全文获取类型
收费全文 | 78752篇 |
免费 | 7282篇 |
国内免费 | 4378篇 |
学科分类
工业技术 | 90412篇 |
出版年
2024年 | 332篇 |
2023年 | 1098篇 |
2022年 | 2334篇 |
2021年 | 2947篇 |
2020年 | 2251篇 |
2019年 | 1916篇 |
2018年 | 2148篇 |
2017年 | 2383篇 |
2016年 | 2122篇 |
2015年 | 3135篇 |
2014年 | 3966篇 |
2013年 | 4709篇 |
2012年 | 5503篇 |
2011年 | 5797篇 |
2010年 | 5356篇 |
2009年 | 5291篇 |
2008年 | 5480篇 |
2007年 | 5228篇 |
2006年 | 5053篇 |
2005年 | 4148篇 |
2004年 | 3013篇 |
2003年 | 2445篇 |
2002年 | 2268篇 |
2001年 | 1993篇 |
2000年 | 1782篇 |
1999年 | 1522篇 |
1998年 | 1131篇 |
1997年 | 985篇 |
1996年 | 840篇 |
1995年 | 740篇 |
1994年 | 614篇 |
1993年 | 423篇 |
1992年 | 369篇 |
1991年 | 238篇 |
1990年 | 187篇 |
1989年 | 189篇 |
1988年 | 132篇 |
1987年 | 86篇 |
1986年 | 52篇 |
1985年 | 39篇 |
1984年 | 24篇 |
1983年 | 27篇 |
1982年 | 29篇 |
1981年 | 14篇 |
1980年 | 16篇 |
1979年 | 8篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1959年 | 6篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
131.
In this paper, the CdxHg1-xTe (x=1-0.7) doped silica glass was prepared through two step sol-gel process and in-situ growth technique from tetraethoxysilane (TEOS), cadmium acetate, mercury acetate and telluric acid. The influence of various factors on the glass was studied. The structure of the microcrystals was investigated by XRD. The absorption and transmittance spectrum of the composite showed that the shift of absorption edge was in conformity with the quantum size effect. The third-order nonlinear optical susceptibility χ(3) was measured by the degenerate four wave mixing (DFWM). The values of χ(3) was in the range of 10-11-10-12 MO esu at wavelength of 1.06 μm. 相似文献
132.
Ping Liu Zheng-Fan Li Guo-Bing Han 《Electromagnetic Compatibility, IEEE Transactions on》2006,48(3):485-492
In this paper, the asymptotic waveform evaluation (AWE) technique is first applied to the conventional eigenmode expansion method for characterizing a power/ground (P/G) plane pair and analyzing the simultaneous switching noise on such plane pairs for printed circuit boards or multichip modules. The application of AWE avoids a large number of iterations in computing the impedance frequency response of a P/G plane pair structure and greatly reduces the computation time. Meanwhile, to obtain an accurate solution in an entire frequency range, we employ the complex frequency hopping technique which can help select multiple expansion points. In addition, the proposed approach can also be used to characterize the P/G plane pair structures with irregular shapes. Three examples demonstrate its high efficiency and good accuracy. 相似文献
133.
134.
135.
136.
BaTiO3 multilayer capacitors with a nominal capacitance of 3.5nF have been carefully measured using the thermally stimulated current (TSC) technique. When a 300V polarization voltage is applied at room temperature, a new TSC peak appeared in defective sample A after it has been immersed in water. No new peak was found in good-quality sample B after a similar treatment. The accelerated life test shows that sample A hasa much shorter life than sample B in terms of insulation resistance. 相似文献
137.
本文选用 ICR 雄性小鼠,经腹腔分别注射不同剂量的~(125)I 及~(131)I,观察并比较它们对小鼠精子畸形发生率的影响及染毒后睾丸中放射性活度的变化。实验结果表明:(1)~(125)I 染毒后4—5周,0、185、370和555 kBq 各组精子畸形发生率分别为9.00‰、9.57‰、11.6‰及13.9‰;~(131)I 染毒后4—5周,上述各组精子畸形发生率分别为8.50‰、12.5‰、14.7‰和15.5‰;在相同注入量下,~(125)I 与~(131)I 诱发小鼠精子畸形发生率的差异各组均不显著(X~2检验,p>0.05)。(2)~(125)I、~(131)I 染毒后2h 至7天内,两者在睾丸中的放射性活度及变化规律相似,即在染毒后2h 达最高值,每克睾丸中~(125)I 和~(131)I 的放射性活度分别占初始注入量(370 kBq)的0.72%和0.50%,然后迅速下降,至一周时,仅分别占初始注入量的0.035%和0.011%。 相似文献
138.
叙述了Quilone试剂的合成,改性脲醛树脂的原理、实验方法、改性后脲醛树脂的抗水性、抗渗透性、耐化学药品性及其影响因素。 相似文献
139.
With the aid of a double-tilt holder in a transmission electron microscope, a new method for a rapid and precise determination of the misorientations of a large number of subgrain or grain boundaries is given in this article. By use of the method, the continuous recrystallization can be rapidly and precisely evaluated when compared to the other conventional methods. 相似文献
140.
An experimental study for the pathologic changes of the canine tracheal mucosa under YAG:Nd laser ablation was performed in order to master the appropriate parameters for the clinical treatment of YAG:Nd laser. 6 male and female Mongolia dogs weighing 13-18 kg were received 20W YAG:Nd laser treatment and their pathologic changes were examined instantly and 3, 7, 14 and 28 days after ablation. 相似文献