全文获取类型
收费全文 | 1707篇 |
免费 | 32篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 88篇 |
综合类 | 2篇 |
化学工业 | 448篇 |
金属工艺 | 53篇 |
机械仪表 | 43篇 |
建筑科学 | 26篇 |
能源动力 | 102篇 |
轻工业 | 135篇 |
水利工程 | 9篇 |
石油天然气 | 1篇 |
无线电 | 166篇 |
一般工业技术 | 306篇 |
冶金工业 | 142篇 |
原子能技术 | 60篇 |
自动化技术 | 161篇 |
出版年
2023年 | 7篇 |
2022年 | 13篇 |
2021年 | 23篇 |
2020年 | 14篇 |
2019年 | 24篇 |
2018年 | 17篇 |
2017年 | 17篇 |
2016年 | 30篇 |
2015年 | 19篇 |
2014年 | 51篇 |
2013年 | 118篇 |
2012年 | 84篇 |
2011年 | 87篇 |
2010年 | 78篇 |
2009年 | 101篇 |
2008年 | 95篇 |
2007年 | 71篇 |
2006年 | 65篇 |
2005年 | 61篇 |
2004年 | 48篇 |
2003年 | 60篇 |
2002年 | 49篇 |
2001年 | 32篇 |
2000年 | 39篇 |
1999年 | 43篇 |
1998年 | 73篇 |
1997年 | 31篇 |
1996年 | 39篇 |
1995年 | 21篇 |
1994年 | 21篇 |
1993年 | 35篇 |
1992年 | 24篇 |
1991年 | 16篇 |
1990年 | 15篇 |
1989年 | 22篇 |
1988年 | 20篇 |
1987年 | 6篇 |
1986年 | 11篇 |
1985年 | 20篇 |
1984年 | 17篇 |
1983年 | 12篇 |
1982年 | 13篇 |
1981年 | 18篇 |
1980年 | 19篇 |
1979年 | 13篇 |
1978年 | 11篇 |
1977年 | 10篇 |
1976年 | 11篇 |
1968年 | 3篇 |
1967年 | 3篇 |
排序方式: 共有1742条查询结果,搜索用时 78 毫秒
1.
Y Furuya Y Yoshida T Katayama S Yamamoto A Kawamura 《Canadian Metallurgical Quarterly》1993,31(6):1637-1640
Polymerase chain reaction (PCR) with nested primer pairs was used to diagnose scrub typhus and identify the Rickettsia tsutsugamushi serotype. The primer pairs used for PCR were designed on the basis of the nucleotide sequence of the gene that encodes the 56-kDa antigen. Serotype-specific primers were used in the second PCR amplification. Five serovariants, the Gilliam, Karp, Kato, Kawasaki, and Kuroki strains of R. tsutsugamushi, were identified by nested PCR. In addition, the serotype identified by PCR with DNA from blood clots was the same as that of the strain isolated from five patients with scrub typhus. These findings indicate that this method is useful for diagnosis and identification of the rickettsial serotype in infected patients. 相似文献
2.
Cortical blood flow (CoBF) was measured continuously by the laser-Doppler method to evaluate the effect of hypercapnia on cortical blood flow during ten surgical procedures in ten young patients (mean +/- SD 9.3 +/- 6.4 yr) with Moyamoya disease. The CoBF was 42.8 +/- 13.4 (ml.100 g-1.min-1) during normocapnia (PaCO2 = 39.0 +/- 2.4 mmHg), and 38.7 +/- 14.4 during hypercapnia (PaCO2 = 47.1 +/- 2.5 mmHg). There was a decrease in CoBF with hypercapnia (P < 0.05) so that the normal CoBF response to hypercapnia was impaired during surgery in the patients with Moyamoya disease. He concluded that patients with Moyamoya disease have a precarious cerebral circulation and hypercapnia may be detrimental to the cortical circulation. This suggests that normocapnia is preferable to hypercapnia in patients with Moyamoya disease during anaesthesia. 相似文献
3.
Ten site-specific mutants of pea apophytochrome A were expressed in Saccharomyces cerevisiae and analyzed for chromophore assembly with apoprotein and photoreversible absorbance changes. The mutants constitute two specific changes for each of five conserved amino acid residues located in the microenvironment of the chromophore attachment residue, which is Cys-323 in pea phytochrome A. All mutant apophytochromes were autocatalytically able to covalently attach phycocyanobilin, indicating that there were no major structural perturbations in the apoproteins. However, the rate of chromophore ligation varied significantly among the mutants. Spectrally, the mutant holophytochromes are of three types: mutant phytochromes that are indistinguishable from the wild-type adduct, mutants with blue-shifted Pr and Pfr absorption maxima compared to the wild-type adduct, and mutants that are not photoreversible. From an analysis of the results, we concluded that the residues Asp-309, Arg-318, His-321, and Gln-326 are probably not catalytically involved in the chromophore ligation reaction, but some residues may play significant structural and stereochemical roles. Arg-318 might anchor the chromophore, as has been suggested [Partis, M. D., & Grimm, R. (1990) Z. Naturforsch, 45c, 987-998; Parker, W., et al. (1993) Bioconjugate Chem. (in press)]. The conserved Gln-326, three residues downstream from the chromophore attachment site, is not electrostatically critical for the spectral integrity and photoreversibility of phytochrome, but this residue is sterically important to the lyase activity. It appears that the role of the five amino acid residues in the N- and C-terminal vicinities of the chromophore binding Cys-323 is structural rather than catalytic for the ligation reaction. 相似文献
4.
