全文获取类型
收费全文 | 2362篇 |
免费 | 34篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 29篇 |
化学工业 | 179篇 |
金属工艺 | 27篇 |
机械仪表 | 29篇 |
建筑科学 | 7篇 |
能源动力 | 27篇 |
轻工业 | 114篇 |
水利工程 | 1篇 |
石油天然气 | 7篇 |
无线电 | 231篇 |
一般工业技术 | 197篇 |
冶金工业 | 1486篇 |
原子能技术 | 5篇 |
自动化技术 | 61篇 |
出版年
2023年 | 5篇 |
2022年 | 14篇 |
2021年 | 33篇 |
2020年 | 16篇 |
2019年 | 21篇 |
2018年 | 25篇 |
2017年 | 23篇 |
2016年 | 19篇 |
2015年 | 14篇 |
2014年 | 31篇 |
2013年 | 50篇 |
2012年 | 24篇 |
2011年 | 40篇 |
2010年 | 46篇 |
2009年 | 27篇 |
2008年 | 30篇 |
2007年 | 21篇 |
2006年 | 18篇 |
2005年 | 26篇 |
2004年 | 30篇 |
2003年 | 14篇 |
2002年 | 11篇 |
2001年 | 16篇 |
2000年 | 20篇 |
1999年 | 73篇 |
1998年 | 464篇 |
1997年 | 276篇 |
1996年 | 193篇 |
1995年 | 110篇 |
1994年 | 110篇 |
1993年 | 100篇 |
1992年 | 30篇 |
1991年 | 39篇 |
1990年 | 43篇 |
1989年 | 47篇 |
1988年 | 35篇 |
1987年 | 21篇 |
1986年 | 29篇 |
1985年 | 21篇 |
1984年 | 10篇 |
1983年 | 8篇 |
1982年 | 13篇 |
1981年 | 17篇 |
1980年 | 27篇 |
1979年 | 4篇 |
1978年 | 9篇 |
1977年 | 40篇 |
1976年 | 86篇 |
1975年 | 10篇 |
1966年 | 2篇 |
排序方式: 共有2400条查询结果,搜索用时 31 毫秒
1.
Mining high utility itemsets (HUIs) from transaction databases considers such factors as the unit profit and quantity of purchased items. Two-phase tree-based algorithms transform a database into compressed tree structures and generate candidate patterns through a recursive pattern-growth procedure. This procedure requires a lot of memory and time to construct conditional pattern trees. To address this issue, this study employs two compressed tree structures, namely, Utility Count Tree and String Utility Tree, to enumerate valid patterns and thus promote fast utility computation. Furthermore, the study presents an algorithm called single-phase utility computation (SPUC) that leverages these two tree structures to mine HUIs in a single phase by incorporating novel pruning strategies. Experiments conducted on both real and synthetic datasets demonstrate the superior performance of SPUC compared with IHUP, UP-Growth, and UP-Growth+ algorithms. 相似文献
2.
S V Bhat 《Bulletin of Materials Science》1994,17(7):1271-1285
When examined using continuous wave electron paramagnetic resonance and nuclear magnetic resonance spectrometers, the highT
c superconductors give rise to intense, low field, ‘non-resonant’ absorption signals in the superconducting state. This phenomenon
can be used as a highly sensitive, contactless technique for the detection and characterization of superconductivity even
in samples containing only minute amounts of the superconducting phase. Further, it can also be applied to the determination
of material parameters of interest such asJ
c andH
c2 in addition to being a powerful way of distinguishing between weak-link superconductivity and bulk superconductivity. The
details of these aspects are discussed. 相似文献
3.
SG Bryant 《Canadian Metallurgical Quarterly》1996,53(19):2339-40, 2343
4.
SG Rijpkema RG Herbes N Verbeek-De Kruif JF Schellekens 《Canadian Metallurgical Quarterly》1996,117(3):563-566
Epiglottic disruption is an uncommon injury usually associated with significant supraglottic trauma. This injury may be overlooked because of the difficulty in examining the larynx or other associated severe injuries. We present two cases of clinically unsuspected epiglottic disruption that were first seen on MR images of the neck. 相似文献
5.
