全文获取类型
收费全文 | 1958篇 |
免费 | 31篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 26篇 |
化学工业 | 101篇 |
金属工艺 | 14篇 |
机械仪表 | 12篇 |
建筑科学 | 32篇 |
能源动力 | 9篇 |
轻工业 | 85篇 |
水利工程 | 2篇 |
石油天然气 | 3篇 |
无线电 | 117篇 |
一般工业技术 | 85篇 |
冶金工业 | 1464篇 |
原子能技术 | 4篇 |
自动化技术 | 36篇 |
出版年
2023年 | 9篇 |
2022年 | 11篇 |
2021年 | 6篇 |
2020年 | 13篇 |
2019年 | 9篇 |
2018年 | 12篇 |
2017年 | 14篇 |
2016年 | 15篇 |
2015年 | 20篇 |
2014年 | 24篇 |
2013年 | 29篇 |
2012年 | 25篇 |
2011年 | 25篇 |
2010年 | 21篇 |
2009年 | 28篇 |
2008年 | 36篇 |
2007年 | 24篇 |
2006年 | 22篇 |
2005年 | 22篇 |
2004年 | 29篇 |
2003年 | 25篇 |
2002年 | 16篇 |
2001年 | 12篇 |
2000年 | 17篇 |
1999年 | 74篇 |
1998年 | 461篇 |
1997年 | 264篇 |
1996年 | 180篇 |
1995年 | 82篇 |
1994年 | 86篇 |
1993年 | 77篇 |
1992年 | 14篇 |
1991年 | 17篇 |
1990年 | 20篇 |
1989年 | 28篇 |
1988年 | 21篇 |
1987年 | 15篇 |
1986年 | 18篇 |
1985年 | 13篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 9篇 |
1980年 | 14篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 37篇 |
1976年 | 77篇 |
1975年 | 4篇 |
1969年 | 1篇 |
1968年 | 1篇 |
排序方式: 共有1990条查询结果,搜索用时 11 毫秒
1.
Machine Learning - We consider the problem of learning a binary classifier from only positive and unlabeled observations (called PU learning). Recent studies in PU learning have shown superior... 相似文献
2.
SG Bryant 《Canadian Metallurgical Quarterly》1996,53(19):2339-40, 2343
3.
SG Rijpkema RG Herbes N Verbeek-De Kruif JF Schellekens 《Canadian Metallurgical Quarterly》1996,117(3):563-566
Epiglottic disruption is an uncommon injury usually associated with significant supraglottic trauma. This injury may be overlooked because of the difficulty in examining the larynx or other associated severe injuries. We present two cases of clinically unsuspected epiglottic disruption that were first seen on MR images of the neck. 相似文献
4.
SA Khotimchenko VM Kodentsova IA Alekseeva SG Vlaskina OA Vrzhesinskaia AA Sokol''nikov LA Kharitonchik IP Aleshko-Ozhevskií LV Sheviakova 《Canadian Metallurgical Quarterly》1997,43(3):158-164
Gamma delta T-Cells represent a minor subpopulation of T-lymphocytes in man and their role in normal and diseased human skin is unknown. This article is a comprehensive review of T-lymphocytes bearing the gamma delta T-cell receptor in normal and pathological human skin. Firstly, we have documented the occurrence of gamma delta T-cells in normal skin and in a range of reactive and malignant skin conditions. We have then discussed the experimental findings regarding the repertoire used by gamma delta T-cells in normal human skin and in cutaneous disorders with an increased percentage of gamma delta T-cells. 相似文献
5.
6.
Human immunodeficiency virus (HIV) infection of the thymus could have profound effects on development of the immune response, particularly in children. We and others have established that in addition to infecting and depleting CD4-bearing thymocytes, functional HIV proviruses are found in thymocytes lacking surface CD4 expression. Using in vitro thymocyte cultures, we show that neither HIV-mediated down regulation of CD4 nor CD4-independent infection contributes to the localization of HIV in cells lacking the primary virus receptor. Rather, infection of a CD4-positive precursor cell (CD4 positive/CD8 positive) with subsequent differentiation into a mature CD4-negative phenotype results in productively infected CD4-negative cells. This novel mechanism may contribute to pathogenesis by distributing viral sequences into functional subsets of T cells typically refractory to HIV infection and could account for the presence of viral DNA in CD8-positive lymphocytes recently observed in patients. 相似文献
7.
HJ Lee HK Ha MH Kim YK Jeong PN Kim MG Lee JS Kim DJ Suh SG Lee YI Min YH Auh 《Canadian Metallurgical Quarterly》1997,169(2):517-520
OBJECTIVE: The purpose of this study was to evaluate ERCP and CT findings of ectopic drainage of the common bile duct into the duodenal bulb. CONCLUSION: Although rare, the diagnosis of ectopic drainage of the common bile duct into the duodenal bulb is important to prevent inadvertent damage during biliary tract or gastric surgery and to clarify the cause of chronic peptic ulcers. 相似文献
8.
EB Poluéktova NK Khitrov VI Andreev SG Pak BK Danilkin 《Canadian Metallurgical Quarterly》1997,69(11):14-16
Changes in the activity of acid phosphatase (AP) and its isoenzymes (tartrate-insensitive AP and formalin-insensitive AP) were investigated in patients with food poisoning in the course of the disease. The activity of AP and its isoenzymes in the serum started to grow in early convalescence and reached maximum in late convalescence. Total activity of AP in food toxic infections consists primarily of the activity of its platelet fraction. AP activity may serve as an additional criterion to predict vascular platelet involvement of hemostasis. 相似文献
9.
10.
We propose a new, less costly, design to test the equivalence of digital versus analogue mammography in terms of sensitivity and specificity. Because breast cancer is a rare event among asymptomatic women, the sample size for testing equivalence of sensitivity is larger than that for testing equivalence of specificity. Hence calculations of sample size are based on sensitivity. With the proposed design it is possible to achieve the same power as a completely paired design by increasing the number of less costly analogue mammograms and not giving the more expensive digital mammograms to some randomly selected subjects who are negative on the analogue mammogram. The key idea is that subjects who are negative on the analogue mammogram are unlikely to have cancer and hence contribute less information for estimating sensitivity than subjects who are positive on the analogue mammogram. To ascertain disease state among subjects not biopsied, we propose another analogue mammogram at a later time determined by a natural history model. The design differs from a double sampling design because it compares two imperfect tests instead of combining information from a perfect and imperfect test. 相似文献