全文获取类型
收费全文 | 6673篇 |
免费 | 598篇 |
国内免费 | 17篇 |
专业分类
电工技术 | 75篇 |
综合类 | 13篇 |
化学工业 | 1884篇 |
金属工艺 | 120篇 |
机械仪表 | 140篇 |
建筑科学 | 280篇 |
矿业工程 | 15篇 |
能源动力 | 188篇 |
轻工业 | 752篇 |
水利工程 | 39篇 |
石油天然气 | 14篇 |
无线电 | 730篇 |
一般工业技术 | 1245篇 |
冶金工业 | 652篇 |
原子能技术 | 83篇 |
自动化技术 | 1058篇 |
出版年
2023年 | 36篇 |
2022年 | 94篇 |
2021年 | 123篇 |
2020年 | 121篇 |
2019年 | 153篇 |
2018年 | 183篇 |
2017年 | 201篇 |
2016年 | 231篇 |
2015年 | 208篇 |
2014年 | 299篇 |
2013年 | 464篇 |
2012年 | 358篇 |
2011年 | 471篇 |
2010年 | 373篇 |
2009年 | 352篇 |
2008年 | 362篇 |
2007年 | 274篇 |
2006年 | 277篇 |
2005年 | 228篇 |
2004年 | 209篇 |
2003年 | 199篇 |
2002年 | 178篇 |
2001年 | 126篇 |
2000年 | 128篇 |
1999年 | 103篇 |
1998年 | 118篇 |
1997年 | 96篇 |
1996年 | 114篇 |
1995年 | 77篇 |
1994年 | 98篇 |
1993年 | 79篇 |
1992年 | 61篇 |
1991年 | 47篇 |
1990年 | 62篇 |
1989年 | 52篇 |
1988年 | 36篇 |
1987年 | 40篇 |
1986年 | 41篇 |
1985年 | 48篇 |
1984年 | 51篇 |
1983年 | 43篇 |
1982年 | 41篇 |
1981年 | 37篇 |
1980年 | 35篇 |
1979年 | 47篇 |
1977年 | 44篇 |
1976年 | 31篇 |
1975年 | 24篇 |
1974年 | 24篇 |
1973年 | 24篇 |
排序方式: 共有7288条查询结果,搜索用时 15 毫秒
31.
Shiffman Saul; Paty Jean A.; Gnys Maryann; Kassel Jon D.; Elash Celeste 《Canadian Metallurgical Quarterly》1995,14(4):301
From previous studies, chippers (very light, long-time cigarette smokers) seem not to be nicotine dependent, despite decades of smoking. The effect of tobacco deprivation on chippers' withdrawal reactions was examined. Matched groups of 26 chippers and 25 regular smokers were studied while abstaining or smoking for 2-day blocks, with assessments administered 5 times daily by palm-top computers. As hypothesized, chippers showed no changes as a result of nicotine deprivation. In contrast, regular smokers demonstrated distinct changes in craving, mood, arousal, and sleep disturbance. The computers also tested participants' cognitive performance. Unlike chippers, regular smokers' performance on complex tasks was slower under deprivation; the effect could not be explained by changes in motor performance or simple reaction time. Results suggest performance may have been improved by nicotine rather than worsened by withdrawal. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
32.
33.
The equivalent inclusion method (EIM) assuming linear elasticity is used to calculate the mechanical interactions between spherical rubber particles in an amorphous matrix, as in a rubber toughened polymer. The influences of the various calculation parameters are examined and it is shown that the method can provide reliable results with regard to the level of hydrostatic stress in the particles. Damage of the material is simulated by replacing the most stressed particles by voids. Numerical simulations for several hundreds of interacting particles give information on the kinetics and spatial organisation of the damage. It appears that, as the volume fraction of particles increases from 10 to 20%, the spatial configuration of the damage evolves from a localised to a diffuse mode. These results are discussed in relation to the efficiency of rubber toughening. 相似文献
34.
Genero Nancy P.; Miller Jean B.; Surrey Janet; Baldwin Lawrence M. 《Canadian Metallurgical Quarterly》1992,6(1):36
In an initial validation study of the Mutual Psychological Development Questionnaire (MPDQ), a measure of perceived mutuality in close relationships, 345 respondents completed the scale for spouse or partner and friend relationships. Results indicated high interitem reliability. Construct and concurrent validity were demonstrated. MPDQ ratings were correlated with adequacy of social support, relationship satisfaction, and cohesion. Ratings correlated negatively with depression. Low spouse or partner mutuality was predictive of significant depressive symptoms in women but not in men. In a 2nd study, 81 respondents completed the scale at 2 time points. Test–retest reliability was satisfactory, and high interitem consistency was replicated. The substantive meaning of these findings, gender differences, and possible future research applications of the MPDQ are disscussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
35.
In the first half of the 21st century, a redistribution of the energy data should occur, where nuclear will play a more important role, particularly as coal will become more and more costly to extract.On a worldwide basis, the unability of oil to be replaced in some areas like transportation, and the difficulty of developing countries to find substitutes for this energy source, could also lead developed countries to keep the energy resources for a better utilization, and give the countries which have no access to other resources, a possibility to develop.Thus, France has extensively enhanced nuclear energy for its electricity production, and, consequently, makes the necessary efforts for the knowledge of the whole fuel cycle. 相似文献
36.
