首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2736篇
  免费   18篇
电工技术   7篇
化学工业   116篇
金属工艺   16篇
机械仪表   8篇
建筑科学   9篇
矿业工程   1篇
能源动力   9篇
轻工业   79篇
水利工程   1篇
石油天然气   2篇
无线电   21篇
一般工业技术   115篇
冶金工业   2327篇
原子能技术   5篇
自动化技术   38篇
  2023年   2篇
  2022年   12篇
  2021年   9篇
  2019年   8篇
  2018年   3篇
  2017年   10篇
  2016年   8篇
  2015年   8篇
  2014年   15篇
  2013年   30篇
  2012年   31篇
  2011年   31篇
  2010年   24篇
  2009年   20篇
  2008年   28篇
  2007年   21篇
  2006年   17篇
  2005年   18篇
  2004年   14篇
  2003年   15篇
  2002年   11篇
  2001年   11篇
  2000年   12篇
  1999年   62篇
  1998年   718篇
  1997年   408篇
  1996年   279篇
  1995年   143篇
  1994年   133篇
  1993年   122篇
  1992年   19篇
  1991年   27篇
  1990年   25篇
  1989年   42篇
  1988年   40篇
  1987年   22篇
  1986年   31篇
  1985年   30篇
  1984年   2篇
  1983年   9篇
  1982年   12篇
  1981年   22篇
  1980年   23篇
  1978年   6篇
  1977年   67篇
  1976年   143篇
  1975年   6篇
  1972年   1篇
  1965年   2篇
  1964年   1篇
排序方式: 共有2754条查询结果,搜索用时 11 毫秒
981.
A 76-year-old woman hospitalized for treatment of an inferior vena cava thrombus was noted to have eosinophilia as well as asthma, peripheral neuropathy, jaw claudication and visual loss. Pathological review of a temporal artery biopsy revealed vasculitis with eosinophils but no giant cells. Treatment with high dose corticosteroids resulted in improvement of visual acuity from hand motion to 20/60. Whereas at least 6 cases of temporal artery involvement with Churg-Strauss syndrome have been reported, visual loss has occurred in only 3 patients. In each of these cases, visual loss was permanent.  相似文献   
982.
OBJECTIVE: To test the hypothesis that the anti-apoptotic ability of Epstein-Barr virus (EBV) may result in altered expression of apoptosis-associated proteins in oral hairy leukoplakia (HL), we evaluated HL tissue and normal epithelium for these proteins by immunohistochemistry. MATERIALS AND METHODS: Twenty formalin-fixed, paraffin-embedded specimens of HL lesions and six specimens of normal control mucosa were selected from archived tissue specimens. Bcl-2, Bcl-x, Bax and p53 apoptosis-associated proteins were evaluated in immunohistochemically stained tissue sections according to staining intensity and pattern. The percentage of p53-positive basal cells was estimated in sequential fields. RESULTS: Generally, there were only slight differences in the expression of Bcl-2 and Bcl-x proteins in the epithelium of HL and control tissue. The staining for Bcl-2 was weaker in keratinocytes than in putative melanocytes and Langerhans cells. Equivocal diffuse cytoplasmic staining of prickle cells was also noted. Keratinocytes throughout the epithelium stained positively for Bcl-x protein, although upper layers were more weakly stained. The 'balloon' keratinocytes in HL were infrequently positive for Bcl-x. Bax staining in HL differed from that in control tissue in being more heterogeneous. The staining reaction in HL was weak to negative in upper epithelial levels where 'balloon' keratinocytes were located. Weak to moderate nuclear p53 protein staining was detected in a mean of 25.3% of basal keratinocytes in all but one of the HL specimens; weak staining was seen in only two control specimens. CONCLUSIONS: We found only slight immunohistochemical evidence that expression of the apoptosis-associated proteins is altered in HL. p53 appears to over-expressed in HL; we speculate that this may be related to up-regulation or stabilization of wild-type p53 protein related to EBV infection.  相似文献   
983.
Twenty-three patients with stage IIIb (T4) non-small cell lung cancer received induction chemotherapy (median, 2 cycles) with (n = 12) or without (n = 11) radiation (median, 45 Gy) before operation. Nine tumors involved the carina (n = 8) or lateral tracheal wall (n = 1), 11 were located centrally and invaded the proximal pulmonary artery (n = 6), veins (n = 3), or both (n = 2), three were apical tumors involving T4 structures, and six were associated with histologically diseased mediastinal nodes. Five complete and 18 partial responses were observed after induction treatment. Resection of all residual tumor at the primary site and involved vestiges was possible in 21 patients (91%); in two apical tumors, tumor was left behind. Nine right tracheal sleeve and 11 intrapericardial pneumonectomies and three resections of apical tumors were performed; 11 patients (48%) had radical mediastinal lymph node dissection. Complete sterilization of the primary tumor was observed in 3 patients (13%). Mean operating time was 209.3 +/- 86.8 minutes, and mean blood loss was 896.9 +/- 1031 mL. Major postoperative complications occurred in 6 patients (26%), including hemothorax requiring drainage (n = 1) or reoperation (n = 1), acute distress syndrome (n = 2), and bronchopleural fistula (n = 2), and their incidence was significantly higher (p = 0.0003) among patients receiving induction chemoradiation than among those receiving chemotherapy alone (42 versus 9%). Early (< 1 month) postoperative mortality was 8.6% (n = 2). With a median follow-up of 25 months (range, 12 to more than 39 months), the projected 3-year overall survival was 54%.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
984.
985.
