全文获取类型
收费全文 | 2966篇 |
免费 | 270篇 |
国内免费 | 75篇 |
专业分类
电工技术 | 153篇 |
综合类 | 164篇 |
化学工业 | 350篇 |
金属工艺 | 52篇 |
机械仪表 | 109篇 |
建筑科学 | 239篇 |
矿业工程 | 16篇 |
能源动力 | 60篇 |
轻工业 | 99篇 |
水利工程 | 69篇 |
石油天然气 | 37篇 |
武器工业 | 8篇 |
无线电 | 383篇 |
一般工业技术 | 254篇 |
冶金工业 | 54篇 |
原子能技术 | 80篇 |
自动化技术 | 1184篇 |
出版年
2023年 | 9篇 |
2022年 | 23篇 |
2021年 | 37篇 |
2020年 | 61篇 |
2019年 | 62篇 |
2018年 | 71篇 |
2017年 | 60篇 |
2016年 | 86篇 |
2015年 | 114篇 |
2014年 | 116篇 |
2013年 | 125篇 |
2012年 | 131篇 |
2011年 | 222篇 |
2010年 | 142篇 |
2009年 | 188篇 |
2008年 | 198篇 |
2007年 | 194篇 |
2006年 | 136篇 |
2005年 | 148篇 |
2004年 | 163篇 |
2003年 | 224篇 |
2002年 | 149篇 |
2001年 | 139篇 |
2000年 | 79篇 |
1999年 | 50篇 |
1998年 | 33篇 |
1997年 | 33篇 |
1996年 | 47篇 |
1995年 | 33篇 |
1994年 | 40篇 |
1993年 | 17篇 |
1992年 | 21篇 |
1991年 | 24篇 |
1990年 | 16篇 |
1989年 | 8篇 |
1988年 | 12篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 18篇 |
1984年 | 17篇 |
1983年 | 9篇 |
1982年 | 8篇 |
1981年 | 5篇 |
1979年 | 2篇 |
1978年 | 8篇 |
1977年 | 3篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 4篇 |
1965年 | 1篇 |
排序方式: 共有3311条查询结果,搜索用时 15 毫秒
971.
Karl Sommer 《化学,工程师,技术》2000,72(8):809-812
While the quality and variety of particle size measuring instruments have improved dramatically in recent years, both in their accuracy and in their speed of measurement, the representation of the measured data — particularly the density distribution — has generally received little attention from the manufacturers. The depiction of a continuous density distribution by a percentage value on the ordinate makes no sense. Although logarithmic density distributions serve a purpose with distinctly separated bi‐ or multimodal distributions (by analogy with analytical chemical spectra), they can lead to serious interpretation errors in the case of the monomodal distribution. Thus for monomodal distributions either the density distribution qr(x) should be used or no representation of the density distribution attempted. 相似文献
972.
斜齿圆桂齿轮在Pro/e中的三维建模 总被引:3,自引:3,他引:0
阐述了利用Pro/e软件的建模功能,生成渐开线斜齿圆柱齿轮,包括在Pro/e中渐开线方程式的建立及用扫描方式建立齿轮轮齿的过程,最后生成完整的斜齿圆柱齿轮三雏模型。 相似文献
973.
Karol Kokowski Magdalena Trzeciak Magorzata Sokoowska-Wojdyo 《International journal of molecular sciences》2021,22(24)
The impact of new and emerging therapies on the microenvironment of primary cutaneous lymphomas (PCLs) has been recently raised in the literature. Concomitantly, novel treatments are already used or registered (dupilumab, upadacitinib) and others seem to be added to the armamentarium against atopic dermatitis. Our aim was to review the literature on interleukins 4, 13, 22, and 31, and JAK/STAT pathways in PCLs to elucidate the safety of using biologics (dupilumab, tralokinumab, fezakinumab, nemolizumab) and small molecule inhibitors (upadacitinib, baricitinib, abrocitinib, ruxolitinib, tofacitinib) in the treatment of atopic dermatitis. We summarized the current state of knowledge on this topic based on the search of the PubMed database and related references published before 21 October 2021. Our analysis suggests that some of the mentioned agents (dupilumab, ruxolitinib) and others may have a direct impact on the progression of cutaneous lymphomas. This issue requires further study and meticulous monitoring of patients receiving these drugs to ensure their safety, especially in light of the FDA warning on tofacitinib. In conclusion, in the case of the rapid progression of atopic dermatitis/eczema, especially in patients older than 40 years old, there is a necessity to perform a biopsy followed by a very careful pathological examination. 相似文献
974.
