全文获取类型
收费全文 | 4816篇 |
免费 | 392篇 |
国内免费 | 30篇 |
专业分类
电工技术 | 97篇 |
综合类 | 5篇 |
化学工业 | 1350篇 |
金属工艺 | 169篇 |
机械仪表 | 132篇 |
建筑科学 | 187篇 |
矿业工程 | 12篇 |
能源动力 | 271篇 |
轻工业 | 494篇 |
水利工程 | 39篇 |
石油天然气 | 87篇 |
无线电 | 487篇 |
一般工业技术 | 927篇 |
冶金工业 | 294篇 |
原子能技术 | 34篇 |
自动化技术 | 653篇 |
出版年
2023年 | 48篇 |
2022年 | 92篇 |
2021年 | 161篇 |
2020年 | 136篇 |
2019年 | 201篇 |
2018年 | 283篇 |
2017年 | 203篇 |
2016年 | 211篇 |
2015年 | 176篇 |
2014年 | 208篇 |
2013年 | 451篇 |
2012年 | 245篇 |
2011年 | 313篇 |
2010年 | 264篇 |
2009年 | 259篇 |
2008年 | 234篇 |
2007年 | 175篇 |
2006年 | 186篇 |
2005年 | 118篇 |
2004年 | 114篇 |
2003年 | 146篇 |
2002年 | 99篇 |
2001年 | 60篇 |
2000年 | 49篇 |
1999年 | 48篇 |
1998年 | 106篇 |
1997年 | 55篇 |
1996年 | 49篇 |
1995年 | 44篇 |
1994年 | 33篇 |
1993年 | 31篇 |
1992年 | 20篇 |
1991年 | 27篇 |
1990年 | 16篇 |
1989年 | 17篇 |
1988年 | 24篇 |
1987年 | 40篇 |
1986年 | 22篇 |
1985年 | 25篇 |
1984年 | 24篇 |
1983年 | 22篇 |
1982年 | 13篇 |
1981年 | 17篇 |
1980年 | 23篇 |
1979年 | 13篇 |
1978年 | 20篇 |
1977年 | 18篇 |
1976年 | 24篇 |
1975年 | 20篇 |
1973年 | 14篇 |
排序方式: 共有5238条查询结果,搜索用时 31 毫秒
1.
Domenico Maiorano Jana El Etri Camille Franchet Jean-Sbastien Hoffmann 《International journal of molecular sciences》2021,22(8)
DNA can experience “replication stress”, an important source of genome instability, induced by various external or endogenous impediments that slow down or stall DNA synthesis. While genome instability is largely documented to favor both tumor formation and heterogeneity, as well as drug resistance, conversely, excessive instability appears to suppress tumorigenesis and is associated with improved prognosis. These findings support the view that karyotypic diversity, necessary to adapt to selective pressures, may be limited in tumors so as to reduce the risk of excessive instability. This review aims to highlight the contribution of specialized DNA polymerases in limiting extreme genetic instability by allowing DNA replication to occur even in the presence of DNA damage, to either avoid broken forks or favor their repair after collapse. These mechanisms and their key regulators Rad18 and Polθ not only offer diversity and evolutionary advantage by increasing mutagenic events, but also provide cancer cells with a way to escape anti-cancer therapies that target replication forks. 相似文献
2.
Chemistry and Technology of Fuels and Oils - The article presents studies on the functional stability of pipeline systems for supplying military forces with fuel. The conditions for the functional... 相似文献
3.
Shamila Vibhushan Manuela Bratti Juan Eduardo Montero-Hernndez Alaa El Ghoneimi Marc Benhamou Nicolas Charles Eric Daugas Ulrich Blank 《International journal of molecular sciences》2021,22(1)
A sizable part (~2%) of the human genome encodes for proteases. They are involved in many physiological processes, such as development, reproduction and inflammation, but also play a role in pathology. Mast cells (MC) contain a variety of MC specific proteases, the expression of which may differ between various MC subtypes. Amongst these proteases, chymase represents up to 25% of the total proteins in the MC and is released from cytoplasmic granules upon activation. Once secreted, it cleaves the targets in the local tissue environment, but may also act in lymph nodes infiltrated by MC, or systemically, when reaching the circulation during an inflammatory response. MC have been recognized as important components in the development of kidney disease. Based on this observation, MC chymase has gained interest following the discovery that it contributes to the angiotensin-converting enzyme’s independent generation of angiotensin II, an important inflammatory mediator in the development of kidney disease. Hence, progress regarding its role has been made based on studies using inhibitors but also on mice deficient in MC protease 4 (mMCP-4), the functional murine counterpart of human chymase. In this review, we discuss the role and actions of chymase in kidney disease. While initially believed to contribute to pathogenesis, the accumulated data favor a more subtle view, indicating that chymase may also have beneficial actions. 相似文献
4.
