全文获取类型
收费全文 | 1960篇 |
免费 | 11篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 5篇 |
化学工业 | 75篇 |
金属工艺 | 7篇 |
机械仪表 | 11篇 |
建筑科学 | 16篇 |
矿业工程 | 4篇 |
能源动力 | 12篇 |
轻工业 | 46篇 |
水利工程 | 7篇 |
石油天然气 | 3篇 |
无线电 | 57篇 |
一般工业技术 | 54篇 |
冶金工业 | 1607篇 |
原子能技术 | 10篇 |
自动化技术 | 58篇 |
出版年
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 4篇 |
2018年 | 8篇 |
2017年 | 4篇 |
2016年 | 9篇 |
2014年 | 4篇 |
2013年 | 18篇 |
2012年 | 12篇 |
2011年 | 17篇 |
2010年 | 21篇 |
2009年 | 9篇 |
2008年 | 13篇 |
2007年 | 17篇 |
2006年 | 18篇 |
2005年 | 22篇 |
2004年 | 15篇 |
2003年 | 18篇 |
2002年 | 15篇 |
2001年 | 14篇 |
2000年 | 11篇 |
1999年 | 63篇 |
1998年 | 431篇 |
1997年 | 246篇 |
1996年 | 196篇 |
1995年 | 95篇 |
1994年 | 85篇 |
1993年 | 93篇 |
1992年 | 13篇 |
1991年 | 28篇 |
1990年 | 42篇 |
1989年 | 39篇 |
1988年 | 41篇 |
1987年 | 32篇 |
1986年 | 36篇 |
1985年 | 25篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 11篇 |
1981年 | 17篇 |
1980年 | 14篇 |
1979年 | 5篇 |
1978年 | 11篇 |
1977年 | 52篇 |
1976年 | 77篇 |
1975年 | 6篇 |
1973年 | 4篇 |
1971年 | 7篇 |
1966年 | 4篇 |
1948年 | 3篇 |
排序方式: 共有1972条查询结果,搜索用时 15 毫秒
81.
CR Albrightson B Zabko-Potapovich G Dytko WM Bryan K Hoyle ML Moore JM Stadel 《Canadian Metallurgical Quarterly》1994,6(7):743-750
Thrombin stimulates cytosolic calcium mobilization and tritiated thymidine incorporation in rat glomerular mesangial cells. This effect may be mediated by a thrombin receptor similar to the receptor found in human platelets. In order to test this possibility, a series of analogues of the thrombin receptor peptide, SFLL-RNPNDKYEPF, was evaluated for their effects on mesangial cells. Analogues of the thrombin receptor peptide containing five, six, seven and 14 amino acids were as efficacious as thrombin with respect to calcium mobilization and thymidine incorporation, although they were significantly less potent. The dissimilarity in potency between thrombin and the thrombin receptor peptides is consistent with the kinetics of the proposed mechanism of action of the enzyme, since the cleavage by thrombin of its receptor results in a tethered ligand which is at a relatively high concentration compared to the free peptides in solution. Those thrombin receptor peptide analogues which showed decreased activity in platelets were tested in mesangial cells. Removal of serine at position one, N-acetylation, or replacement of the phenylalanine at position two with alanine resulted in analogues which were inactive in stimulating mesangial cell proliferation or calcium mobilization. In addition, those analogues which had no stimulatory effects in mesangial cells were not antagonists of SFLLRN-mediated calcium mobilization and thymidine incorporation in mesangial cells. 相似文献
82.
