全文获取类型
收费全文 | 2253篇 |
免费 | 53篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 14篇 |
综合类 | 1篇 |
化学工业 | 228篇 |
金属工艺 | 26篇 |
机械仪表 | 40篇 |
建筑科学 | 78篇 |
矿业工程 | 4篇 |
能源动力 | 24篇 |
轻工业 | 165篇 |
水利工程 | 10篇 |
石油天然气 | 1篇 |
武器工业 | 2篇 |
无线电 | 98篇 |
一般工业技术 | 249篇 |
冶金工业 | 1173篇 |
原子能技术 | 5篇 |
自动化技术 | 190篇 |
出版年
2022年 | 17篇 |
2021年 | 15篇 |
2020年 | 11篇 |
2019年 | 18篇 |
2018年 | 23篇 |
2017年 | 19篇 |
2016年 | 21篇 |
2015年 | 21篇 |
2014年 | 41篇 |
2013年 | 68篇 |
2012年 | 39篇 |
2011年 | 65篇 |
2010年 | 50篇 |
2009年 | 50篇 |
2008年 | 69篇 |
2007年 | 65篇 |
2006年 | 44篇 |
2005年 | 45篇 |
2004年 | 39篇 |
2003年 | 40篇 |
2002年 | 33篇 |
2001年 | 25篇 |
2000年 | 29篇 |
1999年 | 53篇 |
1998年 | 335篇 |
1997年 | 209篇 |
1996年 | 134篇 |
1995年 | 76篇 |
1994年 | 60篇 |
1993年 | 91篇 |
1992年 | 17篇 |
1991年 | 22篇 |
1990年 | 23篇 |
1989年 | 21篇 |
1988年 | 26篇 |
1987年 | 31篇 |
1986年 | 25篇 |
1985年 | 22篇 |
1984年 | 16篇 |
1983年 | 17篇 |
1982年 | 10篇 |
1981年 | 20篇 |
1980年 | 18篇 |
1979年 | 18篇 |
1978年 | 11篇 |
1977年 | 35篇 |
1976年 | 85篇 |
1975年 | 9篇 |
1974年 | 13篇 |
1973年 | 14篇 |
排序方式: 共有2308条查询结果,搜索用时 15 毫秒
31.
One impact of socioeconomic progress on populations has been to reduce the number of cases due to diseases of undernutrition and microbial contamination of food, which affected mostly infants and young children, and to increase those due to diseases of excessive food consumption, which are affecting adults and a growing number of children. This article reviews the main dietary factors which have an influence on cardiovascular disease and cancer, and discusses the link between economic development and increased rates of chronic diseases. There is evidence that the noncommunicable diseases and their risk factors have risen rapidly in countries of the WHO Western Pacific Region. Data from 29 countries and areas in the region indicate that 70% of them show lifestyle diseases in three or more of the top five causes of death. While public health measures have been implemented by some countries to prevent and control nutrition-related chronic diseases, further action is needed. 相似文献
32.
Predictive modelling of the 3-D structure of interleukin-13 总被引:1,自引:0,他引:1
Bamborough Paul; Duncan David; Richards W.Graham 《Protein engineering, design & selection : PEDS》1994,7(9):1077-1082
Several atomic structures are now available for the family ofhelical cytokines, which includes growth hormone as well asmany of the interleukins. Using structural information fromfive members of this family, two alternative models of interleukin(IL)-13 are proposed. IL-13 has biological properties similarto those of IL-4 and, like the other interleukins, is a potentiallyimportant pharmaceutical target. The model of IL-13 is discussedand compared with the known interleukin structures. 相似文献
33.
The postoperative radiographs of 35 patients who underwent impaction allografting of the proximal femur were reviewed. Of Gruen zones that could be clearly visualized, 39.9% contained areas where cement was absent. Even when an adequate mantle was present, cement voids were commonly seen. These cement mantle deficiencies were confirmed in a series of cadaveric impaction allografting procedures. They appear to be a consequence, at least in part, of an inadequate differential between trial and actual component sizes. Additionally, 4 patients were identified with significant component migration secondary to radiographically visible cement mantle fractures within the first 6 months of surgery. It is concluded that the surgical technique requires modification to ensure a more consistent cement mantle and clinical result. 相似文献
34.
The consistency of a family of least-squares estimates of some unknown parameters of a continuous-time linear stochastic system is verified. The unknown parameters appear affinely in the linear transformations of the state and the control. The method of verification of consistency associates a family of control problems to the identification problem, and the asymptotic behavior of the solutions of a family of algebraic Riccati equations from the control problems implies a persistent excitation property for the identification problem 相似文献
35.
36.
