全文获取类型
收费全文 | 3728篇 |
免费 | 44篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 27篇 |
综合类 | 10篇 |
化学工业 | 332篇 |
金属工艺 | 26篇 |
机械仪表 | 60篇 |
建筑科学 | 100篇 |
矿业工程 | 15篇 |
能源动力 | 55篇 |
轻工业 | 209篇 |
水利工程 | 9篇 |
石油天然气 | 5篇 |
武器工业 | 1篇 |
无线电 | 256篇 |
一般工业技术 | 301篇 |
冶金工业 | 2052篇 |
原子能技术 | 19篇 |
自动化技术 | 305篇 |
出版年
2022年 | 19篇 |
2021年 | 15篇 |
2020年 | 16篇 |
2019年 | 17篇 |
2018年 | 15篇 |
2017年 | 21篇 |
2016年 | 18篇 |
2015年 | 30篇 |
2014年 | 33篇 |
2013年 | 90篇 |
2012年 | 55篇 |
2011年 | 59篇 |
2010年 | 59篇 |
2009年 | 50篇 |
2008年 | 59篇 |
2007年 | 74篇 |
2006年 | 67篇 |
2005年 | 100篇 |
2004年 | 44篇 |
2003年 | 59篇 |
2002年 | 45篇 |
2001年 | 55篇 |
2000年 | 51篇 |
1999年 | 97篇 |
1998年 | 609篇 |
1997年 | 369篇 |
1996年 | 251篇 |
1995年 | 145篇 |
1994年 | 131篇 |
1993年 | 127篇 |
1992年 | 26篇 |
1991年 | 48篇 |
1990年 | 35篇 |
1989年 | 47篇 |
1988年 | 66篇 |
1987年 | 45篇 |
1986年 | 41篇 |
1985年 | 60篇 |
1984年 | 27篇 |
1983年 | 31篇 |
1982年 | 35篇 |
1981年 | 51篇 |
1980年 | 39篇 |
1979年 | 24篇 |
1978年 | 18篇 |
1977年 | 73篇 |
1976年 | 150篇 |
1975年 | 18篇 |
1973年 | 21篇 |
1966年 | 15篇 |
排序方式: 共有3782条查询结果,搜索用时 31 毫秒
71.
D Morgan L Turnpenny J Goodship W Dai K Majumder L Matthews A Gardner G Schuster L Vien W Harrison FF Elder M Penman-Splitt P Overbeek T Strachan 《Canadian Metallurgical Quarterly》1998,20(2):149-156
A DNA fragment containing the recA gene of Gluconobacter oxydans was isolated and further characterized for its nucleotide sequence and ability to functionally complement various recA mutations. When expressed in an Escherichia coli recA host, the G. oxydans recA protein could efficiently function in homologous recombination and DNA damage repair. The recA gene's nucleotide sequence analysis revealed a protein of 344 amino acids with a molecular mass of 38 kDa. We observed an E. coli-like LexA repressor-binding site in the G. oxydans recA gene promoter region, suggesting that a LexA-like mediated response system may exist in G. oxydans. The expression of G. oxydans recA in E. coli RR1, a recA+ strain, surprisingly caused a remarkable reduction of the host wild-type recA gene function, whereas the expression of both Serratia marcescens recA and Pseudomonas aeruginosa recA gene caused only a slight inhibitory effect on function of the host wild-type recA gene product. Compared with the E. coli RecA protein, the identity of the amino acid sequence of G. oxydans RecA protein is much lower than those RecA proteins of both S. marcescens and Pseudomonas aeruginosa. This result suggests that the expression of another wild-type RecA could interfere with host wild-type recA gene's function, and the extent of such an interference is possibly correlated to the identity of the amino acid sequence between the two classes of RecA protein. 相似文献
72.
