全文获取类型
收费全文 | 14915篇 |
免费 | 1487篇 |
国内免费 | 326篇 |
专业分类
电工技术 | 470篇 |
综合类 | 395篇 |
化学工业 | 3140篇 |
金属工艺 | 575篇 |
机械仪表 | 770篇 |
建筑科学 | 684篇 |
矿业工程 | 164篇 |
能源动力 | 593篇 |
轻工业 | 1112篇 |
水利工程 | 146篇 |
石油天然气 | 247篇 |
武器工业 | 74篇 |
无线电 | 2448篇 |
一般工业技术 | 2646篇 |
冶金工业 | 1162篇 |
原子能技术 | 204篇 |
自动化技术 | 1898篇 |
出版年
2024年 | 58篇 |
2023年 | 215篇 |
2022年 | 390篇 |
2021年 | 594篇 |
2020年 | 430篇 |
2019年 | 412篇 |
2018年 | 546篇 |
2017年 | 463篇 |
2016年 | 592篇 |
2015年 | 577篇 |
2014年 | 770篇 |
2013年 | 1021篇 |
2012年 | 943篇 |
2011年 | 1069篇 |
2010年 | 885篇 |
2009年 | 839篇 |
2008年 | 763篇 |
2007年 | 644篇 |
2006年 | 612篇 |
2005年 | 504篇 |
2004年 | 466篇 |
2003年 | 398篇 |
2002年 | 375篇 |
2001年 | 328篇 |
2000年 | 300篇 |
1999年 | 321篇 |
1998年 | 410篇 |
1997年 | 321篇 |
1996年 | 240篇 |
1995年 | 190篇 |
1994年 | 169篇 |
1993年 | 115篇 |
1992年 | 91篇 |
1991年 | 78篇 |
1990年 | 80篇 |
1989年 | 71篇 |
1988年 | 51篇 |
1987年 | 52篇 |
1986年 | 56篇 |
1985年 | 37篇 |
1984年 | 31篇 |
1983年 | 29篇 |
1982年 | 15篇 |
1981年 | 26篇 |
1980年 | 25篇 |
1979年 | 15篇 |
1978年 | 15篇 |
1977年 | 18篇 |
1976年 | 30篇 |
1975年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
931.
Tae-Hyun?WonEmail author Gi-Hyun?Hwang June?Ho?Park Man?Hyung?Lee 《Journal of Mechanical Science and Technology》2003,17(2):187-196
In this paper, a new methodology of evolutionary computations - An Adaptive Evolutionary Algorithm (AEA) is proposed. AEA
uses a genetic algorithm (GA) and an evolution strategy (ES) in an adaptive manner in order to take merits of two different
evolutionary computations : global search capability of GA and local search capability of ES. In the reproduction procedure,
the proportions of the population by GA and ES are udaptively modulated according to the fitness. AEA is used for designing
fuzzy logic controller (FLC) for a high-angle-of-attack flight system for a super-maneuverable version of F-18 aircraft. AEA
is used to determine the membership functions and scaling factors of an FLC. The computer simulation results show that the
FLC has met both robustness and performance requirements. 相似文献
932.
Sung?Soo?Park Sang?Joon?Choe Dong?Ho?ParkEmail author 《Korean Journal of Chemical Engineering》2003,20(2):256-261
The incorporation of nickel into mesoporous molecular sieves MCM-41 was carried out. Ni-PO/MCM41 and Ni-C1/MCM41 were prepared
by using Ni(II) acetate solution adjusted to pH=2.5 with phosphoric acid and hydrochloric acid, respectively, by the incipient
wetness method. Photoacoustic spectroscopy (PAS) was used to study the local environments of Ni(II) incorporated into mesopores.
The PAS of as-prepared Ni/MCM41, Ni-Cl/MCM41, and Ni-PO/MCM41 with Ni(II) acetate solution exhibits two bands of λmax around 400 nm and 750 nm, which could be assigned to the3A2g→3Tlg(F) and the3A2g→3Tlg(P) transition of octahedral Ni(II) species. After calcination, Ni ion within Ni-PO/MCM41 dispersed atomically onto the surface
of MCM-41 channel as an octahedral species without the transformation to nickel oxide phase, while Ni ion within Ni-Cl/MCM41
and Ni/MCM41 transformed to nickel oxide phase. It may be attributed to the fact that each Ni ion is separated by the phosphate
grafted to surface silanol group. The effects of phosphoric acid on the dispersity of Ni ion within MCM-41 have been investigated
using31P and29Si MAS NMR spectroscopy and X-ray photoelectron spectroscopy. 相似文献
933.
