首页 | 官方网站   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   1191篇
  免费   38篇
  国内免费   6篇
工业技术   1235篇
  2023年   8篇
  2022年   32篇
  2021年   71篇
  2020年   15篇
  2019年   22篇
  2018年   24篇
  2017年   16篇
  2016年   47篇
  2015年   19篇
  2014年   47篇
  2013年   72篇
  2012年   54篇
  2011年   63篇
  2010年   39篇
  2009年   48篇
  2008年   44篇
  2007年   48篇
  2006年   33篇
  2005年   45篇
  2004年   36篇
  2003年   27篇
  2002年   32篇
  2001年   8篇
  2000年   22篇
  1999年   20篇
  1998年   67篇
  1997年   35篇
  1996年   17篇
  1995年   19篇
  1994年   22篇
  1993年   22篇
  1992年   12篇
  1991年   10篇
  1990年   10篇
  1989年   12篇
  1988年   16篇
  1987年   10篇
  1986年   10篇
  1985年   5篇
  1984年   7篇
  1983年   10篇
  1982年   6篇
  1981年   5篇
  1979年   8篇
  1978年   4篇
  1977年   7篇
  1976年   5篇
  1974年   3篇
  1973年   4篇
  1972年   5篇
排序方式: 共有1235条查询结果,搜索用时 31 毫秒
41.
The use of Ca(OH)2 pre-treatment to improve fermentative biohydrogen yields, from wheat straw was investigated. Wheat straw was pre-treated with 7.4% (w/w) Ca(OH)2 at ambient temperature (20 °C) for 2, 5, 8, and 12 days, prior to 35 °C fermentation with sewage sludge inoculum. Biohydrogen yields were evaluated during dark fermentation and simultaneous saccharification fermentation (SSF) of total pre-treated straw material and compared to those from separated solid and hydrolysate fractions. Ca(OH)2 pre-treatment followed by SSF, exhibited a synergetic relationship. On average, 58.78 mL-H2 g-VS−1 was produced from SSF of pre-treated and filtered solids. This was accompanied by approximately a 10-fold increase in volatile fatty acid production, compared to the untreated control. By omitting pre-treatment hydrolysate liquors from SSF, H2 production increased on average by 35.8%, per VS of harvested straw. Additional inhibition studies indicated that CaCO3, formed as a result of pre-treatment pH control, could promote homoacetogenesis and reduce biohydrogen yields.  相似文献   
42.
Abstract

Inventory management deals with a tradeoff between the benefits of keeping stocks of goods that allows fulfillment of the customer’s demand, and the cost of carrying inventory. Inventory control techniques are very important components and the most organizations can substantially reduce their costs associated with the flow of materials. This paper presents new inventory management model based on particle swarm optimization and pure adaptive search global optimization algorithm in production-inventory system. The proposed model is focusing on planned level of demand for finished goods, production and raw materials cost, production capacity as the norm, change of the production cost and inventory capital cost, all of which are typical factors in automobile manufacture industry. The model determines different factors such as the minimizing inventory quantity, minimizing inventory value, and minimizing production cost based on demand for production items. The model is tested with original real-world dataset obtained from the automotive company Lear from US and its factory in Novi Sad, Serbia.  相似文献   
43.
44.
Glyphosate determination in liver is challenging due to this particular molecule/matrix combination. Glyphosate is a very polar molecule and liver composition is highly variable between individuals and species. Since 2014, the Multiannual Control Program (MACP) of the European Union (EU) demands to analyse glyphosate in food of animal origin on a voluntary basis. Moreover, this analysis will be mandatory in 2017. This paper describes a robust and easily transferable method for glyphosate quantification in liver of animal origin by means of liquid chromatography–tandem mass spectrometry (LC-MS/MS). An intensive clean-up was used to eliminate matrix interferences and was combined with a derivatization step which ensures good retention of glyphosate on a conventional reverse-phase LC column. This method allows to meet the MACP requirements without a time-consuming change in the set-up of the routinely used LC-MS/MS system. Furthermore, it allows the use of an LC column and mobile phases often used in multi-residue analysis. The analytical method was validated according to the SANCO/12571/2013 criteria. Isotopic dilution was used to quantify glyphosate, leading to mean apparent recoveries of 115 and 101 % for the low (0.025 mg kg?1) and the high (0.250 mg kg?1) fortification levels, respectively. At both levels, the relative standard deviation was below 10 %. The limit of quantification of 0.025 mg kg?1 was found to be satisfactory as it was below the maximum residue level (MRL) value set at 0.050 mg kg?1 for glyphosate in liver. It is also the lowest MRL for all commodity types.  相似文献   
45.
