全文获取类型
收费全文 | 45945篇 |
免费 | 2534篇 |
国内免费 | 42篇 |
专业分类
电工技术 | 346篇 |
综合类 | 29篇 |
化学工业 | 8751篇 |
金属工艺 | 921篇 |
机械仪表 | 910篇 |
建筑科学 | 1406篇 |
矿业工程 | 98篇 |
能源动力 | 970篇 |
轻工业 | 6119篇 |
水利工程 | 407篇 |
石油天然气 | 189篇 |
武器工业 | 4篇 |
无线电 | 2606篇 |
一般工业技术 | 8480篇 |
冶金工业 | 10525篇 |
原子能技术 | 253篇 |
自动化技术 | 6507篇 |
出版年
2023年 | 420篇 |
2022年 | 400篇 |
2021年 | 1048篇 |
2020年 | 892篇 |
2019年 | 836篇 |
2018年 | 1788篇 |
2017年 | 1794篇 |
2016年 | 1855篇 |
2015年 | 1332篇 |
2014年 | 1703篇 |
2013年 | 3360篇 |
2012年 | 2675篇 |
2011年 | 2542篇 |
2010年 | 2090篇 |
2009年 | 1817篇 |
2008年 | 1979篇 |
2007年 | 1688篇 |
2006年 | 1242篇 |
2005年 | 1000篇 |
2004年 | 967篇 |
2003年 | 860篇 |
2002年 | 780篇 |
2001年 | 516篇 |
2000年 | 517篇 |
1999年 | 651篇 |
1998年 | 3382篇 |
1997年 | 2041篇 |
1996年 | 1341篇 |
1995年 | 800篇 |
1994年 | 701篇 |
1993年 | 680篇 |
1992年 | 238篇 |
1991年 | 258篇 |
1990年 | 246篇 |
1989年 | 237篇 |
1988年 | 213篇 |
1987年 | 187篇 |
1986年 | 202篇 |
1985年 | 256篇 |
1984年 | 235篇 |
1983年 | 174篇 |
1982年 | 208篇 |
1981年 | 229篇 |
1980年 | 195篇 |
1979年 | 161篇 |
1978年 | 155篇 |
1977年 | 234篇 |
1976年 | 467篇 |
1975年 | 126篇 |
1973年 | 118篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
111.
112.
Loranger Michel; Pépin Michel; Gignac Guy; Benoit Geneviève 《Canadian Metallurgical Quarterly》1995,36(1):59
Presents results of 3 studies on the psychometric properties of the LP-ABC (M. Loranger and M. Pépin, 1993), a French-language instrument for assessing general functioning in adults with mental retardation. The studies involved a total of 299 male and female Canadian adults with mental retardation. Results confirm the internal consistency, construct validity, criterion validity, discriminant validity, interrater reliability, and test–retest reliability of the LP-ABC. (English abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
113.
114.
J Sánchez A Torres J Serrano J Román C Martín L Pérula F Martínez P Gómez 《Canadian Metallurgical Quarterly》1997,20(5):403-408
BACKGROUND: Locally advanced thyroid cancer invading the tracheal cartilage represents a difficult treatment dilemma during thyroidectomy. METHODS: A retrospective chart review was performed to determine the results of laryngotracheal resection or tracheal cartilage shave with adjuvant radiotherapy in patients with locally advanced thyroid cancer invading the upper airway. RESULTS: Of 597 patients undergoing thyroidectomy for thyroid cancer, 40 were found to have laryngotracheal invasion. Thirty-five patients with superficial invasion underwent cartilage shave procedures with adjuvant radiotherapy; five with full-thickness invasion underwent radical resection, including tracheal sleeve resection (n = 3) or total laryngectomy (n = 2). Histologic subtypes included papillary (n = 32), follicular (n = 2), Hurthle cell (n = 1), medullary (n = 3), and anaplastic (n = 2). Of the cartilage shave group, 25 are currently alive with no evidence of disease at a mean follow-up of 81 months (range 1-290). Six developed isolated local/regional recurrence and were managed with total laryngectomy (n = 1), tracheal resection (n = 1), cervical lymphadenectomy (n = 1), or repeat radiotherapy (n = 3). All six patients remain free of disease at a mean follow-up of 5 years. Of those who underwent initial laryngotracheal resection, four remain free of disease at a mean follow-up of 5 years. The rates of 10-year disease-free survival and overall survival for all patients were 47.9% (95% confidence interval [CI] 24.8, 71.0) and 83.9% (95% CI 70.3, 97.5), respectively. CONCLUSIONS: These data suggest that adequate management of thyroid cancer with laryngotracheal invasion can be achieved with a more conservative surgical approach and adjuvant radiotherapy, reserving more radical resections for extensive primary lesions or locally recurrent disease. 相似文献
115.
Coupling GIS with Hydrologic and Hydraulic Flood Modelling 总被引:6,自引:1,他引:5
Nunes Correia Francisco Castro Rego Filipe Da Grača Saraiva Maria Ramos Isabel 《Water Resources Management》1998,12(3):229-249
Geographic Information Systems (GIS) have been recognised as a powerful means to integrate and analyse data from various sources in the context of comprehensive floodplain management. As part of this comprehensive approach to floodplain management, it is very important to be able to predict the consequences of different scenarios in terms of flooded areas and associated risk. Hydrologic and hydraulic modelling plays a crucial role and there is much to gain in incorporating these modelling capabilities in GIS. This is still a rather complex task and research is being done on the full integration of these models. Interfacing between these models and GIS may be a very efficient way of overcoming the difficulties and getting very good results in terms of engineering practice. This paper presents results based on the use of Intergraph GIS coupled with Idrisi GIS. Using these two systems substantially increased the flexibility of using GIS as a tool for flood studies. A lumped (XSRAIN) and a distributed (OMEGA) hydrologic models were used to simulate flood hydrographs. The well known HEC-2 Hydraulic model was used to compute flooded areas. These models were applied in the Livramento catchment with very good results. The computation of flooded areas for different flood scenarios, and its representation in GIS, can be used in the assessment of affected property and associated damages. This is a very useful GIS-based approach to floodplain management. 相似文献
116.
