全文获取类型
收费全文 | 26762篇 |
免费 | 708篇 |
国内免费 | 33篇 |
专业分类
电工技术 | 330篇 |
综合类 | 14篇 |
化学工业 | 5924篇 |
金属工艺 | 518篇 |
机械仪表 | 464篇 |
建筑科学 | 1160篇 |
矿业工程 | 332篇 |
能源动力 | 650篇 |
轻工业 | 1725篇 |
水利工程 | 226篇 |
石油天然气 | 245篇 |
无线电 | 1711篇 |
一般工业技术 | 4077篇 |
冶金工业 | 6152篇 |
原子能技术 | 265篇 |
自动化技术 | 3710篇 |
出版年
2022年 | 247篇 |
2021年 | 411篇 |
2020年 | 266篇 |
2019年 | 347篇 |
2018年 | 422篇 |
2017年 | 369篇 |
2016年 | 487篇 |
2015年 | 393篇 |
2014年 | 615篇 |
2013年 | 1652篇 |
2012年 | 937篇 |
2011年 | 1201篇 |
2010年 | 922篇 |
2009年 | 971篇 |
2008年 | 1148篇 |
2007年 | 1063篇 |
2006年 | 974篇 |
2005年 | 882篇 |
2004年 | 743篇 |
2003年 | 711篇 |
2002年 | 706篇 |
2001年 | 485篇 |
2000年 | 390篇 |
1999年 | 446篇 |
1998年 | 440篇 |
1997年 | 427篇 |
1996年 | 473篇 |
1995年 | 443篇 |
1994年 | 451篇 |
1993年 | 437篇 |
1992年 | 431篇 |
1991年 | 271篇 |
1990年 | 410篇 |
1989年 | 387篇 |
1988年 | 336篇 |
1987年 | 404篇 |
1986年 | 348篇 |
1985年 | 441篇 |
1984年 | 463篇 |
1983年 | 398篇 |
1982年 | 375篇 |
1981年 | 297篇 |
1980年 | 298篇 |
1979年 | 357篇 |
1978年 | 299篇 |
1977年 | 238篇 |
1976年 | 217篇 |
1975年 | 245篇 |
1974年 | 217篇 |
1973年 | 224篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
In previous studies of cholecystokinin's (CCK's) effect on consumption, physical features (e.g., taste, texture, and odor) of test meals were confounded with the nutritive expectancies elicited by those features. To separately assess the role of these two factors in supporting CCK's suppression-of-intake effect, we varied the caloric expectancies elicited by a flavored test solution, while holding constant its actual caloric density, as well as all other unconditioned stimulus features. On alternate days for a 12-day period, hungry rats drank grape or orange Kool-Aid (noncaloric) mixed with a caloric 5% ethanol solution; on the other days, they drank the alternate flavor mixed with plain water. In a subsequent choice test between the flavored solutions without ethanol, the ethanol-associated flavor (Ef) was preferred over the water-associated flavor (Wf). Two days later, the rats were injected with either cholecystokinin octapeptide (CCK-8; ip, 2 μg/kg) or isotonic saline, and then given access to their Ef or their Wf for 1 hr. Consumption of the Ef was supressed by CCK-8; intake of the Wf was unaffected. These results suggest that CCK-8's effectiveness in suppressing intake of a test meal may be treated not to the unconditioned stimulus features of that meal but to the nutritive expectations elicited by those features. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
122.
Miller Ralph R.; Barnet Robert C.; Grahame Nicholas J. 《Canadian Metallurgical Quarterly》1995,117(3):363
The Rescorla-Wagner model has been the most influential theory of associative learning to emerge from the study of animal behavior over the last 25 years. Recently, equivalence to this model has become a benchmark in assessing connectionist models, with such equivalence often achieved by incorporating the Widrow-Hoff delta rule. This article presents the Rescorla-Wagner model's basic assumptions, reviews some of the model's predictive successes and failures, relates the failures to the model's assumptions, and discusses the model's heuristic value. It is concluded that the model has had a positive influence on the study of simple associative learning by stimulating research and contributing to new model development. However, this benefit should neither lead to the model being regarded as inherently "correct" nor imply that its predictions can be profitably used to assess other models. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
123.
