全文获取类型
收费全文 | 1315篇 |
免费 | 3篇 |
国内免费 | 1篇 |
专业分类
化学工业 | 4篇 |
金属工艺 | 1篇 |
矿业工程 | 1篇 |
能源动力 | 1篇 |
轻工业 | 1篇 |
水利工程 | 6篇 |
石油天然气 | 1篇 |
无线电 | 3篇 |
冶金工业 | 1297篇 |
自动化技术 | 4篇 |
出版年
2017年 | 2篇 |
2015年 | 1篇 |
2013年 | 2篇 |
2008年 | 1篇 |
2004年 | 1篇 |
2003年 | 2篇 |
2002年 | 1篇 |
2000年 | 1篇 |
1999年 | 44篇 |
1998年 | 361篇 |
1997年 | 202篇 |
1996年 | 141篇 |
1995年 | 76篇 |
1994年 | 70篇 |
1993年 | 76篇 |
1992年 | 11篇 |
1991年 | 17篇 |
1990年 | 19篇 |
1989年 | 23篇 |
1988年 | 23篇 |
1987年 | 31篇 |
1986年 | 17篇 |
1985年 | 14篇 |
1983年 | 1篇 |
1982年 | 11篇 |
1981年 | 9篇 |
1980年 | 22篇 |
1979年 | 2篇 |
1978年 | 7篇 |
1977年 | 25篇 |
1976年 | 101篇 |
1975年 | 3篇 |
1955年 | 2篇 |
排序方式: 共有1319条查询结果,搜索用时 15 毫秒
81.
82.
83.
DC Thomas KC Butler LP Taylor P Le Blanc BP Griffith RL Kormos HS Borovetz P Litwak MV Kameneva S Choi GW Burgreen WR Wagner Z Wu JF Antaki 《Canadian Metallurgical Quarterly》1997,43(5):M564-M566
Nimbus and the University of Pittsburgh (UOP) have continued the development of a totally implanted axial flow blood pump under the National Institutes of Health (NIH) Innovative Ventricular Assist System (IVAS) program. This 62 cc device has an overall length of 84 mm and an outer diameter of 34.5 mm. The inner diameter of the blood pump is 12 mm. It is being designed to be a totally implanted permanent device. A key achievement during the past year was the completion of the Model 2 pump design. Ten of these pumps have been fabricated and are being used to conduct in vitro and in vivo experiments to evaluate the performance of different materials and hydraulic components. Efforts for optimizing the closed loop speed control have continued using mathematical modeling, computer simulations, and in vitro and in vivo testing. New hydraulic blade designs have been tested using computational fluid dynamics (CFD) and flow visualization. A second generation motor was designed with improved efficiency. To support the new motor, a new motor controller fabricated as a surface mount PC board has been completed. The program is now operating under a formal QA system. 相似文献
84.
KB Kirkland TB Klimko RA Meriwether M Schriefer M Levin J Levine WR Mac Kenzie DT Dennis 《Canadian Metallurgical Quarterly》1997,157(22):2635-2641
BACKGROUND: Borrelia burgdorferi, the causative agent of Lyme disease, has never been isolated from a patient thought to have acquired Lyme disease in any southeastern state. OBJECTIVE: To investigate 14 cases of an erythema migrans (EM)-like rash illness that occurred during 2 summers at an outdoor camp in central North Carolina in an effort to determine the etiologic, epidemiological, and clinical aspects of this illness. METHODS: Using active surveillance, we identified cases of clinically diagnosed EM in residents and staff of the camp. We collected clinical and demographic information; history of exposure to ticks; acute and convalescent serum antibodies to B. burgdorferi, Rickettsia rickettsii, and Ehrlichia chaffeensis; and cultures for spirochetes from biopsy specimens of skin lesions. Serum samples from a group of residents and staff who did not develop rashes were tested for the same antibodies. We speciated ticks removed from people and collected from vegetation. RESULTS: We identified 14 cases of EM-like rash illness during the 2 summers. Of the 14 case-patients, 10 had associated mild systemic symptoms and 1 had documented fever. All 14 case-patients had removed attached ticks, and 8 remembered having removed a tick from the site where the rash developed a median of 12 days earlier (range, 2-21 days). One tick removed from the site where a rash later developed was identified as Amblyomma americanum, the Lone Star tick; 97% of ticks collected from vegetation and 95% of ticks removed from people were A. americanum. No spirochetes were isolated from skin biopsy specimens. Paired serum samples from 13 case-patients did not show diagnostic antibody responses to B. burgdorferi or other tick-borne pathogens. CONCLUSIONS: This investigation suggests the existence of a new tick-associated rash illness. We suspect that the disease agent is carried by A. americanum ticks. In the southern United States, EM-like rash illness should no longer be considered definitive evidence of early Lyme disease. 相似文献
85.
