全文获取类型
收费全文 | 6180篇 |
免费 | 8篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 13篇 |
综合类 | 2篇 |
化学工业 | 144篇 |
金属工艺 | 6篇 |
机械仪表 | 17篇 |
建筑科学 | 18篇 |
矿业工程 | 1篇 |
能源动力 | 11篇 |
轻工业 | 57篇 |
水利工程 | 2篇 |
石油天然气 | 1篇 |
无线电 | 64篇 |
一般工业技术 | 192篇 |
冶金工业 | 5584篇 |
原子能技术 | 2篇 |
自动化技术 | 76篇 |
出版年
2021年 | 5篇 |
2019年 | 5篇 |
2017年 | 5篇 |
2015年 | 4篇 |
2014年 | 5篇 |
2013年 | 28篇 |
2012年 | 21篇 |
2011年 | 24篇 |
2010年 | 15篇 |
2009年 | 16篇 |
2008年 | 18篇 |
2007年 | 19篇 |
2006年 | 23篇 |
2005年 | 13篇 |
2004年 | 18篇 |
2003年 | 22篇 |
2002年 | 11篇 |
2001年 | 6篇 |
2000年 | 19篇 |
1999年 | 184篇 |
1998年 | 1726篇 |
1997年 | 958篇 |
1996年 | 605篇 |
1995年 | 355篇 |
1994年 | 314篇 |
1993年 | 338篇 |
1992年 | 58篇 |
1991年 | 74篇 |
1990年 | 88篇 |
1989年 | 77篇 |
1988年 | 90篇 |
1987年 | 88篇 |
1986年 | 71篇 |
1985年 | 79篇 |
1984年 | 15篇 |
1983年 | 24篇 |
1982年 | 37篇 |
1981年 | 44篇 |
1980年 | 67篇 |
1979年 | 18篇 |
1978年 | 24篇 |
1977年 | 166篇 |
1976年 | 353篇 |
1975年 | 11篇 |
1974年 | 4篇 |
1973年 | 6篇 |
1972年 | 5篇 |
1970年 | 4篇 |
1969年 | 6篇 |
1955年 | 4篇 |
排序方式: 共有6190条查询结果,搜索用时 15 毫秒
41.
The objective of this study was to determine whether differential labeling of 13C occurs in pigs fed diets with different 13C abundances and, if so, to use 13C as a label to determine true amino acid digestibility. Forty-eight pigs averaging 10.5 kg BW were fed dietary treatments consisting of a corn-corn gluten meal-crystalline amino acid diet (C-CGM) and a wheat-soybean meal diet (W-SBM). The 13C abundance of the amino acid fraction (AAF) of the C-CGM and W-SBM diets averaged delta 13C -14.19 and -26.36/1000, respectively. Three pigs/treatment group were killed when groups averaged 10.5 (initial), 22.9, and 46.6 kg BW, and AAF of organs were analyzed for 13C abundance. Carbon 13 in empty body AAF increased (-18.14, -13.98, and -12.66/1000) with increasing body weight in pigs fed the C-CGM diet and decreased (-18.06, -22.78, and -24.76/1000) in pigs fed the W-SBM diet. Liver, small intestine, and longissimus muscle tissues showed similar trends. Each tissue had dietary treatment effects (P < .001) and dietary treatment x weight group (P < .001) interactions. Ten pigs averaging 55.0 kg BW from each treatment group were assigned to metabolism cages and fed at 0700 and 1900. Six of these pigs from each treatment group were implanted with T-cannulas in the ileum and given a 17-d recovery period. At 1900 on d 0 of the collection phase, pigs were switched to the opposite diet that contained chromic oxide.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
42.
ET Berdusco GL Hammond RA Jacobs A Grolla K Akagi D Langlois JR Challis 《Canadian Metallurgical Quarterly》1993,132(5):2001-2008
43.
A case of Macrozamia riedlei seed poisoning is described in a young Dachshund. Vomiting and depression commenced within 6 h of ingestion; other signs that developed included severe hepatopathy, jaundice, abdominal pain that was unresponsive to analgesics, severe gastro-intestinal haemorrhage and thrombocytopenia as well as crystalluria and marrow dyserythropoiesis. The dog was euthanased 6 days after ingestion of the seeds. 相似文献
44.
45.
46.
47.
