全文获取类型
收费全文 | 1008篇 |
免费 | 31篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 7篇 |
综合类 | 3篇 |
化学工业 | 321篇 |
金属工艺 | 14篇 |
机械仪表 | 11篇 |
建筑科学 | 58篇 |
矿业工程 | 2篇 |
能源动力 | 27篇 |
轻工业 | 219篇 |
水利工程 | 10篇 |
石油天然气 | 3篇 |
无线电 | 37篇 |
一般工业技术 | 151篇 |
冶金工业 | 83篇 |
原子能技术 | 4篇 |
自动化技术 | 90篇 |
出版年
2024年 | 3篇 |
2023年 | 5篇 |
2022年 | 17篇 |
2021年 | 55篇 |
2020年 | 11篇 |
2019年 | 18篇 |
2018年 | 16篇 |
2017年 | 18篇 |
2016年 | 27篇 |
2015年 | 22篇 |
2014年 | 26篇 |
2013年 | 94篇 |
2012年 | 55篇 |
2011年 | 64篇 |
2010年 | 46篇 |
2009年 | 38篇 |
2008年 | 53篇 |
2007年 | 49篇 |
2006年 | 47篇 |
2005年 | 43篇 |
2004年 | 31篇 |
2003年 | 28篇 |
2002年 | 35篇 |
2001年 | 6篇 |
2000年 | 17篇 |
1999年 | 13篇 |
1998年 | 20篇 |
1997年 | 13篇 |
1996年 | 13篇 |
1995年 | 13篇 |
1994年 | 14篇 |
1993年 | 15篇 |
1992年 | 9篇 |
1991年 | 8篇 |
1990年 | 8篇 |
1989年 | 4篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 7篇 |
1985年 | 4篇 |
1983年 | 3篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1978年 | 6篇 |
1977年 | 7篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1955年 | 3篇 |
1942年 | 3篇 |
1917年 | 3篇 |
排序方式: 共有1040条查询结果,搜索用时 15 毫秒
41.
Rajendra P. Maskey Ines Kock Mohamed Shaaban Iris Grün-Wollny Elisabeth Helmke Frank Mayer Irene Wagner-Döbler Hartmut Laatsch 《Polymer Bulletin》2002,49(2-3):87-93
Summary
A new group of low-molecular weight channel-forming oligo(hydroxybutyric acids) (cPHBs, 1 with n = 8–30; main component MW ≈ 1300 dalton) was isolated from microorganisms of different origin. Inclusion bodies were
electron-microscopically visible in cells in the state of autolysis, not in cells in the exponential phase of growth. cPHB
and high-molecular poly(l3-hydroxybutyric acid) (sPHB) is cleaved by phenylethylamine and forms the corresponding monomeric
hydroxybutyramide and – under drastic conditions, the crotylamide. One of these compounds, the 3-hydroxy-N-phenethyl-butyramide
(5), was isolated as a new natural product now.
Received: 28 March 2002/Revised version: 26 July 2002/ Accepted: 26 July 2002
RID="*"
ID="*"Marine Bakterien, XVII. XVI: R.P. Maskey, R.N. Asolkar, E. Helmke, and H. Laatsch, Chalcomycin B, a new antibiotic from
a marine Streptomyces sp. B7064. J. Antibiot., submitted 2002
Correspondence to Hartmut Laatsch, e-mail: hlaatsc@gwdg.de, Fax: +49-551-399660 相似文献
42.
Addicks E Mazitschek R Giannis A 《Chembiochem : a European journal of chemical biology》2002,3(11):1078-1088
Integrins, a widely expressed family of heterodimeric cell surface adhesion proteins, are expressed in a variety of cell types. They play a decisive role in cell-cell adhesion or cell to extracellular matrix adhesion events. Antagonists of alpha(v)beta(3) or alpha(IIb)beta(3) integrin may have a potential use in suppression of pathological processes. We present the synthesis of novel tricyclic benzodiazepinedione-based RGD analogues, which were subsequently tested in a solid-phase receptor assay in order to investigate their binding affinities towards alpha(v)beta(3) and alpha(IIb)beta(3) integrin. 相似文献
43.
