全文获取类型
收费全文 | 10666篇 |
免费 | 474篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 118篇 |
综合类 | 38篇 |
化学工业 | 2260篇 |
金属工艺 | 226篇 |
机械仪表 | 184篇 |
建筑科学 | 601篇 |
矿业工程 | 20篇 |
能源动力 | 281篇 |
轻工业 | 839篇 |
水利工程 | 87篇 |
石油天然气 | 44篇 |
武器工业 | 1篇 |
无线电 | 660篇 |
一般工业技术 | 1449篇 |
冶金工业 | 2468篇 |
原子能技术 | 58篇 |
自动化技术 | 1817篇 |
出版年
2023年 | 85篇 |
2022年 | 202篇 |
2021年 | 333篇 |
2020年 | 184篇 |
2019年 | 200篇 |
2018年 | 270篇 |
2017年 | 234篇 |
2016年 | 314篇 |
2015年 | 233篇 |
2014年 | 337篇 |
2013年 | 624篇 |
2012年 | 482篇 |
2011年 | 614篇 |
2010年 | 428篇 |
2009年 | 491篇 |
2008年 | 453篇 |
2007年 | 411篇 |
2006年 | 341篇 |
2005年 | 292篇 |
2004年 | 269篇 |
2003年 | 260篇 |
2002年 | 189篇 |
2001年 | 137篇 |
2000年 | 137篇 |
1999年 | 170篇 |
1998年 | 693篇 |
1997年 | 447篇 |
1996年 | 291篇 |
1995年 | 195篇 |
1994年 | 192篇 |
1993年 | 194篇 |
1992年 | 82篇 |
1991年 | 99篇 |
1990年 | 88篇 |
1989年 | 111篇 |
1988年 | 86篇 |
1987年 | 72篇 |
1986年 | 76篇 |
1985年 | 71篇 |
1984年 | 63篇 |
1983年 | 51篇 |
1982年 | 51篇 |
1981年 | 44篇 |
1980年 | 51篇 |
1979年 | 33篇 |
1978年 | 36篇 |
1977年 | 84篇 |
1976年 | 158篇 |
1975年 | 42篇 |
1973年 | 36篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
This paper presents work directed at capturing the entrepreneurial and collaborative activity of university researchers. The Triple Helix points to the emergence of the entrepreneurial university as well as to an increasing overlay of activities in universities, industry and government. This study explores ways in which patent-based metrics could be utilized in a Triple Helix context, and how hybrid indicators could be developed by combining patent with survey data. More specifically, it aims to develop indicators that connect technological inventiveness of university researchers to both funding organizations and users, as well as to entrepreneurial activities by academics. The paper develops a simplified model of the innovation process to benchmark the relevance of the indicators to the Triple Helix. An analysis of Finnish academic patents illustrates that patent data can already provide useful indicators but, on its own, cannot provide information about how academic patents are interconnected with government or industry through funding or utilization links. An exclusive analysis of patents can point to patent concentrations on certain universities, to inventors and assignees, or to potential gaps in translating applied science into industrial technology. However, the patent data had to be combined with an inventor survey in order to relate academic patents more to their Triple Helix environment. The survey indicated that most patented academic inventions are connected to (often publicly funded) scientific research by the inventors and tend to be utilized in large firms rather than in start-up companies founded by academic entrepreneurs. 相似文献
102.
103.
104.
Fluorescence microscopy techniques have become important tools in mitosis research. The well-known disadvantages of fluorescence microscopy, rapid bleaching, phototoxicity and out-of-focus contributions blurring the in-focus image are obstacles which still need to be overcome. Confocal fluorescence microscopy has the potential to improve our capabilities of analyzing cells, because of its excellent depth-discrimination and image processing power. We have been using a confocal fluorescence microscope for the study of the mechanism of poleward chromosome movement, and report here (1) a cell preparation technique, which allows labeling of fixation sensitive spindle antigens with acceptable microtubule preservation; (2) the use of image processing methods to represent the spatial distribution of various labeled elements in pseudocolour; (3) a novel immunoelectron microscopic labeling method for microtubules, which allows the visualization of their distribution in semithin sections at low magnification; and (4) a first attempt to study microtubule dynamics with a confocal fluorescence microscope in living cells, microinjected with rhodamine labeled tubulin. Our experience indicates that confocal fluorescence microscopy provides real advantages for the study of spatial colocalization of antigens in the mitotic spindle. It does not, however, overcome the basic limits of resolution of the light microscope. Therefore, it has been necessary to use an electron microscopic method. Our preliminary results with living cells show that it is possible to visualize the entire microtubule network in stereo, but that the sensitivity of the instrument is still too low to perform dynamic time studies. It will be worthwhile to further develop this new type of optical instrumentation and explore its usefulness on both fixed and living cells. 相似文献
105.
