全文获取类型
收费全文 | 27450篇 |
免费 | 881篇 |
国内免费 | 88篇 |
专业分类
电工技术 | 337篇 |
综合类 | 47篇 |
化学工业 | 5833篇 |
金属工艺 | 529篇 |
机械仪表 | 519篇 |
建筑科学 | 1825篇 |
矿业工程 | 173篇 |
能源动力 | 756篇 |
轻工业 | 2464篇 |
水利工程 | 204篇 |
石油天然气 | 77篇 |
武器工业 | 1篇 |
无线电 | 1959篇 |
一般工业技术 | 4770篇 |
冶金工业 | 4394篇 |
原子能技术 | 188篇 |
自动化技术 | 4343篇 |
出版年
2023年 | 161篇 |
2022年 | 335篇 |
2021年 | 567篇 |
2020年 | 342篇 |
2019年 | 349篇 |
2018年 | 533篇 |
2017年 | 459篇 |
2016年 | 565篇 |
2015年 | 510篇 |
2014年 | 765篇 |
2013年 | 1682篇 |
2012年 | 1206篇 |
2011年 | 1637篇 |
2010年 | 1193篇 |
2009年 | 1155篇 |
2008年 | 1393篇 |
2007年 | 1240篇 |
2006年 | 1048篇 |
2005年 | 987篇 |
2004年 | 880篇 |
2003年 | 796篇 |
2002年 | 758篇 |
2001年 | 481篇 |
2000年 | 468篇 |
1999年 | 528篇 |
1998年 | 863篇 |
1997年 | 627篇 |
1996年 | 546篇 |
1995年 | 436篇 |
1994年 | 438篇 |
1993年 | 439篇 |
1992年 | 333篇 |
1991年 | 270篇 |
1990年 | 271篇 |
1989年 | 288篇 |
1988年 | 242篇 |
1987年 | 230篇 |
1986年 | 227篇 |
1985年 | 309篇 |
1984年 | 271篇 |
1983年 | 254篇 |
1982年 | 223篇 |
1981年 | 242篇 |
1980年 | 182篇 |
1979年 | 195篇 |
1978年 | 186篇 |
1977年 | 188篇 |
1976年 | 223篇 |
1975年 | 155篇 |
1974年 | 129篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
101.
102.
Hitchcock Janice M.; Sananes Catherine B.; Davis Michael 《Canadian Metallurgical Quarterly》1989,103(3):509
Bilateral electrolytic lesions of the central, but not the lateral, nucleus of the amgydala blocked shock sensitization of startle (the increase in startle produced by presentation of ten 0.6-mA footshocks in rapid succession). Lesions of the central nucleus also decreased reactivity to shock (jumping and flinching) during shock presentation. However, this decrease in reactivity cannot account for the blockade of shock sensitization, because when a higher shock intensity (1.0 mA) was used, producing equivalent reactivity to that of controls at 0.6 mA, central nucleus lesions still blocked shock sensitization. Moreover, lesions of the caudal part of the ventral amygdalofugal pathway, which carries central nucleus efferents to the startle reflex pathway, also blocked shock sensitization. It is hypothesized that shock activates the central nucleus of the amygdala, which increases startle through modulation of the startle pathway. Activation of the amygdala by shock may be the unconditioned response relevant for fear conditioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
103.
The dependence of the cetane number of hydrotreated light cycle oil on chemical composition has been investigated. Cetane number was related to hydrogen content and aromaticity. The latter was determined by high performance liquid chromatography and also by carbon-13 n.m.r. spectroscopy. Specific correlations were developed in each case and a regression coefficient of 0.99 and a standard error of 1.25 were obtained for the best case. The usefulness of predicting cetane number from fuel composition is discussed. 相似文献
104.
The available surgical and non-surgical therapy options for treatment of gallstone disease are presented. Conventional cholecystectomy is regarded as standard therapy of symptomatic cholecystolithiasis. Other modes of therapy may be indicated under certain circumstances, depending on the results of imaging procedures. In this context conventional X-ray examination, oral and intravenous cholecystography, sonography, computed tomography, endoscopic retrograde cholangiography/cholecystography, and magnetic resonance imaging are discussed and their influence on therapeutic decisions is explained. 相似文献
105.
106.
Evaluated the impact of pretreatment depression severity and functional impairment on the response of 2 samples of older depressed adolescents (115 Ss total divided into low-severity groups and high-severity groups) to 2 group cognitive-behavioral treatments. Differences between the 2 active treatments and between active treatment and a waiting-list control condition were expected to be greater in the more severely depressed-impaired group. Improvement for the 2 active treatments in comparison to the control condition was greater in the more severely depressed group in one of the samples but not the other. The prediction that the relative effectiveness of the 2 treatments would be accentuated in the more severely depressed adolescents received no support in either sample. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
107.
Stevenson D. Morow H. Blatecky A. Montgomery Davis P. Richardson P. Courter N.L.T. 《IEEE network》1994,8(6):32-38
The North Carolina Research and Education Network (NC-REN), formerly known as CONCERT, is an existing video and data network, owned and operated by MCNC. NC-REN's purpose has been to provide network-based support for collaboration in the research community within the state since 1985. The first major application planned for the North Carolina Information Highway (NCIH) is an interactive video distance learning system. A secondary application proposed is the use of Switched Multimegabit Data Service (SMDS) as a means of providing data communications services over NCIH. The user community currently supported by NC-REN has come to expect high levels of service, reliability, interoperability and performance for data and video communications. MCNC is committed to see that NC-REN users receive service that is equal to or better than what is currently provided by the existing network. The prospect of migrating NC-REN-provided services to NCIH-provided transport has raised challenging technical and unique service issues 相似文献
108.
109.
Lewinsohn Peter M.; Roberts Robert E.; Seeley John R.; Rohde Paul; Gotlib Ian H.; Hops Hyman 《Canadian Metallurgical Quarterly》1994,103(2):302
In a prospective study of adolescent depression, adolescents (N?=?1,508) were assessed at Time 1 and after 1 yr (Time 2) on psychosocial variables hypothesized to be associated with depression. Most psychosocial variables were associated with current (n?=?45) depression. Formerly depressed adolescents (n?=?217) continued to differ from never depressed controls on many of the psychosocial variables. Many of the depression-related measures also acted as risk factors for future depression (n?=?112), especially past depression, current other mental disorders, past suicide attempt, internalizing behavior problems, and physical symptoms. Young women were more likely to be, to become, and to have been depressed. Controlling for the psychosocial variables eliminated the gender difference for current and future but not for past depression. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
110.
Reviews the research concerning the possible functional roles of the prosodic aspects of infant-directed speech ("baby-talk"), and shows that this style of speaking could have both attentional and affective functions (in addition to linguistic ones). Studies of other speech registers could profit from taking similar approaches and even using similar techniques to those used in infant-directed speech research to tease apart the linguistic, attentional, and affective components of these other speaking styles. Nursing-home register is used to exemplify the importance of examining the social, emotional, and linguistic ramifications of a communication style separately. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献