全文获取类型
收费全文 | 1077篇 |
免费 | 48篇 |
专业分类
电工技术 | 11篇 |
综合类 | 1篇 |
化学工业 | 285篇 |
金属工艺 | 34篇 |
机械仪表 | 49篇 |
建筑科学 | 57篇 |
矿业工程 | 1篇 |
能源动力 | 35篇 |
轻工业 | 61篇 |
水利工程 | 7篇 |
石油天然气 | 1篇 |
无线电 | 68篇 |
一般工业技术 | 218篇 |
冶金工业 | 81篇 |
原子能技术 | 4篇 |
自动化技术 | 212篇 |
出版年
2023年 | 18篇 |
2022年 | 15篇 |
2021年 | 50篇 |
2020年 | 37篇 |
2019年 | 47篇 |
2018年 | 33篇 |
2017年 | 18篇 |
2016年 | 36篇 |
2015年 | 37篇 |
2014年 | 41篇 |
2013年 | 61篇 |
2012年 | 71篇 |
2011年 | 88篇 |
2010年 | 65篇 |
2009年 | 51篇 |
2008年 | 45篇 |
2007年 | 62篇 |
2006年 | 41篇 |
2005年 | 39篇 |
2004年 | 27篇 |
2003年 | 17篇 |
2002年 | 26篇 |
2001年 | 15篇 |
2000年 | 13篇 |
1999年 | 9篇 |
1998年 | 31篇 |
1997年 | 20篇 |
1996年 | 12篇 |
1995年 | 17篇 |
1994年 | 7篇 |
1993年 | 7篇 |
1992年 | 6篇 |
1991年 | 2篇 |
1990年 | 5篇 |
1989年 | 3篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1983年 | 3篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1977年 | 2篇 |
1976年 | 5篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1969年 | 2篇 |
1967年 | 2篇 |
1966年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有1125条查询结果,搜索用时 15 毫秒
991.
Male and female rats were fed diets containing 2% of calories as corn oil or that plus 40% of calories as beef tallow or corn
oil. After 3, 6, 12 and 18 months groups were given 4-14C-cholesterol ip, and feces were collected for 9 days. Just prior to necropsy3H-acetate was administered ip. Samples of serum, liver, heart and carcass were obtained for analysis. Concentrations of fatty
acids and cholesterol, synthesis of those and recovery of ring-labeled steroid are reported. Mortality from acute respiratory
disease was very high in male rats fed beef tallow or low fat diets and very low in those fed the corn oil diet. In females,
only beef tallow diet resulted in a high mortality rate, and this was lower and at a later age than in males. The most notable
effects of age were in relation to fatty acid synthesis and presence of14C-acidic steroid in the carcass. In 3-month-old rats both fats depressed fatty acid synthesis in comparison to the low fat
diet. At later ages beef fat ceased to depress fatty acid synthesis in both sexes. Corn oil continued to depress fatty acid
synthesis up to 12 months in males and 18 months in females. The presence of14C-acidic steroid in carcass was substantial in 6-month-old rats and constituted ca. 40% of recovered14C in 18-month-old rats. The possibility that the increase in acetate incorporation into fatty acids with age in fat feeding
is related to chain elongation rather than de novo synthesis is discussed. Both the presence and amount of acidic steroid
in the carcass are notable and may be of importance in constructing models of cholesterol turnover.
Presented in part at the AOCS Sterol Symposium, April 1970, and the Federation of American Societies for Experimental Biology,
April 1971.
Scientific Series Paper No. 1536, Colorado Agricultural Experiment Station. 相似文献
992.
Alexander Tallner Anne Waschbisch Christian Hentschke Klaus Pfeifer Mathias M?urer 《International journal of molecular sciences》2015,16(7):14901-14911
Multiple sclerosis (MS) patients, in general, show reduced physical function, physical activity, and quality of life. Positive associations between physical activity and quality of life have been reported. In particular, we were interested in the relation between physical activity and mental health in MS patients without limitation of physical function, since limitations of physical function may influence both physical activity and quality of life. Assessment comprised the Baecke questionnaire on physical activity, the Short Form 36 Health Survey (SF-36), and Beck Depression Inventory (BDI). We ranked our sample according to physical activity into four groups and performed an ANOVA to analyze the relationship between levels of physical activity and health-related quality of life (HRQoL). Then we performed a subgroup analysis and included patients with unlimited walking distance and a score of less than 18 in the BDI. Most active vs. inactive patients were compared for the mental subscales of the SF-36 and depression scores. From 632 patients, 265 met inclusion criteria and hence quartiles were filled with 67 patients each. Active and inactive patients did not differ considerably in physical function. In contrast, mental subscales of the SF-36 were higher in active patients. Remarkable and significant differences were found regarding vitality, general health perception, social functioning and mental health, all in favor of physically active patients. Our study showed that higher physical activity is still associated with higher mental health scores even if limitations of physical function are accounted for. Therefore, we believe that physical activity and exercise have considerable health benefits for MS patients. 相似文献
993.
