首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   3160篇
  免费   171篇
  国内免费   16篇
电工技术   83篇
综合类   10篇
化学工业   611篇
金属工艺   30篇
机械仪表   88篇
建筑科学   87篇
矿业工程   12篇
能源动力   91篇
轻工业   195篇
水利工程   10篇
石油天然气   8篇
武器工业   3篇
无线电   606篇
一般工业技术   626篇
冶金工业   319篇
原子能技术   25篇
自动化技术   543篇
  2023年   14篇
  2022年   37篇
  2021年   78篇
  2020年   56篇
  2019年   45篇
  2018年   62篇
  2017年   72篇
  2016年   80篇
  2015年   76篇
  2014年   92篇
  2013年   203篇
  2012年   160篇
  2011年   194篇
  2010年   162篇
  2009年   200篇
  2008年   181篇
  2007年   175篇
  2006年   107篇
  2005年   110篇
  2004年   109篇
  2003年   88篇
  2002年   78篇
  2001年   71篇
  2000年   60篇
  1999年   66篇
  1998年   125篇
  1997年   106篇
  1996年   70篇
  1995年   60篇
  1994年   43篇
  1993年   42篇
  1992年   31篇
  1991年   32篇
  1990年   40篇
  1989年   27篇
  1988年   39篇
  1987年   25篇
  1986年   18篇
  1985年   22篇
  1984年   9篇
  1983年   13篇
  1982年   4篇
  1981年   10篇
  1980年   6篇
  1979年   6篇
  1977年   5篇
  1976年   10篇
  1975年   8篇
  1973年   5篇
  1971年   3篇
排序方式: 共有3347条查询结果,搜索用时 703 毫秒
1.
The low overall survival rate of patients with pancreatic cancer has driven research to seek a new therapeutic protocol. Radiotherapy (RT) is frequently an option in the neoadjuvant or palliative settings for pancreatic cancer treatment. This study explored the effect of RT protocols on the tumor microenvironment (TME) and their consequent impact on anti-programmed cell death ligand-1 (PD-L1) therapy. Using a murine orthotopic pancreatic tumor model, UN-KC-6141, RT-disturbed TME was examined by immunohistochemical staining. The results showed that ablative RT is more effective than fractionated RT at recruiting T cells. On the other hand, fractionated RT induces more myeloid-derived suppressor cell infiltration than ablative RT. The RT-disturbed TME presents a higher perfusion rate per vessel. The increase in vessel perfusion is associated with a higher amount of anti-PD-L1 antibody being delivered to the tumor. Animal survival is increased by anti-PD-L1 therapy after ablative RT, with 67% of treated animals surviving more than 30 days after tumor inoculation compared to a median survival time of 16.5 days for the control group. Splenocytes isolated from surviving animals were specifically cytotoxic for UN-KC-6141 cells. We conclude that the ablative RT-induced TME is more suited than conventional RT-induced TME to combination therapy with immune checkpoint blockade.  相似文献   
2.
3.
Cases of isolated hepatic tuberculosis (TB) are rare. The diagnosis is often delayed or missed because of nonspecific symptoms and laboratory findings. Besides, the disease is extremely rare even in a country where TB is an alarming public health problem. This report demonstrates the difficulty in correctly diagnosing local hepatic TB. We report the case of a 62‐year‐old male patient with end‐stage renal disease treated with hemodialysis, who developed 2 months of abdominal distension and general anorexia, with hyperechoic hepatic lesions on ultrasound. Computed tomography suspected multiple liver tumors. The liver biopsy finally led to the diagnosis of TB of the liver without other involvements. We conclude that isolated hepatic TB is one of the rare forms of extrapulmonary TB in dialysis patients. A greater awareness of this rare clinical entity may prevent needless surgical interventions.  相似文献   
4.
5.
Minds and Machines - To address the rising concern that algorithmic decision-making may reinforce discriminatory biases, researchers have proposed many notions of fairness and corresponding...  相似文献   
6.
A dual-mode ring bandpass filter with two pairs of capacitors has been designed. The capacitors are used to control the location of the even- and odd-mode frequencies independently, allowing weak coupling for narrow-band filter design with realizable capacitance values. Theoretical expressions have been derived for these frequencies. A 4% bandwidth bandpass filter centered at 1.9 GHz was designed and tested with good agreement between theoretical and measured results.  相似文献   
7.
Speed superiority of scaled double-gate CMOS   总被引:1,自引:0,他引:1  
Unloaded ring-oscillator simulations, performed with a generic process/physics-based compact model for double-gate (DG) MOSFETs and supplemented with model-predicted on-state currents and gate capacitances for varying supply voltages (VDD), are used to show and explain the speed superiority of extremely scaled DG CMOS over the single-gate (e.g., bulk-Si) counterpart. The DG superiority for unloaded circuits is most substantive for low VDD < ~1 V  相似文献   
8.
Based on a high-performance liquid chromatographic pump, we have built a device that allows recirculation of DNA through a 63-microm orifice with ensuing fractionation to a minimum fragment size of approximately 300 base pairs. Residence time of the DNA fragments in the converging flow created by a sudden contraction was found to be sufficiently long to allow extension of the DNA molecules into a highly extended conformation and, hence, breakage to occur at midpoint. In most instances, 30 passages sufficed to obtain a narrow size distribution, with >90% of the fragments lying within a 2-fold size distribution. The shear rate required to achieve breakage was found to be inversely proportional to the 1.0 power of the molecular weight. Compared with a restriction digest, up to 40% of all fragments could be cloned directly, with only marginal improvements in cloning efficiency having been observed upon prior end repair with Klenow, T4 polymerase or T4 polynucleotide kinase. Sequencing revealed a fairly random distribution of the fragments.  相似文献   
9.
Chiang  K.S. 《Electronics letters》1987,23(3):112-113
A criterion for the local taper angle of a low-loss single-mode fibre coupler is established by considering the dominant mode coupling in the coupler taper. Effects due to structure parameters, such as cladding/core thickness ratio, corecladding index difference and core separation, are investigated. It is found that the criterion for the coupler taper can be well approximated by that for the single-mode fibre taper with the same structure parameters.  相似文献   
10.
This paper investigates the properties of the on-wafer interconnects built in a 0.18-/spl mu/m CMOS technology for RF applications. A scalable equivalent circuit model is developed. The model parameters are extracted directly from the on-wafer measurements and formulated into empirical expressions. The expressions are in functions of the length and the width of the interconnects. The proposed model can be easily implemented into commercial RF circuit simulators. It provides a novel solution to include the frequency-variant characteristics into a circuit simulation. The silicon-verified accuracy is proved to be up to 25 GHz with an average error less than 2%. Additionally, equivalent circuit model for longer wires can be obtained by cascading smaller subsections together. The scalability of the propose model is demonstrated.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号