全文获取类型
收费全文 | 6688篇 |
免费 | 453篇 |
国内免费 | 9篇 |
专业分类
电工技术 | 78篇 |
综合类 | 2篇 |
化学工业 | 1931篇 |
金属工艺 | 112篇 |
机械仪表 | 211篇 |
建筑科学 | 288篇 |
矿业工程 | 24篇 |
能源动力 | 261篇 |
轻工业 | 975篇 |
水利工程 | 60篇 |
石油天然气 | 35篇 |
无线电 | 417篇 |
一般工业技术 | 1041篇 |
冶金工业 | 316篇 |
原子能技术 | 47篇 |
自动化技术 | 1352篇 |
出版年
2024年 | 22篇 |
2023年 | 96篇 |
2022年 | 272篇 |
2021年 | 310篇 |
2020年 | 208篇 |
2019年 | 231篇 |
2018年 | 277篇 |
2017年 | 291篇 |
2016年 | 280篇 |
2015年 | 235篇 |
2014年 | 313篇 |
2013年 | 568篇 |
2012年 | 447篇 |
2011年 | 552篇 |
2010年 | 373篇 |
2009年 | 403篇 |
2008年 | 341篇 |
2007年 | 314篇 |
2006年 | 264篇 |
2005年 | 196篇 |
2004年 | 145篇 |
2003年 | 164篇 |
2002年 | 134篇 |
2001年 | 78篇 |
2000年 | 83篇 |
1999年 | 65篇 |
1998年 | 54篇 |
1997年 | 55篇 |
1996年 | 52篇 |
1995年 | 40篇 |
1994年 | 30篇 |
1993年 | 27篇 |
1992年 | 15篇 |
1991年 | 21篇 |
1990年 | 12篇 |
1989年 | 19篇 |
1988年 | 11篇 |
1987年 | 11篇 |
1986年 | 11篇 |
1985年 | 14篇 |
1984年 | 9篇 |
1983年 | 9篇 |
1982年 | 14篇 |
1981年 | 6篇 |
1980年 | 9篇 |
1979年 | 10篇 |
1978年 | 19篇 |
1976年 | 9篇 |
1975年 | 5篇 |
1973年 | 5篇 |
排序方式: 共有7150条查询结果,搜索用时 15 毫秒
41.
Raul C. Maranhão Thais B. Cesar Suzana R. Pedroso-Mariani Mario H. Hirata Carlos H. Mesquita 《Lipids》1993,28(8):691-696
A protein-free microemulsion (LDE) with a lipid composition resembling that of low-density lipoprotein (LDL) was used in metabolic
studies in rats to compare LDE with the native lipoprotein. LDE labeled with radioactive lipids was injected into the bloodstream
of male Wistar rats, and plasma kinetics of the labeled lipids were followed on plasma samples collected at regular intervals
for 12 h after injection. The 24-h LDE uptake by different tissues was also measured in tissue samples excised after the animals
had been sacrificed. We found that LDE plasma kinetics were similar to those described for native LDL [fractional clearance
rate (FCR) of cholesteryl ester, 0.42±0.11 h−1]. The major site for LDE uptake was the liver, and the tissue distribution of the LDE injected radioactivity was as one would
expect for LDL. To test whether LDE was taken up by the specific LDL receptors, the LDE emulsion was injected into rats treated
with 17α-ethinylestradiol, which is known to increase the activity of these receptors; as expected, removal of LDE from the
bloodstream increased (FCR=0.90±0.35 h−1). On the other hand, saturation of the receptors that remove remnants by prior infusion of massive amounts of lymph chylomicrons
did not change LDE plasma kinetics. These results indicate that LDE is cleared from plasma by B,E receptors and not by the
E receptors that remove remnants. Incorporation of free cholesterol into LDE increased LDE plasma clearance. Incubation studies
also showed that LDE incorporates a variety of apolipoproteins, including apo E, a ligand for recognition of lipoproteins
by specific receptors. Our data suggest that LDE can be a useful tool to test LDL metabolism and B,E receptor function. 相似文献
42.
Mari Lou Balmer Fred F. Lange Carlos G. Levi 《Journal of the American Ceramic Society》1994,77(8):2069-2075
Aqueous solutions of zirconium acetate and aluminum nitrate were spray pyrolyzed at 250°C and upquenched to different temperatures to yield metastable solid solutions of composition Zr(1− x ) Alx O(2− x /2) . An amorphous oxide forms first during pyrolysis which subsequently crystallizes as a single phase for x ≤ 0.57 (≤40 mol% Al2 O3 ). The crystallization temperature increased with Al2 O3 content. Electron diffraction, supported by Raman spectroscopy, indicates that the initial phase is tetragonal. At higher temperatures, the initial solid solation partitions to other metastable phases, viz., t -ZrO2 +γ-Al2 O3 , prior to achieving their equilibrium phase assemblage, m -ZrO2 +α-Al2 O3 . Partitioning yields a nanocomposite microstructure with grain sizes of 20–100 nm, compared to the 3 to 5 nm in the initial, single phase. Compositions containing 45 to 50 mol% Al2 O3 concurrently crystallize and partition. The structure selected during crystallization and the partitioning phenomena are discussed in terms of diffusional constraints during crystallization, which are conceptually similar to those operating during rapid solidification. 相似文献
43.
