全文获取类型
收费全文 | 4636篇 |
免费 | 60篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 42篇 |
综合类 | 2篇 |
化学工业 | 341篇 |
金属工艺 | 39篇 |
机械仪表 | 49篇 |
建筑科学 | 82篇 |
矿业工程 | 6篇 |
能源动力 | 67篇 |
轻工业 | 259篇 |
水利工程 | 10篇 |
石油天然气 | 23篇 |
无线电 | 229篇 |
一般工业技术 | 330篇 |
冶金工业 | 3023篇 |
原子能技术 | 15篇 |
自动化技术 | 181篇 |
出版年
2022年 | 13篇 |
2021年 | 24篇 |
2020年 | 26篇 |
2019年 | 31篇 |
2018年 | 29篇 |
2017年 | 35篇 |
2016年 | 41篇 |
2015年 | 18篇 |
2014年 | 30篇 |
2013年 | 82篇 |
2012年 | 69篇 |
2011年 | 92篇 |
2010年 | 57篇 |
2009年 | 71篇 |
2008年 | 72篇 |
2007年 | 61篇 |
2006年 | 44篇 |
2005年 | 47篇 |
2004年 | 65篇 |
2003年 | 57篇 |
2002年 | 37篇 |
2001年 | 31篇 |
2000年 | 41篇 |
1999年 | 139篇 |
1998年 | 999篇 |
1997年 | 596篇 |
1996年 | 328篇 |
1995年 | 226篇 |
1994年 | 174篇 |
1993年 | 198篇 |
1992年 | 36篇 |
1991年 | 47篇 |
1990年 | 45篇 |
1989年 | 49篇 |
1988年 | 53篇 |
1987年 | 41篇 |
1986年 | 36篇 |
1985年 | 38篇 |
1984年 | 31篇 |
1983年 | 24篇 |
1982年 | 39篇 |
1981年 | 48篇 |
1980年 | 33篇 |
1979年 | 27篇 |
1978年 | 28篇 |
1977年 | 87篇 |
1976年 | 162篇 |
1975年 | 17篇 |
1974年 | 19篇 |
1973年 | 15篇 |
排序方式: 共有4698条查询结果,搜索用时 183 毫秒
91.
92.
O van der Heijden HC Chiu TC Park H Takahashi VA LiVolsi JI Risinger JC Barrett A Berchuck AC Evans K Behbakht AW Menzin PC Liu I Benjamin MA Morgan SA King SC Rubin J Boyd 《Canadian Metallurgical Quarterly》1998,23(4):243-247
The degree and nature of patient involvement in consultations with health professionals influences problem and needs recognition and management, and public accountability. This paper suggests a framework for understanding the scope for patient involvement in such consultations. Patients are defined as co-producers of formal health services, whose potential for involvement in consultations depends on their personal rights, responsibilities and preferences. Patients' rights in consultations are poorly defined and, in the National Health Service (NHS), not legally enforceable. The responsibilities of patients are also undefined. I suggest that these are not to deny, of their own volition, the rights of others, which in consultations necessitate mutuality of involvement through information-exchange and shared decision-making. Preferences should be met insofar as they do not militate against responsibilities and rights. 相似文献
93.
The purpose of this study was to investigate platelet effects on postischemic heart function in conjunction with adenosine effects on intracoronary platelet adhesion. Homologous platelets were infused into the coronaries of isolated guinea pig hearts, either during low-flow ischemia or during reperfusion, and external heart work (EHW) and intracoronary platelet adhesion were determined. In most experiments, thrombin was added to the perfusate. The influence of endogenous adenosine was studied by use of the uptake blocker dipyridamole and the unspecific adenosine-receptor blocker theophylline, the A1-receptor blocker 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), and the A2-receptor blocker 3,7-dimethyl-1-propargylxanthine (DMPX). The importance of nitric oxide and prostaglandin I2 (PGI2) was tested by using nitro-L-arginine (NOLAG) and indomethacin, respectively. When platelets were applied with thrombin during low-flow ischemia, EHW recovered to only 63 +/- 4% of the preischemic value, as compared with 89 +/- 3% without platelets (p < 0.05). Despite thrombin, platelets incurred no significant functional loss when applied in the first minute of reperfusion (but again in the fifth minute); however, when theophylline was also present, recovery of EHW amounted to only 42 +/- 12%. Intracoronary adhesion of platelets was negligible without thrombin, and highest during low-flow ischemia with thrombin (35 +/- 3% of the applied number). No adhesion occurred during the first minute of reperfusion, whereas in the fifth minute, adhesion was again 20.8 +/- 4%. Dipyridamole increased adenosine release and attenuated adhesion at this time. Theophylline increased adhesion in the first minute of reperfusion (33 +/- 6.4%), whereas NOLAG and indomethacin proved to be ineffective. DPCPX and DMPX each increased platelet retention during the first minute of reperfusion, their effects being additive. Intracoronary adhesion of platelets induced by thrombin in isolated hearts can reduce postischemic recovery of heart function. During reperfusion, but not during low-flow, endogenous adenosine can prevent platelet adhesion and loss of myocardial function, an action mediated both by A1- and A2-receptor-dependent mechanisms. 相似文献
94.
