全文获取类型
收费全文 | 6226篇 |
免费 | 246篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 63篇 |
综合类 | 4篇 |
化学工业 | 1083篇 |
金属工艺 | 51篇 |
机械仪表 | 79篇 |
建筑科学 | 254篇 |
矿业工程 | 7篇 |
能源动力 | 129篇 |
轻工业 | 664篇 |
水利工程 | 55篇 |
石油天然气 | 28篇 |
无线电 | 364篇 |
一般工业技术 | 932篇 |
冶金工业 | 2099篇 |
原子能技术 | 52篇 |
自动化技术 | 610篇 |
出版年
2023年 | 32篇 |
2022年 | 78篇 |
2021年 | 112篇 |
2020年 | 72篇 |
2019年 | 82篇 |
2018年 | 117篇 |
2017年 | 118篇 |
2016年 | 124篇 |
2015年 | 123篇 |
2014年 | 152篇 |
2013年 | 327篇 |
2012年 | 256篇 |
2011年 | 409篇 |
2010年 | 316篇 |
2009年 | 285篇 |
2008年 | 343篇 |
2007年 | 328篇 |
2006年 | 280篇 |
2005年 | 237篇 |
2004年 | 186篇 |
2003年 | 176篇 |
2002年 | 168篇 |
2001年 | 111篇 |
2000年 | 105篇 |
1999年 | 127篇 |
1998年 | 303篇 |
1997年 | 198篇 |
1996年 | 151篇 |
1995年 | 117篇 |
1994年 | 98篇 |
1993年 | 82篇 |
1992年 | 46篇 |
1991年 | 49篇 |
1990年 | 57篇 |
1989年 | 53篇 |
1988年 | 53篇 |
1987年 | 51篇 |
1986年 | 51篇 |
1985年 | 58篇 |
1984年 | 31篇 |
1983年 | 35篇 |
1982年 | 27篇 |
1981年 | 41篇 |
1980年 | 37篇 |
1978年 | 20篇 |
1977年 | 35篇 |
1976年 | 31篇 |
1975年 | 21篇 |
1974年 | 25篇 |
1973年 | 25篇 |
排序方式: 共有6474条查询结果,搜索用时 15 毫秒
1.
Removal of gold from basic solutions containing [Au(CN)2]? has been demonstrated using the inherently conducting polymer polypyrrole. Polymers containing sulfonated aromatic dopants have been found to display a significant ability to remove gold from such solutions. Experiments performed in solutions containing both gold and copper cyanide complexes indicate that the recovery process is not highly selective. However, the polypyrroles used display significantly faster rates of gold recovery than activated carbon. © 2003 Society of Chemical Industry 相似文献
2.
A case of traumatic extracranial vertebral arterial dissection leading to vertebrobasilar thrombosis and respiratory compromise requiring mechanical ventilation was managed with intraarterial thrombolysis and stenting of the vertebral intimal dissection. In contrast to similar, previously reported cases, this critically ill patient made a full recovery, returning to his job as a secondary school teacher. 相似文献
3.
Jennifer Spenader 《Journal of Logic, Language and Information》2003,12(3):351-368
There are three ways to refer to a fact from the complement of afactive verb: (1) Via abstract object anaphoric reference, or, witha full sentential complement that will be interpreted either (2) asa bound presupposition or (3) as triggering a presupposition of afact that will have to be accommodated. Spoken corpus examplesreveal that these three possibilities differ in relation to thetype of information they tend to contribute, and this has twoeffects. First, the information status of the fact and its role inthe discourse seem to affect the preference for one constructionover another in a particular context. Second, presupposed factivecomplements that need to be accommodated tend to be hearer-new andthe focus of the utterance, meaning that information structureseems to contribute to the felicity of accommodation ofpresupposed facts. 相似文献
4.
Kahler Christopher W.; Read Jennifer P.; Wood Mark D.; Palfai Tibor P. 《Canadian Metallurgical Quarterly》2003,17(3):226
Structural equation modeling was used to test the mediational role of social environmental selection on alcohol use in cross-sectional samples of 447 students from a rural state university and 421 students from an urban private university. Results showed that male gender, White ethnicity, and sensation seeking were uniquely associated with greater alcohol use. Mediational analyses indicated that socioenvironmental factors (i.e., Greek involvement, friends' approval of drinking/getting drunk) were positively associated with alcohol use and significantly accounted for parts of the effects of ethnicity and sensation seeking, but not gender, on alcohol use. Results suggest that White students and those high on sensation seeking may drink more heavily in college, in part because they select social environments in which alcohol use is encouraged. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
5.
