全文获取类型
收费全文 | 1614篇 |
免费 | 26篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 11篇 |
综合类 | 1篇 |
化学工业 | 195篇 |
金属工艺 | 11篇 |
机械仪表 | 28篇 |
建筑科学 | 80篇 |
矿业工程 | 8篇 |
能源动力 | 33篇 |
轻工业 | 201篇 |
水利工程 | 16篇 |
石油天然气 | 3篇 |
无线电 | 126篇 |
一般工业技术 | 220篇 |
冶金工业 | 502篇 |
原子能技术 | 18篇 |
自动化技术 | 189篇 |
出版年
2023年 | 6篇 |
2022年 | 7篇 |
2021年 | 18篇 |
2020年 | 14篇 |
2019年 | 20篇 |
2018年 | 18篇 |
2017年 | 23篇 |
2016年 | 12篇 |
2015年 | 17篇 |
2014年 | 27篇 |
2013年 | 80篇 |
2012年 | 71篇 |
2011年 | 54篇 |
2010年 | 50篇 |
2009年 | 49篇 |
2008年 | 76篇 |
2007年 | 68篇 |
2006年 | 51篇 |
2005年 | 56篇 |
2004年 | 38篇 |
2003年 | 45篇 |
2002年 | 38篇 |
2001年 | 39篇 |
2000年 | 42篇 |
1999年 | 35篇 |
1998年 | 125篇 |
1997年 | 77篇 |
1996年 | 57篇 |
1995年 | 40篇 |
1994年 | 38篇 |
1993年 | 34篇 |
1992年 | 18篇 |
1991年 | 27篇 |
1990年 | 15篇 |
1989年 | 15篇 |
1988年 | 14篇 |
1987年 | 16篇 |
1986年 | 21篇 |
1985年 | 25篇 |
1984年 | 15篇 |
1983年 | 10篇 |
1982年 | 7篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1979年 | 10篇 |
1978年 | 8篇 |
1977年 | 13篇 |
1976年 | 23篇 |
1975年 | 7篇 |
1974年 | 9篇 |
排序方式: 共有1642条查询结果,搜索用时 8 毫秒
11.
12.
JF McCarthy DJ Cook MG Massad Y Sano KJ O''Malley NR Ratliff RW Stewart NG Smedira RC Starling JB Young PM McCarthy 《Canadian Metallurgical Quarterly》1998,14(2):197-200
28 isolates of canine parvovirus type-2 (CPV-2) were obtained from dogs with hemorrhagic gastroenteritis in Italy. The antigenic structure of CPV-2 isolates was characterized, using four discriminating monoclonal antibodies. In addition, four vaccinal strains were examined. Similar to reports from Australia and the United Kingdom, a much higher prevalence of CPV-2a (25/28 isolates) was observed than the other variant type, CPV-2b (3/28 isolates). DNA fragments (2.2 kbp) of representative strains of CPV-2, CPV-2a and CPV-2b were amplified by the polymerase chain reaction (PCR) and the products were digested by the restriction enzymes (RE) RsaI, HpaII, HindIII and PvuII. The RvaI enzyme allows the differentiation of CPV-2 from CPV-2a and CPV-2b. 相似文献
13.
MA Heneghan B Cleary M Murray TA O'Gorman CF McCarthy 《Canadian Metallurgical Quarterly》1998,43(6):1356-1361
Thromboembolic events frequently complicate the clinical course of patients with inflammatory bowel disease (IBD). Hereditary thrombophilia may contribute to this tendency. Resistance to activated protein C is the most recently described thrombophilic state and may account for up to 40% of patients with thrombophilia. Thirty-seven patients with IBD were studied (mean age 44 years, range 18-82 years). Three patients had a history of thrombotic episodes. The 37 controls included 23 men and 17 women (mean age 48 years, range 16-89 years). Disease activity was assessed using the Harvey Bradshaw index for patients with Crohn's disease and the Truelove and Witts grading system for patients with ulcerative colitis. Levels of fibrinogen, antithrombin III (ATIII), protein C, protein S, activated protein C resistance (APCR), and the presence of a lupus anticoagulant (LA) were determined. Median ATIII levels in patients with IBD were significantly lower than controls (98% vs 106%, P = 0.007), while fibrinogen was elevated (4.2 vs 3.3 g/liter, P = 0.026) despite quiescent disease activity. LA was detected in 7/37 patients in the IBD group compared to 0/37 controls. (chi2 = 5.68, P = 0.017). No significant difference was observed in levels of inherited thrombophilic factors and in particular APCR between IBD patients and controls. In conclusion, the presence of inherited thrombophilic defects, in particular APCR, is uncommon in patients with IBD and does not merit routine screening. 相似文献
14.
