全文获取类型
收费全文 | 82760篇 |
免费 | 9074篇 |
国内免费 | 6301篇 |
专业分类
电工技术 | 8502篇 |
技术理论 | 1篇 |
综合类 | 8103篇 |
化学工业 | 12923篇 |
金属工艺 | 4569篇 |
机械仪表 | 3341篇 |
建筑科学 | 7700篇 |
矿业工程 | 4013篇 |
能源动力 | 3278篇 |
轻工业 | 8104篇 |
水利工程 | 3544篇 |
石油天然气 | 4206篇 |
武器工业 | 953篇 |
无线电 | 6001篇 |
一般工业技术 | 7935篇 |
冶金工业 | 3866篇 |
原子能技术 | 1292篇 |
自动化技术 | 9804篇 |
出版年
2024年 | 361篇 |
2023年 | 1341篇 |
2022年 | 2235篇 |
2021年 | 2782篇 |
2020年 | 3024篇 |
2019年 | 2788篇 |
2018年 | 2632篇 |
2017年 | 3108篇 |
2016年 | 3365篇 |
2015年 | 3457篇 |
2014年 | 5030篇 |
2013年 | 5521篇 |
2012年 | 6072篇 |
2011年 | 6365篇 |
2010年 | 4693篇 |
2009年 | 4954篇 |
2008年 | 4450篇 |
2007年 | 5389篇 |
2006年 | 4643篇 |
2005年 | 4017篇 |
2004年 | 3438篇 |
2003年 | 2866篇 |
2002年 | 2408篇 |
2001年 | 2068篇 |
2000年 | 1829篇 |
1999年 | 1612篇 |
1998年 | 1325篇 |
1997年 | 1135篇 |
1996年 | 1018篇 |
1995年 | 836篇 |
1994年 | 686篇 |
1993年 | 552篇 |
1992年 | 527篇 |
1991年 | 364篇 |
1990年 | 267篇 |
1989年 | 214篇 |
1988年 | 146篇 |
1987年 | 104篇 |
1986年 | 84篇 |
1985年 | 63篇 |
1984年 | 77篇 |
1983年 | 53篇 |
1982年 | 53篇 |
1981年 | 27篇 |
1980年 | 34篇 |
1979年 | 22篇 |
1978年 | 17篇 |
1977年 | 10篇 |
1975年 | 12篇 |
1951年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Mengru Liu Weihai Zhang Limin Ma 《International Journal of Adaptive Control and Signal Processing》2022,36(1):69-87
The article investigates the finite-time adaptive fuzzy control for a class of nonlinear systems with output constraint and input dead-zone. First, by skillfully combining the barrier Lyapunov function, backstepping design method, and finite-time control theory, a novel adaptive state-feedback tracking controller is constructed, and the output constraint of the nonlinear system is not violated. Second, the fuzzy logic system is used to approximate unknown function in the nonlinear system. Third, the finite-time command filter is introduced to avoid the problem of “complexity explosion” caused by repeated differentiations of the virtual control signal in conventional backstepping control schemes. Meanwhile, a new saturation function is added in the compensating signal for filter error to improve control accuracy. Finally, based on Lyapunov stability analysis, all the signals of the closed-loop are proved to be semi-globally uniformly ultimately bounded, and the tracking error converges to a small neighborhood region of the origin in a finite time. A simulation example is presented to demonstrate the effectiveness for the proposed control scheme. 相似文献
2.
