
1992年 | 76篇 |
1991年 | 55篇 |
1990年 | 61篇 |
1989年 | 63篇 |
1988年 | 70篇 |
1987年 | 57篇 |
1986年 | 67篇 |
1985年 | 68篇 |
1984年 | 52篇 |
1983年 | 49篇 |
1982年 | 41篇 |
1981年 | 48篇 |
1980年 | 28篇 |
1979年 | 35篇 |
1978年 | 27篇 |
1977年 | 34篇 |
1976年 | 40篇 |
1975年 | 18篇 |
1974年 | 21篇 |
排序方式: 共有5918条查询结果,搜索用时 15 毫秒
21.
Chul-Kun Cho Kil Sang Chang Timothy S. Cale 《Korean Journal of Chemical Engineering》1993,10(4):195-202
Magnetic crystallite thermometry has been used to measure the average nickel crystallite temperature in packed bed reactors
during ethane hydrogenolysis, an exothermic reaction. The technique is based on the temperature dependence of the magnetic
moment of dispersed nickel catalysts. Measurement of the average catalyst temperature is very useful for reactor control because
of its shorter time constant compared with exit fluid temperature. Bed temperature control based on the exit fluid temperature,
which has often been used as a control variable, is too slow to protect thermal runaway of the bed. The advantage of short
time constant by measuring the average catalyst temperature has been incorporated with enhanced feedback control system to
control the bed temperature and prevent the thermal runaway of the catalyst bed. An enhanced feedback control structure with
supervisory action performed better than the classical proportional-integral control in runaway prevention when the two control
schemes were compared with each other on the basis of the trippoint (incipient thermal runaway). 相似文献
22.
23.
A 38-year-old woman was transmitted to hospital with profuse vaginal bleeding. The origin of the vaginal injuries (resulting from "normal" sexual intercourse vs. use of instruments for manipulation in the vagina) was obscure. The wound pattern is presented and the literature on the subject is reviewed with special reference to predisposing factors and genesis of coital injuries. Concerning the wound pattern, reflecting a blunt trauma, a manipulation with a (so far unknown) instrument, but also with finger or hand could not be proved with the required certainty. In the presented case the origin of the vaginal injuries from "normal" sexual intercourse as described by the accused man could not be excluded. 相似文献
24.
Traits, as sets of behaviors, can provide a good mechanism for reusability. However, they are limited in important ways and are not present in widely used programming and modeling languages and hence are not readily available for use by mainstream developers. In this paper, we add UML associations and other modeling concepts to traits and apply them to Java and C++ through model-driven development. We also extend traits with required interfaces so dependencies at the semantics level become part of their usage, rather than simple syntactic capture. All this is accomplished in Umple, a textual modeling language based upon UML that allows adding programming constructs to the model. We applied the work to two case studies. The results show that we can promote traits to the modeling level along with the improvement in flexibility and reusability. 相似文献
25.
Transforming smoothers are known as a successful approach to the multigrid treatment of saddlepoint problems resulting from variational problems. In this paper we analyze similar multigrid methods in the context of the practically important class of optimization problems with partial differential equation constraint, which lead to a different kind of saddle point problems. We prove level independent convergence properties for the resulting multigrid methods and demonstrate this also in numerical investigations for a relevant model problem. 相似文献
26.
Forty-four patients suffering from acute and chronic schizophrenic psychoses were used to obtain, by using Lorr's scale (IMPS) and taking the changes in disease state observed within three months as a base, suggestions or pointers as to the proper treatment of disease with fluphenazine (lyorodin) which is a neuroleptically highly potent phenothiazine derivative. Megalomania, grandiose delusions apathetic and depressive syndromes showed marked tendencies toward major improvement. An "antiautistic" effect was observed in chronic patients. The effective dose was between 6 and 12 mg a day. The drug was well tolerated. In the majority of cases it was also necessary for antiparkinsonian drugs to be administered to patients. After twelve months of treatment, slight to major improvements or even freedom from symptoms could be observed in 28 cases (or 64%). 相似文献
27.
John E. Rash Timothy J. A. Johnson C. Sue Hudson F. Dennis Giddings William F. Graham Mohyee E. Eldefrawi 《Journal of microscopy》1982,128(2):121-138
Three methods are described for direct post-fracture, post-shadow labelling of individual classes of intramembrane particles (IMPs) in freeze-fracture replicas of biological membranes. The P-face IMPs corresponding to the acetylcholine receptor complexes (AChRs) of vertebrate neuroeffector junctions are identified by post-replication labelling with ferritin-antibody complexes and with neurotoxin-biotin-avidin-colloidal gold affinity ligands. (The freeze-etch nomenclature of Branton et al., 1975, is used in this report.) These post-shadow labelling techniques resemble conventional en bloc labelling techniques except that the labelling reagents must penetrate a thin but discontinuous layer of platinum superimposed on the molecules of interest. In the ‘sectioned labelled-replica technique’, the replicated and labelled tissues are stained, embedded in plastic and sectioned parallel to the replica-tissue interfaces. In the direct ‘labelled-replica techniques’, the replicated and labelled samples are freeze-dried or critical point dried, the labelled surfaces are stabilized by carbon coating, and the underlying tissues are dissolved, allowing the labelled-replicas to be examined as conventional freeze-fracture replicas. The unshadowed side of each AChR IMP is shown to retain sufficient biochemical information to permit both immunospecific and neurotoxin specific labelling despite formaldehyde fixation, freezing, fracturing, platinum shadowing, and thawing in aqueous media. A new mixed ferricyanide-osmium staining method reveals electron opaque structures spanning the membrane bilayer in the same size, number and distribution as the labelled IMPs. These experiments demonstrate the feasibility of identifying individual IMPs in freeze-fracture replicas and may allow the identification of specific membrane lesions in human disease. 相似文献
28.
The five articles that make up the bulk of this special issue collectively illustrate new methods for examining the utility of sub-test and scale-level profile analysis. By necessity they are preliminary, but they illustrate methods that may indeed prove useful and may help resolve this divide between research and practice. This special issue grew out of a symposium conceived and organized by Cecil Reynolds at the American Psychological Association in 1998. The articles and one of the commentaries in this special issue are extensions of that symposium. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
29.
The bioanode is the defining feature of microbial fuel cell (MFC) technology and often limits its performance. In the current work, we report the engineering of a novel hierarchically porous architecture as an efficient bioanode, consisting of biocompatible chitosan and vacuum-stripped graphene (CHI/VSG). With the hierarchical pores and unique VSG, an optimized bioanode delivered a remarkable maximum power density of 1530 mW m(-2) in a mediator-less MFC, 78 times higher than a carbon cloth anode. 相似文献
30.