全文获取类型
收费全文 | 17214篇 |
免费 | 308篇 |
国内免费 | 24篇 |
专业分类
电工技术 | 206篇 |
综合类 | 5篇 |
化学工业 | 2349篇 |
金属工艺 | 395篇 |
机械仪表 | 377篇 |
建筑科学 | 685篇 |
矿业工程 | 64篇 |
能源动力 | 354篇 |
轻工业 | 1403篇 |
水利工程 | 127篇 |
石油天然气 | 126篇 |
武器工业 | 1篇 |
无线电 | 1640篇 |
一般工业技术 | 2737篇 |
冶金工业 | 5143篇 |
原子能技术 | 185篇 |
自动化技术 | 1749篇 |
出版年
2022年 | 90篇 |
2021年 | 140篇 |
2020年 | 97篇 |
2019年 | 139篇 |
2018年 | 168篇 |
2017年 | 144篇 |
2016年 | 146篇 |
2015年 | 153篇 |
2014年 | 289篇 |
2013年 | 721篇 |
2012年 | 418篇 |
2011年 | 536篇 |
2010年 | 441篇 |
2009年 | 438篇 |
2008年 | 585篇 |
2007年 | 546篇 |
2006年 | 519篇 |
2005年 | 467篇 |
2004年 | 382篇 |
2003年 | 423篇 |
2002年 | 367篇 |
2001年 | 352篇 |
2000年 | 350篇 |
1999年 | 419篇 |
1998年 | 1369篇 |
1997年 | 878篇 |
1996年 | 629篇 |
1995年 | 454篇 |
1994年 | 411篇 |
1993年 | 418篇 |
1992年 | 289篇 |
1991年 | 253篇 |
1990年 | 272篇 |
1989年 | 233篇 |
1988年 | 242篇 |
1987年 | 214篇 |
1986年 | 210篇 |
1985年 | 268篇 |
1984年 | 239篇 |
1983年 | 223篇 |
1982年 | 222篇 |
1981年 | 192篇 |
1980年 | 208篇 |
1979年 | 139篇 |
1978年 | 152篇 |
1977年 | 248篇 |
1976年 | 335篇 |
1975年 | 150篇 |
1974年 | 142篇 |
1973年 | 115篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Intense irradiation (25–40 A/cm2) at intermediate energy (400 keV) has been found to cause “metallisation” of tungsten oxide and titanium niobate crystal surfaces. The possible mechanisms and the likely consequences for high-resolution imaging of clean oxide surfaces are briefly discussed. 相似文献
32.
In the letter, two schemes of circuit partitioning for pseudo-exhaustive testing are described. The complexities of both are proved to be NP-complete. 相似文献
33.
The short contact time dissolution of vitrinite and inertinite concentrates of an Australian bituminous coal was studied under isothermal conditions with tetralin as solvent. The reactivity of the two maceral types and the yields and nature of the products were determined for a range of reaction temperatures (400, 420 and 440 °C) and reaction times (2–20 min). The dissolution of vitrinite proceeded at a significantly greater rate than for inertinite and was associated with greater selectivity to soluble non-gaseous products. At very short reaction times (2 min), the vitrinite underwent solubilizing reactions to yield products of higher molecular weight and greater oxygen functionality than was the case for inertinite, for which changes in the chemical nature of the products were negligible over the range of conditions studied. At longer reaction times (5 min), the composition of the vitrinite-derived products was similar to that of the inertinite-derived products. 相似文献
34.
Presents an obituary for Nicholas Hobbs. Just at the end of his stellar career of public service through psychology, Nick Hobbs received very appropriate honors showing that psychologists and many others knew what a precious national resource his life had been. Only days before his death from cancer on January 23, 1983, he participated in the dedication of the Nicholas Hobbs Laboratory of Human Development of the Peabody College for Teachers of Vanderbilt University, part of the Kennedy Center for Research on Education and Human Development that he founded and directed at its beginning. Two years earlier, he had received two parallel American Psychological Association (APA) awards--one for Distinguished Contributions to Psychology in the Public Interest and another for Distinguished Professional Contributions "utilizing psychological knowledge in the public interest and social policy." As the citations and testimonials on these occasions variously noted, Nick gave creative, responsible, and effective service to the institutions that he helped administer, to the Southern region from which he sprang, to the APA, and to the profession of psychology, but above all to the nation's children and youth, especially those who grew up with disadvantage and difficulty. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
35.
