全文获取类型
收费全文 | 9011篇 |
免费 | 373篇 |
国内免费 | 23篇 |
专业分类
电工技术 | 89篇 |
综合类 | 37篇 |
化学工业 | 2190篇 |
金属工艺 | 151篇 |
机械仪表 | 164篇 |
建筑科学 | 483篇 |
矿业工程 | 14篇 |
能源动力 | 281篇 |
轻工业 | 676篇 |
水利工程 | 59篇 |
石油天然气 | 33篇 |
无线电 | 688篇 |
一般工业技术 | 1811篇 |
冶金工业 | 1150篇 |
原子能技术 | 71篇 |
自动化技术 | 1510篇 |
出版年
2023年 | 95篇 |
2022年 | 170篇 |
2021年 | 253篇 |
2020年 | 172篇 |
2019年 | 234篇 |
2018年 | 261篇 |
2017年 | 186篇 |
2016年 | 246篇 |
2015年 | 219篇 |
2014年 | 292篇 |
2013年 | 509篇 |
2012年 | 477篇 |
2011年 | 546篇 |
2010年 | 404篇 |
2009年 | 421篇 |
2008年 | 437篇 |
2007年 | 423篇 |
2006年 | 335篇 |
2005年 | 322篇 |
2004年 | 269篇 |
2003年 | 243篇 |
2002年 | 214篇 |
2001年 | 146篇 |
2000年 | 157篇 |
1999年 | 144篇 |
1998年 | 312篇 |
1997年 | 220篇 |
1996年 | 139篇 |
1995年 | 161篇 |
1994年 | 128篇 |
1993年 | 105篇 |
1992年 | 100篇 |
1991年 | 91篇 |
1990年 | 58篇 |
1989年 | 63篇 |
1988年 | 71篇 |
1987年 | 67篇 |
1986年 | 44篇 |
1985年 | 54篇 |
1984年 | 52篇 |
1983年 | 32篇 |
1982年 | 37篇 |
1981年 | 53篇 |
1980年 | 40篇 |
1979年 | 41篇 |
1978年 | 34篇 |
1977年 | 42篇 |
1976年 | 73篇 |
1975年 | 32篇 |
1974年 | 24篇 |
排序方式: 共有9407条查询结果,搜索用时 15 毫秒
21.
22.
23.
S Ewig A Glasmacher B Ulrich K Wilhelm H Sch?fer KH Nachtsheim 《Canadian Metallurgical Quarterly》1998,114(2):444-451
STUDY OBJECTIVE: To determine predictors of mortality from pulmonary infiltrates in neutropenic patients with acute leukemia during chemotherapy, and the significance of those factors related to the underlying malignancy and its therapy as well as of those related to the severity of the illness associated with pulmonary infiltrates. DESIGN: A historical cohort study. SETTING: A university teaching hospital and tertiary referral center. PATIENTS AND METHODS: Overall, 53 patients with neutropenia during chemotherapy and with first episodes of pulmonary infiltrates during a 4-year period were studied. Prognostic analysis included 38 variables. Multivariate analyses were performed by logistic regression. RESULTS: The survival rate from pneumonia was 57% (30/53). The following eight parameters were significantly associated with death in univariate analysis: comorbidity present; development of "late" pulmonary infiltrates (> or = 14 days after hospital admission); heart rate > or = 100 beats/min; a ratio heart rate/systolic blood pressure (HR/SBP) > or = 1.2; urea nitrogen > 7 mmol/L; radiographic score > or = 3; neutropenia < 1.0x10(9)/L at the treatment end point; and failed complete remission. In a multivariate model including only parameters available at diagnosis of pulmonary infiltrates, the presence of a ratio HR/SBP > or = 1.2 and of a radiographic score > or = 3 remained independently associated with death. In a second model also including the evolutionary parameter neutropenia < or = 1.0x10(9)/L at the treatment end point, both parameters remained significant together with neutropenia <1.0x 10(9)/L at the treatment end point. The presence of a ratio HR/SBP > or = 1.2 was a strong marker of early death. CONCLUSION: Both therapy- and malignancy-associated neutropenia as well as the severity of illness associated with pulmonary infiltrates are independent prognostic factors. Patients with a ratio HR/SBP > or = 1.2 at diagnosis of pulmonary infiltrates suffer from potentially reversible acute illness, are at risk for early death and, therefore, may be appropriate candidates for treatment in an ICU. 相似文献
24.
Ulrich Schmatz Catherine Dubourdieu Oleg Lebedev Gerard Delabouglise Francois Weiss Jean-Pierre Senateur 《Journal of Low Temperature Physics》1996,105(5-6):1301-1306
Thin and thick YBCO Films have been grown by Aerosol Assisted as well as by thermal MOCVD. The Aerosol Assisted MOCVD technique allows the growth of YBCO films from a single liquid source at deposition rates of up to 10m/h.Transport measurements (I-V) on etched microbridges using a single pulse technique have been performed. The angular magnetic field dependence Jc() of the critical current density from Tc down to 50 K has been measured. Transport properties are reported and discussed with respect to the microstructural features as determined by X-ray diffraction and electron microscopy. 相似文献
25.
