全文获取类型
收费全文 | 38911篇 |
免费 | 1323篇 |
国内免费 | 733篇 |
专业分类
电工技术 | 2027篇 |
综合类 | 2346篇 |
化学工业 | 6074篇 |
金属工艺 | 2475篇 |
机械仪表 | 3714篇 |
建筑科学 | 3274篇 |
矿业工程 | 2637篇 |
能源动力 | 1298篇 |
轻工业 | 4540篇 |
水利工程 | 1347篇 |
石油天然气 | 4577篇 |
武器工业 | 28篇 |
无线电 | 779篇 |
一般工业技术 | 749篇 |
冶金工业 | 1444篇 |
原子能技术 | 126篇 |
自动化技术 | 3532篇 |
出版年
2023年 | 79篇 |
2022年 | 312篇 |
2021年 | 420篇 |
2020年 | 506篇 |
2019年 | 550篇 |
2018年 | 424篇 |
2017年 | 273篇 |
2016年 | 164篇 |
2015年 | 151篇 |
2014年 | 320篇 |
2013年 | 408篇 |
2012年 | 317篇 |
2011年 | 1362篇 |
2010年 | 901篇 |
2009年 | 1101篇 |
2008年 | 1252篇 |
2007年 | 1555篇 |
2006年 | 2141篇 |
2005年 | 2181篇 |
2004年 | 2655篇 |
2003年 | 2888篇 |
2002年 | 3424篇 |
2001年 | 3370篇 |
2000年 | 2904篇 |
1999年 | 2979篇 |
1998年 | 2116篇 |
1997年 | 1900篇 |
1996年 | 1349篇 |
1995年 | 963篇 |
1994年 | 622篇 |
1993年 | 414篇 |
1992年 | 243篇 |
1991年 | 144篇 |
1990年 | 122篇 |
1989年 | 94篇 |
1988年 | 55篇 |
1987年 | 32篇 |
1986年 | 13篇 |
1985年 | 19篇 |
1984年 | 20篇 |
1983年 | 27篇 |
1982年 | 15篇 |
1981年 | 14篇 |
1980年 | 14篇 |
1979年 | 22篇 |
1978年 | 19篇 |
1977年 | 12篇 |
1976年 | 20篇 |
1973年 | 11篇 |
1972年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Virginija Sacevičienė Milda Jucienė Vaida Dobilaitė Valentina Krylova Skirma Žalenkienė Nijolė Dukštienė Raimondas Bliūdžius 《应用聚合物科学杂志》2019,136(21):47523
The aim of this work was to investigate the physical and mechanical performance of architectural polyester (PES)–poly(vinyl chloride) (PVC) membranes exposed to different artificial aging conditions. Two commercially available architectural membranes were chosen as research objects. The durability of the PES/PVC fabrics was evaluated by the loss in mechanical performance, scanning electron microscopy, and X-ray diffraction analysis in order to understand the effect of the degradation agents on the surface of the membranes. The mechanical performance of the PES/PVC membranes was unchanged. Scanning electron microscopy images of the tested materials showed initial cracks after aging. The X-ray fluorescence analysis showed that at the time of aging, the amount of Cl and Si decreased slightly, while Ti decreased by half, and Ca by volume increased twice. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47523. 相似文献
3.
Aleksandar Miletić Peter Panjan Miha Čekada Lazar Kovačević Pal Terek Janez Kovač Goran Dražič Branko Škorić 《Ceramics International》2021,47(2):2022-2033
With the goal to produce a hard and tough coating intended for tribological applications, CrAlN/TiSiN nanolayer coating was prepared by alternative deposition of CrAlN and TiSiN layers. In the first part of the article, a detailed study of phase composition, microstructure, and layer structure of CrAlN/TiSiN coating is presented. In the second part, its mechanical properties, fracture and tribological behavior are compared to the nanocomposite TiSiN coating. An industrial magnetron sputtering unit was used for coating deposition. X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy were used for compositional and microstructural analysis. Mechanical properties and fracture behavior were studied by instrumented indentation and focused ion beam techniques. Tribological properties were evaluated by ball-on-disk test in a linear reciprocal mode. A complex layer structure was found in the nanolayer coating. The TiSiN layers were epitaxially stabilized inside the coating which led to formation of dislocations at interfaces, to introduction of disturbances in the coating growth, and as a result, to development of fine-grained columnar microstructure. Indentation load required for the onset of fracture was twice lower for the nanolayer CrAlN/TiSiN, compared to the nanocomposite TiSiN coating. This agrees very well with their mechanical properties, with H3/E2 being twice higher for the TiSiN coating. However, the nanolayer coating experienced less severe damage, which had a strong impact on tribological behavior. A magnitude of order lower wear rate and four times lower steady state friction coefficient were found for the nanolayer coating. 相似文献
4.
