全文获取类型
收费全文 | 970篇 |
免费 | 7篇 |
专业分类
化学工业 | 15篇 |
机械仪表 | 1篇 |
能源动力 | 3篇 |
轻工业 | 6篇 |
无线电 | 3篇 |
一般工业技术 | 21篇 |
冶金工业 | 912篇 |
自动化技术 | 16篇 |
出版年
2023年 | 2篇 |
2022年 | 1篇 |
2021年 | 1篇 |
2017年 | 7篇 |
2016年 | 1篇 |
2015年 | 1篇 |
2014年 | 2篇 |
2013年 | 5篇 |
2012年 | 3篇 |
2011年 | 11篇 |
2010年 | 2篇 |
2009年 | 1篇 |
2008年 | 3篇 |
2007年 | 3篇 |
2006年 | 1篇 |
2005年 | 3篇 |
2004年 | 1篇 |
2003年 | 5篇 |
2000年 | 3篇 |
1999年 | 39篇 |
1998年 | 310篇 |
1997年 | 190篇 |
1996年 | 95篇 |
1995年 | 59篇 |
1994年 | 39篇 |
1993年 | 61篇 |
1992年 | 7篇 |
1991年 | 8篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 10篇 |
1987年 | 3篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1983年 | 1篇 |
1982年 | 5篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1978年 | 4篇 |
1977年 | 15篇 |
1976年 | 42篇 |
1975年 | 1篇 |
1965年 | 2篇 |
1956年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有977条查询结果,搜索用时 15 毫秒
31.
SF Zarbock 《Canadian Metallurgical Quarterly》1997,2(6):288-9, 294
In recent years, home visitation services have been widely promoted as a means of preventing health and developmental problems in children from vulnerable families. The U.S. Advisory Board of Child Abuse and Neglect, for example, recommended that home visitation services be made available to all parents of newborns to prevent child abuse and neglect. 相似文献
32.
SF Nielsen SB Christensen G Cruciani A Kharazmi T Liljefors 《Canadian Metallurgical Quarterly》1998,41(24):4819-4832
A large number of substituted chalcones have been synthesized and tested for antileishmanial and lymphocyte-suppressing activities. A subset of the chalcones was designed by using statistical methods. 3D-QSAR analyses using 67 (antileishmanial activity) and 63 (lymphocyte-suppressing activity) of the compounds for the training sets and 9 compounds as an external validation set were performed by using the GRID/GOLPE methodology. The Smart Region Definition procedure with subsequent region selection as implemented in GOLPE reduced the number of variables to approximately 1300 yielding 3D-QSAR models of high quality (lymphocyte-suppressing model, R2 = 0. 90, Q2 = 0.80; antileishmanial model, R2 = 0.73, Q2 = 0.63). The coefficient plots indicate that steric interactions between the chalcones and the target are of major importance for the potencies of the compounds. A comparison of the coefficient plots for the antileishmanial effect and the lymphocyte-suppressing activity discloses significant differences which should make it possible to design chalcones having a high antileishmanial activity without suppressing the proliferation of lymphocytes. 相似文献
33.
Antimicrobial therapy can be a confounding factor in the diagnosis of urinary tract infection and is not always reported to laboratories by physicians. We developed a microbiologic assay for screening urine specimens for antimicrobial agents. Bacillus stearothermophilus was used as the indicator bacteria. A total of 1,921 urine specimens from three hospitals in Taiwan were screened using this assay. Of the samples assayed, 1,293 were positive for antimicrobial agents. Agreement between information provided by physicians and laboratory findings was 68.5% (419/612). In the presence of antimicrobial agents in the urine samples, the isolation of yeasts and Pseudomonas aeruginosa increased dramatically, from 4.5 to 19.5% and 4.2 to 13.2%, respectively. Additionally, Escherichia coli was more resistant to gentamicin (75.3% vs 48.7%, p < 0.0001), norfloxacin (85.2% vs 64.6%, p = 0.0006) and co-trimoxazole (58.5% vs 35.5%, p = 0.0018). In view of the high rate of occurrence of antimicrobial agents in urine specimens and the lack of information provided by most physicians to laboratories, a screening method to detect the presence (or absence) of antimicrobials in urine specimens may be a useful tool particularly in areas such as Taiwan where antimicrobial agents are commonly abused. 相似文献
34.
