全文获取类型
收费全文 | 1281篇 |
免费 | 5篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 1篇 |
综合类 | 4篇 |
化学工业 | 10篇 |
金属工艺 | 1篇 |
机械仪表 | 9篇 |
建筑科学 | 3篇 |
能源动力 | 2篇 |
轻工业 | 34篇 |
水利工程 | 1篇 |
石油天然气 | 1篇 |
无线电 | 2篇 |
一般工业技术 | 6篇 |
冶金工业 | 1198篇 |
原子能技术 | 1篇 |
自动化技术 | 19篇 |
出版年
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 4篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 1篇 |
2014年 | 2篇 |
2013年 | 12篇 |
2012年 | 3篇 |
2011年 | 2篇 |
2010年 | 6篇 |
2009年 | 2篇 |
2008年 | 3篇 |
2007年 | 10篇 |
2006年 | 2篇 |
2005年 | 2篇 |
2004年 | 6篇 |
2003年 | 1篇 |
2002年 | 3篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1999年 | 30篇 |
1998年 | 353篇 |
1997年 | 195篇 |
1996年 | 158篇 |
1995年 | 54篇 |
1994年 | 70篇 |
1993年 | 71篇 |
1992年 | 7篇 |
1991年 | 15篇 |
1990年 | 13篇 |
1989年 | 19篇 |
1988年 | 16篇 |
1987年 | 13篇 |
1986年 | 9篇 |
1985年 | 13篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 9篇 |
1979年 | 1篇 |
1978年 | 6篇 |
1977年 | 39篇 |
1976年 | 102篇 |
1975年 | 3篇 |
1972年 | 2篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有1292条查询结果,搜索用时 5 毫秒
61.
Diagnostic tools in the evaluation of patients with viral hepatitis undergoing liver transplantation
Familiarity with the diagnostic parameters of viral hepatitis is imperative in the liver transplantation arena. Chronic viral hepatitis B and C are among the most common categories of end-stage liver disease. The preoperative diagnosis, determination of recurrent infection, and the assessment of antiviral therapeutic efficacy are dependent on appropriate virological testing. Furthermore, liver transplant personnel are at a high risk for parenterally transmitted viral hepatitis infection. Knowledge and understanding of the serological patterns of acute and chronic viral hepatitis, as well as recognition of the immune status for one or more of these viruses, will facilitate prevention and treatment of viral hepatitis for these health care providers. 相似文献
62.
Various analytical, iterative and rebinning algorithms have been proposed for 3D reconstruction in positron emission tomography. This paper examines execution times of five analytical and rebinning algorithms. Meaningful comparisons are obtained by using similar software modules in all implementations. Reconstruction times are shown to differ by vast amounts: the Favor algorithm of Defrise et al is more than twice as fast as the widely used reprojection algorithm of Kinahan and Rogers; the Fourier rebinning algorithm (Fore) recently developed by Defrise is more than 15 times faster than the reprojection algorithm. 相似文献
63.
LS Prichep KR Alper S Kowalik H Merkin M Tom ER John MS Rosenthal 《Canadian Metallurgical Quarterly》1996,40(10):986-993
This study replicates preliminary findings reporting a quantitative electroencephalographic (QEEG) profile of crack cocaine dependence in abstinence. All subjects (n = 52) met criteria for DMS-III-R cocaine dependence (in the form of crack), and were residing in a drug-free therapeutic community. Baseline QEEG evaluations were conducted at intake (5-10 days after last use of crack, and at follow-up (1 month after last reported use). Previous findings of significant excess of relative alpha power and deficit of absolute and relative delta and theta power were replicated in this expanded group. Abnormalities were greater in anterior than posterior regions, and disturbances in interhemispheric relationships were also observed. Further, QEEG showed little change in the interval between the first and second evaluations. This QEEG profile may reflect persistent alterations in neurotransmission as a possible consequence of chronic cocaine exposure. 相似文献
64.
