全文获取类型
收费全文 | 7716篇 |
免费 | 246篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 85篇 |
综合类 | 3篇 |
化学工业 | 1232篇 |
金属工艺 | 159篇 |
机械仪表 | 149篇 |
建筑科学 | 279篇 |
矿业工程 | 15篇 |
能源动力 | 128篇 |
轻工业 | 741篇 |
水利工程 | 59篇 |
石油天然气 | 23篇 |
无线电 | 784篇 |
一般工业技术 | 1124篇 |
冶金工业 | 2227篇 |
原子能技术 | 88篇 |
自动化技术 | 871篇 |
出版年
2023年 | 35篇 |
2021年 | 82篇 |
2020年 | 80篇 |
2019年 | 85篇 |
2018年 | 120篇 |
2017年 | 113篇 |
2016年 | 133篇 |
2015年 | 91篇 |
2014年 | 118篇 |
2013年 | 370篇 |
2012年 | 206篇 |
2011年 | 299篇 |
2010年 | 234篇 |
2009年 | 214篇 |
2008年 | 264篇 |
2007年 | 248篇 |
2006年 | 205篇 |
2005年 | 203篇 |
2004年 | 228篇 |
2003年 | 204篇 |
2002年 | 179篇 |
2001年 | 164篇 |
2000年 | 143篇 |
1999年 | 179篇 |
1998年 | 571篇 |
1997年 | 350篇 |
1996年 | 250篇 |
1995年 | 179篇 |
1994年 | 198篇 |
1993年 | 199篇 |
1992年 | 124篇 |
1991年 | 113篇 |
1990年 | 119篇 |
1989年 | 102篇 |
1988年 | 87篇 |
1987年 | 99篇 |
1986年 | 91篇 |
1985年 | 100篇 |
1984年 | 85篇 |
1983年 | 90篇 |
1982年 | 94篇 |
1981年 | 83篇 |
1980年 | 66篇 |
1979年 | 77篇 |
1978年 | 61篇 |
1977年 | 80篇 |
1976年 | 145篇 |
1975年 | 51篇 |
1974年 | 45篇 |
1973年 | 39篇 |
排序方式: 共有7967条查询结果,搜索用时 31 毫秒
31.
Mark Taylor John Miles Dino Bouchlaghem Chimay Anumba 《Canadian Metallurgical Quarterly》2007,21(1):59-62
IT systems for engineers are becoming more numerous and complex and will further proliferate in the future. It is infeasible to expect users to be trained to work with a plethora of systems, especially as many of them will only see occasional use. Therefore, in the near future, systems will need user interfaces that allow intuitive access and usage. This paper examines a new style of user interface based on virtual reality. 相似文献
32.
33.
34.
J Tyson L Tranebjaerg S Bellman C Wren JF Taylor J Bathen B Aslaksen SJ S?rland O Lund S Malcolm M Pembrey S Bhattacharya M Bitner-Glindzicz 《Canadian Metallurgical Quarterly》1997,6(12):2179-2185
The Jervell and Lange-Nielsen syndrome (JLNS) comprises profound congenital sensorineural deafness associated with syncopal episodes. These are caused by ventricular arrhythmias secondary to abnormal repolarisation, manifested by a prolonged QT interval on the electrocardiogram. Recently, in families with JLNS, Neyroud et al. reported homozygosity for a single mutation in KVLQT1 , a gene which has previously been shown to be mutated in families with dominantly inherited isolated long QT syndrome [Neyroud et al . (1997) Nature Genet ., 15, 186-189]. We have analysed a group of families with JLNS and shown that the majority are consistent with mutation at this locus: five families of differing ethnic backgrounds were homozygous by descent for markers close to the KVLQT1 gene and a further three families from the same geographical region were shown to be homozygous for a common haplotype and to have the same homozygous mutation of the KVLQT1 gene. However, analysis of a single small consanguineous family excluded linkage to the KVLQT1 gene, establishing genetic heterogeneity in JLNS. The affected children in this family were homozygous by descent for markers on chromosome 21, in a region containing the gene IsK . This codes for a transmembrane protein known to associate with KVLQT1 to form the slow component of the delayed rectifier potassium channel. Sequencing of the affected boys showed a homozygous mutation, demonstrating that mutation in the IsK gene may be a rare cause of JLNS and that an indistinguishable phenotype can arise from mutations in either of the two interacting molecules. 相似文献
35.
