全文获取类型
收费全文 | 3186篇 |
免费 | 225篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 30篇 |
综合类 | 4篇 |
化学工业 | 753篇 |
金属工艺 | 16篇 |
机械仪表 | 51篇 |
建筑科学 | 132篇 |
矿业工程 | 2篇 |
能源动力 | 70篇 |
轻工业 | 572篇 |
水利工程 | 26篇 |
石油天然气 | 12篇 |
无线电 | 177篇 |
一般工业技术 | 405篇 |
冶金工业 | 847篇 |
原子能技术 | 20篇 |
自动化技术 | 298篇 |
出版年
2024年 | 10篇 |
2023年 | 26篇 |
2022年 | 39篇 |
2021年 | 154篇 |
2020年 | 58篇 |
2019年 | 68篇 |
2018年 | 110篇 |
2017年 | 109篇 |
2016年 | 114篇 |
2015年 | 78篇 |
2014年 | 121篇 |
2013年 | 189篇 |
2012年 | 163篇 |
2011年 | 193篇 |
2010年 | 149篇 |
2009年 | 141篇 |
2008年 | 150篇 |
2007年 | 141篇 |
2006年 | 113篇 |
2005年 | 105篇 |
2004年 | 91篇 |
2003年 | 66篇 |
2002年 | 75篇 |
2001年 | 47篇 |
2000年 | 50篇 |
1999年 | 40篇 |
1998年 | 118篇 |
1997年 | 79篇 |
1996年 | 74篇 |
1995年 | 47篇 |
1994年 | 56篇 |
1993年 | 47篇 |
1992年 | 42篇 |
1991年 | 14篇 |
1990年 | 35篇 |
1989年 | 35篇 |
1988年 | 23篇 |
1987年 | 24篇 |
1986年 | 18篇 |
1985年 | 22篇 |
1984年 | 26篇 |
1983年 | 9篇 |
1982年 | 9篇 |
1981年 | 26篇 |
1980年 | 11篇 |
1979年 | 17篇 |
1978年 | 13篇 |
1977年 | 15篇 |
1976年 | 14篇 |
1975年 | 10篇 |
排序方式: 共有3415条查询结果,搜索用时 31 毫秒
11.
Schmitt Neal; Gleason Sandra E.; Pigozzi Bruce; Marcus Philip M. 《Canadian Metallurgical Quarterly》1987,72(4):622
A total of 438 manufacturing firms reported their business relocation activity, their overall attitude toward the business climate in Michigan, and their assessment of 34 business climate dimensions. Using a lens model paradigm, we explored reasons for a lack of relation between actual relocation decisions and overall business climate attitudes. Location decisions were most highly correlated with distance and labor considerations, whereas overall business climate was most highly correlated with tax considerations, and secondarily correlated with labor problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
12.
13.
In this work a new class of numerical methods for the BGK model of kinetic equations is presented. In principle, schemes of
any order of accuracy in both space and time can be constructed with this technique. The methods proposed are based on an
explicit–implicit time discretization. In particular the convective terms are treated explicitly, while the source terms are
implicit. In this fashion even problems with infinite stiffness can be integrated with relatively large time steps. The conservation
properties of the schemes are investigated. Numerical results are shown for schemes of order 1, 2 and 5 in space, and up to
third-order accurate in time. 相似文献
14.
15.
Estrogen treatment affects the hepatic synthesis and/or secretion of several proteins involved in clinically important pathological processes such as atherosclerosis, hypertension, and thrombosis. The endocrine regulation of the estrogen receptor (ER) concentration in primary cultures of rat hepatocytes was studied. Human growth hormone (hGH) and dexamethasone (DEX) in combination increased ER concentration 6-fold and ER mRNA levels 2.5-fold. These effects were not significantly different from those observed after treatment with the purely somatogenic bovine growth hormone (GH) in combination with DEX. Treatment with the lactogen ovine prolactin in the presence or absence of DEX did not significantly affect ER or ER mRNA concentrations. Triiodothyronine treatment at the most effective concentration (50 nM) increased ER and ER mRNA levels twofold. Medium supplementation with estradiol (0.1 nM) throughout the experiment did not affect the response to treatment with hGH and DEX. Treatment with high concentrations of ethinylestradiol in combination with hGH and DEX, however, increased the ER level twice as much as hGH and DEX without addition of estradiol or ethinylestradiol, whereas the ER mRNA concentration was the same in both the GH+DEX group and GH+ DEX+ (estradiol or ethinylestradiol) groups. These data indicate the importance of GH in combination with glucocorticoids for the maintenance of ER concentrations in the rat liver. Thyroid hormones may be of some, although minor importance, whereas the data suggest that prolactin is not directly involved in hepatic ER regulation. 相似文献
16.
