全文获取类型
收费全文 | 8671篇 |
免费 | 562篇 |
国内免费 | 29篇 |
专业分类
电工技术 | 132篇 |
综合类 | 6篇 |
化学工业 | 1732篇 |
金属工艺 | 321篇 |
机械仪表 | 584篇 |
建筑科学 | 169篇 |
能源动力 | 370篇 |
轻工业 | 638篇 |
水利工程 | 30篇 |
石油天然气 | 11篇 |
无线电 | 1738篇 |
一般工业技术 | 1819篇 |
冶金工业 | 777篇 |
原子能技术 | 150篇 |
自动化技术 | 785篇 |
出版年
2023年 | 103篇 |
2022年 | 111篇 |
2021年 | 274篇 |
2020年 | 211篇 |
2019年 | 179篇 |
2018年 | 239篇 |
2017年 | 266篇 |
2016年 | 312篇 |
2015年 | 223篇 |
2014年 | 335篇 |
2013年 | 541篇 |
2012年 | 549篇 |
2011年 | 663篇 |
2010年 | 481篇 |
2009年 | 496篇 |
2008年 | 470篇 |
2007年 | 369篇 |
2006年 | 330篇 |
2005年 | 303篇 |
2004年 | 277篇 |
2003年 | 239篇 |
2002年 | 252篇 |
2001年 | 213篇 |
2000年 | 204篇 |
1999年 | 204篇 |
1998年 | 354篇 |
1997年 | 201篇 |
1996年 | 165篇 |
1995年 | 110篇 |
1994年 | 111篇 |
1993年 | 87篇 |
1992年 | 44篇 |
1991年 | 57篇 |
1990年 | 40篇 |
1989年 | 39篇 |
1988年 | 30篇 |
1987年 | 30篇 |
1986年 | 20篇 |
1985年 | 15篇 |
1984年 | 12篇 |
1983年 | 14篇 |
1982年 | 10篇 |
1981年 | 14篇 |
1980年 | 8篇 |
1979年 | 6篇 |
1977年 | 14篇 |
1976年 | 12篇 |
1975年 | 4篇 |
1974年 | 5篇 |
1968年 | 5篇 |
排序方式: 共有9262条查询结果,搜索用时 70 毫秒
91.
92.
In this work, we designed, fabricated and tested a disposable, flow-through amperometric sensor for free chlorine determination in water. The sensor is based on the principle of an electrochemical cell. The substrate, as well as the top microfluidic layer, is made up of a polymer material. The advantages include; (a) disposability from low cost; (b) stable operation range from three-electrode design; (c) fluidic interconnections that provide on line testing capabilities; and (d) transparent substrate which provides for future integration of on-chip optics. The sensor showed a good response and linearity in the chlorine concentration ranging from 0.3 to 1.6 ppm, which applies to common chlorination process for drinking water purification. 相似文献
93.
D.L. Butler P.S. Cho M.W. Chbat J. Goldhar F.-S. Choa G.L. Burdge 《Photonics Technology Letters, IEEE》1996,8(6):779-781
We demonstrate stable operation of a NOLM using orthogonally polarized control and signal beams in nonpolarization-preserving, single-mode fiber. The NOLM can transcribe data from an optically incoherent input at one wavelength to a coherent output over a range of wavelengths. Operation of the NOLM without tuning for the input bit rate is possible over a range of bit rates from less than 1 Gb/s to more than 50 Gb/s. 相似文献
94.
Jung‐Hyun Cho Michael Bass Hans P. Jenssen 《Journal of the Society for Information Display》2007,15(12):1029-1036
Abstract— Several rare‐earth‐doped fluoride crystals that are excited to emit visible light by sequential two‐photon absorption have been investigated as display‐medium candidates for static volumetric three‐dimensional displays. Dispersion of powders of these materials in a refractive‐index‐matched polymer is reported because such a medium may result in a scalable display. The scattering problem in such a medium is greatly reduced by index‐matching the polymer to the crystalline particles. An index‐matching condition that optimizes the performance is identified. 相似文献
95.
Structural Antecedents to Knowledge and Participation: Extending the Knowledge Gap Concept to Participation 总被引:1,自引:0,他引:1
This paper investigates relationships between community characteristics and levels of knowledge and participation examined at both the individual and the community levels. This research extends the knowledge gap concept to a parallel phenomenon, the participation gap. Results from the Social Capital Benchmark Survey 2000 showed that community density, education, and cohesion were significant positive predictors of knowledge but less consistent predictors of participation at the individual level. At the community level, relationships were even stronger, though cohesion was associated with higher mean levels of participation and reduced participation gaps, whereas population density was associated with lower levels of participation and increased gaps. 相似文献
96.
Facial muscle activity and self-reports were examined for racial bias in 3 studies. In the first 2 experiments, While participants imagined cooperating with a Black or White partner. Experiment 1 manipulated reward structure in the context of cooperating with a deficient partner. Experiment 2 manipulated partner deficiency and willingness to expend compensatory effort. On both facial EMG and self-report measures, joint rewards produced more negative affect than independent rewards. However, all partners were liked more when they were willing to try to compensate for their deficits. In addition, more liking was reported for Black partners, but EMG activity indicated bias against Blacks. Experiment 3 investigated individual differences in prejudice. Again, a greater preference for Blacks than Whites occurred on self-report measures, but in their facial muscle activity, high-prejudiced participants exhibited bias against Blacks. 相似文献
97.
