全文获取类型
收费全文 | 2124篇 |
免费 | 16篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 5篇 |
综合类 | 3篇 |
化学工业 | 95篇 |
金属工艺 | 7篇 |
机械仪表 | 11篇 |
建筑科学 | 20篇 |
矿业工程 | 1篇 |
能源动力 | 8篇 |
轻工业 | 71篇 |
水利工程 | 5篇 |
石油天然气 | 5篇 |
武器工业 | 1篇 |
无线电 | 78篇 |
一般工业技术 | 85篇 |
冶金工业 | 1669篇 |
自动化技术 | 79篇 |
出版年
2021年 | 12篇 |
2020年 | 5篇 |
2019年 | 6篇 |
2018年 | 13篇 |
2016年 | 6篇 |
2015年 | 6篇 |
2014年 | 8篇 |
2013年 | 24篇 |
2012年 | 16篇 |
2011年 | 23篇 |
2010年 | 15篇 |
2009年 | 17篇 |
2008年 | 24篇 |
2007年 | 22篇 |
2006年 | 14篇 |
2005年 | 18篇 |
2004年 | 23篇 |
2003年 | 21篇 |
2002年 | 19篇 |
2001年 | 14篇 |
2000年 | 12篇 |
1999年 | 59篇 |
1998年 | 506篇 |
1997年 | 293篇 |
1996年 | 169篇 |
1995年 | 98篇 |
1994年 | 90篇 |
1993年 | 96篇 |
1992年 | 21篇 |
1991年 | 34篇 |
1990年 | 37篇 |
1989年 | 31篇 |
1988年 | 31篇 |
1987年 | 19篇 |
1986年 | 27篇 |
1985年 | 25篇 |
1984年 | 12篇 |
1983年 | 8篇 |
1982年 | 15篇 |
1981年 | 23篇 |
1980年 | 15篇 |
1979年 | 12篇 |
1978年 | 9篇 |
1977年 | 41篇 |
1976年 | 109篇 |
1975年 | 10篇 |
1974年 | 4篇 |
1973年 | 10篇 |
1969年 | 3篇 |
1967年 | 3篇 |
排序方式: 共有2143条查询结果,搜索用时 46 毫秒
911.
912.
Hemolytic anemia associated with lead poisoning from shotgun pellets and the response to Succimer treatment 总被引:1,自引:0,他引:1
MH Aly HC Kim SW Renner A Boyarsky M Kosmin DE Paglia 《Canadian Metallurgical Quarterly》1993,44(4):280-283
The recent development of mini-invasive surgery includes appendectomy. We report our results of 4 years experience in this type of approach. We have operated on 154 patients (61 men, 93 women), mean age 26.7 years, presenting with clinical signs of appendicitis. The operation was completely carried out by laparoscopy in 144 cases, including treatment of abscess in 13 and peritonitis in 8 cases. Operation was converted into laparotomy in 10 cases, 4 of which because of some difficulty in appendix dissection. No deaths were recorded. Eight (5.2%) post-operative complications occurred: 4 infections of the trocar hole, one of which the cause of readmission; 3 cases of pain and fever (in one a re-laparoscopy was performed because of suspicion of leakage of the appendicular stump); 1 residual hematoma requiring second laparoscopy. Mean duration of hospitalisation was 4.9 days (range 2-25 days): at present, mean hospitalisation is 2 and 6 days respectively in cases with and without peritonitis. In conclusion, laparoscopic appendectomy appears to be feasible in the majority of cases, with better results when the appendix is ectopic and/or in the presence of peritoneal reaction. 相似文献
913.
HC Nyholm AL Nielsen J Lyndrup A Dreisler SM Thorpe 《Canadian Metallurgical Quarterly》1993,12(3):246-252
In 159 endometrial carcinomas, estrogen (ER) and progesterone receptors (PR) were determined biochemically by dextran-coated charcoal (DCC) assay and immunohistochemically (ICA) on frozen sections. ICA receptor content was estimated by a total histologic score (HSCORE), including all tissue components, and by a cancer HSCORE, including malignant cells only. These scores were closely correlated. A single biopsy was found to be representative for each tumor. ER-DCC status was positive in 90.3% and PR-DCC status in 92.2% of the tumors. ER total HSCORE was positive in 47% and PR total HSCORE in 89% of tumors. ER and PR correlated inversely with tumor grade (p < 0.001). Correlations were found between ER and PR content determined by either method (DCC: r = 0.77; ICA: r = 0.50), as well as between DCC and ICA content (ER: r = 0.52; PR: r = 0.76). The association between DCC and ICA was affected by the tumor grade: the DCC values decreased relatively more than total HSCOREs with increasing grade. The sensitivity of ICA against DCC assay was 56% for ER and 86% for PR. Maximal agreement between receptor status as determined by ICA and by DCC would result from a DCC cutoff level of 130 fmol/mg for ER and 114 fmol/mg for PR. 相似文献
914.