KC Halling BW Scheithauer AC Halling AG Nascimento SC Ziesmer PC Roche PC Wollan 《Canadian Metallurgical Quarterly》1996,106(3):282-288
OBJECTIVES--(1) to evaluate regional cerebral blood flow (rCBF) with single photon emission computed tomography and 99mTc-hexamethylpropyleneamine oxime in patients with the idiopathic adult hydrocephalus syndrome (IAHS); (2) to examine regional cerebral blood flow (rCBF), gait, and psychometric functions before and after CSF removal (CSF tap test); (3) to assess abnormalities in subcortical white matter by MRI. METHODS--Thirty one patients fulfilling the criteria for IAHS (according to history and clinical and neuroradiological examination) were studied. Quantified gait measurements, psychometric testing, and rCBF before and after removal of CSF were obtained. Pressure of CSF and CSF outflow conductance were investigated with a constant pressure infusion method. Brain MRI was used to quantify the severity of white matter lesions and periventricular hyperintensities. In IAHS a widespread rCBF hypoperfusion pattern was depicted, with a caudal frontal and temporal grey matter and subcortical white matter reduction of rCBF as the dominant feature. Removal of CSF was not accompanied by a concomitant increase in rCBF. Significant white matter lesions were detected only in a minority of patients by MRI. An altered CSF hydrodynamic state with a higher CSF pressure and lower conductance was confirmed. IAHS is characterised by an abnormal CSF hydrodynamic state, associated with a widespread rCBF reduction with preference for subcortical white matter and frontal-temporal cortical regions. Furthermore in most patients MRI did not show white matter changes suggestive of a coexistent subcortical arteriosclerotic encephalopathy. At least in the idiopathic group of patients with AHS, measurements of rCBF before and after temporary relief of the CSF hydrodynamic disturbance will not provide additional information that would be helpful in the preoperative evaluation but is suggestive of a preserved autoregulation of rCBF. 相似文献
37.
38.
An automatic calibration instrument was developed to improve the calibration accuracy of acoustic emission (AE) instrumentation. The instrument facilitates calibration by automatically displaying the maximum value of the stress used to produce AE calibration pulses and the AE pulse. A repeatable AE signal was generated by breaking a graphite rod on the test assembly. By measuring the breaking load of the rod and the maximum root-mean-square values of the resulting AE signals, a relative calibration of the AE measurement system was achieved. Low-noise amplifiers and filters were developed to improve the sensitivity of AE measurements by more than one order of magnitude over commercially available instruments; thus, the smaller signals obtained in parts testing can be detected 相似文献
39.
AE Barker-Griffith BW Streeten JL Abraham DP Schaefer SW Norton 《Canadian Metallurgical Quarterly》1998,105(3):535-538
PURPOSE: This study aimed to identify a dangerous new weapon capable of causing damage to the ocular and periocular regions. METHODS: The authors report two patients who had penetrating ocular injury in the past year because of homemade recreational potato guns. RESULTS: In one 14-year-old boy, projectiles from the firing of a potato gun resulted in orbital and cranial injuries that were life threatening with widespread fractures, marked disruption of facial structures, a cerebrospinal fluid fistula requiring bifrontal surgical repair, and loss of one eye. In a separate accident with a different potato gun, a 14-year-old boy who was wearing glasses at the time of injury had a sight-threatening perforating corneal laceration. CONCLUSION: Practitioners must be aware of the existence of these new, homemade unregulated devices. Information about the use and construction of these guns is widespread on the Internet, but no injuries resulting from these guns currently are documented in the medical literature. 相似文献
40.
TF Duffield D Sandals KE Leslie K Lissemore BW McBride JH Lumsden P Dick R Bagg 《Canadian Metallurgical Quarterly》1998,81(11):2866-2873
A total of 1010 dry cows and pregnant heifers was randomly selected from 25 dairy farms near Guelph, Ontario, Canada to receive either a controlled-release capsule of monensin or a placebo at 3 wk prior to expected calving. Serum samples were obtained at the time of treatment administration, and both serum and milk samples were collected at wk 1, 2, 3, 6, and 9 postcalving. The threshold used to define subclinical ketosis was selected a priori at a concentration of > or = 1200 mumol/L of beta-hydroxybutyrate. Using this threshold, the prevalence and incidence of subclinical ketosis were significantly reduced (50%) by monensin treatment. The duration of subclinical ketosis for cows that had been treated with monensin was also shorter than that for cows treated with the placebo. Monensin treatment significantly reduced the incidence of subclinical ketosis when the threshold was defined using higher concentrations of serum beta-hydroxybutyrate (1400 and 2000 mumol/L). In addition, monensin significantly reduced the prevalence of positive milk ketone tests. 相似文献