全文获取类型
收费全文 | 966篇 |
免费 | 130篇 |
国内免费 | 54篇 |
专业分类
电工技术 | 21篇 |
综合类 | 69篇 |
化学工业 | 56篇 |
金属工艺 | 10篇 |
机械仪表 | 4篇 |
建筑科学 | 273篇 |
矿业工程 | 39篇 |
能源动力 | 72篇 |
轻工业 | 56篇 |
水利工程 | 67篇 |
石油天然气 | 304篇 |
武器工业 | 1篇 |
无线电 | 26篇 |
一般工业技术 | 59篇 |
冶金工业 | 48篇 |
原子能技术 | 5篇 |
自动化技术 | 40篇 |
出版年
2024年 | 9篇 |
2023年 | 16篇 |
2022年 | 27篇 |
2021年 | 22篇 |
2020年 | 41篇 |
2019年 | 46篇 |
2018年 | 27篇 |
2017年 | 32篇 |
2016年 | 38篇 |
2015年 | 46篇 |
2014年 | 68篇 |
2013年 | 91篇 |
2012年 | 55篇 |
2011年 | 69篇 |
2010年 | 71篇 |
2009年 | 59篇 |
2008年 | 57篇 |
2007年 | 63篇 |
2006年 | 56篇 |
2005年 | 39篇 |
2004年 | 35篇 |
2003年 | 36篇 |
2002年 | 20篇 |
2001年 | 30篇 |
2000年 | 14篇 |
1999年 | 14篇 |
1998年 | 4篇 |
1997年 | 12篇 |
1996年 | 9篇 |
1995年 | 2篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 1篇 |
1974年 | 1篇 |
1970年 | 1篇 |
1964年 | 1篇 |
1963年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有1150条查询结果,搜索用时 15 毫秒
91.
James Mark Baldwin was one of the earliest American practitioners of the "new psychology" and an influential figure in the emergence and establishment of psychology in the US. He left the US because of a scandal in Baltimore resulting from his arrest at a "colored" bordello. Baldwin returned only occasionally to North America following his forced resignation from Johns Hopkins University in 1909. Contrary to the few references to his life after leaving Baltimore, Baldwin appears to have initially settled in England. He made numerous extended trips to Mexico and continental Europe, especially France, which eventually became his adopted home. Baldwin's later life and work in Europe are examined in this article. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
92.
为了查清储层发育规律,提高勘探成功率,运用岩心观察、铸体薄片鉴定、阴极发光等手段,结合测井、孔渗等资料,研究了塔中顺南地区奥陶系一间房组碳酸盐岩的储层特征、成岩作用及其对储层发育的影响。结果表明:研究区奥陶系一间房组碳酸盐岩储层的岩石类型主要为颗粒灰岩、微晶灰岩、藻黏结灰岩;储集空间类型以溶蚀孔洞和裂缝为主,为裂缝型和裂缝-孔洞型储层;一间房组储层基质孔隙度最小值为 0.20%,最大值为 3.90%,平均值为 1.52%;渗透率最小值为 0.003 mD,最大值为 5.84 mD,平均值为 0.62 mD,储层基质物性较差,以发育 Ⅲ 类储层为主;一间房组碳酸盐岩的成岩作用类型复杂多样,主要有胶结作用、压实压溶作用、溶蚀(岩溶)作用、破裂作用等,其中胶结作用是最主要的破坏性成岩作用,溶蚀(岩溶)作用和破裂作用均是主要的建设性成岩作用。 相似文献
93.
Luca Grilli 《Industry and innovation》2014,21(4):267-284
Increasing the number of rapid-growth new technology-based firms (NTBFs) is considered one of the key priorities of innovation policy adopted by the European Commission. Grounded in the empirical literature on the determinants of high-tech start-up growth in Europe, this paper develops a heuristic firm growth model for European NTBFs to individuate three primary areas of intervention for policy-making aimed to sustain the growth of NTBFs: (i) reducing the social and regulatory burdens arising from (honest) firm failure, (ii) acknowledging the local nature of the venture capital industry and promoting territorial marketing initiatives to attract (international) venture capitalist players and (iii) leveraging the “halo and certification” effect of directs public subsidies and grants towards NTBFs. If recent initiatives of the European Commission go in these directions, much remains to be done to increase the growth potential of high-tech start-ups on the European landscape. 相似文献
94.
Claude Debru 《Centaurus; international magazine of the history of science and medicine》2013,55(1):62-69
This paper is devoted to an outline of certain aspects of international scientific cooperation and exchange between Eastern and Western European countries from 1950 to 1989, with an emphasis on mathematics, biochemistry and neuroscience. 相似文献
95.
设计语义是研究设计语言的意义的学问.研究中世纪书籍装帧中的设计语义,有助于了解这种形成于被认为是黑暗的、毫无人性化的时代中形成的书籍装帧形式为什么可以在印刷时代被继续沿用,并从中获得启发. 相似文献
96.
