全文获取类型
收费全文 | 3840篇 |
免费 | 107篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 188篇 |
综合类 | 6篇 |
化学工业 | 849篇 |
金属工艺 | 127篇 |
机械仪表 | 63篇 |
建筑科学 | 70篇 |
矿业工程 | 1篇 |
能源动力 | 135篇 |
轻工业 | 253篇 |
水利工程 | 12篇 |
石油天然气 | 5篇 |
无线电 | 400篇 |
一般工业技术 | 733篇 |
冶金工业 | 727篇 |
原子能技术 | 96篇 |
自动化技术 | 293篇 |
出版年
2023年 | 13篇 |
2022年 | 36篇 |
2021年 | 71篇 |
2020年 | 32篇 |
2019年 | 57篇 |
2018年 | 72篇 |
2017年 | 67篇 |
2016年 | 86篇 |
2015年 | 69篇 |
2014年 | 73篇 |
2013年 | 179篇 |
2012年 | 134篇 |
2011年 | 214篇 |
2010年 | 149篇 |
2009年 | 166篇 |
2008年 | 157篇 |
2007年 | 151篇 |
2006年 | 105篇 |
2005年 | 114篇 |
2004年 | 132篇 |
2003年 | 98篇 |
2002年 | 76篇 |
2001年 | 79篇 |
2000年 | 54篇 |
1999年 | 94篇 |
1998年 | 302篇 |
1997年 | 190篇 |
1996年 | 144篇 |
1995年 | 76篇 |
1994年 | 63篇 |
1993年 | 102篇 |
1992年 | 49篇 |
1991年 | 72篇 |
1990年 | 42篇 |
1989年 | 40篇 |
1988年 | 33篇 |
1987年 | 30篇 |
1986年 | 41篇 |
1985年 | 35篇 |
1984年 | 28篇 |
1983年 | 30篇 |
1982年 | 31篇 |
1981年 | 30篇 |
1980年 | 26篇 |
1979年 | 23篇 |
1978年 | 20篇 |
1977年 | 18篇 |
1976年 | 18篇 |
1975年 | 11篇 |
1973年 | 10篇 |
排序方式: 共有3958条查询结果,搜索用时 0 毫秒
1.
Takayuki Honma Yuichiro Kuroki Tomoichiro Okamoto Masasuke Takata Yukihiro Kanechika Masanobu Azuma Hitofumi Taniguchi 《Ceramics International》2008,34(4):943-946
Aluminum nitride ceramics were prepared by sintering with 0–4.8 mass% of Ca3Al2O6 (C3A) as a sintering additive. The transmittance in the range of 260–550 nm increased with increasing amount of C3A. The cathodoluminescence intensity attributed to oxygen-induced defects decreased with increasing amount of C3A. From the results, the increase of the transmittance in the range of 260–550 nm was considered to be related to the decrease of the oxygen-induced defect density. 相似文献
2.
Recently published studies indicate a potential clinical application of PET in head and neck tumors. In the preoperative staging phase, PET enables confirmation of regional lymph node extension and guides nodal neck dissection or systemic treatment. In this phase, a high negative predictive value, near 100%, could make it possible to avoid many negative neck dissections. This is a reliable technique for confirming or excluding the presence of recurrent/residual tumor and for obtaining an early evaluation of chemotherapeutic and radiotherapeutic response. PET imaging in many cases makes it possible to locate and guide histological study of tumors with an unknown primary. PET imaging for these indications is a perfect complementary method for clinical exploration and better than other imaging techniques. 相似文献
3.
Tadashi Hano Michiaki Matsumoto Takahisa Kawazu Takaaki Ohtake 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,62(1):60-63
The extraction equilibria of various di- and tripeptides with di-2-ethylhexylphosphoric acid (D2EHPA) were studied at low pH values. The complex extracted to organic phase consisted of one molecule of peptide and two molecules of D2EHPA dimer. The extraction constants of the peptides correlated well with the distribution coefficients of peptides between 1-octanol and water, which is a measure of hydrophobicity. The permeation rates of peptides through an emulsion liquid membrane were examined by using D2EHPA as a carrier, Span 80 as an emulsifier and kerosene as a diluent. The rates varied considerably with peptide type, depending upon the hydrophobicity. 相似文献
4.