KK Doak CE Haas KJ Dunnigan RA Reiss JR Reiser J Huntress JL Altavela 《Canadian Metallurgical Quarterly》1998,18(3):637-645
In the absence of E1B, the 289-amino acid product of human adenovirus type 5 13S E1A induces p53-independent apoptosis by a mechanism that requires viral E4 gene products (Marcellus, R.C., J.C. Teodoro, T. Wu, D.E. Brough, G. Ketner, G.C. Shore, and P.E. Branton. 1996. J. Virol. 70:6207-6215) and involves a mechanism that includes activation of caspases (Boulakia, C.A., G. Chen, F.W. Ng, J. G. Teodoro, P.E. Branton, D.W. Nicholson, G.G. Poirier, and G.C. Shore. 1996. Oncogene. 12:529-535). Here, we show that one of the E4 products, E4orf4, is highly toxic upon expression in rodent cells regardless of the p53 status, and that this cytotoxicity is significantly overcome by coexpression with either Bcl-2 or Bcl-XL. Conditional expression of E4orf4 induces a cell death process that is characterized by apoptotic hallmark features, such as externalization of phosphatidylserine, loss of mitochondrial membrane potential, cytoplasmic vacuolation, condensation of chromatin, and internucleosomal DNA degradation. However, the wide-spectrum inhibitor of caspases, tetrapeptide zVAD-fmk, does not affect any of these apoptogenic manifestations, and does not alter the kinetics of E4orf4-induced cell death. Moreover, E4orf4 expression does not result in activation of the downstream effector caspase common to most apoptosis-inducing events, caspase-3 (CPP32). We conclude, therefore, that in the absence of E1A, E4orf4 is sufficient by itself to trigger a p53-independent apoptosis pathway that may operate independently of the known zVAD-inhibitable caspases, and that may involve an as yet uncharacterized mechanism. 相似文献
48.
FS Kraly RA Tribuzio YM Kim ME Keefe J Finkell 《Canadian Metallurgical Quarterly》1995,58(6):1091-1097
A role for endogenous histamine and its H3 receptor subtype for mediating drinking elicited by eating was examined in adult male Sprague-Dawley rats. The i.p. injection of the H3 agonist R-alpha-methylhistamine (Ramh, 2.5 mg/kg) shortened the latency to initiate drinking and increased 1-h water intake in nondeprived rats freely eating pellets and drinking water. The ICV injection (through a surgically implanted chronic cannula) of 10 micrograms Ramh increased water intake; this Ramh-induced drinking was abolished by previous ICV injection of the H3 antagonist thioperamide (Th, 60 micrograms). For rats drinking and eating after 24-h food deprivation, s.c. Th inhibited drinking behavior: for example, 10 mg/kg Th s.c. delayed the latency to initiate drinking and inhibited 1-h water intake without inhibition of food intake. In contrast, 60 micrograms Th ICV failed to inhibit food-related drinking in rats eating after food deprivation. For nondeprived rats eating a small cracker, 10 mg/kg Th s.c. delayed the latency to initiate drinking and abolished water intake without effect of eating, and 60 micrograms Th ICV had similar effects upon drinking elicited by ingestion of cracker. The IG infusion (through a surgically implanted gastric catheter) of 2 ml 600 or 900 mOsm/kg NaCl, a treatment that is subthreshold for increase in systemic plasma osmolality at the initiation of drinking, elicited drinking that was abolished by 10 mg/kg Th s.c. and attenuated by 60 micrograms Th ICV. The IG infusion of 2 ml 1800 mOsm/kg NaCl, a treatment that is above threshold for increase in systemic plasma osmolality, elicited drinking that was attenuated by 10 mg/kg s.c. or 60 micrograms Th ICV. These results demonstrate that peripheral and central H3 receptors for histamine have a role in drinking elicited by eating and the postprandial gastrointestinal osmotic consequences of eating. These findings extend the evidence demonstrating a histaminergic contribution to food-related drinking in rats. 相似文献
49.
50.
Empirical research pertaining to cardiopulmonary resuscitation (CPR), clinician behaviors related to do-not-resuscitate (DNR) orders and substituted judgment suggests potential contributions to medical ethics. Research quantifying the likelihood of surviving CPR points to the need for further philosophical analysis of the limitations of the patient autonomy in decision making, the nature and definition of medical futility, and the relationship between futility and professional standards. Research on DNR orders has identified barriers to the goal of patient involvement in these life and death discussions. The initial data on surrogate decision making also points to the need for a reexamination of the moral basis for substituted judgment, the moral authority of proxy decision making and the second-order status of the best interests standard. These examples of empirical research suggest that an interplay between empirical research, ethical analysis and policy development may represent a new form of interdisciplinary scholarship to improve clinical medicine. 相似文献