全文获取类型
收费全文 | 4914篇 |
免费 | 42篇 |
专业分类
电工技术 | 35篇 |
综合类 | 3篇 |
化学工业 | 406篇 |
金属工艺 | 82篇 |
机械仪表 | 72篇 |
建筑科学 | 89篇 |
矿业工程 | 10篇 |
能源动力 | 46篇 |
轻工业 | 229篇 |
水利工程 | 21篇 |
石油天然气 | 3篇 |
无线电 | 307篇 |
一般工业技术 | 319篇 |
冶金工业 | 3044篇 |
原子能技术 | 14篇 |
自动化技术 | 276篇 |
出版年
2021年 | 22篇 |
2018年 | 27篇 |
2017年 | 26篇 |
2016年 | 27篇 |
2015年 | 19篇 |
2014年 | 29篇 |
2013年 | 97篇 |
2012年 | 46篇 |
2011年 | 67篇 |
2010年 | 66篇 |
2009年 | 69篇 |
2008年 | 75篇 |
2007年 | 83篇 |
2006年 | 91篇 |
2005年 | 88篇 |
2004年 | 68篇 |
2003年 | 66篇 |
2002年 | 70篇 |
2001年 | 66篇 |
2000年 | 61篇 |
1999年 | 133篇 |
1998年 | 882篇 |
1997年 | 478篇 |
1996年 | 315篇 |
1995年 | 224篇 |
1994年 | 208篇 |
1993年 | 200篇 |
1992年 | 69篇 |
1991年 | 57篇 |
1990年 | 80篇 |
1989年 | 83篇 |
1988年 | 75篇 |
1987年 | 66篇 |
1986年 | 63篇 |
1985年 | 64篇 |
1984年 | 47篇 |
1983年 | 43篇 |
1982年 | 48篇 |
1981年 | 43篇 |
1980年 | 58篇 |
1979年 | 29篇 |
1978年 | 29篇 |
1977年 | 83篇 |
1976年 | 171篇 |
1975年 | 26篇 |
1974年 | 25篇 |
1973年 | 22篇 |
1972年 | 20篇 |
1971年 | 23篇 |
1968年 | 19篇 |
排序方式: 共有4956条查询结果,搜索用时 15 毫秒
51.
The Mono Mac 6 (MM6) human monocytic cell line was evaluated with the established J774 murine macrophage cell line to ascertain its effectiveness in determining the intracellular activities of antimycobacterial drugs. Cells were infected with Mycobacterium tuberculosis H37Ra and treated with drug concentrations corresponding to the MICs, as well as to threefold higher than and threefold less than the MICs. Changes in CFU were compared after 7 days to determine significant differences between treated and nontreated groups. The results suggest that MM6 will make a useful model for testing the intracellular activities of antituberculosis drugs. 相似文献
52.
J. Wright V. Adams J. Hykin P. Gowland B. Issa P. Boulby P. Tokarczuk D. Evans R. Spiller P. Mansfield 《Magma (New York, N.Y.)》1994,2(3):467-469
Echo-planar imaging (EPI) can be used to produce snapshot images of the human stomach and antro-pyloro-duodenal segment in real time as an alternative technique to intubation and exposure to ionizing radiation. The method has been further developed to monitor simultaneous gastric motility and gastric emptying of liquid and solid meals. The model has been utilized to study the effects of pharmacological agents on gastric function.Eight normal subjects were imaged in a 0.5-T superconducting magnet for up to 6 h following ingestion of 800 ml tap water, followed by 500 ml porridge test meal + 500 ml tap water. A rapid multislice technique was adopted to image adjacent transverse slices (10 mm thick) through the gastric region. In addition, three subjects were orally dosed with 20 mg of the prokinetic agent Cisapride. Gastric volumes for each slice were calculated and summed to produce a measure of total gastric volume and gastric emptying. Contractile activity at the level of the antro-pyloric segment was detected using sequential 128 ms images at 3 s intervals. Alternate measurements of gastric volume and motility were made for the duration of the study.Gastric emptyingT
1/2's (times to empty 50% of the gastric contents) of 12.9 min for water and 116 min for porridge were in agreement with results obtained by the traditional techniques of gamma scintigraphy and impedance imaging. The frequency of gastric contractions increased from 2.4 contractions per minute (cpm) to 3.2 cpm following water and from 2.9 to 3.2 cpm following porridge. The prokinetic effect of enhanced coordination of antroduodenal contractions was also observed. These studies have demonstrated that EPI can be used to detect and image gastroduodenal function in man, totally noninvasively, and can be used to study the effects of drugs acting on the gastrointestinal tract. 相似文献
53.
