全文获取类型
收费全文 | 5264篇 |
免费 | 62篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 48篇 |
化学工业 | 392篇 |
金属工艺 | 69篇 |
机械仪表 | 57篇 |
建筑科学 | 124篇 |
矿业工程 | 15篇 |
能源动力 | 42篇 |
轻工业 | 295篇 |
水利工程 | 29篇 |
石油天然气 | 7篇 |
无线电 | 295篇 |
一般工业技术 | 451篇 |
冶金工业 | 3088篇 |
原子能技术 | 19篇 |
自动化技术 | 399篇 |
出版年
2021年 | 29篇 |
2019年 | 20篇 |
2018年 | 25篇 |
2017年 | 33篇 |
2016年 | 18篇 |
2015年 | 32篇 |
2014年 | 58篇 |
2013年 | 150篇 |
2012年 | 103篇 |
2011年 | 102篇 |
2010年 | 57篇 |
2009年 | 61篇 |
2008年 | 89篇 |
2007年 | 106篇 |
2006年 | 103篇 |
2005年 | 72篇 |
2004年 | 79篇 |
2003年 | 88篇 |
2002年 | 75篇 |
2001年 | 58篇 |
2000年 | 54篇 |
1999年 | 144篇 |
1998年 | 914篇 |
1997年 | 533篇 |
1996年 | 359篇 |
1995年 | 201篇 |
1994年 | 179篇 |
1993年 | 220篇 |
1992年 | 69篇 |
1991年 | 69篇 |
1990年 | 75篇 |
1989年 | 69篇 |
1988年 | 70篇 |
1987年 | 55篇 |
1986年 | 55篇 |
1985年 | 65篇 |
1984年 | 28篇 |
1983年 | 24篇 |
1982年 | 32篇 |
1981年 | 54篇 |
1980年 | 48篇 |
1979年 | 28篇 |
1978年 | 31篇 |
1977年 | 116篇 |
1976年 | 190篇 |
1975年 | 33篇 |
1974年 | 24篇 |
1973年 | 28篇 |
1972年 | 19篇 |
1971年 | 18篇 |
排序方式: 共有5330条查询结果,搜索用时 15 毫秒
51.
52.
Oxygen mass transfer calculations in large arteries 总被引:1,自引:0,他引:1
Parkinsonism is characterised by overactive glutamatergic transmission in the cortico-striatal and subthalamo-medial pallidal pathways. Local blockade of glutamatergic transmission in these pathways can alleviate parkinsonian symptoms. The effectiveness of the treatment, however, is often limited by the simultaneous appearance of unwanted side-effects. These side-effects, including ataxia and dissociative anaesthesia, are particularly problematic when N-methyl-D-aspartate (NMDA) antagonists are used. In an attempt to overcome these problems we have attempted to manipulate excitatory amino acid (EAA)-mediated neurotransmission indirectly by targeting the NMDA receptor associated modulatory sites. We review evidence which demonstrates that antagonists for both the NMDA associated glycine and polyamine sites can reverse parkinsonian symptoms when injected intra-cerebrally in both MPTP-treated and bilateral 6-OHDA lesioned marmosets without eliciting unwanted side-effects. We further review preliminary data which suggest that ifenprodil, a polyamine site antagonist, has striking anti-parkinsonian actions in the marmoset. Potential mechanisms of action underlying these effects are discussed in terms of NMDA receptor subtypes and the neuroanatomical locus of action. The anti-parkinsonian efficacy of intra-striatally administered EAA antagonists leads us to question the view of dopamine acting in the striatum as a simple neuromodulator. 相似文献
53.
Conditioned eyeblink responses are presumably learned in the cerebellum and relayed to motoneurons by way of the red nucleus. Projections from the red nucleus to cerebellar cortex (Larsell's lobule HVI) could be important for shaping temporally adaptive features of the conditioned response. Rabbits that had pipettes containing wheat germ agglutinated horseradish peroxidase (WGA-HRP) implanted unilaterally into HVI showed retrograde labeling of neurons within subregions of the contralateral red nucleus implicated in eyeblink conditioning by lesioning and recording studies. Retrogradely labeled neurons were also observed in the pontine nuclei, inferior olive, and spinal trigeminal nucleus pars oralis. Projections to HVI provide a possible neural substrate for implementing time-derivative computational models of learning in the cerebellum. Time-derivative models are capable of describing the timing and topography of conditioned responses. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
54.
