全文获取类型
收费全文 | 4484篇 |
免费 | 176篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 61篇 |
综合类 | 3篇 |
化学工业 | 853篇 |
金属工艺 | 50篇 |
机械仪表 | 76篇 |
建筑科学 | 162篇 |
矿业工程 | 6篇 |
能源动力 | 121篇 |
轻工业 | 377篇 |
水利工程 | 57篇 |
石油天然气 | 12篇 |
无线电 | 327篇 |
一般工业技术 | 853篇 |
冶金工业 | 1036篇 |
原子能技术 | 29篇 |
自动化技术 | 643篇 |
出版年
2023年 | 26篇 |
2022年 | 49篇 |
2021年 | 94篇 |
2020年 | 71篇 |
2019年 | 72篇 |
2018年 | 115篇 |
2017年 | 89篇 |
2016年 | 100篇 |
2015年 | 69篇 |
2014年 | 123篇 |
2013年 | 289篇 |
2012年 | 230篇 |
2011年 | 285篇 |
2010年 | 200篇 |
2009年 | 221篇 |
2008年 | 260篇 |
2007年 | 259篇 |
2006年 | 204篇 |
2005年 | 191篇 |
2004年 | 178篇 |
2003年 | 138篇 |
2002年 | 149篇 |
2001年 | 92篇 |
2000年 | 80篇 |
1999年 | 63篇 |
1998年 | 86篇 |
1997年 | 83篇 |
1996年 | 64篇 |
1995年 | 70篇 |
1994年 | 67篇 |
1993年 | 63篇 |
1992年 | 59篇 |
1991年 | 31篇 |
1990年 | 42篇 |
1989年 | 48篇 |
1988年 | 41篇 |
1987年 | 41篇 |
1986年 | 43篇 |
1985年 | 48篇 |
1984年 | 34篇 |
1983年 | 30篇 |
1982年 | 22篇 |
1981年 | 29篇 |
1980年 | 14篇 |
1979年 | 26篇 |
1978年 | 13篇 |
1977年 | 14篇 |
1975年 | 8篇 |
1974年 | 6篇 |
1972年 | 7篇 |
排序方式: 共有4666条查询结果,搜索用时 0 毫秒
11.
O'Farrell Timothy J.; Fals-Stewart William; Murphy Marie; Murphy Christopher M. 《Canadian Metallurgical Quarterly》2003,71(1):92
This study examined partner violence in the year before and the year after individually based, outpatient alcoholism treatment for 301 married or cohabiting male alcoholic patients and used a demographically matched nonalcoholic comparison sample. In the year before treatment, 56% of the alcoholic patients had been violent toward their female partner, 4 times the rate of 14% in the comparison sample. In the year after treatment, violence decreased significantly to 25% of the alcoholic sample but remained higher than in the comparison group. Among remitted alcoholics after treatment, violence prevalence of 15% was nearly identical to the comparison sample and half the rate among relapsed patients (32%). Thus, partner violence decreased after alcoholism treatment, and clinically significant violence reductions occurred for patients whose alcoholism was remitted after treatment. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
12.
Timothy G. Trucano Dennis E. Grady Glenn D. Kubiak Marlin E. Kipp Richard E. Olson Archie Farnsworth 《International Journal of Impact Engineering》1995,17(4-6):873-890
xtreme
ltra
iolet
ithography (EUVL) seeks to apply radiation in a wavelength region centered near 13 nm to produce microcircuits having feature sizes 0.1 micron or less. A critical requirement for the commercial application of this technology is the development of an economical, compact source of this radiation which is suitable for lithographic applications. A good candidate is a laser-plasma source, which is generated by the interaction of an intermediate intensity laser pulse (up to 1012 W/cm2) with a metallic target. While such a source has radiative characteristics which satisfy the needs of an EUVL source, the debris generated during the laser-target interaction strikes at the economy of the source. Here, we review the use of concepts and computer modeling, originally developed for hypervelocity impact analysis, to study this problem. 相似文献
13.
14.
The authors present a method for solving a class of optimization problems with nonsmooth constraints. In particular, they apply the method to the design of narrowband minimum-power antenna array processors which are robust in the presence of errors such as array element placement, look direction misalignment, and frequency offset. They first show that the constrained minimum power problem has a unique global minimum provided that the constraint set is nonempty. Then it is shown how the design problem derived directly from considerations of the sensitivity of the antenna array processor to errors can be transformed into a quadratic programming problem with linear inequality constraints which can be solved efficiently by the standard active set strategy. They also present numerical results for two types of nonsmooth constraints developed to provided robustness. These results confirm the effectiveness of the method 相似文献
15.
