全文获取类型
收费全文 | 36539篇 |
免费 | 1371篇 |
国内免费 | 63篇 |
专业分类
电工技术 | 377篇 |
综合类 | 29篇 |
化学工业 | 7285篇 |
金属工艺 | 729篇 |
机械仪表 | 744篇 |
建筑科学 | 1968篇 |
矿业工程 | 114篇 |
能源动力 | 1061篇 |
轻工业 | 2911篇 |
水利工程 | 432篇 |
石油天然气 | 120篇 |
武器工业 | 5篇 |
无线电 | 2495篇 |
一般工业技术 | 6170篇 |
冶金工业 | 6667篇 |
原子能技术 | 270篇 |
自动化技术 | 6596篇 |
出版年
2023年 | 217篇 |
2022年 | 445篇 |
2021年 | 684篇 |
2020年 | 466篇 |
2019年 | 623篇 |
2018年 | 786篇 |
2017年 | 700篇 |
2016年 | 837篇 |
2015年 | 761篇 |
2014年 | 1046篇 |
2013年 | 2387篇 |
2012年 | 1689篇 |
2011年 | 2100篇 |
2010年 | 1663篇 |
2009年 | 1556篇 |
2008年 | 1813篇 |
2007年 | 1784篇 |
2006年 | 1606篇 |
2005年 | 1446篇 |
2004年 | 1184篇 |
2003年 | 1130篇 |
2002年 | 1058篇 |
2001年 | 710篇 |
2000年 | 557篇 |
1999年 | 601篇 |
1998年 | 608篇 |
1997年 | 586篇 |
1996年 | 560篇 |
1995年 | 580篇 |
1994年 | 527篇 |
1993年 | 512篇 |
1992年 | 502篇 |
1991年 | 289篇 |
1990年 | 420篇 |
1989年 | 391篇 |
1988年 | 320篇 |
1987年 | 357篇 |
1986年 | 313篇 |
1985年 | 420篇 |
1984年 | 420篇 |
1983年 | 319篇 |
1982年 | 295篇 |
1981年 | 284篇 |
1980年 | 270篇 |
1979年 | 270篇 |
1978年 | 248篇 |
1977年 | 228篇 |
1976年 | 207篇 |
1975年 | 194篇 |
1974年 | 173篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
A.S. Fomichev I. David S.M. Lukyanov Yu.E. Penionzhkevich N.K. Skobelev O.B. Tarasov 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1994,350(3):605-607
The mass and charge identification of secondary particles with Z < 4 by a large CsI(T1) scintillation detector is performed using pulse shape analysis and time-of-flight methods. The dependence of the light output on E, A and Z is studied in the energy range of 1–20 MeV/A and special attention is paid to the integration time of the photomultiplier anode signal. It is found that the behaviour of the calibration curves strongly depends on the choice of the integration time interval. 相似文献
32.
33.
14 medicated hypertensive, 15 nonmedicated mild hypertensive, 39 normotensive, and 13 hypotensive adults participated in a 1–2 hr laboratory experiment that assessed each S's symptoms, moods, and estimates of systolic blood pressure (SBP) relative to actual SBP levels. Several self-reports and autonomic measures were collected during and after each of 22 tasks. Within-S correlations indicated that all Ss could estimate SBP at levels greater than chance. Further, 68% of the Ss evidenced at least 1 significant symptom–SBP correlation. Although medicated hypertensives believed they could estimate their BP more accurately than other groups, they were actually no more accurate than the other Ss. They also evidenced far fewer empirically derived symptom–SBP and emotion–SBP correlations than any other group. Overall, blood pressure (BP) beliefs were largely inaccurate. If these erroneous beliefs can be eliminated, Ss may be able to estimate BP fluctuations more accurately. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
34.
Lewis Gloria J.; Greenburg Sharon L.; Hatch David B. 《Canadian Metallurgical Quarterly》1988,19(1):81
We report the results of the first national survey of psychologists in private practice regarding their participation in peer consultation groups. The sample (71% return) was drawn from 800 randomly selected psychologists listed in the National Register of Health Service Providers in Psychology. We found that 23% of the sample currently belonged to peer consultation groups, and 24% had belonged in the past. Of those not currently in groups, 61% expressed the desire to belong if one were available. There were virtually no significant demographic differences between current members and nonmembers. We examined the following group characteristics: formation, length of existence, size, membership, leadership, theoretical orientation, range of experience, time and place, content, and group process. Groups tended to be small, informal, and leaderless; however, we found great variation among groups on all dimensions. Findings also showed a high degree of satisfaction with membership. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
35.
36.
Control law design for rotorcraft fly-by-wire systems normally attempts to decouple the angular responses using fixed-gain crossfeeds. This approach can lead to poor decoupling over the frequency range of pilot inputs and increase the load on the feedback loops. In order to improve the decoupling performance, dynamic crossfeeds should be adopted. Moreover, because of the large changes that occur in the aircraft dynamics due to small changes about the nominal design condition, especially for near-hovering flight, the crossfeed design must be ‘robust’. A new low-order matching method is presented here to design robust crossfeed compensators for multi-input, multi-output (MIMO) systems. The technique minimizes cross-coupling given an anticipated set of parameter variations for the range of flight conditions of concern. Results are presented in this paper of an analysis of the pitch/roll coupling of the UH-60 Black Hawk helicopter in near-hovering flight. A robust crossfeed is designed that shows significant improvement in decoupling perfomance and robustness over the fixed-gain or single point dynamic compensators. The design method and results are presented in an easily used graphical format that lends significant physical insight to the design procedure. This plant precompensation technique is an appropriate preliminary step to the design of robust feedback control laws for rotorcraft. 相似文献
37.
38.
39.
Reviews the book, Elements of episodic memory by Endel Tulving (1983). Those of us who have followed Tulving's investigations in the somewhat fragmented form of journal articles are very grateful to have his ideas encapsulated, elaborated, and elegantly expounded in his Elements of episodic memory. Tulving spends the initial third of the book driving home the evidence that the distinction between episodic and semantic memory is not just that episodic is time-lagged and semantic is not: it is more far-ranging, and his new work on amnesia is leading to the conclusion that for some forms of this disorder either type of memory may be attacked but not necessarily both. The first vista that opens from Tulving's vantage point is that "systems" and "schemata" are collections of connections that derive a certain autonomy from being only loosely connected to other collections. The second vista that emerges is a psychology in which the use of numbers is rich and strange. A third vista that opens up is shielded at first by a spectre of opposition. The spectre seizes on the passage on "free radicals," in which Tulving claims that certain thoughts cannot be unambiguously assigned to either episodic or semantic memory. Perhaps the most heartening aspect of this book is that Tulving could never have written this monograph without the foundations of his experiments. It is a great relief to see experimentation validated in so invigorating a form. Nevertheless, the most difficult chapters of the book, on recognition and recall, are built on experimental findings that are not yet properly understood. I am glad Tulving did not delay in writing this book until he felt more secure about the questions raised in these last chapters: the work thereby remains a challenge rather than a fait accompli. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
40.
David Hui 《International Journal of Mechanical Sciences》1985,27(6):397-408
This paper deals with the effects of initial geometric imperfections and in-plane boundary conditions on the large-amplitude vibration behavior of angle- and cross-ply rectangular thin plates. It is found that the presence of imperfection amplitudes of the order of only half the total laminated-plate thickness may significantly raise the vibration frequencies and change the large-amplitude vibration behavior from the well-known hard-spring to soft-spring behavior. The effects of fibre angles and bending-stretching coupling for angle-ply plates and Young's moduli ratios and number of layers for antisymmetric cross-ply plates are examined. 相似文献