35.
Changes in calorie intake and weight gain were evaluated in five children with cystic fibrosis (CF) who received behavioral intervention and four children with CF who served as wait list controls. The behavioral intervention was a 6-week group treatment that provided nutritional education plus management strategies aimed at mealtime behaviors that parents find most problematic. The control group was identified prospectively and was evaluated on all dependent measures at the same points in time pre- and posttreatment as the intervention group. Difference scores on calorie intake and weight gain from pre- to posttreatment were compared between groups using t tests for independent samples. The behavioral intervention group increased their calorie intake by 1,032 calories per day, while the control group's intake increased only 244 calories per day from pre- to posttreatment [t(6) = 2.826, p = 0.03]. The intervention group also gained significantly more weight (1.7 kg) than the control group (0 kg) over the 6 weeks of treatment [t(7) = 2.588, p = 0.03] and demonstrated catchup growth for weight, as indicated by improved weight Z scores (-1.18 to -0.738). The control group showed a decline in weight Z scores over this same time period (-1.715 to -1.76). One month posttreatment, the intervention was replicated with two of the four children from the control group. Improved calorie intake and weight gain pre- to posttreatment were again found in these children. At 3- and 6-month follow-up study of children receiving intervention, maintenance of calorie intake and weight gain was confirmed. No changes were found on pulmonary functioning, resting energy expenditure, or activity level pre- to posttreatment. This form of early intervention appears to be promising in improving nutritional status and needs to be investigated over a longer period of time to evaluate the effects of treatment gains on the disease process. 相似文献
36.
STATEMENT OF PROBLEM: The practice of fixed prosthodontic has changed dramatically with the introduction of innovative techniques and materials. Adhesive resin systems are examples of these changes that have led to the popularity of bonded ceramics and resin-retained fixed partial dentures. Today's dentist has the choice of a water-based luting agent (zinc phosphate, zinc polycarboxylate, glass ionomer, or reinforced zinc oxide-eugenol) or a resin system with or without an adhesive. Recent formulations of glass ionomer luting agents include resin components (resin-modified glass ionomers), which are increasingly popular in clinical practice. PURPOSE: This review summarizes the research on these systems with the goal of providing information that will help the reader choose the most suitable material. MATERIAL: The scientific studies have been evaluated in relation to the following categories: (1) biocompatibility, (2) caries or plaque inhibition, (3) microleakage, (4) strength and other mechanical properties, (5) solubility, (6) water sorption, (7) adhesion, (8) setting stresses, (9) wear resistance, (10) color stability, (11) radiopacity, (12) film thickness or viscosity, and (13) working and setting times. In addition, guidelines on luting-agent manipulation are related to available literature and include: (1) temporary cement removal, (2) smear layer removal, (3) powder/liquid ratio, (4) mixing temperature and speed, (5) seating force and vibration, and (6) moisture control. Tables of available products and their properties are also presented together with current recommendations by the authors with a rationale. 相似文献
37.
The 3,6-dideoxyhexoses are found in the lipopolysaccharides of gram-negative bacteria, where they have been shown to be the dominant antigenic determinants. Of the five 3,6-dideoxyhexoses known to occur naturally, four have been found in various strains of Salmonella enterica (abequose, tyvelose, paratose, and colitose) and all five, including ascarylose, are present among the serotypes of Yersinia pseudotuberculosis. Although there exists one report of the cloning of the rfb region harboring the abequose biosynthetic genes from Y. pseudotuberculosis serogroup HA, the detailed genetic principles underlying a 3,6-dideoxyhexose polymorphism in Y. pseudotuberculosis have not been addressed. To extend the available information on the genes responsible for 3,6-dideoxyhexose formation in Yersinia spp. and facilitate a comparison with the established rfb (O antigen) cluster of Salmonella spp., we report the production of three overlapping clones containing the entire gene cluster required for CDP-ascarylose biosynthesis. On the basis of a detailed sequence analysis, the implications regarding 3,6-dideoxyhexose polymorphism among Salmonella and Yersinia spp. are discussed. In addition, the functional cloning of this region has allowed the expression of Ep (alpha-D-glucose cytidylyltransferase), Eod (CDP-D-glucose 4,6-dehydratase), E1 (CDP-6-deoxy-L-threo-D-glycero-4- hexulose-3-dehydrase), E3 (CDP-6-deoxy-delta 3,4-glucoseen reductase), Eep (CDP-3,6-dideoxy-D-glycero-D- glycero-4-hexulose-5-epimerase), and Ered (CDP-3,6-dideoxy-L-glycero-D-glycero-4-hexulose-4-reductase), facilitating future mechanistic studies of this intriguing biosynthetic pathway. 相似文献
38.
