全文获取类型
收费全文 | 323369篇 |
免费 | 3331篇 |
国内免费 | 916篇 |
专业分类
电工技术 | 6454篇 |
综合类 | 275篇 |
化学工业 | 45062篇 |
金属工艺 | 15802篇 |
机械仪表 | 12960篇 |
建筑科学 | 7401篇 |
矿业工程 | 1610篇 |
能源动力 | 7834篇 |
轻工业 | 22193篇 |
水利工程 | 3222篇 |
石油天然气 | 4601篇 |
武器工业 | 15篇 |
无线电 | 40869篇 |
一般工业技术 | 68165篇 |
冶金工业 | 54191篇 |
原子能技术 | 6087篇 |
自动化技术 | 30875篇 |
出版年
2021年 | 2167篇 |
2020年 | 1561篇 |
2019年 | 1916篇 |
2018年 | 11291篇 |
2017年 | 11912篇 |
2016年 | 7928篇 |
2015年 | 2730篇 |
2014年 | 4043篇 |
2013年 | 11549篇 |
2012年 | 8751篇 |
2011年 | 16586篇 |
2010年 | 14529篇 |
2009年 | 14450篇 |
2008年 | 14620篇 |
2007年 | 16565篇 |
2006年 | 7445篇 |
2005年 | 10035篇 |
2004年 | 8204篇 |
2003年 | 8097篇 |
2002年 | 6660篇 |
2001年 | 6587篇 |
2000年 | 6112篇 |
1999年 | 6425篇 |
1998年 | 16527篇 |
1997年 | 11427篇 |
1996年 | 8823篇 |
1995年 | 6630篇 |
1994年 | 5946篇 |
1993年 | 5884篇 |
1992年 | 4154篇 |
1991年 | 4054篇 |
1990年 | 3871篇 |
1989年 | 3655篇 |
1988年 | 3573篇 |
1987年 | 3031篇 |
1986年 | 2954篇 |
1985年 | 3215篇 |
1984年 | 2934篇 |
1983年 | 2840篇 |
1982年 | 2641篇 |
1981年 | 2547篇 |
1980年 | 2471篇 |
1979年 | 2315篇 |
1978年 | 2112篇 |
1977年 | 2608篇 |
1976年 | 3572篇 |
1975年 | 1772篇 |
1974年 | 1735篇 |
1973年 | 1674篇 |
1972年 | 1473篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Yilin Yang Siddarth K. Achar John R. Kitchin 《American Institute of Chemical Engineers》2022,68(6):e17653
The degree of rate control (DRC) quantitatively identifies the kinetically relevant (sometimes known as rate-limiting) steps of a complex reaction network. This concept relies on derivatives which are commonly implemented numerically, for example, with finite differences (FDs). Numerical derivatives are tedious to implement, and can be problematic, and unstable or unreliable. In this study, we demonstrate the use of automatic differentiation (AD) in the evaluation of the DRC. AD libraries are increasingly available through modern machine learning frameworks. Compared with the FDs, AD provides solutions with higher accuracy with lower computational cost. We demonstrate applications in steady-state and transient kinetics. Furthermore, we illustrate a hybrid local-global sensitivity analysis method, the distributed evaluation of local sensitivity analysis, to assess the importance of kinetic parameters over an uncertain space. This method also benefits from AD to obtain high-quality results efficiently. 相似文献
72.
73.
74.
Dr. Omer K. Rasheed Cassandra Buhl Dr. Jay T. Evans Dr. Kendal T. Ryter 《ChemMedChem》2021,16(8):1246-1251
Mincle agonists have been shown to induce inflammatory cytokine production, such as tumor necrosis factor-alpha (TNF) and promote the development of a Th1/Th17 immune response that might be crucial to development of effective vaccination against pathogens such as Mycobacterium tuberculosis. As an expansion of our previous work, a library of 6,6′-amide and sulfonamide α,α-d -trehalose compounds with various substituents on the aromatic ring was synthesized efficiently in good to excellent yields. These compounds were evaluated for their ability to activate the human C-type lectin receptor Mincle by the induction of cytokines from human peripheral blood mononuclear cells. A preliminary structure–activity relationship (SAR) of these novel trehalose diamides and sulfonamides revealed that aryl amide-linked trehalose compounds demonstrated improved activity and relatively high potency cytokine production compared to the Mincle ligand trehalose dibehenate adjuvant (TDB) and the natural ligand trehalose dimycolate (TDM) inducing dose-dependent and human-Mincle-specific stimulation in a HEK reporter cell line. 相似文献
75.
