全文获取类型
收费全文 | 2711篇 |
免费 | 146篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 59篇 |
综合类 | 2篇 |
化学工业 | 494篇 |
金属工艺 | 34篇 |
机械仪表 | 55篇 |
建筑科学 | 91篇 |
矿业工程 | 4篇 |
能源动力 | 65篇 |
轻工业 | 182篇 |
水利工程 | 20篇 |
石油天然气 | 3篇 |
无线电 | 295篇 |
一般工业技术 | 555篇 |
冶金工业 | 650篇 |
原子能技术 | 19篇 |
自动化技术 | 332篇 |
出版年
2023年 | 36篇 |
2022年 | 46篇 |
2021年 | 84篇 |
2020年 | 61篇 |
2019年 | 62篇 |
2018年 | 62篇 |
2017年 | 46篇 |
2016年 | 84篇 |
2015年 | 72篇 |
2014年 | 79篇 |
2013年 | 132篇 |
2012年 | 166篇 |
2011年 | 211篇 |
2010年 | 143篇 |
2009年 | 109篇 |
2008年 | 139篇 |
2007年 | 127篇 |
2006年 | 102篇 |
2005年 | 74篇 |
2004年 | 66篇 |
2003年 | 52篇 |
2002年 | 41篇 |
2001年 | 31篇 |
2000年 | 28篇 |
1999年 | 32篇 |
1998年 | 90篇 |
1997年 | 68篇 |
1996年 | 47篇 |
1995年 | 42篇 |
1994年 | 27篇 |
1993年 | 34篇 |
1992年 | 21篇 |
1991年 | 34篇 |
1990年 | 24篇 |
1989年 | 22篇 |
1988年 | 24篇 |
1987年 | 25篇 |
1986年 | 14篇 |
1985年 | 25篇 |
1984年 | 29篇 |
1983年 | 20篇 |
1982年 | 20篇 |
1981年 | 17篇 |
1980年 | 13篇 |
1979年 | 20篇 |
1977年 | 19篇 |
1976年 | 35篇 |
1974年 | 14篇 |
1972年 | 10篇 |
1966年 | 12篇 |
排序方式: 共有2860条查询结果,搜索用时 15 毫秒
101.
Pooja Kaur Dr. Alice Johnson Joshua Northcote-Smith Dr. Chunxin Lu Dr. Kogularamanan Suntharalingam 《Chembiochem : a European journal of chemical biology》2020,21(24):3618-3624
Immunogenic cell death (ICD) offers a method of stimulating the immune system to attack and remove cancer cells. We report a copper(II) complex containing a Schiff base ligand and a polypyridyl ligand, 4 , capable of inducing ICD in breast cancer stem cells (CSCs). Complex 4 kills both bulk breast cancer cells and breast CSCs at sub-micromolar concentrations. Notably, 4 exhibits greater potency (one order of magnitude) towards breast CSCs than salinomycin (an established breast CSC-potent agent) and cisplatin (a clinically approved anticancer drug). Epithelial spheroid studies show that 4 is able to selectively inhibit breast CSC-enriched HMLER-shEcad spheroid formation and viability over non-tumorigenic breast MCF10 A spheroids. Mechanistic studies show that 4 operates as a Type II ICD inducer. Specifically, 4 readily enters the endoplasmic reticulum (ER) of breast CSCs, elevates intracellular reactive oxygen species (ROS) levels, induces ER stress, evokes damage-associated molecular patterns (DAMPs), and promotes breast CSC phagocytosis by macrophages. As far as we are aware, 4 is the first metal complex to induce ICD in breast CSCs and promote their engulfment by immune cells. 相似文献
102.
Jason M. Lonergan Charmayne Lonergan Joshua Silverstein Pornsinee Cholsaipant John McCloy 《Journal of the American Ceramic Society》2020,103(6):3610-3619
Sulfur trioxide (SO3) additions, up to 3.0 mass%, were systematically investigated for effects on the physical properties of sodium borosilicate glass melted in air, with a sulfur-free composition of 50SiO2–10Al2O3–12B2O3–21Na2O–7CaO (mass%). Solubility measurements, using electron microscopy chemical analysis, determined the maximum loading to be ~1.2 mass% SO3. It was found that measured sulfur (here as sulfate) additions up to 1.18 mass% increased the glass transition temperature by 3%, thermal diffusivity by 11%, heat capacity by 10%, and thermal conductivity by 20%, and decreased the mass density by 1%. Structural analysis, performed with Raman spectroscopy, indicated that the borosilicate network polymerized with sulfur additions up to 3.0 mass%, presumably due to Na2O being required to charge compensate the ionic additions, thus becoming unavailable to form non-bridging oxygen in the silicate network. It is postulated that this increased cross-linking of the borosilicate backbone led to a structure with higher dimensionality and average bond energy. This increased the mean free paths and vibration frequency of the phonons, which resulted in the observed increase in thermal properties. 相似文献
103.
