全文获取类型
收费全文 | 2942篇 |
免费 | 81篇 |
国内免费 | 5篇 |
学科分类
工业技术 | 3028篇 |
出版年
2023年 | 18篇 |
2022年 | 44篇 |
2021年 | 82篇 |
2020年 | 22篇 |
2019年 | 44篇 |
2018年 | 51篇 |
2017年 | 36篇 |
2016年 | 65篇 |
2015年 | 51篇 |
2014年 | 68篇 |
2013年 | 156篇 |
2012年 | 115篇 |
2011年 | 161篇 |
2010年 | 104篇 |
2009年 | 122篇 |
2008年 | 139篇 |
2007年 | 99篇 |
2006年 | 105篇 |
2005年 | 96篇 |
2004年 | 78篇 |
2003年 | 94篇 |
2002年 | 77篇 |
2001年 | 73篇 |
2000年 | 60篇 |
1999年 | 73篇 |
1998年 | 199篇 |
1997年 | 150篇 |
1996年 | 103篇 |
1995年 | 68篇 |
1994年 | 77篇 |
1993年 | 58篇 |
1992年 | 33篇 |
1991年 | 27篇 |
1990年 | 15篇 |
1989年 | 20篇 |
1988年 | 13篇 |
1987年 | 23篇 |
1986年 | 19篇 |
1985年 | 32篇 |
1984年 | 19篇 |
1983年 | 20篇 |
1982年 | 13篇 |
1981年 | 11篇 |
1980年 | 16篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1977年 | 19篇 |
1976年 | 19篇 |
1975年 | 5篇 |
1968年 | 4篇 |
排序方式: 共有3028条查询结果,搜索用时 15 毫秒
1.
2.
In recent years, computer technology has made remarkable progress and a computer has become an indispensable tool for both engineers and scientists. In this article, utilization of computers in welding research is briefly summarized. Their use in numerical analysis is particularly discussed and applied to physical phenomena in molten pool, hydrogen diffusion and residual stresses due to welding. A comparison is made between theoretical and experimental results. 相似文献
3.
A cryogenic power cable is expected to be capable of carrying bulk power as a main transmission line in a future metropolitan electric power system. It is important to establish a strategy of how to sustain power supply when such a highly densified power supply route trips from the network due to contingency. It is proposed here that the bulk power transmitted by the cryogenic cable could be distributed into the parallel conventional transmission lines by suitable circuit breaker operations in the system. In this process, power-flow routes are forced to be changed with a remarkable modification in the system configuration. In this paper, the power swings associated with the large power-flow change following contingent faults are analyzed by means of a transient network analyzer. It is found that the proposed system modification could be realized without any harmful power swing if the parameters in generators as well as in control devices have conventional magnitudes. It is shown also by simulations that the margin to occurrence in an unstable power swing is left sufficient even if the parameters deviate somewhat from the present magnitudes. 相似文献
4.
Kenji Nomura Hiromichi OhtaKazushige Ueda Toshio Kamiya Masahiro HiranoHideo Hosono 《Thin solid films》2003,445(2):322-326
We have investigated the characteristics of transparent metal-insulator-semiconductor field-effect transistors (MISFETs) fabricated using InGaO3(ZnO)m (m=integer) single-crystalline thin films as n-channel layers and amorphous alumina as gate insulator films. The MISFETs exhibit good characteristics such as insensitivity to visible light illumination, off-current as low as ∼1 nA with a positive threshold voltage of ∼3 V and on/off current ratio of 105. The field-effect mobility increased from ∼1 to ∼10 cm2 (V s)−1 as the m-value increased. Room temperature Hall mobility also increased. However, unexpectedly these values were lower than the field-effect mobility. It is explained by existence of shallow localized state in the homologous compounds. 相似文献
5.
