全文获取类型
收费全文 | 1435篇 |
免费 | 1篇 |
国内免费 | 1篇 |
专业分类
化学工业 | 7篇 |
金属工艺 | 1篇 |
轻工业 | 1篇 |
无线电 | 1篇 |
一般工业技术 | 2篇 |
冶金工业 | 1421篇 |
原子能技术 | 2篇 |
自动化技术 | 2篇 |
出版年
2023年 | 1篇 |
2018年 | 1篇 |
2006年 | 3篇 |
2004年 | 1篇 |
2003年 | 4篇 |
2002年 | 1篇 |
2000年 | 1篇 |
1999年 | 42篇 |
1998年 | 474篇 |
1997年 | 261篇 |
1996年 | 170篇 |
1995年 | 87篇 |
1994年 | 74篇 |
1993年 | 88篇 |
1992年 | 9篇 |
1991年 | 15篇 |
1990年 | 12篇 |
1989年 | 21篇 |
1988年 | 9篇 |
1987年 | 9篇 |
1986年 | 10篇 |
1985年 | 8篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 8篇 |
1980年 | 8篇 |
1979年 | 1篇 |
1978年 | 4篇 |
1977年 | 23篇 |
1976年 | 81篇 |
1975年 | 4篇 |
1955年 | 1篇 |
排序方式: 共有1437条查询结果,搜索用时 142 毫秒
131.
A Pizziol V Tikhonoff CD Paleari E Russo A Mazza G Ginocchio C Onesto L Pavan E Casiglia AC Pessina 《Canadian Metallurgical Quarterly》1998,52(11):846-849
BACKGROUND: Leishmaniasis recidiva cutis (LRC) is rare in New World leishmaniasis. Only seven cases have been reported so far. MATERIALS AND METHODS: Four cases are reported here. Parasite diagnosis was performed by classical methods of touch preparations, histopathologic sections, and cultures. In addition, the detection of parasite DNA by the polymerase chain reaction (PCR) was performed in all cases. RESULTS: Parasites were detected by at least one of the classical methods in all primary lesions; however, only the PCR was positive in the recidivant lesions. DISCUSSION: LRC cases most likely represent a reactivation of an initial infection, probably due to the persistence of parasites in scarred tissue. Although lupoid leishmaniasis (LL) has been used as a synonym of LRC, a clear difference between LRC and LL can be defined as LL is the initial clinical presentation while LRC is a recurrent lesion. CONCLUSIONS: The results indicate that it is not appropriate to use these two denominations as synonyms. The designation of LRC should be maintained in order to define recidives occurring at the border of an old scar of cutaneous leishmaniasis, avoiding the confusion with the lupoid form of the disease. 相似文献
132.
STUDY OBJECTIVE: To evaluate the cross-reactivity of dapsone after a documented hypersensitivity reaction to trimethoprim-sulfamethoxazole (TMP-SMX) during prophylaxis for Pneumocystis carinii pneumonia. DESIGN: Retrospective, chart review, cohort study. SETTING: Two university-affiliated teaching hospitals. PATIENTS: Sixty patients infected with the human immunodeficiency virus. MEASUREMENTS AND MAIN RESULTS: Thirteen patients (21.7%) had cross-reactivity to dapsone after the reaction to TMP-SMX. No significant risk factors for this response were identified. Most reactions were of mild or moderate severity and rated as possibly or probably caused by one of the agents. Of the 13 patients, 4 (30.8%) continued therapy. CONCLUSIONS: Although cross-reactivity can occur, dapsone may be considered in patients with mild hypersensitivity reactions to TMP-SMX. 相似文献
133.
Blocked signal transduction to the ERK and JNK protein kinases in anergic CD4+ T cells 总被引:1,自引:0,他引:1
T cells activated by antigen receptor stimulation in the absence of accessory cell-derived costimulatory signals lose the capacity to synthesize the growth factor interleukin-2 (IL-2), a state called clonal anergy. An analysis of CD3- and CD28-induced signal transduction revealed reduced ERK and JNK enzyme activities in murine anergic T cells. The amounts of ERK and JNK proteins were unchanged, and the kinases could be fully activated in the presence of phorbol 12-myristate 13-acetate. Dephosphorylation of the calcineurin substrate NFATp (preexisting nuclear factor of activated T cells) also remained inducible. These results suggest that a specific block in the activation of ERK and JNK contributes to defective IL-2 production in clonal anergy. 相似文献
134.
