全文获取类型
收费全文 | 2230篇 |
免费 | 58篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 33篇 |
综合类 | 1篇 |
化学工业 | 714篇 |
金属工艺 | 46篇 |
机械仪表 | 39篇 |
建筑科学 | 80篇 |
矿业工程 | 2篇 |
能源动力 | 70篇 |
轻工业 | 176篇 |
水利工程 | 12篇 |
石油天然气 | 6篇 |
无线电 | 221篇 |
一般工业技术 | 403篇 |
冶金工业 | 216篇 |
原子能技术 | 16篇 |
自动化技术 | 254篇 |
出版年
2022年 | 32篇 |
2021年 | 44篇 |
2020年 | 13篇 |
2019年 | 19篇 |
2018年 | 33篇 |
2017年 | 36篇 |
2016年 | 42篇 |
2015年 | 19篇 |
2014年 | 54篇 |
2013年 | 109篇 |
2012年 | 90篇 |
2011年 | 113篇 |
2010年 | 83篇 |
2009年 | 105篇 |
2008年 | 98篇 |
2007年 | 99篇 |
2006年 | 82篇 |
2005年 | 70篇 |
2004年 | 62篇 |
2003年 | 63篇 |
2002年 | 78篇 |
2001年 | 36篇 |
2000年 | 38篇 |
1999年 | 41篇 |
1998年 | 57篇 |
1997年 | 54篇 |
1996年 | 50篇 |
1995年 | 40篇 |
1994年 | 35篇 |
1993年 | 36篇 |
1992年 | 31篇 |
1991年 | 34篇 |
1990年 | 36篇 |
1989年 | 29篇 |
1988年 | 24篇 |
1987年 | 27篇 |
1986年 | 25篇 |
1985年 | 42篇 |
1984年 | 34篇 |
1983年 | 19篇 |
1982年 | 26篇 |
1981年 | 20篇 |
1980年 | 17篇 |
1979年 | 29篇 |
1978年 | 23篇 |
1977年 | 24篇 |
1976年 | 22篇 |
1975年 | 22篇 |
1974年 | 14篇 |
1973年 | 18篇 |
排序方式: 共有2289条查询结果,搜索用时 15 毫秒
21.
Jacques Auger Chantal Lecomte Jacky Paris Eric Thibout 《Journal of chemical ecology》1989,15(4):1391-1398
Acrolepiopsis assectella andPlutella xylostella frass volatiles, trapped on Tenax GC, were examined by capillary gas chromatography. In both moths, the same three disulfides, dimethyl, dipropyl, and methyl propyl, were the most abundant substances, but in different proportions. The synthetic disulfides elicited the same behavioral response by the parasitoid,Diadromus pulchellus as frass. The plant origin of these substances is discussed. 相似文献
22.
Jacques Jupille Anne-Marie Flank Pierre Lagarde 《Journal of the American Ceramic Society》2002,85(5):1041-1046
The local structure centered on sodium after diffusion in silica (Na-SiO2 samples) has been determined by means of extended X-ray absorption fine structure (EXAFS) studies. The Na-SiO2 samples are of particular interest because (i) their sodium content can be varied over a wide range of concentration and (ii) their local structure is representative of that of soda–silica glass. EXAFS analyses reveal the existence of a well-defined local structure involving oxygen, sodium, and silicon neighbors. The Na-O, Na-Na, and Na-Si bonds lengths, which amount to 0.23, 0.30, and 0.38 nm, respectively, do not depend on sodium concentration. This environment closely resembles that found in soda–silica glass. Moreover, it is compatible with the "target site" and "the site memory effect" suggested by recent theories of the ionic conductivity in oxide glasses. 相似文献
23.
Verhelst SH Michiels PJ van der Marel GA van Boeckel CA van Boom JH 《Chembiochem : a European journal of chemical biology》2004,5(7):937-942
Aminoglycoside antibiotics, which are able to selectively bind to RNA, are considered to be an important lead in RNA-targeting drug discovery. In this study, surface plasmon resonance (SPR) was employed to explore the interaction of aminoglycosides with known tobramycin-binding RNA hairpins (aptamers) and an unrelated RNA hairpin. It was established that aminoglycosides have multiple interactions with RNA hairpins. Unexpectedly, the different hairpins showed comparable affinity for a set of related aminoglycosides. The observed absence of selectivity presents an extra hurdle in the discovery of novel aminoglycosides as specific drugs that target defined RNA hairpins. 相似文献
24.
The Resource Constrained Project Scheduling Problem is one of the most intensively investigated scheduling problems. It requires scheduling a set of interrelated activities, while considering precedence relationships, and limited renewable resources allocation. The objective is to minimize the project duration. We propose a new destructive lower bound for this challenging ${\mathcal {NP}}$ -hard problem. Starting from a previously suggested LP model, we propose several original valid inequalities that aim at tightening the model representation. These new inequalities are based on precedence constraints, incompatible activity subsets, and nonpreemption constraints. We present the results of an extensive computational study that was carried out on 2,040 benchmark instances of PSPLIB, with up to 120 activities, and that provide strong evidence that the new proposed lower bound exhibits an excellent performance. In particular, we report the improvement of the best known lower bounds of 5 instances. 相似文献
25.