Preliminary experiments using two chemicals (CaO, a quicklime, and a cationic nitrogen-bearing precipitant, EC-004) to remove silica from geothermal brine were undertaken at the Mokai geothermal plant, New Zealand. The brine was mixed with the reagent (CaO or EC-004). The reaction was studied from the start of the experiment (NRT, 0 min, no retaining time) and after 15 min (15RT) at 90 °C. The concentration of silica in the brine was initially 954 mg/l, and decreased linearly with increasing reagent concentration. When CaO is added, the silica concentration at 15RT was 200 mg/l lower than at NRT and became almost zero on addition of 1.5 g/l. In contrast, when EC-004 is added, the total silica concentration nearly reaches the solubility of amorphous silica at 90 °C. In order to prevent silica scaling in Mokai brines cooled to 90 °C, the CaO and EC-004 added should be individually adjusted to 0.5 g/l and 80 mg/l, respectively. 相似文献
6.
The major envelope protein, p35, of vaccinia virus (VV; strain LIVP) was purified by extraction from virions with the non-ionic detergent Nonidet P-40. The protein was cleaved with CNBr. Four homogeneous peptides were isolated and their N-terminal amino-acid (aa) sequences determined. A computer search of a protein sequence databank revealed complete identity of the determined sequences with aa 44-63, 144-149, 154-165 and 224-238 of ORF H3 of the HindIII-H fragment of the VV genome [Rosel et al., J. Virol. 60 (1989) 436-446]. Earlier, Gordon et al. [Virology 167 (1988) 361-369] determined that the p35 surface protein of VV strain IHD-W is encoded by the H6 gene. Muravlev et al. [Biopolymery i kletka 6 (1990) 83-89 (Russian)] deduced from their data that gene A2 encodes this prominent antigen. Taking into account this ambiguity, we cloned the genes H3, H6 and A2 in expression vectors, prepared the specific antisera against the expression products and conducted the immunochemical analysis of the recombinant and native VV-specific proteins. It has been established that the H6 codes for an early protein that is found only in the infected cell extracts, but is absent in mature virions. The immunodominant protein p35 of VV strain LIVP is encoded by the gene H3. The gene A2 protein product is present mainly in the infected cell extract, but the antiserum against the A2 product shows a rather weak interaction with the 35-kDa fraction of structural VV proteins resolved by electrophoresis. 相似文献
7.
8.
K Ueda 《Canadian Metallurgical Quarterly》1997,24(15):2190-2195
This paper deals with the basic features of the xenobiotic efflux pump (P-glycoprotein and MRP) and the clinical significance of the search for specific modulators of these proteins. P-glycoprotein and MRP function as ATP-dependent efflux pumps that extrude cytotoxic drugs from the cells before the drugs reach their intracellular targets, thus conferring resistance to many structurally dissimilar anti-cancer drugs. These proteins are responsible for multidrug resistance of tumor cells, a major obstacle to cancer chemotherapy. To develop well-designed modulators, structural information regarding the specific drug binding sites is important. We recently found that mutations in the putative transmembrane domain (TM) 1 of human P-glycoprotein alter the drug resistance pattern. Some amino acid residues in TM1 together with TM5-6 and TM11-12 may help to govern substrate specificity. The features common to substrates for P-glycoprotein and MRP are also discussed. 相似文献
9.
Shuzo Ueda Ryoichi Kurihara Noriyuki Miyazaki Toshikuni Isozaki 《International Journal of Pressure Vessels and Piping》1985,18(3):161-176
The purpose of pipe rupture studies in JAERI is to perform model tests on pipe whip, restraint behavior, jet impingement and jet thrust force, and to establish a computational method for analyzing these phenomena. This report presents the analytical results of 4-inch pipe whip tests under BWR LOCA conditions.Dynamic response analyses were performed using the general-purpose finite element program ADINA. The test pipe was modelled by straight beam elements and the four restraints were modelled by a single truss element. The analytical results were compared with the experimental results. Impact time and maximum total restraint force showed good agreement with experimental results. On the other hand, pipe strain and pipe deflection could not be predicted so well. The reason for this is that the sliding of the restraint during the pipe whip movement cannot be considered in the analyses. 相似文献
10.