全文获取类型
收费全文 | 3825篇 |
免费 | 20篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 15篇 |
化学工业 | 163篇 |
金属工艺 | 5篇 |
机械仪表 | 15篇 |
建筑科学 | 19篇 |
能源动力 | 18篇 |
轻工业 | 80篇 |
水利工程 | 13篇 |
石油天然气 | 1篇 |
无线电 | 77篇 |
一般工业技术 | 99篇 |
冶金工业 | 3271篇 |
原子能技术 | 11篇 |
自动化技术 | 59篇 |
出版年
2023年 | 4篇 |
2022年 | 28篇 |
2021年 | 33篇 |
2020年 | 12篇 |
2019年 | 12篇 |
2018年 | 18篇 |
2017年 | 9篇 |
2016年 | 11篇 |
2015年 | 20篇 |
2014年 | 20篇 |
2013年 | 40篇 |
2012年 | 36篇 |
2011年 | 23篇 |
2010年 | 25篇 |
2009年 | 25篇 |
2008年 | 38篇 |
2007年 | 19篇 |
2006年 | 26篇 |
2005年 | 14篇 |
2004年 | 22篇 |
2003年 | 30篇 |
2002年 | 12篇 |
2001年 | 9篇 |
2000年 | 10篇 |
1999年 | 133篇 |
1998年 | 1057篇 |
1997年 | 627篇 |
1996年 | 400篇 |
1995年 | 189篇 |
1994年 | 199篇 |
1993年 | 191篇 |
1992年 | 34篇 |
1991年 | 16篇 |
1990年 | 25篇 |
1989年 | 28篇 |
1988年 | 30篇 |
1987年 | 26篇 |
1986年 | 17篇 |
1985年 | 22篇 |
1984年 | 4篇 |
1983年 | 9篇 |
1982年 | 25篇 |
1981年 | 20篇 |
1980年 | 23篇 |
1978年 | 8篇 |
1977年 | 86篇 |
1976年 | 168篇 |
1975年 | 3篇 |
1973年 | 2篇 |
1965年 | 2篇 |
排序方式: 共有3846条查询结果,搜索用时 7 毫秒
21.
MM Simon P Pavlik A Hartig M Binder H Ruis WJ Cook CL Denis B Schanz 《Canadian Metallurgical Quarterly》1995,249(3):289-296
We examined the hypoxic tolerance phenomenon in vitro. Brief exposure to hypoxia induced the production of basic fibroblast growth factor (bFGF) mRNA and protein in rat cortical neurons and protected them from hypoxic injury. Cortical neurons were cultured from 18th-day rat embryos in a serum-free medium and subjected to brief (4 h) and/or prolonged (24 h) hypoxia. Neuronal damage was assessed by quantifying lactate dehydrogenase (LDH) activity in the medium. After brief hypoxia, LDH release was identical to that of the controls, whereas prolonged hypoxia caused a significant increase in LDH release, indicating neuronal death. However, if brief hypoxia was applied 2 days prior to the prolonged hypoxia, no increase in LDH release was observed. The bFGF mRNA expression was assessed with Northern blot and protein immunoreactivity with Western blot analysis. The brief period of hypoxia caused a 2.5-fold increase in bFGF mRNA and considerable bFGF protein expression 1 day later, but prolonged hypoxia caused increase in the expression of bFGF mRNA at 2 days and no protein expression until 3 days after the start of the hypoxia. When cells were subjected to prolonged hypoxia 2 days after brief hypoxia, however, no increase in bFGF mRNA was observed, while bFGF protein was expressed continuously. We also observed that exogenously applied bFGF reduced neuronal injury produced by prolonged hypoxia. The results obtained with this model suggest that brief hypoxia induces bFGF protein and thus tolerance to subsequent lethal hypoxia. Basic FGF might play a role as a tolerance-associated factor in this process. Thus, an in vitro model is useful for assessing the response of cortical neurons to hypoxic stress and for researching new factors related to ischemic tolerance. 相似文献
22.
