全文获取类型
收费全文 | 708篇 |
免费 | 16篇 |
国内免费 | 12篇 |
学科分类
工业技术 | 736篇 |
出版年
2023年 | 3篇 |
2022年 | 5篇 |
2021年 | 17篇 |
2020年 | 9篇 |
2019年 | 10篇 |
2018年 | 10篇 |
2017年 | 15篇 |
2016年 | 10篇 |
2015年 | 10篇 |
2014年 | 22篇 |
2013年 | 57篇 |
2012年 | 21篇 |
2011年 | 32篇 |
2010年 | 21篇 |
2009年 | 28篇 |
2008年 | 37篇 |
2007年 | 40篇 |
2006年 | 30篇 |
2005年 | 24篇 |
2004年 | 21篇 |
2003年 | 26篇 |
2002年 | 28篇 |
2001年 | 12篇 |
2000年 | 14篇 |
1999年 | 22篇 |
1998年 | 17篇 |
1997年 | 15篇 |
1996年 | 18篇 |
1995年 | 9篇 |
1994年 | 8篇 |
1993年 | 14篇 |
1992年 | 15篇 |
1991年 | 11篇 |
1990年 | 9篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 10篇 |
1983年 | 4篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1980年 | 7篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1977年 | 6篇 |
1976年 | 5篇 |
1974年 | 4篇 |
1972年 | 4篇 |
排序方式: 共有736条查询结果,搜索用时 78 毫秒
731.
Permanent magnet synchronous motors are widely used for several industrial applications. Some applications such as electric vehicles and compressor drives require a constant power operation. The operating limits and the constant power speed range deeply depend on the machine parameters. The relationships between the motor parameters and the operating performance have been theoretically examined. This paper examines the performances of the prototype synchronous motors, where the stator structure and the rotor structure of all motors are the same. The permanent magnets are inserted into the rotor slits and the volume of the permanent magnet is adjusted to control the magnet‐flux linkage. The effects of adding the magnet to the rotor on the machine parameters and the operating performance are examined based on the various experimental results. The prototype motor has flexibility as to speed versus power performance by adjusting the volume of the permanent magnet. The theoretical results with respect to the operating limits and the motor parameters are also confirmed experimentally. © 2000 Scripta Technica, Electr Eng Jpn, 131(4): 70–77, 2000 相似文献
732.
Natural convection heat transfer and flow structure in an anisotropic porous medium in a square cavity saturated with a Boussinesq fluid have been studied analytically and numerically. Based on an asymptotic analysis, three distinctive regimes are found depending on the magnitude of the permeability ratio K. In the vicinity of K = 1 the average Nusselt number and fluid velocity are scaled with (KRa) 1/2 when either K or the Rayleigh number Ra is varied. In the limit of K → 0 the heat transfer across the cavity approaches the conductive state, and the convecting velocity, which is primarily in the vertical direction, is scaled with KRa. At the other end of the spectrum, namely, K → ∞, the average Nusselt number and the convecting velocity are scaled with Ra and independent of K. The asymptotic results are verified with two‐dimensional numerical calculations. The ranges of K of the respective regimes are also determined based on the numerical results. © 2000 Scripta Technica, Heat Trans Asian Res, 29(5): 373–384, 2000 相似文献
733.
This paper is concerned with the theoretical basis for the determination of the condensation coefficient of vapor by means of a shock tube. Film condensation on the shock-tube endwall behind a reflected shock wave is analyzed on the basis of the first author's gas-dynamics theory. It is clarified that there exists a transition phenomenon during the growth of a liquid film, that is, the liquid film grows in proportion to time immediately after the reflection of the shock wave, and after a transition time, it grows in proportion to the square root of time. The transition phenomenon between these growths is caused by the change in heat conduction characteristics at the endwall. The reason why the condensation coefficient must be determined before the transition is clarified. © 1997 Scripta Technica, Inc. Heat Trans Jpn Res 25(3): 166–177, 1996 相似文献
734.
The influence of tetraalkylammonium salts, viz., tetraethylammonium, tetrapropylammonium, and tetrabutylammonium bromides (0.005, 0.010, 0.015 mol kg−1) on the micellar behavior of aqueous solutions of the cationic surfactant cetyltrimethylammonium bromide (CTAB, 0.2–2 mmol kg−1) over the 298.15–313.15 K temperature range has been studied by conductometric method. From conductivity versus surfactant concentration plots, the critical micelle concentration (CMC) of CTAB has been determined, which shows that the tetraalkylammonium bromides promote the formation of CTAB aggregates. Further, from the temperature dependence of CMC values, the degree of ionization, the counterion binding constant along with some thermodynamic parameters of micellization, such as standard free energy change (), standard enthalpy change (), standard entropy change () have been calculated. From the values of , and , it has been concluded that our ternary system is both enthalpy as well as entropy controlled. Similar CMC values were obtained from UV–Visible spectrometry measurements, using pyrene as a probe at ambient temperature. Also 1H-NMR and FTIR methods give a greater understanding of the molecular scale interactions between the tetraalkylammonium bromides and the cationic surfactant. 相似文献
735.
