全文获取类型
收费全文 | 427篇 |
免费 | 15篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 136篇 |
金属工艺 | 3篇 |
机械仪表 | 4篇 |
建筑科学 | 10篇 |
矿业工程 | 1篇 |
能源动力 | 5篇 |
轻工业 | 88篇 |
水利工程 | 2篇 |
无线电 | 20篇 |
一般工业技术 | 59篇 |
冶金工业 | 74篇 |
原子能技术 | 1篇 |
自动化技术 | 38篇 |
出版年
2023年 | 2篇 |
2022年 | 14篇 |
2021年 | 14篇 |
2020年 | 10篇 |
2019年 | 6篇 |
2018年 | 13篇 |
2017年 | 9篇 |
2016年 | 11篇 |
2015年 | 4篇 |
2014年 | 14篇 |
2013年 | 24篇 |
2012年 | 13篇 |
2011年 | 31篇 |
2010年 | 26篇 |
2009年 | 17篇 |
2008年 | 18篇 |
2007年 | 22篇 |
2006年 | 13篇 |
2005年 | 9篇 |
2004年 | 16篇 |
2003年 | 13篇 |
2002年 | 12篇 |
2001年 | 6篇 |
2000年 | 7篇 |
1999年 | 3篇 |
1998年 | 3篇 |
1997年 | 5篇 |
1995年 | 2篇 |
1994年 | 10篇 |
1993年 | 8篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1976年 | 3篇 |
1973年 | 2篇 |
1966年 | 3篇 |
1961年 | 2篇 |
1955年 | 2篇 |
排序方式: 共有442条查询结果,搜索用时 46 毫秒
421.
Michalski G Meixner T Fenn M Hernandez L Sirulnik A Allen E Thiemens M 《Environmental science & technology》2004,38(7):2175-2181
The isotopic composition of nitrate collected from aerosols, fog, and precipitation was measured and found to have a large 17O anomaly with delta17O values ranging from 20 percent per thousand to 30% percent per thousand (delta17O = delta17O - 0.52(delta18O)). This 17O anomaly was used to trace atmospheric deposition of nitrate to a semiarid ecosystem in southern California. We demonstrate that the delta17O signal is a conserved tracer of atmospheric nitrate deposition and is a more robust indicator of N deposition relative to standard delta18O techniques. The data indicate that a substantial portion of nitrate found in the local soil, stream, and groundwater is of atmospheric origin and does not undergo biologic processing before being exported from the system. 相似文献
422.
423.
424.
425.
Edith Wendler-Kalsch 《Materialwissenschaft und Werkstofftechnik》1982,13(4):129-137
Corrosion Behaviour and Film Formation of Copper and Copper Alloys Film formation processes on Cu, CuZn, CuAl and CuNi materials in NH3- and Cl?-containing aqueous solutions are discussed in a summary article by way of corrosion systems, some typical and some of practical significance, and the protection offered by these films against general corrosion is described. Also considered are localized corrosion phenomena to which Cu-base alloys with oxide films are typically exposed. A comparison of the resistance of the various alloying systems illustrates the particular danger of stress corrosion cracking of mechanically stressed metals. Finally, the type and structure of oxide surface films are discussed with respect to their effect on crack initiation. 相似文献
426.
The author comments on a school of psychotherapy called Logotherapy or Existential Analysis, which was originated by Victor E. Frankl of the Department of Neurology and Psychiatry at the University of Vienna. This school of analysis reflects the culture of the Hitler era and post-war Europe. Frankl states that neurosis is caused by repression of the patient's sense of responsibility and the function of psychotherapy is to bring this sense of responsibility back to the patient's awareness. Happiness, he postulates, is a byproduct of the realization of other values. Fear of death, aging, and discomfort are the principal causes of anxiety. The author feels that this school of psychotherapy, which has arisen from an experiential background so different from ours is worthy of careful study. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
427.