A Ikeda K Fujimoto I Yoshii S Matsumoto K Nishitani K Ikeda 《Canadian Metallurgical Quarterly》1993,68(4):410-421
Ever since 1974, the cadaver has been embalmed by the arterial embalming method, using pre-embalming fluid with blood clot disperser and cell conditioner for the removal of blood clots and drainage of blood, at the Department of Anatomy of the Kawasaki Medical School. According to this method, the cadavers are always very well fixed so that they can be used for not only anatomical dissection but also research for the vascular system by vasography, kinematics of the joint and other histologic examinations. In this report we have described our embalming procedure concretely and its application to research. 相似文献
5.
Fatemeh Niyati-Shirkhodaee Takayuki Shibamoto 《Journal of the American Oil Chemists' Society》1992,69(12):1254-1256
Formaldehyde, acrolein, malonaldehyde (MA), acetaldehyde and propanal produced from cod liver oil upon ultraviolet irradiation
(λmax=300 nm) were derivatized into nitrogenor sulfur-containing compounds and then analyzed by capillary gas chromatography with
a nitrogen-phosphorus detector or a flame photometric detector. Acrolein and MA were formed at levels of 10.9±3.06 and 190.2±38.4
nmol/mg of fish oil, respectively. Maximum levels of formaldehyde, acetaldehyde and propanal formed were 7.0±0.90, 49.1±4.5
and 35.8±4.0 nmol/mg of oil, respectively. Formation of propanal in large quantities corresponded to the high content of ɛ-3
fatty acids in cod liver oil. 相似文献
6.
Anju Sawada Takehiro Kubo Yosikazu Abe Kazuyuki Matsumoto 《Journal of Low Temperature Physics》1995,101(3-4):707-712
The isochoric pressure of bcc Solid3He in the vicinity of the triple point has been measured by changing the temperature stepwisely and waiting for thermal equilibrium. We observed anomalous pressure kinks of the temperature dependence in the paramagnetic region near the triple point. This anomaly appeared at 0.37 to 0.40 tesla, and disappeared below 0.36 tesla. Moreover, critical phenomena at the transition point from the paramagnetic phase (PP) to the high field phase was observed and the phase line curves toward the PP side. 相似文献
7.
G Egusa F Murakami C Ito Y Matsumoto S Kado M Okamura H Mori K Yamane H Hara M Yamakido 《Canadian Metallurgical Quarterly》1993,100(2):249-255
It has recently been reported that there exists a new 'RING-finger' protein family among the zinc-finger (Zf) proteins. Previously, we had isolated the mouse Mel-18 cDNA (mMel-18) encoding the nuclear RING-finger protein that exhibits an ability to bind to a nonspecific DNA column. Here, we have isolated and characterized the human Mel-18 cDNA (hMel-18) using the mMel-18 cDNA as a probe. The deduced hMel-18 protein contains 344 amino acids (38 kDa) with a RING-finger motif, a helix-loop-helix (HLH)-like structure and a Pro/Ser-rich region. The hMel-18 gene is conserved among vertebrates. Its mRNA is highly expressed in placenta, lung and kidney, but the level is low in liver, pancreas and skeletal muscle. Using in situ hybridization, we mapped hMel-18 to band q22 of chromosome 12. It is possible that the Mel-18/bmi-1 gene family represents a mammalian homologue of the Drosophila polycomb gene group. 相似文献
8.
Phenol novolac/poly (4-hydroxyphenylmaleimide) (PHPMI) blends were used as an epoxy resin hardener. The curing behavior of the above system and the thermal and mechanical properties of the cured epoxy resin were studied. It was not necessary to use a curing accelerator for this system, because PHPMI caused acceleration of the curing reaction. The curing mechanism of this system was investigated by using model compounds. Test pieces from the neat resins and the glass fiber reinforced resins were evaluated in terms of thermal and mechanical properties, respectively. It was found that heat resistance and mechanical properties were improved by increasing the amount of PHPMI in the hardener. 相似文献
9.
10.
The codeword error rate (WER) performance of noncoherent frequency-shift keying with soft decision decoding of block codes using Chase's second algorithm (1972) is investigated in a Rayleigh fading channel. The received signal envelope is sampled and used as channel measurement information. The theoretical upper and lower bounds of the WER are derived, assuming independent Rayleigh envelope samples in a received block. When the Golay (23, 12, 7) code is used, soft decision decoding with 6-bit error correction capability (3-bit error and 3-bit erasure) requires an average signal-to-noise power ratio about 5 dB lower than that for minimum distance decoding with 3-bit error correction to obtain a WER=10-3. The effects of bit interleaving on the WER performance when fading envelope variation is slow compared to the bit rate are investigated through computer simulations 相似文献