G
V Vijaya T Gireesh Gajanan S Bhat 《Journal of the science of food and agriculture》2002,82(5):493-496
The effect of enzymatic hydrolysis of proteins in milk using neutrase on the growth of the probiotic strain Bifidobacterium bifidus was evaluated by estimation of microbial growth, acidity, viscosity and flavour production. A significant increase in the growth of B bifidus was observed in neutrase‐hydrolysed milk. The setting time of bifidus‐cultured milk was advanced by about 12 h at 5% degree of hydrolysis. Enzymatic hydrolysis of proteins prior to cultivation also significantly increased the viscosity of the product. An approximately 60% increase in viscosity of the product was observed in neutrase‐hydrolysed milk. Production of steam‐volatile monocarbonyls as an indication of development of flavour was also higher in neutrase‐hydrolysed milk. The concentration of steam‐volatile monocarbonyls was 2.47 µmol per 100 ml in neutrase‐hydrolysed milk but only 1.84 µmol per 100 ml in control milk at the setting point of the curd. © 2002 Society of Chemical Industry 相似文献
6.
SA Khotimchenko VM Kodentsova IA Alekseeva SG Vlaskina OA Vrzhesinskaia AA Sokol''nikov LA Kharitonchik IP Aleshko-Ozhevskií LV Sheviakova 《Canadian Metallurgical Quarterly》1997,43(3):158-164
Gamma delta T-Cells represent a minor subpopulation of T-lymphocytes in man and their role in normal and diseased human skin is unknown. This article is a comprehensive review of T-lymphocytes bearing the gamma delta T-cell receptor in normal and pathological human skin. Firstly, we have documented the occurrence of gamma delta T-cells in normal skin and in a range of reactive and malignant skin conditions. We have then discussed the experimental findings regarding the repertoire used by gamma delta T-cells in normal human skin and in cutaneous disorders with an increased percentage of gamma delta T-cells. 相似文献
7.
8.
N. Nishiyama C. Caneau S. Tsuda G. Guryanov M. Hu R. Bhat Chung-En Zah 《Photonics Technology Letters, IEEE》2005,17(8):1605-1607
Error-free transmission through 10-km single-mode fiber at 10 Gb/s under -13-dB optical reflections has been demonstrated for the first time using a directly modulated 1.3-/spl mu/m InP-based VCSEL without any optical isolator. The 13-GHz relaxation oscillation frequency and stable polarization suppresses relative intensity noise degradation under optical reflection. Only 1-dB error-free power penalty has been observed with optical reflection set with the worst polarization direction. 相似文献
9.
Human immunodeficiency virus (HIV) infection of the thymus could have profound effects on development of the immune response, particularly in children. We and others have established that in addition to infecting and depleting CD4-bearing thymocytes, functional HIV proviruses are found in thymocytes lacking surface CD4 expression. Using in vitro thymocyte cultures, we show that neither HIV-mediated down regulation of CD4 nor CD4-independent infection contributes to the localization of HIV in cells lacking the primary virus receptor. Rather, infection of a CD4-positive precursor cell (CD4 positive/CD8 positive) with subsequent differentiation into a mature CD4-negative phenotype results in productively infected CD4-negative cells. This novel mechanism may contribute to pathogenesis by distributing viral sequences into functional subsets of T cells typically refractory to HIV infection and could account for the presence of viral DNA in CD8-positive lymphocytes recently observed in patients. 相似文献
10.
The 20-kDa protein gene is androgen regulated in rat ventral prostate. Intron 1 contains a 130-base pair complex response element (D2) that binds androgen (AR) and glucocorticoid receptor (GR) but transactivates only with AR in transient cotransfection assays in CV1 cells using the reporter vector D2-tkCAT. To better understand the function of this androgen-responsive unit, nuclear protein interactions with D2 were analyzed by DNase I footprinting in ventral prostate nuclei of intact or castrated rats and in vitro with ventral prostate nuclear protein extracts from intact, castrated, and testosterone-treated castrated rats. Multiple androgen-dependent protected regions and hypersensitive sites were identified in the D2 region with both methods. Mobility shift assays with 32P-labeled oligonucleotides spanning D2 revealed specific interactions with ventral prostate nuclear proteins. Four of the D2-protein complexes decreased in intensity within 24 h of castration. UV cross-linking of the androgen-dependent DNA binding proteins identified protein complexes of approximately 140 and 55 kDa. The results demonstrate androgen-dependent nuclear protein-DNA interactions within the complex androgen response element D2. 相似文献