全文获取类型
收费全文 | 6784篇 |
免费 | 150篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 60篇 |
综合类 | 3篇 |
化学工业 | 947篇 |
金属工艺 | 51篇 |
机械仪表 | 55篇 |
建筑科学 | 324篇 |
矿业工程 | 86篇 |
能源动力 | 104篇 |
轻工业 | 613篇 |
水利工程 | 61篇 |
石油天然气 | 11篇 |
无线电 | 356篇 |
一般工业技术 | 790篇 |
冶金工业 | 2781篇 |
原子能技术 | 19篇 |
自动化技术 | 674篇 |
出版年
2022年 | 32篇 |
2021年 | 78篇 |
2020年 | 45篇 |
2019年 | 55篇 |
2018年 | 64篇 |
2017年 | 81篇 |
2016年 | 94篇 |
2015年 | 70篇 |
2014年 | 81篇 |
2013年 | 290篇 |
2012年 | 194篇 |
2011年 | 253篇 |
2010年 | 212篇 |
2009年 | 216篇 |
2008年 | 280篇 |
2007年 | 275篇 |
2006年 | 201篇 |
2005年 | 232篇 |
2004年 | 175篇 |
2003年 | 213篇 |
2002年 | 188篇 |
2001年 | 147篇 |
2000年 | 130篇 |
1999年 | 156篇 |
1998年 | 376篇 |
1997年 | 232篇 |
1996年 | 232篇 |
1995年 | 162篇 |
1994年 | 170篇 |
1993年 | 201篇 |
1992年 | 155篇 |
1991年 | 83篇 |
1990年 | 140篇 |
1989年 | 122篇 |
1988年 | 110篇 |
1987年 | 112篇 |
1986年 | 108篇 |
1985年 | 110篇 |
1984年 | 87篇 |
1983年 | 69篇 |
1982年 | 68篇 |
1981年 | 75篇 |
1980年 | 51篇 |
1979年 | 80篇 |
1978年 | 47篇 |
1977年 | 59篇 |
1976年 | 83篇 |
1975年 | 36篇 |
1974年 | 33篇 |
1973年 | 45篇 |
排序方式: 共有6935条查询结果,搜索用时 296 毫秒
11.
12.
Howard George S.; Maxwell Scott E.; Berra Susan M.; Sternitzke Mary E. 《Canadian Metallurgical Quarterly》1985,70(1):233
Updated the report of W. M. Cox and V. Catt (see record 1978-21651-001) by determining the 40 top contributing institutions to the Journal of Applied Psychology, 1976–1982, and assessed the generalizability of productivity rankings based solely on contributions to this journal. A number of industrial and organizational psychologists were asked to indicate all the journals in which psychologists in the field were likely to publish. Five journals suggested by these nominators were used for comparison in the review. A list of the 40 most productive graduate programs based on these 5 journals is included. Results show the inadequacy of Cox and Catt's decision to base productivity ratings solely on contributions to 1 journal. Using 5 journals, 4 programs were catapulted into the top 10 rankings, while 7 programs dropped from top rankings in the Cox study (1970–1975) to below the 65th rank in the present study. Using only the Journal of Applied Psychology contributions, 2 of these programs ranked in the top 10, 1976–1982. (5 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
13.
Douglas W. Cooper 《Particulate Science and Technology》1989,7(4):371-380
Aerogels are highly porous materials made by removing the liquid phase of a dilute suspension of solids by taking off the vapor under super-critical temperature and pressure conditions. The aerogel structure has a skeleton of nanometer-size elements forming pores that are tens of nanometers in dimension. In some cases the structure of the aerogel arises from clusters having fractal geometry. The collection efficiency and pressure drop for such material is predicted here from models in the literature. A quality factor is used to compare aerogel material with other filter materials. The quality factor relating gas filtration efficiency with pressure drop is predicted to be unusually high for these materials in comparison with other common fibrous filter media, predicting lower flow resistance for aerogels at equivalent particle collection efficiency levels. 相似文献
14.
The interactions of the antihistaminic drug chlorpheniramine maleate (CPM) with the negatively charged polyelectrolytes poly(sodium 4-styrenesulfonate) (PSS) and poly(acrylic acid) (PAA) are studied by the washing method of the diafiltration technique at conditions simulating those of the small intestine such as pH 7.5 and 0.13 M NaCl. The results are compared with those already reported involving other pharmacologically important polyelectrolytes such as alginic acid (ALG), carboxymethylcellulose (CMC), and κ- and ι-carrageenan (κ- and ι-CAR). As in the case of ALG, CMC, and CAR, interactions of CPM with PAA appear to be electrostatic and are cleaved in the presence of 0.13 M NaCl. On the contrary, apart from electrostatic interactions, additional interactions are found with PSS and residual interactions are kept in the presence of 0.13 M NaCl, a fact that may be attributed to π-π interactions and hydrophobic forces. The effect of the addition of 4 M urea, branched poly(ethyleneimine) (BPEI), and poly(vinylpyrrolidone) (PVP) is also studied. The addition of urea 4 M or 0.001 M BPEI produces a decrease on the amounts of counterions bound to PSS at infinite elution, while the addition of PVP does not produce any change on the diafiltration profiles. 相似文献
15.
