全文获取类型
收费全文 | 4323篇 |
免费 | 132篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 65篇 |
综合类 | 5篇 |
化学工业 | 468篇 |
金属工艺 | 33篇 |
机械仪表 | 73篇 |
建筑科学 | 64篇 |
矿业工程 | 2篇 |
能源动力 | 74篇 |
轻工业 | 132篇 |
水利工程 | 32篇 |
石油天然气 | 1篇 |
无线电 | 461篇 |
一般工业技术 | 502篇 |
冶金工业 | 2138篇 |
原子能技术 | 20篇 |
自动化技术 | 393篇 |
出版年
2023年 | 10篇 |
2022年 | 31篇 |
2021年 | 47篇 |
2020年 | 36篇 |
2019年 | 27篇 |
2018年 | 46篇 |
2017年 | 46篇 |
2016年 | 59篇 |
2015年 | 53篇 |
2014年 | 74篇 |
2013年 | 179篇 |
2012年 | 112篇 |
2011年 | 130篇 |
2010年 | 118篇 |
2009年 | 142篇 |
2008年 | 128篇 |
2007年 | 134篇 |
2006年 | 81篇 |
2005年 | 91篇 |
2004年 | 80篇 |
2003年 | 66篇 |
2002年 | 74篇 |
2001年 | 55篇 |
2000年 | 44篇 |
1999年 | 112篇 |
1998年 | 712篇 |
1997年 | 465篇 |
1996年 | 271篇 |
1995年 | 151篇 |
1994年 | 127篇 |
1993年 | 135篇 |
1992年 | 43篇 |
1991年 | 52篇 |
1990年 | 54篇 |
1989年 | 50篇 |
1988年 | 64篇 |
1987年 | 41篇 |
1986年 | 32篇 |
1985年 | 34篇 |
1984年 | 10篇 |
1983年 | 14篇 |
1982年 | 11篇 |
1981年 | 17篇 |
1980年 | 18篇 |
1979年 | 6篇 |
1977年 | 47篇 |
1976年 | 105篇 |
1975年 | 9篇 |
1973年 | 3篇 |
1955年 | 4篇 |
排序方式: 共有4463条查询结果,搜索用时 15 毫秒
1.
Yu-Hung Lee Ching-Fang Yu Ying-Chieh Yang Ji-Hong Hong Chi-Shiun Chiang 《International journal of molecular sciences》2021,22(4)
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.
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
4.
5.
BACKGROUND: The enterococci have become important nosocomial pathogens. They can cause multiple site infections and enterococcal bacteremia becomes more frequently associated with a high mortality rate. Previous studies of enterococcal bacteremia showed a variety of results. To establish the significance and importance of enterococci as nosocomial pathogens in this hospital, to characterize their clinical pictures and to search for the risk factors for mortality, this retrospective study was performed. METHODS: There were 208 cases of enterococcal bacteremia which occurred from 1988 to 1992. Twenty-seven cases had no medical charts, dismissing possibility of evaluation. Finally, 181 cases of enterococcal bacteremia were analysed. RESULTS: One hundred and eighteen episodes were nosocomial infections. Polymicrobial bacteremia occurred in 68.5% of the patients and the most common co-isolate was Pseudomonas aeruginosa. Those patients (78.5%) with underlying diseases and malignancies were the most common underlying problems. The portal of entry could be found in 69.6 percent of patients, with the gastrointestinal tract the most common sources. Antimicrobial susceptibility testing showed high gentamicin resistance rate (89.5%), and ampicillin still had about 80 percent sensitivity rate. The group who received specific antibiotic therapy for enterococcus showed lower mortality (36.4% versus 47.6%). Only one case had infective endocarditis. Forty-nine patients suffered from septic shock, the cause of 30 deaths. Totally 75 patients died during hospitalization. Besides sepsis, another major cause of death was their underlying diseases itself. CONCLUSIONS: Enterococci have no doubt become important nosocomial pathogens and enterococcal bacteremia were associated with high mortality, especially in elderly patients with underlying diseases such as malignancy or diabetes. When clinically dealing with sepsis from the gastrointestinal or biliary tract, especially when previous cephalosporins therapy showed no response, the possibility of enterococcal bacteremia should always be considered. 相似文献
6.
PJ Oefner SP Hunicke-Smith L Chiang F Dietrich J Mulligan RW Davis 《Canadian Metallurgical Quarterly》1996,24(20):3879-3886
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
7.
NF Saba JD Sweeney LC Penn JC Lawton RL Yankee CH Huang MS Schanfield 《Canadian Metallurgical Quarterly》1997,37(3):321-324
PURPOSE: We report a case of postoperative reparalysis in the recovery room, following nebulized epinephrine. The patient was pharmacologically reversed with edrophonium after paralysis with rocuronium. CLINICAL FINDINGS: A 12-yr-old girl developed postoperative reparalysis following the intraoperative administration of rocuronium. A total of 0.92 mg.kg-1 rocuronium was administered. After surgery, pharmacological reversal was achieved with 20 mg edrophonium with 0.15 mg atropine sulfate iv 35 min after the last administration of rocuronium. Muscular relaxation was monitored using an ulnar peripheral nerve stimulator (PNS). After reversal, a full train-of-four and sustained tetanus at 50 Hz were present. In the recovery room, following nebulized epinephrine, the patient became apneic. The patient was paralyzed and an ulnar PNS demonstrated only one faint twitch. The paralysis was reversed with 1.5 mg neostigmine with 0.3 mg glycopyrrolate. CONCLUSION: Postoperative reparalysis following rocuronium may be a cause of postoperative respiratory distress. The definitive diagnosis is made using PNS and observing the response to pharmacological reversal. Nebulized epinephrine may have a previously undescribed role in the development of postoperative reparalysis. 相似文献
8.
9.
10.
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