全文获取类型
收费全文 | 3451篇 |
免费 | 0篇 |
专业分类
化学工业 | 5篇 |
轻工业 | 6篇 |
石油天然气 | 1篇 |
无线电 | 1篇 |
一般工业技术 | 3篇 |
冶金工业 | 3434篇 |
自动化技术 | 1篇 |
出版年
2019年 | 1篇 |
2017年 | 1篇 |
2013年 | 1篇 |
2011年 | 1篇 |
2010年 | 1篇 |
2008年 | 1篇 |
2004年 | 1篇 |
2003年 | 4篇 |
2000年 | 1篇 |
1999年 | 98篇 |
1998年 | 938篇 |
1997年 | 572篇 |
1996年 | 356篇 |
1995年 | 200篇 |
1994年 | 189篇 |
1993年 | 210篇 |
1992年 | 31篇 |
1991年 | 50篇 |
1990年 | 52篇 |
1989年 | 63篇 |
1988年 | 61篇 |
1987年 | 62篇 |
1986年 | 55篇 |
1985年 | 53篇 |
1983年 | 10篇 |
1982年 | 20篇 |
1981年 | 24篇 |
1980年 | 36篇 |
1979年 | 3篇 |
1978年 | 13篇 |
1977年 | 105篇 |
1976年 | 225篇 |
1975年 | 10篇 |
1955年 | 3篇 |
排序方式: 共有3451条查询结果,搜索用时 15 毫秒
31.
32.
AM Standeven M Escobar RL Beard YD Yuan RA Chandraratna 《Canadian Metallurgical Quarterly》1997,54(4):517-524
Thirty-nine acrylates and methacrylates that had been used in dental resin materials were evaluated by a cytotoxicity test, and the relationships between their structures and cytotoxicity were studied to predict cytotoxic levels of dental resin materials in order to develop new low-toxic resin materials. All the acrylates evaluated were more toxic than corresponding methacrylates. In both the acrylates and methacrylates, a hydroxyl group seemed to enhance cytotoxicity. Dimethacrylates with 14 or fewer oxyethylene chains showed similar cytotoxicity while dimethacrylates with 23 oxyethylene chains showed lower cytotoxicity. The cytotoxicity ranking of monomers widely used in dental resin materials was bisphenol A bis 2-hydroxypropyl methacrylate (bisGMA) > urethane dimethacrylate (UDMA) > triethyleneglycol dimethacrylate (3G) > 2-hydroxyethyl methacrylate (HEMA) > methyl methacrylate (MMA). In acrylates, methacrylates, and ethylmethacrylates with either substituents, the lipophilicity of substituents affected their cytotoxicity, and an inverse correlation between IC50 and logP was observed. These results will be useful in developing new resin materials with low toxic monomer compositions. 相似文献
33.
We studied six patients (twelve upper extremities) who had quadriplegia at the sixth cervical level. Our purpose was to evaluate how the loss of terminal extension of the elbow adversely affected the ability of the patient to perform transfers with a sliding board and so-called depression raises (lifting of the body with use of the extended upper extremities to reduce the pressure on the ischial tuberosities). Function of the triceps muscle was considered to be absent in eight upper extremities and present in four. A flexion contracture of the elbow was simulated with use of a specially fabricated, hinged elbow brace. Terminal extension was progressively limited, in 5-degree increments, until the patient was no longer able to perform the transfer or the depression raise. The mean flexion contracture at which the patient could not perform the transfer or the depression raise was approximately 25 degrees when function of the triceps was absent and approximately 50 degrees when function of the triceps was intact. The results of this study emphasize the importance of maintaining the full range of motion of the elbow in a patient who has high-level quadriplegia. In a patient who has quadriplegia at the sixth cervical level who otherwise would be independent with regard to transfer skills and mobility in bed, a flexion contracture of the elbow of approximately 25 degrees or more can result in the loss of a functional level and render the patient as dependent as one who has quadriplegia at the fifth cervical level. 相似文献
34.
The use of linear peptides as antigens for detection of serum antibodies has been studied using a sequence of the Borrelia burgdorferi protein, flagellin, and Lyme disease sera as a model. It was found that a novel presentation of the peptide as a hapten on the carrier protein, bovine serum albumin, in the enzyme-linked immunosorbent assay format can be successfully applied to distinguish between Lyme disease and control sera. 相似文献
35.
The goal of this research was to identify patients' preferences for physician inquiry into various aspects of health status and to examine whether the preconsultation availability of health status data (collected from the SF-36 Health Status Questionnaire) influenced the physician's conduct during the consultation. Results from 58 prenatal patient visits yielded the following findings. First, patients expressed strong preferences for physicians to ask about the patient's perceptions of health in general and about physical dimensions of health status such as pain, vitality, and role limitations due to physical functioning. Patients also were more satisfied when doctors were perceived as having asked about these issues. Second, patients varied considerably in their preferences for physician inquiries into psychosocial issues such as social functioning, mental health, and role limitations due to emotional problems. Approximately half the patients wanted these matters discussed, whereas the remainder either did not care or preferred that doctors not ask about these topics. Third, the preconsultation availability of health status information had little effect on the degree to which physicians asked about the patient's health-related quality of life. Clinical implications are discussed. 相似文献
36.