WiMAX技术标准的发展进程 总被引:1,自引:0,他引:1
IEEE 802.16 is very attractive since its publication,.The growth of WiMAX organization accxelerates the development of 802.16 standard,The mobile WiMAX——802.16e standard is especially attractive,This article presents the status quo and the development of WiMAX technical standard along with the work plan of the standard organization in the next stage.The article also introduces the conditions that the development of mobile WiMAX technical standard is attracting people's attention. 相似文献
975.
Keith G. Woodgate 《国际强度与非线性控制杂志
》1997,7(1):29-42
》1997,7(1):29-42
The paper presents a complete solution for the multivariable, continuous-time Generalized ℋ︁∞ (𝒢ℋ︁∞) sensitivity minimization problem. In contrast with existing solutions, derived via polynomial methods, the state-space solution given here is essentially non-iterative. Closed formulae for the minimum and a particular optimal controller are derived in terms of a real Schur decomposition, the solution of two Lyapunov equations and a single, well-conditioned eigenvalue problem. © 1997 by John Wiley & Sons, Ltd. 相似文献
976.
采用静态和动态试验对天然气泄漏量计算模式进行了筛选和验证,同时采用静态试验对不同风速、风向条件下天然气泄漏检测最佳条件进行筛选。试验结果表明:采用折线积分法和相关曲线法计算泄漏最,较能反映输、配气站场泄漏的真实情况;在风速小于0.8m/s(包括静风)时,距设备泄漏点下风向1.5-2.0cm处,由测试浓度计算泄漏速率的准确性较高;当风速为0.8-1.3m/s时,距设备泄漏点下风向1.0cm左右,由测试浓度计算泄漏速率的准确性较高;当风速大于1.3m/s时,应停止进行天然气泄漏检测工作。 相似文献
977.
Olof J. Staffans 《国际强度与非线性控制杂志
》1998,8(14):1189-1217
》1998,8(14):1189-1217
This is the first part in a three part study of the suboptimal full information H∞ problem for a well-posed linear system with input space U, state space H, and output space Y. We define a cost function Q(x0,u)=∫〈y(s),Jy(s)〉Yds, where y∈L2loc( R +; Y) is the output of the system with initial state x0∈H and control u∈L2loc( R +; U), and J is a self-adjoint operator on Y. The cost function Qis quadratic in x0 and u, and we suppose (in the stable case) that the second derivative of Q(x0, u) with respect to u is non-singular. This implies that, for each x0∈H, there is a unique critical control ucrit such that the derivative of Q(x0, u) with respect to u vanishes at u=ucrit. We show that ucrit can be written in feedback form whenever the input/output map of the system has a coprime factorization with a (J, S)-inner numerator; here S is a particular self-adjoint operator on U. A number of properties of this feedback representation are established, such as the equivalence of the (J, S)-losslessness of the factorization and the positivity of the Riccati operator on the reachable subspace. © 1998 John Wiley & Sons, Ltd. 相似文献
978.
利用冷却塔排放烟气技术介绍 总被引:1,自引:0,他引:1
在火力发电厂中烟囱成为火电厂必不可少的重要设施,利用冷却塔排放烟气不但可以节约工程投资和运行费用,而且有利于提高冷却塔的冷却效率,是一种技术先进,经济适用的方法。本文将主要介绍利用冷却塔排放烟气的工艺流程、烟气排放对冷却塔热力性能的影响、排烟冷却塔的结构稳定性及存在的问题。 相似文献
979.
Stable linear fractional transformations (SLFTs) resulting from a 2 × 2-block unit Z in the ring of stable real rational proper matrices are considered in this paper. Several general properties are obtained, including properties with respect to possible pole-zero cancellations and a generic McMillan degree relationship between a transfer matrix and its image under an SLFT. The problem of representing a plant as an SLFT of another plant such that the order of the original plant is exactly equal to the sums of the orders of the SLFT and of the new plant is solved. All such representations can be found by searching for all matching pairs of stable invariant subspaces associated with the plant. In relation to applications of SLFTs, it is shown that if two plants are related by an SLFT, then a one-to-one correspondence between their two respective sets of all stabilizing controllers can be established via a different SLFT. Also, it is shown how to decompose a standard H∞ control problem by means of SLFT into two individual H∞ subproblems, the first involving a nominal plant model and the second involving a certain frequency-shaped approximation error. An example is presented to illustrate the idea of decomposing the complexity of an H∞ control problem. 相似文献
980.
This paper deals with the H∞ filtering problem for a class of discrete-time nonlinear systems with or without real time-varying parameter uncertainty and unknown initial state. For the case when there is no parametric uncertainty in the system, we are concerned with designing a nonlinear H∞ filter such that the induced l2 norm of the mapping from the noise signal to the estimation error is within a specified bound. It is shown that this problem can be solved via one Riccati equation. We also consider the design of nonlinear filters which guarantee a prescribed H∞ performance in the presence of parametric uncertainties. In this situation, a solution is obtained in terms of two Riccati equations. 相似文献