全文获取类型
收费全文 | 89370篇 |
免费 | 8074篇 |
国内免费 | 4539篇 |
学科分类
工业技术 | 101983篇 |
出版年
2024年 | 386篇 |
2023年 | 1406篇 |
2022年 | 2688篇 |
2021年 | 3743篇 |
2020年 | 2708篇 |
2019年 | 2352篇 |
2018年 | 2514篇 |
2017年 | 2829篇 |
2016年 | 2767篇 |
2015年 | 3619篇 |
2014年 | 4485篇 |
2013年 | 5382篇 |
2012年 | 5861篇 |
2011年 | 6384篇 |
2010年 | 5839篇 |
2009年 | 5387篇 |
2008年 | 5269篇 |
2007年 | 4907篇 |
2006年 | 4809篇 |
2005年 | 4147篇 |
2004年 | 2962篇 |
2003年 | 2803篇 |
2002年 | 3076篇 |
2001年 | 2623篇 |
2000年 | 2168篇 |
1999年 | 1988篇 |
1998年 | 1540篇 |
1997年 | 1346篇 |
1996年 | 1251篇 |
1995年 | 1065篇 |
1994年 | 897篇 |
1993年 | 650篇 |
1992年 | 482篇 |
1991年 | 368篇 |
1990年 | 270篇 |
1989年 | 232篇 |
1988年 | 192篇 |
1987年 | 118篇 |
1986年 | 93篇 |
1985年 | 65篇 |
1984年 | 43篇 |
1983年 | 30篇 |
1982年 | 32篇 |
1981年 | 29篇 |
1980年 | 26篇 |
1979年 | 18篇 |
1975年 | 8篇 |
1962年 | 42篇 |
1961年 | 39篇 |
1960年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
83.
OBJECTIVE: To identify the influence of the increased level of serum cholyglycine (CG) on lipid metabolism and hemorrheology in patients with intrahepatic cholestasis during pregnancy (ICP). METHODS: The concentrations of serum CG, total cholesterol (CH), triglycerides (TG), high density lipoprotein-cholesterol (HDL-C), low density lipoprotein-cholesterol (LDL-C), high shear and low shear of blood specific viscosity (HS and LS), plasma specific viscosity (PV) and hematocrit (HCT) were measured in 68 cases of primiparas with single pregnancy and 30 healthy nonpregnant women respectively. The group of ICP was composed of 35 cases with CG > 6 mumol/L, the group of normal pregnancy, 33 cases with CG < 6 mumol/L. RESULTS: The means of CG and the lipidic parameters in the two pregnant groups were significantly higher than those in the non-pregnancy group (P < 0.02-0.001) except the means of HDL-C between the groups of ICP and non-pregnancy. The levels of LDL-C, LDL-C/HDL-C, LS, PV and HCT in the ICP were significantly higher than those in the normal pregnancy group (P < 0.02-0.001). CONCLUSIONS: There are significant changes of lipid metabolism and hemorrheology in patients with ICP. However, these changes could be corrected after pregnancy termination, when the level of serum CG returned to normal. The results suggest that the pathophysiologic changes of ICP are associated with increased level of serum CG. 相似文献
84.
Fractal geometry is finding its application in the nondestructive evaluation (NDE) of corrosion by characterizing the corrosion surface with fractal dimensions. It was found that corrosion surfaces can be well described by multifractals. Two algorithms were used to obtain the fractal dimensions of a corroded aluminum alloy surface, one being box-counting and another being coherent light scattering. Fractal dimensions were related with the damage caused by corrosion and fatigue. 相似文献
85.
Yu Jin Joshi S.G. 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1996,43(3):491-494
It is found that an acoustic wave which is nearly polarized in the shear horizontal (SH) direction can propagate along the X axis of a Z-cut lithium niobate plate if the ratio h/λ, where h=plate thickness and λ=acoustic wavelength, is less than about 0.5. Attractive properties of this quasi-SH wave include: (1) phase velocity nearly constant for all values of h/λ; (2) ability to propagate in contact with a liquid medium; and (3) electromechanical coupling coefficient as high as 0.15. These properties make the wave attractive for use in a variety of sensor and signal processing applications. An example of sensor applications is illustrated by using the wave to measure conductivity of liquids (aqueous KCl solution). The frequency of a 12-MHz quasi-SH mode oscillator fabricated on a 0.48 wavelength thick Z-X lithium niobate plate is found to vary by more than 80 kHz for variation in KCI concentration from 0 to 0.15% 相似文献
86.
链烷烃的表面张力与内压 总被引:1,自引:0,他引:1
对Davis和Rosseinsky提出的关系检验表明,液体的表面张力σ与P1Vm1/3之比不仅取决于温度,还与液体的种类有关,据此,建立了一个能由链烷烃的分子结构准确预测其表面张力的方法。 相似文献
87.
88.
研究了铁钴钒软磁合金的铁芯损耗,发现铁芯损耗谱具有分形结构。讨论了带材厚度和磁感应强度对分形维数Df的影响。 相似文献
89.
Ye. L. Stolov 《Journal of Electronic Testing》1993,4(3):283-283
Let a circuit havem outputs,m>1. There are two ways to test this circuit by means of a signature analyzer: use a single input analyzer for each output or use anm-input analyzer to test all outputs simultaneously. The main goal of this letter is to demonstrate that for fault output sequences with small multiplicity of errors and long length the second approach is more effective. 相似文献
90.
本文介绍了一种计算机存储系统中的单向错误检测码,系统构成采用9位字节,其中8位数据位,1位校验位,并使用一个单独的附加奇偶校验字节。单向错误检测码有两类,一类每个字包含固定的奇偶校验位;另一类每个字节包含的检验位的构成方式是任意的。 相似文献