A meta-analysis was conducted on 91 studies to derive a correlation matrix for adult age, speed of processing, primary–working memory, episodic memory, reasoning, and spatial ability. Structural equation modeling with a single latent common cognitive factor showed that all cognitive measures shared substantial portions of age-related variance. A mediational model revealed that speed of processing and primary–working memory appear to be important mediators of age-related differences in the other measures. However, not all of the age-related influences were mediated. An examination of quadratic age effects and correlational patterns for subsamples under and over 50 years of age revealed that (a) negative age–cognition relations were significant for the 18- to 50-year-old sample and (b) the age-related decline accelerated significantly over the adult life span for variables assessing speed, reasoning, and episodic memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
16.
A method to estimate the local partial pressures and temperature during low pressure chemical vapor deposition (LPCVD) proceses using film profile data is demonstrated using the chemistry of blanket tungsten deposition by the hydrogen reduction of tungsten hexafluoride. EVREST, the computer program which performs the estimates, uses EVOLVE, a physically based process simulator for ballistic transport and heterogeneous reactions in features on patterned wafers, to compute film profiles for a given set of deposition conditions. In order to validate the estimation method and to demonstrate EVREST, test calculations are performed using film profiles generated by EVOLVE instead of experimental scanning electron microscopy cross-sections. Calculated films profiles are compared with the generated film profiles (the data) and the simulated deposition conditions are adjusted using an algorithm based on Marquardt's method to minimize the sum of squared differences between points on the calculated and generated profiles. Test calculations confirm that film profiles in more than one feature can be used to improve the reliability of the partial pressure and temperature estimates. 相似文献
17.
The synthesis of new lanthanide allyl complexes of enhanced stability and solubility in saturated hydrocarbons based on silyl-substituted allyl ligands is reported. Thus the potassium salt K(CH2CHCHSiMe3) ( 1 ) reacts with YCl3 in tetrahydrofuran to give the tris-allyl complex Y(CH2CHCHSiMe3)3 ( 2 ), while K(CH2CHCHSiMe2tBu) ( 3 ) affords Y(CH2CHCHSiMe2tBu)3(THF)1.5 ( 4 ). Slow re-crystallization of 4 from light petroleum in the presence of tert-butylcyanide led to multiple insertion to give the sec-amido complex Y{NHC(tBu)(CH)3SiMe2tBu}2{η2-NHC(tBu)CH=CHCH2SiMe2tBu)CH(CHCHSiMe2tBu)CtBuNH}(THF)·(CH3CH(Me)(CH2)2CH3) ( 5 ), which was crystallographically characterized. The reaction of ScCl3(THF)3 with two equivalents of Li{1,3-C3H3(SiMe3)2} in tetrahydrofuran gives the bis-allyl complex {1,3-C3H3(SiMe3)2}2Sc(μ-Cl)2Li(THF)2 ( 6 ), while the analogous reaction of K{1,3-C3H3(SiMe3)2} ( 7 ) with either LaCl3 or YCl3 in tetrahydrofuran affords the bis-allyl complexes MCl{1,3-C3H3(SiMe3)2}2(THF)x (8, M = La, x = 1; 9, M = Y, x = 0). An attempt to prepare the similar neodymium complex gave the mono-allyl complex NdI2{1,3-C3H3(SiMe3)2}(THF)1.25 ( 10 ). The reactions of 8 and 9 with triisobutyl aluminum in benzene-d6 show allyl exchange between lanthanide and aluminum. Complexes 8 , 9 , and 10 have been tested with a variety of activator systems as catalysts for the polymerization of 1,3-butadiene. 相似文献
18.
Carl A. Soderstrom Patricia C. Dischinger Gordon S. Smith J.Richard Hebel David R. McDuff David A. Gorelick Timothy J. Kerns Shiu M. Ho Kathleen M. Read 《Accident; analysis and prevention》1997,29(6):715-721
A structured in-depth interview employing standardized criteria was used to determine the prevalence of lifetime and current alcohol dependence (alcoholism) in unselected consecutive patients admitted to a regional Level I trauma center. Of 629 patients, 157 (25.0%) were current alcoholics at the time of injury. An additional 87 (13.8%) were diagnosed as lifetime non-current alcoholics. There was no significant difference in the rates of current alcohol dependence among patients injured in vehicular crashes (23.5%), other unintentional trauma victims (29.3%), and those injured as a result of violence (24.6%). Of BAC + (blood alcohol concentration positive) patients, 54.5% were current alcoholics. However, 14.4% of alcohol-negative patients were also diagnosed as alcohol dependent. 相似文献
19.
Hugo E. Delgado Ph.D. Ramanath I. Ramakrishnan M.S. Timothy E. Howson D.E.S. 《JOM Journal of the Minerals, Metals and Materials Society》1994,46(9):21-23
Computer-aided engineering tools are routinely used to simulate forging and heat-treatment operations and to perform thermal and stress analyses. This review gives a few examples of the current uses of process modeling tools and outlines some developing capabilities and near-term applications. 相似文献
20.