PC Fletcher PJ McKenna CD Frith PM Grasby KJ Friston RJ Dolan 《Canadian Metallurgical Quarterly》1998,55(11):1001-1008
BACKGROUND: Functional neuroimaging experiments have implicated prefrontal cortex (PFC) in memory processes. Several studies of schizophrenic patients have shown failure of activation in the dorsolateral region of PFC (DLPFC). We used a graded memory challenge to characterize functional neuroanatomical differences between schizophrenic and control subjects. The graded manipulation of task demands enabled us to assess group differences in the context of normal and abnormal psychological task performance. METHODS: Memory-related activity was assessed using positron emission tomography in schizophrenic patients and age-matched controls during performance of a graded memory task. Subjects underwent scanning while learning and recalling word lists of variable length. RESULTS: We used a model that assessed linear and nonlinear effects of memory load. Nonlinear group differences in DLPFC activation were observed. Controls showed a steepening slope of DLPFC increase as task demands increased. By contrast, schizophrenic subjects showed initial DLPFC increases that fell away with increasing memory load. The DLPFC response in schizophrenic subjects was closely related to measured task performance. In addition, schizophrenic subjects failed to show task-related decreases in activity in the left superior temporal and inferior parietal gyrus. CONCLUSIONS: Patients with schizophrenia showed a failure in DLPFC activation only in the face of diminished performance measures, suggesting that a full characterization of task-related changes in DLPFC activation must consider performance levels. However, striking failures of deactivation in superior temporal and inferior parietal regions were independent of task performance, possibly reflecting a core abnormality of the condition. 相似文献
135.
The clinical features and family histories of 20 adults with dyskinetic cerebral palsy from 20 families were studied. The majority of the patients showed progressive neurological deterioration in adult life. In only three did the condition stabilise by 10 years of age and in seven there was deterioration after the age of 30. Two patients developed a secondary cervical spondylotic myelopathy. Four patients had affected relatives and there were similar proportions of affected parents and siblings. The family data suggest genetic heterogeneity with autosomal recessive and dominant variants. The existence of an X-linked form cannot be excluded, and the demonstration of an increased paternal age effect among single cases suggests that some of these may arise because of fresh dominant genetic mutation. 相似文献
136.
137.
138.
Forty-five patients with social phobia and 15 individuals with no mental disorder were compared on number and type of life events experienced. Social phobia patients were further examined to evaluate the effect of negative life events and of the interaction between personality style and life events on severity of impairment and reactions to cognitive-behavioral group therapy. Patients with social phobia reported more negative life events than participants with no mental disorder. Among patients with social phobia, more frequent negative life events were associated with higher scores on measures of depression and general anxiety. Patients high on autonomy who reported more negative autonomous (i.e., achievement-oriented) life events also scored higher on measures of social anxiety and general anxiety. There were no significant interactions between sociotropy and the frequency of reported socially oriented negative life events. However, patients high on sociotropy scored higher on measures of social anxiety, depression, and general anxiety. Patients who had experienced more negative life events improved more after treatment on measures of social anxiety than did those who had experienced fewer negative life events. Implications of these findings and recommendations for future research are discussed. 相似文献
139.
140.
To clarify the relationship between selenium (Se) deficiency and functional disorders, the authors determined the Se concentration, anti-oxidant enzyme activity, and other parameters in rats fed a Se-deficient diet. Rats fed the Se-deficient diet showed a decrease in Se concentration and glutathione peroxidase (GSH-Px) activity in plasma, erythrocytes, heart, liver, and skeletal muscle from the first week after the initiation of the diet, an increase in heart lipid peroxide concentration from the second week, and an increase in liver glutathione S-transferase activity from the fourth week. From the twelfth week, a decrease in the growth rate in the rats fed the Se-deficient diet was observed. In spite of this growth impairment, no changes in electrocardiogram, muscle tone, degree of hemolysis, plasma biochemistry, or hematological values were detected. In summary, the authors found that a reduction of body Se is easily induced, but that the appearance of functional disorders following Se deficiency is difficult to detect in rats. 相似文献