全文获取类型
收费全文 | 1735篇 |
免费 | 48篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 35篇 |
综合类 | 1篇 |
化学工业 | 297篇 |
金属工艺 | 72篇 |
机械仪表 | 17篇 |
建筑科学 | 53篇 |
矿业工程 | 2篇 |
能源动力 | 42篇 |
轻工业 | 114篇 |
水利工程 | 17篇 |
石油天然气 | 2篇 |
无线电 | 185篇 |
一般工业技术 | 246篇 |
冶金工业 | 475篇 |
原子能技术 | 12篇 |
自动化技术 | 217篇 |
出版年
2023年 | 15篇 |
2022年 | 27篇 |
2021年 | 47篇 |
2020年 | 34篇 |
2019年 | 35篇 |
2018年 | 36篇 |
2017年 | 43篇 |
2016年 | 34篇 |
2015年 | 25篇 |
2014年 | 36篇 |
2013年 | 76篇 |
2012年 | 63篇 |
2011年 | 67篇 |
2010年 | 56篇 |
2009年 | 58篇 |
2008年 | 80篇 |
2007年 | 54篇 |
2006年 | 39篇 |
2005年 | 44篇 |
2004年 | 40篇 |
2003年 | 34篇 |
2002年 | 30篇 |
2001年 | 27篇 |
2000年 | 24篇 |
1999年 | 34篇 |
1998年 | 127篇 |
1997年 | 85篇 |
1996年 | 42篇 |
1995年 | 44篇 |
1994年 | 27篇 |
1993年 | 35篇 |
1992年 | 12篇 |
1991年 | 21篇 |
1990年 | 18篇 |
1989年 | 11篇 |
1987年 | 17篇 |
1986年 | 14篇 |
1985年 | 11篇 |
1984年 | 14篇 |
1983年 | 15篇 |
1982年 | 10篇 |
1981年 | 14篇 |
1980年 | 12篇 |
1979年 | 11篇 |
1978年 | 12篇 |
1977年 | 20篇 |
1976年 | 38篇 |
1975年 | 9篇 |
1974年 | 15篇 |
1973年 | 10篇 |
排序方式: 共有1787条查询结果,搜索用时 15 毫秒
111.
RD Jordan 《Canadian Metallurgical Quarterly》1987,36(12):3604-3613
112.
A simple, compact transresistor is introduced. Simulations show its linearity properties are attractive when compared to some of the best transresistors reported in the literature. Experimental results from a single-ended structure indicate a linearity deviation bound by ±0.35% over a voltage swing of 1.5 Vp-p. Balanced versions of the circuit are even more linear 相似文献
113.
Jennifer L Graef Abbie E Smith Kristina L Kendall David H Fukuda Jordan R Moon Travis W Beck Joel T Cramer Jeffrey R Stout 《Journal of the International Society of Sports Nutrition》2009,6(1):18-7
Background
High-intensity interval training has been shown to be a time-efficient way to induce physiological adaptations similar to those of traditional endurance training. Creatine supplementation may enhance high-intensity interval training, leading to even greater physiological adaptations. The purpose of this study was to determine the effects of high-intensity interval training (HIIT) and creatine supplementation on cardiorespiratory fitness and endurance performance (maximal oxygen consumption (VO2PEAK), time-to-exhaustion (VO2PEAKTTE), ventilatory threshold (VT), and total work done (TWD)) in college-aged men. 相似文献114.
T Frehmann C Flores F Luekewille T Mietzel B Spengler W F Geiger 《Water science and technology》2005,52(5):151-158
A special arrangement of combined sewer overflow tanks is the in-line storage sewer with downstream discharge (ISS-down). This layout has the advantage that, besides the sewer system, no other structures are required for stormwater treatment. The verification of the efficiency with respect to the processes of sedimentation and remobilization of sediment within the in-line storage sewer with downstream discharge is carried out in a combination of a field and a pilot plant study. The model study was carried out using a pilot plant model scaled 1:13. The following is intended to present some results of the pilot plant study and the mathematical empirical modelling of the sedimentation and remobilization process. 相似文献
115.