One approach to limiting disclosure risk in public-use microdata is to release multiply-imputed, partially synthetic data sets. These are data on actual respondents, but with confidential data replaced by multiply-imputed synthetic values. A mis-specified imputation model can invalidate inferences based on the partially synthetic data, because the imputation model determines the distribution of synthetic values. We present a practical method to generate synthetic values when the imputer has only limited information about the true data generating process. We combine a simple imputation model (such as regression) with density-based transformations that preserve the distribution of the confidential data, up to sampling error, on specified subdomains. We demonstrate through simulations and a large scale application that our approach preserves important statistical properties of the confidential data, including higher moments, with low disclosure risk. 相似文献
26.
André Twele Wenxi Cao Simon Plank Sandro Martinis 《International journal of remote sensing》2016,37(13):2990-3004
This article presents an automated Sentinel-1-based processing chain designed for flood detection and monitoring in near-real-time (NRT). Since no user intervention is required at any stage of the flood mapping procedure, the processing chain allows deriving time-critical disaster information in less than 45 min after a new data set is available on the Sentinel Data Hub of the European Space Agency (ESA). Due to the systematic acquisition strategy and high repetition rate of Sentinel-1, the processing chain can be set up as a web-based service that regularly informs users about the current flood conditions in a given area of interest. The thematic accuracy of the thematic processor has been assessed for two test sites of a flood situation at the border between Greece and Turkey with encouraging overall accuracies between 94.0% and 96.1% and Cohen’s kappa coefficients (κ) ranging from 0.879 to 0.910. The accuracy assessment, which was performed separately for the standard polarizations (VV/VH) of the interferometric wide swath (IW) mode of Sentinel-1, further indicates that under calm wind conditions, slightly higher thematic accuracies can be achieved by using VV instead of VH polarization data. 相似文献
27.
28.
Ulrich Schoch Jürg Lüthy und Christian Schlatter 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1984,178(5):351-355
Zusammenfassung In Rohextrakten von 18Penicillium camemberti- und 6P. roqueforti-Stämmen, die als Reifungsorganismen bei der Schimmelkäseproduktion in Schweizer Käsereien eingesetzt werden, wurde das mutagene Potential mit Hilfe des Ames-Testes bestimmt. In keinem der geprüften Extrakte konnte eine mutagene Aktivität festgestellt werden. Roquefortin, ein in Blauschimmelkäsen nachweisbares Mykotoxin vonP. roqueforti, erwies sich im Ames-Test als nicht mutagen. Die ermittelten Resultate ergaben keine Anhaltspunkte für genotoxische Effekte durch die Konsumation von schimmelgereiftem Käse.
Auszug aus der Dissertation von U. Schoch, Mykotoxine in schimmelgereiften Käsen, Diss. ETH Nr. 7278, ETH Zürich, 1983 相似文献
Mutagenicity testing of commercialP. Camemberti- andP. roqueforti-strains
Summary We tested the mutagenic potential of crude extracts of 18 strains ofPenicillium camemberti- and 6 strains ofP. roqueforti, which are used commercially in the production of mould ripened cheese in Switzerland. No mutagenic activity could be detected in any of the extracts. Roquefortine, a mycotoxin ofP. roqueforti, often found in Blue cheese, was negative in the Amestest. The results obtained do not lead reasons for experting undesired long term effects from the consumption of mould ripened cheese.
Auszug aus der Dissertation von U. Schoch, Mykotoxine in schimmelgereiften Käsen, Diss. ETH Nr. 7278, ETH Zürich, 1983 相似文献
29.
30.
The lead free Sn–Ag–y%Cu (y = 0.0, 0.5, 1.0 and 2.0) interconnect interfacial microstructures and the microstructure evolution under thermal treatment (isothermal aging, 150 °C/1000 h) were studied in detail by using surface microetching microscopy and cross section microscopy. The corresponding mechanical and reliability behaviors were evaluated by performing shear test and fracture mode analysis before and after the thermal treatment. The results indicate: (i) The interconnects could have different microstructures and intermetallic compound (IMC), depending on the Cu content. The Cu–Sn IMC could have microstructures that were clusters or protrusion-like, Augustine grass leaf-like, scissor-like, tweezers-like, etc. (ii) Ag3Sn IMCs were not observed at time zero for any interconnect groups, but they occurred after the aging for all groups. The Ag3Sn IMC could have different microstructures, again depending on Cu content. For low Cu content, the Ag3Sn IMCs were granules or nodules; for higher Cu content, Ag3Sn IMCs were plate-like. (iii) The growth of Ag3Sn plates was promoted by the growth of Cu–Sn IMCs, but indirectly linked to the Cu content. (iv) High Cu content (1.0 wt% and higher) could degrade the mechanical and reliability performances of the LF interconnect by providing a brittle joint, which was mainly achieved through the substantial growth of Cu–Sn IMCs and Ag3Sn plates. 相似文献