Shijie Zhu Yutaka Kagawa Jian-Wu Cao Mineo Mizuno 《Metallurgical and Materials Transactions A》2004,35(9):2853-2859
Time-dependent deformation in an enhanced SiC/SiC composite has been studied under constant load at high temperatures of 1200
°C, 1300 °C, and 1400 °C. Creep damage evolution was evaluated by a Young’s-modulus change of partial unloading and microscopic
observation. The addition of the glassy phase in the matrix is very effective for protecting the composite from oxidation.
The transient creep is dominant in creep life at all the temperatures. An empirical equation is proposed to describe creep
behavior of the composite. It is found that creep activation energy increases with creep time at stresses lower than matrix
cracking stress, but the activation energy remains constant at stresses higher than the matrix cracking stress. The creep
strain rate of the composite is considered to be controlled by creep of fibers based on examining the time, strain, stress,
and temperature dependencies of creep strain rates. 相似文献
5.
Y Shioda S Koizumi S Furuya S Akira N Kameyama N Hamano W Takahashi A Tokunaga N Tanaka M Onda 《Canadian Metallurgical Quarterly》1993,23(6):556-561
Respiratory infections are the most common infection in children. They differ remarkably according to age, bacteria and viruses. Therefore a careful history of outbreak, age, former infections, involvement of surroundings, symptoms, etc are essential. The present study included 50 children, aged between 0.3 and 12 yrs, all treated ambulatorily. 21 received brodimoprim (B) and 29 erythromycin (E). Indications were: tonsillitis, bronchitis, otitis media, sinusitis and scarlet fever. Dosages were: B was given 10 mg/kg body weight (b.w.) initially followed by 5 mg/kg b.w., once-a-day. The duration of treatment varied between 4 and 14 days (mean 8.3 days). E was given 30.50 mg/kg b.w. 3 times per day; duration 4 to 14 days (mean 8.6 days). Overall results were: in group B:12 cures, 5 improvements, 3 failures; 1 not assessable. In group E: 20 cures, 8 improvements, 1 failure. Side effects: in group B: vomiting (1), skin reaction (2), discontinuation (2); in group E: skin reaction (1), diarrhea (5), diarrhea+vomiting (1); discontinuation (2). The differences in efficacy and tolerability in the two groups are not statistically significant. The improved compliance with a single versus t.i.d. dosages has to be taken into account. 相似文献
6.
Hirokazu Ikeda Chikara Fukunaga Yutaka Saitoh Masahiro Inoue Junko Yamanaka 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1996,380(3):618-622
The radiation tolerance for prototype front-end chips designed for a silicon micro-strip detector was examined with a 60Co irradiation source to establish an allowable range of the radiation dose. The irradiated front-end chips were SMA2SH-64A, a 64-channel preamplifier array; SMA2SH-1, a single-channel preamplifier circuit with a comparator; and Control-C, a digital-control chip for the preamplifiers. 相似文献
7.
8.
Yutaka Asako Hisayoshi KamikogaHisashi Nishimura Yoshiyuki Yamaguchi 《International Journal of Heat and Mass Transfer》2002,45(11):2243-2253
Compression is one solution to improve the strength of softwoods. The effective thermal conductivities of compressed Japanese cedars (cryptomeria japonica), which were compressed in the radial direction of the wood, were measured. Both the effective thermal conductivities in the tangential and fiber directions increase proportionally to the density increment due to the compression. However, the thermal conductivity in the radial direction (compression direction) increases slightly with the density increment. Numerical computations were conducted to explain the characteristics of thermal conductivity in the radial direction by using a microscopic heat conduction model for the compressed wood. The numerical results were compared with the measured values. And the physical mechanism of the heat conduction in the compressed woods is discussed. 相似文献
9.
A single loop electrochemical potentiokinetic reactivation test method has been developed for alloy 600 that produces good passivation on all the surfaces, good etching during the reactivation scan and no appreciable pitting. It is able to quantify and discriminate between samples with a wide range of degree of sensitization. The Pa value correlates well with the minimum level of chromium in the depletion regions at the grain boundaries. It has been shown that the width of the attacked regions is much larger than the width of chromium depletion regions and it does not show any direct correlation with either depth or width or with a volume parameter of chromium depletion regions. It has been shown that the chromium carbides are not attacked during the test and that the intragranular regions attacked during the test are the sites of chromium carbides in the grain matrix. A modified Pa parameter is shown to be sensitive down to 7.5 wt% chromium in the depletion regions and indicates that the intragranular carbides have shallower depletion profiles than those at grain boundaries. Comparison of the results of the single loop and the double loop tests showed a good correlation. 相似文献
10.
The effect of Zr on reduction of hardness and microstructure in an FS weld of equal channel angular-pressed Al alloy was investigated. Zr addition to Al suppressed dynamic recovery in the thermomechanically affected zone and enabled retention of the high hardness of the ECA-pressed material throughout the weld. 相似文献