High molecular weight poly(α-methyl β,l-malate) (Mn ∼ 25,000, PD ∼ 1.7) was prepared from microbial poly(β,l-malic acid) (Mn ∼ 29,000, PD ∼ 1.3) by methylation with diazomethane in dry acetone without substantial cleavage of the polyester main chain. The thermal properties of this poly(malate) were assessed and its crystal structure was preliminary examined. Two crystal forms were identified by X-ray diffraction, their occurrence being dependent on crystallization conditions. The kinetics of nonisothermal and isothermal crystallizations from the melt were studied and modelled using the Avrami approach. Results were compared to those recently reported by us for low molecular weight poly(α-methyl β,l-malate) (Mn ∼ 3000, PD ∼ 1.3). 相似文献
44.
Electronic Markets - Robots are being implemented in many frontline services, from waiter robots in restaurants to robotic concierges in hotels. A growing number of firms in hospitality and tourism... 相似文献
45.
Leonardo Roberto da Silva Eduardo Carlos Bianchi Ronaldo Yoshinobu Fusse Rodrigo Eduardo Catai Thiago Valle Frana Paulo Roberto Aguiar 《International Journal of Machine Tools and Manufacture》2007,47(2):412-418
The quality of machined components is currently of high interest, for the market demands mechanical components of increasingly high performance, not only from the standpoint of functionality but also from that of safety. Components produced through operations involving the removal of material display surface irregularities resulting not only from the action of the tool itself, but also from other factors that contribute to their superficial texture. This texture can exert a decisive influence on the application and performance of the machined component. This article analyzes the behavior of the minimum quantity lubricant (MQL) technique and compares it with the conventional cooling method. To this end, an optimized fluid application method was devised using a specially designed nozzle, by the authors, through which a minimum amount of oil is sprayed in a compressed air flow, thus meeting environmental requirements. This paper, therefore, explores and discusses the concept of the MQL in the grinding process. The performance of the MQL technique in the grinding process was evaluated based on an analysis of the surface integrity (roughness, residual stress, microstructure and microhardness). The results presented here are expected to lead to technological and ecological gains in the grinding process using MQL. 相似文献
46.
In ‘multi-adjoint logic programming’, MALP in brief, each fuzzy logic program is associated with its own ‘multi-adjoint lattice’ for modelling truth degrees beyond the simpler case of true and false, where a large set of fuzzy connectives can be defined. On this wide repertoire, it is crucial to connect each implication symbol with a proper conjunction thus conforming constructs of the form (←i, &i) called ‘adjoint pairs’, whose use directly affects both declarative and operational semantics of the MALP framework. In this work, we firstly show how the strong dependence of adjoint pairs can be largely weakened for an interesting ‘sub-class’ of MALP programs. Then, we reason in a similar way till conceiving a ‘super-class’ of fuzzy logic programs beyond MALP, which definitively drops out the need for using adjoint pairs, since the new semantics behaviour relies on much more relaxed lattices than multi-adjoint ones. 相似文献
47.
Decision recommendations are a set of alternative options for clinical decisions (e.g., diagnosis, prognosis, treatment selection, follow-up, and prevention) that are provided to decision makers by knowledge-based Clinical Decision Support Systems (k-CDSS) as aids. We propose to follow a “reasoning over domain” approach for the generation of decision recommendations by gathering and inferring conclusions from production rules. In order to rationalize our approach, we present a specification that will sustain the logic models supported in the knowledge bases we use for persistence. We introduce first the underlying knowledge model and then the necessary extensions that will convey toward the solution of the reported needs. The starting point of our approach is the proposition of Reflexive Ontologies (RO). Here, we go a step further, proposing an extension of RO that includes the handling and reasoning that production rules provide. Our approach speeds up the recommendation generation process. 相似文献
48.
49.
Gustavo Zavala Antonio J. Nebro Francisco Luna Carlos A. Coello Coello 《Structural and Multidisciplinary Optimization》2016,53(3):545-566
Many structural design problems in the field of civil engineering are naturally multi-criteria, i.e., they have several conflicting objectives that have to be optimized simultaneously. An example is when we aim to reduce the weight of a structure while enhancing its robustness. There is no a single solution to these types of problems, but rather a set of designs representing trade-offs among the conflicting objectives. This paper focuses on the application of multi-objective metaheuristics to solve two variants of a real-world structural design problem. The goal is to compare a representative set of state-of-the-art multi-objective metaheuristic algorithms aiming to provide civil engineers with hints as to what optimization techniques to use when facing similar problems as those selected in the study presented in this paper. Accordingly, our study reveals that MOCell, a cellular genetic algorithm, provides the best overall performance, while NSGA-II, the de facto standard multi-objective metaheuristic technique, also demonstrates a competitive behavior. 相似文献
50.
This paper proposes a novel pose (position and orientation) consensus controller for networks of heterogeneous robots modeled in the operational space. The proposed controller is a distributed proportional plus damping scheme that, with a slight modification, solves both the leader–follower and leaderless consensus problems. A singularity‐free representation, unit quaternion, is used to describe the robots orientation, and the network is represented by an undirected and connected interconnection graph. Furthermore, it is shown that the controller is robust to interconnection variable time delays. Experiments with a network of two 6‐degrees‐of‐freedom robots are presented to illustrate the performance of the proposed scheme. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献