全文获取类型
收费全文 | 65346篇 |
免费 | 6252篇 |
国内免费 | 3201篇 |
学科分类
工业技术 | 74799篇 |
出版年
2024年 | 290篇 |
2023年 | 1008篇 |
2022年 | 1892篇 |
2021年 | 2568篇 |
2020年 | 1934篇 |
2019年 | 1709篇 |
2018年 | 1999篇 |
2017年 | 2166篇 |
2016年 | 2209篇 |
2015年 | 2667篇 |
2014年 | 3398篇 |
2013年 | 4366篇 |
2012年 | 4834篇 |
2011年 | 5541篇 |
2010年 | 4757篇 |
2009年 | 4668篇 |
2008年 | 4411篇 |
2007年 | 4057篇 |
2006年 | 3681篇 |
2005年 | 3060篇 |
2004年 | 2322篇 |
2003年 | 1827篇 |
2002年 | 1708篇 |
2001年 | 1449篇 |
2000年 | 1180篇 |
1999年 | 959篇 |
1998年 | 908篇 |
1997年 | 614篇 |
1996年 | 504篇 |
1995年 | 353篇 |
1994年 | 333篇 |
1993年 | 272篇 |
1992年 | 186篇 |
1991年 | 168篇 |
1990年 | 121篇 |
1989年 | 106篇 |
1988年 | 82篇 |
1987年 | 74篇 |
1986年 | 58篇 |
1985年 | 33篇 |
1984年 | 33篇 |
1983年 | 36篇 |
1982年 | 31篇 |
1981年 | 22篇 |
1980年 | 22篇 |
1979年 | 23篇 |
1977年 | 27篇 |
1976年 | 32篇 |
1975年 | 14篇 |
1974年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
We describe in this report a sensitive and direct method for the analysis of tamoxifen (TAM) in microsamples of plasma. The drug and internal standard (quinine bisulfate, I.S.) were separated on a 10-microm particle, 10 cm X 8 mm CN cartridge in conjunction with a radial compression system. The mobile phase was a mixture of 0.1 M sodium acetate in 0.001 M tetrabutylammonium phosphate solution (pH 6) and methanol (30:70, v/v) at a flow-rate of 4 ml/min. After addition of I.S. and o-phosphoric acid in acetonitrile (0.6 M) to the plasma (30 microl), the mixture was placed in an ultraviolet shortwave transluminator for 2 min prior to injection into the chromatograph. The compounds were detected in the effluent fluorometrically at excitation and emission wavelengths of 258 and 378 nm, respectively. Under these conditions, no interference in the assay from any endogenous substance or other concurrently used drugs was observed and the retention times of I.S. and TAM were 4.4 and 10.15 min, respectively. The concentration of TAM in plasma was linearly (r>0.9983) related to the peak height ratio (TAM/I.S.) in the range 0.01-2.0 microg ml(-1) and C.V. at 0.075, 0.4 and 1.2 microg ml(-1) was < or = 4.96%. We are currently using this assay for monitoring TAM in plasma and investigating its pharmacokinetics in cancer patients receiving cytotoxic drugs in addition to TAM as a multi-drug resistance modifier. 相似文献
52.
The incidence of stress fractures is increasing among competitive and recreational athletes as well as among children and the elderly. By understanding the continuum of bone's response to stress and maintaining an appropriate index of suspicion, the health care provider can diagnose these injuries appropriately. An accurate history and examination is essential and will differentiate stress fractures from other stress reactions. The more common stress fractures are discussed. 相似文献
53.
Cheol-Min Park Byung-Hyuk Min Jae-Hong Jun Juhn-Suk Yoo Min-Koo Han 《Electron Device Letters, IEEE》1997,18(1):16-18
We have fabricated a self-aligned offset-gated poly-Si thin film transistor (TFT) by employing a novel photoresist reflow process. The gate structure of the new device is consisted of two unique patterns: A main-gate and a sub-gate. The new fabrication method extends the gate-oxide over the offset region. With the assistance of the sub-gate and reflowed photoresist a self-aligned offset region is successfully obtained due to the offset oxide acting as an implantation mask. The poly-Si TFT with symmetrical offsets is easily fabricated and the new method does not require any additional offset mask step. Compared with the misaligned offset gated poly-Si TFTs, excellent symmetric electrical characteristics are obtained 相似文献
54.
本文对CIMS装配线和拆卸线的可靠性问题进行研究。文中分析了它们的运行状况,求出了两种生产线的稳态可用度,并用一个例子加以说明。 相似文献
55.