Chateau Marie-Elise Galet Laurence Soudais Yannick Fages Jacques 《Journal of surfactants and detergents》2004,7(4):355-362
A new test was developed to assess the efficiency of no-wiping hard-surface cleaning. The test allows cleaner comparisons
according to their ability to remove greasy soils. The chosen approach minimizes the mechanical forces applied while cleaning
so that the interactions between a detergent solution and the soil to be removed can be characterized. For this, immersion
cleaning was chosen, with coated stainless steel as substrate and pigmented oils as the model soil. Several parameters were
studied in defined ranges using the Experimental Design method and systematic comparisons. The test shows high reliability
on degreasing assessments and is there-fore especially suited to optimization of nonionic surfactant mixes. The originality
of the test lies in the possibility of keeping a visual trace of the cleaned substrate appearance by imprinting it on a piece
of paper. The validation of the test leads to corroboration of several practical observations. Temperature and agitation play
a major role in cleaning efficiency. Detergent solution concentration is a more relevant parameter than pH. Sodium carbonate
is shown to have a higher buffering effect than pentahydrated sodium metasilicate. The test is easy to set up, highly sensitive,
and can be adapted to solve the problems encountered by formulators of detergent cleaners, such as screening the best ethoxylated
fatty alcohol mix for better degreasing properties. 相似文献
26.
Corinne Leprince Eric Vivier Dominique Treton Pierre Galanaud Jacques Benveniste Yolande Richard Yolene Thomas 《Lipids》1991,26(12):1204-1208
The role of paf-acether (paf), a phospholipid cytokine, in the modulation of human B cell function was investigated. Paf,
from 1×10−5 M to 10−6 M, decreased B cell proliferation induced by both phorbol myristate acetate (PMA) and anti-IgM antibodies (anti-IgM Ab).
By contrast, 1×10−7 M to 1×10−9 M paf enhanced PMA triggered, but not anti-IgM triggered B cell proliferation. B cell proliferation was modulated between
24 and 72 hr of culture indicating that the effect of paf did not merely reflect a shift in proliferation kinetics. Interestingly,
paf also enhanced the spontaneous proliferation of a Burkitt lymphoma-derived B cell line, Raji, which suggests that paf can
directly act on B cells. The modulatory effect of paf on peripheral blood B cells was independent of PMA concentration, yet
the effect on Raji cells was dependent upon cell density. The data suggest that paf is a potent modulator of B cell function,
and may be involved in the control of humoral immune response.
Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl
Ether Lipids, Tokyo, Japan, May 1989. 相似文献
27.
The telomerization of dimethylaminoethyl methacrylate (DMAEMA) with mercaptoethanol initiated by 2,2′-azobisisobutyronitrile was first investigated at 70 °C and the influence of the type of solvent was studied. The results showed that well-defined telomers of DMAEMA could not be synthetized via telomerization of DMAEMA in water or water/acetonitrile mixture since the telomerization reaction is in competition with the nucleophilic addition of thiol onto the monomer. Transfer constants for mercaptoethanol in benzene and acetonitrile were determined by Mayo's and O'Brien's methods. The transfer constant obtained in acetonitrile (0,6) was higher than that obtained in benzene. This difference can be explained by the fact that the thiol was consumed by two reactions: nucleophilic addition and telomerization. The influence of solvents on the polymerization kinetics was enlightened. These results were applied to the synthesis of macromonomers of DMAEMA with isocyanatoethyl methacrylate (IEM). These macromonomers were copolymerized with styrene. 相似文献
28.
Jacques Teghem Daniel Tuyttens 《International Transactions in Operational Research》2014,21(6):871-898
We consider a one machine scheduling model, minimizing a classical objective function—either the total completion time or the maximum tardiness—and with two sets of jobs: one with initial jobs already scheduled and one with new jobs that must be inserted in the schedule. As such rescheduling can create a modification of the schedule of the initial jobs, a disruption objective is considered in addition to the original objective. This additional objective can be formulated in four different ways. Such model has been introduced by Hall and Potts, minimizing either a linear aggregation of the two objectives or the initial objective under a constraint giving an upper limit of the disruption objective. In this paper, the aim is to obtain the set of efficient schedules in regard to the two objectives. Algorithms are provided for the eight possible bi‐objective problems and illustrated by some didactic examples. 相似文献
29.
30.
Simple thermodynamic relationships as well as semiempirical solubility parameter plotting techniques were examined as methods for predicting critical crazing strains of polycarbonate exposed to linear and branched alkanes. In general, measured critical strains correlated with predicted solubilities based on the Flory–Huggins equation. Solubility parameters could also be used to predict critical strains if molecular size differences between specific alkanes were taken into account. These techniques were then extended to polar and hydrogen bonding liquids using two-dimensional solubility parameter plotting representations. A comprehensive listing of critical strains for polycarbonate exposed to over 80 liquids and liquid mixtures is included. 相似文献