Westerhausen René; Woerner Wolfgang; Kreuder Frank; Schweiger Elisabeth; Hugdahl Kenneth; Wittling Werner 《Canadian Metallurgical Quarterly》2006,20(3):272
The objective of the present study was to examine the role of the corpus callosum (CC) in dichotic listening. For this purpose, 40 right-handed healthy male participants were assessed with morphological and diffusion tensor imaging, which yielded macrostructural (midsagittal area) and microstructural (mean diffusion, fractional anisotropy) measures of the total CC and predefined subregions. Applying the standard consonant-vowel Bergen Dichotic Listening Test (including 3 different attentional instructions), the authors found dichotic listening performance to be substantially related to the integrity of the CC at both macro- and microstructural levels. Results indicate a dual role of the CC; it is relevant not only for the stimulus-driven (bottom-up) transfer of left-ear input to the left hemisphere but also for its attentional (top-down) modulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
44.
Elisabeth 《Data & Knowledge Engineering》2002,41(2-3):247-272
Natural language and databases are core components of information systems. They are related to each other because they share the same purpose: the conceptualization aspects of the real world in order to deal with them in some way. Natural language processing (NLP) techniques may substantially enhance most phases of the information system lifecycle, starting with requirements analysis, specification and validation, and going up to conflict resolution, result processing and presentation. Furthermore, natural language based query languages and user interfaces facilitate the access to information for anyone and allow for new paradigms in the usage of computerized services. This paper investigates the use of NLP techniques in the design phase of information systems. Then, it reports on data base querying and information retrieval enhanced with NLP. 相似文献
45.
Ana Celia Mota Elisabeth Dumont James L. Smith 《Journal of Low Temperature Physics》1999,117(5-6):1477-1481
We have found a sharp transition at T
c2
= 350 mK in the vortex creep rate of a single crystal of (U
1–x
Th
x
)Be
13
with T
c
= 523 mK (x = 0.0275). For T T
c2
, no creep of vortices is observed in a time scale of 105
s, while for T
c2
< T < T
c
, vortices creep at very high rates (30% of decay from a metastable configuration in the first 105
s at T = 400 mK). The sharp transition occurs at the same temperature at which the second jump in the specific heat appears in these samples. Similar low levels of creep rates have been reported by us in the low–T superconducting phase of UPt
3.1 相似文献
46.
Elisabeth Blickstad 《Food microbiology》1984,1(3):177-185
The water activity (aw) of a cured minced meat mixture was reduced with NaCl or glycerol + NaCl and the products stored in air, N2 or CO2 at 4°C. The lower the aw, the lower was the growth rate of the total microflora except when aw was reduced below 0·98 with glycerol and products were stored in CO2, when the growth rate was independent of aw. At aw 0·94 NaCl was more effective than glycerol + NaCl in reducing the growth rate. In air the final microflora of products stored at aw ≤0·96 consisted primarily of yeasts while at 0.98 aw, both Lactobacillus (62%) and yeasts (38%) were found. In CO2 and N2Lactobacillus predominated at 0·94–0·98 aw when 2% NaCl or NaCl + glycerol were used. At 0·94 aw, produced using 6% NaCl, a heterogenous final microflora was found, including Micrococcus and Staphylococcus. An increase in the microbial shelf-life of meat products may be obtained by reducing the aw, particularly for use with storage in N2- and CO2-atmospheres. The type of solute chosen to regulate aw may affect the solubility of CO2, which in turn affects the shelf-life. 相似文献
47.
Elisabeth Chassaing Nicolas Portail Anne-france Levy Guillaume Wang 《Journal of Applied Electrochemistry》2004,34(11):1085-1091
Ni–Mo nanocrystalline layers were electrodeposited using direct current from citrate–ammonia solutions. The quartz crystal microbalance investigation confirms that the discharge process starts with hydrogen evolution before the onset of the alloy deposition. The grain size was estimated from X-ray line broadening. It decreases when the molybdenum content is increased. It is smaller for layers deposited at pH 9.5 than 8.5. The microhardness exhibits a maximum close to 800 Vickers for Mo around 17 wt%. For higher Mo a softening is observed showing a deviation from Hall-Petch behaviour due to small grain size. In deaerated hydrochloric solutions, the layers show a large passivation domain without any pitting. The corrosion currents as well as the passivation currents, higher than for the bulk Hastelloy B alloy, decrease when Mo is increased. 相似文献
48.