Low temperature heat capacity measurements have been made on hot isostatically pressed Nb3Sn and arc cast, homogenized, and A15 transformation annealed V-23.3 at. pct Ga and V-18.1 at. pct Ga. The heat capacity measurements
display the superconducting transition temperature (T
c), and have been used to evaluate the effects of plastic deformation on theT
c range. Plastic deformation to the extent of 15 pct compression at 1525 and 1650 °C does not alter the superconducting transition
in polycrystalline Nb3Sn. Plastic deformation to the extent of 15 pct compression at 1050 and 1200 °C does not alter the superconducting transition
in polycrystalline V-23.3Ga, transformed to A15 structure with a fifty-hour 1150 °C anneal. The same statement can be made
for A15 V-18.1Ga, deformed at 1050 °C after a fifty-hour, 1150 °C anneal. With onlyfive hours annealing at 1150 °C, A15 V-23.2Ga displays a lowering and broadening of theT
c range upon 1050 and 1200 °C plastic deformation. With onlyfive hours annealing at 1150 °C, A15 V-18.1Ga displays a broad, but increasedT
c range after plastic deformation at 1050 °C. 相似文献
54.
55.
56.
A discrete-time, model-based output feedback control structure for nonlinear processes is developed in the present work. The structure makes use of a closed-loop observer, while at the same time it guarantees that the overall feedback controller possesses integral action. An algebraic transformation is applied on the observer states to insure that the input/output gain of the observer matches the model upon which the static state feedback control law is based. The resulting control algorithm is a two-degree-of-freedom control law, in the sense that the output and the set point are processed in different ways. The control structure is shown not only to have the same properties as the standard model-state feedback structure, but also that it emerges from a model algorithmic control framework. Finally, a simulation example using an exothermic CSTR operating at an open-loop unstable steady state is used to evaluate the closed-loop performance of the proposed method. 相似文献
57.
58.
59.
Les Hatton Andy Wright Stuart Smith Gregg Parkes Paddy Bennett Robert Laws 《Software》1988,18(4):301-329
The portability of software has become a major commercial issue in recent times. Such portability does not come easily, as few if any computer languages are really portable in practice. An additional complicating factor, especially in the commercial environment, is that the resulting software must be efficient. This paper describes the design and successful implementation of a 500,000+ line portable FORTRAN 77 package for the processing of seismic data. The package exhibits demonstrably high efficiency on a wide variety of machines from minicomputers to the largest supercomputers. Experiences gained during this exercise throw much light on the integration of the various thought processes which occur during the software engineering cycle, especially the notion of locality. 相似文献
60.
Royzman Edward B.; Cassidy Kimberly Wright; Baron Jonathan 《Canadian Metallurgical Quarterly》2003,7(1):38
This article reviews the evidence and theory pertaining to a form of perspective-taking failure--a difficulty in setting aside the privileged information that one knows to be unavailable to another party. The authors argue that this bias (epistemic egocentrism, or EE) is a general feature of human cognition and has been tapped by 2 independent and largely uncommunicating research traditions: the theory-of-mind tradition in developmental psychology and, with more sensitive probes, the "heuristics and biases" tradition in the psychology of human judgment. This article sets the stage for facilitating communication between these traditions as well as for the recognition of EE's breadth and potential interdisciplinary significance. The authors propose a life-span account and a tentative taxonomy of EE; and they highlight the interdisciplinary significance of EE by discussing its implications for normative ethics. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献