全文获取类型
收费全文 | 989篇 |
免费 | 63篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 8篇 |
综合类 | 8篇 |
化学工业 | 235篇 |
金属工艺 | 16篇 |
机械仪表 | 11篇 |
建筑科学 | 47篇 |
能源动力 | 29篇 |
轻工业 | 146篇 |
水利工程 | 12篇 |
石油天然气 | 2篇 |
无线电 | 131篇 |
一般工业技术 | 173篇 |
冶金工业 | 84篇 |
原子能技术 | 13篇 |
自动化技术 | 138篇 |
出版年
2023年 | 11篇 |
2022年 | 12篇 |
2021年 | 23篇 |
2020年 | 12篇 |
2019年 | 16篇 |
2018年 | 21篇 |
2017年 | 27篇 |
2016年 | 20篇 |
2015年 | 25篇 |
2014年 | 39篇 |
2013年 | 35篇 |
2012年 | 55篇 |
2011年 | 57篇 |
2010年 | 46篇 |
2009年 | 47篇 |
2008年 | 30篇 |
2007年 | 45篇 |
2006年 | 33篇 |
2005年 | 32篇 |
2004年 | 27篇 |
2003年 | 29篇 |
2002年 | 21篇 |
2001年 | 14篇 |
2000年 | 16篇 |
1999年 | 16篇 |
1998年 | 33篇 |
1997年 | 26篇 |
1996年 | 24篇 |
1995年 | 19篇 |
1994年 | 12篇 |
1993年 | 16篇 |
1992年 | 9篇 |
1991年 | 11篇 |
1990年 | 8篇 |
1989年 | 10篇 |
1988年 | 5篇 |
1987年 | 10篇 |
1986年 | 12篇 |
1985年 | 18篇 |
1984年 | 16篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1981年 | 18篇 |
1980年 | 14篇 |
1978年 | 9篇 |
1977年 | 14篇 |
1976年 | 13篇 |
1975年 | 6篇 |
1974年 | 3篇 |
1973年 | 4篇 |
排序方式: 共有1053条查询结果,搜索用时 15 毫秒
991.
A comparison is reported of fineness results obtained for 27 lots of scoured wool by the projection-microscope and air-flow methods. The sampling of the scoured wool was done by core-boring, and the cores were hand-carded before air-flow tests were made. The sub-samples for projection-microscope measurement were cut into snippets 1 mm long in order to obtain a length-biassed sample. The air-flow apparatus was calibrated with reference tops in five different forms. The results show that there exists a systematic difference between the air-flow and projection-microscope mean diameters of scoured wool when the air-flow instrument is calibrated with reference tops in the original state. A better agreement results by hand-carding the test samples of the reference tops, but the closest agreement is obtained by cutting, washing, and hand-carding these test samples so that their condition is similar to that of the core sample being tested. Provided that this kind of calibration were applied, the mean diameter of washed wool could be determined by air-flow testing of cored and hand-carded samples. 相似文献
992.
Magdalena Staniszewska Pedro Fragoso Costa Matthias Eiber Jasmin M. Klose Jasmin Wosniack Henning Reis Tibor Szarvas Boris Hadaschik Katharina Lückerath Ken Herrmann Wolfgang P. Fendler Janette Iking 《International journal of molecular sciences》2021,22(14)
Prostate-specific membrane antigen (PSMA)-directed radioligand therapy (RLT) prolongs overall survival in men with metastatic castration-resistant prostate cancer (mCRPC). However, men with low PSMA expression are excluded from RLT. We explored the effect of androgen receptor blockade with enzalutamide on PSMA expression. Assessment of PSMA and androgen receptor (AR) expression on the human PC cell lines 22Rv1, C4-2, and LNCaP by immunohistochemistry and flow cytometry revealed low (22Rv1) and high (C4-2 and LNCaP) PSMA expression, and high, comparable AR positivity. Treatment with enzalutamide increased PSMA levels in 22Rv1, C4-2, and LNCaP (2.2/2.3/2.6-fold, p = 0.0005/0.03/0.046) after one week compared to DMSO-treated controls as assessed by flow cytometry. NOD/Scid mice bearing 22Rv1 tumors were treated with enzalutamide for two weeks. Positron emission tomography/computed tomography (PET/CT) demonstrated higher tumor uptake of 68Ga-PSMA after enzalutamide treatment (p = 0.004). Similarly, a clinical case with low baseline PSMA avidity demonstrated increased uptake of 68Ga-PSMA after enzalutamide on PET/CT and post-therapeutic 177Lu-PSMA scintigraphy in a patient with mCRPC. Enzalutamide induced PSMA expression in the 22Rv1 xenograft model and in an mCRPC patient, both with low baseline tumoral PSMA levels. Therefore, enzalutamide pre-treatment might render patients with low PSMA expression eligible for 177Lu-PSMA RLT. 相似文献
993.