A unified theoretical method for the calculation of the radio capacity of multiple-access schemes such as FDMA (frequency-division multiple access), TDMA (time-division multiple access), CDMA (code-division multiple access) and SSMA (spread-spectrum multiple access) in noncellular and cellular mobile radio systems is presented for AWGN (additive white Gaussian noise) channels. The theoretical equivalence of all the considered multiple-access schemes is found. In a fading multipath environment, which is typical for mobile radio applications, there are significant differences between these multiple-access schemes. These differences are discussed in an illustrative manner revealing several advantages of CDMA and SSMA over FDMA and TDMA. Novel transmission and reception schemes called coherent multiple transmission and coherent multiple reception are briefly presented 相似文献
56.
本文利用等效工作站理论和工件流平衡原理,推导出非串行离散事件生产线可以等价于串联系统,并归结为装配和拆卸两条定理,解决了系统的建模、分析与设计问题。 相似文献
57.
以路用性能为控制指标,选择满足技术质量指标要求的原材料,对SMA改性沥青混合料的配合比设计进行优化,以期找到最佳路用性能和经济指标的SMA改性沥青混合料配合比的影响因素及对策。研究表明,对级配和体积指标等满足有关要求的特定原材料,其混合料最优路用性能只有在粗集料形成骨架嵌挤密实稳定,其空隙恰好被细集料等组成的胶结料所填充时,即VCADRC-VCAmix值趋向于0(+)才充分体现出来;同时,在满足各项控制指标的前提下,可以通过适当增大2.36mm集料通过率来进一步提高混合料的抗车辙和稳定性能。 相似文献
58.
It is essential to automate the scanning path generation process to effectively implement the micro-stereolithography. However, a scanning path that is generated based only on a 3D CAD model introduces dimensional inaccuracies. In micro-stereolithography, the photopolymer solidification is affected by fabrication conditions, such as the optical properties (laser power, laser scanning speed, laser scanning pitch focusing condition, etc.) and material properties of the photopolymer. Thus, the photopolymer solidification phenomena must be considered when generating a laser scanning path. In this paper, a scanning path generation algorithm that uses 3D CAD data and considers the photopolymer solidification phenomena is proposed to improve the dimensional accuracy in micro-stereolithography. Multi-line photopolymer solidification experiments were performed for various laser scanning conditions to examine the photopolymer solidification phenomena. From these experiments, linear relations between the solidification length (width) and scanning length (width) were acquired and stored in a database. Subsequently, these data were utilized to compensate the scanning path of the laser beam. In addition, experiments for determining the layer thickness in the z-direction were performed and these results were also used in the scanning path generation algorithm.This research was supported by the Highly Advanced National Project (http://www.most.go.kr), which performs some of the National R&D Program, and sponsored by the Korean Ministry of Science and Technology under the contract project code M10214000116-02B1500-02010. 相似文献
59.
KS Min AR Khan MK Kwon YJ Jung Z Yun Y Kiso 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(8):909-915
The performance of a laboratory‐scale anaerobic acidogenic fermenter fed with a mixture of blended kitchen food‐waste and primary sludge from a sewage treatment plant was investigated for the production of volatile fatty acids (VFA). The operating variables for acidogenic fermentation were kitchen food‐waste content (10 and 25 wt %), hydraulic retention time (HRT: 1, 3 and 5 days), temperature (ambient: 18 ± 2 °C, and mesophilic: 35 ± 2 °C) and pH (varied from 5.2 to 6.7). The experimental results indicated that effluent VFA concentrations and VFA production rates were higher at ambient temperature than at mesophilic conditions. The net amount of VFA with 10 wt % food‐waste increased up to 920 mg dm?3 with an increase of HRT, but contrasting results (a decrease of 2610 mg dm?3) were found due to the conversion of VFA into biogas in the case of 25 wt % food‐waste, which increased significantly at HRT of 3–5 days. In terms of biogas composition (CO2 and CH4), the organic matter was converted into CO2 through the oxidative pathway by facultative species at low temperature while mesophilic temperature and optimum pH (6.3–7.8) played a pivotal role in increasing rate of conversion of VFA into biogas by methanogenesis. Rates of VFA production and their conversion are dependent on the food‐waste content in the mixture. Yet, the higher concentration of food‐waste (25% compared with 10%) did not produce VFA proportionally due to the increased rate of conversion of VFA into gaseous products. The maximum VFA production rate (0.318 g VFAproduced g?1 VSfed day?1) was achieved in the 10 wt % food‐waste at ambient temperature and at a 5‐day HRT. Copyright © 2005 Society of Chemical Industry 相似文献
60.
历史中心区复兴中的地域性问题与对策 总被引:2,自引:0,他引:2
本文以上海思南路47~48街坊改造为例,探讨城市形态更新与居民外迁问题,并期待相关地域性社会对策的出现。 相似文献