Tae-Sung Jung Do-Chan Choi Sung-Hee Cho Myong-Jae Kim Seung-Keun Lee Byung-Soon Choi Jin-Sun Yum San-Hong Kim Dong-Gi Lee Jong-Chang Son Myung-Sik Yong Heung-Kwun Oh Sung-Bu Jun Woung-Moo Lee Haq E. Kang-Deog Suh Ali S.B. Hyung-Kyu Lim 《Solid-State Circuits, IEEE Journal of》1997,32(11):1748-1757
A 3.3-V 16-Mb nonvolatile memory having operation virtually identical to DRAM with package pin compatibility has been developed. Read and write operations are fully DRAM compatible except for a longer RAS precharge time after write. Fast random access time of 63 ns with the NAND flash memory cell is achieved by using a hierarchical row decoder scheme and a unique folded bit-line architecture which also allows bit-by-bit program verify and inhibit operation. Fast page mode with a column address access time of 21 ns is achieved by sensing and latching 4 k cells simultaneously. To allow byte alterability, nonvolatile restore operation with self-contained erase is developed. Self-contained erase is word-line based, and increased cell disturb due to the word-line based erase is relaxed by adding a boosted bit-line scheme to a conventional self-boosting technique. The device is fabricated in a 0.5-μm triple-well, p-substrate CMOS process using two-metal and three-poly interconnect layers. A resulting die size is 86.6 mm2, and the effective cell size including the overhead of string select transistors is 2.0 μm2 相似文献
98.
N Cho Y Nara M Harada T Sugo Y Masuda A Abe K Kusumoto Y Itoh T Ohtaki T Watanabe S Furuya 《Canadian Metallurgical Quarterly》1998,46(11):1724-1737
On the basis of structural information for the cyclic hexapeptide endothelin (ET) receptor antagonist, TAK-044, a series of thieno[2,3-d]pyrimidine-2,4-dione derivatives bearing a carboxyl group and aromatic rings that were important for receptor binding were designed, synthesized, and evaluated for ET receptor binding affinities and inhibitory activities against ET-induced vasoconstriction. Optimization of each substituent in the thieno[2,3-d]pyrimidine ring led to the discovery of a novel and potent nonpeptide ET receptor antagonist, 6-(4-methoxymethoxyphenyl)-5-methylsulfonylaminomethyl-1-(2- methylthiobenzyl)-2,4-dioxo-1,2,3,4-tetrahydrothieno[2,3-d]p yrimidine-3- acetic acid (32 g), which binded to human ETA and ETB receptor subtypes with affinities (IC50) of 7.6 and 100 nM, respectively. Compound 32 g effectively antagonized ET-induced vasoconstriction and the inhibitory effect mediated by the ETB receptor was more potent than that of bosentan, while the inhibitory effect mediated by the ETA receptor was slightly less potent than that of bosentan. 相似文献
99.
Haemophilus influenzae is a bacterium of medical interest of which the entire genome has been sequenced. The proteome of the microorganism has been analyzed by two-dimensional gel electrophoresis, during which immobilized pH 3-10 gradient strips were used and approximately 300 proteins were identified. In order to detect additional, basic proteins, we analyzed the soluble protein fraction of H. influenzae and the proteins of fractions collected from affinity chromatography on heparin, by two-dimensional gel electrophoresis, using for the first-dimensional separation immobilized pH gradient strips comprising the pH region of 6-11. The protein spots were analyzed by matrix-assisted laser desorption ionization-mass spectrometry. One hundred and two proteins were identified, of which 58 were identified for the first time. A large percentage of the basic proteins represent nucleic acid binding and, in particular, ribosomal proteins. The locations of the identified basic proteins of H. influenzae are indicated in a two-dimensional map. 相似文献
100.
OBJECTIVE: Multivariate statistical methods were used to identify patient-related variables that predicted length of stay in a single psychiatric facility. The study investigated whether these variables remained stable over time and could be used to provide individual physicians with data on length of stay adjusted for differences in clinical caseloads and to detect trends in the physicians' practice patterns. METHODS: Data on all patients discharged over two six-month periods were collected at an acute psychiatric inpatient facility. Stepwise multiple regression analyses were conducted on the two datasets. RESULTS: The results from both analyses revealed that five variables significantly predicted length of stay and were stable over time. They were a primary diagnosis of schizophrenia, the number of previous admissions, a primary diagnosis of a mood disorder, age, and a secondary diagnosis of an alcohol- or other drug-related disorder. For some physicians, the mean length of stay of their patients differed significantly from the length predicted by the regression model--generally, it was shorter. CONCLUSIONS: The results demonstrate that patient-related predictors of length of stay in a single psychiatric hospital can be identified using relatively simple statistical procedures and can be consistent across a large dataset and over time. 相似文献