The Steady radial distribution of chemical species in a wire‐to‐cylinder ozone generator filled with pure oxygen has been computed by applying four different plasma chemistry models of increasing complexity. The most complete model considers ten species (e, O2 +, O2 ?, O3 ?, O?, O2, O2(1Δg), O2(1∑g +), O and O3) and 79 reactions, including ionization by electron impact, electron attachment and detachment, electron-ion recombination, charge transfer, etc. The chemical model is coupled with the electrical model through Poisson's equation. The spatially averaged ozone density has been computed as a function of the current intensity and compared with the experimental values obtained by UV spectroscopy. 相似文献
106.
van Gelderen Amos; Schoonen Rob; de Glopper Kees; Hulstijn Jan; Simis Annegien; Snellings Patrick; Stevenson Marie 《Canadian Metallurgical Quarterly》2004,96(1):19
The authors report results of a study into the role of components of first-language (L1; Dutch) and second-language (L2; English) reading comprehension. Differences in the contributions of components of L1 and L2 reading comprehension are analyzed, in particular processing speed in L1 and L2. Findings indicate that regression weights of the L1 and L2 components are different. Although correlations between most processing speed components and reading comprehension are substantial, there are no unique contributions to the explanation of either L1 or L2 reading comprehension when linguistic and metacognitive knowledge are accounted for. In addition, L1 reading comprehension is shown to have a large contribution to L2 reading comprehension, supporting theories of L1-L2 transfer of reading skills. Results are discussed from a developmental perspective. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
107.
Sialon ceramics are a modern type of engineering ceramics with excellent mechanical, thermal and corrosion resistant properties. This paper describes the structure characterisation of porous sialon ceramics. It is possible to significantly improve the strength and crack resistance of sialon ceramics as a result of a reduction of the volume fraction of porosity. 相似文献
108.
Leedham Beth; Meyerowitz Beth E.; Muirhead Jan; Frist William H. 《Canadian Metallurgical Quarterly》1995,14(1):74
We explored the relations between positive expectations and adjustment, adherence, and health in cardiac transplant patients. Thirty-one patients and their nurse completed questionnaires before transplantation and at 3 times after surgery. As predicted, patients' self-reported positive expectations were generally associated with good mood, adjustment to the illness, and quality of life, even in patients who experienced health setbacks. High preoperative expectations predicted later adherence to a complex medical regimen. Positive expectations measured before the transplant predicted a substantial amount of the variance in the nurse's ratings of physical health 6 months after surgery, covarying for adherence behavior and preoperative health. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
109.
A scheme of force variation during the compression of a spring in both elastic and elastic-plastic state is presented. For the elastic state it has been found that equivalent load increments occur with equivalent deflection increments. In the elastic-plastic state equivalent load increments correspond to higher deflection increments. Prestressing the spring increases the range of the elastic deformation of a spring. Equations for the determination of torsional moment during prestressing and relationships of total non-dilatational strain versus elastic strain and radii of elastic zone are also presented. The effect of characteristic spring dimensions and non-dilatational strain on spring deflection has been determined. A nomogram for the determination of the resultant equivalent strain as a function of external load, also considering residual stress distribution, has as well been elaborated. 相似文献
110.
A membrane fraction was isolated from the water soluble fraction of bovine lens by increasing the density of the water soluble fraction with KBr and subjecting it to overnight centrifugation at 100000 g. We have called this fraction, which floats to the top of the mixture upon centrifugation, the non-sedimenting membrane fraction (NSMF). Electron microscopy of the NSMF revealed that it is composed of the expected membrane structures of unit membrane, fiber junction and cytoskeleton. Significantly less of the total membrane of the NSMF was devoted to fiber junction (22.8%) than in the sedimenting membrane fraction (SMF) (41.1%) prepared by sucrose density centrifugation of the water insoluble fraction. The NSMF accounted for about 7-12% of the total bovine lens membrane, and preliminary experiments demonstrated that a similar fraction could be isolated from the water soluble fraction of lenses from rats, rabbits, chickens and humans. The NSMF contained about 0.9 mg total lipid per mg total membrane protein, which was significantly greater than the value obtained for the SMF (0.5 mg total lipid per mg total membrane protein). The greater relative amount of total lipid in the NSMF was due to a significantly greater relative amount of phospholipid in the NSMF which was further reflected by the observation that the cholesterol: phospholipid molar ration of the NSMF (0.58) was significantly less than that of the SMF (0.88). Thus the relative lipid composition of the NSMF was significantly different than that of the SMF. Although the phospholipid content of the NSMF was greater than that of the SMF, the compositions of the phospholipids in the two membrane fractions were similar. The NSMF possessed essentially the same polypeptides (both extrinsic and intrinsic) which were found in the SMF. The NSMF was found to be distributed throughout the lens in a proportionate manner. We conclude that the NSMF may account for most of the lipid which remains in the water soluble fraction of the normal bovine lens after sedimentation of the water insoluble fraction. This membrane fraction substantially differs from the SMF in terms of structure and relative lipid composition. We speculate that the NSMF may represent a specialised domain of the fiber cell plasma membrane which has been previously unrecognized. 相似文献