ER Broun JL Wheat PH Kneebone K Sundblad RA Hromas G Tricot 《Canadian Metallurgical Quarterly》1994,38(3):576-579
The purpose of the study reported here was to investigate the impact of prophylaxis against gram-positive infections in patients undergoing high-dose chemotherapy and autologous bone marrow transplantation in a randomized trial. Forty-three patients undergoing high-dose chemotherapy with autologous bone marrow transplant were enrolled in a nonblinded randomized trial to receive or not to receive prophylaxis for gram-positive infections with 10(6) U of penicillin intravenously (i.v.) every 6 h (q6h) (if penicillin allergic, 750 mg of vancomycin i.v. q12h) in addition to standard antimicrobial prophylaxis with 400 mg of norfloxacin orally three times a day, 200 mg of fluconazole orally once a day, and 5 mg of acyclovir per kg of body weight i.v. q12h. The patients were being treated for germ cell cancer (n = 15), breast cancer (n = 16), Hodgkin's disease (n = 3), non-Hodgkin's lymphoma (n = 4), acute myeloid leukemia (n = 1), acute lymphoblastic leukemia (n = 1), and ovarian cancer (n = 3). The trial was stopped because of excess morbidity in the form of streptococcal septic shock in the group not receiving gram-positive prophylaxis. There were significantly fewer overall infections (10 versus 3; P = 0.016) and streptococcal infections (9 versus 1; P = 0.0078) in the group receiving gram-positive prophylaxis. There were no significant differences in the numbers of deaths, duration of broad-spectrum antibiotics, or incidence of neutropenic fever between the two groups. Prophylaxis for gram-positive infections with penicillin or vancomycin is effective in reducing the incidence of streptococcal infections in patients undergoing high-dose chemotherapy and autologous bone marrow transplant. However, this approach may carry a risk of fostering resistance among streptococci to penicillin or vancomycin. 相似文献
65.
Yersinia pestis, the plague bacillus, has a plasminogen activator (pla) gene on the 9.5-kb plasmid pPla that is hypothesized to play a role in producing the foregut blockage in the flea vector that precedes transmission. In this study, however, Y. pestis that lacked pPla, the 70-kb virulence plasmid, or both plasmids, proved able to block Xenopsylla cheopis fleas normally. Blockage rates decreased with increasing environmental temperature for fleas infected with either wild type or pPla- Y. pestis. Thus, procoagulant ability of the Y. pestis pla gene product does not mediate blockage, nor does its ability to induce fibrinolysis at>28 degreesC account for failure to block at elevated temperatures. A Y. pestis strain that lacked all or part of the third plasmid of 110 kb, however, failed to colonize the flea midgut normally, indicating that one or more genes on the large plasmid may be required for vectorborne transmission. 相似文献
66.
A modification of the aspiration liver biopsy technique using a large-caliber disposable needle is described in an 18-month experience. One hundred forty liver biopsies were performed, obtaining adequate tissue in 98% of the patients. Complications occurred in 12 patients and were limited to pain at the biopsy site, epigastrium, or right shoulder; one instance of tachycardia and three of transient hypotension occurred. Thirty patients studied prospectively with liver scans and hematologic parameters failed to disclose subclinical complications. While the number of patients biopsied is still too small to provide definite conclusions , it appears that this technique is safe, similar and has a very high yield of excellent specimens. In addition, the needle offers the advantage of being disposable and easy to use by a single operator. 相似文献
67.
68.
69.
The oxygen consumption rate (o.c.r.) of post-rigor beef muscle, unlike the pre-rigor o.c.r., is virtually unaffected by the degree of comminution of the muscle. It has a constant enthalpy of activation (ΔH*) of 18.2 ± 0.3 kcal/mol, which is nearly double the value for pre-rigor muscle and is close to the enthalpy of activation of the mitochondrial NAD+-linked oxidation of pyruvate (~19 kcal/mol). The latter mitochondrial rate (m.r.) appears to be the step which determines the post-rigor o.c.r., unlike the pre-rigor state where the rate of turnover of ATP (a.t.r.) is rate-determining, except below 15 °C. This is because the potential post-rigor a.t.r. is too high for the mitochondrial electron-transport chain to keep pace with it under the prevailing conditions of low pH. The post-rigor o.c.r. can be doubled at all times of storage up to 6 weeks by addition of an ATP supplement. The o.c.r. declines exponentially from the second day of storage onwards and reaches about 10% of its initial level after about 6 weeks storage of the muscle at 2 °C. This is shown to parallel the decline in the m.r. on storage and is evidently due to partly irreversible impairment of mitochondrial function and not to loss of NAD+. The respiratory quotient (r.q.) in the post-rigor state is 1.0 at low pH and falls to ~0.5 on raising the pH to 7.2, due to initial production and subsequent oxidation of α-glycerol phosphate and pyruvate in equal amounts. There are species differences in the magnitude of the post-rigor o.c.r., possibly due to differing mitochondrial contents. The exponential decay of the o.c.r. during storage goes far to explain the increasing depth of penetration of the oxymyoglobin layer which forms on exposing a surface of meat to air or oxygen and which gives the exposed meat an attractive bright red appearance. 相似文献
70.