全文获取类型
收费全文 | 9657篇 |
免费 | 629篇 |
国内免费 | 14篇 |
专业分类
电工技术 | 128篇 |
综合类 | 5篇 |
化学工业 | 2423篇 |
金属工艺 | 160篇 |
机械仪表 | 320篇 |
建筑科学 | 383篇 |
矿业工程 | 20篇 |
能源动力 | 398篇 |
轻工业 | 1777篇 |
水利工程 | 129篇 |
石油天然气 | 52篇 |
武器工业 | 2篇 |
无线电 | 499篇 |
一般工业技术 | 1432篇 |
冶金工业 | 910篇 |
原子能技术 | 65篇 |
自动化技术 | 1597篇 |
出版年
2024年 | 21篇 |
2023年 | 94篇 |
2022年 | 255篇 |
2021年 | 437篇 |
2020年 | 270篇 |
2019年 | 308篇 |
2018年 | 389篇 |
2017年 | 396篇 |
2016年 | 433篇 |
2015年 | 294篇 |
2014年 | 413篇 |
2013年 | 770篇 |
2012年 | 656篇 |
2011年 | 763篇 |
2010年 | 510篇 |
2009年 | 551篇 |
2008年 | 488篇 |
2007年 | 393篇 |
2006年 | 331篇 |
2005年 | 238篇 |
2004年 | 211篇 |
2003年 | 191篇 |
2002年 | 185篇 |
2001年 | 131篇 |
2000年 | 132篇 |
1999年 | 116篇 |
1998年 | 325篇 |
1997年 | 235篇 |
1996年 | 152篇 |
1995年 | 101篇 |
1994年 | 69篇 |
1993年 | 57篇 |
1992年 | 33篇 |
1991年 | 25篇 |
1990年 | 28篇 |
1989年 | 26篇 |
1988年 | 21篇 |
1987年 | 20篇 |
1986年 | 18篇 |
1985年 | 27篇 |
1984年 | 28篇 |
1983年 | 27篇 |
1982年 | 14篇 |
1981年 | 16篇 |
1980年 | 14篇 |
1979年 | 10篇 |
1978年 | 8篇 |
1977年 | 17篇 |
1976年 | 24篇 |
1975年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
951.
Vales-Alonso J. de Vicente F.I. Gonzalez-Castano E.J. Pousada-Carballo J.M. 《Communications Letters, IEEE》2001,5(6):275-276
The authors propose a feasible real-time GSM terminal detector, to be located in a restricted area. All idle terminals entering it are forced to emit signaling information, which can be captured. As far as the authors know, market alternatives are nonexistent. A possible application is presented: a mobile terminal detector for airport access bridges 相似文献
952.
L. Rejn A. Rosas‐Zavala J. Porcayo‐Calderon V. M. Castao 《Polymer Engineering and Science》2000,40(9):2101-2104
Percolation in carbon black‐filled polymeric concrete, is discussed based on the measured changes in electrical conductivity and morphology of the composite at different concentrations of carbon black. The percolation threshold ranged between 6 and 7 wt% (based on resin weight) of carbon black. Above this concentration, the filler particles formed agglomerates in contact with each other, suggesting that the conduction process is nearly ohmic in nature. A power law predicted by percolation theory described the behavior of the conductivity as a function of carbon black content. Microscopic analysis showed the presence of a continuous structure formed by the polyester resin and carbon black, in which silica particles were embedded. 相似文献
953.
LS Belli L de Carlis G Rondinara AB Alberti G Bellati A De Gasperi D Forti G Idèo 《Canadian Metallurgical Quarterly》1998,27(6):1524-1529
Maintenance of adequate immunosuppression and avoidance of side-effects are the goals of long-term management of all organ-transplanted patients. We here report the final results of a prospective, randomized trial comparing early cyclosporine monotherapy versus double-drug therapy (cyclosporine and steroids) in adult liver transplantation patients. One hundred four patients were randomized 3 months after transplantation either to continue (Group I = 50 patients) or to stop steroids (Group II = 54 patients). Patients on a double-drug regimen were maintained long term on methylprednisolone at a dose of 0.1 mg/kg/d. Target cyclosporine trough levels were between 150 and 250 ng/mL in both groups. Our main points of interest were the prevalence of acute and chronic rejections and steroid-related side-effects in the two groups of patients. Mean follow-up was 41 +/- 16 months (range, 4-68 months). Patient actuarial survival 2 and 5 years after randomization was similar in the two groups (82% vs. 83% and 82% vs. 77%). The prevalence of acute rejections after randomization was, respectively, 8% and 4%. A single episode of chronic rejection was observed only in a patient on long-term steroid therapy. Side-effects of steroid therapy were less frequent in patients weaned off steroids, and when considering hypertension and diabetes, the differences between the two groups were statistically significant. Early cyclosporine monotherapy is a safe undertaking in liver transplantation because it allows a significant reduction of steroid-related side-effects without increasing the risk of acute and chronic rejection. After 5 years, patient survival was similar in patients with or without steroids. 相似文献
954.
