全文获取类型
收费全文 | 4801篇 |
免费 | 83篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 182篇 |
综合类 | 7篇 |
化学工业 | 916篇 |
金属工艺 | 88篇 |
机械仪表 | 73篇 |
建筑科学 | 72篇 |
矿业工程 | 2篇 |
能源动力 | 112篇 |
轻工业 | 368篇 |
水利工程 | 22篇 |
石油天然气 | 10篇 |
无线电 | 528篇 |
一般工业技术 | 735篇 |
冶金工业 | 1343篇 |
原子能技术 | 131篇 |
自动化技术 | 303篇 |
出版年
2023年 | 20篇 |
2022年 | 78篇 |
2021年 | 86篇 |
2020年 | 35篇 |
2019年 | 45篇 |
2018年 | 49篇 |
2017年 | 43篇 |
2016年 | 75篇 |
2015年 | 36篇 |
2014年 | 91篇 |
2013年 | 175篇 |
2012年 | 126篇 |
2011年 | 178篇 |
2010年 | 123篇 |
2009年 | 152篇 |
2008年 | 155篇 |
2007年 | 134篇 |
2006年 | 124篇 |
2005年 | 116篇 |
2004年 | 114篇 |
2003年 | 114篇 |
2002年 | 103篇 |
2001年 | 128篇 |
2000年 | 96篇 |
1999年 | 138篇 |
1998年 | 561篇 |
1997年 | 338篇 |
1996年 | 242篇 |
1995年 | 130篇 |
1994年 | 136篇 |
1993年 | 114篇 |
1992年 | 67篇 |
1991年 | 56篇 |
1990年 | 55篇 |
1989年 | 53篇 |
1988年 | 55篇 |
1987年 | 51篇 |
1986年 | 51篇 |
1985年 | 46篇 |
1984年 | 37篇 |
1983年 | 38篇 |
1982年 | 40篇 |
1981年 | 45篇 |
1980年 | 25篇 |
1979年 | 28篇 |
1978年 | 23篇 |
1977年 | 31篇 |
1976年 | 54篇 |
1975年 | 15篇 |
1973年 | 15篇 |
排序方式: 共有4892条查询结果,搜索用时 15 毫秒
21.
The tensile strengths and elongations of starch films prepared from various unmodified and modified starches were measured. These properties were improved by addition of urea and polyvinyl alcohol to the starch paste. The results obtained were as follows.
- 1 The heating temperature greatly affected the tensile strength and elongation of various unmodified starches. Potato starch gave the best film.
- 2 Introduction of hydroxyethyl groups into corn starch had unexpectedly little affect on the properties of the films.
- 3 A combination of hydroxyethylation and acid-modification slightly improved the properties of the films.
- 4 No film could be obtained after combinations of hydroxyethylation and hypochlorite-oxidation, pyrodextrinization or α-amylase-dextrinization. However, addition of urea to these modified starches resulted in good films.
- 5 On addition of urea the elongation of starch films increased and the pastes adhered uniformly to water repellent surfaces.
- 6 A film with the best properties was prepared from a mixture of 67% acid-modified hydroxyethyl starch, 13% urea and 20% polyvinyl alcohol.
22.
23.
In order to elucidate the granular structure of the leguminous starches the speed of solubilization of several starches was determined by digestion with dimethyl sulfoxide and with α-amylase. By microscopic investigations with normal and polarized light different forms of erosion were observed in the different starches, all of them less intense than those observed in cereal starches. It was concluded that the starch granules of mucunã seeds are the most homogeneous and have the least porous structure, followed by chick pea, jack, lablab and guanda beans. It is supposed that maturation, climate and soil influence the cristallinity of the granules, resulting in different digestibility. 相似文献
24.
