全文获取类型
收费全文 | 102691篇 |
免费 | 6147篇 |
国内免费 | 2618篇 |
专业分类
电工技术 | 3904篇 |
技术理论 | 8篇 |
综合类 | 4027篇 |
化学工业 | 14781篇 |
金属工艺 | 4356篇 |
机械仪表 | 4490篇 |
建筑科学 | 5225篇 |
矿业工程 | 2380篇 |
能源动力 | 2277篇 |
轻工业 | 6197篇 |
水利工程 | 1669篇 |
石油天然气 | 4323篇 |
武器工业 | 483篇 |
无线电 | 8400篇 |
一般工业技术 | 10466篇 |
冶金工业 | 24708篇 |
原子能技术 | 931篇 |
自动化技术 | 12831篇 |
出版年
2024年 | 360篇 |
2023年 | 1223篇 |
2022年 | 2063篇 |
2021年 | 2851篇 |
2020年 | 2030篇 |
2019年 | 1721篇 |
2018年 | 2367篇 |
2017年 | 2737篇 |
2016年 | 2853篇 |
2015年 | 3171篇 |
2014年 | 3562篇 |
2013年 | 3944篇 |
2012年 | 5886篇 |
2011年 | 6533篇 |
2010年 | 4262篇 |
2009年 | 4023篇 |
2008年 | 3768篇 |
2007年 | 3759篇 |
2006年 | 3772篇 |
2005年 | 6092篇 |
2004年 | 4314篇 |
2003年 | 3565篇 |
2002年 | 2282篇 |
2001年 | 1870篇 |
2000年 | 1580篇 |
1999年 | 2239篇 |
1998年 | 7379篇 |
1997年 | 4867篇 |
1996年 | 3539篇 |
1995年 | 2383篇 |
1994年 | 1786篇 |
1993年 | 1577篇 |
1992年 | 632篇 |
1991年 | 616篇 |
1990年 | 550篇 |
1989年 | 476篇 |
1988年 | 467篇 |
1987年 | 331篇 |
1986年 | 292篇 |
1985年 | 229篇 |
1984年 | 124篇 |
1983年 | 118篇 |
1982年 | 158篇 |
1981年 | 202篇 |
1980年 | 206篇 |
1979年 | 67篇 |
1978年 | 102篇 |
1977年 | 615篇 |
1976年 | 1329篇 |
1975年 | 101篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Large spontaneous intrahepatic portosystemic venous shunts are occasionally found and their diagnosis by Doppler sonography is rarely reported. The authors describe a case of spontaneous intrahepatic porto-systemic venous shunt in liver cirrhosis diagnosed by color Doppler and characterized by an unusual pulsed Doppler spectrum: a continuous flat portal-like pattern of flow in the portal branch, and in both the shunt and the hepatic vein. 相似文献
992.
V Heinemann D Bosse U Jehn B K?hny K Wachholz A Debus P Scholz HJ Kolb W Wilmanns 《Canadian Metallurgical Quarterly》1997,41(6):1275-1280
The liposomal formulation of amphotericin B (AmBisome) greatly reduces the acute and chronic side effects of the parent drug. The present study describes the pharmacokinetic characteristics of AmBisome applied to 10 patients at a dose of 2.8 to 3.0 mg/kg of body weight and compares them to the pharmacokinetics observed in 6 patients treated with amphotericin B deoxycholate at the standard dose of 1.0 mg/kg. Interpatient variabilities of amphotericin B peak concentrations (Cmax) and areas under concentration-time curves (AUC) were 8- to 10-fold greater for patients treated with AmBisome than for patients treated with amphotericin B deoxycholate. At the threefold greater dose of AmBisome, median Cmaxs were 8.4-fold higher (14.4 versus 1.7 microg/ml) and median AUCs exceeded those observed with amphotericin B deoxycholate by 9-fold. This was in part explained by a 5.7-fold lower volume of distribution (0.42 liters/kg) in AmBisome-treated patients. The elimination of amphotericin B from serum was biphasic for both formulations. However, the apparent half-life of elimination was twofold shorter for AmBisome (P = 0.03). Neither hemodialysis nor hemofiltration had a significant impact on AmBisome pharmacokinetics as analyzed in one patient. In conclusion, the liposomal formulation of amphotericin B significantly (P = 0.001) reduces the volume of drug distribution, thereby allowing for greater drug concentrations in serum. The low toxicity of AmBisome therefore cannot readily be explained by its serum pharmacokinetics. 相似文献
993.
