全文获取类型
收费全文 | 525026篇 |
免费 | 5012篇 |
国内免费 | 1049篇 |
专业分类
电工技术 | 8274篇 |
综合类 | 2651篇 |
化学工业 | 82606篇 |
金属工艺 | 26180篇 |
机械仪表 | 18283篇 |
建筑科学 | 11126篇 |
矿业工程 | 5069篇 |
能源动力 | 9558篇 |
轻工业 | 36063篇 |
水利工程 | 7245篇 |
石油天然气 | 15695篇 |
武器工业 | 55篇 |
无线电 | 49956篇 |
一般工业技术 | 111867篇 |
冶金工业 | 74178篇 |
原子能技术 | 14926篇 |
自动化技术 | 57355篇 |
出版年
2021年 | 4239篇 |
2019年 | 4092篇 |
2018年 | 21437篇 |
2017年 | 20605篇 |
2016年 | 17826篇 |
2015年 | 5208篇 |
2014年 | 8258篇 |
2013年 | 18549篇 |
2012年 | 14931篇 |
2011年 | 24420篇 |
2010年 | 20305篇 |
2009年 | 19026篇 |
2008年 | 20659篇 |
2007年 | 21488篇 |
2006年 | 12063篇 |
2005年 | 11610篇 |
2004年 | 11299篇 |
2003年 | 11014篇 |
2002年 | 10408篇 |
2001年 | 9712篇 |
2000年 | 9609篇 |
1999年 | 8904篇 |
1998年 | 18711篇 |
1997年 | 13837篇 |
1996年 | 10671篇 |
1995年 | 8479篇 |
1994年 | 7715篇 |
1993年 | 7726篇 |
1992年 | 6390篇 |
1991年 | 6216篇 |
1990年 | 6452篇 |
1989年 | 6261篇 |
1988年 | 6027篇 |
1987年 | 5631篇 |
1986年 | 5583篇 |
1985年 | 6138篇 |
1984年 | 5927篇 |
1983年 | 5565篇 |
1982年 | 5251篇 |
1981年 | 5347篇 |
1980年 | 5274篇 |
1979年 | 5381篇 |
1978年 | 5569篇 |
1977年 | 5881篇 |
1976年 | 7093篇 |
1975年 | 5031篇 |
1974年 | 5038篇 |
1973年 | 5153篇 |
1972年 | 4494篇 |
1971年 | 4143篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
181.
E Arvat R Giordano J Ramunni G Arnaldi A Colao R Deghenghi G Lombardi F Mantero F Camanni E Ghigo 《Canadian Metallurgical Quarterly》1998,83(12):4207-4211
We previously reported that in Cushing's disease (CD) the ACTH- and cortisol (F)-releasing activity of Hexarelin (HEX), a GH secretagogue, is exaggerated with respect to that in normal subjects and is higher than that of human CRH (hCRH), but it is absent in Cushing's syndrome. Our aim was to extend the study about the effects of HEX (2.0 microg/kg, iv) on ACTH and F secretion in 21 patients with CD (3 men and 18 women, 16-68 yr old). Based on magnetic resonance imaging, 15 CD patients had pituitary microadenoma, and 6 had macroadenoma. The results in CD patients were compared with those in 27 normal age-matched controls (NS; 10 men and 17 women, 24-69 yr old). Basal ACTH and F levels in CD were similar in patients with microadenom (mean+/-SEM, 78.3+/-7.2 pg/mL and 237.1+/-23.6 microg/L, respectively) and macroadenoma (57.4+/-9.0 pg/mL and 196.9+/-20.1 microg/L, respectively) and were higher (P < 0.001) than those in NS (17.7+/-2.0 pg/mL and 115.3+/-6.7 microg/L, respectively). In microadenoma CD patients, HEX induced marked ACTH and F increases (delta peak, mean+/-SEM: 261.2+/-77.6 pg/mL and 226.1+/-87.2 microg/L, respectively), which were higher (P < 0.04) than those induced by hCRH (45.6+/-16.9 pg/mL and 84.6+/-25.7 microg/L, respectively). Moreover, in microadenoma CD patients, the ACTH and F responses to HEX were higher (P < 0.001) than those in NS (18.5+/-4.0 pg/mL and 36.1+/-6.8 microg/L, respectively). In macroadenoma CD patients, HEX induced a slight, but significant increase (P < 0.02) in ACTH and F levels (33.9+/-18.0 pg/mL and 89.6+/-34.3 microg/L, respectively), which was not significantly different from that elicited by hCRH (20.0+/-7.0 pg/mL and 54.8+/-21.3 microg/L, respectively). In macroadenoma CD patients, the ACTH and F responses to HEX and hCRH were, in turn, similar to those in NS. In conclusion, our findings demonstrate that the ACTH and F hyperresponsiveness to HEX is present in Cushing's disease with micro-, but not macro- ACTH-secreting pituitary adenoma. This finding agrees with other evidence pointing toward differences in the hormonal behavior between micro- and ACTH-secreting pituitary macroadenomas. 相似文献
182.
