全文获取类型
收费全文 | 2400篇 |
免费 | 185篇 |
国内免费 | 38篇 |
专业分类
电工技术 | 9篇 |
综合类 | 123篇 |
化学工业 | 1078篇 |
金属工艺 | 37篇 |
机械仪表 | 35篇 |
建筑科学 | 290篇 |
矿业工程 | 16篇 |
能源动力 | 15篇 |
轻工业 | 662篇 |
水利工程 | 38篇 |
石油天然气 | 44篇 |
武器工业 | 3篇 |
无线电 | 20篇 |
一般工业技术 | 172篇 |
冶金工业 | 32篇 |
原子能技术 | 14篇 |
自动化技术 | 35篇 |
出版年
2024年 | 11篇 |
2023年 | 49篇 |
2022年 | 142篇 |
2021年 | 140篇 |
2020年 | 87篇 |
2019年 | 69篇 |
2018年 | 69篇 |
2017年 | 54篇 |
2016年 | 87篇 |
2015年 | 75篇 |
2014年 | 109篇 |
2013年 | 166篇 |
2012年 | 145篇 |
2011年 | 123篇 |
2010年 | 103篇 |
2009年 | 113篇 |
2008年 | 72篇 |
2007年 | 123篇 |
2006年 | 105篇 |
2005年 | 110篇 |
2004年 | 70篇 |
2003年 | 57篇 |
2002年 | 46篇 |
2001年 | 27篇 |
2000年 | 50篇 |
1999年 | 37篇 |
1998年 | 37篇 |
1997年 | 20篇 |
1996年 | 29篇 |
1995年 | 29篇 |
1994年 | 19篇 |
1993年 | 19篇 |
1992年 | 22篇 |
1991年 | 24篇 |
1990年 | 20篇 |
1989年 | 19篇 |
1988年 | 9篇 |
1987年 | 24篇 |
1986年 | 10篇 |
1985年 | 26篇 |
1984年 | 26篇 |
1983年 | 11篇 |
1982年 | 12篇 |
1981年 | 8篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1977年 | 5篇 |
1976年 | 2篇 |
1951年 | 1篇 |
排序方式: 共有2623条查询结果,搜索用时 15 毫秒
1.
Yue Gao Miao-miao Zhang Xiao-peng Guo Wen-jian Li Dong Lu 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2020,95(5):1290-1297
Toxicity caused by the accumulation of butanol in fermentation media is an important factor limiting the concentration of butanol. There is currently no systematic research in place investigating the butanol tolerance mechanism of bacteria such as Clostridium acetobutylicum, which adapts to butanol stress and regulates its growth and metabolism. Here, research results related to the butanol tolerance of C. acetobutylicum are reviewed to understand the molecular basis of changes in butanol-tolerant strains. Organic solvent-tolerant bacteria play an important role in the fields of biofuel production, enzyme preparation and bioremediation. An analysis of limitations of the application of organic solvent-tolerant bacteria has revealed that future research should focus on combining the microbial tolerance phenotype with specific utilization to achieve an optimal balance between organic solvent tolerance and production. This review serves as a reference for the improvement and engineering of strains that tolerate organic solvents. © 2019 Society of Chemical Industry 相似文献
2.
3.
Sung-Eun Lee 《Journal of Stored Products Research》2002,38(2):157-166
The fumigant toxicities of lavender and ylang-ylang essential oils were tested against a chlorpyrifos-methyl resistant strain (QVOS102) and an insecticide-susceptible reference strain (VOS48) of the saw-toothed grain beetle, Oryzaephilus surinamensis L. (Coleoptera: Silvanidae). The resistant strain showed 1.3- and 1.6-fold higher tolerance against lavender and ylang-ylang fumigation toxicity, respectively, relative to the susceptible strain. LT50 values calculated as the time to attain 50% mortality of tested insects during fumigation were determined at two different concentrations. At 15 μl/l of air, QVOS102 had 2.9- and 1.4-fold higher LT50 values for lavender and ylang-ylang fumigation toxicity, respectively, than VOS48. At 200 μl/l air, QVOS102 had 6.4- and 2.9-fold higher LT50 values for lavender and ylang-ylang fumigation toxicity, respectively, than VOS48. Piperonyl butoxide, a potential inhibitor of cytochrome P450-dependent monooxygenase, increased fumigant toxicities of the two essential oils against QVOS102. The enhanced tolerance for the essential oil may have resulted from the enhancement of detoxifying enzymes associated with insecticide resistance. 相似文献
4.