P Barrett G Davidson DG Hazlerigg MA Morris AW Ross PJ Morgan 《Canadian Metallurgical Quarterly》1998,139(1):163-171
95.
An 84-year-old male presented to the emergency room with the chief complaint of painful, swollen penis following the use of a constriction ring to maintain penile erection. A high fever, chills and hypotension were recognized. Septic shock was presumed, and administration of antibiotics was started. Microbiologic cultures revealed Escherichia coli in blood. We herein report a rare but serious complication accompanying incarceration of the penis. 相似文献
96.
1. The spontaneously hypertensive rat (SHR) exhibits a lower bodyweight in utero and an exaggerated salt appetite post partum. To determine whether salt appetite is affected by the perinatal environment, we measured the salt appetite of embryo-cross-transferred SHR and Wistar Kyoto (WKY) rats at maturity. 2. One-cell embryos were collected from the oviducts of donor rats and transferred into the oviducts of recipients through the infundibulum. The salt appetite of the resultant female offspring for 0.10 and 0.15 mol/L saline was measured at 20-30 weeks of age. 3. Salt intake of SHR gestated in WKY rats was significantly lower than that of SHR gestated in SHR, while that of WKY rats gestated in SHR was higher than that of WKY rats gestated in WKY rats. 4. Therefore, some maternal factor plays a role in the development of the exaggerated salt appetite of the SHR. This factor is also able to affect the later salt appetite of WKY rat offspring born to SHR surrogates. 相似文献
97.
98.
Urinary tract abnormalities are fairly common in the perinatal period. Ultrasonography is an effective diagnostic tool for identifying fetal urinary tract anomalies and can be helpful in establishing prognosis and guiding treatment decisions. The sonographer is encouraged to characterize and localize the fetal urinary tract abnormality when identified. In doing so, the correct diagnosis can be selected from the differential possibilities, providing vital clinical information needed to develop a care plan for both the pregnant woman and her fetus. 相似文献
99.
In a duplicate study during 1987-1991, 478 24-h duplicate samples from 14 homes for elderly people and 10 homes for youth were investigated for their contents of selected harmful substances. The analyses covered 45 active substances of pesticides, 17 PCB-congeners as well as lead, cadmium, and nitrate contents. Pesticides could be detected only in 15% of the investigated samples. The pesticide contents reached max. 8% of the respective FAO/WHO-limits. As the mean intake of the three most important PCB-congeners (sum of the congeners 138, 153, and 180) values of 0.9 and 1.1 micrograms per day and ration or person, respectively, were found. Also in the worst case the daily PCB intake was below the recommended ADI value of the FDA of 1 microgram/kg of body weight. The daily nutritional intake of lead and cadmium via the investigated daily rations reached about 5.6% and 20% of the Provisionally Tolerably Weekly Intake values of the FAO/WHO. The mean nitrate content of the duplicate portions was 101 mg per day and person (median: 79 mg per day and person). Referred to the median value the WHO limit (3.65 mg/kg body weight and day) was exhausted to about 36%. 相似文献
100.
The molecular basis for the profound inflammatory response and the accumulation of hyaluronan in orbital connective tissues seen in thyroid-associated ophthalmopathy is unknown. Moreover, the link between the orbital manifestations of Graves' disease and those in the pretibial skin, localized dermopathy, has yet to be established. We have reported recently that leukoregulin, an activated T lymphocyte-derived cytokine, dramatically induces hyaluronan synthesis and prostaglandin-endoperoxide H synthase 2 in human orbital fibroblasts in culture. In the current studies, utilizing giant two-dimensional gel electrophoresis, we find that orbital fibroblasts express constitutively a protein profile that distinguishes them from skin fibroblasts derived from the abdominal wall and from the pretibium. We further demonstrate that leukoregulin, when present in culture medium for 16 hr, up-regulates a set of orbital fibroblast proteins not present in untreated cultures or in fibroblasts from the abdominal wall. However, some of the same protein inductions are present in the pretibial fibroblasts. These leukoregulin-induced changes in protein expression are completely blocked by dexamethasone (10 nM). Our findings are the first to identify proteins that appear to be expressed and differentially regulated in an anatomical site-restricted manner in orbital and pretibial fibroblasts and seem to establish a molecular link between fibroblasts from the orbit and those in pretibial skin. 相似文献