全文获取类型
收费全文 | 11740篇 |
免费 | 394篇 |
国内免费 | 201篇 |
专业分类
电工技术 | 278篇 |
综合类 | 248篇 |
化学工业 | 1297篇 |
金属工艺 | 307篇 |
机械仪表 | 472篇 |
建筑科学 | 452篇 |
矿业工程 | 137篇 |
能源动力 | 186篇 |
轻工业 | 1140篇 |
水利工程 | 293篇 |
石油天然气 | 113篇 |
武器工业 | 74篇 |
无线电 | 1103篇 |
一般工业技术 | 1238篇 |
冶金工业 | 3744篇 |
原子能技术 | 163篇 |
自动化技术 | 1090篇 |
出版年
2022年 | 124篇 |
2021年 | 183篇 |
2020年 | 133篇 |
2019年 | 124篇 |
2018年 | 128篇 |
2017年 | 148篇 |
2016年 | 139篇 |
2015年 | 186篇 |
2014年 | 286篇 |
2013年 | 522篇 |
2012年 | 405篇 |
2011年 | 483篇 |
2010年 | 407篇 |
2009年 | 445篇 |
2008年 | 452篇 |
2007年 | 451篇 |
2006年 | 394篇 |
2005年 | 350篇 |
2004年 | 271篇 |
2003年 | 277篇 |
2002年 | 277篇 |
2001年 | 224篇 |
2000年 | 198篇 |
1999年 | 242篇 |
1998年 | 884篇 |
1997年 | 568篇 |
1996年 | 484篇 |
1995年 | 323篇 |
1994年 | 271篇 |
1993年 | 284篇 |
1992年 | 117篇 |
1991年 | 133篇 |
1990年 | 140篇 |
1989年 | 140篇 |
1988年 | 139篇 |
1987年 | 140篇 |
1986年 | 117篇 |
1985年 | 130篇 |
1984年 | 96篇 |
1983年 | 104篇 |
1982年 | 72篇 |
1981年 | 93篇 |
1980年 | 74篇 |
1979年 | 81篇 |
1978年 | 72篇 |
1977年 | 126篇 |
1976年 | 232篇 |
1975年 | 73篇 |
1974年 | 71篇 |
1973年 | 63篇 |
排序方式: 共有10000条查询结果,搜索用时 629 毫秒
51.
David N. Johnson Alan A. Johnson 《Fatigue & Fracture of Engineering Materials & Structures》1985,8(3):287-294
The results of Stan ton and Bairstow (1908) have been reanalyzed to yield information on the composition dependence of the low cycle impact fatigue properties of pearlitic plain carbon steels. It has been found that the energy absorbed per impact, Ei, and the number of impacts are failure, Nf, are related by the equation: In this equation q is determined by the carbon, manganese and silicon contents of the steel; Eo is the impact endurance limit; and C and D are constants. The curve represented by this equation intersects that representing the Johnson-Keller high cycle impact fatigue equation at a value of logeNf equal to 1/C. Thus, the transition from low to high cycle impact fatigue occurs at this value of logeNf. 相似文献
52.
Sally Cole Johnson 《集成电路应用》2007,(5):41-42
纽约州立大学Buffalo分校电子封装实验室正在为美国海军开发新型的功率电子封装,在一些极端苛刻的工作条件下(比如在军舰和战机上).它们能够解决大电流密度、高温和大的温度梯度所引起的种种问题。这类功率电子封装还有可能很快进入民用产品。 相似文献
53.
Cunningham William A.; Johnson Marcia K.; Gatenby J. Chris; Gore John C.; Banaji Mahzarin R. 《Canadian Metallurgical Quarterly》2003,85(4):639
Evaluative responses appear to involve 2 seemingly distinct sets of processes: those that are automatically activated and others that are more consciously controlled. Using functional magnetic resonance imaging, the authors investigated the brain systems associated with automatic and controlled evaluative processing. Participants made either evaluative (good-bad) or nonevaluative (past-present) judgments about famous names. Greater amygdala activity was observed for names rated as "bad" relative to those rated as "good," regardless of whether the task directly involved an evaluative judgment (good-bad) or not (past-present). Good-bad judgments resulted in greater medial and ventrolateral prefrontal cortex (PFC) activity than past-present judgments. Furthermore, there was greater ventrolateral PFC activity in good-bad judgments marked by greater ambivalence. Together, these findings indicate a neural distinction between processes engaged for automatic and controlled evaluation. Whereas automatic processes are sensitive to simple valence, controlled processes are sensitive to attitudinal complexity. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
54.
55.
G Hendrickson R K Anderson P D Clayton J Cimino G M Hripcsak S B Johnson M McCormack S Sengupta S Shea R Sideli 《M.D. computing : computers in medical practice》1992,9(1):35-42
Over the past seven years, Columbia-Presbyterian Medical Center has been planning and implementing an integrated academic information management system. Accomplishments to date include establishing an institutional information architecture, installing a campus-wide network of workstations, recruiting the staff needed to develop and implement the system, and developing various applications. This paper presents the rationale and steps involved in these accomplishments, as well as data on use of the system so far. 相似文献
56.
57.
58.
OBJECTIVE: To study the effects of thevetoside (TS), a cardiac glycoside, and an inhibitor of Na+, K(+)-ATPase, on tumor cells cultured in vitro. METHODS: The cytotoxic effects of TS on tumor cells were determined by trypan blue dye exclusion, neutral red vital staining and clonogenic assay. The time-effect relationship and growth inhibition of tumor cells by TS were assayed with trypan blue exclusion method. RESULTS: TS at low doses (0.005-0.1 mg.L-1), with dose dependence, was able to kill SMMC-7721, SGC-7901 and HeLa cells. IC50 values for SMMC-7721, SGC-7901 and HeLa cells were 0.007, 0.011 and 0.018 mg.L-1 by trypan blue dye exclusion test and 0.016, 0.055 and 0.078 mg.L-1 by neutral red vital staining test. TS inhibited the clonal forming rate of SMMC-7721 and SGC-7901 significantly with IC50 values of 0.021 and 0.036 mg.L-1, respectively. Only when the cells were continuously treated with TS for more than 8 hours, the drug-induced cell lethality could be displayed and strengthened quickly. The growth of tumor cells was notably inhibited after they were exposed to 0.1 microgram/ml of TS for 12 hours. All the experimental results of antitumor activity in vitro showed that SMMC-7721 was most sensitive to TS among the three kinds of tumor cells. CONCLUSIONS: TS has cytotoxic action on tumor cells cultured in vitro and this lethal effect must have an action process, in which tumor cells are not dead but suffer from deadly injury and lost the capability of unlimited proliferation. 相似文献
59.
J Randerson L Cawkwell A Jack JA Child F Lewis N Hall P Johnson P Evans S Barrans GJ Morgan 《Canadian Metallurgical Quarterly》1996,93(1):160-162
Fluorescent polymerase chain reaction (PCR) was used to assay 12 microsatellite markers (APC x 2, DCC, P53 x 2, RB1, NM23, WT1, D6S260, D6S262, D6S281 and TNFa) to look for evidence of microsatellite instability in 40 cases of follicle centre cell lymphoma (FCC). Evidence of novel alleles seen in the tumour tissue but not the normal uninvolved tissue was seen in seven cases (17%). In only two of these cases (5%) was more than one locus involved but in these cases multiple affected loci were seen (4/12 and 7/12 respectively). The detection of microsatellite instability indicates a DNA repair defect such as that which would be predicted to occur in cells with mutated mismatch repair genes, a novel finding in FCC lymphoma. 相似文献
60.