全文获取类型
收费全文 | 186214篇 |
免费 | 2825篇 |
国内免费 | 1001篇 |
专业分类
电工技术 | 3639篇 |
综合类 | 482篇 |
化学工业 | 29420篇 |
金属工艺 | 8282篇 |
机械仪表 | 5727篇 |
建筑科学 | 4906篇 |
矿业工程 | 1046篇 |
能源动力 | 4984篇 |
轻工业 | 16821篇 |
水利工程 | 1850篇 |
石油天然气 | 3422篇 |
武器工业 | 32篇 |
无线电 | 21202篇 |
一般工业技术 | 34814篇 |
冶金工业 | 33955篇 |
原子能技术 | 4379篇 |
自动化技术 | 15079篇 |
出版年
2021年 | 1640篇 |
2019年 | 1513篇 |
2018年 | 2358篇 |
2017年 | 2336篇 |
2016年 | 2438篇 |
2015年 | 1913篇 |
2014年 | 3122篇 |
2013年 | 8358篇 |
2012年 | 5089篇 |
2011年 | 6936篇 |
2010年 | 5518篇 |
2009年 | 6390篇 |
2008年 | 6309篇 |
2007年 | 6278篇 |
2006年 | 5405篇 |
2005年 | 5062篇 |
2004年 | 4734篇 |
2003年 | 4392篇 |
2002年 | 4349篇 |
2001年 | 4360篇 |
2000年 | 4121篇 |
1999年 | 4311篇 |
1998年 | 10640篇 |
1997年 | 7590篇 |
1996年 | 5825篇 |
1995年 | 4436篇 |
1994年 | 3747篇 |
1993年 | 3664篇 |
1992年 | 2694篇 |
1991年 | 2611篇 |
1990年 | 2474篇 |
1989年 | 2499篇 |
1988年 | 2432篇 |
1987年 | 2170篇 |
1986年 | 2101篇 |
1985年 | 2409篇 |
1984年 | 2215篇 |
1983年 | 2032篇 |
1982年 | 1913篇 |
1981年 | 1965篇 |
1980年 | 1812篇 |
1979年 | 1827篇 |
1978年 | 1787篇 |
1977年 | 2127篇 |
1976年 | 2706篇 |
1975年 | 1562篇 |
1974年 | 1566篇 |
1973年 | 1617篇 |
1972年 | 1356篇 |
1971年 | 1270篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
993.
We have verified that chemotaxis of isolated human polymorphonuclear leukocytes (PMN) was a target of in vitro toxicant effect of acrylonitrile (ACN). This toxicant induced a significant dose dependent decreasing of chemotaxis with 50% inhibition (IC50) occurring at 15 mM. We assume that PMN from workers exposed to ACN reacts vivo in a similar way to PMN exposed in vitro to ACN. We propose therefore to use chemotaxis assay as a biomarker of early biological effect of ACN in workers, since for their monitoring there are so far only internal dose indicators but no suitable effect indicators. 相似文献
994.
995.
Y Panis J Belghiti D Valla JP Benhamou F Fékété 《Canadian Metallurgical Quarterly》1994,115(3):276-281
BACKGROUND: In Budd-Chiari syndrome (BCS) treated by portosystemic shunt, postoperative shunt thrombosis is associated with high morbidity and mortality rates. The aim of this study was to determine factors associated with shunt thrombosis. METHODS: From 1985 to 1991, 25 patients underwent portosystemic shunt for BCS. According to the patency of the shunt during the postoperative period and follow-up, patients were divided into two groups including 17 patients with patent shunt and 8 (32%) with shunt thrombosis. RESULTS: In patients with patent shunt, actuarial survival rate at 5 years was 87% versus 38% in patients with shunt thrombosis (p < 0.05). Duration of symptoms before operation was higher in patients with shunt thrombosis than in patients with patent shunt (315 +/- 483 vs 109 +/- 168 days, p < 0.05). In patients with patent shunt, extensive fibrosis or cirrhosis was observed in 3 of 17 (18%) versus in 5 of 8 (63%) of patients with shunt thrombosis (p < 0.05). Shunt thrombosis was observed in 3 of 3 patients (100%) with the combination of myeloproliferative disorder, duration of symptoms more than 100 days, and cirrhosis versus 0 of 6 (0%) patients without this combination (p < 0.05). CONCLUSIONS: In acute form of BCS (with short history of the disease and absence of extensive fibrosis or cirrhosis), early portal decompression is mandatory, with low risk of shunt thrombosis and good long-term results. In chronic form of BCS, the risk of shunt thrombosis is high and long-term results are bad; in these patients, orthotopic liver transplantation must be considered. 相似文献
996.
997.
998.
F. Devaux N. Souli A. Ougazzaden F. Huet M. Carre 《Photonics Technology Letters, IEEE》1996,8(2):218-220
We report on a tandem of electroabsorption modulators integrated with an amplifier by the identical active layer (IAL) approach. A 14 dB fiber-to-fiber is obtained by the use of constant As-P ratio MQW active layer and operation at 10 Gb/s is demonstrated. A record modulator saturation power of 35 mW is also reported. 相似文献
999.
The aim this study was to report findings on the concentrations of mean triiodothyroxine (T3), thyroxin (T4), thyroid stimulating hormone (TSH) and prolactin (Prl) in patients with benign mastopathy and in control group. All of the examined subjects were clinically euthyroid. The mean T4 concentrations in women with mastopathy (78.25 +/- 15.27 ng/ml) were significantly lower than in control group 88.73 +/- 15.27). The mean TSH and PRL concentration in women with mastopathy were higher, but not significantly, than in control women. This results indicate, that benign mastopathy seems to be connected with thyroid functions. 相似文献
1000.
OBJECTIVE: Percutaneous transluminal angioplasty of stenoses of the renal artery can be used to treat hypertension and renal insufficiency. Although many studies have been published on the short-term results of this procedure, few long-term studies are available. SUBJECTS AND METHODS: One hundred ninety-five patients (123 men and 72 women 19-79 years old; mean age, 56 years) with stenosis of the renal artery and hypertension underwent renal percutaneous transluminal angioplasty at our institution. The stenosis was unilateral in 66% of patients, bilateral in 26%, and in a solitary functioning kidney in 8%. Renal insufficiency was present in 31% of patients. After renal percutaneous transluminal angioplasty, long-term clinical and angiographic follow-up was evaluated by life-table analysis. RESULTS: In patients with fibromuscular disease, blood pressure returned to normal in 57%, improved in 21%, and was unchanged in 21%. In patients with atherosclerotic stenosis, blood pressure returned to normal in 12%, improved in 51%, and was unchanged in 37%. After percutaneous transluminal angioplasty, renal function improved in 48% of patients with renal insufficiency due to bilateral stenosis or stenosis in the single functioning kidney, whereas none of the patients with unilateral stenosis of renal artery and renal insufficiency had any notable improvement. Long-term follow-up showed a high rate (82%) of patency of revascularized arteries and a low rate (21%) of hypertension recurrence at 5 years. CONCLUSION: Renal percutaneous transluminal angioplasty is useful for treating hypertension and for reestablishing renal function. Its effects on blood pressure and renal function are long-lasting in the large majority of patients. 相似文献