The purpose of this study was to examine the factors which affect the level of fatigue among patients participating in clinical trials in which this symptom had been assessed with the EORTC QLQ-C30. Data were assembled from 2390 patients in ten clinical trials in which the QLQ-C30 had been used to assess baseline and on-study quality of life. The relationship between the level of fatigue reported by the patients on the fatigue scale of this questionnaire and patient and disease characteristics was assessed in univariate and multivariate cross-sectional analyses. In addition, changes in fatigue scores were compared in a longitudinal analysis among patients on two arms of an anti-emetic trial whose emesis control was markedly different. Baseline fatigue levels differed substantially among patients taking part in the different trials. Factors associated with greater fatigue severity on univariate analysis included: female gender, presence of metastatic disease, and poorer performance status. In addition, on multivariate analyses the oldest patients were found to have less fatigue, as were patients with breast cancer, while patients with ovarian and lung cancer experienced greater fatigue. Patients on the arm of the anti-emetic trial in which emesis was better controlled showed significantly less increase in fatigue after receiving chemotherapy. The fatigue scale of the QLQ-C30 appears to provide a useful approach to assessing this important symptom. The relationships found between fatigue and patient and disease characteristics need further exploration as does the degree to which the QLQ-C30 fully captures this dimension of quality of life. 相似文献
36.
Insulin receptor substrate (IRS) proteins are key regulators of basic functions such as cellular growth and metabolism. They provide an interface between multiple receptors and a complex network of intracellular signaling molecules. Two members of this family (IRS-1 and IRS-2) have been identified previously. In this investigation, we analyzed a mouse expressed sequence tag clone that proved to be a new member of the IRS family. Sequence analysis of this clone and comparison with the sequences deposited in GenBank demonstrates this protein may be the murine homolog of rat IRS-3, recently purified and cloned from rat adipocytes. Accordingly, we have named our protein mouse IRS-3. The expressed sequence tag clone contains the complete coding sequence of 1485 bp, encoding a protein of 495 amino acids. Sequence alignment with the other members of the IRS family shows that this protein contains pleckstrin homology and phosphotyrosine-binding domains that are highly conserved. In addition, there is conservation of many tyrosine phosphorylation motifs responsible for interactions with downstream signaling molecules containing SH2 domains. The murine IRS-3 messenger RNA (2.4 kilobases in length) is expressed in many tissues, with highest levels in liver and lung. Mouse IRS-3 is highly expressed in the first part of the embryonic life, when IRS-1 messenger RNA is barely detectable. Unlike the genes encoding IRS-1 and IRS-2, the IRS-3 gene contains an intron (344 bp in length) in the region between the pleckstrin homology and the phosphotyrosine-binding domains. Fluorescent in situ hybridization localized the mouse IRS-3 gene on the telomeric region of chromosome 5G2. Cloning of the murine IRS-3 gene will make it possible to apply genetic approaches to elucidate the physiological role of this new member of the IRS family of proteins. 相似文献
37.
Gleason's score (GS) has been reported to be the most valuable prognostic factor in cases of prostate cancer. GS is solely dependent on the histological architecture of the prostate cancer, but, it seems doubtful that histological patterns are sufficient for evaluating the degree of malignancy of prostate cancer. We previously reported that the estimation of volume-weighted mean nuclear volume (MNV) might be a more useful prognosticator for prostate cancer than subjective histological grading. However, the previous study was conducted on patients treated in a single hospital, and the number of subjects was too small to draw a definitive conclusion. In this study, we analyzed a larger number of subjects at another institution using a blinded study design. A retrospective prognostic study of 195 patients with prostate cancer diagnosed between January 1966 and December 1988 at Kyoto University Hospital, and treated by conservative therapy, was conducted. Unbiased estimates of MNV were compared with the clinical stage and histological grading according to GS with regard to the prognostic value. Univariate analysis revealed that estimates of MNV, clinical stage, and GS all correlated significantly with disease-specific survival in cases of prostate cancer. Multivariate analysis of all cases also revealed that all of these factors were significant independent prognosticators of disease-specific survival. However, focusing on clinically localized cases (stages A, B, and C), multivariate analysis revealed that the estimation of MNV was the only powerful prognosticator of prostate cancer. This study indicates that the estimation of MNV is prognostically equal or superior to GS in cases of prostate cancer. We emphasized that the estimates of MNV is a more objective method for histological grading to predict the malignant potential of prostate cancer. 相似文献
38.
