全文获取类型
收费全文 | 329601篇 |
免费 | 4215篇 |
国内免费 | 739篇 |
专业分类
电工技术 | 6404篇 |
综合类 | 578篇 |
化学工业 | 50818篇 |
金属工艺 | 10798篇 |
机械仪表 | 9188篇 |
建筑科学 | 8801篇 |
矿业工程 | 943篇 |
能源动力 | 9074篇 |
轻工业 | 32354篇 |
水利工程 | 2764篇 |
石油天然气 | 3866篇 |
武器工业 | 8篇 |
无线电 | 40961篇 |
一般工业技术 | 61454篇 |
冶金工业 | 61259篇 |
原子能技术 | 5628篇 |
自动化技术 | 29657篇 |
出版年
2021年 | 2501篇 |
2019年 | 2389篇 |
2018年 | 3883篇 |
2017年 | 3723篇 |
2016年 | 3891篇 |
2015年 | 2801篇 |
2014年 | 4861篇 |
2013年 | 15434篇 |
2012年 | 8040篇 |
2011年 | 10961篇 |
2010年 | 8597篇 |
2009年 | 9842篇 |
2008年 | 10439篇 |
2007年 | 10448篇 |
2006年 | 9222篇 |
2005年 | 8544篇 |
2004年 | 8372篇 |
2003年 | 8034篇 |
2002年 | 7870篇 |
2001年 | 7896篇 |
2000年 | 7562篇 |
1999年 | 7893篇 |
1998年 | 18217篇 |
1997年 | 13300篇 |
1996年 | 10508篇 |
1995年 | 8219篇 |
1994年 | 7504篇 |
1993年 | 7253篇 |
1992年 | 5588篇 |
1991年 | 5280篇 |
1990年 | 5179篇 |
1989年 | 5033篇 |
1988年 | 4938篇 |
1987年 | 4129篇 |
1986年 | 4281篇 |
1985年 | 4985篇 |
1984年 | 4557篇 |
1983年 | 4282篇 |
1982年 | 3815篇 |
1981年 | 4017篇 |
1980年 | 3681篇 |
1979年 | 3650篇 |
1978年 | 3445篇 |
1977年 | 4048篇 |
1976年 | 5066篇 |
1975年 | 2962篇 |
1974年 | 2807篇 |
1973年 | 2847篇 |
1972年 | 2322篇 |
1971年 | 2048篇 |
排序方式: 共有10000条查询结果,搜索用时 13 毫秒
901.
902.
Studied the differences in moral orientation in terms of gender specific modes of reasoning, in 2 experiments. In Exp 1, 32 Ss (aged 24–55 yrs) were read the "Heinz dilemma," and asked 3 questions regarding it. Deliberative and justificatory strategies were identified on the basis of the presence or absence of the higher level knowledge structures. In Exp 2, 40 undergraduates were presented with "Michael and Kohlberg Heinz dilemma," followed by a set of relevant questions. Male Ss preferred to apply a norm or rule in their solutions, while females rejected the application of a norm and sought alternative solutions. This was replicated in Exp 2, but the pattern was reversed with female Ss preferring to apply a norm. Males were divided in their use of either strategy indicating that although, genders differed in their judgments as to which norms or rules to apply; once adopted, norms and rules were used in similar ways. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
903.
Y Stern M Aronson T Shpitzer O Nativ O Medalia K Segal R Feinmesser 《Canadian Metallurgical Quarterly》1995,121(9):1003-1005
OBJECTIVE: To assess the role of DNA ploidy as a predictor of radioresistance in T1 glottic carcinoma. DESIGN: Case-control study. Flow cytometric DNA ploidy measurements were performed on formalin-fixed paraffin-embedded tumor specimens from 15 patients with T1 glottic laryngeal carcinomas in whom radiotherapy had failed and from a matched group of 15 patients in whom an identical radiotherapy regimen was curative. Analysis of DNA content was performed blind to outcome of treatment. SETTING: Academic tertiary referral medical center. PARTICIPANTS: Thirty patients with clinically staged T1, N0, M0 glottic carcinoma. INTERVENTION: All patients received radiation to the larynx through opposed lateral ports at a total dose of 64 to 70 Gy. RESULTS: Ten diploid and five aneuploid histograms were found in the resistant group, and six diploid and nine aneuploid histograms were found in the radiosensitive group. This difference was not statistically significant. A trend toward a higher relapse rate after radiotherapy (62.5%) among patients with diploid tumor compared with those with aneuploid tumor (35.7%) was noted. CONCLUSIONS: DNA ploidy did not predict response to radiotherapy in patients with T1 glottic cancer, probably because of the small number of patients. A trend toward lower risk of local recurrence after radiotherapy in aneuploid tumors was noted. A larger prospective study is needed to assess the value of DNA ploidy in the treatment of early laryngeal cancer. 相似文献
904.