Lai X Zheng Y Ipsen H Jacobsen S Larsen JN Løwenstein H Søndergaard I 《Applied spectroscopy》2007,61(11):1184-1190
A new method for particle size determination in polystyrene and aluminum hydroxide suspensions using near-infrared transmittance spectroscopy is described. Mono-dispersed polystyrene particle size standards were used to establish the calibration model. The particle sizes used in the study are similar to the wavelength range of 700-1300 nm, where light scattering is wavelength dependent. The wavelength dependency of near-infrared (NIR) absorbance is found to be linear with the particle size when the analysis is based on the same spectrum starting point (the same absorbance at 700 nm). Partial least squares regression (PLSR) is applied to model this linear relationship. Compared to laser diffraction (LD) the NIR method has similar accuracy and precision in the measurement of particles with a uniform size. For a sample containing multiple sizes of particles, the mean size measured by the NIR method is shown to be weighted by the particle mass. The application of the model to aluminum hydroxide suspension shows that the NIR method is suitable for the detection of particle size changes during the production process and storage. The advantages of the NIR method are that no knowledge of the refractive index and the concentration of a sample are necessary and that the method is fast and easy to operate. 相似文献
994.
Voges KL Mason CL Brooks JC Delmore RJ Griffin DB Hale DS Henning WR Johnson DD Lorenzen CL Maddock RJ Miller RK Morgan JB Baird BE Gwartney BL Savell JW 《Meat science》2007,77(3):357-364
Beef from retail and foodservice establishments in 11 US cities was evaluated using Warner-Bratzler shear (WBS) and consumer evaluation panels. Postmortem aging times ranged from 3 to 83d for retail and 7 to 136d for foodservice with mean aging times of 22.6d and 30.1d, respectively. For retail, the three cuts from the round - top round, bottom round, and eye of round - had the highest (P<0.05) WBS values compared to cuts from the chuck, rib, and loin. Top loin steaks had the lowest (P<0.05) WBS value compared to ribeye and top sirloin foodservice steaks. Retail bone-in top loin, top loin, ribeye, T-bone, and porterhouse received the highest (P<0.05) ratings by consumers for overall like and like tenderness. Quality grade had little or no effect on foodservice sensory evaluations. Improvements in round tenderness are needed to increase consumer acceptability. 相似文献
995.
Székely Eszter; Tiemeier Henning; Arends Lidia R.; Jaddoe Vincent W. V.; Hofman Albert; Verhulst Frank C.; Herba Catherine M. 《Canadian Metallurgical Quarterly》2011,11(2):425
Very few large-scale studies have focused on emotional facial expression recognition (FER) in 3-year-olds, an age of rapid social and language development. We studied FER in 808 healthy 3-year-olds using verbal and nonverbal computerized tasks for four basic emotions (happiness, sadness, anger, and fear). Three-year-olds showed differential performance on the verbal and nonverbal FER tasks, especially with respect to fear. That is to say, fear was one of the most accurately recognized facial expressions as matched nonverbally and the least accurately recognized facial expression as labeled verbally. Sex did not influence emotion-matching nor emotion-labeling performance after adjusting for basic matching or labeling ability. Three-year-olds made systematic errors in emotion-labeling. Namely, happy expressions were often confused with fearful expressions, whereas negative expressions were often confused with other negative expressions. Together, these findings suggest that 3-year-olds' FER skills strongly depend on task specifications. Importantly, fear was the most sensitive facial expression in this regard. Finally, in line with previous studies, we found that recognized emotion categories are initially broad, including emotions of the same valence, as reflected in the nonrandom errors of 3-year-olds. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
996.
Thomas Ryll Henning Galinski Lukas Schlagenhauf Pierre Elser Jennifer L. M. Rupp Anja Bieberle‐Hutter Ludwig J. Gauckler 《Advanced functional materials》2011,21(3):401-401
Agglomerated Pt thin films have been proposed as electrodes for electrochemical devices like micro‐solid oxide fuel cells (μ‐SOFCs) operating at low temperatures. However, comprehensive studies elucidating the interplay between agglomeration state and electrochemical properties are lacking. In this contribution the electrochemical performance of agglomerated and “dense” Pt thin film electrodes on yttria‐stabilized‐zirconia (YSZ) is correlated with their microstructural characteristics. Besides the microscopically measurable triple‐phase‐boundary (tpb) where Pt, YSZ and air are in contact, a considerable contribution of “nanoscopic” tpbs to the electrode conductivity resulting from oxygen permeable grain boundaries is identified. It is demonstrated that “dense” Pt thin films are excellent electrodes provided their grain size and thickness are in the nanometer range. The results disprove the prevailing idea that the performance of Pt thin film electrodes results from microscopic and geometrically measurable tpbs only. 相似文献
997.