Strang Harold R.; Lawrence Edith C.; Fowler Patrick C. 《Canadian Metallurgical Quarterly》1978,63(4):446
Examined the effects of knowledge of results (KR) and assigned goals on arithmetic computation. 100 female university students either received or did not receive explicit KR while under an easy or challenging goal assignment. 50 controls received neither KR nor goal assignment. Ss receiving KR under challenging goal assignments significantly increased their computational speed at no apparent cost in accuracy. These findings are congruent with the findings of M. Erez (1977). With the minimizing of implicit KR in the no-KR groups in the present study, challenging goal assignment in itself had no noticeable effect on computational speed and led to a significant increase in errors. It is suggested that feedback may be a necessary complement to assigned goals in facilitating performance. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
428.
Quick Determination of Monomeric Unoxidized Fatty Acids Refining and distillation fatty acids as well as raw or partly refined oils can contain beside monomeric fatty acids di and polymeric as well as oxidized fatty acids, too. Determination of the content of monomeric, unoxidized fatty acids is important for the use in feed. As quick method a gas chromatographic procedure is presented. Collaborative studies demonstrate a satisfactory repeatability of the results. The comparability is impaired by apparatus and operating parameters. The relative constance of deviation permits a compensation by comparative analysis and determination of correction factors. 相似文献
429.
This paper presents several Arcs-States models that can be applied to numerous vehicle routing problems, one of which is the well-known vehicle routing problem with capacities and time windows. In these models, the variables correspond to the states (i.e. the resource quantities) of the vehicles when they travel through an arc. The LP relaxation of the problem provides a lower bound that can be embedded in a branch and bound algorithm that solves the problem exactly. However, for the pseudo-polynomial number of variables and constraints of our models, column and row generations have to be used. Generally, in a branch and bound algorithm, the lower bound needs to be very efficient to minimize the size of the branch and bound trees as far as possible. One of the models we present, the time-only, relies on a relaxation of the Arcs-States model where a resource is removed from the states in the variables. Although the quality of the bounds decreases, the global resolution time is greatly improved, as illustrated on instances of Solomon's benchmark. 相似文献
430.
Marco Antonio López-Mata Marisol Gastelum-Cabrera Edith Valbuena-Gregorio Paul Baruk Zamudio-Flores Silvia Elena Burruel-Ibarra Gloria Guadalupe Morales-Figueroa Luis Quihui-Cota Josué Elías Juárez-Onofre 《Iranian Polymer Journal》2018,27(8):545-553
Nowadays, an increased interest on the development of novel biomaterials for different applications has been observed. The biopolymers such as proteins, lipids, polysaccharides or their combinations have been used for the manufacturing of novel membranes. The pectin is a polysaccharide that previously has been used only or combined with polymeric matrices, but the formulation of PEC/AG has not been evaluated yet. The aim of this work was to evaluate the physicochemical properties of a novel PEC/AG membrane. A mixture of pectin citric (PEC)/Aloe gel (AG) was prepared to manufacture membranes at 100/0 (control), 90/10, 80/20, 70/30, 60/40 and 50/50 proportions (% v/v) by casting method. Water vapor permeability (WVP), solubility, ATR-FTIR spectroscopy, microstructure, mechanical and optical properties were assessed for the produced membranes. The PEC/AG membranes showed a yellowish color, low UV light transmission at 200 nm and no significant changes in the opacity values. In addition, the microstructure by scanning electron microscopy (SEM) showed changes on the surface appeared as differently sized structures. An analysis of the total area of the 3284 cm?1 showed rearrangement of hydrogen bonds of the polysaccharide macromolecules, suggesting an enhanced interaction between the PEC and AG chains. In addition, all the membranes of PEC/AG showed high solubility (100%), low WVP and better toughness, extensibility and plasticity as compared with the control. The assessed physicochemical properties of the produced membranes suggested that they may be used as biomaterial for multiple applications in the medical, pharmaceutical, cosmetic or food industries. 相似文献