STUDY OBJECTIVES: To define a set of orthostatic vital signs that minimize the frequency of false-positives among healthy individuals while maximizing sensitivity in detecting acute moderate blood loss and to determine the sensitivity and specificity of this optimized tilt test in detecting acute moderate blood loss. DESIGN AND INTERVENTION: Postural vital signs were recorded in a standardized manner before and after 450-mL phlebotomy. Paired comparisons were done for a variety of criteria for a positive tilt test using receiver-operating characteristic curves. SETTING AND TYPE OF PARTICIPANTS: Three hundred forty-five healthy euvolemic adult volunteer blood donors were tested at three community blood donation centers over a one-year period. Subjects were prospectively divided into group 1 (less than age 65; 301) and group 2 (age 65 or older; 44). MEASUREMENTS AND MAIN RESULTS: For each combination of pulse and blood pressure in group 1, a change in pulse alone had the same or higher sensitivity with at least the same specificity. Pulse alone was similarly superior in group 2 compared with previously published combinations of pulse and blood pressure. Even the optimized tilt test had limited sensitivity in detecting acute moderate blood loss with high specificity. CONCLUSION: In applying the tilt test to young adults without cardiovascular disease, pulse measurement usually is all that is necessary. 相似文献
37.
Radiographic computed tomography and magnetic resonance imaging are the procedures of choice in the diagnosis of patients with suspected pituitary gland abnormalities. Several cases are presented where the diagnostic value of such procedures in patients with diseases affecting the pituitary gland is demonstrated. 相似文献
38.
We established an in vitro model of the phagocytosis of Mycobacterium tuberculosis by human peripheral blood monocytes to evaluate the subsequent inhibition of intracellular replication of the organism. Highly purified T cells (94% CD3(+)/CD16(-)) or natural killer (NK) cells (96% CD16(+)/CD3(-)) isolated by Percoll discontinuous density gradient of peripheral blood mononuclear cells were incubated with M. tuberculosis-infected monocyte monolayers. Monocytes were lysed immediately and at 4, 7, and 10 d after infection for quantification of intracellular replication, which was assessed by quantitative plating techniques as colony-forming units (CFU). Whereas control monocytes permitted intracellular replication, T cells activated monocytes to kill 77% (p < 0.01) of intracellular M. tuberculosis compared with control monocytes by 10 d after infection. NK cells activated monocytes to kill 84% (p < 0.01) of M. tuberculosis in comparison with control monocytes. Lymphokine (IL-2)-activated-killer (LAK) cells were capable of activating monocytes to kill 97% (p < 0.01) of the intracellular organisms compared with control monocytes. In purified protein derivative (PPD)-positive donors, PPD-specific-CD4(+) lymphocytes stimulated monocytes to kill intracellular M. tuberculosis in a Class II major histocompatibility complex-restricted manner. In contrast, in PPD-negative donors, CD4(-) lymphocytes activated monocytes in a genetically unrestricted manner. Both T cell supernatant and NK cell supernatant generated from cocultivation with M. tuberculosis-infected monocytes also activated monocytes to augment mycobactericidal function. In conclusion, T cells, NK cells, LAK cells, and their supernatants activated mycobactericidal function of monocytes, although these pathways of activation differed in terms of antigenic specificity and genetic restriction. 相似文献
39.
Oncocytic lesions of the caruncle and other ocular adnexa 总被引:2,自引:0,他引:2
This is a clinicopathologic study of 18 oncocytic lesions involving the ocular adnexa. These lesions most commonly occur in elderly patients (median age 73), and there is a striking predilection for women. The broad spectrum of lesions included oncocytic adenomatous hyperplasia, oncocytomas, and oncocytic carcinoma. Ten lesions, all of which were oncocytomas, involved the caruncle, four the conjunctiva, and one the mucocutaneous junction of the eyelid. Two tumors involved the lacrimal sac and one the lacrimal gland. A review of the literature disclosed only 17 previously reported oncocytic lesions of the ocular adnexa. A small yellowish-tan or reddish caruncular mass, especially in an elderly woman, should alert the ophthalmologist to consider the possibility of oncocytoma in his differential diagnosis. 相似文献
40.
In the experiment reported in this paper, 22 of 35 neurons in the gustatory NTS were found to respond to odorant as well as taste stimuli. This odorant response was apparently mediated by the ethmoid nerve and at least one other odorant-responsive system, possibly other nasal trigeminal afferents. These gustatory neurons responded to odorants, as they did to taste stimuli, in a manner consistent with an encoding of stimulus quality information. Thus at least some of the neurons of the gustatory NTS carry information concerning several of the senses involved in ingestion. 相似文献