全文获取类型
收费全文 | 6347篇 |
免费 | 606篇 |
国内免费 | 17篇 |
专业分类
电工技术 | 77篇 |
综合类 | 11篇 |
化学工业 | 1878篇 |
金属工艺 | 231篇 |
机械仪表 | 335篇 |
建筑科学 | 101篇 |
矿业工程 | 2篇 |
能源动力 | 350篇 |
轻工业 | 456篇 |
水利工程 | 9篇 |
石油天然气 | 5篇 |
武器工业 | 1篇 |
无线电 | 1116篇 |
一般工业技术 | 1446篇 |
冶金工业 | 253篇 |
原子能技术 | 41篇 |
自动化技术 | 658篇 |
出版年
2024年 | 4篇 |
2023年 | 68篇 |
2022年 | 102篇 |
2021年 | 176篇 |
2020年 | 135篇 |
2019年 | 184篇 |
2018年 | 226篇 |
2017年 | 215篇 |
2016年 | 251篇 |
2015年 | 228篇 |
2014年 | 318篇 |
2013年 | 408篇 |
2012年 | 478篇 |
2011年 | 521篇 |
2010年 | 427篇 |
2009年 | 422篇 |
2008年 | 368篇 |
2007年 | 284篇 |
2006年 | 264篇 |
2005年 | 216篇 |
2004年 | 200篇 |
2003年 | 229篇 |
2002年 | 183篇 |
2001年 | 127篇 |
2000年 | 135篇 |
1999年 | 129篇 |
1998年 | 141篇 |
1997年 | 84篇 |
1996年 | 74篇 |
1995年 | 53篇 |
1994年 | 45篇 |
1993年 | 30篇 |
1992年 | 43篇 |
1991年 | 24篇 |
1990年 | 28篇 |
1989年 | 29篇 |
1988年 | 12篇 |
1987年 | 18篇 |
1986年 | 14篇 |
1985年 | 8篇 |
1984年 | 13篇 |
1983年 | 12篇 |
1982年 | 3篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1978年 | 4篇 |
1977年 | 8篇 |
1976年 | 11篇 |
1975年 | 3篇 |
1970年 | 1篇 |
排序方式: 共有6970条查询结果,搜索用时 15 毫秒
31.
Po-An Sung Kwang-Cheng Chen 《Selected Areas in Communications, IEEE Journal on》1996,14(8):1583-1594
We generalize the multiuser (CDMA spread spectrum) communication systems to the fading environments. We first extend Verdu's (1986) conventional optimum receiver to Rayleigh-fading environments and then evaluate its performance. Having no knowledge of the received power at the receiving end, we therefore need an estimator to efficiently estimate the received signal strength of each user in fading environments. A linear minimum mean square error (LMMSE) unbiased estimator is proposed to attain this goal. By using the minimum mean square error (MMSE) Bayesian estimation, we further propose the LMMSE bit estimator for efficient demodulation. Its performance is close to the optimum multiuser receiver but with a much simpler polynomial complexity. To further reduce the complexity, we extend the LMMSE estimator to the sequential LMMSE estimator. In sequential estimation, we do not need to implement the matched filter banks and to perform the matrix inversion when estimating. In addition, it converges after approximately 2k iterations, where k is the number of users. With this fast convergence property and the simple structure, the sequential LMMSE estimator provides an attractive alternative to the implementation of a multiuser system 相似文献
32.
CaO-Al2O3-MgO (CAM) ceramic fibre produced via inviscid melt spinning (IMS) was investigated for phase transformation. Differential thermal analysis (DTA) on the as-spun CAM fibre gave two transformation peaks, one for exothermic peak at around 927°C and the other for endothermic one at around 1100°C. In order to identify each phase transformation x-ray diffraction (XRD) analysis was performed on the CAM fibres heat-treated to each phase transformation completion temperature. The exothermic peak was determined to represent crystallization of remaining amorphous phase in the as-spun CAM fibre. The endothermic peak was determined to correspond to transformation of non-equilibrium CaO · Al2O3 phase to equilibrium 3CaO· 5Al2O3 phase. 相似文献
33.
In 2006, an involutional block cipher using cellular automata was proposed. A self-invertible CA-based structure allows for an efficient hardware implementation. This paper analyzes the insecurity of the cipher due to its conjugate property. The results of this study will make it possible to construct a decryption process without knowledge of the secret key. 相似文献
34.
Aragonite particles dispersed in a bioresorbable polymer matrix are considered to be a good candidate for bone prosthesis
materials. It is important to characterize the microstructure of synthetic aragonite used for biomedical applications, since
the microstructure may influence its integration, resorption and replacement by bone. We studied late stages of aragonite
growth, at an air–liquid interface, from a solution not doped with additives. Comparison was made between the types of synthetic
aragonite microstructure and that of aragonite which is found in nature (mollusc shells, gallstones, Earth's crust). The microstructure
of natural aragonite is unique to certain classes of living organisms and the understanding of its structure/function relationships
may help to select the types of synthetic aragonite for specific biomedical applications. Three types of synthetic aragonite
were observed based on grain size and grain morphology.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
35.
We report a family in which three siblings developed dementia between the ages of 40 and 70 years. Two of the siblings developed symptoms of depression, abnormal behavior, and an inability to function, progressing to severe dementia. The third sibling had a severe dementia, the clinical details of which are not available. In the two deceased siblings neuropathologic examinations demonstrated severe demyelination, axon loss, and gliosis in cerebral white matter. Cerebellar and brainstem white matter were unaffected. Cerebral gray matter was negligibly affected. The disorder, histopathologically classified as a pigmented orthochromatic leukodystrophy, is extremely rare. Its etiology is unknown, but the pathology and familial occurrence imply that it represents a genetic defect in a function localized in the cerebral white matter. 相似文献
36.
