全文获取类型
收费全文 | 5632篇 |
免费 | 531篇 |
国内免费 | 305篇 |
学科分类
工业技术 | 6468篇 |
出版年
2024年 | 29篇 |
2023年 | 83篇 |
2022年 | 215篇 |
2021年 | 220篇 |
2020年 | 184篇 |
2019年 | 122篇 |
2018年 | 131篇 |
2017年 | 161篇 |
2016年 | 138篇 |
2015年 | 220篇 |
2014年 | 272篇 |
2013年 | 290篇 |
2012年 | 379篇 |
2011年 | 335篇 |
2010年 | 347篇 |
2009年 | 327篇 |
2008年 | 380篇 |
2007年 | 322篇 |
2006年 | 280篇 |
2005年 | 209篇 |
2004年 | 185篇 |
2003年 | 117篇 |
2002年 | 111篇 |
2001年 | 111篇 |
2000年 | 71篇 |
1999年 | 44篇 |
1998年 | 287篇 |
1997年 | 203篇 |
1996年 | 146篇 |
1995年 | 78篇 |
1994年 | 50篇 |
1993年 | 67篇 |
1992年 | 16篇 |
1991年 | 12篇 |
1990年 | 8篇 |
1989年 | 11篇 |
1988年 | 16篇 |
1987年 | 14篇 |
1986年 | 7篇 |
1985年 | 11篇 |
1982年 | 7篇 |
1981年 | 14篇 |
1980年 | 21篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 65篇 |
1976年 | 136篇 |
1975年 | 3篇 |
1965年 | 2篇 |
1951年 | 2篇 |
排序方式: 共有6468条查询结果,搜索用时 0 毫秒
81.
LG Kupchinski? IuA Barshte?n BG Pogodaev AI Treshinski? 《Canadian Metallurgical Quarterly》1976,(3):80-84
A study was made of a possibility of using Soviet made membranes "Vladipor" with a pore diameter of 16--17 nm for the purpose of concentration and purification of antigenic extracts from stab cultures of S. typhi obtained by the action of typsin, hydrogen peroxide and detergents. Preparations, complete by antigenic structure, were obtained by ultrafiltration, with a good yield. The maximal rate of ultrafiltration was noted in case of "peroxide" antigenic preparations. The use of diafiltration provided a significant reduction of the ash content in the end products. 相似文献
82.
Circulating plasma progesterone (P) has been quantitatively controlled in the rat "model" through highly specific binding by treatment with anti-P (A-P). Knowing the constant, which characterizes the binding of P to A-P in plasma, sequential assays of circulating A-P and A-P bound total P (Pt) revealed the levels of the biologically active unbound P (Pu). The studies showed that at different stages of gestation the mechanisms through which A-P reduces Pu and terminates pregnancy are the same. However, the doses of AP which effectively reduce Pu and also the critical levels of Pu at which pregnancy terminates are different. The moderate and transient physiologic P-withdrawal (Pw) at midterm permits the continuation of normal gestation, but pregnancy is terminated by a drastic and sustained reduction in Pu. In contrast, when Pu is only slightly and briefly reduced below physiologic levels, pregnancy continues and only retarded conceptus growth signals that Pw occurred. Apparently Pw has to be controlled and measured with "razor's-edge" precision to fully expose and define the regulatory significance of this steroid in the maintenance and termination of pregnancy. Short of this precision, the key regulator of the pregnant uterus will remain buried, as it has been during 40 years, in controversial findings. 相似文献
83.
Histories of deliveries and development records of 44 newborns with penumopathies who had died on the first days of life in the presence of phenomena of the syndrome of respiratory disorder were analysed and the newborns' lungs were morphologically investigated. The investigation made it possible to single out the following forms of pneumopathy in newborns: edematous-hemorrhagic, hyaline, atelectatic, aspirated, and mixed. In the majority of cases the syndrome of respiratory disorder was a sequela of hypoxia of the intrauterine origin which continued during the first hours and days of life after birth. Such "primary asphyxia" may lead to the development of pneumopathy in a neonate. On the other hand, "secondary asphyxia" in many cases represent sequelae of penumopathy destructural and functional immaturity of the pulmonary tissue, hypoxia, a higher permeability of vessels of the microcirculatory bed, spasm of small pulmonary arteris contributed considerably to the development of penumopathies. 相似文献
84.
85.
86.
目的应用高压水射流进行混凝土构件表面处理前确定机械的初始参数。实现对处理深度全面合理的控制.方法用AJP-E25135型高压泵,RG-2002HNDF型、口径为0.25mm七喷嘴旋转喷枪,对36组不同的初始参数、同批制作的砾石混凝土试块进行了高压水射流表面处理试验,并运用人工神经网络技术,对试验数据进行理论分析.结果建立了压力、靶距、口径、S/A(砂率)与处理深度关系的预测模型并把模型的预测结果与实验结果进行了比较,平均相对误差为0.0005.结论模型能够满足工程实际需要.可用于混凝土构件表面处理深度的估计与分析,以及特定处理深度条件下初始参数的预测.并可广泛应用于高压水表面处理深度模型的参数优化选择。智能化控制等领域. 相似文献
87.
88.
高炉紫铜风口是由铸造本体和轧制端头两个部分采用TIG手工焊接而成。随着高炉的扩容,为了延长风口使用寿命,提高焊缝物理和力学性能,成功采用了MIG自动焊,满足了高炉生产需求。 相似文献
89.
650轧辊的堆焊修复 总被引:1,自引:0,他引:1
对轧辊断裂部位进行了分析,找出了裂纹形成的主要原因。通过采取焊前预热、低氢焊接和焊后热处理等措施,成功地实现了650轧辊端头断裂的堆焊修复,即以焊代换。同时,延长了轧辊服役周期。 相似文献
90.
为了使得计算机能自动生成表达力丰富的三维场景的艺术绘制,提出了一种基于Shader的多重绘制模型,并采用了多重绘制的协调、参数空间的纹理铺陈、基于色调的表现控制等技术来进行模拟.引入多重绘制可以同时采用对象空间的绘制和图像空间的绘制,通过纹理铺陈描述语言Shader,用户可以定义自己的纹理和笔划来表现三维和二维场景.不同于传统的Shader,基于Shader的多重绘制模型采用光亮度、材质颜色等作为输入,由用户自行决定绘制结果的输入.这一用户可定制性的引入大大增强了艺术绘制的表现能力.该模型已经在一个建筑设计系统中得到实现,以钢笔画为表现媒介的图例表明该模型模拟效果令人满意. 相似文献