全文获取类型
收费全文 | 3388篇 |
免费 | 49篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 12篇 |
综合类 | 6篇 |
化学工业 | 140篇 |
金属工艺 | 8篇 |
机械仪表 | 9篇 |
建筑科学 | 16篇 |
能源动力 | 41篇 |
轻工业 | 94篇 |
水利工程 | 2篇 |
石油天然气 | 1篇 |
无线电 | 60篇 |
一般工业技术 | 87篇 |
冶金工业 | 2770篇 |
原子能技术 | 4篇 |
自动化技术 | 189篇 |
出版年
2024年 | 2篇 |
2023年 | 11篇 |
2022年 | 12篇 |
2021年 | 25篇 |
2020年 | 19篇 |
2019年 | 20篇 |
2018年 | 27篇 |
2017年 | 18篇 |
2016年 | 18篇 |
2015年 | 20篇 |
2014年 | 31篇 |
2013年 | 59篇 |
2012年 | 33篇 |
2011年 | 52篇 |
2010年 | 32篇 |
2009年 | 32篇 |
2008年 | 23篇 |
2007年 | 25篇 |
2006年 | 23篇 |
2005年 | 16篇 |
2004年 | 22篇 |
2003年 | 24篇 |
2002年 | 20篇 |
2001年 | 14篇 |
2000年 | 16篇 |
1999年 | 114篇 |
1998年 | 915篇 |
1997年 | 523篇 |
1996年 | 346篇 |
1995年 | 175篇 |
1994年 | 151篇 |
1993年 | 192篇 |
1992年 | 18篇 |
1991年 | 26篇 |
1990年 | 27篇 |
1989年 | 34篇 |
1988年 | 21篇 |
1987年 | 23篇 |
1986年 | 22篇 |
1985年 | 32篇 |
1984年 | 3篇 |
1983年 | 4篇 |
1982年 | 15篇 |
1981年 | 10篇 |
1980年 | 30篇 |
1978年 | 6篇 |
1977年 | 51篇 |
1976年 | 101篇 |
1975年 | 2篇 |
1973年 | 2篇 |
排序方式: 共有3439条查询结果,搜索用时 15 毫秒
41.
42.
43.
44.
Recent research has found that family caregivers do not discuss their caregiving in terms of tasks but instead describe their care as shaped by concerns, commitments and goals. The purpose of this paper is to challenge the ways in which nurses approach the family caregiving process and to explore possibilities for evolving nursing knowledge by questioning existing practice in the light of developing insight into the ways in which being a family caregiver is meaningful. A critique of the philosophical orientations of rationalism and empiricism provides a platform to discuss the merits of a Heideggerian phenomenological approach in assisting nurses to better understand family caring experience. Such critique serves to support the notion of displacing the traditional scientific view as the prime means of disclosing truth, acknowledging alternative ways of knowing. 相似文献
45.
Hemodynamics and left ventricular myocardial contractility in 170 patients who underwent surgery of prostatic adenoma were examined in preoperative period and 16 days after single-stage transvesical adenomectomy. The age of the patients varied from 52 to 85 years. Echocardiography and the dilution method were used for the evaluation. The increase of end-diastolic and end-systolic volumes, stroke volume, cardiac index, was registered. The combined pharmacological treatment made it possible to decrease the number of operative and postoperative cardiovascular complications. 相似文献
46.
J Moreno Sierra ML Maestro de las Casas J Chicharro Almarza MD Ortega Heredia J López García-Asenjo C Merino Sánchez E Blanco Jiménez A Silmi Moyano L Rsesel Estévez 《Canadian Metallurgical Quarterly》1997,50(8):855-866
OBJECTIVE: The clinical course of transitional cell carcinoma of the bladder can be difficult to predict due to its potential to invade the muscle layer and/or develop to a high grade lesion. Bladder carcinoma can arise from genetic changes that may activate the oncogenes (-c-erbB2, c-erbB1, c-myc, ras, etc.) and/or inactivate the suppressor genes (p53, Rb). The aim of the present study is to continue a study protocol on the molecular biology of bladder tumors. METHODS/RESULTS: From January, 1993 to January, 1995, 85 patients were studied. These patients were divided into two groups: the first group comprised 14 controls of urothelial tissue and the second comprised 65 cases of transitional cell carcinoma of the bladder. p53 expression was determined by an immunohistochemical method (NCL-p53-DO7 monoclonal antibody). Quantification of the p8 oncoprotein in cytosol and EGFR (epidermal growth factor receptor) in membrane was performed by ELISA (Oncogene Science) and RIA (Vienna Lab), respectively. A statistically significant relationship between the expression of p53 and EGFR with tumor stage and grade was found. Quantification of p185 and EGFR showed higher values in the tumor tissue than in the control samples, but a worse survival could not be determined. CONCLUSIONS: The present study shows that p53 expression can be considered to be a prognostic factor. It provides useful information on the aggressive behaviour of the tumor and has a direct relation with the survival rates. 相似文献
47.
Protein kinase C (PKC) isoforms are altered in colon tumors and upon exposure of intestinal mucosa to nutrients. We evaluated the effects of the PKC inhibitors staurosporine and calphostin C on human Caco-2 intestinal epithelial proliferation, motility, and differentiation. Motility was quantitated by monolayer expansion and the brush border enzymes dipeptidyl dipeptidase (DPDD) and alkaline phosphatase (AP) by synthetic substrate digestion. Staurosporine (0.03-1.0 ng/ml) and calphostin C (10(-12) M-10(-4) M) dose-dependently inhibited monolayer expansion and AP but stimulated DPDD. Proliferation was also inhibited but the effects of each inhibitor on motility, AP, and DPDD were preserved after mitomycin C proliferative blockade, suggesting that these effects were proliferation-independent. PKC inhibitors independently inhibit motility, AP and proliferation in human intestinal Caco-2 epithelial cells, but selectively stimulate the small intestinal differentiation marker DPDD. PKC may regulate small intestinal epithelial differentiation. 相似文献
48.
49.
50.
Cooking reduces odor intensity in boar meat but also may induce lipid oxidation unless the meat pH is above approximately 6.0. This research was designed to determine the feasibility of cooking boar meat in the prerigor state to overcome boar odor and lipid oxidation problems. Prerigor and postrigor triceps brachii muscle samples from 40 boars (20 Duroc and 20 Yorkshire) were cooked to 60 degrees C, frozen and stored at -20 degrees C, reheated in a 60 degrees C water bath for 1 h, and then subjected to pH, thiobarbituric acid (TBA), and sensory analyses. Boar odor intensity and skatole concentration in backfat samples were determined by olfactory test and HPLC, respectively. Cooked (initial cooking) prerigor meat was found to have higher (P < .05) pH and lower (P < .05) TBA values than comparable postrigor meat (6.44 vs 6.09 and 2.15 vs 3.23, respectively). Regression analysis indicated an inverse relationship between pH and TBA values (r = -.52; P < .01). No appreciable changes in TBA values were noted after frozen storage for 14 to 98 d, but reheating increased TBA values (P < .05) in both prerigor and postrigor samples (3.45 vs 4.32, respectively). Sensory evaluation scores indicated that prerigor cooked meat was less tender with more pronounced rancid flavor than postrigor cooked meat (P < .05), but panelists may have allowed the toughness of the prerigor samples to adversely affect their flavor scores. No difference in boar odor was detected between rigor states or breeds. Mean skatole concentration in backfat was .12 micrograms/g and no difference was detected between breeds.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献