C Held P Hjemdahl N Rehnqvist NH Wallén I Bj?rkander SV Eriksson L Forslund B Wiman 《Canadian Metallurgical Quarterly》1997,95(10):2380-2386
BACKGROUND: Disturbed fibrinolytic function may influence the progression of coronary atherosclerosis and contribute to thrombotic cardiovascular (CV) events. METHODS AND RESULTS: In the Angina Prognosis Study in Stockholm (APSIS), patients with stable angina pectoris were studied prospectively during double-blind treatment with metoprolol or verapamil. Various measures of fibrinolytic function were studied in 631 (of 809) patients. During a median follow-up time of 3.2 years (2132 patient-years), 32 patients suffered a CV death, 21 had a nonfatal myocardial infarction (MI), and 77 underwent revascularization. Plasma levels of tissue plasminogen activator (TPA) activity and antigen (ag), plasminogen activator inhibitor (PAI-1) activity at test, and TPA responses to exercise were determined at baseline and after 1 month's treatment and were related to subsequent fatal and nonfatal CV events. Univariate Cox regression analysis revealed that elevated levels of TPA-ag at rest (P < .05), high PAI-1 activity (P < .05), and low TPA-ag responses to exercise (P < .05) were associated with increased risk of subsequent CV death. After adjustment for baseline risk factors, TPA-ag independently predicted CV death or MI. In addition, PAI-1 activity independently predicted CV death or MI in male patients. Verapamil treatment was associated with a 10% decrease of TPA-ag levels and metoprolol treatment with a 2% increase (P < .001 for treatment difference). CONCLUSIONS: Plasma TPA-ag levels at rest, and among male patients PAI-1 activity as well, independently predict subsequent CV death or MI in patients with stable angina pectoris. 相似文献
17.
Stress in the parenting role has been found to be related to family functioning and parenting behavior. However, most research in this area has been conducted with clinical samples and has not compared parenting stress of mothers and fathers. In this study, 589 married couples with young children (12 to 60 months old) completed the Parenting Stress Index-Short Form (Abidin, 1990) and measures of child-rearing behaviors and attitudes, social support, and child behavior. The validity of Abidin's measure and theoretical model was tested, and results were mixed. Small effects were found for mothers and fathers, and these were moderated by child age and marital happiness. Stress as a normal consequence of parenting is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
18.
S Karacagil A Holmberg A Narbani I Eriksson D Bergqvist 《Canadian Metallurgical Quarterly》1996,12(3):337-341
Faecal samples from asymptomatic dairy cows and calves from a farm on the Island Falster, Denmark, were examined by a sucrose gradient flotation technique. Giardia cysts were found in 7.6% of the 92 samples, and estimated cyst excretion rates ranged from 50-200 cysts per gram faeces. Given that Giardia has the potential to cause clinical disease in cattle and to be transmitted to other animal species and humans, finding the parasite in cattle may be of major epidemiological significance. Future work should focus on elucidating the pathogenicity, transmission patterns and the genetic structure of Giardia populations in cattle in Denmark. 相似文献
19.
Sandra A. Yost Peter H. Bauer Kasyapa Balemarthy 《Multidimensional Systems and Signal Processing》1996,7(2):211-220
This paper addresses the BIBO (bounded-input bounded-output) stability of a class of discrete 2-D quarter-plane filters in the presence of nonessential singularities of the second kind (NSSK's) on the unit bidisk. Conditions under which the double bilinear transformation (DBT) preserves stability are derived. The results presented here also extend the class of systems whose stability can be predicted. Use of the inverse DBT to produce a continuous equivalent of the discrete 2-D transfer function allows easy application of a continuous-domain equivalent of a criterion developed by Dautov. The necessary and sufficient condition for stability derived in this work provides a simple check for the class of systems under consideration. From this class of systems, it is also possible to construct stable pairs of mutually inverse transfer functions. 相似文献
20.
This article describes the application, at the team and individual level, of findings from the positive psychology research. An overview of this research is presented focusing on several areas generally included in the positive psychology domain: flow, appreciative inquiry, the broaden and build theory, and other strategies for increasing the experience of positive emotions and the identification and deployment of strengths. The authors propose that these applications show promise in consulting psychology engagements and may have merit when utilized by practitioners themselves. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献