Yushi Fujita Atsushi Sakuda Yuki Hasegawa Minako Deguchi Kota Motohashi Ding Jiong Hirofumi Tsukasaki Shigeo Mori Masahiro Tatsumisago Akitoshi Hayashi 《Small (Weinheim an der Bergstrasse, Germany)》2023,19(36):2302179
All-solid-state lithium–sulfur (Li/S) batteries are promising next-generation energy-storage devices owing to their high capacities and long cycle lives. The Li2S active material used in the positive electrode has a high theoretical capacity; consequently, nanocomposites composed of Li2S, solid electrolytes, and conductive carbon can be used to fabricate high-energy-density batteries. Moreover, the active material should be constructed with both micro- and nanoscale ion-conduction pathways to ensure high power. Herein, a Li2S–Li2O–LiI positive electrode is developed in which the active material is dispersed in an amorphous matrix. Li2S–Li2O–LiI exhibits high charge–discharge capacities and a high specific capacity of 998 mAh g−1 at a 2 C rate and 25 °C. X-ray photoelectron spectroscopy, X-ray diffractometry, and transmission electron microscopy observation suggest that Li2O–LiI provides nanoscale ion-conduction pathways during cycling that activate Li2S and deliver large capacities; it also exhibits an appropriate onset oxidation voltage for high capacity. Furthermore, a cell with a high areal capacity of 10.6 mAh cm–2 is demonstrated to successfully operate at 25 °C using a Li2S–Li2O–LiI positive electrode. This study represents a major step toward the commercialization of all-solid-state Li/S batteries. 相似文献
736.
Arvind Negi Anne Sophie Voisin-Chiret 《Chembiochem : a European journal of chemical biology》2022,23(12):e202100689
Apoptosis is a highly regulated cellular process. Aberration in apoptosis is a common characteristic of various disorders. Therefore, proteins involved in apoptosis are prime targets in multiple therapies. Bcl-xL is an antiapoptotic protein. Compared to other antiapoptotic proteins, the expression of Bcl-xL is common in solid tumors and, to an extent, in some leukemias and lymphomas. The overexpression of Bcl-xL is also linked to survival and chemoresistance in cancer and senescent cells. Therefore, Bcl-xL is a promising anticancer and senolytic target. Various nanomolar range Bcl-xL inhibitors have been developed. ABT-263 was successfully identified as a Bcl-xL/Bcl-2 dual inhibitor. But it failed in the clinical trial (phase-II) because of its on-target platelet toxicity, which also implies an essential role of Bcl-xL protein in the survival of human platelets. Classical Bcl-xL inhibitor designs utilize occupancy-driven pharmacology with typical shortcomings (such as dose-dependent off-target and on-target platelet toxicities). Hence, event-driven pharmacology-based approaches, such as proteolysis targeting chimeras (PROTACs) and SNIPERs (specific non-genetic IAP-based protein erasers) have been developed. The development of Bcl-xL based PROTACs was expected, as 600 E3-ligases are available in humans, while some (such as cereblon (CRBN), von Hippel-Lindau (VHL)) are relatively less expressed in platelets. Therefore, E3 ligase ligand-based Bcl-xL PROTACs (CRBN: XZ424, XZ739; VHL: DT2216, PZ703b, 753b) showed a significant improvement in platelet therapeutic index than their parent molecules ( ABT-263 : DT2216, PZ703b, 753b, XZ739, PZ15227; A1155463 : XZ424). Other than their distinctive pharmacology, PROTACs are molecularly large, which limits their cell permeability and plays a role in improving their cell selectivity. We also discuss prodrug-based approaches, such as antibody-drug conjugates ( ABBV-155 ), phosphate prodrugs ( APG-1252 ), dendrimer conjugate ( AZD0466 ), and glycosylated conjugates ( Nav-Gal ). Studies of in-vitro, in-vivo, structure-activity relationships, biophysical characterization, and status of preclinical/clinical inhibitors derived from these strategies are also discussed in the review. 相似文献