117.
INTRODUCTION AND DEVELOPMENT: Multiple sclerosis (ME) is an inflammatory disease of the myelin of the central nervous system, the origin of which is still unknown. Genetic, infectious, immunological and environmental factors have all been blamed, but none of these factors on their own can explain the whole spectrum of this disease. Of the environmental factors, fat in the diet has given rise to most discussion. At the present time, it is known that polyunsaturated essential fatty acids form a part of biological membranes. A relationship has been found between the dietary fat consumed and the plasma levels and cell membrane content. CONCLUSIONS: The possible immuno-modulation function of these fatty acids justify rigorous evaluation of this hypothesis. 相似文献
118.
T González-Hernández B Mantolán-Sarmiento B González-González H Pérez-González 《Canadian Metallurgical Quarterly》1996,372(2):309-326
We have studied the GABAergic projections to the inferior colliculus (IC) of the rat by combining the retrograde transport of horseradish peroxidase (HRP) and immunohistochemistry for gamma-amino butyric acid (GABA). Medium-sized (0.06-0.14 microliter) HRP injections were made in the ventral part of the central nucleus (CNIC), in the dorsal part of the CNIC, in the dorsal cortex (DCIC), and in the external cortex (ECIC) of the IC. Single HRP-labeled and double (HRP-GABA)-labeled neurons were systematically counted in all brainstem auditory nuclei. Our results revealed that the IC receives GABAergic afferent connections from ipsi- and contralateral brainstem auditory nuclei. Most of the contralateral GABAergic input originates in the IC and the dorsal nucleus of the lateral lemniscus (DNLL). The dorsal region of the IC (DCIC and dorsal part of the CNIC) receives connections mostly from its homonimous contralateral region, and the ventral region from the contralateral DNLL. The commissural GABAergic projections originate in a morphologically heterogeneous neuronal population that includes small to medium-sized round and fusiform neurons as well as large and giant neurons. Quantitatively, the ipsilateral ventral nucleus of the lateral lemniscus is the most important source of GABAergic input to the CNIC. In the superior olivary complex, a smaller number of neurons, which lie mainly in the periolivary nuclei, display double labeling. In the contralateral cochlear nuclei, only a few of the retrogradely labeled neurons were GABA immunoreactive. These findings give us more information about the role of GABA in the auditory system, indicating that inhibitory inputs from different ipsi- and contralateral, mono- and binaural auditory brainstem centers converge in the IC. 相似文献
119.
E Béjar 《Canadian Metallurgical Quarterly》1996,50(1):1-12
Retinal cytosolic Ca2+/calmodulin-dependent protein kinase II (CaM KII) was isolated from hatched 6-wk chicken retinae by ultracentrifugation and affinity chromatography using calmodulin (CaM) and anti-CaM KII-alpha columns. Samples from different fractions were examined with SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and silver staining or immunoblotting. Comparisons were made between the final antibody affinity eluates from retina and forebrain. Silver-stained gels showed that multiple proteins were present in the antibody affinity eluates from retina, including major proteins of 178, 56, and 45 kDa and several minor proteins. Immunoblots revealed that CaM KII-alpha was present in eluates from the retina and forebrain. CaM KII-beta was present in the antibody eluate from forebrain but not retina. The latter subunit was present in the crude homogenates of the retina. Regarding the antibody eluate from retina, the possibility that the major 56 kDa protein was tubulin was ruled out, but protein tau (tau) and synapsin I were present. The presence of multiple proteins in the antibody affinity eluate indicates that these proteins were coisolated in a CaM KII-alpha-associated protein complex. The finding that protein tau and synapsin I are associated with retinal CaM KII provides further insight into the mechanisms underlying the function of the kinase in this tissue. The lack of cytosolic CaM KII-beta subunit in the antibody affinity eluate from retina is indicative of a brain region-specificity in subunit composition of the kinase. 相似文献
120.
The human obesity gene map: the 1997 update 总被引:1,自引:0,他引:1
An update of the human obesity gene map incorporating published results up to October 1997 is presented. Evidence from Mendelian disorders exhibiting obesity as a clinical feature; single-gene mutation rodent models; quantitative trait loci uncovered in human genome-wide scans and in crossbreeding experiments with mouse, rat, and pig models; association and case-control studies with candidate genes; and linkage studies with genes and other markers is reviewed. All chromosomal locations of the animal loci are converted into human genome locations based on syntenic relationships between the genomes. A complete listing of all of these loci reveals that all but chromosome Y of the 24 human chromosomes are represented. Some chromosomes show at least three putative loci related to obesity on both arms (1, 2, 6, 8, 11, and 20) and several on one chromosome arm only (3p, 4q, 5q, 7q, 12q, 13q, 15q, 15p, 22q, and Xq). Studies reporting negative association and linkage results are also listed, with the exception of the unlinked markers from genome-wide scans. 相似文献