S. K. Chen A. Serquis G. Serrano K. A. Yates M. G. Blamire D. Guthrie J. Cooper H. Wang S. Margadonna J. L. MacManus‐Driscoll 《Advanced functional materials》2008,18(1):113-120
By applying a combination of characterisation tools, changes in structural and superconducting properties with nominal Mg non‐stoichiometry in MgxB2 are found. The non‐stoichiometry produces enhanced in‐field critical current densities (Jc's) and upper critical field / irreversibility field (Hc2/Hirr(T)) values. Upper critical fields of ~ 21 T (4.2 K) were obtained in nominal Mg‐deficient samples compared to ~ 17 T (4.2 K) for near‐stoichiometric samples. 相似文献
16.
The effects of moisture, temperature, and ultraviolet (UV) light on performance of natural‐fiber–plastic composites (NFPC) were assessed. We conducted short‐term tests in the laboratory and long‐term tests under natural exposure and measured changes in mechanical properties and color in samples of the composite. Chemical changes of the composite's materials were measured by X‐ray photoelectron spectroscopy to elucidate the mechanisms of chemical transformations on the material surface. Relative humidity highly affected the modulus of rupture (MOR) and the modulus of elasticity (MOE), and had a greater effect than temperature and UV exposure on performance of the composite. The lightness of the composite was increased by the UV effect in the short‐ and the long‐term tests. The X‐ray photoelectron spectroscopy (XPS) analysis suggested that the composite was protected by the UV absorber. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 2570–2577, 2006 相似文献
17.
Nonnative plant species are causing enormous ecological and environmental impacts from local to global scale. Remote sensing images have had mixed success in providing spatial information on land cover characteristics to land managers that increase effective management of invasions into native habitats. However, there has been limited evaluation of the use of hyperspectral data and processing techniques for mapping specific invasive species based on their spectral characteristics. This research evaluated three different methods of processing hyperspectral imagery: minimum noise fraction (MNF), continuum removal, and band ratio indices for mapping iceplant (Carpobrotus edulis) and jubata grass (Cortaderia jubata) in California's coastal habitat. Validation with field sampling data showed high mapping accuracies for all methods for identifying presence or absence of iceplant (97%), with the MNF procedure producing the highest accuracy (55%) when the classes were divided into four different densities of iceplant. 相似文献
18.
The eye movements of young and older adults were tracked as they read sentences varying in syntactic complexity. In Experiment 1, cleft object and object relative clause sentences were more difficult to process than cleft subject and subject relative clause sentences; however, older adults made many more regressions, resulting in increased regression path fixation times and total fixation times, than young adults while processing cleft object and object relative clause sentences. In Experiment 2, older adults experienced more difficulty than young adults while reading cleft and relative clause sentences with temporary syntactic ambiguities created by deleting the that complementizers. Regression analyses indicated that readers with smaller working memories need more regressions and longer fixation times to process cleft object and object relative clause sentences. These results suggest that age-associated declines in working memory do affect syntactic processing. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
19.
The paper describes a prototype system called HiSQL (Historical SQL) which extends the functionality of SQL in manipulating
historical data, by providing functions for spatial and temporal processing. Conceptually the paper is divided into three
parts: the first part deals with the design and architecture of the system; the second part introduces a case study (the defters);
and the third part describes specific functions for spatial and temporal processing of serial documents. The paper concludes
with a comparison between HiSQL and SQL and suggestions for further work.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
20.
JE Myers T Mieczkowski J Perel D Abbondanza TB Cooper JJ Mann 《Canadian Metallurgical Quarterly》1994,35(2):112-120
Serotonergic responsivity was assessed in 20 psychiatric patients by the prolactin response to a fenfluramine challenge test. During the fenfluramine challenge 6 of 20 patients (30%) spontaneously reported psychopathologic reactions that included: increased anxiety/agitation, psychotic symptoms, illusions, mood elevation, and anergia. The time of peak behavioral symptoms (2.5 +/- 0.8 hrs) corresponded closely to the time of peak increase in prolactin levels (3.0 +/- 1.1 hr). Abnormal behavioral responders had statistically significant greater increases in prolactin 1 to 4 hr after fenfluramine when compared to normal responders. Patients who developed an abnormal psychopathologic response to fenfluramine were characterized by higher levels of anxiety and agitation at the time of admission to the hospital but otherwise were not distinguishable on the basis of severity of other psychiatric symptoms. This study suggests that increased serotonergic transmission may trigger anxiety, psychosis, and mood elevation in specific vulnerable individuals, whereas other patients with similar psychiatric illnesses are not affected. 相似文献