全文获取类型
收费全文 | 4138篇 |
免费 | 89篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 47篇 |
综合类 | 2篇 |
化学工业 | 569篇 |
金属工艺 | 106篇 |
机械仪表 | 56篇 |
建筑科学 | 121篇 |
矿业工程 | 27篇 |
能源动力 | 59篇 |
轻工业 | 308篇 |
水利工程 | 23篇 |
石油天然气 | 3篇 |
无线电 | 320篇 |
一般工业技术 | 607篇 |
冶金工业 | 1613篇 |
原子能技术 | 39篇 |
自动化技术 | 332篇 |
出版年
2023年 | 16篇 |
2022年 | 25篇 |
2021年 | 57篇 |
2020年 | 34篇 |
2019年 | 52篇 |
2018年 | 58篇 |
2017年 | 55篇 |
2016年 | 53篇 |
2015年 | 39篇 |
2014年 | 68篇 |
2013年 | 156篇 |
2012年 | 107篇 |
2011年 | 147篇 |
2010年 | 112篇 |
2009年 | 104篇 |
2008年 | 110篇 |
2007年 | 95篇 |
2006年 | 109篇 |
2005年 | 80篇 |
2004年 | 73篇 |
2003年 | 81篇 |
2002年 | 80篇 |
2001年 | 73篇 |
2000年 | 66篇 |
1999年 | 94篇 |
1998年 | 493篇 |
1997年 | 279篇 |
1996年 | 215篇 |
1995年 | 126篇 |
1994年 | 130篇 |
1993年 | 119篇 |
1992年 | 46篇 |
1991年 | 46篇 |
1990年 | 47篇 |
1989年 | 63篇 |
1988年 | 48篇 |
1987年 | 38篇 |
1986年 | 39篇 |
1985年 | 35篇 |
1984年 | 25篇 |
1983年 | 23篇 |
1982年 | 19篇 |
1981年 | 26篇 |
1980年 | 23篇 |
1979年 | 22篇 |
1978年 | 34篇 |
1977年 | 47篇 |
1976年 | 127篇 |
1975年 | 28篇 |
1974年 | 19篇 |
排序方式: 共有4232条查询结果,搜索用时 15 毫秒
51.
JD Wagner L Zhang JK Williams TC Register DM Ackerman B Wiita TB Clarkson MR Adams 《Canadian Metallurgical Quarterly》1996,16(12):1473-1480
OBJECTIVES: To assess retinal complications and to identify risk factors for retinal complications following aqueous shunt procedures. MATERIALS AND METHODS: Records of 38 consecutive aqueous shunt procedures that were performed on 36 patients at the Eye Institute of the Medical College of Wisconsin, Milwaukee, from June 1993 to March 1995 (minimum follow-up, 6 months) were reviewed. The mean +/- SD follow-up was 11.4 +/- 5.2 months (median, 10.5 months). RESULTS: Twelve patients (32%) had the following retinal complications: 4 serous choroidal effusions (10%) that required drainage, 3 suprachoroidal hemorrhages (8%), 2 vitreous hemorrhages (5%), 1 rhegmatogenous retinal detachment (3%), 1 endophthalmitis (3%), and 1 scleral buckling extrusion (3%). Surgical procedures for retinal complications were required in 8 (67%) of these 12 patients. Visual acuity decreased 2 lines or more in 9 (75%) of these 12 patients. The median onset of a postoperative retinal complication was 12.5 days, with 10 patients (83%) experiencing complications within 35 days. Serous choroidal effusions developed in 10 other patients (26%), and these effusions resolved spontaneously. Visual acuity decreased 2 lines or more in 2 (20%) of these additional 10 patients. Patients who experienced serious retinal complications were significantly older, had a higher rate of hypertension, and postoperative ocular hypotony. Serious retinal complications were distributed evenly among patients with Krupin valves with discs and Molteno and Baerveldt devices. Experience with the Ahmed glaucoma valve implant was limited. CONCLUSION: Aqueous shunt procedures may be associated with significant retinal complications and subsequent visual loss. 相似文献
52.
PURPOSE: Retrospective studies suggest that adult patients with intractable epilepsy may have a history of febrile seizures in childhood. Risk factors for a febrile seizure may include the rate of increase in the core temperature (T-core), its peak (Tmax), the duration of the temperature increase, or an underlying brain pathology. Recently, neuronal migration disorders (NMD) have been diagnosed with increasing frequency in patients with epilepsy, but the link between NMD, febrile seizures, and epilepsy is unclear. We studied rat pups rendered hyperthermic to ascertain the incidence of seizures, mortality, and extent of hippocampal cell loss in each group. METHODS: We exposed 14-day-old rat pups with experimentally induced NMD (n = 39) and age-matched controls (n = 30) to hyperthermia (core body temperature > 42 degrees C). RESULTS: The incidence of hyperthermia-induced behavioral seizures and mortality rate were significantly higher in rats with NMD than in controls (p < 0.05). The longer duration of hyperthermia resulted in a higher incidence of behavioral seizures and higher mortality rate (p < 0.05). In rats with NMD, hyperthermia resulted in hippocampal pyramidal cell loss independent of seizure activity; the extent of neuronal damage correlated positively with the duration of hyperthermia. In control rats, occasional neuronal loss and astrocytosis occurred only after prolonged hyperthermia. CONCLUSIONS: In immature rats, NMD lower the threshold to hyperthermia-induced behavioral seizures and hyperthermia in the presence of NMD may cause irreversible hippocampal neuronal damage. 相似文献
53.