JB Ubbink WJ Vermaak A van der Merwe PJ Becker R Delport HC Potgieter 《Canadian Metallurgical Quarterly》1994,124(10):1927-1933
We have previously shown that a modest vitamin supplement containing folic acid, vitamin B-12 and vitamin B-6 is effective in reducing elevated plasma homocysteine concentrations. The effect of supplementation of the individual vitamins on moderate hyperhomocysteinemia has now been investigated in a placebo-controlled study. One hundred men with hyperhomocysteinemia were randomly assigned to five groups and treated with a daily dose of placebo, folic acid (0.65 mg), vitamin B-12 (0.4 mg), vitamin B-6 (10 mg) or a combination of the three vitamins for 6 wk. Folic acid supplementation reduced plasma homocysteine concentrations by 41.7% (P < 0.001), whereas the daily vitamin B-12 supplement lowered homocysteine concentrations by 14.8% (P < 0.01). The daily pyridoxine dose did not reduce significantly plasma homocysteine concentrations. The combination of the three vitamins reduced circulating homocysteine concentrations by 49.8%, which was not significantly different (P = 0.48) from the reduction achieved by folate supplementation alone. Our results indicate that folate deficiency may be an important cause of hyperhomocysteinemia in the general population. 相似文献
915.
916.
Motor vehicle accident survivors (n?=?92) were assessed for acute stress disorder (ASD) within 1 month of the trauma and reassessed (n?=?71) for posttraumatic stress disorder (PTSD) 6 months posttrauma. ASD was diagnosed in 13% of participants, and a further 21% had subclinical levels of ASD. At follow-up, 78% of ASD participants and 60% of subclinical ASD participants met criteria for PTSD. The strong predictive power of acute numbing, depersonalization, a sense of reliving the trauma, and motor restlessness, in contrast to the low to moderate predictive power of other symptoms, indicates that only a subset of ASD symptoms is strongly related to the development of chronic PTSD. Although these findings support the use of the ASD diagnosis, they suggest that the dissociative and arousal clusters may require revision. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
917.
Follicular dendritic cell tumors are uncommon, and all the reported cases have occurred as primary lymph node tumors. We report two cases in the oral cavity, one in the soft palate and one in the tonsil. The tumors were characterized by sheets, whorls, and storiform arrays of spindly and syncytial-appearing cells with oval nuclei, fine chromatin, distinct nucleoli, and occasional nuclear pseudoinclusions. Multinucleated forms were present and were prominent in one case. An unusual feature was the presence of irregular pseudovascular spaces, which could raise a concern for vascular neoplasm. Because the tumors showed cohesive growth and a sharp interface with the fibrous stroma, they could also be mistaken for carcinoma, sarcoma, or melanoma. After radiation therapy, the palatal tumor showed a greater degree of nuclear pleomorphism, numerous nuclear pseudoinclusions, and striking nuclear grooving and foldings, mimicking interdigitating reticulum cell tumors. The diagnosis in both cases was confirmed by immunoreactivity with CD21 and CD35 and by ultrastructural demonstration of interdigitating cell processes with desmosomes. Both tumors also showed unexpected immunoreactivity with muscle-specific actin. Follicular dendritic cell tumor merits wider recognition of its possible extranodal occurrence as well as its full morphological spectrum in order to better define its behavior. 相似文献
918.
919.
Ulcerative colitis (UC) is a chronic relapsing inflammatory bowel disease (IBD) showing immunologic abnormalities and association with autoimmune states (Snook et al., 1989). Extraintestinal manifestation of UC affect various organ systems (Podolsky, 1991). We describe morphologically documented encephalomyeloneuritis in a 58-year-old white male with UC in full remission providing support for the concept that ulcerative colitis may be complicated by neurologic manifestations affecting both the central and peripheral nervous system. 相似文献
920.
Our study was to assess whether there were differential effects of nasal continuous positive airway pressure (nCPAP) on different kinds of obstruction in either upper or lower airways in patients with chronic obstructive pulmonary disease (COPD). nCPAP (6 cmH2O for ten minutes) was applied to 7 patients with reversible extrathoracic upper airway obstruction (RUAO) and 3 patients with fixed extrathoracic upper airway obstruction (FUAO). Eighteen stable asthmatics, receiving methacholine challenge to induce a more than 20% reduction in FEV1, were randomly investigated for the effect of nCPAP or sham pressure on reversible lower airway obstruction. Nine stable COPD patients were enrolled to study the effect on irreversible lower airway obstruction. Maximal expiratory and inspiratory flow volume curves and dyspnoea scores were obtained before and after immediate withdrawal of nCPAP. In the RUAO group, nCPAP significantly improved stridor and dyspnoea scores, decreased the ratio of FEF50/FIF50 from 2.05 +/- 0.25 to 1.42 +/- 0.16, and increased peak inspiratory flow (PIF) as well as forced inspiratory vital capacity by 26 +/- 8% and 9 +/- 4%, respectively. In expiratory phase, there was no significant change in pulmonary functions. In asthmatics, nCPAP significantly reversed methacholine-induced bronchoconstriction increasing forced vital capacity by 10 +/- 3%, FEV1 by 15 +/- 4% and PIF by 32 +/- 11%. nCPAP significantly increased the response to bronchodilators. The improvement in airflow rate persisted for at least 5 min after nCPAP withdrawal and was highly correlated with the response to bronchodilators. There was no significant effect of nCPAP on airflow rate in COPD patients. Subjective dyspnoea score changes paralleled the pulmonary function improvement. We conclude that there are differential effects of nCPAP on airflow rates in patients with different nature of airway obstruction. Patients with airway obstruction caused by structural changes may not benefit from the use of nCPAP in improving airflow rates. 相似文献