W. Jill Harrison K. R. Pearson Alan A. Powell E. John Small 《Computational Economics》1994,7(3):203-223
General equilibrium moels are usually represented as a system of levels equations (e.g., in North America) or a system of linearized equations (e.g., in Australia). Either representation can be used to obtain accurate solutions. General-purpose software is available in both cases-GAMS or MPS/GE is typically used by levels modellers and GEMPACK by linearizers. Some equations (notably accounting identities) are naturally expressed in the levels while others (especially behavioural equations) are naturally expressed in a linearized form. This paper describes the new GEMPACK facility for solving models represented as a mixture of levels and linearized equations and discusses the advantages to modellers of using such a representation. 相似文献
73.
CW van Haselen PV Diederen J Toonstra SC van der Putte LH Rademakers JA Faber WA van Vloten 《Canadian Metallurgical Quarterly》1998,290(11):583-590
Small-cell variants of Sézary syndrome and mycosis fungoides (MF) have been described. However, in these studies the nuclear area of the small-cell variant of MF (SC-MF) as compared to histological classical MF (CL-MF) was not characterized objectively by quantitative electron microscopy. In a 14-year follow-up period, of a total of 76 patch/plaque stage MF patients seen in the Department of Dermatology of the University Hospital Utrecht, 14 (18%) had an infiltrate composed of atypical lymphocytes characterized by a distinctly smaller cell diameter and smaller, hyperchromatic, deeply indented nuclei as compared to the usual cell type of MF. The aim of the investigation was to confirm this observation objectively using quantitative electron microscopy (morphometry) and to define SC-MF as compared to CL-MF. The study was performed on the 14 patients with SC-MF, and 10 patients with clinical and histological CL-MF and 4 patients with chronic eczema. Electron micrographs of sections obtained from each biopsy were analysed by computer to produce the following data: a nuclear contour index (NCI), the mean nuclear area (MNA), the mean nuclear area of the cells above the 75th percentile (P75NA) and the percentage of cells larger than 30 microm2. The values of MNA differed significantly between patients with SC-MF and those with CL-MF (17.6 vs 23.2 microm2; P = 0.02), as did the values of P75NA (20.7 vs 27.9 microm2; P = 0.01). The NCI of the SC-MF and CL-MF patients were similar. These results are consistent with our observations that SC-MF does indeed exist. 相似文献
74.
Tomás Sánchez López Damith C. Ranasinghe Mark Harrison Duncan McFarlane 《Personal and Ubiquitous Computing》2012,16(3):291-308
The Internet of Things (IoT) concept is being widely presented as the next revolution toward massively distributed information,
where any real-world object can automatically participate in the Internet and thus be globally discovered and queried. Despite
the consensus on the great potential of the concept and the significant progress in a number of enabling technologies, there
is a general lack of an integrated vision on how to realize it. This paper examines the technologies that will be fundamental
for realizing the IoT and proposes an architecture that integrates them into a single platform. The architecture introduces
the use of the Smart Object framework to encapsulate radio-frequency identification (RFID), sensor technologies, embedded
object logic, object ad-hoc networking, and Internet-based information infrastructure. We evaluate the architecture against
a number of energy-based performance measures, and also show that it outperforms existing industry standards in metrics such
as network throughput, delivery ratio, or routing distance. Finally, we demonstrate the feasibility and flexibility of the
architecture by detailing an implementation using Wireless Sensor Networks and Web Services, and describe a prototype for
the real-time monitoring of goods flowing through a supply chain. 相似文献
75.