Advanced sludge treatment affects extracellular polymeric substances to improve activated sludge dewatering 总被引:41,自引:0,他引:41
The management of wastewater sludge, now often referred to as biosolids, accounts for a major portion of the cost of the wastewater treatment process and represents significant technical challenges. In many wastewater treatment facilities, the bottleneck of the sludge handling system is the dewatering operation. Advanced sludge treatment (AST) processes have been developed in order to improve sludge dewatering and to facilitate handling and ultimate disposal. The authors have extensively reported lab-scale, semi-pilot and pilot investigations on either thermal and thermochemical processes, or chemical oxidation using hydrogen peroxide. To understand the action of these advanced sludge technologies, the essential role played by extracellular polymeric substances (EPS) needs to be understood. EPS form a highly hydrated biofilm matrix, in which the micro-organisms are embedded. Hence they are of considerable importance in the removal of pollutants from wastewater, in bioflocculation, in settling and in dewatering of activated sludge. The present paper reviews the characteristics of EPS and the influence of thermochemical and oxidation mechanisms on degradation and flocculation of EPS. Experimental investigations on waste activated sludge are conducted by the authors to evaluate the various literature findings. From the experiments, it is concluded that AST methods enhance cake dewaterability in two ways: (i) they degrade EPS proteins and polysaccharides reducing the EPS water retention properties; and (ii) they promote flocculation which reduces the amount of fine flocs. 相似文献
49.
This work presents a simple microfluidic device with an integrated thin-film heater for studies of DNA hybridization kinetics and double-stranded DNA melting temperature measurements. The heating characteristics of the device were evaluated with a novel, noninvasive indirect technique using molecular beacons as temperature probes inside reaction chambers. This is the first microfluidic device in which thermal dehybridization of surface-bound oligonucleotides was performed for measurement of double-stranded DNA melting temperatures with +/- 1 degrees C precision. Surface modification and oligonucleotide immobilization were performed by continuously flowing reagents through the microchannels. The resulting reproducibility of oligonucleotide surface densities, at 9% RSD, was better than for the same modification chemistries on glass slides in unstirred reagent solutions (RSD=20%). Moreover, the surface density of immobilized DNA probe molecules could be varied controllably by changing the concentration of the reagent solution used for immobilization. Thus, excellent control of surface characteristics was made possible, something which is often difficult to achieve with larger devices. Solid-phase hybridization reactions, a fundamental aspect of microarray technologies often taking several hours in conventional systems, were reduced to minutes in this device. It was also possible to determine forward rate constants for hybridization, k. These varied from 820,000 to 72,000 M(-1) s(-1), decreasing as surface densities increased. Surface densities could therefore be optimized to obtain rapid hybridization using such an approach. Taken together, this combined microfluidic/small-volume heating approach represents a powerful tool for surface-based DNA analysis. 相似文献
50.
McDonnell LA Mize TH Luxembourg SL Koster S Eijkel GB Verpoorte E de Rooij NF Heeren RM 《Analytical chemistry》2003,75(17):4373-4381
It is well known in secondary ion mass spectrometry (SIMS) that sample topography leads to decreased mass resolution. Specifically, the ion's time of flight is dependent on where it was generated. Here, using matrix-enhanced SIMS, it is demonstrated that, in addition to increasing the yield of intact pseudomolecular ions, the matrix allows the user to semiquantitatively record the topography of a sample. Through mapping the topography-related mass shifts of the matrix (which leads to decreased mass resolution), the analogous mass shifts of higher mass ions can be deconvoluted and higher resolution and greater sensitivity obtained. Furthermore, the semiquantitative topographical map obtained can be compared with any chemical images obtained, allowing the user to quickly ascertain whether local intensity maximums are due to topological features or represent genuine features of interest. 相似文献