Md. Raisul Islam N. E. Wijeysundera J. C. Ho 《International Journal of Refrigeration》2003,26(8):909-917
This paper describes the development of a novel film-inverting design concept for falling-film absorbers. The solid surface of the absorber is segmented so that both surfaces of the falling-film are alternatively cooled in a periodic manner. A conventional tubular absorber is modified by introducing film-guiding fins between tubes to produce a film-inverting arrangement. A maximum increase in vapour absorption rate of about 100% is obtained with the film-inverting design compared to the tubular absorber. The numerical simulation indicates that the vapour absorption rate can be increased by using a large number of film-inverting segments in the absorber. 相似文献
934.
A dispatching method is suggested for automated guided vehicles by using an auction algorithm. The dispatching method in
this study is different from traditional dispatching rules in that it looks into the future for an efficient assignment of
delivery tasks to vehicles and also in that multiple tasks are matched with multiple vehicles. The dispatching method in this
study is distributed in the sense that the dispatching decisions are made through communication among related vehicles and
machines. The theoretical rationale behind the distributed dispatching method is also discussed. Through a simulation study,
the performance of the method is compared with that of a popular dispatching rule.
RID="*"
ID="*" The research was financially supported by the Sasakawa Scientific Research Grant from The Japan Science Society. The
original version of the simulation program is provided by Professor Jae Yeon Kim at Dong Yang University, Korea.
Correspondence to: J. K. Lim 相似文献
935.
Vascular disease produces changes in lumenal shape evident in magnetic resonance angiography (MRA). However, quantification of vascular shape from MRA is problematic due to image artifacts. Prior deformable models for vascular surface reconstruction primarily resolve problems of initialization of the surface mesh. However, initialization can be obtained in a trivial manner for MRA using isosurfaces. We propose a methodology for deforming the isosurface to conform to the boundaries of objects in the image with minimal a priori assumptions of object shape. As in conventional methods, external forces attract the surface toward edges in the image. However, smoothing is produced by a moment that aligns the normals of adjacent surface triangles. Notably, the moment produces no translational motion of surface triangles. The deformable isosurface was applied to a digital phantom of a stenotic artery, to MRA of three renal arteries with atherosclerotic disease and MRA of one carotid artery with atherosclerotic disease. Results of the surface reconstruction from the deformable model were compared with conventional X-ray angiography for the renal arteries. Measurement of the degree of stenosis of the renal arteries was within 12% +/- 6%. The deformable model provided improvements over the isosurface in all cases in terms of measurement of the degree of stenosis or improving the surface smoothness. 相似文献
936.
A starlike water-soluble fullerene derivative, hexa(sulfonbutyl)fullerene (C60[(CH2)4SO3-]6; HSBF), consisting of a C60 cage covalently bonded with six negatively charged sulfonate arms, was synthesized and used to selectively precipitate positively charged surfactants, amino acids, peptides, and proteins. The affinity of HSBF to the analytes depends on the charge, structure, and hydrophobic characteristics of the analytes. The ion pair precipitate was easily removed from the solution by centrifugation. After washing, the precipitate was redissolved in the solvent or buffer solution and the analyte was characterized by laser desorption ionization-time-of-flight mass spectrometry (LD-TOF). HSBF shows strong optical absorbance in the UV range, so no additional organic matrix was required to conduct LD-TOF analysis of small analytes. For the solution that contained five quaternary amines differing only in alkyl chain length, HSBF exhibits the highest affinity to the amine with the longest alkyl chain. Only the arginine signal was detected from the solution that contained 14 amino acids. The peptides with arginine as the end groups interacted most strongly with HSBF and could be selectively precipitated from a solution of a mixture of five peptides. The signals associated with a trace amount of charged peptides derived from the digestion of proteins by trypsin were greatly enhanced after concentration with HSBF. Among eight proteins in the sample solution, insulin had the strongest affinity to the HSBF and exhibited the strongest signal on the matrix-assisted laser desorption/ionization mass spectrum. 相似文献
937.