76.
Breslavs’kyi D. V. Metel’yov V. O. Morachkovs’kyi O. K. Tatarinova O. A. 《Strength of Materials》2019,51(5):753-760
Strength of Materials - Creep constitutive equations have been derived for the materials that exhibit the properties of orthotropy (transversal isotropy) and transient creep under cyclic loading. A... 相似文献
77.
Manika Chaudhary Milan Singh Ashwani Kumar Yogendra K. Gautam Anil K. Malik Yogesh Kumar Beer Pal Singh 《Ceramics International》2021,47(2):2094-2106
The current research work presents a facile and cost–effective co-precipitation method to prepare doped (Co & Fe) CuO and undoped CuO nanostructures without usage of any type of surfactant or capping agents. The structural analysis reveals monoclinic crystal structure of synthesized pure CuO and doped-CuO nanostructures. The effect of different morphologies on the performance of supercapacitors has been found in CV (cyclic voltammetry) and GCD (galvanic charge discharge) investigations. The specific capacitances have been obtained 156 (±5) Fg?1, 168(±5) Fg?1 and 186 (±5) Fg?1 for CuO, Co-doped CuO and Fe-doped CuO electrodes, respectively at scan rate of 5 mVs?1, while it is found to be 114 (±5) Fg?1, 136 (±5) Fg?1 and 170 (±5) Fg?1 for CuO, Co–CuO and Fe–CuO, respectively at 0.5 Ag-1 as calculated from the GCD. The super capacitive performance of the Fe–CuO nanorods is mainly attributed to the synergism that evolves between CuO and Fe metal ion. The Fe-doped CuO with its nanorods like morphology provides superior specific capacitance value and excellent cyclic stability among all studied nanostructured electrodes. Consequently, it motivates to the use of Fe-doped CuO nanostructures as electrode material in the next generation energy storage devices. 相似文献
78.
Environmental concerns continue to pose the challenge to replace petroleum-based products with renewable ones completely or at least partially while maintaining comparable properties. Herein, rigid polyurethane (PU) foams were prepared using soy-based polyol for structural and thermal insulation applications. Cell size, density, thermal resistivity, and compression force deflection (CFD) values were evaluated and compared with that of petroleum-based PU foam Baydur 683. The roles of different additives, that is, catalyst, blowing agent, surfactants, and different functionalities of polyol on the properties of fabricated foam were also investigated. For this study, dibutyltin dilaurate was employed as catalyst and water as environment friendly blowing agent. Their competitive effect on density and cell size of the PU foams were evaluated. Five different silicone-based surfactants were employed to study the effect of surface tension on cell size of foam. It was also found that 5 g of surfactant per 100 g of polyol produced a foam with minimum surface tension and highest thermal resistivity (R value: 26.11 m2·K/W). However, CFD values were compromised for higher surfactant loading. Additionally, blending of 5 g of higher functionality soy-based polyol improved the CFD values to 328.19 kPa, which was comparable to that of petroleum-based foam Baydur 683. 相似文献
79.
Microsystem Technologies - The strategy for analysis of noise generated in the analog circuit is presented here. Further, methodology for optimization of noise to improve the performance of the... 相似文献
80.
Sophia X. Sui Lana J. Williams Kara L. Holloway-Kew Natalie K. Hyde Julie A. Pasco 《International journal of molecular sciences》2021,22(1)
Sarcopenia is the loss of skeletal muscle mass and function with advancing age. It involves both complex genetic and modifiable risk factors, such as lack of exercise, malnutrition and reduced neurological drive. Cognitive decline refers to diminished or impaired mental and/or intellectual functioning. Contracting skeletal muscle is a major source of neurotrophic factors, including brain-derived neurotrophic factor, which regulate synapses in the brain. Furthermore, skeletal muscle activity has important immune and redox effects that modify brain function and reduce muscle catabolism. The identification of common risk factors and underlying mechanisms for sarcopenia and cognition may allow the development of targeted interventions that slow or reverse sarcopenia and also certain forms of cognitive decline. However, the links between cognition and skeletal muscle have not been elucidated fully. This review provides a critical appraisal of the literature on the relationship between skeletal muscle health and cognition. The literature suggests that sarcopenia and cognitive decline share pathophysiological pathways. Ageing plays a role in both skeletal muscle deterioration and cognitive decline. Furthermore, lifestyle risk factors, such as physical inactivity, poor diet and smoking, are common to both disorders, so their potential role in the muscle–brain relationship warrants investigation. 相似文献