183.
H Sawert E Girardi G Antonucci MC Raviglione P Viale G Ippolito 《Canadian Metallurgical Quarterly》1998,158(19):2112-2121
184.
185.
The electrochemical and corrosion behaviour of a nickel base super alloy (C-263) has been investigated in the deaerated binary and ternary solution mixture of concentrated phosphoric acid, acetic acid, sulphuric acid, nitric acid or water using potentiostatic technique at 35°C. The possibilities of electropolishing of this alloy in these solution mixtures have been also explored. The alloy showed distinct active, passive and transpassive behaviour in the experimental solutions. The alloy remained active and turned passive in the negative potential region. Transpassive dissolution of the alloy is observed and electropolishing is achieved in this region. The best electropolishing is obtained in 50% H3PO4 + 40% CH3COOH + 10% H2SO4. Higher content of water in the electrolytic solution is not useful for electropolishing of the alloy The experimental results also suggest that a current plateau in the transpassive potential region is not a sufficient condition to achieve electropolishing. 相似文献
186.
Several in vivo and in vitro methods for monitoring immunological properties of two allergoids obtained by formaldehyde treatment of ovalbumin (OA) were developed. The calculated molecular weight of allergoids was 80 kD (OA-F1) and 165 kD (OA-F2), respectively. The allergenic activity in vitro of allergoids in mast-cell histamine release assay was 1000 times lower than of OA. Both allergoids showed reduced ability to induce passive cutaneous anaphylaxis in the Sprague-Dawley rats or systemic anaphylaxis in Dunkin-Harley guinea-pigs. The ability of OA and allergoids to bind to the OA-specific IgE antibodies was measured in vivo by the inhibition of passive cutaneous anaphylaxis (PCA-inhibition). Allergoid binding to IgE was 51-66% lower than the native allergen. Moreover, the avidity of OA-specific IgG antibodies, measured by ELISA-inhibition, for allergoids and allergen was of the same order. Allergoids induced a different pattern of humoral immune response from that, induced by the native allergen. Thus, after immunization of BALB/c mouse, both allergoids induced a higher production of IgG and a lower production of IgE than OA, only OA-F2 induced a lower production of IgG1. The differences in the IgA response to the immunogens was not significant. Delayed hypersensitivity studies in the BALB/c mouse showed that allergoids were 5- to 12-times less effective in inducing a cell-mediated immune response than OA. The present study provides a battery of immunological methods for preclinical testing of modified allergens. 相似文献
187.
188.
189.
Closed-loop expressions for the minimum energy control of a single-input linear digital system are described. They are obtained by two different methods. The optimal inputs are given by state feedback with the bounded variable gains. The gains are independent of the initial state of the system 相似文献
190.
Catastrophic convolutional codes (CC) cause an infinite number of decoded data bit errors when decoding a finite number of code symbols. A CC displays a catastrophic error propagation if the generating polynomials have a common factor. An efficient algorithm for polynomial factorization in GF(2m) is used for detecting catastrophic CC for any rate n/m and constraint length k. A general formula is derived to calculate the number of catastrophic codes in any (m, n, k) CC. 相似文献