全文获取类型
收费全文 | 1438篇 |
免费 | 15篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 21篇 |
化学工业 | 206篇 |
金属工艺 | 34篇 |
机械仪表 | 23篇 |
建筑科学 | 49篇 |
矿业工程 | 2篇 |
能源动力 | 83篇 |
轻工业 | 97篇 |
水利工程 | 4篇 |
石油天然气 | 4篇 |
无线电 | 159篇 |
一般工业技术 | 224篇 |
冶金工业 | 429篇 |
原子能技术 | 16篇 |
自动化技术 | 104篇 |
出版年
2023年 | 7篇 |
2022年 | 13篇 |
2021年 | 17篇 |
2020年 | 5篇 |
2019年 | 16篇 |
2018年 | 8篇 |
2017年 | 12篇 |
2016年 | 19篇 |
2015年 | 9篇 |
2014年 | 26篇 |
2013年 | 40篇 |
2012年 | 34篇 |
2011年 | 60篇 |
2010年 | 23篇 |
2009年 | 55篇 |
2008年 | 47篇 |
2007年 | 55篇 |
2006年 | 52篇 |
2005年 | 51篇 |
2004年 | 53篇 |
2003年 | 45篇 |
2002年 | 42篇 |
2001年 | 39篇 |
2000年 | 36篇 |
1999年 | 33篇 |
1998年 | 141篇 |
1997年 | 75篇 |
1996年 | 85篇 |
1995年 | 30篇 |
1994年 | 49篇 |
1993年 | 22篇 |
1992年 | 18篇 |
1991年 | 20篇 |
1990年 | 18篇 |
1989年 | 20篇 |
1988年 | 15篇 |
1987年 | 12篇 |
1986年 | 8篇 |
1985年 | 18篇 |
1984年 | 9篇 |
1983年 | 11篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1980年 | 8篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1977年 | 13篇 |
1976年 | 27篇 |
1975年 | 6篇 |
1970年 | 4篇 |
排序方式: 共有1455条查询结果,搜索用时 15 毫秒
1.
Raffael Ott Xenia Pawlow Andreas Weiß Anna Hofelich Melanie Herbst Nadine Hummel Cornelia Prehn Jerzy Adamski Werner Rmisch-Margl Gabi Kastenmüller Anette-G. Ziegler Sandra Hummel 《International journal of molecular sciences》2020,21(24)
Shared metabolomic patterns at delivery have been suggested to underlie the mother-to-child transmission of adverse metabolic health. This study aimed to investigate whether mothers with gestational diabetes mellitus (GDM) and their offspring show similar metabolomic patterns several years postpartum. Targeted metabolomics (including 137 metabolites) was performed in plasma samples obtained during an oral glucose tolerance test from 48 mothers with GDM and their offspring at a cross-sectional study visit 8 years after delivery. Partial Pearson’s correlations between the area under the curve (AUC) of maternal and offspring metabolites were calculated, yielding so-called Gaussian graphical models. Spearman’s correlations were applied to investigate correlations of body mass index (BMI), Matsuda insulin sensitivity index (ISI-M), dietary intake, and physical activity between generations, and correlations of metabolite AUCs with lifestyle variables. This study revealed that BMI, ISI-M, and the AUC of six metabolites (carnitine, taurine, proline, SM(-OH) C14:1, creatinine, and PC ae C34:3) were significantly correlated between mothers and offspring several years postpartum. Intergenerational metabolite correlations were independent of shared BMI, ISI-M, age, sex, and all other metabolites. Furthermore, creatinine was correlated with physical activity in mothers. This study suggests that there is long-term metabolic programming in the offspring of mothers with GDM and informs us about targets that could be addressed by future intervention studies. 相似文献
2.
A comparison between different PMD compensation techniques 总被引:17,自引:0,他引:17
Sunnerud H. Chongjin Xie Karlsson M. Samuelsson R. Andrekson P.A. 《Lightwave Technology, Journal of》2002,20(3):368-378
We quantify the benefits of using different techniques for compensation of polarization mode dispersion (PMD) in fiber-optic communication systems by means of numerical simulations. This is done both with respect to PMD-induced pulse broadening and in terms of system outage probability for different data formats [nonreturn-to-zero (NRZ) and return-to-zero (RZ)]. Attention is focused on simple and relevant single- and double-stage post-transmission compensators with a few degrees of freedom (DOF). It is generally believed that a PMD compensator with a polarization controller and a variable delay line can only compensate the PMD to the first order. We show, from analytical results, the counterintuitive fact that this scheme can also partially compensate for higher order PMD. We also investigate the benefit of using a polarizer as compensation element where the optical average power can be used as a feedback signal 相似文献
3.