PA Winstanley EK Mberu IS Szwandt AM Breckenridge WM Watkins 《Canadian Metallurgical Quarterly》1995,39(4):948-952
The potency of antimalarial dihydrofolate reductase inhibitors, alone and in synergistic combination with dihydropteroate synthetase inhibitors, against the Kenyan K39 strain of Plasmodium falciparum (pyrimethamine resistant) and against normal replicating human bone marrow cells in in vitro culture has been studied. Therapeutic indices and rank order of synergistic potency were derived. Trimethoprim, pyrimethamine, and the quinazolines WR159412 and WR158122 had the smallest therapeutic indices (1.39, 4.38, 2.56, and 90.0, respectively), while the three triazines clociguanil, WR99210, and chlorcycloguanil had the largest (3,562, 3,000, and 2,000, respectively). In rank order of decreasing activity against P. falciparum, the six most potent drug combinations were WR99210-dapsone, chlorcycloguanil-dapsone, WR158122-dapsone, WR159412-dapsone, WR159412-sulfamethoxazole, and chlorcycloguanil-sulfamethoxazole; pyrimethamine-sulfadoxine was the least potent combination. These experiments form a basis for the selection of rapidly eliminated antifolate combinations for further clinical testing. 相似文献
83.
84.
85.
The results of a reactivity-initiated accident experiment, designated RIA-ST-4, are discussed and analyzed with regard to molten fuel-coolant interaction (MFCI). In this experiment, extensive amounts of molten UO2 fuel and zircaloy cladding were produced and fragmented upon mixing with the coolant. Coolant pressurization up to 35 MPa and coolant overheating in excess of 940 K occurred after fuel rod failure. The initial coolant conditions were similar to those in boiling water reactors during a hot startup (that is, coolant pressure of 6.45 MPa, coolant temperature of 538 K, and coolant flow rate of 85 cm3/s). It is concluded that the high coolant pressure recorded in the RIA-ST-4 experiment was caused by an MFCI and was not due to gas release from the test rod at failure, Zr/water reaction, of UO2 fuel vapor pressure. The high coolant temperature indicated the presence of superheated steam, which may have formed during the expansion of the working fluid back to the initial coolant pressure; yet, the thermal-to-mechanical energy conversion ratio is estimated to be only about 0.3%. 相似文献
86.
WM Blaney 《Canadian Metallurgical Quarterly》1977,184(3):397-409
The olfactory sensilla on the maxillary palp tip of Locusta migratoria (L.) resemble the surrounding contact chemoreceptors in general morphology. The perforated peg has a thicker wall than is commonly found in olfactory sensilla. The form and position of the sensilla are considered in relation of the olfactory function. The fine structure of the dendrites is discussed in relation to that described in other olfactory sensilla. 相似文献
87.
JJ Ellestad-Sayed RA Nelson MA Adson WM Palmer EH Soule 《Canadian Metallurgical Quarterly》1976,29(12):1333-1338
To investigate further an apparent relationship between chronic ulcerative and granulomatous colitis and pantothenic acid deficiency, colonic tissues obtained at the time of colectomy in 29 patients with these disorders were assayed for pantothenic acid and for coenzyme A (CoA) activity. For comparison, normal colonic tissues free of pathological lesions were obtained from 31 patients having colectomy for carcinoma or diverticulitis. Plasma, red blood cells, and colonic mucosa were assayed microbiologically for free and total pantothenic acid. The activity of CoA in colonic mucosa was determined by assaying the acetylation of sulfanilamide. Concentrations of free, bound, and total pantothenic acid in blood and in colonic mucosa did not differ between the two groups of patients. Bound pantothenic acid increased linearly with total pantothenic acid. Colonic mucosa concentrated free pantothenic acid to about 50 times the level of blood, and pantothenic acid in red cells was similar to the concentration in plasma. Compared to normal gut mucosa, CoA activity was markedly low in mucosa from patients with chronic ulcerative or granulomatous disease despite the presence of normal amounts of free and bound pantothenic acid. A block in the conversion of bound pantothenic acid to CoA in diseased mucosa is suggested. 相似文献
88.
89.
90.
We studied a 14-year-old girl who suffered fractures of her mandible and tegmen following a fall from a balance beam. Thirteen days after hospitalization, she developed severe, protracted, recurrent episodes of hyperventilation; subsequently, she suffered posthyperventilation apnea, which at times was prolonged and association with severe hypoxemia with an arterial oxygen pressure as low as 25 mm Hg. The patient was treated with added dead space and chlorpromazine hydrochloride (Thorazine). Postulated mechanisms for her disorder are discussed. The importance of close clinical and laboratory observation in similar cases is stressed. 相似文献