46.
We investigate local and metric geometry of weighted Carnot–Carathéodory spaces which are a wide generalization of sub-Riemannian manifolds and arise in nonlinear control theory, subelliptic equations, etc. For such spaces, the intrinsic Carnot–Carathéodory metric might not exist, and some other new effects take place. We describe the local algebraic structure of such a space, endowed with a natural quasimetric (first introduced by A. Nagel, E. M. Stein, and S. Wainger) and compare local geometries of the initial Carnot–Carathéodory (CC) space and its tangent cone at some fixed (possibly nonregular) point. The main results of the present paper, in particular, the theorem on divergence of integral lines and other estimates obtained for the quasimetrics, are new even for the case of sub-Riemannian manifolds.  相似文献   
47.
48.
当前俄罗斯正在进行立法改革以实现治理体系现代化,其中改革的重点是国家管理体系中的劳动保护、工业安全和突发事件的应急处理。过去的立法体系侧重于对受伤员工提供健康补偿和医疗救护,而新的立法体系则以预防为主,以期通过建立完善的风险管理机制和运行规则,提高安全生产水平、普及安全文化教育,保障员工的生命安全。新标准强调企业必须进行职业风险评估,并将职业风险评估纳入企业工作管理体系。论文以采金业为例,选取伊尔库茨克州波戴波区金矿露天采场为研究案例,探讨了现代化职业风险评估的方法,明确了职业风险评估首先要进行危害鉴别,编制了风险源管理档案清单。采用实测员工风险因素的“记分法”和数学模拟“矩阵法”完成了伊尔库茨克州波戴波区金矿露天采场主要职业的风险评估。研究表明: 在钻井爆破作业场所,由碎石的喷射、粉尘的排放和噪声效应引起的危险为不可接受风险,通过实施安全生产制度(即遵守安全标准和技术要求、为工人提供防护装备),可将高风险和不可接受风险化解为可接受风险;阐述了高风险职业,编制了风险手册,提出了改善工作条件的首要措施是消除影响爆破手和钻机操作员的有害因素,并为员工提供能更有效预防噪音和振动的个人防护用品。  相似文献   
49.
Topics in Catalysis - The process of synthesis of formic acid via partial peroxide oxidation of methane over Fe-MFI zeolites, as well as the influence of the catalyst activation by oxalic acid on...  相似文献   
50.
The sea urchin Diadema setosum is edible and desirable as food by locals in central Vietnam and a promising target for potential fishing. The lipid profiles of the gonads of the sea urchin inhabiting the coastal area in Nha Trang Bay are studied for the first time. The determination of the content of the total lipids (TL), total phospholipids (PL), monoacylglycerols (MAG), diacylglycerols (DAG), triacylglycerols (TAG), cholesterol (Chol), sterol esters, and free fatty acids (FFA) is analyzed by high-performance thin layer chromatography (HPTLC); the phosphatidylserine (PS), phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidylcholine (PC), lysophosphatidylcholine (LPC), and sphingomyelin (SM) are determined by high-pressure liquid chromatography (HPLC); and the fatty acid levels of TLs are identified using gas chromatography (GC). Non-polar TAG, FFA, Chol, and DAG dominated. The content of total PL is significant. PC is abundant among PL fractions, followed by PE, PI, and PS. The TLs contain a high proportion of PUFA, mainly due to arachidonic fatty acid and eicosapentanoic fatty acid. The (n−6)/(n−3) ratio is 1.68, and the atherogenic and thrombogenic indexes of D. setosum are 1.13 and 0.73. The results can be used in the development of marine bioprospecting and methodological approaches for the creation of functional substances.  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-23

京公网安备 11010802026262号