W. Chen S. -H. Wang R. Chu F. King T. R. Jack R. R. Fessler 《Metallurgical and Materials Transactions A》2003,34(11):2601-2608
A study was carried out to understand the effect of precyclic loading on stress-corrosion-crack initiation in an X-65 pipeline
steel exposed to a near-neutral-pH soil environment. The test specimens were precyclically loaded before corrosion exposure
to represent a service history of up to about 20 years, depending on the severity of pressure fluctuation. Microcracks had
initiated on the polished surface of the X-65 pipeline steel after long-time exposure at open-circuit potential (OCP) in a
near-neutral-pH synthetic soil solution. These microcracks were mostly initiated from pits at metallurgical discontinuities
such as grain boundaries, pearlitic colonies, and banded phases in the steel. Strong preferential dissolution was observed
along planes of the banded structures in the steel. The selective corrosion attack at these metallurgical discontinuities
is attributed to the galvanic nature of those areas to their neighbors. Cyclic loading prior to corrosion exposure had significant
effects on microcrack initiation and propagation during subsequent corrosion exposure. Cyclic loading prior to corrosion exposure
either reduced or increased the probability of crack initiation and the rate of crack propagation, depending upon the magnitude
of the stress cycles. The largest reduction was seen at a peak cyclic stress of about 0.8 of the yield strength. This cyclic-loading-dependent
cracking behavior might be related to the alteration of the substructures and the residual stress in the steel as a result
of precyclic loading. 相似文献
905.
906.
907.
S. R. Syrtsov V. N. Shut D. A. Il'yushchenko E. L. Gavrilenko 《Journal of Engineering Physics and Thermophysics》2002,75(5):1229-1233
The influence of the parameters of posistor elements and the conditions of their heat exchange on the electrical and dynamic characteristics of a posistor block have been investigated. Good agreement between calculation results and experimental data has been established. 相似文献
908.
909.
The thermal expansion of a titanium modified, swelling resistant austenitic stainless steel designated as D9 is studied by measuring the lattice parameter as a function of temperature in the range 300-1300 K by high-temperature X-ray diffraction technique. The thermal expansion data thus obtained is in reasonable agreement with the typical thermal expansion values reported for similar nuclear grade austenitic stainless steels. However, at temperatures exceeding 900 K, the measured thermal expansivity exhibits a pronounced non-linear increase due partly to the precipitation of complex carbide and intermetallic phases. The high-temperature thermal expansion data obtained in the present study are augmented by modelling the low-temperature thermal expansion behaviour by Grüneisen formalism. 相似文献
910.
Bedload Transport in Alluvial Channels 总被引:1,自引:0,他引:1
Miguel Bravo-Espinosa W. R. Osterkamp Vicente L. Lopes 《Canadian Metallurgical Quarterly》2003,129(10):783-795
Hydraulic, sediment, land-use, and rock-erosivity data of 22 alluvial streams were used to evaluate conditions of bedload transport and the performance of selected bedload-transport equations. Transport categories of transport-limited (TL), partially transport-limited (PTL), and supply-limited (SL) were identified by a semiquantitative approach that considers hydraulic constraints on sediment movement and the processes that control sediment availability at the basin scale. Equations by Parker et al. in 1982, Schoklitsch in 1962, and Meyer-Peter and Muller in 1948 adequately predicted sediment transport in channels with TL condition, whereas the equations of Bagnold in 1980, and Schoklitsch, in 1962, performed well for PTL and SL conditions. Overall, the equation of Schoklitsch predicted well the measured bedload data for eight of 22 streams, and the Bagnold equation predicted the measured data in seven streams. 相似文献