4.
AM De Mattos MA Head J Everett J Hosenpud R Hershberger A Cobanoglu G Ott R Ratkovec DJ Norman 《Canadian Metallurgical Quarterly》1994,57(4):626-630
To determine if cardiac allograft outcome is improved among patients with fewer HLA-DR mismatches with their donors, we studied 132 recipients of a primary cardiac allograft who were transplanted between December 1985 and December 1991. These recipients and their donors all had high-confidence-level serological HLA-DR typing, previously shown to correlate highly with DNA DR typing. Patients were divided in two groups based on the HLA-DR mismatch with their donors. Group I consisted of 78 patients with 1 or zero DR mismatch and group II of 54 patients with 2 DR mismatches. Allograft outcome measurements included incidence of moderate rejection, incidence of allograft vasculopathy at 12 months, cardiac function measured as left ventricular ejection fraction (LVEF) and cardiac index (CI), and actuarial graft survival up to 7 years. Groups I and group II were not different with regard to recipient age, donor age, ischemia time, pulmonary vascular resistance, sex, or PRA greater than 0%. Group II had a higher incidence of moderate rejection on the first-week biopsy (47% vs. 25%, P = 0.019), and during the first month (84% vs. 58%, P = 0.006), but no difference was found in frequency of rejection from months 2 to 12. LVEF was not different in the groups at any point. CI was better in group I at 12 months (2.76 vs. 2.5, P = 0.03). No statistically significant difference was found in incidence of allograft vasculopathy (17% vs. 26%, P = 0.204). Actual graft survival at 1 year was better for group I (91% vs. 74%, P = 0.008), and actuarial graft survival at 6 years also favored group I (76% vs. 56%, P = 0.04). Using high-confidence-level serological HLA-DR typing assignments we demonstrated that HLA-DR mismatching correlates highly with cardiac allograft outcome. Implications are that heart transplant survival could be improved if prospective matching were feasible and prioritized or if immunosuppression were tailored to the HLA-DR match. 相似文献
5.
Dr. V. Recina Dr. D. Lundström B. Karlsson 《Metallurgical and Materials Transactions A》2002,33(9):2869-2881
The influence of chemical composition on the microstructure of the γ-titanium aluminide alloy Ti-48Al-2W-0.5Si (at. pct) and the accompanying tensile, low-cycle fatigue, and creep properties
has been evaluated. The study showed that small variations in chemical composition and casting procedures resulted in considerable
variations in the microstructure, yielding vastly different mechanical properties. Low contents of aluminum and tungsten led
to a coarse-grained lamellar (γ/α
2) microstructure with high creep resistance. A composition close to the nominal one produced a duplex (γ+γ/α
2) structure with favorable strength, ductility, and low-cycle fatigue properties. By controlling the solidification and cooling
rates at casting, a pseudoduplex (PS-DP) microstructure with a unique combination of high strength and high fatigue and creep
resistance can be obtained. These unique properties can be explained by the diffuse boundaries between the relatively small
γ grains and the neighboring lamellar colonies, combined with semicoherent interfaces between the γ and α
2 phases. At tensile and low-cycle fatigue loading, these boundaries act like high-angle boundaries, producing a virtually
fine-grained material promoting strength, whereas at creep loading, grain-boundary sliding is hindered in the semicoherent
interfaces leading to high creep resistance. 相似文献
6.
7.
8.
The most recent attempts in raising Tc of cuprate superconductors were successful by synthesizing new Hg-based cuprate materials. We discuss some properties of materials from this series with varying numbers of Cu-O planes per unit cell, including the considerable rise of the critical temperature under the influence of external pressure.In the second part of this contribution, various attempts to directly determine the symmetry of the superconducting order parameter of high-Tc cuprates are mentioned and set into perspective. The experimental approaches are all based on probing the phase of the order parameter in suitably connected closed superconducting loops. The evidence for unconventional order-parameter symmetry in these materials is growing. 相似文献
9.
Multilayer calculations by conventional matrix methods for dielectricum/noble metal/dielectricum systems on glass have been performed. The aim has been to maximize the integrated parameters for solar transmission, Tsol, and transmission of visible light, Teye We have found that Ag is superior for maximizing the transmittance over the narrow visible wavelength range owing to the low internal absorptance. When solar energy transmission is considered multilayers based on Au are the best choice for metal film thicknesses above 15 nm. For thinner films, Ag is still to be preferred. 相似文献
10.