全文获取类型
收费全文 | 12747篇 |
免费 | 1013篇 |
国内免费 | 463篇 |
专业分类
电工技术 | 657篇 |
综合类 | 817篇 |
化学工业 | 2193篇 |
金属工艺 | 754篇 |
机械仪表 | 768篇 |
建筑科学 | 1026篇 |
矿业工程 | 356篇 |
能源动力 | 330篇 |
轻工业 | 606篇 |
水利工程 | 194篇 |
石油天然气 | 829篇 |
武器工业 | 75篇 |
无线电 | 1462篇 |
一般工业技术 | 1730篇 |
冶金工业 | 694篇 |
原子能技术 | 119篇 |
自动化技术 | 1613篇 |
出版年
2024年 | 68篇 |
2023年 | 276篇 |
2022年 | 345篇 |
2021年 | 512篇 |
2020年 | 426篇 |
2019年 | 330篇 |
2018年 | 416篇 |
2017年 | 445篇 |
2016年 | 417篇 |
2015年 | 456篇 |
2014年 | 596篇 |
2013年 | 685篇 |
2012年 | 760篇 |
2011年 | 839篇 |
2010年 | 680篇 |
2009年 | 688篇 |
2008年 | 699篇 |
2007年 | 623篇 |
2006年 | 685篇 |
2005年 | 628篇 |
2004年 | 422篇 |
2003年 | 358篇 |
2002年 | 333篇 |
2001年 | 250篇 |
2000年 | 287篇 |
1999年 | 337篇 |
1998年 | 285篇 |
1997年 | 275篇 |
1996年 | 234篇 |
1995年 | 177篇 |
1994年 | 165篇 |
1993年 | 126篇 |
1992年 | 99篇 |
1991年 | 74篇 |
1990年 | 77篇 |
1989年 | 32篇 |
1988年 | 37篇 |
1987年 | 24篇 |
1986年 | 19篇 |
1985年 | 5篇 |
1984年 | 7篇 |
1983年 | 8篇 |
1982年 | 6篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Journal of Computer Science and Technology - DOACROSS loops are significant parts in many important scientific and engineering applications, which are generally exploited pipeline/wave-front... 相似文献
2.
In the field of images and imaging, super-resolution (SR) reconstruction of images is a technique that converts one or more low-resolution (LR) images into a highresolution (HR) image. The classical two types of SR methods are mainly based on applying a single image or multiple images captured by a single camera. Microarray camera has the characteristics of small size, multi views, and the possibility of applying to portable devices. It has become a research hotspot in image processing. In this paper, we propose a SR reconstruction of images based on a microarray camera for sharpening and registration processing of array images. The array images are interpolated to obtain a HR image initially followed by a convolution neural network (CNN) procedure for enhancement. The convolution layers of our convolution neural network are 3×3 or 1×1 layers, of which the 1×1 layers are used to improve the network performance particularly. A bottleneck structure is applied to reduce the parameter numbers of the nonlinear mapping and to improve the nonlinear capability of the whole network. Finally, we use a 3×3 deconvolution layer to significantly reduce the number of parameters compared to the deconvolution layer of FSRCNN-s. The experiments show that the proposed method can not only ameliorate effectively the texture quality of the target image based on the array images information, but also further enhance the quality of the initial high resolution image by the improved CNN. 相似文献
3.
In this research, maleic anhydride-α-octadecene copolymer and its derivative with phenylethylamine was synthesized and its effect on the crystallization of paraffins was investigated. This derivative, when added into second cut of vacuum gas oil and forth cut of vacuum gas oil, increases the size and improves aggregation of paraffin crystals observed by polarizing light microscopy, increases onset temperature and enthalpy of paraffin crystallization determined by differential scanning calorimetry, improves the dewaxing efficiency with dosage of 100?ppm explored by MEK-toluene dewaxing. 相似文献
4.
In colloidal suspensions of silica, particles undergo constant collisions. By controlling various parameters, the repulsive barrier can be reduced, thereby substantially increasing the number of collision‐induced dimerization events. Xia and co‐workers report on p. 1627 that the dimers could be arrested and then permanently fixed by introducing a small amount of fresh tetraethylorthosilicate into the colloidal suspension, with monodisperse dimer yields of up to 50 %. This yield could be increased to 80 % by centrifugation in a density gradient medium. When fresh tetraethylorthosilicate is introduced into a colloidal suspension of silica spheres, it hydrolyzes and condenses in situ to arrest and fix the dimers resulting from constant collisions between the spheres. By optimizing the experimental parameters (including the length of aging time) and the diameter of the silica spheres, as well as the concentrations of counterions, water, and ammonia, it is possible to routinely produce monodisperse dimers with a yield as high as 50 %. When combined with centrifugation using a density gradient medium, the yield of such dimers could be further increased to 80 %. It is believed that this method will provide a simple and versatile approach to the high‐volume production of dimers from spherical colloids composed of different materials. These dimers may find widespread use in a range of applications such as fabrication of photonic crystals and fundamental studies related to colloidal science. 相似文献
5.
Qin Song Zou Xubiao Zhong Yan Zhang Zhongdong 《中国炼油与石油化工》2006,(1):31-35
1 Introduction Propylene as an important feedstock for organic chemicals is mainly originated from steam cracking and catalytic cracking processes. During the FCC process the propylene content varies with the FCC catalyst and process technology adopted, resulting in significant difference in propylene concentration in the cracked product——LPG. The conventional FCC pro- cess generally gives a propylene yield of around 4%, while the FCC process with maximization of propylene yield can in… 相似文献
6.
7.
Laparoscopic retroperitoneal lymph node dissection is a new surgical procedure used to enhance staging in men with clinical stage I nonseminomatous germ cell tumors of the testis. The procedure has been performed in a limited number of patients at several centers with extensive laparoscopic experience. Laparoscopic retroperitoneal lymphadenectomy is a technically demanding procedure which can be successfully completed in the majority of patients. However, the risk of complications is greater than in patients who undergo standard open retroperitoneal lymph node dissection. The primary advantage of a laparoscopic approach is shortened hospitalization and rapid return to normal activity. The role of laparoscopy in the management of patients with testis malignancy has not been defined. The use of this staging procedure may help minimize the need for surveillance studies following surgery and may be best utilized in men with a lower likelihood of nodal metastases. Ultimately, prospective study in large groups of patients will be necessary to determine the role of laparoscopic retroperitoneal lymph node dissection in patients with testis cancer. 相似文献
8.
9.
随着国民经济转型的发展,城市化进程加快,城市水土流失也将越来越严重。搞好城市建设与水土保持生态环境建设的关系,尤为重要。城市建设必须接受《水土保持法》的制约;应与自然景观相协调,维护生物物种的多样性;必须维护河流水系形态的平衡;城市建设应与城郊防护林体系及城市绿地紧密结合;田园城市模式应成为新城区的主体;城市建设要保护好黑土地的水土保持生态环境。 相似文献
10.
测试与分析了两种塑料管材的拉伸与弯曲性能、热变形温度、结晶性和化学组成,分析结果表明:管材B较管材A具有更高模量与热变形温度,但管材B较高的分子量与较小的分子量分布抑制管材产品内在的均匀性,且管材B中的α晶在高温下向β晶的转变可能会影响管材长期使用性能. 相似文献