Dr. Joshua A. Visser Dr. Deborah Yager Dr. Schuyler A. Chambers Dr. Ji Youn Lim Xujun Cao Prof. Lynette Cegelski 《Chembiochem : a European journal of chemical biology》2023,24(18):e202300266
Escherichia coli and other Enterobacteriaceae thrive in robust biofilm communities through the coproduction of curli amyloid fibers and phosphoethanolamine cellulose. Curli promote adhesion to abiotic surfaces and plant and human host tissues and are associated with pathogenesis in urinary tract infection and food-borne illness. The production of curli in the host has also been implicated in the pathogenesis of neurodegenerative diseases. We report that the natural product nordihydroguaiaretic acid (NDGA) is effective as a curlicide in E. coli. NDGA prevents CsgA polymerization in vitro in a dose-dependent manner. NDGA selectively inhibits cell-associated curli assembly and inhibits uropathogenic E. coli biofilm formation. More broadly, this work emphasizes the ability to evaluate and identify bioactive amyloid assembly inhibitors by using the powerful gene-directed amyloid biogenesis machinery in E. coli. 相似文献
104.
The crystallization of poly(phenylene sulfide) (PPS) in a polymer–magnetic Nd—Fe—B powder suspension was studied. Isothermal crystallization behavior was analyzed by way of differential scanning calorimetry, and the kinetics were described via the Avrami equation. The Avrami parameters and the crystallization times were strongly affected by both the particle size and the presence of a coupling agent coated on the filler particles. The small Nd—Fe—B particles exhibited long induction and half‐times, whereas the large particles tended to have short crystallization times. Particles ranging from 38 to 150 μ appeared to have similar crystallization times and to have no significant change in the value of Avrami index with melt crystallization temperature. As a result of these analyses, the dynamic mechanical properties were determined to correlate the fundamental polymer crystallization characteristics and the physical properties of the PPS binder. The enhancement of the wetting of the filler to the binder was promoted through the coupling agent, as confirmed by dynamic mechanical testing performed on the samples. The storage modulus typically decreased because of the presence of the uncoated small particles. Conversely, the loss modulus was enhanced because of the presence of the coated small particles in the PPS binder. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1091–1102, 2002 相似文献
105.
Hendrix JA Shimshock SJ Shutske GM Tomer JD Kapples KJ Palermo MG Corbett TJ Vargas HM Kafka S Brooks KM Laws-Ricker L Lee DK de Lannoy I Bordeleau M Rizkalla G Owolabi J Kamboj RK 《Chembiochem : a European journal of chemical biology》2002,3(10):999-1009
A new class of potent dopamine D(4) antagonists was discovered with selectivity over dopamine D(2) and the alpha-1 adrenoceptor. The lead compound was discovered by screening our compound collection. The structure-activity relationships of substituted isoindoline rings and the chirality about the hydroxymethyl side chain were explored. The isoindoline analogues showed modest differences in potency and selectivity. The S enantiomer proved to be the more potent enantiomer at the D(4) receptor. Several analogues with greater than 100-fold selectivity for D(4) over D(2) and the alpha-1 adrenoreceptor were discovered. Several selective analogues were active in vivo upon oral or intraperitoneal administration. A chiral synthesis starting from either D- or L-O-benzylserine is also described. 相似文献
106.