Calcified and fibrotic coronary artery lesions cannot always be dilated with conventional balloon angioplasty even at high pressures. This study examines the success of excimer laser facilitated angioplasty in 38 lesions in 37 patients with lesions that failed balloon angioplasty alone. 相似文献
23.
MM Haglund MS Grady PM Kanev EG Pavlin TA Mayberg HR Winn 《Canadian Metallurgical Quarterly》1994,11(5):623-627
Using an illustrative case of severe closed head injury that resulted in a posterior fossa epidural hematoma (EDH) and supratentorial epidural/subdural hematomas (SDH), the massive blood losses associated with operative repair of the torn sigmoid sinus and the significant fluid losses associated with refractory diabetes insipidus were treated by the intraoperative use of the Rapid Infusion System (RIS, Haemonetics). The RIS can rapidly infuse warm blood, crystalloid, or colloid at rates up to 1.5 L/min, thereby limiting the commonly associated hypotension, hypothermia, and coagulopathies. During the suboccipital craniectomy for evacuation of the EDH and repair of the sigmoid sinus, the patient required 18 units of blood replacement secondary to a large tear in the sigmoid sinus. During a separate craniotomy for evacuation of the SDH, the patient also developed diabetes insipidus, which increased the operative fluid replacement to 39 L. Despite these massive blood and fluid losses, the RIS limited the hypotension to less than 2 min and prevented hypothermia and the frequently associated coagulopathies. When used in a neurosurgical setting associated with massive blood and/or fluid losses, the RIS accomplishes three important objectives: (1) rapid infusion of intravenous fluids for maintaining perfusion pressure, (2) rapid warming of fluids despite high intravenous infusion rates of cold crystalloids, thereby preventing intraoperative hypothermia, and (3) continuous monitoring of infusion rates and totals. 相似文献
24.
The stabilizing free energy of beta-trypsin was determined by hydrogen ion titration. In the pH range from 3.0 to 7.0, the change in free energy difference for the stabilization of the native protein relative to the unfolded one (delta delta G0 titration) was 9.51 +/- 0.06 kcal/mol. An isoelectric point of 10.0 was determined, allowing us to calculate the Tanford and Kirkwood electrostatic factor w. This factor presented a nonlinear behavior and indicated more than one type of titratable carboxyl groups in beta-trypsin. In fact, one class of carboxyl group with a pK = 3.91 +/- 0.01 and another one with a pK = 4.63 +/- 0.03 were also found by hydrogen ion titration of the protein in the folded state. 相似文献
25.
26.
27.
BA Lawrence J Polse A DePina MM Allen NH Kolodny 《Canadian Metallurgical Quarterly》1997,34(5):280-283
The identity of a number of phosphorus-containing metabolites present in Synechocystis sp. PCC 6308 has been confirmed by 31P NMR spectroscopy. The presence of D-ribulose 1,5-bisphosphate (RuBP); DL-glyceraldehyde 3-phosphate (GlyP); D(-)3-phosphoglyceric acid (3PGA); D-ribulose 5-phosphate (Ru5P);6-phosphogluconic acid (6PGA); phosphoenolpyruvate (PEP); inorganic phosphate (Pi); uridine diphosphoglucose (UDPG); ADP and ATP were demonstrated by the pH dependence of their 31P NMR chemical shifts in spectra of perchloric acid cell extracts. Intracellular pH of cells was determined to be 7.5-7.7. 相似文献
28.
大型水电工程需要大量的开挖隧洞,作者是负责印度国家水电公司(NHPC)所属的Tessta Ⅱ级水电工程的总工程师,现对印度在水电开发中的最新隧洞开挖工程做了一个展望。 相似文献
29.
30.
Three-stage treatment using a day hospital instead of a sanatorium with regards to the pattern of a tuberculosis process can achieve the results of closure of decay and abacillation cavities, which are not inferior to those with the conventional treatment, by reducing the basic regimen through the length of a hospital stage. The efficiency of two-stage treatment (day hospital--outpatient clinic) of lung tissue decay and culture-positive patients depends on the duration of the basic regimen, patient compliance, and the presence of a concomitant abnormality. 相似文献