Williams Ludwell Harrison III 《LISP and Symbolic Computation》1989,2(3-4):179-396
Lisp and its descendants are among the most important and widely used of programming languages. At the same time, parallelism in the architecture of computer systems is becoming commonplace. There is a pressing need to extend the technology of automatic parallelization that has become available to Fortran programmers of parallel machines, to the realm of Lisp programs and symbolic computing. In this paper we present a comprehensive approach to the compilation of Scheme programs for shared-memory multiprocessors. Our strategy has two principal components:interprocedural analysis andprogram restructuring. We introduceprocedure strings andstack configurations as a framework in which to reason about interprocedural side-effects and object lifetimes, and develop a system of interprocedural analysis, using abstract interpretation, that is used in the dependence analysis and memory management of Scheme programs. We introduce the transformations ofexit-loop translation andrecursion splitting to treat the control structures of iteration and recursion that arise commonly in Scheme programs. We propose an alternative representation for s-expressions that facilitates the parallel creation and access of lists. We have implemented these ideas in a parallelizing Scheme compiler and run-time system, and we complement the theory of our work with snapshots of programs during the restructuring process, and some preliminary performance results of the execution of object codes produced by the compiler.This work was supported in part by the National Science Foundation under Grant No. NSF MIP-8410110, the U.S. Department of Energy under Grant No. DE-FG02-85ER25001, the Office of Naval Research under Grant No. ONR N00014-88-K-0686, the U.S. Air Force Office of Scientific Research under Grant No. AFOSR-F49620-86-C-0136, and by a donation from the IBM Corportation. 相似文献
76.
77.
78.
Nicholas P. Petropolis Harrison M. Petropolis Nicole E. MacNeil Taylor M. Doucet D. Gerrard Marangoni 《Journal of surfactants and detergents》2021,24(1):51-66
The critical micelle concentrations (CMC) values and counterion dissociation (α values) have been determined for a number of mixed micellar systems consisting of two typical ionic surfactants and glycol ethers (glymes) as cosurfactants, namely diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. Conductance experiments were used to determine the CMC and α values of the mixed micelles as a function of glyme concentration in the aqueous mixed solvent. Favorable interactions between sodium dodecyl sulfate micelles and glyme cosurfactants were deduced from the decreases in the CMC values and the large increase in the α values of these systems as a function of increasing glyme concentration in the mixed solvents. In contrast to the anionic surfactant/glyme systems, in general, there appeared to be little favorable interactions between the surfactant and glymes when micelles of the cationic surfactant dodecyltrimethylammonium bromide were formed in water/glyme solvent systems containing an increasing amount of the glymes. The interaction of glymes with the surfactant micelles was examined closely via 13C nuclear magnetic resonance (NMR) chemical shifts for both surfactant and glyme carbons; these chemical shifts changes were interpreted in terms of the distribution and the localization of the glymes in the aggregates. Finally, partition constants, determined from two-dimensional diffusion-oriented spectroscopy (2D-DOSY) experiments, were used to calculate thermodynamic quantities of transfer of the glymes between the bulk phase and the self-assembled aggregates. All these results are interpreted in terms of the key contributions that both the glyme ethoxylated groups and alkyl endgroups make to the hydrophobic interactions. 相似文献
79.
Railway Engineering Science - Electrified railways are becoming a popular transport medium and these consume a large amount of electrical energy. Environmental concerns demand reduction in energy... 相似文献
80.
Dale A. Creaser Philip G. Harrison M. A. Morris B. A. Wolfindale 《Catalysis Letters》1994,23(1-2):13-24
X-ray photoelectron spectroscopy has been used to examine the nature of the oxide overlayers on a passivated cerium metal foil as a function of a variety of oxidation and reduction treatments. Oxidation of a clean uncontaminated cerium(III) oxide surface is facile at room temperature and produces non-stoichiometric ceria (CeO2–x) at oxygen doses as low as 10 L. At higher doses the overlayer thickens, and after a dose of 160 L the layer depth exceeds the Ce 3d photoelectron attenuation distance of about 20 Å. High pressure treatment of the foil in oxygen (0.5 bar at RT and 473 K) produces CeO2 in a high degree of crystallographic order such that O 1s photoelectron intensities are increased above that expected from a randomly oriented powder. An attempt to reduce the CeO2 layer formed by controlled oxidation with CO (633 K, 14 h, 0.6 bar) results in the formation of a carbonated surface layer. Results following attempts to reoxidise this layer are discussed. 相似文献