Physicochemical characterization of diclofenac sodium-loaded poloxamer gel as a rectal delivery system with fast absorption 总被引:1,自引:0,他引:1
Yong CS Sah H Jahng Y Chang HW Son JK Lee SH Jeong TC Rhee JD Baek SH Kim CK Choi HG 《Drug development and industrial pharmacy》2003,29(5):545-553
Rectal poloxamer gel systems composed of poloxamers and bioadhesive polymers were easy to administer to the anus and were mucoadhesive to the rectal tissues without leakage after the dose. However, a poloxamer gel containing diclofenac sodium could not be developed using bioadhesive polymers, since the drug was precipitated in this preparation. To develop a poloxamer gel using sodium chloride instead of bioadhesive polymers, the physicochemical properties such as gelation temperature, gel strength, and bioadhesive force of various formulations composed of diclofenac sodium, poloxamers, and sodium chloride were investigated. Furthermore, the pharmacokinetic study of diclofenac sodium delivered by the poloxamer gel was performed. Diclofenac sodium significantly increased the gelation temperature and weakened the gel strength and bioadhesive force, while sodium chloride did the opposite. The poloxamer gels with less than 1.0% sodium chloride, in which the drug was not precipitated, were inserted into the rectum without difficulty and leakage, and were retained in the rectum of rats for at least 6 hr. Furthermore, poloxamer gel gave significantly higher initial plasma concentrations and faster Tmax of diclofenac sodium than did solid suppository, indicating that drug from poloxamer gel could be absorbed faster than that from the solid one in rats. Our results suggested that a rectal poloxamer gel system with sodium chloride and poloxamers was a more physically stable, convenient, and effective rectal dosage form for diclofenac sodium. 相似文献
938.
Teng S Liu L Zu J Luan Z Liu D 《Journal of the Optical Society of America. A, Optics, image science, and vision》2003,20(9):1747-1754
A uniform formulation for the self-imaging of gratings with any kind of partially coherent illumination is developed in terms of the cross mutual spectral density of the partial coherence theory. The formulation includes the time diffractive intensity distribution and the averaged diffractive intensity distribution at self-imaging distances and can be applied to both continuous and temporal illuminations with any kind of spectra. It is found that the averaged intensity distribution is related only to the intensity spectrum of illumination. The continuous polychromatic illumination and the ultrashort laser pulses with or without frequency chirp are then studied by a numerical stimulation. It is shown that the ultrashort laser pulse and the continuous polychromatic illuminations have similar averaged self-image distributions. Thus the Talbot effect may help in the study of the temporal and spectral characteristics of ultrashort laser pulses. An experiment with an LED is given, as well. 相似文献
939.
Völcker N Klee D Höcker H Langefeld S 《Journal of materials science. Materials in medicine》2001,12(2):111-119
Surface modification techniques were employed in order to provide functionalized silicone rubber with enhanced cytocompatibility. Acrylic acid (AAc), methacrylic acid (MAAc) and glycidylmethacrylate (GMA) were graft-co-polymerized onto the surface of silicone induced by an argon plasma and thermal initiation. The polymerizations were carried out in solution, in the case of acrylic acid a vapor phase graft-co-polymerization subsequent to argon plasma activation was carried out as well. Human fibronectin (hFn), which acts as a cell adhesion mediator for fibroblasts, was immobilized by making use of the generated carboxylic or epoxy groups, respectively. Surface analysis was accomplished by means of X-ray photoelectron spectroscopy (XPS), infrared spectroscopy in attenuated total reflection mode (IR-ATR), scanning electron microscopy (SEM), atomic force microscopy (AFM) and dynamic contact angle measurements using the Wilhelmy-plate method. The amount of immobilized active hFn was semiquantified by enzyme-linked immunosorbent assay (ELISA) using a structure-specific antibody against the cell-binding domain of hFn. In vitro testing showed a remarkable difference between surfaces exposing adsorbed-only and surfaces with covalently immobilized hFn. © 2001 Kluwer Academic Publishers 相似文献
940.
In this paper, we study the system capacity and access control for the TDMA/SS (time division multiple access with spread spectrum) cellular networks supporting multimedia services. In the TDMA/SS system, time is divided into frames and each frame is further divided into slots. Only one user is allowed to transmit in a slot and spread spectrum technique is adopted to combat inter-cell interference. A packet can occupy more than one slot, depending on the user's data rate and quality of service requirement. We derive a necessary and sufficient condition for a group of users to be admissible for the TDMA/SS system and prove that its admission region contains that of the TDMA/CDMA system. In the TDMA/CDMA system, time is also divided into frames and each frame consists of several slots. The difference is that every packet occupies exactly one slot and multiple users can transmit their packets in the same slot. Numerical results show that the admission region of the TDMA/SS system can be significantly larger than that of the TDMA/CDMA system. To further increase bandwidth utilization and guarnatee delay bound requirements, several access control schemes are proposed. Simulation results are obtained for these access control schemes. 相似文献