We analysed rates of detection for smear abnormalities in 255,000 women served by the Bristol screening programme. The programme began in 1966 with the aim of eradicating the 30-40 deaths each year in Bristol from cervical cancer. Organisation has been good and population uptake has been high for the past 15 years. Records were computerised in 1977. During the 1988 to 1993 screening round, 225,974 women were tested. New smear abnormalities were found in 15,551, of whom nearly 6000 were referred for colposcopy. These numbers are excessively high in comparison with the incidence of the malignancy we are trying to prevent. The effect of screening on death rates in Bristol is too small to detect. Our conclusion is that despite good organisation of the service, much of our effort in Bristol is devoted to limiting the harm done to healthy women and to protecting our staff from litigation as cases of serious disease continue to occur. The real lesson from 30 years' cervical screening is that no matter how obvious the predicted benefit may seem for any screening test, introduction should never take place without adequate prior evaluation of both positive and negative effects in controlled trials. 相似文献
54.
Solar cells based on hydrogenated amorphous silicon are now made from a variety of materials including alloys and microcrystalline
films. Research aimed at improving cell efficiency should emphasize studies of alloys and metastable defects. We discuss several
research topics related to the growth, structure, and electronic properties of these materials, which should lead to improved
photovoltaic devices. 相似文献
55.
GF Wagner RC Fargher C Milliken BA McKeown DH Copp 《Canadian Metallurgical Quarterly》1993,93(2):185-191
The aims of this study were to determine the most appropriate duration for the measurement of the maximal accumulated O2 deficit (MAOD), which is analogous to the anaerobic capacity, to ascertain the effects of mass, fat free mass (FFM), leg volume (Vleg) and lower body volume (V1b) on anaerobic test performance, to examine the reproducibility for peak power output (Wpeak) or maximal anaerobic power using an air-braked cycle ergometer and to produce approximations for the percentages of aerobic and anaerobic metabolism during exercise of short duration but high intensity. A group of 12 endurance trained cyclists [mean age 25.1 (SD 4.6) years; mean body mass 73.43 (SD 7.12) kg; mean maximal oxygen consumption 5.12 (SD 0.35) l.min-1; mean body fat 12.5 (SD 4.1) %] accordingly performed four counterbalanced treatments of 45, 60, 75 and 90 s of maximal cycling on an air-braked ergometer. The mean O2 deficit of 3.52 l for the 45-s treatment was significantly less (P < 0.01) than those for the 60 (3.75 l), 75 (3.80 l) and 90-s (3.75 l) treatments. These data therefore indicate that in predominantly aerobically trained subjects the O2 deficit attains a plateau after 60 s of maximal cycling on an air-braked ergometer. Statistically significant interclass correlation coefficients (P < 0.05) between the anthropometric variables (mass, FFM, Vleg and Vlb) and Wpeak or maximal anaerobic power (0.624-0.748) and MAOD (ml) or anaerobic capacity (0.666-0.772) furthermore would suggest the relevance of taking into account muscle mass during anaerobic tests.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
56.
The exposure to paired electric impulses and vibromassage promotes completeness of repair in the treatment of injured peripheral nerves of the limb. The effect is achieved due to marked stimulation of myelinization and differentiation of the nerve fibers, regeneration of the nerve system in the denervated muscle. 相似文献
57.
Common Assembly Language for Microprocessors (CALM) is a set of notations, independent of any manufacturer but strongly inspired by the best existing assemblers.
The paper contains a discussion of assembler addressing modes and their expressions in CALM. A program example of the Bubble Sort subroutine written for 4 processors (hypothetical, 8085, 8086, 68000) gives an idea of CALM programs. 相似文献
58.
59.
60.
RE Droleskey PJ Holman KA Waldrup DE Corrier GG Wagner 《Canadian Metallurgical Quarterly》1993,79(3):424-434
Babesia odocoilei continuously cultured in white-tailed deer (Odocoileus virginianus) erythrocytes was examined by transmission and scanning electron microscopy. Merozoites, trophozoites, intermediate-stage forms, and dividing forms were observed. Merozoites possessed a single nucleus, inner membrane complex, rhoptries, free ribosomes, rough endoplasmic reticulum, and single membrane-bound vesicles. Trophozoites lacked an inner membrane complex and rhoptries. Intermediate stages were characterized by distinct segments of inner membrane complex. Dividing forms ranged from cells with an elongated nucleus to mature daughter cells joined by a ringlike structure. Babesia odocoilei was characterized by its close proximity to the erythrocyte membrane, membranous structures resembling feeding organelles, and reproduction via a method resembling budding sensu stricto. 相似文献