摩擦诱发高铬铸铁相变的透射电镜研究 总被引:2,自引:0,他引:2
利用透射电子显微镜研究了高铬铸铁在摩擦过程中的显微组织变化。结果表明:奥氏体基体在摩擦应力的作用下发生相变。摩擦表面形成α‘M。次表层形成γ与α’M共存区;γ与.ε共存区;γ位错丛聚区。 相似文献
994.
流溪河灌区工程渠首枢纽计算机监控系统开发与研建 总被引:1,自引:0,他引:1
流溪河渠首枢纽计算机监控系统在自行开发的现场总线工业局域网及专用智能终端、冗余管理和故障诊断专家系统的硬件环境下,在分别由监控系统(含设备层与上位机在线监控系统)和管理系统(由离线管理与服务器上的查询服务系统组成)软件的支持下,实现了对枢纽工程3座水闸47孔闸门的运行和管理,具有自动监测、自动量水、自动控制及系统重构等功能.现已以每天24h不间断地运行了2年,顺利地完成了枢纽工程的调洪、调水等日常调度与运行工作. 相似文献
995.
S Vasil'ev KD Irrgang T Schr?tter A Bergmann HJ Eichler G Renger 《Canadian Metallurgical Quarterly》1997,36(24):7503-7512
The protein composition, steady state and time-resolved fluorescence emission spectra were studied in solubilized and aggregated LHCII complexes, that were prepared according to two different isolation protocols: (1) by fractionation of cation-depleted thylakoid membranes using the non-ionic detergent Triton X-100 according to the procedure of Burke et al. [(1978) Arch. Biochem. Biophys. 187, 252-263] or (2) by solubilization with N-beta-dodecyl maltoside (beta-DM) of photosystem II (PSII) membrane fragments in the presence of cations [Irrgang et al. (1988) Eur. J. Biochem. 178, 207-217]. Based on the analysis of the decay-associated emission spectra measured at 10 and 80 K five long-wavelength chlorophyll species were identified in aggregated LHCII complexes. These five forms are characterized by emission maxima at 681.5, 683, 687, 695, or 702 nm. All of these forms were found in both types of LHCII preparations but the relative amounts and temperature dependency of these species were markedly different in the aggregated LHCII complexes isolated by the two procedures. It was found that these differences cannot be simply explained by effects due to using a less mild detergent as beta-DM or by an ionic influence of Ca2+. Biochemical analysis of the protein composition showed that beta-DM type LHCII consists of all the chlorophyll (Chl)binding proteins belonging to the antenna system of PSII except the CP29 type II gene product (CP29). In contrast, the Triton X-100-solubilized LHCII is highly depleted in CP26 (CP 29 type I gene product) and is contaminated by a variety of unidentified polypeptides. It is proposed that the aggregates of LHCII prepared using Triton X-100 acquire specific spectral and kinetic features due to interaction between the bulk of LHCII subunits and minor protein(s). 相似文献
996.
高校实验材料的计算机化管理 总被引:1,自引:0,他引:1
主要阐述了高校实验材料实行计算机化管理的必要性及全面介绍了自行开发设计的高校实验材料计算机管理系统. 相似文献
997.
用偏微分方程构造过渡面 总被引:9,自引:2,他引:7
用偏微分方程的构造曲面是一种新兴的方法,本文借若干算例说明如何用偏微分方程构造两已知曲面之间的过渡面。论文着重讨论用四阶方程构造一阶连续的过渡面。 相似文献
998.
论述了计算机排版与科技期刊编辑的关系,以及编辑人员在计算机排版时应具备的能力,总结了计算机排版工作中积累的一些值得借鉴的经验。 相似文献
999.
Spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats that had been on a low sodium diet for 3 days were given 1.5 mmol sodium chloride kg-1 body weight either orally or intravenously. The rats receiving an oral sodium load showed a greater natriuresis than those receiving the same saline load intravenously. No increase of renal sodium excretion was observed when the rats received a hypertonic mannitol solution orally. The cumulative sodium excretion during the 8 h following oral loading was two to three times larger in SHR than in WKY, whereas no difference between strains could be demonstrated after giving saline intravenously. Furthermore, after switching from normal to low sodium diet the rate of decrease of renal sodium excretion was greater in SHR than in WKY rats. It is proposed that there exists a gastrointestinal sensory mechanism for sodium controlling the renal sodium excretion. Furthermore, it is suggested that the function of this mechanism differs between SHR and WKY. 相似文献
1000.