This article allows the determination of the induced perturbations at the ends of the coaxial line in wide frequency band enough. The perturbation source is a current direct point injection into the cable screen in any position. For this, we have applied the theory of the state variables, with foundation of the quasi-TEM approximation, in order to simulate the coaxial line above a ground level that has a finished conductivity. This allows us to supply the current and voltage expressions at the ends of the line as their analytic forms for any conditions of charge. Next, the elaborate objective is to verify experimentally on concrete applications if the test obtained results confirm the theoretical expectations supplied by calculation code finalizing. 相似文献
37.
Surendra P. Verma Jean R. Philippot Bernard Bonnet Josette Sainte-Marie Yves Moschetto Donald F. H. Wallach 《Lipids》1985,20(12):890-896
Raman and resonance Raman spectra of plasma lipoproteins ± malondialdehyde were studied at concentrations which block the
normal receptor-mediated uptake by cells. The strong resonance Raman bands at about 1010, 1162 and 1530 cm−1, due to the presence of carotenoids in the lipoproteins, are envisaged as structural probes. High resolution resonance Raman
spectra of the 1500–1600 cm−1 region reveal multiple features suggesting the coexistence of several structural populations of β-carotene whose precise
assignment is complex. When plasma lipoproteins are reacted with malondialdehyde, a complex change occurs in the resonance
Raman banding of β-carotene in the 1500–1600 cm−1 region. Malonaldehyde (MDA) also modifies the acoustical region (70–200 cm−1 of low density lipoprotein (LDL) lipids. We suggest that malondialdehyde association with plasma lipoproteins alters the
lipid structure via apoprotein or apoprotein/lipid associations. 相似文献
38.
Jean Chilo 《电信纪事》1985,40(3-4):135-144
The author presents the theoretical methods for modeling and transient analysis of coupled transmission lines. For an interconnecting bus used in GaAs technology with a 30 ps rise time activating signal and 3 mm length, he shows the great importance of coupling: signal distortion on the activated lines and parasiting on the unactivated ones. He studies the reduction of these phenomena with use of earth lines or addition of a second ground plane over the lines. 相似文献
39.
F Hau 《Canadian Metallurgical Quarterly》1993,36(3):297-304
PURPOSE: To determine the efficacy, dose-response relationship, and safety of 30, 60, and 90 mg of a single intravenous dose of an aminobisphosphonate, pamidronate (APD), for the treatment of moderate to severe hypercalcemia of malignancy. PATIENTS AND METHODS: Patients with histologically proven cancer and a corrected serum calcium level of at least 12.0 mg/dL after 48 hours of normal saline hydration were enrolled in a double-blind, multicenter, randomized clinical trial. Pamidronate in 30-, 60-, or 90-mg doses was administered as a single 24-hour infusion. Serum calcium corrected for albumin, urine hydroxyproline, and calcium excretion, and serum parathyroid hormone (PTH) (1-84) were determined before and after pamidronate therapy. RESULTS: Thirty-two men and 18 women entered the study. A dose-response relationship for normalization of corrected serum calcium was seen after pamidronate administration. Corrected serum calcium normalized in 40% of patients who received 30 mg, in 61% of patients who received 60 mg, and in 100% of patients who received 90 mg of pamidronate. The decline in the serum calcium level was associated with decreased osteoclastic skeletal resorption evidenced by a decrease in urine calcium and hydroxyproline excretion. Among those with a normalized corrected serum calcium level, the mean (median) duration of normalization of the corrected serum calcium value was 9.2 (4), 13.3 (5), and 10.8 (6) days in the 30-, 60-, and 90-mg treatment groups, respectively. The response of hypercalcemia to pamidronate was not significantly influenced by the presence of skeletal metastases. PTH 1-84, suppressed in patients on entry into this study, increased to a greater extent in those patients with osteolytic skeletal metastases compared with those with humoral hypercalcemia of malignancy. Clinical improvement, including improved mental status and decreased anorexia, accompanied the decline in the corrected serum calcium level in all three treatment groups. Side effects included low-grade fever, asymptomatic hypocalcemia, hypomagnesemia, and hypophosphatemia. CONCLUSIONS: A single-dose infusion of 60 to 90 mg of pamidronate was highly effective and well tolerated and normalized corrected serum calcium in nearly all patients (61% to 100%) with hypercalcemia of malignancy. 相似文献
40.
Ockene Judith K.; Kristeller Jean; Pbert Lori; Hebert James R.; Luippold Rose; Goldberg Robert J.; Landon Joan; Kalan Kathryn 《Canadian Metallurgical Quarterly》1994,13(3):278
Patterns of smoking cessation using 6- and 12-mo follow-up data are reported for 1,261 primary care patients randomized to 3 physician-delivered smoking interventions: advice only (AO), counseling (CI), and counseling plus availability of nicotine-containing gum (CI?+?NCG). One-week point-prevalence cessation rates at 12 mo did not differ among the interventions: AO (15.2%), CI (12.9%) and CI?+?NCG (16.7%). However, maintained cessation rates (abstinent at both 6 and 12 mo) increased with intervention intensity: AO (6.0%), CI (7.8%), and CI?+?NCG (10.0%): Test of trend χ–2?=?5.06, p?=?.02. CI?+?NCG was significantly higher than AO (p?=?.02). The findings support the following conclusions: Brief physician delivered intervention with availability of nicotine-containing gum can have a beneficial long-term effect on smoking cessation, and cohort data as well as point-prevalence rates are important when assessing the long-term impact of lifestyle interventions. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献