全文获取类型
收费全文 | 3983篇 |
免费 | 237篇 |
国内免费 | 70篇 |
专业分类
电工技术 | 170篇 |
综合类 | 54篇 |
化学工业 | 837篇 |
金属工艺 | 110篇 |
机械仪表 | 152篇 |
建筑科学 | 94篇 |
矿业工程 | 19篇 |
能源动力 | 141篇 |
轻工业 | 208篇 |
水利工程 | 31篇 |
石油天然气 | 31篇 |
武器工业 | 8篇 |
无线电 | 814篇 |
一般工业技术 | 674篇 |
冶金工业 | 374篇 |
原子能技术 | 29篇 |
自动化技术 | 544篇 |
出版年
2024年 | 11篇 |
2023年 | 36篇 |
2022年 | 104篇 |
2021年 | 129篇 |
2020年 | 78篇 |
2019年 | 66篇 |
2018年 | 87篇 |
2017年 | 92篇 |
2016年 | 96篇 |
2015年 | 115篇 |
2014年 | 177篇 |
2013年 | 323篇 |
2012年 | 263篇 |
2011年 | 268篇 |
2010年 | 214篇 |
2009年 | 202篇 |
2008年 | 206篇 |
2007年 | 196篇 |
2006年 | 186篇 |
2005年 | 107篇 |
2004年 | 106篇 |
2003年 | 105篇 |
2002年 | 81篇 |
2001年 | 62篇 |
2000年 | 65篇 |
1999年 | 68篇 |
1998年 | 152篇 |
1997年 | 108篇 |
1996年 | 83篇 |
1995年 | 53篇 |
1994年 | 68篇 |
1993年 | 55篇 |
1992年 | 49篇 |
1991年 | 32篇 |
1990年 | 37篇 |
1989年 | 36篇 |
1988年 | 21篇 |
1987年 | 19篇 |
1986年 | 13篇 |
1985年 | 18篇 |
1984年 | 17篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 9篇 |
1980年 | 6篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 9篇 |
1975年 | 7篇 |
1973年 | 5篇 |
排序方式: 共有4290条查询结果,搜索用时 62 毫秒
181.
Mohamed Gamal Mohamed Maha Mohamed Samy Tharwat Hassan Mansoure Chia-Jung Li Wen-Cheng Li Jung-Hui Chen Kan Zhang Shiao-Wei Kuo 《International journal of molecular sciences》2022,23(1)
There is currently a pursuit of synthetic approaches for designing porous carbon materials with selective CO2 capture and/or excellent energy storage performance that significantly impacts the environment and the sustainable development of circular economy. In this study we prepared a new bio-based benzoxazine (AP-BZ) in high yield through Mannich condensation of apigenin, a naturally occurring phenol, with 4-bromoaniline and paraformaldehyde. We then prepared a PA-BZ porous organic polymer (POP) through Sonogashira coupling of AP-BZ with 1,3,6,8-tetraethynylpyrene (P-T) in the presence of Pd(PPh3)4. In situ Fourier transform infrared spectroscopy and differential scanning calorimetry revealed details of the thermal polymerization of the oxazine rings in the AP-BZ monomer and in the PA-BZ POP. Next, we prepared a microporous carbon/metal composite (PCMC) in three steps: Sonogashira coupling of AP-BZ with P-T in the presence of a zeolitic imidazolate framework (ZIF-67) as a directing hard template, affording a PA-BZ POP/ZIF-67 composite; etching in acetic acid; and pyrolysis of the resulting PA-BZ POP/metal composite at 500 °C. Powder X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, transmission electron microscopy, and Brunauer–Emmett–Teller (BET) measurements revealed the properties of the as-prepared PCMC. The PCMC material exhibited outstanding thermal stability (Td10 = 660 °C and char yield = 75 wt%), a high BET surface area (1110 m2 g–1), high CO2 adsorption (5.40 mmol g–1 at 273 K), excellent capacitance (735 F g–1), and a capacitance retention of up to 95% after 2000 galvanostatic charge–discharge (GCD) cycles; these characteristics were excellent when compared with those of the corresponding microporous carbon (MPC) prepared through pyrolysis of the PA-BZ POP precursors with a ZIF-67 template at 500 °C. 相似文献
182.
183.
184.
185.
针对矿山18线南西翼矿体开采过程中存在的通风系统不完善、风量欠缺、污风无法及时排出等问题,运用风压平衡原理、网络优化技术、机站优化技术以及计算机网络模拟技术展开研究,拟定了3种可行的通风方案。经技术经济比较,确定了新掘18线905~855 m回风井(1.5 m),保留该井905 m 水平回风机站,并在855 m 水平新设1台K45 6 №12风机(18.5 kW)方案。数值模拟结果表明:18线南西翼通风系统总风量达到20.5 m3/s,井下风流的可调性和稳定性增强,为矿山的安全生产提供了有力保障。 相似文献
186.