Endoglin (CD 105) is a cell surface antigen widely expressed on vascular endothelium, syncytiotrophoblast, some tissue macrophages, certain culture cells (including early leukemic B-lineage) and some endothelial cell lines. Though its relation to the transforming growth factor-beta (TGF-beta) receptor system is well documented, its function and detailed pattern of expression still remain to be clarified. We examined the differential tissue distribution of endoglin in human lymphoid organs and placenta with several anti-CD 105 monoclonal antibodies (mAbs) using an indirect immunoperoxidase technique, and performed semi-quantitative measurements using an image-analyzing system for comparison. Arterial, venous and capillary endothelia in these organs were reactive with anti-CD 105 mAbs at varying intensities. Interestingly, a distinctly stronger staining pattern was observed in the high endothelial venules (HEVs) which may indicate a special role for endoglin in lymphocyte trafficking. Syncytiotrophoblast expressed endoglin strongly on their apical cell membrane. Extravillous trophoblasts at certain locations selectively expressed endoglin on their cell membranes, suggesting a special role for this surface antigen during trophoblast differentiation. 相似文献
39.
M Sivanandham P Shaw SF Bernik E Paoletti MK Wallack 《Canadian Metallurgical Quarterly》1998,46(5):261-267
The objective of this study was to evaluate the clinical efficacy and cost effectiveness of inpatient and outpatient laparoscopic lumbar diskectomy (LLD) compared with laminectomy (LAM) in the surgical treatment of disabling L5-S1 disk herniation. Sixty-two adults underwent surgery for herniated L5-S1 intervertebral disks (31 LLD and 31 LAM). Operative blood loss (EBL) (milliliters), operative time (ORT) (minutes), hospital stay (LOS), and rehabilitation time to normal activity (REHAB) (days), recurrent symptoms, postoperative morbidity, percent pain free, and hospital patient charges were calculated. Thirty LLD patients (97%) had immediate relief of disk pain. Morbidity after LLD included transient urinary retention (one) and rectus hematoma (one). One LAM patient had a pseudomeningocele. Among patients observed for > or =6 months, with a median follow up time of 34 months, 22 of 25 LLD patients (88%) returned to normal activity, while 12 of the LAM group (52%) were disabled (p = 0.004). Functional outcome was improved by LLD for workers compensation patients followed > or =6 months, with 86% LAM disabled, vs. 10% LLD (p = 0.001). Sixteen LLD patients (52%) and 18 (58%) of the LAM group needed postoperative physical therapy. Four LLD patients recurred; three required reoperation. Four LAM patients had surgery for recurrent disk herniation. ORT was longer for LLD than LAM (210 vs. 158 minutes, median, p < 0.05). EBL and REHAB time were significantly reduced with LLD, vs. LAM. With a median follow-up of 34 months, 58% of LLD and 39% of LAM patients followed > or =6 months were pain free. Outpatient LLD (n = 9) reduced LOS (1 day vs. 2 days and 4 days, p < 0.01) and lowered patient charges ($4,405 vs. $5,723 and $7,192, p < 0.01) compared with inpatient LLD (n = 23) and LAM, respectively. LLD is a safe, cost-effective, minimally invasive alternative to LAM for treating herniated L5-S1 disks. Compared with LAM, LLD reduces EBL, LOS, REHAB time, and patient charges, improves function, and increases long-term pain relief. Cost effectiveness is optimized when LLD is performed as outpatient surgery. 相似文献
40.
Stretch injury to the phrenic nerve is an unusual cause of unilateral diaphragmatic paralysis. In this case the injury occurred while the patient was lying on the ground and cutting down a Christmas tree with a hand saw. 相似文献