全文获取类型
收费全文 | 964篇 |
免费 | 34篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 48篇 |
化学工业 | 226篇 |
金属工艺 | 23篇 |
机械仪表 | 19篇 |
建筑科学 | 8篇 |
能源动力 | 47篇 |
轻工业 | 74篇 |
石油天然气 | 1篇 |
无线电 | 98篇 |
一般工业技术 | 182篇 |
冶金工业 | 153篇 |
原子能技术 | 38篇 |
自动化技术 | 82篇 |
出版年
2023年 | 13篇 |
2022年 | 24篇 |
2021年 | 45篇 |
2020年 | 19篇 |
2019年 | 17篇 |
2018年 | 27篇 |
2017年 | 26篇 |
2016年 | 37篇 |
2015年 | 24篇 |
2014年 | 39篇 |
2013年 | 55篇 |
2012年 | 48篇 |
2011年 | 51篇 |
2010年 | 27篇 |
2009年 | 30篇 |
2008年 | 43篇 |
2007年 | 26篇 |
2006年 | 23篇 |
2005年 | 11篇 |
2004年 | 20篇 |
2003年 | 24篇 |
2002年 | 23篇 |
2001年 | 15篇 |
2000年 | 20篇 |
1999年 | 21篇 |
1998年 | 66篇 |
1997年 | 25篇 |
1996年 | 32篇 |
1995年 | 19篇 |
1994年 | 12篇 |
1993年 | 13篇 |
1992年 | 15篇 |
1991年 | 11篇 |
1990年 | 10篇 |
1989年 | 11篇 |
1988年 | 13篇 |
1987年 | 5篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 4篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1975年 | 6篇 |
1974年 | 3篇 |
1972年 | 3篇 |
排序方式: 共有999条查询结果,搜索用时 554 毫秒
91.
92.
Hiroshi Yamamoto Yudai Nakamura Shigemi Moriguchi Yuki Nakamura Yuta Honda Ikumi Tamura Yoshiko Hirata Akihide Hayashi Jun Sekizawa 《Water research》2009,43(2):351-362
We selected eight pharmaceuticals with relatively high potential ecological risk and high consumption—namely, acetaminophen, atenolol, carbamazepine, ibuprofen, ifenprodil, indomethacin, mefenamic acid, and propranolol—and conducted laboratory experiments to examine the persistence and partitioning of these compounds in the aquatic environment. In the results of batch sunlight photolysis experiments, three out of eight pharmaceuticals—propranolol, indomethacin, and ifenprodil—were relatively easily photodegraded (i.e., half-life < 24 h), whereas the other five pharmaceuticals were relatively stable against sunlight. The results of batch biodegradation experiments using river water suggested relatively slow biodegradation (i.e., half-life > 24 h) for all eight pharmaceuticals, but the rate constant was dependent on sampling site and time. Batch sorption experiments were also conducted to determine the sorption coefficients to river sediments and a model soil sample. The determined coefficients (Kd values) were much higher for three amines (atenolol, ifenprodil, and propranolol) than for neutral compounds or carboxylic acids; the Kd values of the amines were comparable to those of a four-ring polycyclic aromatic hydrocarbon (PAH) pyrene. The coefficients were also higher for sediment/soil with higher organic content, and the organic carbon-based sorption coefficient (log Koc) showed a poor linear correlation with the octanol-water distribution coefficient (log Dow) at neutral pH. These results suggest other sorption mechanisms—such as electrochemical affinity, in addition to hydrophobic interaction—play an important role in sorption to sediment/soil at neutral pH. 相似文献
93.
We report a simple method for the fabrication of reproducible, clean, and stable MgB2 superconducting tips. The quality of these tips has been verified by imaging the surface of a thin Au(111) film sample, using a low temperature scanning tunneling microscopy (STM). Using the MgB2 superconducting tip, high-quality semiatomically resolved STM surface images of the thin Au(111) film sample have been observed, which unambiguously indicates that the fabrication of relatively superconducting MgB2, suitable for use as STM tips, is feasible. 相似文献
94.
K Toda E Tatsumi Y Taenaka T Masuzawa H Takano 《Canadian Metallurgical Quarterly》1996,62(6):1737-1742
BACKGROUND: We postulated that pathophysiologic processes under nonpulsatile circulation are related to the behavior of the sympathetic nerve activity that regulates tissue perfusion. METHODS: Pulsatile and nonpulsatile pumps were installed in parallel in the left heart bypass circuit of anesthetized goats (n = 9) so that pulsatile circulation could be converted to nonpulsatile circulation instantly. At 5 minutes before and after systemic depulsation, we measured hemodynamic indices, renal nerve activity, and regional blood flow of the brain, heart, and renal cortex. RESULTS: Renal nerve activity was significantly elevated after systemic depulsation (15.6 +/- 9.3 versus 19.4 +/- 9.8 microV), when mean aortic pressure remained almost constant. The renal cortical flow was significantly reduced after depulsation (3.61 +/- 1.23 versus 2.93 +/- 1.19 mL.min-1.g-1), whereas no significant difference was found in the regional blood flow of the brain or the heart. CONCLUSIONS: The significant reduction of renal cortical blood flow after systemic depulsation is associated with a significant increase in renal nerve activity. Our results suggest that increased renal nerve activity plays an important role in the reduction of renal function after systemic depulsation. 相似文献
95.