Yuhang Xing Ruyi Li Lu Xue Mianhong Chen Xuli Lu Zhihao Duan Wei Zhou Jihua Li 《International Journal of Food Science & Technology》2022,57(8):5268-5279
Mangiferin (MGF) is a phenolic compound isolated from mango, but its poor solubility significantly limits its use. In this study, MGF was embedded into the inner aqueous phase of W1/O/W2 emulsions. Firstly, the dissolution method of MGF was determined. MGF remained stable in solution with pH 13 at 30 min, and its solubility reached 10 mg mL−1. When the pH of MGF solutions was adjusted from pH 13 to pH 6, MGF did not immediately crystallise, providing sufficient time to construct the MGF-loaded W1/O/W2 emulsions. Subsequently, the MGF-loaded W1/O/W2 emulsions were constructed using polyglycerol polyricinoleate (PGPR) and calcium caseinate (CAS). The formation and stability of the W1/O/W2 emulsions were investigated. The MGF-loaded W1/O/W2 emulsions stabilised with 1% PGPR and 1% – 3% CAS exhibited a low viscosity, limited loading capacity, and poor stability. Conversely, the MGF-loaded W1/O/W2 emulsions stabilised by 3%PGPR–3%CAS exhibited optimal loading capacity (encapsulation efficiency = 95.31% and loading efficiency = 0.91%) and stability, which was attributed to the fact that high viscosity and gel state retarded the migration of inner aqueous phase. These results indicated that the W1/O/W2 emulsions stabilised by PGPR and CAS may be a potential alternative for encapsulating mangiferin. 相似文献
3.
Tomohiro Toigawa Yasuhiro Tsubata Takeshi Kai Takuya Furuta Yuta Kumagai Tatsuro Matsumura 《溶剂提取与离子交换》2021,39(1):74-89
ABSTRACT Absorbed-dose estimation is essential for evaluation of the radiation tolerance of minor-actinide-separation processes. We propose a dose-evaluation method based on radiation permeability, with comparisons of heterogeneous structures seen in the solvent-extraction process, such as emulsions forming in the mixture of the organic and aqueous phases. A demonstration of radiation-energy-transfer simulation is performed with a focus on the minor-actinide-recovery process from high-level liquid waste with the aid of the Monte Carlo radiation-transport code PHITS. The simulation results indicate that the dose absorbed by the extraction solvent from alpha radiation depends upon the emulsion structure, and that from beta and gamma radiation depends upon the mixer-settler-apparatus size. Non-negligible contributions of well-permeable gamma rays were indicated in terms of the plant operation of the minor-actinide-separation process. 相似文献
4.
5.
《International Journal of Hydrogen Energy》2021,46(73):36301-36313
By choosing a triple block polymer, poly(styrene-b-(ethylene-co-butylene)-b-styrene) (SEBS), as the backbone and adopting a long side-chain double-cation crosslinking strategy, a series of SEBS-based anion-exchange membranes (AEMs) was successively synthesized by chloromethylation, quaternization, crosslinking, solution casting, and alkalization. The 70C16-SEBS-TMHDA membrane showed high OH− conductivity (72.13 mS/cm at 80 °C) and excellent alkali stability (only 10.86% degradation in OH− conductivity after soaking in 4-M NaOH for 1700 h at 80 °C). Furthermore, the SR was only 9.3% at 80 °C and the peak power density of the H2/O2 single cell was up to 189 mW/cm2 at a current density of 350 mA/cm2 at 80 °C. By introducing long flexible side chains into a polymer SEBS backbone, the structure of the hydrophilic–hydrophobic microphase separation in the membrane was constructed to improve the ionic conductivity. Additionally, network crosslinked structure improved dimensional stability and mechanical properties. 相似文献
6.
7.
Developing the thermal stability of metal-based ceramic composites or their films has always been challenging and bottlenecks for the utilization of energy. In this paper, the novel mesh-like functional Al doped-MoO3 nanocomposite film with even distribution and high purity was firstly fabricated by the high-efficiency electrophoretic deposition and surface modification. The optimal suspension turned out to be the mixture of isopropanol and the additives of polyethyleneimine and benzoic acid. The microtopography, crystalline structure, environmental resistance and thermal stability were analyzed by field emission scanning electron microscope (FESEM), energy dispersive X-ray (EDX), X-ray diffractometer (XRD), exposure and droplet-impacting test, DSC analysis and ignition test, respectively. The water contact angle and sliding angle of product can reach ~170° and <1°, indicating the excellent anti-wetting property. In addition, the high heat-release (~3180 J/g) of product all kept almost unchangeable after six months exposure experiments, demonstrating the outstanding thermostability. The exquisite design idea here can perfectly match microelectromechanical system (MEMS), providing the valuable reference for fabricating other metal-based high-energy composites with long lifespan for real industrial applications. 相似文献
8.
