全文获取类型
收费全文 | 7056篇 |
免费 | 345篇 |
国内免费 | 21篇 |
专业分类
电工技术 | 74篇 |
综合类 | 25篇 |
化学工业 | 1491篇 |
金属工艺 | 132篇 |
机械仪表 | 146篇 |
建筑科学 | 374篇 |
矿业工程 | 13篇 |
能源动力 | 269篇 |
轻工业 | 434篇 |
水利工程 | 67篇 |
石油天然气 | 33篇 |
无线电 | 592篇 |
一般工业技术 | 1402篇 |
冶金工业 | 898篇 |
原子能技术 | 50篇 |
自动化技术 | 1422篇 |
出版年
2023年 | 75篇 |
2022年 | 155篇 |
2021年 | 246篇 |
2020年 | 166篇 |
2019年 | 205篇 |
2018年 | 252篇 |
2017年 | 178篇 |
2016年 | 217篇 |
2015年 | 195篇 |
2014年 | 248篇 |
2013年 | 445篇 |
2012年 | 389篇 |
2011年 | 456篇 |
2010年 | 328篇 |
2009年 | 328篇 |
2008年 | 360篇 |
2007年 | 343篇 |
2006年 | 260篇 |
2005年 | 236篇 |
2004年 | 198篇 |
2003年 | 192篇 |
2002年 | 166篇 |
2001年 | 101篇 |
2000年 | 110篇 |
1999年 | 99篇 |
1998年 | 250篇 |
1997年 | 167篇 |
1996年 | 101篇 |
1995年 | 113篇 |
1994年 | 91篇 |
1993年 | 74篇 |
1992年 | 59篇 |
1991年 | 46篇 |
1990年 | 38篇 |
1989年 | 34篇 |
1988年 | 40篇 |
1987年 | 36篇 |
1986年 | 23篇 |
1985年 | 33篇 |
1984年 | 23篇 |
1983年 | 20篇 |
1982年 | 30篇 |
1981年 | 33篇 |
1980年 | 23篇 |
1979年 | 24篇 |
1978年 | 20篇 |
1977年 | 29篇 |
1976年 | 47篇 |
1975年 | 15篇 |
1972年 | 15篇 |
排序方式: 共有7422条查询结果,搜索用时 15 毫秒
31.
Sven Hovmöller 《Ultramicroscopy》1985,17(2):175-192
We present a family of techniques for the transmission electron microscope that generate surface zone-axis patterns. These patterns display the variation of the diffracted-beam intensity as a function of the angle of the incident electrons. The conditions of the experiments are those of reflection high-energy electron diffraction at near grazing incidence. The techniques are: surface convergent-beam diffraction, a surface analogue of the Tanaka method and a modified double-rocking scheme. Experimental results are presented for diffraction from surfaces of MgO and MoS2. We anticipate that surface zone-axis patterns (surface ZAPs) will become established as an important tool for surface characterization, especially when used in conjunction with high-resolution surface imaging and surface energy loss spectroscopy; surface ZAPs may be expected to play, in surface analysis, a role analogous to that played by convergent-beam diffraction in normal transmission electron microscopy. 相似文献
32.
Sven Beyer Christian Jacobi Daniel Kröning Dirk Leinenbach Wolfgang J. Paul 《International Journal on Software Tools for Technology Transfer (STTT)》2006,8(4-5):411-430
In the verified architecture microprocessor (VAMP) project we have designed, functionally verified, and synthesized a processor
with full DLX instruction set, delayed branch, Tomasulo scheduler, maskable nested precise interrupts, pipelined fully IEEE
compatible dual precision floating point unit with variable latency, and separate instruction and data caches. The verification
has been carried out in the theorem proving system PVS. The processor has been implemented on a Xilinx FPGA.
A shorter version of this article with the title “Instantiating uninterpreted functional units and memory system: functional
verification of the VAMP” appeared in [8]. The work reported here was done while all the authors were with Saarland University. 相似文献
33.
Examined how the factors relative in-group size and relative outgroup size (i.e., minority vs. nonminority) affect the perception of in-group and out-group homogeneity. On the basis of social identity theory, we hypothesized that (a) members of minorities would perceive the in-group as more homogeneous than the out-group, whereas members of nonminorities would perceive the reverse; (b) this effect would be strongest on dimensions most strongly correlated with the social categorization; and (c) members of minorities would identify more strongly with their in-group than would members of nonminorities. 192 13–15 yr olds participated in the experiment. On the presumed basis of a perceptual task, approximately half were randomly allocated to minimal social categories, which differed in perceived size relative to an out-group (which also differed in perceived size). They were asked to estimate the homogeneity of the two groups on a number of dimensional attributes. The remaining (control) subjects gave similar estimates under identical conditions, except that they were not allocated to a category. The data confirmed all but the second hypothesis, which was only partially supported. The results were interpreted in terms of social identification processed. Results tend to rule out alternative explanations in terms of an inverse relation between group size and perceived group homogeneity, rating extremity, and in-group favoritism. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
34.