5.
6.
聚α烯烃基础油的生物降解性和毒性 总被引:4,自引:0,他引:4
低粘度聚α烯烃(PAO)基础油,在CEC-L-33-T-82试验程序的条件下是容易生物降解的。PAO基础油对哺乳动物是无毒和无刺激性的,在海洋微生物荧光细菌的Microtox试验中,对含有49000μg/g浓度的PAO水溶性馏分,没有发现明显的影响。 相似文献
7.
目的制备新生牛肝活性肽并评价其安全性。方法采用膜法分离制备新生牛肝活性肽。将3批制品于37~40℃,75%相对湿度条件下存放3个月,以多肽含量为指标观察其稳定性,并进行急性毒性试验、小鼠骨髓细胞微核试验、Ames试验、小鼠精子畸形试验和大鼠喂养试验。结果制备的3批新生牛肝活性肽存放3个月后,多肽含量无明显下降,质量稳定。小鼠和大鼠经口灌人大于20.0g/kg体重的新生牛肝活性肽,均无急性毒性。3种致突变试验均未显示出致突变性,大鼠喂养试验各项指标均未见明显毒性。结论新生牛肝活性肽未表现出明显毒性。 相似文献
8.
聚乙二醇修饰的蓖麻毒蛋白A链的免疫原性和在小鼠体内急性毒性研究 总被引:2,自引:0,他引:2
目的研究单甲氧聚乙二醇(mPEG)与蓖麻毒蛋白A链(RA)偶联后RA免疫原性和毒性的改变。方法从天然蓖麻籽中提取纯化的RA,经与含活性马来酰亚胺基团的mPEG反应偶联,得到纯化的mPEG偶联RA。用蛋白质印迹方法比较RA修饰前后的免疫原性,通过测定半数致死量(LD50)比较RA修饰前后的毒性。结果mPEG偶联RA后免疫原性和毒性均明显下降。偶联前RA链的LD50为2.37 mg.kg-1,经mPEG修饰后RA的LD50为6.15mg.kg-1。结论聚乙二醇能遮蔽RA,降低其免疫原性和毒性。 相似文献
9.
The soil microbial biomass quotient (expressed as a percentage of the total soil organic carbon) and the specific rate of carbon-dioxide production by soil microbes (respiration quotient) are often used as indicators of stress on soil microbial populations. A low biomass quotient or a high respiration quotient is considered to be an indication of stress from, for example, toxicity from metals in sewage sludge applied to soils. These metabolic quotients are affected by a wide variety of other factors such as the biodegradability of soil organic-carbon amendments, plant inputs of organic carbon into soils, natural variations in microbial population sizes with depth, and in the rhizosphere of plants. These variations could be sufficiently large to make interpretation of changes in biomass quotient and respiration quotient, as a response to stress, problematical. 相似文献
10.
Four sites in the Detroit River/Lake Erie western basin were evaluated for their toxicity. The evaluation was based on 1) bulk chemical characterization of the sediments, 2) chemical composition of the sediment elutriates, and 3) toxicity of the elutriates to ultraplankton and microplankton/net plankton. A sequence of decreasing contamination was determined from the chemical composition of the elutriates based on the elutriation release of metals such as Zn, Mn, Cd, Ni, and Co. Bioassessment of elutriate toxicity was determined by carbon-14 Algal Fractionation Bioassays (AFB's) which were conducted with various dilutions of standard and Chelex-100 treated elutriates. Site A (near Windsor, Ontario) and Site D (western Lake Erie) were found to be toxic to ultraplankton. The observed toxicity was attributed to the bioavailability and synergistic impact of elutriated metals on ultraplankton production. A direct relationship between the water soluble metal fraction and toxicity was observed. These results confirmed that sediment toxicity should not be evaluated solely on bulk chemical composition of the sediments. The AFB's have been proven useful in the bioassessment of sediments due to their rapidity/sensitivity and hence could be routinely used for the screening and early detection of contaminants affecting fast growing organisms which form the basis of the aquatic food chain. 相似文献