全文获取类型
收费全文 | 38870篇 |
免费 | 2307篇 |
国内免费 | 3891篇 |
专业分类
电工技术 | 2601篇 |
技术理论 | 3篇 |
综合类 | 3364篇 |
化学工业 | 4180篇 |
金属工艺 | 4900篇 |
机械仪表 | 3516篇 |
建筑科学 | 2456篇 |
矿业工程 | 1010篇 |
能源动力 | 1066篇 |
轻工业 | 2358篇 |
水利工程 | 779篇 |
石油天然气 | 3648篇 |
武器工业 | 277篇 |
无线电 | 3852篇 |
一般工业技术 | 3543篇 |
冶金工业 | 1216篇 |
原子能技术 | 527篇 |
自动化技术 | 5772篇 |
出版年
2024年 | 67篇 |
2023年 | 327篇 |
2022年 | 578篇 |
2021年 | 876篇 |
2020年 | 660篇 |
2019年 | 494篇 |
2018年 | 512篇 |
2017年 | 595篇 |
2016年 | 544篇 |
2015年 | 777篇 |
2014年 | 1168篇 |
2013年 | 1179篇 |
2012年 | 1454篇 |
2011年 | 4073篇 |
2010年 | 2503篇 |
2009年 | 1757篇 |
2008年 | 1896篇 |
2007年 | 1535篇 |
2006年 | 1777篇 |
2005年 | 1725篇 |
2004年 | 4019篇 |
2003年 | 2148篇 |
2002年 | 2014篇 |
2001年 | 1539篇 |
2000年 | 996篇 |
1999年 | 1559篇 |
1998年 | 1139篇 |
1997年 | 1073篇 |
1996年 | 679篇 |
1995年 | 586篇 |
1994年 | 476篇 |
1993年 | 1240篇 |
1992年 | 946篇 |
1991年 | 538篇 |
1990年 | 552篇 |
1989年 | 455篇 |
1988年 | 240篇 |
1987年 | 66篇 |
1986年 | 64篇 |
1985年 | 42篇 |
1984年 | 30篇 |
1983年 | 22篇 |
1982年 | 30篇 |
1981年 | 14篇 |
1980年 | 32篇 |
1979年 | 14篇 |
1978年 | 5篇 |
1977年 | 14篇 |
1973年 | 6篇 |
1971年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
81.
CCD型束流截面探测器的主要特点是使用电荷耦合器件做传感器,用束流同步光中的可见光成份做为信号源。该探测器同时具有模拟量和数字量两种输出,工作周期短,速度高,不影响束团粒子寿命,在电子储存环物理运行中,是一种有效的探测设备。 相似文献
82.
产品数据管理(PDM)实施中的存在问题与对策 总被引:7,自引:2,他引:5
论述了产品数据管理(PDM)技术发展的历史,讨论了实施PDM的两种目标,并指出PDM在制造业信息化中的地位与作用,阐述了PDM重在实施的原因,根据作者经验,总结了我国企业在实施PDM中存在的4个问题,并从用户和软件厂商两个角度提出了解决这些问题的对策。 相似文献
83.
84.
85.
86.
XIAO Chang-jiang SUN Ming ZHOU Hong-yan LIU Sui-xin LONG Kai-chao HE Fei LI Tong 《中南工业大学学报(英文版)》2005,12(Z1)
Objective Study on the effect of NF-κB in ox-LDL injured HUVEC-304 and the intervention with the serum of Tongmai Decoction. Methods Tongmai Decoction herbage-contained serum was made by the serum pharmacology methods, then the HUVEC-304 cells were divided into 5 groups and incubated for 24 h: 1) normal group;2) fetal calf serum group; 3) ox-LDL group; 4) simvastatin group; 5) Tongmai Decoction group. RT-PCR was used to determine the mRNA of NF-κB in the cells, Western Blot Assay was used to determine the protein content of NF-κB in the cells. Results 1) Compared with the cells in normal group and serum control group , the endothelial cells in ox-LDL group are seriously injured, while those in Tongmai Decoction group grow better; 2) Compared with the cells in normal group and fetal calf serum group, the expressions of NF-κB gene and protein are up-regulated in ox-LDL group(P<0.05, P<0.01); 3) Compared with the cells in ox-LDL group, the expression of NF-κB gene and protein in Tongmai Decoction group are significantly down-regulated, there is no difference between Tongmai Decoction group and simvastatin group(P>0.05). Conclusion Tongmai Decoction can protect the injured endothelial cells, up-regulate the expressions of NF-κB gene and protein content. 相似文献
87.
Shaofeng Wang Jianwei Xu Yuejin Tong Lin Wang Chaobin He 《Polymer International》2005,54(9):1268-1274
A novel cholesterol‐imprinted polymer (CMIP‐H) was prepared by a hybrid method of covalent imprinting and non‐covalent imprinting. This approach involves the copolymerization of a template‐containing monomer, cholesteryl 2‐hydroxyethyl methacrylate carbonate, and a cross‐linker, followed by hydrolysis to afford a flexible guest‐binding site accompanied with the easy and efficient removal of a ‘sacrificial spacer’. The effect of solvent on the binding capacity of CMIP‐H towards cholesterol was studied, indicating that a good binding capacity towards cholesterol could be achieved in a less‐polar solvent. The binding experiments of CMIP‐H towards a series of structural analogues of cholesterol, including cholesterol acetate, progesterone and stigmasterol, were carried out in hexane. The results showed that CMIP‐H almost did not bind cholesterol acetate at all because the hydrogen‐bonding site is blocked. It exhibited a similar binding towards both cholesterol and stigmasterol, but much higher binding towards progesterone. Copyright © 2005 Society of Chemical Industry 相似文献
88.
89.
提出了用三角函数表示的一类用于油田开发指标预测的增长曲线共6条,从而进一步完善和丰富了现有的增长曲线法。提出和推导了它们的Np-t、Qt-t、Qt-Np关系式、(Np/NRmax)Qtmax准数计算式以及参数求解式。其特片研究表明,它们特征相近;(Np/NRamx)Qtmax变化范围为0-0.36785,属于峰值产量出现在油田开发初期的情况,其Qt-Np关系为一不对称的拱形曲线。提出了求取曲线参数的过原点重复线性回归法。双河油田的实例表明该方法有一定实用价值。 相似文献
90.
Dongchang Sun Liyong Tong 《International journal for numerical methods in engineering》2004,60(11):1911-1932
A novel finite element model is presented for static and dynamic analysis of composite plates integrated with a laminated piezoelectric layer, a host laminated composite plate and an adhesive layer between them. A new adhesive element is developed which includes both peel and shear effects in the adhesive layer based on first‐order shear deformation plate theory. The thin adhesive layer between the piezoelectric layer and the host plate is modelled by assuming that it carries constant shear and peel strains throughout its thickness. In addition, a weighted static shape control scheme for finding the optimal voltage distribution for static shape control is given. By selecting different weighting matrices, a variety of items such as displacements, slopes, curvatures, strains and even generalized forces, can be included in finding the optimal actuating voltage for static shape control. The present model is validated by comparing with those results available in the literature. The numerical results show that the weighted linear least method can give a satisfactory voltage distribution to best match the desired shape. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献