Manal A. Mahdy Sayed H. Kenawy Esmat M.A. Hamzawy Gehan T. El-Bassyouni I.K. El Zawawi 《Ceramics International》2021,47(9):12047-12055
The influence of adding 10, 20 and 30% molar ratio of silicon carbide (SiC) separately to a composite of wollastonite (W) with a fixed content of 10%Fe2O3 prepared by wet precipitation method was studied. The crystal structure of the annealed composite powders was inspected by X-ray diffraction (XRD); revealing multi-phase structure. The highest estimated crystallite size investigated by Scherrer equation of W, SiC, WFe:SiC10, WFe:SiC20 and WFe:SiC30 were 53.89, 54.6, 56.3, 48.5 and 54.6 nm respectively; demonstrating the formation of nanocomposites. Particles shape, size and crystallinity of the samples were studied using high resolution transmission electron microscope (HR-TEM). The band gap Eg values of the nanocomposites increased with SiC content having an intermediate value that lies between that of γ-Fe2O3 (maghemite) and SiC. Ferromagnetic and paramagnetic contributions were observed in the magnetic hysteresis loops for the composites. This study highlighted that the coercive field (Hci) of the composites improved with increasing the SiC content. The innovative wollastonite/Fe2O3/SiC with amended magnetic properties elicited attention due to their promising application in bone filler and industrial purposes. 相似文献
5.
Nadia Chlibi José P.B. Silva Eliana M.F. Vieira Luís M. Goncalves Joaquim Agostinho Moreira Adil Chahboun Hassen Dahman Mário Pereira Maria J.M. Gomes Lassaad El Mir 《Ceramics International》2021,47(16):22594-22603
Spin-coated chalcostibite CuSbS2 thin films (≈500 nm thick) were fabricated and the influence of the drying temperature on the structural, morphological, optical and thermoelectric properties of the films was investigated. Crystalline phase-pure chalcostibite has been obtained for the films dried at 180 °C and 210 °C, while below 180 °C these films are partially amorphous. Surprisingly, at drying temperature of 240 °C, a CuxS secondary phase appeared. The increase of the drying temperature leads to the increase of the particle size and the decrease of the optical band gap, which is interesting for optoelectronic applications. The highest power factor value was achieved for the film dried at 210 °C, due to the inexistence of secondary phases, which allowed realizing a stable thermoelectric touch sensor with a Vsignal/noise of 5. In addition, this film was tested as a photovoltaic (PV) device and a power conversion efficiency (PCE) of 0.030% with an open-circuit voltage (VOC) of 0.36 V, a short-circuit current density (JSC) of 0.278 mAcm?2 and a fill factor (FF) of 0.27 were obtained. Therefore, this work evidences a pathway toward developing bi-functional devices with simultaneously thermoelectric touch sensor and photovoltaic functions. 相似文献
6.
Neural Processing Letters - In this paper, by employing contraction mapping principle theorem and by finding suitable Lyapunov–Krasovskii functional, some sufficient conditions are given for... 相似文献
7.
By using first-principles calculations we studied the electronic, optical and magnetic properties of ZnO co-doped with Eu and Pm. In this calculation, we used Wien2k code based on full potential linearized augmented plane waves (FP-LAPW) method with the modified Becke-Johnson (mBJ) approximation. This correction gives good band gap compared to experimental band gap. The introduction of Eu and Pm codoping leads to an increase in the band gap. Electrons can transit easily from the valence band to the conduction band, which results in an enhancement of visible light absorption in a wider absorption range. Absorption spectra reach a high value in visible and infrared light regions. With the significance of the obtained results, the studied compounds may potentially find spintronic and optoelectronic applications. 相似文献
8.
Ahmed El Kholy Khairy Fakhry Osayed Abu-Elyazeed 《Journal of Nuclear Science and Technology》2019,56(3):291-299
Heat transfer study of nanofluids as coolant in SCWRs core has been performed at Helwan University. A thermal hydraulic code has been produced to study the effect of TiO2 nanofluid water based as a coolant with comparison with pure water as a coolant. Various volume fractions of nanoparticles TiO2 (2, 6 and 10%) were used in order to investigate its effects on reactor thermalhydraulic characteristics. Based on Parameters of a SCW Canadian Deuterium Uranium nuclear reactor (CANDU), the fuel assembly was modeled to study the effect of nanoparticles volume fraction on thermos-physical properties of basic fluid and the temperature distribution of fuel, cladding surface and coolant in axial direction. The theoretical results showed that the density, viscosity and thermal conductivity of the coolant increases with the increase of nanoparticles volume fraction, contrasting to specific heat, which decreases with the increase in nanoparticles volume fraction. 相似文献
9.
More than three million tons of sulfide tailings were discarded without any protection for more than 36 years at the since-abandoned Kettara mine. The impact of these tailings as well as the coarse wastes disorderly dumped on the surface site is highlighted by the elevated sulfate levels in the wells downstream of the wastes. Kinetic tests carried out on these sulfide tailings over 10 years ago, showed similar trends in metal dissolution despite large difference in test duration (21 and 53 weeks for the weathering and humidity cell tests, respectively). 40% of the sulfate release occurred in the first 3 weeks of the humidity test. However, in this study, the elevated sulfate levels in the groundwater was shown not be linked to the tailings, where the original sulfide material is still present under an oxidized layer of 10 cm–1.2 m. Thus, kinetic test results should not be extrapolated to field scale without accounting for site-specific factors, especially particle size and climate. 相似文献
10.