首页 | 本学科首页   官方微博 | 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   2243篇
  免费   103篇
  国内免费   1篇
电工技术   22篇
综合类   21篇
化学工业   592篇
金属工艺   35篇
机械仪表   37篇
建筑科学   155篇
矿业工程   9篇
能源动力   53篇
轻工业   181篇
水利工程   19篇
石油天然气   2篇
无线电   151篇
一般工业技术   422篇
冶金工业   259篇
原子能技术   13篇
自动化技术   376篇
  2023年   18篇
  2022年   25篇
  2021年   46篇
  2020年   48篇
  2019年   41篇
  2018年   58篇
  2017年   25篇
  2016年   56篇
  2015年   43篇
  2014年   95篇
  2013年   118篇
  2012年   111篇
  2011年   176篇
  2010年   110篇
  2009年   97篇
  2008年   106篇
  2007年   103篇
  2006年   84篇
  2005年   52篇
  2004年   68篇
  2003年   49篇
  2002年   62篇
  2001年   40篇
  2000年   36篇
  1999年   49篇
  1998年   97篇
  1997年   66篇
  1996年   52篇
  1995年   33篇
  1994年   32篇
  1993年   23篇
  1992年   22篇
  1991年   25篇
  1990年   23篇
  1989年   18篇
  1988年   17篇
  1987年   9篇
  1986年   9篇
  1985年   8篇
  1984年   18篇
  1983年   11篇
  1982年   13篇
  1981年   10篇
  1980年   14篇
  1979年   10篇
  1978年   14篇
  1977年   11篇
  1976年   16篇
  1975年   13篇
  1970年   8篇
排序方式: 共有2347条查询结果,搜索用时 203 毫秒
1.
2.
Financial theory creates a puzzle. Some authors argue that high-risk entrepreneurs choose debt contracts instead of equity contracts since risky but high returns are of relatively more value for a loan-financed firm. Conversely, authors who focus explicitly on start-up finance predict that entrepreneurs are the more likely to seek equity-like venture capital contracts, the more risky their projects are. Our paper is an initial step towards resolving this puzzle empirically. We present microeconometric evidence on the determinants of debt and equity financing in young and innovative SMEs. We pay special attention to the role of risk for the choice of the method of financing. Since risk is not directly observable we use different indicators for financial and project risk. It turns out that our data generally confirms the hypothesis that the probability that a young high-tech firm receives equity financing is an increasing function of the financial risk. With regard to the intrinsic project risk, our results are less conclusive, as some of our indicators of a risky project are found to have a negative effect on the likelihood to be financed by private equity.  相似文献   
3.
Approximately 80% of the international transport of goods is carried on by means of ships. A large portion of the transport capacity is represented by Roll-on-Roll-off (RoRo) ships. Especially in Europe this is a relevant potential for the RoRo segment. Consequently, the design and construction of RoRo ships plays an increasing role for German shipyards and their suppliers. In order to make the loading and unloading procedure of trailer economically more competitive, ship owners would like to improve the lashing of trailers on the ship. On the basis of a multibody system formalism, a software tool has been developed which allows for an optimization of the loading of trailers on RoRo ships. Commemorative Contribution.  相似文献   
4.
Dynamic complexity investigates the required effort to maintain knowledge about a property of a structure under changing operations. This article introduces a refined notion of dynamic problems which takes the initial structure into account. It develops the basic structural complexity notions accordingly. It also shows that the dynamic version of the LOGCFL-complete problem D2LREACH(acyclic) can be maintained with first-order updates.  相似文献   
5.
We present a method based on extended linear real quantifier elimination for multiple object semilinear motion planning, i.e. finding collision-free trajectories for several robots in a time dependent environment. For practical applicability the method is limited to polygonal objects and linear trajectories. It can, however, deal with situations involving even non-convex objects.  相似文献   
6.
7.
Das Autobahnmautgesetz zeichnet sich durch eine strenge Zweckbindung für die Mautdaten aus. Diese dürfen ausschlie?lich für die Zwecke des Mautgesetzes erhoben und verarbeitet werden. Diese Vorgabe hat das LG Magdeburg in einem Beschluss richtungsweisend auch für die Verbindungsdaten der GSM-Kommunikation best?tigt.  相似文献   
8.
We prove several essential fractal properties, such as positivity, finiteness or local infinity, of Hausdorff and packing measures of radial Julia sets for large subclasses of entire and meromorphic functions considered in our previous work: çGeometric thermodynamical formalism and real analyticity for meromorphic functions of finite order'. Most of the results proven are shown to be optimal.  相似文献   
9.
Symbolic parametrization of curves   总被引:1,自引:0,他引:1  
If algebraic varieties like curves or surfaces are to be manipulated by computers, it is essential to be able to represent these geometric objects in an appropriate way. For some applications an implicit representation by algebraic equations is desirable, whereas for others an explicit or parametric representation is more suitable. Therefore, transformation algorithms from one representation to the other are of utmost importance.We investigate the transformation of an implicit representation of a plane algebraic curve into a parametric representation. Various methods for computing a rational parametrization, if one exists, are described. As a new idea we introduce the concept of working with classes of conjugate (singular or simple) points on curves. All the necessary operations, like determining the multiplicity and the character of the singular points or passing a linear system of curves through these points, can be applied to such classes of conjugate points. Using this idea one can parametrize a curve if one knows only one simple point on it. We do not propose any new method for finding such a simple point. By classical methods a rational point on a rational curve can be computed, if such a point exists. Otherwise, one can express the coordinates of such a point in an algebraic extension of degree 2 over the ground field.  相似文献   
10.
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