This article quantifies errors arising from various integration methods and from sampling density in the numerical estimation of colorimetric integrals, e.g., tristimulus values. Both data sampling density and various numerical integration method errors will be distinguished. A test is presented to quantify sampling interval requirements for accurate colorimetric calculations for various illuminants. © 1992 John Wiley & Sons, Inc. 相似文献
124.
125.
The high-temperature thermodynamic behavior of the Cr-Cr2N-N2 system has been investigated in the temperature range 1450 to 1850 K by measuring the equilibrium pressure of nitrogen gas
over pure chromium metal and chromium nitride Cr2N. From the experimental data, the standard free energy and enthalpy of formation of Cr2N have been determined to be: ΔH° = −104. ± 10 (KJ. mol−1 Cr2N) ΔG° = −104. + 0.04987 ± 3.8 (KJ. mol−1 Cr2N) 相似文献
126.
Examined intake profiles of 54 depressed women survivors of child sexual abuse presenting for a specialized group therapy program at a community mental health center. The 32 therapy completers were compared with the 22 dropouts. Both groups possessed extensive and severe childhood and adult abuse histories. Both were extremely socially disadvantaged and clinically impaired as measured on the Millon Clinical Multiaxial Inventory (MCMI). Dropouts were more likely to have been battered as children and to have been sexually abused only within the family. Completers were more likely to have been multiply offended both by intrafamilial and extrafamilial perpetrators. The groups differed in terms of marital status and extent of economic dependence on spouse. Dropouts appeared to be more actively enmeshed in the abuse cycle at the time of therapy. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
127.
Forster Jean L.; Jeffery Robert W.; Schmid Thomas L.; Kramer F. Matthew 《Canadian Metallurgical Quarterly》1988,7(6):515
Evaluated the feasibility and effectiveness of a program for weight gain prevention (WGP) in normal adults. 219 Ss were randomized to either WGP treatment or no treatment for 12 mo. The treatment group received monthly newsletters relating to weight management, participated in a financial incentive system, and were offered an optional 4-session education course in the 6th mo of the program. Results demonstrate high interest in WGP among Ss who were not objectively overweight. Participation, as measured by return of postcards sent with each newsletter, was approximately 75%. Results after 1 yr show a net weight loss of 1.8 lb in the group receiving the program compared with controls. 82% of participants maintained or lost weight, compared with 56% of controls. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
128.
Designing a Production Line to Maximize Profit 总被引:1,自引:0,他引:1
The relationship between profitability and efficiency in a production line is discussed at length for the continuous production model. We prove that a solution which maximizes efficiency will not necessarily maximize profit. Several useful relationships between profitability and efficiency are developed which can greatly enhance computational efficiency. A solution procedure is developed which will determine the optimal number of work stations by maximizing an assumed profit function. An example is provided to illustrate these relationships and the entire solution procedure. 相似文献
129.
Both neuropsychology and psychology in general have been enhanced markedly by brain–behavior models derived from the study of the epilepsies. A significant body of neuropsychological concepts originated or were confirmed through epilepsy-based treatment and research. These concepts include the peri-Rolandic homunculus, the role of the hippocampal–temporal lobe complex in cognitive memory, hemisphere plasticity for speech in childhood, the intracarotid amytal procedure for determining hemisphere memory patency, and hemisphere-based models of cognition confirmed through human commissurotomy. Personality and social–emotional research in epilepsy are additional areas in which new conceptual models grounded in psychological science can both repay our debt to the epilepsies and provide much needed psychological research and treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
130.
Jonathan Cherneff Robert Logcher Jerome Connor Nicholas Patrikalakis 《Research in Engineering Design》1992,3(4):195-210
A method for machine interpretation of architectural (or other) schematic drawings is presented. The central problem is to build an efficient drawing parser (i.e., a program that identifies the semantic entities, characteristics, and relationships that are represented in the drawing). The parser is built from specifications of the drawing grammar and an underlying spatial model. The grammar describes what to look for, and the spatial model enables the parser to find it quickly. Coupled with existing optical recognition technology, this technique enables the use of drawings directly as: (1) a database to drive various Architecture-Engineering-Construction (AEC) applications; (2) a communication protocol to integrate CAD systems; (3) a traditional user interface. 相似文献