《International Journal of Hydrogen Energy》2022,47(54):22981-22992
In this study, a three-dimensional model was established using the lattice Boltzmann method (LBM) to study the internal ice melting process of the gas diffusion layer (GDL) of the proton exchange membrane fuel cell (PEMFC). The single-point second-order curved boundary condition was adopted. The effects of GDL carbon fiber number, growth slope of the number of carbon fibers and carbon fiber diameter on ice melting were studied. The results were revealed that the temperature in the middle and lower part of the gradient distribution GDL is significantly higher than that of the no-gradient GDL. With the increase of the growth slope of the number of carbon fiber, the temperature and melting rate gradually increase, and the position of the solid-liquid interface gradually decreases. The decrease in the number of carbon fibers has a similar effect as the increase in the growth slope of the number of carbon fibers. In addition, as the diameter of the carbon fiber increases, the position of the solid-liquid interface gradually decreases first and then increases. 相似文献
9.
William M. Pitts Martin Werrel Marco Fernandez Mary A. Long Evan A. Eisenberg James Filliben Cory D. Runyon 《火与材料》2021,45(1):127-154
Fire spread and growth on real‐scale four cushion mock‐ups of residential upholstered furniture (RUF) were investigated with the goal of identifying whether changes in five classes of materials (barrier, flexible polyurethane foam, polyester fiber wrap, upholstery fabric, and sewing thread), referred to as factors, resulted in statistically significant changes in burning behavior. A fractional factorial experimental design plus practical considerations yielded a test matrix with 20 material combinations. Experiments were repeated a minimum of two times. Measurements included fire spread rates derived from video recordings and heat release rates (HRRs). A total of 13 experimental parameters (3 based on the videos and 10 on the HRR results), referred to as responses, characterized the measurements. Statistical analyses based on Main Effects Plots (main effects) and Block Plots (main effects and factor interactions) were used. The results showed that three of the factors resulted in statistically significant effects on varying numbers of the 13 responses. The Barrier and Fabric factors had the strongest main effects with roughly comparable magnitudes. Foam was statistically significant for fewer of the responses and its overall strength was weaker than for Barrier and Fabric. No statistically significant main effects were identified for Wrap or Thread. Multiple two‐term interactions between factors were identified as being statistically significant. The Barrier*Fabric interaction resulted in the highest number of and strongest statistically significant effects. The existence of two‐term interactions means that it will be necessary to consider their effects in approaches designed to predict the burning behavior of RUF. 相似文献
10.
Aniruddha Nag Mohammed Asif Ali Jiabei Zhou Makoto Ogawa Tatsuo Kaneko 《大分子材料与工程》2021,306(11):2100459
Aromatic and functional polymers with processibility derived from biobased starting materials are prerequisite considering sustainable society. Poly(2,5-benzimidazole)s are rigid-rod polymers to show ultrahigh thermal stability such as flame retardance, while usually suffer from poor solubility. Here, poly(benzimidazole-co-amide)s are synthesized from two biobased monomers, 3,4-diaminobenzoic acid and a semirigid comonomer, 4-aminohydrocinnamic acid. The copolymers with an amide composition of 80 mol% and higher are soluble in widely used polar solvents to fabricate the films keeping high flame retardance, which is comparable with popular high-performance polymers such as aromatic polyimides, polyetheretherketone, polyphenylene sulfide, etc. 相似文献