Chromium metabolism of lactating women was evaluated by measuring diet, breast milk, urine, and serum chromium in 17 subjects 60 d postpartum. Breast milk chromium concentration was similar for the 3 d of collection with a mean +/- SE concentration of 3.54 +/- 0.40 nmol/L (0.18 ng/mL). Dietary intake and urinary chromium values were also similar for each of the 3 collection days. Total chromium intake of lactating mothers (0.79 +/- 0.08 mumol/d) was greater than that of reference female subjects (0.48 +/- 0.02). There was a significant correlation (r = 0.84) between serum chromium and urinary chromium excretion. If a breast milk volume of 715 mL is assumed, chromium intake of exclusively breast-fed infants is < 2% of the estimated safe and adequate daily intake of 10 micrograms. In summary, breast milk chromium content is independent of dietary chromium intake and serum or urinary chromium values. Chromium intake also did not correlate with serum or urine chromium but there was a significant relationship between serum and urinary chromium concentrations. 相似文献
39.
MD Margolin AG Cogan M Taylor D Buck TN McAllister C Toth BS McAllister 《Canadian Metallurgical Quarterly》1998,69(8):911-919
The posterior maxilla has traditionally been one of the most difficult areas to successfully place dental implants due to poor bone quality and close approximation to the maxillary sinus. Sinus augmentation procedures have become a viable means of assuring adequate bone for the placement of dental implants in this area. However, with the techniques currently employed, a considerable variation in the quality of bone attained with the sinus augmentation procedure exists. The purpose of this in vivo study was to evaluate the healing response and bone formation stimulated by 3 doses of recombinant human osteogenic protein-1 (rhOP-1), 0.25, 0.6, and 2.5 mg OP-1 per gram of collagen matrix; natural bone mineral; or collagen matrix alone (control) placed in the maxillary sinus of adult chimpanzees. Results were assessed using clinical, histologic, and radiographic techniques. Radiographic analysis of the computed tomography scans taken at 1 week, and 2.5, 4.5, and 6.5 months revealed a more rapid mineralization with the 2.5 mg OP-1/g collagen matrix and natural bone mineral treatment groups. The incremental bone mineral density (BMD) increase for these 2 treatments from 1 week to 2.5 months was over 2.5 times the increase found with the collagen matrix alone; these 2 treatments also had a higher BMD at the most superior slices evaluated when compared to the other 3 groups. Biopsy specimens were taken at 3.5, 5.5, and 7.5 months and for all 5 treatment groups bone formation was observed at all time points in the majority of the specimens. At 7.5 months the 2.5 and 0.6 mg OP-1/g collagen matrix treatment groups had an increase in the percent bone area when compared to the matrix alone control. In conclusion, these results demonstrate that sinus augmentation with natural bone mineral or 2.5 mg OP-1/g collagen matrix induce comparable radiographic and histologic evidence of bone formation and that both of these treatments performed superior to the control group of collagen matrix alone based upon all methods of evaluation. 相似文献
40.
P. R. Taylor S. A. Pirzada M. Manrique 《Metallurgical and Materials Transactions B》1994,25(5):713-720
Thermodynamic calculations, based on a free energy minimization (FEM) program, are presented for a number of material synthesis
systems pertinent to plasma processing. Thermo-dynamic analysis gives general guidelines for the expected reactions and equilibrium
compo-sition of species at different temperatures and pressures. Thermodynamics also allows the preliminary screening of possible
synthesis reactions. These predictions should be used along with kinetic considerations for any proposed reaction system.
Experimental results are presented to elucidate these thermodynamic predictions. 相似文献