BACKGROUND: In-vivo experimental data indicate that both pre- and postoperative radiotherapy can prevent heterotopic ossification after hip surgery. This comparison was clinically tested in a randomized study. PATIENTS AND METHODS: From June 1992 to September 1993, 84 patients with high risk for the development of heterotopic ossification were randomized. The treatment concept consisted either of preoperative radiotherapy within four hours prior to surgery (arm A) or postoperative radiotherapy within 72 hours following hip surgery (arm B). Preoperative radiotherapy was given in one fraction of 7 Gy, while the postoperative radiotherapy was delivered in five fractions of each 3.5 Gy (total 17.5 Gy). All patient variables (age, sex, prior surgery) and predisposing risk factors were comparable in both treatment arms. For the radiological assessment of heterotopic ossification according to (Brooker-Score) X-rays of the pelvis or hip were evaluated which had been taken immediately pre- and postoperatively as well as at least six months following surgery and prophylactic irradiation. The functional hip status was evaluated pre- and postoperatively using the Harris-Score. Cases in which the Brooker- and/or Harris-Score worsened during the postoperative follow-up as compared to the pre- and immediate postoperative situations were considered as treatment failures. RESULTS: Of 44 patients with at least six months follow-up 41 (93%) experienced a successful prophylaxis. Two failures were observed in the preoperative and one in the postoperative group. The prophylactic efficacy was not influenced if the pre- or postoperative interval was longer than prescribed. All intra- and postoperative complications were comparable for both treatment groups. The mean interval to partial strain (50% body weight) of the operated hip was longer in the preoperative group (mean 19 +/- 27 days) as compared to the postoperative group (mean 8 +/- 13 days). With respect to full strain (100% body weight), the results were equal in both groups. The functional hip status decreased in two patients. Again the mean overall improvement in the postoperative group was larger (mean 42.7 +/- 17.1 points) as compared to the preoperative group (mean 34.3 +/- 13.7 points). CONCLUSIONS: Preoperative and postoperative radiotherapy have equal prophylactic efficacy to prevent heterotopic ossification following hip surgery. The main advantage of preoperative radiotherapy are the simple management of the patient, the reduction of possible complications associated with transport and positioning of the patient in the postoperative period as well as excellent acceptance of this treatment concept by patients, nurses and staff.  相似文献   
986.
987.
Ten batches of Arzúa, a soft cow's-milk cheese produced in northwest Spain, were prepared from pasteurized milk. Two (control) batches (CB) were made with a commercial starter containingLactococcus lactis subspecieslactis andcremoris. Another eight batches (MB) were made with the commercial starter plus one of eightMicrococcus spp. strains previously isolated from raw-milk Arzúa cheeses. In all MB, β-casein degradation over the 30-day ripening period was more pronounced (mean 31%) than in the CB (mean 12%). αS1-Casein degradation was highly variable in the MB, though mean degradation over the ripening period (75%) was similar to that observed in the CB (73%). Similarly, volatile fatty acid (VFA) content was highly variable in the MB, with the mean content at 30 days (3.8 mEq per 100 g) being higher than in the CB (1.6 mEq per 100 g). Rheological characterization of the cheeses (by uniaxial compression) revealed significant differences between batches, with some samples fracturing under the compression pressure applied and others not. Sensory evaluation also revealed significant differences. “Non-milk” aromas were more frequently detected in batches made with lipolytic micrococcal strains. Betweenbatch differences in tastes and texture were also detected. Multiple correlation analysis of the data obtained at day 15 of ripening revealed statistically significant positive correlations (r>0.70) between αS1-casein content and dry matter content, between αS1-casein content and sensorially evaluated firmness, and between VFA content and sensorially evaluated rancidity. Statistically significant negative correlations between sensorially evaluated firmness and the ratio of αS1-I content to αS1-casein content were detected. The results of this study suggest a need for further studies aimed at selecting those strains which could be most suitable for the production of Arzüa cheeses; due to their effects on texture, αS1-caseinolytic strains seem to be more appropriate than β-caseinolytic ones.  相似文献   
988.
989.
Congenital adrenal hyperplasia due to 21-hydroxylase deficiency (21-OH), in its severe forms, produces virilization of the external genitalia of the affected female fetus. Early treatment with dexamethasone of the pregnant mother at risk of a fetus with 21-OH deficiency avoids the masculinization of the affected female fetus. We present a pregnant mother, where the prenatal diagnosis was established by DNA analysis of a chorionic villous sample obtained in the 9th week of gestation. Molecular analysis showed the female fetus to be affected of 21-OH deficiency. Maternal treatment with dexamethasone started on the 6th week of gestation has prevented the virilization of the affected baby. No significant side effects have been encountered. Prenatal diagnosis and treatment for 21-OH deficiency is effective and safe, as is described in the literature. This is the first case in Spain where both prenatal molecular diagnosis and treatment for 21-OH deficiency have been reported.  相似文献   
990.
Dietary control is known to influence diabetic processes. Therefore, the purpose of this work was to determine possible effects brought about by two different dietary protein levels on the nutritional diet utilization in alloxan-diabetic rats. Rats were divided in two groups: 1) One fed on 12% and 2) one a 4% protein diet. Each group was then divided into two subgroups: A) non diabetic and B) diabetic. Weight parameters, food intake, food efficiency (FE), digestive efficiency (DE), metabolic utilization (MU), retained N/ingested N ratio as well as initial and final glycemia were evaluated at the beginning and at the end of the experiment. A decrease in body weight, FE, DE and MU was observed in the control rats of group 2A, in comparison with the group 1A. Experimental diabetes led to increased FE in 1B group in relation to those of group 1A. Also decreased body weight and FE as well as increased food intake and DE were found in the control animals of 2B group. Glycemia increased in diabetic rats as compared with non-diabetic rats, in both groups, 1 and 2. The data suggest that under the experimental conditions cited, both the nutritional utilization of the diet and the diabetogenic status might be modulated by the dietary protein ingested level.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号