国外钻井技术发展现状 总被引:7,自引:0,他引:7
美国及西欧一些发达国家一直处于钻井技术的前列,了解国外钻井技术现状,利于我国们在战略上决策钻井科技发展的方向,本文首先概述了国外比较成熟的大位移井钻井、欠平衡钻井、小井眼钻井、超深井钻井、老井重钻等技术,对国外正在研究和开发的钻井技术,如分枝井钻井技术、连续管技术、旋转导向钻井系统、套管钻井工艺、三维可视化技术等也作了一定介绍,对促进我国钻井技术的发展具有一定的借鉴意义。 相似文献
97.
The structure of CFC use in Western Europe is different from that in the USA and Japan, with the highest percentage use of CFCs in Europe in aerosols. The use of CFCs in automotive air conditioning in the EEC is much less than elsewhere and this, together with the fact that R-12 and R-22 already have similar market shares, means that the refrigeration industry in Western Europe will not be as greatly affected by CFC reduction as elsewhere. More stringent reduction programmes than those imposed by the Montreal Protocol are in force in most Western European countries, to some extent due to consumer and environmental pressure group influences. Some countries, especially in Scandinavia, are introducing additional legislation to restrict CFC use. The strongest stand has been taken by the Federal Republic of Germany, which requires a 95% reduction in CFC use by 1995, with a voluntary ban from 1992. This paper discusses in detail European research programmes into CFC replacements. Many projects have been proposed, including work on refrigerants [fundamentals (four projects), thermophysical properties (18 projects) and lubricants and materials (five projects)] and cycles and components (17 projects). 相似文献
98.
Derk J. Swider Luuk Beurskens Sarah Davidson John Twidell Jurek Pyrko Wolfgang Prüggler Hans Auer Katarina Vertin Romualdas Skema 《Renewable Energy》2008,33(8):1832-1842
This paper compares conditions and costs for RES-E grid connection in selected European countries. These are Germany, the Netherlands, the United Kingdom, Sweden, Austria, Lithuania and Slovenia. Country specific case studies are presented for wind onshore and offshore, biomass and photovoltaic power systems, as based on literature reviews and stakeholder interviews. It is shown that, especially for wind offshore, the allocation of grid connection costs can form a significant barrier for the installation of new RES-E generation if the developer has to bear all such costs. If energy policy makers want to reduce the barriers for new large-scale RES-E deployment, then it is concluded that the grid connection costs should be covered by the respective grid operator. These costs may then be recouped by increasing consumer tariffs for the use of the grid. 相似文献
99.
Soil nutrient deficiency has hampered increased agricultural production in the savannas of northern Nigeria. It has been observed that inorganic fertilizer (IF) has the potential to reverse the situation. However, low adoption among the farmers has characterized IF in the savannas of northern Nigeria. The application rates have also fallen far lower than the rate recommended by research and extension, resulting in low crop yields. This paper investigates the factors that influence farmers' decision to adopt or not to adopt IF and to evaluate the elasticity of adoption. This information will help to prioritize the factors that affect IF adoption decisions and suggest pathways for effective promotion of IF. About 49% of the survey farmers adopted IF and the application rate ranges from 5.6 to 64.4 kg ha–1 (with a mean of 24.1 kg ha–1). The probability of adoption increases with increased targeting of: farmers from the Guinea savanna agroecological zone, younger farmers, better educated farmers, food secure farmers and net sellers of food grains, farmers who have diversified into many crops, farmers who perceive increase in the fertilizer needs of their crops, and farmers who apply large quantities of organic manure. Among others, the estimates of elasticity of adoption indicate that a 1% increase in the number of farmers who perceive an increase in the fertilizer needs of their crops results in 3.23% increase in the probability of IF adoption. The paper concludes with policy implications for strategies aimed at promoting IF in the savannas of Nigeria and similar ecologies elsewhere. 相似文献
100.
柴达木盆地北缘侏罗系烃源岩生物有机相 总被引:3,自引:0,他引:3
柴达木盆地北缘地区侏罗系烃源岩的主要生烃显微组分包括藻类体、角质体和孢子体,根据这3种不同显微组分在岩石中的赋存特征、丰度,以及它们之间的相对含量,将侏罗系泥岩的成烃生物相分为4类:富集有机质型(A型)、有机质密集搬运-沉积聚集型(B型)、有机质稀疏搬运-沉积聚集型(C型)、有机质碎屑状散布型(D型).从A型到D型,有机质丰度逐渐降低,类型逐渐变差.对油气勘探和地质研究具有重要意义的优质烃源岩是A型生物相泥岩,该类烃源岩发育较高丰度的层状藻类体,有机碳含量大干4.O%,有机质类型为Ⅱ1-Ⅱ2型,一般只在下侏罗统下部和中侏罗统七段的局部层段发育,往往集中在几米至十几米厚的富集有机质层段,多形成于湖泊-三角洲沉积体系中的闭塞环境.图5表3参20 相似文献