PURPOSE: This case report describes the clinical, scintigraphic, and pathologic findings in a patient with an unexpected finding of a cutaneous malignant melanoma. METHOD: Multiple imaging studies were done, as was a pathologic examination of a suspicious pigmented lesion on the patient's back. RESULT: A Tc-99m MDP bone scan showed diffuse uptake in the skeleton, lungs, kidneys, and stomach. CONCLUSION: Metastatic calcification, as shown by isotope scintigraphy, is an unusual manifestation of metastatic cancer from a primary cutaneous melanoma. 相似文献
15.
Hemoptysis secondary to an aortobronchial fistula is rare and uniformly fatal when left untreated. The authors describe a case of massive hemoptysis caused by an aortopulmonary fistula in an infected Dacron graft used successfully to repair a coarctation of the aorta. 相似文献
16.
Andy Gill Tristan Bull Andrew Farmer Garrin Kimmell Ed Komp 《Higher-Order and Symbolic Computation》2012,25(2-4):255-274
In this article we overview the design and implementation of the second generation of Kansas Lava. Driven by the needs and experiences of implementing telemetry decoders and other circuits, we have made a number of improvements to both the external API and the internal representations used. We have retained our dual shallow/deep representation of signals in general, but now have a number of externally visible abstractions for combinatorial and sequential circuits, and enabled signals. We introduce these abstractions, as well as our abstractions for reading and writing memory. Internally, we found the need to represent unknown values inside our circuits, so we made aggressive use of associated type families to lift our values to allow unknowns, in a principled and regular way. We discuss this design decision, how it unfortunately complicates the internals of Kansas Lava, and how we mitigate this complexity. Finally, when connecting Kansas Lava to the real world, the standardized idiom of using named input and output ports is provided by Kansas Lava using a new monad, called Fabric. We present the design of this Fabric monad, and illustrate its use in a small but complete example. 相似文献
17.
McCarthy R 《Food management》1985,20(3):62-7, 102-8, 112 passim
18.
McCarthy R 《Food management》1985,20(4):158-64, 168
19.
Ed Tallent 《国际互联网参考资料服务季刊》2013,18(3):83-89
Abstract Inter-play, an on-line index to plays in collections, anthologies and periodicals, provides easy access to the locations of printed plays by making citations for the location(s) of each play searchable by author and/or title. The process of converting the original card file play index into an electronic database available on the World Wide Web is described. The index has been designed to provide easy access to and broad coverage of available plays. New titles are added to the file on a regular basis, placing this Web publication squarely in the electronic journal arena. 相似文献
20.
Kirk Weller Ilana Arnon Ed Dubinsky 《Canadian Journal of Science, Mathematics, & Technology Education》2013,13(2):129-159
Abstract In an earlier study of preservice elementary and middle school teachers’ beliefs about repeating decimals, Weller, Arnon, and Dubinsky (2009) reported on a comparison of the mathematical performance of 77 preservice teachers who completed an APOS-based instructional unit with 127 preservice teachers who completed traditional instruction. The purpose of the current study, based on 47 interviews conducted 4 months after the instruction, during which time there was no further instruction on this topic, is to determine the strength and stability (over time) of the students’ beliefs, to uncover thinking that did not arise in the earlier study, and to see whether the interviews yield similar comparative results. The interviews did uncover changes in student thinking. The students who received the APOS-based instruction developed stronger and more stable (over time) beliefs that a repeating decimal is a number; a repeating decimal has a fraction or integer to which it corresponds; a repeating decimal in general equals its corresponding fraction or integer; and, in particular, In addition, a number of indices and categories were developed that may prove useful in other studies consisting of the comparison of interview and questionnaire data involving a large number of interview subjects. 相似文献