全文获取类型
收费全文 | 5742篇 |
免费 | 4篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 1篇 |
化学工业 | 68篇 |
金属工艺 | 5篇 |
机械仪表 | 5篇 |
建筑科学 | 13篇 |
能源动力 | 2篇 |
轻工业 | 33篇 |
水利工程 | 1篇 |
无线电 | 31篇 |
一般工业技术 | 39篇 |
冶金工业 | 5506篇 |
原子能技术 | 5篇 |
自动化技术 | 38篇 |
出版年
2018年 | 5篇 |
2014年 | 4篇 |
2013年 | 9篇 |
2012年 | 7篇 |
2011年 | 13篇 |
2010年 | 5篇 |
2009年 | 7篇 |
2008年 | 11篇 |
2007年 | 11篇 |
2006年 | 14篇 |
2005年 | 11篇 |
2004年 | 11篇 |
2003年 | 14篇 |
2002年 | 9篇 |
2001年 | 6篇 |
2000年 | 8篇 |
1999年 | 165篇 |
1998年 | 1680篇 |
1997年 | 913篇 |
1996年 | 651篇 |
1995年 | 335篇 |
1994年 | 324篇 |
1993年 | 339篇 |
1992年 | 41篇 |
1991年 | 57篇 |
1990年 | 80篇 |
1989年 | 68篇 |
1988年 | 65篇 |
1987年 | 85篇 |
1986年 | 59篇 |
1985年 | 58篇 |
1984年 | 3篇 |
1983年 | 14篇 |
1982年 | 32篇 |
1981年 | 35篇 |
1980年 | 39篇 |
1979年 | 7篇 |
1978年 | 10篇 |
1977年 | 146篇 |
1976年 | 340篇 |
1975年 | 12篇 |
1974年 | 2篇 |
1972年 | 2篇 |
1971年 | 2篇 |
1965年 | 2篇 |
1955年 | 5篇 |
1942年 | 6篇 |
1941年 | 2篇 |
1940年 | 2篇 |
1936年 | 2篇 |
排序方式: 共有5747条查询结果,搜索用时 15 毫秒
991.
Eighteen spring-born Columbia ram, wether, and zeranol-implanted ram lambs were studied to determine the influence of castration or zeranol implants on intramuscular collagen (IMC) properties and muscle shear force values. Warner-Bratzler shear force values for longissimus muscle were greatest for ram lambs, intermediate for implanted rams, and least for wethers (P < .05). Nonreducible collagen crosslink concentration was greater in IMC of rams and implanted rams (P < .05). The IMC from rams compared with that from wethers contained proportionately more Type III than Type I collagen (P < .05); values for implanted rams were intermediate. Heat-soluble muscle collagen concentration was greater for rams and implanted rams than for wethers (P < .05); however, insoluble collagen concentration did not differ by treatment. Muscle collagen concentrations were not different for rams, wethers, or implanted rams. Increased shear force values in rams were associated with elevated collagen crosslink concentration and increased proportion of Type III collagen. Greater concentration of soluble collagen in ram IMC neither diminished nor diluted IMC crosslinking. The proportion of heat-labile collagen in the fractions did not reflect the IMC crosslinking profile for ram and wether lambs. Zeranol implantation modified IMC characteristics of rams such that shear force values and some collagen properties were similar to those of wethers. 相似文献
992.
PURPOSE: To quantify the workload of residents on night call and to determine the residents' perceptions of the balance between service and education in their night-call activities. METHOD: Twenty-two internal medicine residents--nine first-year residents and 13 senior residents (i.e., in their second, third, or fourth year)--kept logs of their night-call activities for two periods of 16 days each in 1991-92, at a 772-bed teaching hospital affiliated with Wright State University School of Medicine. The residents used the following five-point scale to rate each activity: 1, strictly service; 3, even balance; 5, strictly education. They also recorded the total times spent on various activities. Data were analyzed by using the independent and paired t-tests. RESULTS: Ninety-eight percent of the logs were returned. The first-year and senior residents did not differ significantly in times spent on logged events. Both the first-year and the senior residents perceived many night-call activities to be weighted toward education, especially those involving evaluation of acutely ill patients being considered for hospital admission (overall mean rating of 3.3). There was no striking difference between the first-year and senior residents' perceptions of the balance between service and education in their activities. CONCLUSION: The residents' perceptions of the relationship between service and education indicate that there was an even balance between the two. The educational aspects of night-call duties can and should remain an integral part of residents' training. 相似文献
993.