In this paper, we argue that successful integration of knowledge across work domains in the short-term can mask the generation of long-term consequences. We explore a setting, the introduction of environmental considerations into semiconductor manufacturing, where the eventual adoption of common measurement artifacts and associated practices enabled knowledge integration, but failed to address significant underlying consequences. Drawing from observational, interview, and archival data we develop an understanding of the work practices of the Tech and EnviroTech groups as structured by the material world and broader collective conventions. We introduce the concept of knowledge regime to outline the differences in knowledge across these work domains. More specifically, we find that differences in the causal specificity and developmental time horizon of knowledge and the measurement artifacts that result contribute to the relative power of one knowledge regime over another. Understanding these sources of incompatibility provides insight into the design requirements of information systems as boundary objects for knowledge integration, but also specifies the potential limits to any design effort. 相似文献
6.
JF Price 《Canadian Metallurgical Quarterly》1997,27(9):1004-1006
OBJECTIVE: To describe a rare case of right renal agenesia and left pelvic ectopy. To our knowledge, only 10 such cases have been reported in the world literature. METHODS: A 76-year-old male patient who consulted for irritative prostatic syndrome is described. Patient evaluation included IVP and CT. RESULTS: IVP revealed the absence of the right kidney in addition to an anomalous position of the left kidney. The foregoing findings were confirmed by CT. CONCLUSION: This uncommon congenital anomaly is essentially asymptomatic and is generally diagnosed in infants through its complications. In the case described herein, however, this anomaly had been incidentally detected during IVP and CT assessment of a 76-year-old patient who had consulted for irritative prostatic syndrome. 相似文献
7.
8.
Anton Apriyantono Jennifer M Ames 《Journal of the science of food and agriculture》1993,61(4):477-484
Aqueous molal solutions of xylose and lysine (initial pH 4–9) were refluxed either with control of the pH at 5–0 or without pH control (final pH 2–6). Analysis by gas chromatography (GC) and GC-mass spectrometry resulted in the identification of 58 and 28 compounds, respectively, from the two systems. Furans were the main reaction products in both systems and 2-furfural alone comprised 522 and 999 g kg?1 of the volatiles, respectively, from the systems with final pH values of 5–0 and 2–6. Maintaining the pH at 5–0 resulted in a higher yield and greater numbers of nitrogen-containing compounds, and monocyclic pyrroles, pyridines and 2,3-dihydro-l H-pyrrolizines were identified only in that system. Aliphatic compounds, alicyclic compounds, benzene derivatives. l-(2–furfuryl)pyrroles and pyrazines were also identified. This investigation is the first report of the formation of 2.3-dihydro-l H-pyrrolizines in a model system containing lysine as the amino compound; a possible mechanism is proposed. 相似文献
9.
The purpose of this study was to identify family physicians' firearm safety counseling beliefs and behaviors. A survey was mailed to a random sample of 600 members of the American Academy of Family Physicians. A three wave mailing technique was used to maximize the response rate and yielded 271 usable surveys (55% response rate). Outcome measures included training experience in firearm safety counseling, the prevalence of firearm safety counseling by family physicians, and their perceptions regarding such counseling. The majority (78%) of family physicians lacked formal training on how to counsel patients about firearm safety and 49% believed more time should be spent in residency programs on firearm safety counseling. The majority (84%) of respondents never or rarely counseled patients on firearm safety and 50% believed firearm safety counseling should be a low priority in their delivery of primary care. The majority of respondents did not regularly counsel patients about firearm safety, did not believe firearm safety counseling should be a priority, and did not believe firearm safety counseling would be effective in reducing firearm-related trauma. 相似文献
10.
AS Jonason S Kunala GJ Price RJ Restifo HM Spinelli JA Persing DJ Leffell RE Tarone DE Brash 《Canadian Metallurgical Quarterly》1996,93(24):14025-14029
The multiple genetic hit model of cancer predicts that normal individuals should have stable populations of cancer-prone, but noncancerous, mutant cells awaiting further genetic hits. We report that whole-mount preparations of human skin contain clonal patches of p53-mutated keratinocytes, arising from the dermal-epidermal junction and from hair follicles. These clones, 60-3000 cells in size, are present at frequencies exceeding 40 cells per cm2 and together involve as much as 4% of the epidermis. In sun-exposed skin, clones are both more frequent and larger than in sun-shielded skin. We conclude that, in addition to being a tumorigenic mutagen, sunlight acts as a tumor promoter by favoring the clonal expansion of p53-mutated cells. These combined actions of sunlight result in normal individuals carrying a substantial burden of keratinocytes predisposed to cancer. 相似文献