全文获取类型
收费全文 | 39289篇 |
免费 | 4004篇 |
国内免费 | 2251篇 |
专业分类
电工技术 | 2263篇 |
技术理论 | 1篇 |
综合类 | 2964篇 |
化学工业 | 6279篇 |
金属工艺 | 2242篇 |
机械仪表 | 2394篇 |
建筑科学 | 3127篇 |
矿业工程 | 1085篇 |
能源动力 | 1123篇 |
轻工业 | 3178篇 |
水利工程 | 891篇 |
石油天然气 | 1960篇 |
武器工业 | 340篇 |
无线电 | 4872篇 |
一般工业技术 | 4815篇 |
冶金工业 | 1676篇 |
原子能技术 | 501篇 |
自动化技术 | 5833篇 |
出版年
2024年 | 209篇 |
2023年 | 680篇 |
2022年 | 1183篇 |
2021年 | 1643篇 |
2020年 | 1322篇 |
2019年 | 1059篇 |
2018年 | 1278篇 |
2017年 | 1372篇 |
2016年 | 1304篇 |
2015年 | 1583篇 |
2014年 | 1984篇 |
2013年 | 2481篇 |
2012年 | 2732篇 |
2011年 | 2794篇 |
2010年 | 2578篇 |
2009年 | 2538篇 |
2008年 | 2468篇 |
2007年 | 2374篇 |
2006年 | 2239篇 |
2005年 | 1864篇 |
2004年 | 1422篇 |
2003年 | 1326篇 |
2002年 | 1397篇 |
2001年 | 1209篇 |
2000年 | 844篇 |
1999年 | 722篇 |
1998年 | 532篇 |
1997年 | 488篇 |
1996年 | 413篇 |
1995年 | 327篇 |
1994年 | 269篇 |
1993年 | 197篇 |
1992年 | 177篇 |
1991年 | 116篇 |
1990年 | 109篇 |
1989年 | 72篇 |
1988年 | 52篇 |
1987年 | 44篇 |
1986年 | 29篇 |
1985年 | 15篇 |
1984年 | 17篇 |
1983年 | 18篇 |
1982年 | 11篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1977年 | 3篇 |
1973年 | 3篇 |
1959年 | 8篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Shinsook Yoon Mi-Kyoung Kim In-Young Lee Mikyung Yun Jeong E. Nam Shin 《Journal of Industrial and Engineering Chemistry》2008,14(6):759-764
We have developed a mutant strain derived from Agrobacterium sp. ATCC 31750, which produces a water-soluble polysaccharide having potential utility to the food, feed, pharmaceutical and cosmetic industries. A high concentration of product (15 g/L) is obtained by 48 h cultivation of the mutant strain under optimized fermentation conditions. The water-soluble polysaccharide obtained from cultures of the mutant strain beta82 has Glc:Man:Gal in approximate molar ratios of 5.8:6.7:1.0. The molecular weight of the polysaccharide was determined to be approximately 1000 kDa by HPSEC analysis. Linkage analysis contained 3-Glcp, 3-Manp, terminal Glcp and terminal Manp, as well as a small proportion of 3- and 3,4-Galp, and 4,6-Manp residues. Based on analyses using FT-IR and 13C NMR spectrometers, most glycosidic bonds joining these sugar residues are of the α-type, and acetyl groups are apparently attached to the polymer chain at random. 相似文献
42.
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
43.
Yun‐Seok Cho Bheong‐Uk Lee Kye‐Heon Oh 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(9):1211-1217
BACKGROUND: Environmental contamination by nitroaromatic compounds such as 2,4,6‐trinitrotoluene (TNT), hexahydro‐1,3,5‐trinitro‐1,3,5‐s‐triazine (RDX), atrazine, and/or simazine (TRAS) generated as waste from military and agricultural activities is a serious worldwide problem. Microbiological treatment of these compounds is an attractive method because many explosives and herbicides are biodegradable and the process can be made cost‐effective. We explored the feasibility of using cultures of Pseudomonas putida HK‐6 for simultaneous degradation of TRAS with the aim of microbial application in wastewater treatment in bench‐scale bioreactors. RESULTS: Experiments were conducted to study the effects of supplemental carbons, nitrogens, and Tween‐80 on the degradation of Ps. putida HK‐6 in media containing TRAS as target substrate(s). The most effective TRAS degradation was shown in the presence of molasses. Addition of nitrogen sources produced a delayed effect for the target substrate(s). Tween‐80 enhanced the degradation of target substrate(s). Simultaneous degradation of these compounds proceeded to completion within the given period. CONCLUSIONS: Ps. putida HK‐6 was capable of growth with TRAS, and the effects of supplements on TRAS degradation and simultaneous TRAS degradation were evaluated in bench‐scale bioreactors. The results of this study have practical applications in the processes of industrial waste stream treatment where the disposal of TRAS may be problematic. Copyright © 2008 Society of Chemical Industry 相似文献
44.
Wei Li Zhang Wei Pan Bin Luo Xi Hua Zou Meng Yao Wang 《Photonics Technology Letters, IEEE》2008,20(9):712-714
A theoretical construction of one-to-many (OTM) and many-to-one (MTO) chaos synchronization communications using semiconductor lasers is presented. One center laser provides strong injections (strong link) to other side lasers, and the side lasers also provide weak injections (weak link) to the center one. Simulation results show that the side lasers synchronize with the center laser through injection-locking. In addition, messages transmitted via the strong links or the weak links experience strong chaos pass filtering, enabling us to realize OTM and MTO communications. 相似文献
45.
Yun‐Hwei Shen 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(5):581-586
A novel strategy of sweep coagulation to treat low turbidity water is presented herein. Study findings demonstrated that an Na+‐saturated bentonite with medium cation exchange capacity (CEC) resulted in significant turbidity removal at a bentonite dosage of 30 mg dm?3. Bentonite dispersion with fully delaminated platelets tended to undergo a more porous type of coagulation with intense face‐to‐face interactions of platelets and effectively entrapped TiO2 particles in band‐type structures. This type of coagulation usually results in a large volume of settled flocs with a fluffy structure and excellent turbidity removal efficiency for sweep coagulation. The sign and magnitude of electrical charge on TiO2 particles has a minor effect on the efficiency of sweep coagulation. Copyright © 2005 Society of Chemical Industry 相似文献
46.
47.
48.
Feedback-induced chaos and intensity noise enhancement in a laser diode with external optical feedback are studied by computer simulations. The enhancement of relative intensity noise (RIN) that is often observed in experiments is considered as a result of the feedback-induced deterministic chaos and the intensity noise suppression is treated from the viewpoint of chaos control. Especially, the conventional noise suppressing technique known as a high-frequency injection modulation is turned into a problem of stabilizing chaos through parameter modulations. We developed an analytical method which allows to optimize the modulation frequency from the linear stability analysis of the dynamical model that describes the laser diode with external feedback. The robustness of the modulation with respect to the modulation frequency and depth is verified and the results suggest the feasibility of applying our method to actual noise suppression. The RIN in the low-frequency region (up to 100 MHz) is shown to be reduced to the solitary laser level when the feedback-induced chaos is effectively controlled with the optimized modulation frequency 相似文献
49.
50.