全文获取类型
收费全文 | 14245篇 |
免费 | 1092篇 |
国内免费 | 213篇 |
学科分类
工业技术 | 15550篇 |
出版年
2024年 | 33篇 |
2023年 | 186篇 |
2022年 | 251篇 |
2021年 | 500篇 |
2020年 | 389篇 |
2019年 | 386篇 |
2018年 | 508篇 |
2017年 | 574篇 |
2016年 | 514篇 |
2015年 | 483篇 |
2014年 | 679篇 |
2013年 | 1131篇 |
2012年 | 918篇 |
2011年 | 1014篇 |
2010年 | 835篇 |
2009年 | 752篇 |
2008年 | 820篇 |
2007年 | 745篇 |
2006年 | 734篇 |
2005年 | 505篇 |
2004年 | 407篇 |
2003年 | 383篇 |
2002年 | 343篇 |
2001年 | 328篇 |
2000年 | 290篇 |
1999年 | 265篇 |
1998年 | 328篇 |
1997年 | 248篇 |
1996年 | 184篇 |
1995年 | 168篇 |
1994年 | 130篇 |
1993年 | 88篇 |
1992年 | 63篇 |
1991年 | 42篇 |
1990年 | 38篇 |
1989年 | 40篇 |
1988年 | 34篇 |
1987年 | 21篇 |
1986年 | 21篇 |
1985年 | 22篇 |
1984年 | 25篇 |
1983年 | 28篇 |
1982年 | 21篇 |
1981年 | 8篇 |
1980年 | 12篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1977年 | 10篇 |
1976年 | 12篇 |
1975年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
61.
Fibroblast cultures were established from the skin of normal and psoriatic subjects. The response to 1 alpha,25-dihydroxyvitamin D3 [1,25-(OH)2D3] of each kind of cells was assessed by measuring tritiated thymidine incorporation into DNA as an index of cell proliferation. We found that both types of cells responded with a similar dose- and time-dependent inhibition of thymidine incorporation. We also studied the response of the mRNA encoding the proto-oncogene c-myc, since its level is associated to the proliferative state in many cell types. Psoriatic fibroblasts contained higher basal amounts of c-myc RNA than control fibroblasts. Addition of 1,25-(OH)2D3 to the culture medium induced a time-dependent increase of c-myc RNA in psoriatic fibroblasts but not in controls. As a control, retinoic acid had no effect in any of the two cell types. It is concluded that in primary normal human fibroblasts, c-myc RNA levels are not correlated with the proliferative state, and that there is an altered expression of this proto-oncogene in psoriasis. 相似文献
62.
63.
本文简单介绍NexGen公司最新设计出的Nx586CPU。它是一种80×86兼容的处理器,文中介绍了它的微体系结构,RISC86指令等。 相似文献
64.
本文介绍了一种鱼类耳石样品的扫描电镜制样方法,通过对草鱼耳石进行包埋,抛磨,并用合适的腐蚀剂处理,用SEM成功地观察了耳石的日轮及超微结构,该方法简便易行,保证所观察耳石样品的微观结构完整与清晰。 相似文献
65.
66.
67.
68.
Discusses common presenting complaints and those of emergent significance that have an organic etiology. The following categories are discussed: head, eyes, ears, throat, neck, cardiac, respiratory, gastrointestinal, genito-urinary, musculoskeletal, and neurologic complaints. It is suggested that many therapists lack adequate medical information to suspect the presence of organic problems when symptoms are indistinguishable from psychogenic/psychosomatic problems. (4 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
69.
The effects of cooking temperature, time and temperature of brine-salting, and temperature of ripening on the behavior of Enterobacteriaceae in Manchego cheese were studied. Fifty lots of cheese from raw ewe's milk manufactured and ripened under different conditions were investigated throughout a 60-day ripening period. Differences in pH values due to temperature-dependent whey retention accounted for the effect of cooking temperature on coliform and fecal coliform counts. Temperature of brine-salting had no effect on Enterobacteriaceae counts, but a significant effect of salting time on Enterobacteriaceae and fecal coliform counts was detected. Ripening temperature was the manufacturing variable with greatest influence (P<.01) on Enterobacteriaceae and coliform counts during the whole curing period. 相似文献
70.
A method based on cluster analysis techniques is proposed in order to obtain representative local wind patterns. Modeling renewable energy systems, in an accurate way which strongly depends on wind loads, requires reliable data to analyze their response and evaluate their performance. Otherwise poor agreement with the models may be obtained. In a case study for La Paz, Baja California Sur, Mexico, four different wind patterns were obtained from a one-year data set recorded at 10-min intervals. 相似文献