NR Asad LM Asad AB Silva I Felzenszwalb AC Leit?o 《Canadian Metallurgical Quarterly》1998,407(3):253-259
Despite a large body of evidence showing the beneficial effects of successful treatment of anemia with recombinant human erythropoietin (EPO) in patients with end-stage renal disease, controversy remains as to whether EPO treatment of anemia can improve the nutritional status in patients on maintenance hemodialysis. This prompted us to conduct a prospective study in 41 hemodialysis patients with basal hemoglobin less than 9 g/dl. The dose of EPO was increased for 12 weeks to achieve the target hemoglobin concentration of 10 g/dl and then titrated in the following 12 weeks to maintain the target value. Nutritional status was assessed at baseline and after 6 months of follow-up, using the global protein-calorie malnutrition (PCM) index proposed by Bilbrey and Cohen. A low global PCM score indicates better nutrition. The results showed that hemoglobin values significantly increased from 8.7 +/- 0.8 g/dl at baseline to 10.7 +/- 0.5 g/dl in the 6th month (p < 0.001). No significant changes were observed in the normalized protein catabolic rate and Kt/V during the study period. Global PCM scores improved from 30.0 +/- 7.5 to 23.6 +/- 3.1 (p < 0.001) and paralleled the correction of anemia by EPO treatment. The data were consistent with a major improvement in the nutritional markers of relative body weight, triceps skinfold, midarm circumference, midarm muscle circumference, serum albumin, serum transferrin and total lymphocyte count in the 6th month as compared to baseline. The percentages of mild and moderate-severe PCM at baseline were 32 and 58%, respectively. These percentages were significantly reduced during the 6th month to 20 and 30%, respectively (p = 0.0004). In summary, correction of renal anemia with EPO improves the nutritional status in hemodialysis patients. A postulated mechanism is that EPO may exhibit anabolic effects, with a better utilization of ingested protein. 相似文献
955.
N Rodriguez-Cousi?o FE Nargang R Baardman W Neupert R Lill DA Court 《Canadian Metallurgical Quarterly》1998,273(19):11527-11532
TOM22 is an integral component of the preprotein translocase of the mitochondrial outer membrane (TOM complex). The protein is anchored to the lipid bilayer by a central trans-membrane segment, thereby exposing the amino-terminal domain to the cytosol and the carboxyl-terminal portion to the intermembrane space. Here, we describe the sequence requirements for the targeting and correct insertion of Neurospora TOM22 into the outer membrane. The orientation of the protein is not influenced by the charges flanking its trans-membrane segment, in contrast to observations regarding proteins of other membranes. In vitro import studies utilizing TOM22 preproteins harboring deletions or mutations in the cytosolic domain revealed that the combination of the trans-membrane segment and intermembrane space domain of TOM22 is not sufficient to direct import into the outer membrane. In contrast, a short segment of the cytosolic domain was found to be essential for the import and assembly of TOM22. This sequence, a novel internal import signal for the outer membrane, carries a net positive charge. A mutant TOM22 in which the charge of the import signal was altered to -1 was imported less efficiently than the wild-type protein. Our data indicate that TOM22 contains physically separate import and membrane anchor sequences. 相似文献
956.
Drying of textiles is one of the energy‐intensive unit operations and stenters are the most widely used drying machines in textile finishing mills. This study reveals energetic and exergetic analysis of a stenter system in a textile finishing factory based on actual operational data. The system includes a stenter along with its circulating and induced draft fans, a hot oil boiler and an oil circulating pump. The exergy destructions in each of the components of the overall systems were determined for average values of experimentally measured parameters. Exergy efficiencies of the system components were determined which help in assessing their performance and to establish strategies for improvement. The exergetic efficiencies of the stenter and hot oil boiler were found to be 28.7 and 34.7%, respectively, while the overall exergy efficiency of the system was obtained to be 34.4%. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
957.
Roque Calvo Rosario Domingo Miguel A. Sebastián 《International Journal of Flexible Manufacturing Systems》2007,19(3):247-263
Manufacturing flexibility is becoming a fundamental production objective, along with cost, quality, and delivery time. Current
production systems face quick changes in market conditions and they need to adapt in this environment. The supply chain and
industrial globalization give an important role for assembly systems. Placed at the end of the value chain, assembly systems
must face those quick changes successfully to reach the expected performance. The key performance indicators are normally
based on cost, quality, and delivery time objectives. Reducing costs and improving quality are almost universal goals. Delivery
time is typically determined by customer demand in the supply chain, planning from make-to-stock to make-to-order, and aspiring
to reach a just-in-time manufacturing system. In this context, flexibility could be the differential advantage to tackle uncertainty.
Closely related to the rest of production objectives and the overall performance of the system, flexibility must be integrated
in the system for successful decision-making in operations. This work presents this approach of flexibility. A brief review
of flexibility concepts and measurements in the literature precedes an introduction to flexibility, defined based on the function
of utility. This function represents the expectations of system performance. This approach allows the formulation of the taxonomy
of operational flexibility in agreement with the classical types identified in former works. Next, an integer model is programmed
to simulate the basic behavior of task planning in a make-to-order assembly system. This first application illustrates flexibility
quantification based on utility evolution. The use of common industrial parameters to quantify operational flexibility will
finally facilitate an integrated interpretation of system performance trends. 相似文献
958.