The biochemical basis for considering tannins as digestion inhibitors has been reexamined. Both stimulatory and inhibitory effects of tannins on tryptic hydrolysis are reported. We show how stimulation may result from tannin-induced structural changes in the substrate protein, effectively denaturing it. The surfactant and bile constituent cholic acid also produced similar stimulatory effects. These results have considerable implications for normal digestive physiology as well as for the impact of tannins on argicultural and natural herbivore populations. 相似文献
35.
A. Simon Z. Kntor 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2002,190(1-4):351-356
The formation and deposition of particulates by pulsed laser deposition of Si1−xGex semiconductor alloy thin films are discussed. Using Rutherford backscattering spectrometry with micrometer lateral resolution (micro-RBS) the film composition was measured with high accuracy, even in the presence of particulates with a high areal density of 20,000–30,000 particulates per mm2. We show that on impact of a particulate, the part of the thin film which is already deposited probably melts and its Ge content segregates to the surface. 相似文献
36.
The authors investigated the relationship between transformational leadership behavior and group performance in 218 financial services teams that were branches of a bank in Hong Kong and the United States. Transformational leadership influenced team performance through the mediating effect of team potency. The effect of transformational leadership on team potency was moderated by team power distance and team collectivism, such that higher power distance teams and more collectivistic teams exhibited stronger positive effects of transformational leadership on team potency. The model was supported by data in both Hong Kong and the United States, which suggests a convergence in how teams function in the East and West and highlights the importance of team values. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
37.
The purpose of this brief editorial is to discuss psychology in Québec and some of the foremost researchers who have had a recognized world-wide impact on psychology. Following a brief review of historical facts describing the evolution of psychology in Québec, and of issues related to communicating psychology in French, the contribution of certain distinguished individuals is highlighted. These persons either have played a critical role in international organisations, or have produced scientific work that is widely recognized by their peers. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
38.
Handley Simon J.; Evans Jonathan St. B. T.; Thompson Valerie A. 《Canadian Metallurgical Quarterly》2006,32(3):559
Under the suppositional account of conditionals, when people think about a conditional assertion, "if p then q," they engage in a mental simulation in which they imagine p holds and evaluate the probability that q holds under this supposition. One implication of this account is that belief in a conditional equates to conditional probability [P(q/p)]. In this paper, the authors examine a further implication of this analysis with respect to the wide-scope negation of conditional assertions, "it is not the case that if p then q." Under the suppositional account, nothing categorically follows from the negation of a conditional, other than a second conditional, "if p then not-q." In contrast, according to the mental model theory, a negated conditional is consistent only with the determinate state of affairs, p and not-q. In 4 experiments, the authors compare the contrasting predictions that arise from each of these accounts. The findings are consistent with the suppositional theory but are incongruent with the mental model theory of conditionals. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
39.
The primary visual sources of depth and size information are binocular cues and motion parallax. Here, the authors determine the efficacy of these cues to control prehension by presenting them in isolation from other visual cues. When only binocular cues were available, reaches showed normal scaling of the transport and grasp components with object distance and size. However, when only motion parallax was available, only the transpont component scaled reliably. No additional increase in scaling was found when both cues were available simultaneously. Therefore, although equivalent information is available from binocular and motion parallax information, the latter may be of relatively limited use for the control of the grasp. Binocular disparity appears selectively important for the control of the grasp. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
40.
Mechanisms in damping of mechanical vibration by piezoelectric ceramic-polymer composite materials 总被引:5,自引:0,他引:5
The piezoelectric ceramic (piezoceramic) component of a polymer-piezoelectric ceramic composite converts mechanical energy
into electrical energy and this electrical energy is dissipated as heat in a load resistance, R
x, simulated by a shunted resistance, but provided in practice by a conductive polymer composite matrix. The composite therefore
dissipates the input mechanical energy via the damping mechanism provided by piezoelectric ceramic-conductive matrix material,
as well as the conventional viscoelastic damping provided by the polymer. Mathematical models have been developed to characterize
the damping behaviour of the composites, and the maximum damping ratio of composites can be as high as 23%. A two degrees-of-freedom
(2DOF) experimental setup was developed to test the validity of the models. The experimental results are in good agreement
with the theoretical predictions. 相似文献