全文获取类型
收费全文 | 1373篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
化学工业 | 76篇 |
金属工艺 | 12篇 |
机械仪表 | 7篇 |
建筑科学 | 2篇 |
能源动力 | 14篇 |
轻工业 | 21篇 |
水利工程 | 1篇 |
石油天然气 | 1篇 |
无线电 | 9篇 |
一般工业技术 | 14篇 |
冶金工业 | 1207篇 |
原子能技术 | 2篇 |
自动化技术 | 13篇 |
出版年
2018年 | 3篇 |
2016年 | 5篇 |
2014年 | 3篇 |
2013年 | 6篇 |
2012年 | 14篇 |
2011年 | 7篇 |
2009年 | 7篇 |
2007年 | 7篇 |
2006年 | 6篇 |
2005年 | 4篇 |
2003年 | 7篇 |
2001年 | 7篇 |
1999年 | 45篇 |
1998年 | 346篇 |
1997年 | 206篇 |
1996年 | 147篇 |
1995年 | 64篇 |
1994年 | 61篇 |
1993年 | 79篇 |
1992年 | 14篇 |
1991年 | 16篇 |
1990年 | 25篇 |
1989年 | 21篇 |
1988年 | 23篇 |
1987年 | 23篇 |
1986年 | 19篇 |
1985年 | 13篇 |
1984年 | 2篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 9篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 34篇 |
1976年 | 74篇 |
1975年 | 6篇 |
1973年 | 3篇 |
1946年 | 2篇 |
1944年 | 2篇 |
1943年 | 2篇 |
1941年 | 2篇 |
1940年 | 2篇 |
1939年 | 2篇 |
1938年 | 2篇 |
1937年 | 4篇 |
1936年 | 2篇 |
1935年 | 2篇 |
1934年 | 3篇 |
1926年 | 2篇 |
排序方式: 共有1379条查询结果,搜索用时 15 毫秒
81.
Bell T.H. Barrow B.J. Miller J.T. 《Geoscience and Remote Sensing, IEEE Transactions on》2001,39(6):1286-1293
This paper reviews the problem of subsurface discrimination using electromagnetic induction (EMI) sensors. Typically, discrimination is based on differences in the multiaxis magnetic polarizability between different objects. They review work on frequency and time domain systems, and their interrelationship. They present the results of comprehensive measurements of the multiaxis EMI response of a variety of inert ordnance items, ordnance fragments, and scrap metal pieces recovered from firing ranges. The extent to which the distributions of the eigenvalues of magnetic polarizability for the different classes of objects do not overlap establishes an upper bound on discrimination. For various reasons, the eigenvalues cannot always be accurately determined using data collected above a buried target. This tends to increase the overlap of the distributions, and hence degrade discrimination performance 相似文献
82.
83.
84.
RT Skarda 《Canadian Metallurgical Quarterly》1999,214(1):37-39
OBJECTIVE: To assess the results of laparoscopic splenectomy as a treatment for immune thrombocytopenic purpura (ITP). MATERIAL AND METHODS: We conducted a retrospective study of all patients who underwent laparoscopic splenectomy for ITP at our institution between August 1992 and May 1997. RESULTS: Of 27 patients who underwent attempted laparoscopic splenectomy for ITP at our institution during the study period, 26 had completion of the procedure without conversion to an open splenectomy. The median postoperative hospital stay was 1.5 days, and no postoperative deaths occurred. In one patient, pancreatitis developed postoperatively. In four patients, splenectomy failed--two initially and two subsequently--and reinstitution of medical therapy was necessary. The other patients have remained free of medication, and 19 patients have platelet counts greater than 100 x 10(9)/L. The 3-year actuarial success rate was 81.5%. Response to corticosteroid therapy preoperatively may be an indicator of success of splenectomy. CONCLUSION: Laparoscopic splenectomy is safe and allows prompt recovery. Long-term response rates are similar to those achieved with open splenectomy. 相似文献
85.
BS Iyengar RT Dorr DS Alberts EM Hersh SE Salmon WA Remers 《Canadian Metallurgical Quarterly》1999,42(3):510-514
A set of 20 2-cyanoaziridine-1-carboxamides was synthesized from 2-cyanoaziridine and appropriate isocyanates. These compounds were active against a variety of solid and hematological tumor cells in culture, including strains resistant to doxorubicin and mitoxantrone. Their potencies in these assays correlated with the lipophilicity of substituents. The N-phenyl derivative was more potent and equally effective to imexon, a cyclized 2-cyanoaziridine-1-carboxamide of clinical interest, against cloned fresh human tumors. 相似文献
86.
ML Mayer SJ Clark TR Konrad VA Freeman RT Slifkin 《Canadian Metallurgical Quarterly》1999,89(2):164-170
OBJECTIVES: This study assessed the influence of public policies on the immunization status of 2-year old children in the United States. METHODS: Up-to-dateness for the primary immunization series was assessed in a national sample of 8100 children from the 1988 National Maternal and Infant Health Survey and its 1991 Longitudinal Follow-Up. RESULTS: Documented immunization rates of this sample were 33% for poor children and 44% for others. More widespread Medicated coverage was associated with greater likelihood of up-to-dateness among poor children. Up-to-dateness was more likely for poor children with public rather than private sources of routine pediatric care, but all children living in states where most immunizations were delivered in the public sector were less likely to be up to date. Poor children in state with partial vaccine replacement programs were less likely to be up to date than those in free-market purchase states. CONCLUSIONS: While state policies can enhance immunization delivery for poor children, heavy reliance on public sector immunization does not ensure timely receipt of vaccines. Public- and private-sector collaboration is necessary to protect children from vaccine-preventable diseases. 相似文献
87.
88.
RA Wain GL Berdejo WN Delvalle RT Lyon LA Sanchez WD Suggs T Ohki E Lipsitz FJ Veith 《Canadian Metallurgical Quarterly》1999,29(1):100-7; discussion 107-9
PURPOSE: Arteriography is the diagnostic test of choice before lower extremity revascularization, because it is a means of pinpointing stenotic or occluded arteries and defining optimal sites for the origin and termination of bypass grafts. We evaluated whether a duplex ultrasound scan, used as an alternative to arteriography, could be used as a means of accurately predicting the proximal and distal anastomotic sites in patients requiring peripheral bypass grafts and, therefore, replace standard preoperative arteriography. METHODS: Forty-one patients who required infrainguinal bypass grafts underwent preoperative duplex arterial mapping (DAM). Based on these studies, an observer blinded to the operation performed predicted what operation the patient required and the best site for the proximal and distal anastomoses. These predictions were compared with the actual anastomotic sites chosen by the surgeon. RESULTS: Whether a femoropopliteal or an infrapopliteal bypass graft was required was predicted correctly by means of DAM in 37 patients (90%). In addition, both anastomotic sites in 18 of 20 patients (90%) who had femoropopliteal bypass grafts and 5 of 21 patients (24%) who had infrapopliteal procedures were correctly predicted by means of DAM. CONCLUSION: DAM is a reliable means of predicting whether patients will require femoropopliteal or infrapopliteal bypass grafts, and, when a patient requires a femoropopliteal bypass graft, the actual location of both anastomoses can also be accurately predicted. Therefore, DAM appears able to replace conventional preoperative arteriography in most patients found to require femoropopliteal reconstruction. Patients who are predicted by means of DAM to require crural or pedal bypass grafts should still undergo preoperative contrast studies to confirm these results and to more precisely locate the anastomotic sites. 相似文献
89.
90.