Csar Omar Ramírez Quiroz George D. Spyropoulos Michael Salvador Loïc M. Roch Marvin Berlinghof Jos Darío Perea Karen Forberich Laura‐Isabelle Dion‐Bertrand Nadine J. Schrenker Andrej Classen Nicola Gasparini Ganna Chistiakova Mathias Mews Lars Korte Bernd Rech Ning Li Frank Hauke Erdmann Spiecker Tayebeh Ameri Steve Albrecht Gonzalo Abelln Salvador Len Tobias Unruh Andreas Hirsch Aln Aspuru‐Guzik Christoph J. Brabec 《Advanced functional materials》2019,29(40)
A multipurpose interconnection layer based on poly(3,4‐ethylenedioxythiophene) doped with poly(styrene sulfonate) (PEDOT:PSS), and d ‐sorbitol for monolithic perovskite/silicon tandem solar cells is introduced. The interconnection of independently processed silicon and perovskite subcells is a simple add‐on lamination step, alleviating common fabrication complexities of tandem devices. It is demonstrated experimentally and theoretically that PEDOT:PSS is an ideal building block for manipulating the mechanical and electrical functionality of the charge recombination layer by controlling the microstructure on the nano‐ and mesoscale. It is elucidated that the optimal functionality of the recombination layer relies on a gradient in the d ‐sorbitol dopant distribution that modulates the orientation of PEDOT across the PEDOT:PSS film. Using this modified PEDOT:PSS composite, a monolithic two‐terminal perovskite/silicon tandem solar cell with a steady‐state efficiency of 21.0%, a fill factor of 80.4%, and negligible open circuit voltage losses compared to single‐junction devices is shown. The versatility of this approach is further validated by presenting a laminated two‐terminal monolithic perovskite/organic tandem solar cell with 11.7% power conversion efficiency. It is envisioned that this lamination concept can be applied for the pairing of multiple photovoltaic and other thin film technologies, creating a universal platform that facilitates mass production of tandem devices with high efficiency. 相似文献
994.
995.
996.
The maximum tolerable concentrations per animal position of hydrogen sulphide alone (5 ppm) and with ammonia (5 ppm H2S; 30 ppm NH3) were established by model experiments under defined environmental conditions. The normal values of the contaminant gas combination were found to be acceptable even with additional dust load on the experimental animals. TGL 29084 should stipulate 5 ppm hydrogen sulphide as the new maximum concentration per animal position. 相似文献
997.
K Mathias 《Canadian Metallurgical Quarterly》1976,29(8):393-398
The preoperative cholecystography and postoperative radiography of gallstones were compared in 68 patients. Calcified structures were detected in 32% of the stones which were free of calcium in the native roentgenograms. The possibility is stressed that the calciumocontent of cholecystographic transparent stones may be responsible for the failure of CDCA-therapy. 52 of the 68 patients additionally received a fat meal. A contraction of the gallbladder was not observed in 25% of these cases. From the missing contraction of the gallbladder should not be concluded that a CDCA-therapy is contraindicated. A functional analysis with a synthetic derivate of cholecystokinin is recommended. 相似文献
998.
JL Martin WJ Beck AP McDonald GM Carlson JR Mathias 《Canadian Metallurgical Quarterly》1983,5(4):315-319
A solid-phase meal labeled with 99mTc-sulfur colloid provides an improved clinical test for the quantitative evaluation of human gastric emptying. We studied 12 healthy male controls and five male patients with known gastric stasis secondary to a vagotomy and drainage procedure. All subjects were fasted for 8 hours before the study, and each consumed an unbuttered biscuit and a poached egg white containing 1 mCi of 99mTc-sulfur colloid. For 2 hours, 60-second counts were measured every 10 minutes by a Pho Gamma III scintillation camera. The t1/2 for control subjects was 60 minutes, at which time patients with gastric stasis had retained 98% of the test meal. At 120 minutes, control subjects and patients with gastric stasis had 4.7% and 89%, respectively, of the meal remaining in the stomach. The solid-phase test meal labeled with 99mTc-sulfur colloid is easy to perform and can be used clinically to quantitatively measure gastric emptying in humans. This test can discriminate between control subjects and patients with known gastric stasis. 相似文献
999.
6 typical bacteria species of the human intestinal flora (E. coli, Klebsiella pneumoniae, Proteus vulgaris, Streptococcus faecalis, Bacteroides fragilis, Bifidobacterium sp.) were incubated in a liquid medium for 48 h with [15N2]-urea and [15N]-ammonium chloride. The rates of [15N]-incorporation were calculated. They depend reproducible on the species examined, on the kind of the offered NPN-substance and on the amount of NPN-substance in the medium. With [15N2]-urea the minimal rate of incorporation was 3.8% (E coli) and the maximal one 95.6% (Bifidobacterium sp.). With [15N]-ammonium chloride the corresponding figures were 31.0 (Proteus vulg.) and 98.0% (Bifidobacterium sp.). The findings are discussed with regard to a possible enteral detoxification in uremic patients by bacterial utilization and elimination of urea and ammonia. 相似文献
1000.
D Lammer N Mathias JM Laplaza W Jiang Y Liu J Callis M Goebl M Estelle 《Canadian Metallurgical Quarterly》1998,12(7):914-926
The RUB1/NEDD-8 family of ubiquitin-related genes is widely represented among eukaryotes. Here we report that Cdc53p in Saccharomyces cerevisiae, a member of the Cullin family of proteins, is stably modified by the covalent attachment of a single Rub1p molecule. Two genes have been identified that are required for Rub1p conjugation to Cdc53p. The first gene, designated ENR2, encodes a protein with sequence similarity to the amino-terminal half of the ubiquitin-activating enzyme. By analogy with Aos1p, we infer that Enr2p functions in a bipartite Rub1p-activating enzyme. The second gene is SKP1, shown previously to be required for some ubiquitin-conjugation events. A deletion allele of ENR2 is lethal with temperature-sensitive alleles of cdc34 and enhances the phenotypes of cdc4, cdc53, and skp1, strongly implying that Rub1p conjugation to Cdc53p is required for optimal assembly or function of the E3 complex SCFCdc4. Consistent with this model, both enr2delta and an allele of Cdc53p that is not Rub1p modified, render cells sensitive to alterations in the levels of Cdc4p, Cdc34p, and Cdc53p. 相似文献