Masanori Ono Natsumi Toyoda Kyosuke Kagami Takashi Hosono Takeo Matsumoto Shin-ichi Horike Rena Yamazaki Mitsuhiro Nakamura Yasunari Mizumoto Tomoko Fujiwara Hitoshi Ando Hiroshi Fujiwara Takiko Daikoku 《International journal of molecular sciences》2022,23(14)
Recently, it was demonstrated that the expression of BMAL1 was decreased in the endometrium of women suffering from recurrent spontaneous abortion. To investigate the pathological roles of uterine clock genes during pregnancy, we produced conditional deletion of uterine Bmal1 (cKO) mice and found that cKO mice could receive embryo implantation but not sustain pregnancy. Gene ontology analysis of microarray suggested that uterine NK (uNK) cell function was suppressed in cKO mice. Histological examination revealed the poor formation of maternal vascular spaces in the placenta. In contrast to WT mice, uNK cells in the spongiotrophoblast layer, where maternal uNK cells are directly in contact with fetal trophoblast, hardly expressed an immunosuppressive NK marker, CD161, in cKO mice. By progesterone supplementation, pregnancy could be sustained until the end of pregnancy in some cKO mice. Although this treatment did not improve the structural abnormalities of the placenta, it recruited CD161-positive NK cells into the spongiotrophoblast layer in cKO mice. These findings indicate that the uterine clock system may be critical for pregnancy maintenance after embryo implantation. 相似文献
25.
Sodium-glucose co-transporter-2 inhibitors (SGLT2is) not only have antihyperglycemic effects and are associated with a low risk of hypoglycemia but also have protective effects in organs, including the heart and kidneys. The pathophysiology of diabetes involves chronic hyperglycemia, which causes excessive demands on pancreatic β-cells, ultimately leading to decreases in β-cell mass and function. Because SGLT2is ameliorate hyperglycemia without acting directly on β-cells, they are thought to prevent β-cell failure by reducing glucose overload in this cell type. Several studies have shown that treatment with an SGLT2i increases β-cell proliferation and/or reduces β-cell apoptosis, resulting in the preservation of β-cell mass in animal models of diabetes. In addition, many clinical trials have shown that that SGLT2is improve β-cell function in individuals with type 2 diabetes. In this review, the preclinical and clinical data regarding the effects of SGLT2is on pancreatic β-cell mass and function are summarized and the protective effect of SGLT2is in β-cells is discussed. 相似文献
26.
27.
28.
Matano T. Takai Y. Takahashi T. Sakito Y. Fujii I. Takaishi Y. Fujisawa H. Kubouchi S. Narui S. Arai K. Morino M. Nakamura M. Miyatake S. Sekiguchi T. Koyama K. 《Solid-State Circuits, IEEE Journal of》2003,38(5):762-768
A 1-Gb/s/pin 512-Mb DDRII SDRAM has been developed using a digital delay-locked loop (DLL) and a slew-rate-controlled output buffer. The digital DLL has a frequency divider for DLL input, performs at an operating frequency of up to 500 MHz at 1.6 V, and provides internal clocking with 50% duty-cycle correction. The DLL has a current-mirror-type interpolator, which enables a resolution as high as 14 ps, needs no standby current, and can operate at voltages as low as 0.8 V. The slew-rate impedance-controlled output buffer circuit reduces the output skew from 107 to 10 ps. This SDRAM was tested using a 0.13-/spl mu/m 126.5-mm/sup 2/ 512-Mb chip. 相似文献
29.
Cardenas Angelica Moreno Nakamura Pinto Miguel Kiyoshy Pietrosemoli Ermanno Zennaro Marco Rainone Marco Manzoni Pietro 《Mobile Networks and Applications》2020,25(3):961-968
Mobile Networks and Applications - In this paper we describe a low-cost and low-power consumption messaging system based on LoRa technology. More that one billion people worldwide cannot access... 相似文献
30.
Okamura H. Toyoshima H. Takeda K. Oguri T. Nakamura S. Takada M. Imai K. Kinoshita Y. Yoshida H. Yamazaki T. 《Solid-State Circuits, IEEE Journal of》1995,30(11):1196-1202
While an ECL-CMOS SRAM can achieve both ultra high speed and high density, it consumes a lot of power and cannot be applied to low power supply voltage applications. This paper describes an NTL (Non Threshold Logic)-CMOS SRAM macro that consists of a PMOS access transistor CMOS memory cell, an NTL decoder with an on-chip voltage generator, and an automatic bit line signal voltage swing controller. A 32 Kb SRAM macro, which achieves a 1 ns access time at 2.5 V power supply and consumes a mere 1 W, has been developed on a 0.4 μm BiCMOS technology 相似文献