全文获取类型
收费全文 | 20109篇 |
免费 | 702篇 |
国内免费 | 21篇 |
专业分类
电工技术 | 215篇 |
综合类 | 18篇 |
化学工业 | 3767篇 |
金属工艺 | 322篇 |
机械仪表 | 403篇 |
建筑科学 | 1005篇 |
矿业工程 | 49篇 |
能源动力 | 501篇 |
轻工业 | 1677篇 |
水利工程 | 120篇 |
石油天然气 | 57篇 |
武器工业 | 1篇 |
无线电 | 1584篇 |
一般工业技术 | 3054篇 |
冶金工业 | 5027篇 |
原子能技术 | 188篇 |
自动化技术 | 2844篇 |
出版年
2023年 | 157篇 |
2022年 | 296篇 |
2021年 | 460篇 |
2020年 | 341篇 |
2019年 | 365篇 |
2018年 | 424篇 |
2017年 | 389篇 |
2016年 | 491篇 |
2015年 | 424篇 |
2014年 | 520篇 |
2013年 | 1074篇 |
2012年 | 856篇 |
2011年 | 1116篇 |
2010年 | 765篇 |
2009年 | 821篇 |
2008年 | 861篇 |
2007年 | 758篇 |
2006年 | 701篇 |
2005年 | 590篇 |
2004年 | 485篇 |
2003年 | 439篇 |
2002年 | 420篇 |
2001年 | 295篇 |
2000年 | 317篇 |
1999年 | 426篇 |
1998年 | 1378篇 |
1997年 | 826篇 |
1996年 | 616篇 |
1995年 | 426篇 |
1994年 | 380篇 |
1993年 | 374篇 |
1992年 | 197篇 |
1991年 | 168篇 |
1990年 | 148篇 |
1989年 | 156篇 |
1988年 | 144篇 |
1987年 | 139篇 |
1986年 | 132篇 |
1985年 | 157篇 |
1984年 | 132篇 |
1983年 | 119篇 |
1982年 | 96篇 |
1981年 | 115篇 |
1980年 | 98篇 |
1979年 | 97篇 |
1978年 | 91篇 |
1977年 | 176篇 |
1976年 | 228篇 |
1975年 | 82篇 |
1974年 | 72篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Modellierung in der Lehre an Hochschulen: Thesen und Erfahrungen 总被引:1,自引:1,他引:0
Martin Glinz 《Informatik-Spektrum》2008,31(5):425-434
Zusammenfassung Nicht erst seit Modellierung zum Modewort geworden ist, ist Modellierung ein wichtiges Thema in der Informatikausbildung.
Dieser Beitrag beleuchtet in zw?lf Thesen das Warum, Was, Wie viel, Wo, Wann und Wie von Modellierung in der Lehre im Rahmen
informatikbezogener Studieng?nge. Die Thesen basieren auf der Erfahrung des Verfassers mit einer seit über zehn Jahren gehaltenen
Modellierungsvorlesung an der Universit?t Zürich sowie dem Gedankenaustausch mit anderen Hochschullehrerinnen und -lehrern
im Rahmen der GI-Workshopreihe ,,Modellierung“. Zus?tzlich liefert eine Befragung von Absolventinnen und Absolventen an der
Universit?t Zürich empirische Evidenz für eine Reihe der Thesen. 相似文献
102.
Fabrice Martin Marc-Etienne Jan Samuel Rey-Mermet Brahim Belgacem Dong Su Marco Cantoni Paul Muralt 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2006,53(7):1339-1343
Polycrystalline A1N thin films were deposited by RF reactive magnetron sputtering on Pt(111)/Ti electrode films. The substrates were tilted by an angle ranging from 40 degrees to 70 degrees with respect to the target normal. A low deposition temperature and a high sputter gas pressure were found ideal for tilted growth. The resulting grain tilt angle amounts to about half the substrate tilt angle. For coupling evaluation, 5 GHz solidly mounted resonator structures have been realized. The tilted grain A1N films exhibited a permittivity in the 9.5-10.5 range and loss tangent of 0.3%. Two shear modes as well as the longitudinal mode could be clearly identified. The coupling coefficient k2(eff) of the fundamental thickness shear mode (TS0) was found to be about 0.5%, which is compatible with a c-axis tilt of about 6 degrees. 相似文献
103.
Problems that arise from health-care management, rather than from a disease process, are now recognized as making a substantial contribution to patient morbidity and mortality and to the cost of health care. However, most classifications of these problems do not provide sufficient detail to allow comparisons or to develop better strategies for the prevention, detection and management of these problems. A 'Generic Occurrence Classification' was developed to record their salient features, place them in context and elicit any system or human error-based contributing factors. This was done by an iterative process in which 'natural categories', identified from over 2000 incidents and 800 adverse events, were placed in a hierarchical structure created using software written in Microsoft Visual Basic; data were stored in a Microsoft Access database. This was shown to be a valid and reliable way to compare incidents and accidents from different sources and to allow sufficient detail to be retrieved to develop preventive strategies. 相似文献
104.
