全文获取类型
收费全文 | 4603篇 |
免费 | 98篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 46篇 |
综合类 | 2篇 |
化学工业 | 871篇 |
金属工艺 | 80篇 |
机械仪表 | 78篇 |
建筑科学 | 192篇 |
矿业工程 | 24篇 |
能源动力 | 88篇 |
轻工业 | 409篇 |
水利工程 | 28篇 |
石油天然气 | 19篇 |
无线电 | 290篇 |
一般工业技术 | 679篇 |
冶金工业 | 1181篇 |
原子能技术 | 59篇 |
自动化技术 | 660篇 |
出版年
2022年 | 36篇 |
2021年 | 43篇 |
2019年 | 39篇 |
2018年 | 40篇 |
2017年 | 42篇 |
2016年 | 60篇 |
2015年 | 52篇 |
2014年 | 77篇 |
2013年 | 254篇 |
2012年 | 143篇 |
2011年 | 174篇 |
2010年 | 152篇 |
2009年 | 175篇 |
2008年 | 200篇 |
2007年 | 198篇 |
2006年 | 183篇 |
2005年 | 139篇 |
2004年 | 132篇 |
2003年 | 114篇 |
2002年 | 131篇 |
2001年 | 101篇 |
2000年 | 89篇 |
1999年 | 81篇 |
1998年 | 104篇 |
1997年 | 90篇 |
1996年 | 89篇 |
1995年 | 86篇 |
1994年 | 78篇 |
1993年 | 91篇 |
1992年 | 93篇 |
1991年 | 34篇 |
1990年 | 71篇 |
1989年 | 58篇 |
1988年 | 65篇 |
1987年 | 68篇 |
1986年 | 70篇 |
1985年 | 90篇 |
1984年 | 89篇 |
1983年 | 83篇 |
1982年 | 86篇 |
1981年 | 75篇 |
1980年 | 47篇 |
1979年 | 62篇 |
1978年 | 62篇 |
1977年 | 57篇 |
1976年 | 56篇 |
1975年 | 64篇 |
1974年 | 38篇 |
1973年 | 39篇 |
1972年 | 35篇 |
排序方式: 共有4706条查询结果,搜索用时 15 毫秒
31.
Ronald W. Rousseau James K. Ferrell Robert M. Kelly 《Chemical Engineering Communications》1985,34(1):27-35
Experience with the operation of a pilot-scale unit is used to outline potential difficulties in the operation of acid gas removal systems on gases produced from coal. The pilot plant has been used to condition gases produced from subbituminous coal, devolatilized char, peat and lignite. The solvent used in the acid gas removal system has been refrigerated methyl alcohol. Data from this study document accumulation of hydrocarbons, sulfur and nitrogen compounds, and mercury in the circulating solvent. 相似文献
32.
Disguise and the structured self-report assessment of psychopathology: I. An analogue investigation.
Explored the utility of disguise in structured self-report assessments of psychopathology in 3 experiments with 370 university students. Exp I used items from the Basic Personality Inventory (BPI); Exp II used the BPI, the Desirability scale of the Personality Research Form—Form E, and 4 criterion measures; and Exp III used 2 of the criterion measures and the BPI. Data indicate that under normal test-taking circumstances, the use of disguised test items was not advantageous. This relationship, however, was moderated by a number of dimensional parameters. When faking response sets in terms of desirability was induced, the use of disguised test item content was not useful. Data are interpreted in terms of the various strategies of test construction underlying the assessment of psychopathology. Results support a rational strategy of test construction emphasizing the use of relevant test item content. It is concluded that, in structured self-report assessments, the most valid results may be obtained through the use of direct questions with cooperative test respondents. (43 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
33.
WH Newman LM Zhang MR Castresana MG Currie BF Becker 《Canadian Metallurgical Quarterly》1994,54(18):1351-1356
Atrial natriuretic peptide (ANP) and sodium nitroprusside (SNP) increase cGMP in vascular smooth muscle cells and act as vasodilators in some, but not all, blood vessels. In this present study, we attempted to correlate the ability of these two agents to dilate blood vessels with the ability to increase cGMP in cultured vascular smooth muscle cells. In the isolated guinea pig heart, SNP dose-dependently increased coronary flow while ANP was ineffective. In smooth muscle cells cultured from the coronary system, SNP increased intracellular cGMP in a dose-dependent manner while ANP had no effect on cGMP in these cells. In isolated guinea-pig thoracic aorta, precontracted with K+, both ANP and SNP produced relaxation and ANP was the more potent. In smooth muscle cells cultured from the aorta, ANP and SNP increased cGMP and the potency relationship was similar to the intact vessel. These results support the view that phenotypic properties of vascular smooth muscle cells can account for differences in the response of blood vessels to vasodilators. 相似文献
34.
PD Currie 《Canadian Metallurgical Quarterly》1998,76(6):421-433
The Hedgehog family of secreted glycoproteins proteins plays multifarious roles during vertebrate embryogenesis. In both the Drosophila and vertebrate embryo correct deployment of Hedgehog-like proteins is critical for the generation of pattern in many tissues and organs. New evidence now reveals that genes involved in hedgehog signalling are mutated in a number of common human genetic disorders, including skin cancer and craniofacial defects. The understanding of how cells generate, receive and transduce the Hedgehog signal during development has led to the establishment of molecular paradigms for the pathogenesis of these diseases. These studies clearly illustrate that knowledge of the normal role of a gene during development is critical for generating an understanding of the disease state in which it is mutated. 相似文献
35.