SC Kaul EL Duncan A Englezou S Takano RR Reddel Y Mitsui R Wadhwa 《Canadian Metallurgical Quarterly》1998,17(7):907-911
The murine mortalin genes, mot-1 and mot-2, are members of the hsp70 family of proteins and differ from each other by only two amino acid residues. Mot-1 is expressed in normal cells and has pancytosolic cellular distribution whereas mot-2 is found in the perinuclear region of immortal cells. We report here that a high level of expression of mot-2 protein resulted in malignant transformation of cells as analysed by anchorage independent growth and nude mice assays. A high level of protein expression is attributed to the 900 bp 3' untranslated region of the cDNA which does not have any transforming activity per se. Mortalin cDNA clones isolated from human transformed cells were also found to have transforming activity in similar assays and a high level of expression was apparent in some of the human immortalized cells that showed non-pancytosolic mortalin immunofluorescence. Taken together, the data suggest that nonpancytosolic mortalin may have a role in tumorigenesis. 相似文献
96.
H Utsunomiya K Takano T Ogasawara T Hashimoto T Fukushima M Okazaki 《Canadian Metallurgical Quarterly》1998,19(3):547-549
We describe two infants in whom rhombencephalosynapsis was diagnosed with MR imaging in vivo. In contrast to Dandy-Walker malformation, the vermian maldevelopment in this anomaly is characterized by an absence of the anterior vermis and a deficiency of the posterior vermis. The cerebellar hemispheres are fused. In an attempt to identify the pathogenesis of these anatomic manifestations, we question the traditional concept of the embryologic development of the cerebellar primordium. 相似文献
97.
M Ikenaga Y Takano Y Ohtani H Tsukamoto Y Hiki A Kakita I Okayasu 《Canadian Metallurgical Quarterly》1998,48(6):453-459
In order to clarify the cell kinetics of colorectal villous tumors (VT), 21 villous adenomatous areas and 12 carcinomatous areas within villous adenomas were investigated for proliferative activity and apoptosis and compared with a series of 41 tubular tumors (TT), demonstrating elements of intramucosal carcinomas as well as tubular adenomas (so-called carcinoma in tubular adenoma). Proliferation was estimated in terms of Ki-67 labeling indices and mitotic indices, and apoptosis was assessed by DNA nick-end labeling to give apoptotic indices. Apoptotic indices of villous adenomatous and carcinomatous regions were significantly lower than the values for their tubular counterparts. Ki-67 labeling indices were also significantly lower for adenoma components. Apoptotic indices, Ki-67 labeling indices and mitotic indices increased with atypia raised in tubular adenoma components. Correlations of mitotic indices with apoptotic indices, Ki-67 labeling indices with apoptotic indices and mitotic indices with Ki-67 labeling indices were found for each villous tumor group and tubular tumor group, and the apoptosis and proliferation ratios for villous tumors were relatively low, suggesting a tendency for greater growth due to less cell deletion. Although this is only one of the biological features of villous tumor groups, it might play a major role in generation of malignancy. 相似文献
98.
T Koshino S Takano T Houjo Y Sano K Kudo H Kihara S Kitani T Takaishi K Hirai K Ito Y Morita 《Canadian Metallurgical Quarterly》1998,247(2):510-513
Hormone-sensitive lipase (HSL) catalyzes the rate-limiting step in adipocyte lipolysis. We have studied the effect of glucose and long chain fatty acids on the HSL mRNA content of 3T3-F442A adipocytes. Exposure of the cells for 32 h to a medium without glucose led to a decrease by a factor of 2.5-3 in the HSL mRNA without a change in C/EBP alpha mRNA or triglyceride content of the adipocytes. The reduction in HSL mRNA level was accompanied by a decrease in HSL total activity. The effect of glucose exposure was observed after 24 h of exposure and was reversible. Treatment of the adipocytes with oleate did not affect HSL expression. These data show that glucose modulates HSL gene expression and hence could participate in the regulation of adipose tissue lipolysis. 相似文献
99.
100.
E Kojima K Naito M Iwai Y Hirose K Isobe K Takano 《Canadian Metallurgical Quarterly》1997,36(7):528-531
A 37-year-old woman underwent an emergency operation at our hospital because of severe abdominal pain and ileus. Most of her small intestine and ascending colon were observed to have become necrotic due to occlusion of her superior mesenteric artery (SMA). Pathological findings of the resected intestine revealed that her SMA was completely thrombosed 2 cm distal from its origin with smooth muscle proliferation. Post-surgical blood analysis of her pre-operative serum was positive for lupus anticoagulant and antinuclear antibodies. She noticed vaginal bleeding due to missed abortion on the 31st day after the operation. We diagnosed her acute abdominal pain to be that of antiphospholipid syndrome associated with her pregnancy. 相似文献