RJ Jaszczak DR Gilland MW Hanson S Jang KL Greer RE Coleman 《Canadian Metallurgical Quarterly》1993,34(9):1577-1586
We describe a technique using a line source and a rotatable air-copper-lead assembly to acquire gamma transmission computed tomographic (TCT) data for determining attenuation maps to compensate SPECT emission scans. The technique minimizes problems associated with discriminating 99mTc transmission and 201Tl emission photons and requires only a modest increase in total study time. A 99mTc line source and a stacked foil ("multislat") collimator are placed near the focal line of a fan-beam collimator (114 cm focal length) mounted on one detector of a triple-camera SPECT system. We acquired TCT data of plastic rod and anthropomorphic thorax phantoms to investigate the capability of the line source and rotatable air-copper-lead attenuators to determine attenuation maps. The data were acquired with and without 5.4 MBq (145 microCi) of 201Tl placed in the myocardial chamber of the thorax phantom. Phantoms also were scanned using a curved transmission slab source mounted to a parallel-hole collimator. Fan-beam TCT images have improved resolution compared with parallel-beam TCT images. Two patient scans also were performed to evaluate the clinical usefulness of fan-beam TCT. The rotatable air-copper-lead attenuator method eliminates contamination of emission data by transmission photons and reduces spill-over of emission data into the transmission energy window for some cases. Results show the feasibility of using fast, sequential or interlaced transmission scans of a line source within a rotatable air-copper-lead attenuator assembly to obtain accurate attenuation maps for SPECT attenuation compensation. 相似文献
994.
Conducted a survey to explore the relation between the role of supervision and practitioners' experience, training, and certification and to determine how these factors affect quality assurance in university counseling centers. Ss were 185 counselors. Findings indicate that time spent in supervision was not significantly related to the dependent variables of educational level, experience, or licensure, and that unlicensed practitioners were less likely to seek supervision. The lack of supervision and licensed practitioners may be inconsistent with the value placed on supervision as a quality control procedure. (13 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
995.
996.
997.
998.
999.
Serum- and bradykinin-induced calcium transients in familial Alzheimer's fibroblasts 总被引:1,自引:0,他引:1
KR McCoy RD Mullins TG Newcomb GM Ng G Pavlínková RJ Polinsky LE Nee JE Sisken 《Canadian Metallurgical Quarterly》1993,14(5):447-455
The calcium-sensitive photoprotein, aequorin, was used to examine serum- and bradykinin-induced transient increases in free cytosolic calcium ions in skin fibroblasts from 10 individuals with early onset familial AD (FAD), including four who were biopsied before their clinical symptoms would allow a diagnosis of AD, 2 individuals with late onset FAD, 8 at-risk but nonsymptomatic individuals, and 13 controls. The data show that (a) among controls, the peaks of the calcium transients increase in height as a function of donor age; (b) transients induced by 10% serum, 10 nM bradykinin (BK) or 100 nM BK were generally lower in FAD fibroblasts, including those from donors in the early stages of the disease, than in age-matched control cells; (c) such transients are reduced in cells from a proportion of the nonsymptomatic, at-risk individuals. Thus, serum- and BK-induced calcium transients are reduced in fibroblasts from both early and more advanced stage FAD donors and perhaps even from donors who are presymptomatic carriers of the defective gene. The data also suggest that changes in calcium transients in FAD fibroblasts neither mimic nor exaggerate the effects of normal aging. 相似文献
1000.