55.
Evaluated the efficacy of outpatient group treatment of chronic pain and the effect of spouse involvement in treatment in chronic pain patients ranging in age from 23 to 69 yrs who were randomly assigned to couples group treatment (n?=?17), patient-only group treatment (n?=?14), or waiting-list controls (n?=?12). 29 Ss had low back pain; the remaining Ss reported pain in the knee, arm, leg, hip, head, and phantom limb. The Ss completed the MMPI—168 and measures of health-related psychosocial and physical dysfunction and marital satisfaction. Results indicate that the 16-hr cognitive-behavioral program produced reductions in pain, somatization, spouse-observed pain behavior, physical and psychosocial dysfunction, spouse-rated dysfunction, and utilization of health care resources. Depression was not affected by treatment. Spouse involvement did not facilitate response to treatment on any variables. Also, Ss in the individual condition only showed improved marital satisfaction. All treatment gains were maintained at 3-mo to 7-mo follow-ups. Results indicate that brief outpatient treatment can significantly ameliorate chronic pain problems, and spouse involvement is not essential for a positive response to treatment. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
56.
F Petersen H Z?hner JW Metzger S Freund RP Hummel 《Canadian Metallurgical Quarterly》1993,46(7):1126-1138
During germination spores of Streptomyces viridochromogenes NRRL B-1551 excrete a compound, germicidin, which has an inhibitory effect on the germination of its own arthrospores at a concentration as low as 200 pM (40 pg/ml). At higher concentrations germicidin inhibits porcine Na+/K(+)-activated ATPase and retards the germination of the cress Lepidium sativum. Germicidin is the first known autoregulative inhibitor of spore germination in the genus Streptomyces and was isolated from the supernatant of germinated spores, but also from the supernatant of the submerged culture. Spectroscopic analysis and derivatization reactions revealed germicidin to be 6-(2-butyl)-3-ethyl-4-hydroxy-2-pyrone (C11H16O3). Crude isolates of germicidin from the supernatant of submerged culture, but not from the spores, contained a second, structurally very similar compound (C10H14O3), in which in contrast to germicidin a 2-propyl instead of the 2-butyl chain was bound to C-6 and which did not show any activity in the germination and ATPase assay. The germination assay was evaluated as a new screening model for specifically active compounds. 相似文献
57.
58.
When Bonner & Moore was formed in 1956, few-if any-other firms were offering computer consulting services to private industry. Over the years, Bonner & Moore's software development and computer modeling projects took the company far and wide, from Texas oil refineries to the other side of the globe. Its computer services created a solid financial success. 相似文献
59.
60.
Bench-scale reactor experiments were performed to study the dissolution of a binary naphthalene-in-nonane mixture nonaqueous phase liquid (NAPL) pool over a wide range of average pore water velocities, vx (≈0.1–60 m/day). Experimental NAPL pool dissolution flux values were determined using a steady-state mass balance approach. The experimental flux data were compared to model predictions made assuming either local equilibrium or mass-transfer limited conditions. The local equilibrium model could describe the trends in the average effluent concentration and dissolution flux with 0.110?m/day. Data determined to be under mass-transfer limited conditions were fit to the nonequilibrium model to estimate values for an overall mass-transfer coefficient. The calculated overall mass-transfer coefficients had an average value of 0.407 m/day and showed no correlation with vx, probably due to mass-transfer resistance becoming dominated by the diffusional resistance in the NAPL. These results suggest that the nonequilibrium approach is better suited for describing high velocity (vx>10?m/day) dissolution of multicomponent NAPL pools, and that flushing of groundwater at very high velocities may not be an effective approach for enhancing NAPL-pool dissolution flux. 相似文献