L. Nicolas M. Durin V. Koundy Eric Mathet A. Bucalossi P. Eisert J. Sievers L. Humphries J. Smith V. Pistora K. Ikonen 《Nuclear Engineering and Design》2003,223(3):263-277
The subject of this paper is to compare the results of the different calculations performed by the benchmark participants in the framework of the OECD Lower Head Failure (OLHF) program. The benchmark consists in the finite element (FE) calculation or in analytical calculations of the mechanical behavior of the OLHF-1 experiment. Seven participants from six countries and seven companies or organizations (AVN, VTT, GRS, UJV, SNL, IPSN and CEA) have performed the benchmark.The OLHF experiment program extends the NRC-sponsored SNL LHF program (NUREG/CR-5582) completed in 1998: these experiments where intended to simulate the thermal/mechanical loads to a 1/4.85-scale model of a reactor pressure vessel. The pressure vessel material (SA533B1 steel) used in these experiments is prototypic of reactor PWR vessel material and has been well characterized by material property testing as part of this program. The OLHF tests advance the results of the previous testing program by examining the effects of large temperature differences across the vessel wall. Large temperature differences in excess of 150–400 K are more prototypic of accident conditions.Most of the participants performed 2-D axisymmetric analyses and doesn’t study the crack opening. The global mechanical behaviour of OLHF-1 experiment is well represented but prediction of the maximum vertical displacement is not in good agreement with the experimental value. Failure time and location are in quite good agreement with experimental results but large discrepancies are observed on the mode of failure: creep or plasticity. To improve predictions, more investigation and work is needed on the choice of the failure criteria and failure mode. 相似文献
36.
37.
Butler Emily A.; Egloff Boris; Wlhelm Frank H.; Smith Nancy C.; Erickson Elizabeth A.; Gross James J. 《Canadian Metallurgical Quarterly》2003,3(1):48
At times, people keep their emotions from showing during social interactions. The authors' analysis suggests that such expressive suppression should disrupt communication and increase stress levels. To test this hypothesis, the authors conducted 2 studies in which unacquainted pairs of women discussed an upsetting topic. In Study 1, one member of each pair was randomly assigned to (a) suppress her emotional behavior, (b) respond naturally, or (c) cognitively reappraise in a way that reduced emotional responding. Suppression alone disrupted communication and magnified blood pressure responses in the suppressors' partners. In Study 2, suppression had a negative impact on the regulators' emotional experience and increased blood pressure in both regulators and their partners. Suppression also reduced rapport and inhibited relationship formation. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
38.
Penedo Frank J.; Dahn Jason R.; Gonzalez Jeffrey S.; Molton Ivan; Carver Charles S.; Antoni Michael H.; Roos Bernard A.; Schneiderman Neil 《Canadian Metallurgical Quarterly》2003,22(2):220
This study evaluated relations among optimism, perceived stress management skills (PSMS), and positive mood in 46 men who had surgical treatment for localized prostate cancer. The authors found that optimism, PSMS, and positive mood scores were positively correlated. Positive mood was unrelated to demographic and disease-related control variables. In a hierarchical regression model controlling for PSMS, the relationship between optimism and positive mood became nonsignificant, whereas PSMS remained a correlate of positive mood. Results suggest that the relationship between optimism and positive mood may be mediated by belief in being able to use stress management techniques effectively. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
39.
Fe–Co bimetallic metals supported on CaCO3 support have been prepared using three different methods for the preparation of the catalysts; wet impregnation (IMP), deposition–precipitation (DP) and reverse micelle impregnation (RM). By careful choice and optimization of CVD reaction conditions and catalyst preparation procedures, we have tailored the nanofabrication of CNTs using 5 wt.% Fe–Co/CaCO3. High yields of ‘clean’ MWNTs with near 100% selectivity and excellent reproducibility were obtained (1215% and 835% yields for the IMP and DP methods respectively). The RM technique enabled more precise control over the size of the CNTs and a narrower diameter distribution (3–5 nm i.d. and 10–15 nm o.d.) was obtained. 相似文献
40.
D. P. Phillips, T. E. Ruth, and L. M. Wagner (1993) reported that 1969-1990 California mortality data show that Chinese Americans are particularly vulnerable to diseases that Chinese astrology and traditional Chinese medicine associate with their birth years. For example, because fire is associated with the heart, a Chinese person born in a fire year (such as 1937) is more likely to die of heart disease than is a Chinese person born in a nonfire year. However, many diseases were excluded from this study, some diseases that were included have ambiguous links to birth years, and the statistical tests were indirect. A more complete statistical analysis and independent California mortality data for the years 1960-1968 and 1991-2002 did not replicate the original results. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献