36.
This paper describes experimental and numerical studies of heat transfer between surfaces in contact over a highly elliptical area in a gas or in vacuum. Measurements of the steady-state thermal resistance of a high aspect ratio contact formed between cylindrical steel surfaces with widely different radii of curvature (76 cm vs 0.95 cm) are reported for two levels of surface roughness (0.05 μm and 1.0 μm rms) and compared to 3-D numerical results obtained with the multigrid method. Theoretical results obtained by evaluating the contact conductance acting over each surface element within the contour area with a method developed previously for rough but nominally flat surfaces are shown to be in excellent agreement with the rough surface experimental data. 相似文献
37.
Responses ofRhagoletis pomonella (Walsh) (Diptera: Tephritidae) flies to host fruit visual stimuli (apples or models of apples) and chemical stimuli (synthetic apple volatile blend) were studied in semidwarf field-caged apple trees. Three different fruit or model densities (1, 4, or 16 fruit or models/ tree) and two odor release rates [ca. 0.7g/hr (close to the natural release rate of a ripe apple) and ca. 500g/hr (amount of odor released by commercially sold apple maggot traps)] were tested. Individually released flies were followed as they moved within a tree for a maximum of 20 min. We recorded three-dimensional search paths followed by foraging flies and computed such variables as total relative distance traveled before alighting on a fruit or model, track length between individual alightment sites, and directness of flight to fruits or models. Effect of odor on propensity to alight on fruit or models and host-searching behavior prior to alighting on fruit or on models varied according to fruit or model color and density. If the fruit visual stimulus was strong (e.g., red color), odor did not increase the probability of finding fruit or fruit models. As the visual stimulus became progressively weaker (red to green to clear), odor (irrespective of concentration) appeared to aid flies during the fruit-finding process. As density of fruit or models increased, the probability of flies finding a fruit or model also increased (e.g., 50% of flies found a red fruit model at 1 model/tree while 90% found a red model at 16 models/tree; 4% of flies found a clear model with odor at 1 model/tree while 35% found a clear model with odor at 16 models/tree). Findings reported elsewhere indicate thatR. pomonella flies are able to discover a point source of odor (an odor-bearing tree in a patch of trees) by flying upwind (in the tree patch) in response to intermittent exposure to odor. Findings here indicate that after arrival on a host tree (point source), flies discover individual apparent and abundant host fruit on the basis of vision. If fruit are less apparent or scarce, odor appears to interact with vision during the fruit-finding process. 相似文献
38.
Ronald R. Yager 《国际智能系统杂志》2014,29(10):881-905
Our interest is in the problem of comparing alternatives with uncertain payoffs when the uncertainty is represented using a measure. We first describe various aspects of the use of a measure to represent uncertainty. We recall that probability is a special well‐understood example of measure‐based uncertainty. We note that stochastic dominance provides a well‐established method for comparing alternatives in the case of probabilistic uncertainty. Inspired by this we develop an extension of the use of stochastic dominance for comparing uncertainty profiles to the case where the uncertainty is represented by a measure. We refer to this as measure based stochastic dominance. Do to the fact that in most cases a stochastic dominance relationship does not exist between alternatives this requires us to consider the use of surrogates for measure based stochastic dominance to compare alternatives. Here we investigate a class of surrogates for measure based stochastic dominance that we call Measure Weighted Means (MWM). As we see these MWM are numeric values consistent with measure based stochastic dominance. 相似文献
39.
A detailed investigation of the seed oil ofByrsocarpus coccineus Schum. and Thonn. has disclosedcis-11,12-methyleneoctadecanoic (lactobacillic) (13%) and two branched octadecenoic acids (0.1%). Other fatty acids in the oil
are those normally associated with seed lipids except for an unusually high proportion (12%) ofcis-11-octadecenoic acid. Lactobacillic acid has long been known as a constituent of certain bacterial lipids, but this is the
first report of its presence in a seed oil. The branched olefinic acids have not heretofore been found to occur in plants.
Mention of firm names or trade products does not imply endorsement or recommendation by the Department of Agriculture over
other firms or similar products not mentioned. 相似文献
40.
The action of the tumor promoter, phorbol 12,13-dibutyrate (PDBu), on rabbit peritoneal and human neutrophils is associated
with stimulation of14C-arachidonic acid incorporation into phospholipids within 1–2 min. Stimulated14C-arachidonate incorporation was relatively selective for phosphatidylinositol (PI) in rabbit neutrophils. In contrast, the
secretory response of human neutrophils to PDBu coincided with stimulated label incorporation into phosphatidylserine (PS),
phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidic acid (PA) and PI. Significant increases in label incorporation
were observed with PDBu concentrations as low as 2 nM, and the dose response of stimulated label incorporation paralleled
that of evoked lysozyme secretion. A parallel, but partial, inhibition of PDBu-stimulated PI labeling and enzyme release was
observed after exposing rabbit neutrophils to calcium-deprived medium, whereas calcium deprivation failed to significantly
depress either of these stimulant actions of PDBu in human neutrophils. Further, in rabbit neutrophils PDBu elicited an increase
in cell associated45Ca. However, PDBu was unable to promote the incorporation of32P orthophosphate into PI or enhance phospholipase A2 activity in broken cells. These findings suggest that one expression of the interaction between phorbol esters and their
receptors on neutrophils involves the turnover of arachidonic acid in phospholipids. This stimulated turnover of arachidonate
may be a critical step in the cascade of events associated with neutrophil activation. 相似文献