105.
106.
Summary We introduce a very simple model for thermally activated atomic migration on a lattice, and several techniques to handle it. For thermodynamical systems, the model can be used for simulating decomposition paths taking into account relevant metallurgical features. Close to equilibrium, the simplest mean-field approximation of the model can be linearized with respect to the departure from equilibrium; one then gets a microscopic interpretation of classical phenomenological coefficients, such as mobility, interfacial transfer coefficient, rate constants for the coupled relaxation of concentration and order fields. Further away from the equilibrium, the nonlinearities can be taken into account in a consistent way. For driven alloys, i.e. alloys submitted to external forcing, forced atomic migration is added to the model and new features emerge: the model is supported by several experimental results some of which confirmed its predictions a posteriori. 相似文献
107.
In farm animals as in human, reproduction is affected by changes in the level of energetic balance. The main factors that link metabolism and reproduction, like insulin, IGFs, glucose, FFA, leptin and NPY, act on hypothalamo-pituitary axis as well as on gonads by directly altering gametogenesis. 相似文献
108.
Communication between patients with breast cancer and health care providers. Determinants and implications 总被引:1,自引:0,他引:1
C Lerman M Daly WP Walsh N Resch J Seay A Barsevick L Birenbaum T Heggan G Martin 《Canadian Metallurgical Quarterly》1993,72(9):2612-2620
BACKGROUND: This study evaluated the perceptions of patients with breast cancer of their medical interactions with providers. The determinants and psychological consequences of communication problems also were examined. METHODS: Ninety-seven patients with Stage I or II breast cancer completed a set of validated questionnaires before initiating postoperative therapy. Data on psychological distress were collected at baseline and 3-month follow-up, and multivariate models were fit to explain the relationship between pretreatment communication problems and subsequent psychological distress. Data on clinical variables were abstracted from medical records. RESULTS: A substantial proportion of patients (84%) reported difficulties communicating with the medical team. Communication problems were more common among patients who were less optimistic about their disease and had less assertive coping styles. Patient-reported communication problems were associated with increased anxiety, depression anger, and confusion at the 3-month follow-up. The association between communication problems and mood disturbance remained significant, although small, after adjusting for baseline mood disturbance, demographic, clinical, and coping style variables. CONCLUSION: Interventions that enhance communication between patients with breast cancer and their providers may improve patients' psychological adjustment to treatment. Conversely, interventions that lower distress and modify coping style may enhance communication. 相似文献
109.
EJ Amella 《Canadian Metallurgical Quarterly》1998,19(5):269-74; quiz 275
Adequate nutritional intake is critical to preserving the health of older people. When an elderly person requires assistance with eating, the most social of all activities of daily living, the assessment of nutritional issues becomes multidimensional and interdisciplinary. Management strategies should involve the professional nurse's attention to dietary needs, as well as the social, cultural, and interactive components of mealtime. Additionally, special strategies need to be developed for people with cognitive and physical disabilities. 相似文献
110.
CB Granger J Hirsch RM Califf J Col HD White A Betriu LH Woodlief KL Lee EG Bovill RJ Simes EJ Topol 《Canadian Metallurgical Quarterly》1996,93(5):870-878
BACKGROUND: Although intravenous heparin is commonly used after thrombolytic therapy, few reports have addressed the relationship between the degree of anticoagulation and clinical outcomes. We examined the activated partial thromboplastin time (aPTT) in 29,656 patients in the Global Utilization of Streptokinase and t-PA for Occluded Coronary Arteries (GUSTO-I) trial and analyzed the relationship between the aPTT and both baseline patient characteristics and clinical outcomes. METHODS AND RESULTS: Intravenous heparin was administered as a 5000-U bolus followed by an initial infusion of 1000 U/h, with dose adjustment to achieve a target aPTT of 60 to 85 seconds. aPTTs were collected 6, 12, and 24 hours after thrombolytic administration. Higher aPTT at 24 hours was strongly related to lower patient weight (P < .00001) as well as older age, female sex, and lack of cigarette smoking (all PT< .0001). At 12 hours, the aPTT associated with the lowest 30-day mortality, stroke, and bleeding rates was 50 to 70 seconds. There was an unexpected direct relationship between the aPTT and the risk of subsequent reinfarction. There was a clustering of reinfarction in the first 10 hours after discontinuation of intravenous heparin. CONCLUSIONS: Although the relationship between aPTT and clinical outcome was confounded to some degree by the influence of baseline prognostic characteristics, aPTTs higher than 70 seconds were found to be associated with higher likelihood of mortality, stroke, bleeding, and reinfarction. These findings suggest that until proven otherwise, we should consider the aPTT range of 50 to 70 seconds as optimal with intravenous heparin after thrombolytic therapy. 相似文献