Cephamycin C-producing microorganisms contain a two-protein enzyme system that converts cephalosporins to 7-methoxycephalosporins. Interaction between the two component proteins P7 (Mr 27,000) and P8 (Mr 32,000) has been studied by immunoaffinity chromatography using anti-P7 and anti-P8 antibodies, cross-linking with glutaraldehyde, and fluorescence spectroscopy analysis. Co-renaturation of the P7 and P8 polypeptides resulted in the formation of a protein complex with a molecular mass of 59 kDa, which corresponds to a heterodimer of P7 and P8. Glutaraldehyde cross-linking of the polypeptides after assembly of the protein complex showed the presence of a single heterodimer form that reacted with antibodies against P7 and P8. Each separate protein did not associate with itself into multimers. The P7.P8 complex co-purified by immunoaffinity chromatography from extracts of Nocardia lactamdurans and Streptomyces clavuligerus, suggesting that both proteins are present as an aggregate in vivo. Fluorescence spectroscopy studies of 5-methylaminonaphthalene-1-sulfonyl-P7 in response to increasing concentrations of P8 showed a blue shift in the fluorophore emission, indicating a conformational change of P7 in response to the interaction of P8 with an apparent dissociation constant of 47 microM. NADH showed affinity for the P7 component. The P7.P8 complex interacted strongly with the substrates S-adenosylmethionine and cephalosporin C, differently from that occurring with the separate P7 or P8 components, resulting in a strong blue shift in the fluorescence emission spectra of the complex. 相似文献
959.
A systematic method of analyzing the colorimetric behavior of a set of observers is proposed. The differences between each observer and a standard one are analyzed with different procedures in two color‐representation systems. It is apparent that these differences strongly depend on the color‐representation system in which they are analyzed. Results obtained in this work indicate that comparison between two observers should be carried out by applying an optimized operator. This operator minimizes the differences between the color‐representation systems associated with the observers that are compared. The proposed method should be applied when color‐matching properties of a set of observers, or when color matching obtained with different colorimetric instruments, are compared. © 2002 Wiley Periodicals, Inc. Col Res Appl, 28, 15–24, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/col. 相似文献
960.
L. Troidle T. Eisen F.o. Finkelstein . 《Hemodialysis international. International Symposium on Home Hemodialysis》2004,8(1):80-81
The Dialysis Outcome and Quality Initiative has guidelines for vascular access and states that the dialysis catheter (DC) should be limited to less than 20% of the end-stage renal disease (ESRD) patients. Our center has found this target difficult to achieve.
Objective: We wondered what the reasons for use of a DC might be.
Methods: We noted the number of patients with a DC in place and assessed the reasons why the DC was being used on 8/1/03.
Results: 73 of the 170 (42.9%) patients had a DC on 8/1/03. 24 (32.9%) of the patients refused to have initial arteriovenous fistulae or grafts (AVF/G) or a secondary AVF/G revision or replacement procedure performed after initial AVF/G failure. 15 (20.5%) patients had a maturing AVF/G, 12 (16.4%) had significant medical and/or surgical contraindications for AVF/G placement, 9 (12.3%) patients were awaiting surgical thrombectomy, revision or placement of AVF/G, 6 patients (8.2%) were awaiting transfer to CPD therapy, 4 (5.5%) patients were undecided about having an AVF/G placed, and 1 (1.4%) had acute renal failure and early ESRD recovery was expected. Only 2 (2.7%) patients had no access plan by the nephrology team.
Conclusions: Patients' refusal for an AVF/G placement and patients with a maturing AVF/G or awaiting surgical revision or placement were the most common reasons for the use of a DC in our center. To significantly impact on the high use of the DC, it would be crucial to better understand the reasons for patients' refusals. 相似文献
Objective: We wondered what the reasons for use of a DC might be.
Methods: We noted the number of patients with a DC in place and assessed the reasons why the DC was being used on 8/1/03.
Results: 73 of the 170 (42.9%) patients had a DC on 8/1/03. 24 (32.9%) of the patients refused to have initial arteriovenous fistulae or grafts (AVF/G) or a secondary AVF/G revision or replacement procedure performed after initial AVF/G failure. 15 (20.5%) patients had a maturing AVF/G, 12 (16.4%) had significant medical and/or surgical contraindications for AVF/G placement, 9 (12.3%) patients were awaiting surgical thrombectomy, revision or placement of AVF/G, 6 patients (8.2%) were awaiting transfer to CPD therapy, 4 (5.5%) patients were undecided about having an AVF/G placed, and 1 (1.4%) had acute renal failure and early ESRD recovery was expected. Only 2 (2.7%) patients had no access plan by the nephrology team.
Conclusions: Patients' refusal for an AVF/G placement and patients with a maturing AVF/G or awaiting surgical revision or placement were the most common reasons for the use of a DC in our center. To significantly impact on the high use of the DC, it would be crucial to better understand the reasons for patients' refusals. 相似文献