5.
针对和成矿业井下原矿含泥量和含水量较大,且矿泥中存在绿泥石、高岭土等黏土类矿物,造成供矿系统粘堵严重,系统台时量仅为设计水平一半的问题,对原矿进行了洗矿工艺研究。通过洗矿工艺,将原矿中的矿块和矿泥分离,实现矿块和矿泥按粒度分选,彻底解决了供矿系统粘堵严重的问题,稳定了磨选系统给矿量。 相似文献
6.
7.
Alexandra Kodadová Zuzana Vitková Petra Herdová Anton Ťažký Jarmila Oremusová Daniel Grančai 《Drug development and industrial pharmacy》2015,41(7):1080-1088
This study deals with the formulation of natural drugs into hydrogels. For the first time, compounds from the sage essential oil were formulated into chitosan hydrogels. A sample preparation procedure for hydrophobic volatile analytes present in a hydrophilic water matrix along with an analytical method based on the gas chromatography coupled with the mass spectrometry (GC-MS) was developed and applied for the evaluation of the identity and quantity of essential oil components in the hydrogels and saline samples. The experimental results revealed that the chitosan hydrogels are suitable for the formulation of sage essential oil. The monoterpene release can be effectively controlled by both chitosan and caffeine concentration in the hydrogels. Permeation experiment, based on a hydrogel with the optimized composition [3.5% (w/w) sage essential oil, 2.0% (w/w) caffeine, 2.5% (w/w) chitosan and 0.1% (w/w) Tween-80] in donor compartment, saline solution in acceptor compartment, and semi-permeable cellophane membrane, demonstrated the useful permeation selectivity. Here, (according to lipophilicity) an enhanced permeation of the bicyclic monoterpenes with antiflogistic and antiseptic properties (eucalyptol, camphor and borneol) and, at the same time, suppressed permeation of toxic thujone (not exceeding its permitted applicable concentration) was observed. These properties highlight the pharmaceutical importance of the developed chitosan hydrogel formulating sage essential oil in the dermal applications. 相似文献
8.
This paper presents an analytical solution to the non-uniform pressure on thick-walled cylinder. The formulation is based on the linear elasticity theory (plain strain) and stress function method. As an example, the proposed solution is used to model the stress distribution due to non-uniform steel reinforcement corrosion in concrete. The model is formulated considering different scenarios of corrosion pressure distribution. It is validated against the finite element model for different cases of non-uniform pressure distributions. The results show that the corrosion-induced cracks are likely to start just beyond the anodic zone. This is confirmed by the experimental tests on concrete cylinder exposed to non-uniform accelerated corrosion of steel reinforcement. The model can be effectively used to calculate the distribution of corrosion-induced stresses in concrete. 相似文献
9.
10.
黄浦江为感潮河流,低潮位重现期的确定对黄浦江航道的设计具有重要意义。为了准确估计黄浦江低潮位的重现期,以黄浦江下游吴淞口站年最低潮位序列为例,在对样本进行三性审查的基础上,分别采用传统的数理统计方法和时变矩方法进行水文频率分析。结果表明:吴淞口站年最低潮位序列在1996年发生了变异;还现修正后的序列服从位置参数线性时变的GEV模型,低潮位存在缓慢的上升趋势;一致性条件下百年一遇低潮位约为0.261 m,在非一致性条件下其重现期增大为150 a。非一致性条件下的重现期增大说明黄浦江现有的航道设计标准偏安全,航道通航保证率提高。 相似文献