Metabolomics has become an integral part of many life-science applications but is technically still very challenging. Numerous analytical approaches are needed as metabolites have very broad concentration ranges and extremely diverse chemical properties. Configuring a metabolomics pipeline and exploring its merits is a complex task that depends on effective and transparent evaluation procedures. Unfortunately, there are no widely applicable methods to evaluate how well acquired data can approximate actual concentration differences. Here, we introduce a powerful approach that provides semiquantitative calibration curves over a biologically defined concentration range for all detected compounds. By performing metabolomics on a stepwise gradient between two biological specimens, we obtain a data set where each peak would ideally show a linear dependency on the mixture ratio. An example gradient between extracts of tomato leaf and fruit demonstrates good calibration statistics for a large proportion of the peaks but also highlights cases with strong background-dependent signal interference. Analysis of artificial biological gradients is a general and inexpensive tool for calibration that greatly facilitates data interpretation, quality control and method comparisons. 相似文献
998.
Henning H. Ewe Eduard W. Justi Hans-Joachim Selbach 《Energy Conversion and Management》1980,20(2):75-83
Alkaline H2O2 fuel cells with supported electrodes offer great current densities. Difficulties were raised by the nonreproducibility of the electrode performance caused by variations of the contact pressures of the meshes supporting and compressing the catalysts powder layers. The authors checked the significance of this contact pressure and found an essential improvement of the reproducibility by controlling the contact pressure. Furthermore the current densities at constant polarizations were increased significantly by the optimization of the contact pressure. This improvement was interpreted by a simple pore system, the gas distribution and the diaphragm resistivity inside the catalyst layers. 相似文献
999.
Mohammad-Hesam Ejtehadi Hubert Klaus Stefanie Sommer Henning Haensel Jan Scholten 《The International Journal of Advanced Manufacturing Technology》2011,55(9-12):983-995
Spherical joints are used in automotive chassis to connect components. They are used in locations where force transmission and at least two rotational degrees of freedom are required simultaneously. The source of wear in such joints specifically in the running-in phase has been an important question in the automotive industry. In this work, the main cause of running-in wear in a specific type of spherical chassis joint is identified experimentally. To verify this identification, simplified tribological tests are conducted on sample geometries of polyoxymethylene representing contact surfaces in spherical joint. The results are used to develop an algorithm which describes the running-in phase in a wear simulation tool. Material tests for polyoxymethylene are conducted in order to identify the stress?Cstrain behaviour which is then used for non-linear finite element simulations in the implemented algorithm. The simplified tribological experiments are subsequently simulated using the modified wear simulation tool for validation. 相似文献
1000.
Micro- and nanostructuring of glass surfaces is normally realized by pattern transfer via a lithographical process including wet chemical or reactive ion (i.e. dry) etching. In this contribution we introduce a technology for roughening glass surfaces without lithography. We make use of self-masking that appears under certain process parameters during reactive ion etching in an Ar/CF4-plasma. This way a multitude of different surface roughness morphologies can be realized. In a first step an about 10 nm thin unstructured metallic layer (preferably of Cu) is deposited onto the cleaned glass substrates. This layer is not laterally structured by lithography, but rather by nucleation or coalescence. These metal spots impose an initial etch pattern on the glass surface, which is getting increasingly coarse during further etching. Choice of the metal layer and variation of the etch parameters like etch time, total pressure, gas fluxes of Ar and CF4, ion energy, and plasma density affect the resulting morphology. Each morphology is characterized by its root-mean-square surface roughness and the correlation length of its height profile. We mainly used borosilicate thin glass D263?T from Schott AG, Mainz, Germany as substrates. The resulting individual surface structures like cones, hemispheres, pits, and trenches possess typical dimensions of 0.1 to 0.8 μm. The diverse surface roughness morphologies show individual scattering characteristics so that nearly any proportion of diffuse to total transmitted light power is realized. Thus user-defined light diffusers are feasible. The process can be scaled up to large substrate sizes. 相似文献