全文获取类型
收费全文 | 49893篇 |
免费 | 3971篇 |
国内免费 | 2057篇 |
专业分类
电工技术 | 2664篇 |
技术理论 | 8篇 |
综合类 | 3082篇 |
化学工业 | 8779篇 |
金属工艺 | 2762篇 |
机械仪表 | 3277篇 |
建筑科学 | 3731篇 |
矿业工程 | 1718篇 |
能源动力 | 1450篇 |
轻工业 | 2816篇 |
水利工程 | 795篇 |
石油天然气 | 3923篇 |
武器工业 | 448篇 |
无线电 | 5361篇 |
一般工业技术 | 5973篇 |
冶金工业 | 2516篇 |
原子能技术 | 502篇 |
自动化技术 | 6116篇 |
出版年
2024年 | 242篇 |
2023年 | 925篇 |
2022年 | 1508篇 |
2021年 | 2049篇 |
2020年 | 1585篇 |
2019年 | 1338篇 |
2018年 | 1499篇 |
2017年 | 1675篇 |
2016年 | 1477篇 |
2015年 | 1956篇 |
2014年 | 2398篇 |
2013年 | 2926篇 |
2012年 | 2983篇 |
2011年 | 3361篇 |
2010年 | 2801篇 |
2009年 | 2733篇 |
2008年 | 2808篇 |
2007年 | 2574篇 |
2006年 | 2636篇 |
2005年 | 2312篇 |
2004年 | 1460篇 |
2003年 | 1362篇 |
2002年 | 1243篇 |
2001年 | 1110篇 |
2000年 | 1232篇 |
1999年 | 1448篇 |
1998年 | 1135篇 |
1997年 | 956篇 |
1996年 | 863篇 |
1995年 | 771篇 |
1994年 | 635篇 |
1993年 | 475篇 |
1992年 | 364篇 |
1991年 | 264篇 |
1990年 | 223篇 |
1989年 | 154篇 |
1988年 | 136篇 |
1987年 | 88篇 |
1986年 | 63篇 |
1985年 | 35篇 |
1984年 | 29篇 |
1983年 | 31篇 |
1982年 | 25篇 |
1981年 | 15篇 |
1980年 | 11篇 |
1979年 | 5篇 |
1978年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
1.
对己二腈工业反应器提出了两釜串联带回流的模型,通过模拟计算得出模型的级间返混系数 f=6的结论。该模型能较好地预测工业反应器中物料组分浓度变化和气、液两相的流动特性;指出了现工业反应器的鼓泡中和段体积偏小是造成己二酸浓度偏高的关键;提出了可以通过增加串连一个鼓泡预反应段的改造方案,能有效地降低己二酸的浓度,从7%降至4%左右,从而能较好地减缓腐蚀和结焦。 相似文献
2.
实体造型中的几何约束 总被引:5,自引:0,他引:5
实体造型是一个基于约束的过程,完成从功能约束到几何约束、再到代数约束的转化而得到实体模型。本文讨论了几何约束的层次性及其表示,并且对几何约束同设计意图的关系进行了研究,提出了基于CSG/GCG/B-rep的模型表示。 相似文献
3.
Liang Y.C. Wenjiang Zeng Pick Hong Ong Zhaoxia Gao Jun Cai Balasubramanian N. 《Electron Device Letters, IEEE》2002,23(12):700-703
In this letter, a concise process technology is proposed for the first time to enable the fabrication of good quality three-dimensional (3-D) suspended radio frequency (RF) micro-inductors on bulk silicon, without utilizing the lithography process on sidewall and trench-bottom patterning. Samples were fabricated to demonstrate the applicability of the proposed process technology. 相似文献
4.
Successful operation of the Synchronous Overlap and Add (SOLA) algorithm for Time Scale Modification (TSM) of speech is closely tied to the proper choice of parameters. This paper investigates the quality of time scale modified speech under different values of primary parameters. Based on Mean Opinion Score (MOS) tests and Bark Spectral Distortion (BSD) measure, the proper choices of synthesis shift (Ss) and the duration of the shift search interval (K max?) are given experimentally. The conclusions can be helpful for operating the SOLA algorithm for time scale modification of speech. 相似文献
5.
6.
针对熟料饲料油隔泵供料压力不稳定、消耗油及备件量大、检修频繁的情况,着重介绍和探讨了对新型离心泵的选型、可行性分析、过流件材质及密封的选择、新型饲料泵的成功应用. 相似文献
7.
Kollipara R.T. Arodzero A. Bashindzhagyan G. Brau J.E. Frey R. Gao D. Mason D. Sinev N. Strom D. Yang X. 《IEEE transactions on nuclear science》1995,42(2):92-101
The SSC GEM silicon Central Tracker design incorporated 18-cm long single-sided AC-coupled silicon microstrip ladders. Compared to the 12-cm long ladders considered in the preliminary stages of the tracker design, the 18-cm long ladders have the advantage of reduced cost, channel count and overall power consumption, and led to a simplified tracker assembly. However, such long ships also present the challenge of maintaining satisfactory performance. The increased capacitance and series resistance contribute to lower signal-to-noise ratios, longer time walk, higher power consumption per channel and increased probability of crosstalk to neighboring channels. In this paper, an accurate method to calculate the geometric capacitance of the AC-coupled microstrips is presented and the calculated results are compared with measurements, SPICE simulations are performed to predict the noise, the extent of interstrip capacitive coupling and the dispersion of the detector signal due to the finite series resistance of the metal strips and the long length of the detector. The influence of the preamplifier current and the shaping time on the signal and noise levels is also presented. The study concludes that the 18-cm long ladders can successfully satisfy the performance goals of the GEM silicon Central Tracker 相似文献
8.
9.
Polymorphonuclear leucocyte (PMNL) accumulation in extravascular tissues and inflammatory exudates is dependent on their migration through blood vessel endothelium and then through connective tissue. Previously we utilized a barrier of human synovial and dermal fibroblasts (HSF or HDF) grown on microporous filters, as a model of PMNL migration through connective tissue. Those studies showed that beta 2 (CD18) and the beta 1 integrins, very late activation antigen-5 (VLA-5) and VLA-6, in part mediate this PMNL migration. Here we report that VLA-4, which can also be expressed at low levels on activated PMNL, is also involved in PMNL migration induced by C5a through fibroblast (HSF and HDF) barriers, because monoclonal antibody (mAb) to VLA-4 significantly inhibited (by 20-30%) PMNL migration. Blocking the function of CD18, VLA-5 or VLA-6 was not required for detection of the VLA-4-mediated migration. Combination treatment with mAb to VLA-4 and with mAb to VLA-5 or to VLA-6 further inhibited PMNL migration, irrespective of whether CD11/CD18 mechanisms were blocked with anti-CD18 mAb or not. Treatment of PMNL with a peptide based on the VLA-4-binding domain in the CS-1 fragment of fibronectin, but not a control peptide, inhibited PMNL migration to a comparable extent to treatment with mAb to VLA-4. A low level of VLA-4 was expressed on C5a-activated PMNL, detected by immunofluorescence flow cytometry. These results suggest that VLA-4 can be mobilized by human peripheral blood PMNL and can, in addition to VLA-5, VLA-6 and CD11/CD18 integrins, mediate PMNL migration through connective tissue. This is in marked contrast to PMNL transendothelial migration, where beta 1 integrins appear to play no significant role. 相似文献
10.
介绍了军用飞机电子吊舱蒸汽压缩制冷环境控制系统的工作特点,给出了电子膨胀阀在电子吊舱地面模拟制冷系统中的初步试验研究结果。 相似文献