LA Randoll WR Wilson MS Weaver K Spuhler-Phillips SW Leslie 《Canadian Metallurgical Quarterly》1996,20(2):197-200
To determine what effect ovariectomy and the accompanying sudden loss of circulating gonadal hormones has on spatial learning performance in the adult rat, two groups of rats were tested on the Lashley III simple alley maze following surgery. Ovariectomized animals were compared with a control group of animals that underwent laparotomy at the same time. The ovariectomized group evidenced superior performance on the maze task, as measured by latency to reach goal (running times) and error scores. It is suggested that this finding provides further evidence for the role of gonadal steroid hormones in the manipulation of functions related to learning and memory, especially in the hippocampus. 相似文献
86.
The subunits that make up the capsid of a double-stranded DNA phage have been found to be arranged as covalently bonded, interlinked pentamer and hexamer rings. This remarkable 'chainmail' arrangement raises interesting new questions about macromolecular assembly. 相似文献
87.
88.
TP Le LW Church G Corradin RL Hunter Y Charoenvit R Wang P de la Vega J Sacci WR Ballou N Kolodny S Kitov GM Glenn RL Richards CR Alving SL Hoffman 《Canadian Metallurgical Quarterly》1998,16(2-3):305-312
Only low antibody levels were obtained from vaccinating human volunteers with single-chain peptide from the Plasmodium falciparum circumsporozoite protein (PfCSP). This resulted in modest protection against sporozoite challenge. In addition, HLA restriction limits the probability of synthesis of a vaccine effective for a diverse population. We report immunization studies with a multiple antigen peptide (MAP) system consisting of multiple copies of a B-cell epitope from the central repeat region of the PfCSP in combination with a universal T-cell epitope, the P2P30 portion of tetanus toxin. This MAP4(NANP)6P2P30 vaccine was highly immunogenic in four different strains of mice when used with various safe and nontoxic adjuvants. When this MAP vaccine was encapsulated in liposomes with lipid A and adsorbed to aluminium hydroxide and given three times at 4-week intervals, the resultant antibody prevented 100% of sporozoites from invading and developing into liver stage infection. This high degree of immunogenicity of MAP4(NANP)6P2P30 vaccine formulated in liposomes, lipid A and aluminum hydroxide provides the foundation for consideration of human trials with this formulation. 相似文献
89.
J Kelly R Wolin M Connolly A Afonso L James P Kirshmeier WR Bishop AT McPhail 《Canadian Metallurgical Quarterly》1998,6(6):673-686
Blocking farnesylation of oncogenic Ras proteins is a mechanism based therapeutic approach that is of current interest for the development of antitumor agents to treat ras associated tumors. As part of a SAR study on the lead farnesyl protein transferase (FPT) inhibitor I, we report here the synthesis of novel geometric isomers II and III and the FPT inhibition activity of their N-acyl and N-sulfonamido derivatives 15-65. The N-acyl derivatives are markedly less active than the lead inhibitor I thereby demonstrating that the spatial location of the N-acyl group in I is critical for binding of the compound to FPT. In contrast to I, the N-sulfonamido-II series is a novel lead of non-sulfhydryl, nonpeptidic compounds that are dual FPT/GGPT inhibitors. In light of recent reports on the alternative prenylation of N- and K-Ras, dual FPT/GGPT inhibitors may be required to control cell proliferation in tumors containing activated Ras. 相似文献
90.
M Perrotti F Rabbani P Russo MC Solomon WR Fair 《Canadian Metallurgical Quarterly》1998,52(1):106-110
Postgastrectomy osteopenia is observed generally in humans. Fructooligosaccharides increase the absorption of calcium from the large intestine of healthy rats. Thus, we have examined whether they stimulate calcium absorption and prevent osteopenia in rats following total gastrectomy. Rats were subjected to either a sham surgical operation or Billoth II gastrectomy. Seven rats from each surgical treatment group were fed a control diet, and another seven rats of each treatment group were fed a diet containing fructooligosaccharides (75 g/kg diet) for 4 wk. For 5 d each week, feces were collected, and the calcium and phosphorus contents were measured for calculation of the absorption of these minerals. At the end of the experiment, the rats were killed and bones were collected. The net calcium absorption, calcium content and bone mineral density of the femur and tibia in gastrectomized rats fed the control diet were significantly less than those in sham-operated rats fed control diet. The net calcium absorption in rats fed the fructooligosaccharides diet was greater than that in rats fed control diet. Moreover, dietary fructooligosaccharides prevented the decrease in the calcium content and bone mineral density in gastrectomized rats. Dietary fructooligosaccharides enhanced calcium absorption and prevented the changes indicative of postgastrectomy osteopenia such as decreases in bone calcium content and bone mineral density in gastrectomized rats. 相似文献