Li-Jane Shih Jia-Yu Wang Jing-Yao Jheng An-Ci Siao Yen-Yue Lin Yi-Wei Tsuei Yow-Chii Kuo Chih-Pin Chuu Yung-Hsi Kao 《International journal of molecular sciences》2020,21(23)
Prostate cancer (PCa) is a reproductive system cancer in elderly men. We investigated the effects of betel nut arecoline on the growth of normal and cancerous prostate cells. Normal RWPE-1 prostate epithelial cells, androgen-independent PC-3 PCa cells, and androgen-dependent LNCaP PCa cells were used. Arecoline inhibited their growth in dose- and time-dependent manners. Arecoline caused RWPE-1 and PC-3 cell cycle arrest in the G2/M phase and LNCaP cell arrest in the G0/G1 phase. In RWPE-1 cells, arecoline increased the expression of cyclin-dependent kinase (CDK)-1, p21, and cyclins B1 and D3, decreased the expression of CDK2, and had no effects on CDK4 and cyclin D1 expression. In PC-3 cells, arecoline decreased CDK1, CDK2, CDK4, p21, p27, and cyclin D1 and D3 protein expression and increased cyclin B1 protein expression. In LNCaP cells, arecoline decreased CDK2, CDK4, and cyclin D1 expression; increased p21, p27, and cyclin D3 expression; had no effects on CDK1 and cyclin B1 expression. The antioxidant N-acetylcysteine blocked the arecoline-induced increase in reactive oxygen species production, decreased cell viability, altered the cell cycle, and changed the cell cycle regulatory protein levels. Thus, arecoline oxidant exerts differential effects on the cell cycle through modulations of regulatory proteins. 相似文献
187.
地表蒸散发(ET)是水循环和能量循环的关键组成部分,具有极其重要的应用价值。研究旨在发展一种可靠且高效的深度神经网络(DNN)模型,基于MODIS可见光数据、微波AMSR2亮度温度和数字高程DEM,实现全天候全球高分辨率每日ET的估算。利用FLUXNET和AmeriFlux通量网6种代表性土地覆盖类型的148个站点观测数据来训练和验证DNN模型,结果表明:DNN模型可以有效建立卫星数据(MODIS、AMSR2数据)与ET之间的关系;6种地类的ET估算结果验证的平均绝对误差(MAE)为0.16—0.63 mm/d,均方根误差(RMSE)为0.27—0.89 mm/d,除裸地的决定系数(R2)为0.37以外,其他地类的R2均>0.7。通过对比模型估算的ET与MOD16A2和GLEAM的ET产品,结果表明3种产品的ET空间分布特征相似,ET值非常接近,估算得到的全球2020年日均ET为0—4 mm/d。 相似文献
188.
Richard Kuan-Lin Lee Tian-Neng Li Sui-Yuan Chang Tai-Ling Chao Chun-Hsien Kuo Max Yu-Chen Pan Yu-Ting Chiou Kuan-Ju Liao Yi Yang Yi-Hsuan Wu Chen-Hao Huang Hsueh-Fen Juan Hsing-Pang Hsieh Lily Hui-Ching Wang 《International journal of molecular sciences》2022,23(7)
Entry inhibitors against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are urgently needed to control the outbreak of coronavirus disease 2019 (COVID-19). This study developed a robust and straightforward assay that detected the molecular interaction between the receptor-binding domain (RBD) of viral spike protein and the angiotensin-converting enzyme 2 (ACE2) receptor in just 10 min. A drug library of 1068 approved compounds was used to screen for SARS-CoV2 entry inhibition, and 9 active drugs were identified as specific pseudovirus entry inhibitors. A plaque reduction neutralization test using authentic SARS-CoV-2 virus in Vero E6 cells confirmed that 2 of these drugs (Etravirine and Dolutegravir) significantly inhibited the infection of SARS-CoV-2. With molecular docking, we showed that both Etravirine and Dolutegravir are preferentially bound to primary ACE2-interacting residues on the RBD domain, implying that these two drug blocks may prohibit the viral attachment of SARS-CoV-2. We compared the neutralizing activities of these entry inhibitors against different pseudoviruses carrying spike proteins from alpha, beta, gamma, and delta variants. Both Etravirine and Dolutegravir showed similar neutralizing activities against different variants, with EC50 values between 4.5 to 5.8 nM for Etravirine and 10.2 to 22.9 nM for Dolutegravir. These data implied that Etravirine and Dolutegravir may serve as general spike inhibitors against dominant viral variants of SARS-CoV-2. 相似文献
189.
190.