全文获取类型
收费全文 | 1973篇 |
免费 | 20篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 20篇 |
化学工业 | 119篇 |
金属工艺 | 24篇 |
机械仪表 | 21篇 |
建筑科学 | 26篇 |
矿业工程 | 3篇 |
能源动力 | 18篇 |
轻工业 | 77篇 |
水利工程 | 5篇 |
石油天然气 | 5篇 |
无线电 | 145篇 |
一般工业技术 | 204篇 |
冶金工业 | 1232篇 |
原子能技术 | 15篇 |
自动化技术 | 83篇 |
出版年
2021年 | 11篇 |
2019年 | 7篇 |
2018年 | 15篇 |
2017年 | 11篇 |
2016年 | 8篇 |
2015年 | 9篇 |
2014年 | 11篇 |
2013年 | 42篇 |
2012年 | 24篇 |
2011年 | 41篇 |
2010年 | 23篇 |
2009年 | 21篇 |
2008年 | 31篇 |
2007年 | 47篇 |
2006年 | 28篇 |
2005年 | 23篇 |
2004年 | 24篇 |
2003年 | 25篇 |
2002年 | 24篇 |
2001年 | 27篇 |
2000年 | 11篇 |
1999年 | 47篇 |
1998年 | 344篇 |
1997年 | 237篇 |
1996年 | 166篇 |
1995年 | 83篇 |
1994年 | 62篇 |
1993年 | 75篇 |
1992年 | 19篇 |
1991年 | 35篇 |
1990年 | 30篇 |
1989年 | 32篇 |
1988年 | 21篇 |
1987年 | 18篇 |
1986年 | 26篇 |
1985年 | 28篇 |
1984年 | 7篇 |
1983年 | 22篇 |
1982年 | 15篇 |
1981年 | 16篇 |
1980年 | 27篇 |
1979年 | 16篇 |
1978年 | 14篇 |
1977年 | 43篇 |
1976年 | 81篇 |
1975年 | 9篇 |
1974年 | 9篇 |
1973年 | 6篇 |
1972年 | 6篇 |
1970年 | 6篇 |
排序方式: 共有1997条查询结果,搜索用时 15 毫秒
1.
Water Resources Management - Public awareness of water quality concerns has increased since the Flint, MI crisis, but knowledge about water resources management remains low. Consequently,... 相似文献
2.
FC Breedveld 《Canadian Metallurgical Quarterly》1997,141(15):717-719
Slow-acting antirheumatic drugs (SAARDs) are usually prescribed in rheumatoid arthritis only when non-steroid anti-inflammatory drugs can no longer suppress the inflammation or when articular damage is radiologically apparent. It was established recently that articular damage occurs in an early phase of RA. This damage is linked to subsequent disability; to prevent it is the purpose of SAARDs. In view of the short-term reduction of arthritis activity and improvement of function as well as the meanwhile established fact that the side effects of SAARDs are not different from those of other antirheumatic agents, SAARDs should be prescribed in an early phase of RA. 相似文献
3.
Adaptive increases in renal bicarbonate reabsorption occur in response to acute increases in filtered bicarbonate (FLHCO3). In a previous study, we showed that an increase in FLHCO3 induced by plasma volume expansion increased the Vmax for Na+/H+ exchange activity in renal cortical brush border membrane vesicles (BBMV), providing a potential mechanism for the adaptive increase in HCO3- reabsorption. The present studies were undertaken to determine whether the increase in FLHCO3 induced by plasma expansion also stimulates the other major H+ transporter in cortical BBMV, the H(+)-ATPase. H(+)-ATPase activity was assessed in BBMV obtained from hydropenic and plasma expanded Munich-Wistar rats, using a NADH-linked ATPase assay. H(+)-ATPase activity was measured as the ouabain and oligomycin-insensitive, bafilomycin A1-sensitive component of total ATPase activity. Acute plasma expansion doubled single nephron FLHCO3, and this change was associated with a 64% increase in the Vmax for H(+)-ATPase activity, with no change in apparent Km. The Vmax for H(+)-ATPase activity correlated directly with whole kidney GFR and FLHCO3 (r = 0.68 and 0.72, respectively), and with single nephron GFR and FLHCO3 (r = 0.76 and 0.80, respectively). Thus, the mechanism for the adaptive increase in proximal tubular HCO3- reabsorption that occurs in response to acute increases in FLHCO3 appears to be related to increased activity of both H(+)-ATPase and Na+/H+ exchange in the apical membrane of the proximal tubule epithelium. 相似文献
4.
5.
6.
7.
JF DeFrance S Sands FC Schweitzer L Ginsberg JC Sharma 《Canadian Metallurgical Quarterly》1997,9(4):283-293
The purpose of this article is to deliberate the moral and legal dilemma entailed in the weapon of the labour strike as a pressure tactic on the Israeli Finance Ministry regarding job slots, budgets and, in effect, violating the collective agreement signed by the nurses and impairing patients' treatment, as opposed to refraining from striking and suffering the heavy burden of work, the lack of trained personnel, low wages, and the inability to give patients proper, high quality treatment. 相似文献
8.
9.
The effect of particle distribution on damage formation in particulate reinforced metal matrix composites deformed in compression 总被引:1,自引:0,他引:1
P.B. Prangnell S.J. Barnes S.M. Roberts P.J. Withers 《Materials Science and Engineering: A》1996,220(1-2):41-56
Image analysis results are reported on the generation of damage in particulate reinforced metal matrix composites during compressive deformation. The technique allows the automated collection of data on the incidence of particle fracture and void formation in the matrix as a function of important microstructural parameters such as local particle volume fraction and particle size. There is a strong relationship between damage and the local volume fraction of the reinforcement proving that damage formation is accentuated in regions of particle clustering. With the SiC reinforced materials examined, there was observed to be a change in dominance of damage mechanism from particle fracture at low local volume fractions to void formation in the matrix within strongly clustered regions. The results are compared with finite element (FE) modelling of the compressive deformation of clustered particles using a simple cluster of equi-spaced particles. The FE results suggest that plastic flow is generally inhibited in clustered regions. In certain highly clustered configurations shielding is such that flow does not occur in the heart of the cluster even at high levels of average plastic strain. The modelling suggests that the change in dominance of damage mechanism is related to the dramatic increase in tensile hydrostatic stresses in the matrix with higher levels of particle clustering. 相似文献
10.
D Levine PD Barnes S Sher RC Semelka W Li CR McArdle S Worawattanakul RR Edelman 《Canadian Metallurgical Quarterly》1998,206(2):549-554
PURPOSE: To evaluate the normal appearance of fetal anatomy, the conspicuity of fetal organs, the reproducibility of images, and the limitations to image quality with the use of half-Fourier, single-shot rapid acquisition with relaxation enhancement (RARE) magnetic resonance (MR) imaging. MATERIALS AND METHODS: Fifty-four fetuses of 49 pregnancies underwent MR imaging with the half-Fourier, single-shot RARE technique. Two reviewers attempted to identify 47 organs and anatomic regions in each fetus. Organ or region conspicuity, image quality, and the limitations of image quality were graded. RESULTS: Fetal anatomy was well depicted in fetuses over 20 weeks in gestational age. Fetal imaging was limited by gestational age of 20 weeks or less usually owing to the small size of the organ or region being evaluated and, less frequently, by motion. CONCLUSION: Half-Fourier, single-shot RARE MR imaging provided a detailed and reproducible evaluation of normal fetal anatomy, which can be used as a standard of reference in MR imaging of fetal anomalies. 相似文献