Kang Ji-Hoon Hwang Jinyul Sung Hyung Jin Ryu Hoon 《The Journal of supercomputing》2021,77(9):9597-9614
The Journal of Supercomputing - Direct numerical simulations (DNS) of turbulent flows have increasing importance because they not only provide fundamental understanding of turbulent flows but also... 相似文献
37.
H. C. Yang C. H. Nien H. H. Sung C. H. Chen 《Journal of Low Temperature Physics》1989,75(3-4):243-252
The electrical resistivity, ac susceptibility, critical current density, and Josephson tunneling of Pb/Ag multilayers have been measured in wide temperature ranges in order to study the proximity effect. A resistivity drop was found to occur atT
c
of Pb in versusT measurement and, at low temperature, the multilayers show proximity effect. The I-V characteristic of the multilayer shows voltage steps, indicating a resistive state has occurred in the sample. The superconducting properties of the multilayer were analyzed with the bilayer theory of the proximity effect. 相似文献
38.
Sung H. Whang 《Journal of Materials Science》1986,21(7):2224-2238
The application of rapid solidification technology (RST) to titanium alloy systems is relatively new and became the subject of active research since it was demonstrated that novel titanium alloys of higher temperature capability can be synthesized through new alloy design based on rapid solidification processing. The effects of rapid solidification on the occurrence of metastable phases, microstructures and mechanical properties in binary and ternary titanium alloys are reviewed. In particular, earlier results from RS-Ti alloy research have shown that many different novel dispersoids, some of which are coarsening-resistant at elevated temperatures (600 to 800° C), can be created in the matrix through RST. The alloys containing novel dispersoids also exhibit good creep resistance at elevated temperatures. Further studies on/- and-Ti alloys through RST, in conjunction with the development of various processing technologies for bulk alloy manufacturing, are clearly desirable. 相似文献
39.
Eugene Choi Sung Jean Park Gunhee Lee Seung Kew Yoon Minho Lee Suk Kyeong Lee 《International journal of molecular sciences》2021,22(6)
Hepatocellular carcinoma (HCC), the most common malignant tumor in the liver, grows and metastasizes rapidly. Despite advances in treatment modalities, the five-year survival rate of HCC remains less than 30%. We sought genetic mutations that may affect the oncogenic properties of HCC, using The Cancer Genome Atlas (TCGA) data analysis. We found that the GNAQ T96S mutation (threonine 96 to serine alteration of the Gαq protein) was present in 12 out of 373 HCC patients (3.2%). To examine the effect of the GNAQ T96S mutation on HCC, we transfected the SK-Hep-1 cell line with the wild-type or the mutant GNAQ T96S expression vector. Transfection with the wild-type GNAQ expression vector enhanced anchorage-independent growth, migration, and the MAPK pathways in the SK-Hep-1 cells compared to control vector transfection. Moreover, cell proliferation, anchorage-independent growth, migration, and the MAPK pathways were further enhanced in the SK-Hep-1 cells transfected with the GNAQ T96S expression vector compared to the wild-type GNAQ-transfected cells. In silico structural analysis shows that the substitution of the GNAQ amino acid threonine 96 with a serine may destabilize the interaction between the regulator of G protein signaling (RGS) protein and GNAQ. This may reduce the inhibitory effect of RGS on GNAQ signaling, enhancing the GNAQ signaling pathway. Single nucleotide polymorphism (SNP) genotyping analysis for Korean HCC patients shows that the GNAQ T96S mutation was found in only one of the 456 patients (0.22%). Our data suggest that the GNAQ T96S hotspot mutation may play an oncogenic role in HCC by potentiating the GNAQ signal transduction pathway. 相似文献
40.
Gilles Thibault Gilles Paintaud Hsueh Cheng Sung Laurie Lajoie Edouard Louis the GETAID Celine Desvignes Herv Watier Valrie Gouilleux-Gruart David Ternant 《International journal of molecular sciences》2021,22(11)
The FcγRIIA/CD32A is mainly expressed on platelets, myeloid and several endothelial cells. Its affinity is considered insufficient for allowing significant binding of monomeric IgG, while its H131R polymorphism (histidine > arginine at position 131) influences affinity for multimeric IgG2. Platelet FcγRIIA has been reported to contribute to IgG-containing immune-complexe clearance. Given our finding that platelet FcγRIIA actually binds monomeric IgG, we investigated the role of platelets and FcγRIIA in IgG antibody elimination. We used pharmacokinetics analysis of infliximab (IgG1) in individuals with controlled Crohn’s disease. The influence of platelet count and FcγRIIA polymorphism was quantified by multivariate linear modelling. The infliximab half-life increased with R allele number (13.2, 14.4 and 15.6 days for HH, HR and RR patients, respectively). It decreased with increasing platelet count in R carriers: from ≈20 days (RR) and ≈17 days (HR) at 150 × 109/L, respectively, to ≈13 days (both HR and RR) at 350 × 109/L. Moreover, a flow cytometry assay showed that infliximab and monomeric IgG1 bound efficiently to platelet FcγRIIA H and R allotypes, whereas panitumumab and IgG2 bound poorly to the latter. We propose that infliximab (and presumably any IgG1 antibody) elimination is partly due to an unappreciated mechanism dependent on binding to platelet FcγRIIA, which is probably tuned by its affinity for IgG2. 相似文献