Heinz Jordan Karl Schönbacher 《Electrical Engineering (Archiv fur Elektrotechnik)》1941,35(3):185-192
Zusammenfassung Für verschiedene Phasen- und Lochzahlen je Pol und Phase sind die Werte der abgeleiteten Beziehung, die auch für Phasenzahlen kleiner als 1 ihre Gültigkeit behält, in einer Tafel zusammengestellt. In Anbetracht der Vorteile von vielphasigen Wicklungen wird eine 12phasige Schaltung für 3phasigen Netzanschlu\ angegeben.Mit Rücksicht auf die Wichtigkeit für die Berechnung der Drehmomente von Oberfeldern sind für den Käfiganker die Werte der doppeltverketteten Streuung in Abhängigkeit von den Phasenzahlen (m=0,3 bis 40) in Kurvenform dargestellt. Diese gelten auch für die sogenannten oberfeldarmen Wicklungen, bei denen die Phasenzahl durch Kunstschaltungen soweit erhöht wird, da\ nur mehr die Lochzahlq=1 verbleibt.Bezeichnungen
m
Phasenzahl des Strombelages
-
q
Stabzahl je Polpaar und Phase
-
d
Koeffizient der doppeltverketteten Streuung
-
Ordnungszahl der Stäbe je Pol und Phase
-
Ordnungszahl der Phasen
-
v
Ordnungszahl der Oberfelder
-
Abszisse des ersten Stabes der ersten Phase (Bogenma\)
-
x
Abszisse der Feldkurve in elektrischen Graden
-
zeitlicher Phasenwinkel des Stromes der ersten Phase ( elektr.)
-
p
Polpaarzahl
-
y
Ordinate der Feldkurve
-
y
1
Amplitude der Grundwelle
-
v
Amplitude desv-ten Kosinusgliedes
-
b
v
Amplitude desv-ten Sinusgliedes
- Z
Zähnezahl des Käfigläufers 相似文献
116.
117.
Monoterpenoid content of sage grouse ingesta 总被引:1,自引:0,他引:1
Bruce L. Welch Jordan C. Pederson Ronald L. Rodriguez 《Journal of chemical ecology》1989,15(3):961-969
We tested the hypothesis that the monoterpenoid levels in the ingesta from various digestive organs of sage grouse are less than that expected from the big sagebrush leaves ingested. Results supported the hypothesis. Dramatic reductions occurred between the gizzard and duodenum. Monoterpenoid levels in the ceca were nil; thus adverse effects of monoterpenoids on ceca microbes would also be nil.The use of trade or firm names in this paper is for reader information and does not imply endorsement by the U.S. Department of Agriculture of any product or service. 相似文献
118.
119.
Dirk C. Jordan Sarah R. Kurtz Kaitlyn VanSant Jeff Newmiller 《Progress in Photovoltaics: Research and Applications》2016,24(7):978-989
Published data on photovoltaic (PV) degradation measurements were aggregated and re‐examined. The subject has seen an increased interest in recent years resulting in more than 11 000 degradation rates in almost 200 studies from 40 different countries. As studies have grown in number and size, we found an impact from sampling bias attributable to size and accuracy. Because of the correlational nature of this study we examined the data in several ways to minimize this bias. We found median degradation for x‐Si technologies in the 0.5–0.6%/year range with the mean in the 0.8–0.9%/year range. Hetero‐interface technology (HIT) and microcrystalline silicon (µc‐Si) technologies, although not as plentiful, exhibit degradation around 1%/year and resemble thin‐film products more closely than x‐Si. Several studies showing low degradation for copper indium gallium selenide (CIGS) have emerged. Higher degradation for cadmium telluride (CdTe) has been reported, but these findings could reflect a convolution of less accurate studies and longer stabilization periods for some products. Significant deviations for beginning‐of‐life measurements with respect to nameplate rating have been documented over the last 35 years. Therefore, degradation rates that use nameplate rating as reference may be significantly impacted. Studies that used nameplate rating as reference but used solar simulators showed less variation than similar studies using outdoor measurements, even when accounting for different climates. This could be associated with confounding effects of measurement uncertainty and soiling that take place outdoors. Hotter climates and mounting configurations that lead to sustained higher temperatures may lead to higher degradation in some, but not all, products. Wear‐out non‐linearities for the worst performing modules have been documented in a few select studies that took multiple measurements of an ensemble of modules during the lifetime of the system. However, the majority of these modules exhibit a fairly linear decline. Modeling these non‐linearities, whether they occur at the beginning‐of‐life or end‐of‐life in the PV life cycle, has an important impact on the levelized cost of energy. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
120.
Michel Grosse Kerstin Günther Paul M. Jordan Dávid Roman Oliver Werz Christine Beemelmanns 《Chembiochem : a European journal of chemical biology》2022,23(9):e202200073
δ-Hydroxy-β-keto esters and δ,β-dihydroxy esters are characteristic structural motifs of statin-type natural products and drug candidates. Here, we describe the synthesis of functionalized δ-hydroxy-β-keto esters in good yields and excellent enantioselectivities using Chan's diene and modified Mukaiyama-aldol reaction conditions. Diastereoselective reduction of δ,β-dihydroxy esters afforded the respective syn- and anti-diols, and saponification yielded the corresponding acids. All products were evaluated for their anti-inflammatory properties, which uncovered a surprising structure-activity relationship. 相似文献