A proposed method for estimating the electrical conductivity of cement paste pore solution at 25 °C is based on the concentrations of OH−, K+ and Na+. The approach uses an equation that is a function of the solution ionic strength, and requires a single coefficient for each ionic species. To test the method, the conductivity of solutions containing mixtures of potassium hydroxide and sodium hydroxide with molar ratios of 4:1, 2:1 and 1:1, and having ionic strengths varying from 0.15 to 2.00 mol/l were measured in the laboratory and compared to predicted values. The proposed equation predicts the conductivity of the solutions to within 8% over the concentration range investigated. By comparison, the dilute electrolyte assumption that conductivity is linearly proportional to concentration is in error by 36% at 1 mol/l and in error by 55% at 2 mol/l. The significance and utility of the proposed equation is discussed in the context of predicting ionic transport in cement-based systems. 相似文献
107.
Peter C. Guschl Joshua U. Otaigbe Chun‐Keung Loong 《Polymer Engineering and Science》2004,44(9):1692-1701
The phase behavior of novel, binary organic‐inorganic hybrids consisting of an ultra‐low Tg tin‐based phosphate glass (Pglass) and polystyrene (PS) was investigated. Dynamic mechanical analysis (DMA) revealed that the glass transition peaks of the PS changed slightly with Pglass volume fraction, leading to a broad peak at the phase inversion point. The phase inversion and degree of phase continuity of the hybrid were studied through solvent extraction, optical/scanning electron microscopy, and dynamic rheology. The Jordhamo and Utracki viscosity ratio models provided reliable estimates of the inversion point. Torque rheometry revealed a trend toward linear additivity within the temperature range 200°C–230°C. Small‐angle neutron scattering experiments gave further evidence of the hybrid phase incompatibility. The results of this study point to a promising new class of blend materials with the potential to present a unique combination of properties impossible to achieve with classical polymer blends. Polym. Eng. Sci. 44:1692–1701, 2004. © 2004 Society of Plastics Engineers. 相似文献
108.
Snyder JW Zebger I Gao Z Poulsen L Frederiksen PK Skovsen E McIlroy SP Klinger M Andersen LK Ogilby PR 《Accounts of chemical research》2004,37(11):894-901
The lowest excited electronic state of molecular oxygen, singlet molecular oxygen (a1Deltag), is an intermediate in many chemical and biological processes. Tools and methods have been developed to create singlet-oxygen-based optical images of heterogeneous samples that range from phase-separated polymers to biological cells. Such images provide unique insight into a variety of oxygen-dependent phenomena, including the photoinitiated death of cells. 相似文献
109.
Yong-Le Pan Aimable Kalume Chuji Wang Joshua L. Santarpia 《Aerosol science and technology》2018,52(1):13-18
We describe a new method for focusing and concentrating a stream of moving micron-sized aerosol particles in air. The focusing and concentrating process is carried out by the combined drag force and optical force that is generated by a double-layer co-axial nozzle and a focused doughnut-shaped hollow laser beam, respectively. This method should supply a new tool for aerosol science and related research.
Copyright © 2018 American Association for Aerosol Research 相似文献
110.
Hydrogenation of vegetable oils using mixtures of supercritical carbon dioxide and hydrogen 总被引:5,自引:0,他引:5
Jerry W. King Russell L. Holliday Gary R. List Janet M. Snyder 《Journal of the American Oil Chemists' Society》2001,78(2):107-113
Hydrogenation of vegetable oils under supercritical conditions can involve a homogeneous one-phase system, or alternatively
two supercritical components in the presence of a condensed phase consisting of oil and a solid catalyst. The former operation
is usually conducted in flow reactors while the latter mode is more amenable to stirred, batch-reactor technology. Although
many advantages have been cited for the one-phase hydrogenation of oils or oleochemicals using supercritical carbon dioxide
or propane, its ultimate productivity is limited by the oil solubility in the supercritical fluid phase as well as unconventional
conditions that affect the hydrogenation. In this study, a dead-end reactor has been utilized in conjunction with a head-space
consisting of either a binary fluid phase consisting of varying amounts of carbon dioxide mixed with hydrogen or neat hydrogen
for comparison purposes. Reaction pressures up to 2000 psi and temperatures in the range of 120–140°C have been utilized with
a conventional nickel catalyst to hydrogenate soybean oil. Depending on the chosen reaction conditions, a wide variety of
end products can be produced having different iodine values, percentage trans fatty acid content, and dropping points or solid fat indices. Although addition of carbon dioxide to the fluid phase containing
hydrogen retards the overall reaction rate in most of the studied cases, the majority of products have low trans fatty acid content, consistent with a nonselective mode of hydrogenation. 相似文献