全文获取类型
收费全文 | 318105篇 |
免费 | 3867篇 |
国内免费 | 880篇 |
专业分类
电工技术 | 5373篇 |
综合类 | 197篇 |
化学工业 | 51564篇 |
金属工艺 | 12699篇 |
机械仪表 | 9190篇 |
建筑科学 | 8558篇 |
矿业工程 | 2078篇 |
能源动力 | 7674篇 |
轻工业 | 28419篇 |
水利工程 | 3497篇 |
石油天然气 | 7258篇 |
武器工业 | 18篇 |
无线电 | 33422篇 |
一般工业技术 | 61712篇 |
冶金工业 | 57443篇 |
原子能技术 | 7824篇 |
自动化技术 | 25926篇 |
出版年
2021年 | 2447篇 |
2019年 | 2329篇 |
2018年 | 4131篇 |
2017年 | 4101篇 |
2016年 | 4398篇 |
2015年 | 2889篇 |
2014年 | 4926篇 |
2013年 | 14030篇 |
2012年 | 7968篇 |
2011年 | 10669篇 |
2010年 | 8651篇 |
2009年 | 9802篇 |
2008年 | 10239篇 |
2007年 | 10173篇 |
2006年 | 8969篇 |
2005年 | 8374篇 |
2004年 | 7760篇 |
2003年 | 7503篇 |
2002年 | 7557篇 |
2001年 | 7092篇 |
2000年 | 6762篇 |
1999年 | 6762篇 |
1998年 | 15286篇 |
1997年 | 11486篇 |
1996年 | 9128篇 |
1995年 | 7026篇 |
1994年 | 6406篇 |
1993年 | 6288篇 |
1992年 | 4920篇 |
1991年 | 4741篇 |
1990年 | 4686篇 |
1989年 | 4690篇 |
1988年 | 4603篇 |
1987年 | 4000篇 |
1986年 | 3941篇 |
1985年 | 4633篇 |
1984年 | 4404篇 |
1983年 | 4036篇 |
1982年 | 3840篇 |
1981年 | 3973篇 |
1980年 | 3741篇 |
1979年 | 3704篇 |
1978年 | 3753篇 |
1977年 | 4199篇 |
1976年 | 5277篇 |
1975年 | 3452篇 |
1974年 | 3233篇 |
1973年 | 3284篇 |
1972年 | 2792篇 |
1971年 | 2573篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
This article presents the results of a pilot-study conducted on a small sample of women with breast cancer and the members of their social support system. The purpose was to determine the potential link between the mental health of the breast cancer patient and their support system. Mental health was assessed with the SCL-90-R (Derogatis, 1977), a self-report scale composed of 90 items divided into nine categories, offering three global indicators of distress: the Global Severity Index (GSI); the Positive Symptom Distress Index (PSDI), and the Positive Symptom Total (PST). The SCL-90-R was distributed to a sample of 14 subjects: seven women treated for breast cancer and seven significant others (social support). The results led to the definition of symptoms such as hostility, phobic anxiety and psychosis specific to either the woman or the support system. 相似文献
82.
O. A. Ustrekhova T. G. Ezhikova-Babakhanova G. B. Basov 《Chemistry and Technology of Fuels and Oils》1993,29(11):544-548
Translated from Khimiya i Tekhnologiya Topliv i Masel, No. 11, pp. 17–18, 23, November, 1993. 相似文献
83.
B Antonsson DB Kassel G Di Paolo R Lutjens BM Riederer G Grenningloh 《Canadian Metallurgical Quarterly》1998,273(14):8439-8446
SCG10 is a neuron-specific, membrane-associated protein that is highly concentrated in growth cones of developing neurons. Previous studies have suggested that it is a regulator of microtubule dynamics and that it may influence microtubule polymerization in growth cones. Here, we demonstrate that in vivo, SCG10 exists in both phosphorylated and unphosphorylated forms. By two-dimensional gel electrophoresis, two phosphoisoforms were detected in neonatal rat brain. Using in vitro phosphorylated recombinant protein, four phosphorylation sites were identified in the SCG10 sequence. Ser-50 and Ser-97 were the target sites for protein kinase A, Ser-62 and Ser-73 for mitogen-activated protein kinase and Ser-73 for cyclin-dependent kinase. We also show that overexpression of SCG10 induces a disruption of the microtubule network in COS-7 cells. By expressing different phosphorylation site mutants, we have dissected the roles of the individual phosphorylation sites in regulating its microtubule-destabilizing activity. We show that nonphosphorylatable mutants have increased activity, whereas mutants in which phosphorylation is mimicked by serine-to-aspartate substitutions have decreased activity. These data suggest that the microtubule-destabilizing activity of SCG10 is regulated by phosphorylation, and that SCG10 may link signal transduction of growth or guidance cues involving serine/threonine protein kinases to alterations of microtubule dynamics in the growth cone. 相似文献
84.
M.E.W. Eggenkamp V. A. Shvarts R. Blaauwgeers A. Storm R. Jochemsen G. Frossati 《Journal of Low Temperature Physics》1998,110(1-2):299-304
This paper focuses on the hydrodynamics of third sound on a superfluid
3
He film. We solve the hydrodynamical equations in the limit of thick films with weak interaction with the substrate. The surface tension at the free interface is shown to have a large effect on the third sound velocity and on the attenuation for frequencies larger than 1Hz. In the case of a diffusely scattering substrate a ripplon-like dispersion relation is found for this frequency range. 相似文献
85.
A process-inherent NAND2 device is presented for a three-dimensional CMOS integration with epitaxial lateral overgrowth and chemo-mechanical polishing. The required 'OR' function of the two PMOS transistors is achieved by one silicon volume, which is controlled by a back gate and a conventional front gate. Almost symmetrical characteristics are measured for the front and the back gates.<> 相似文献
86.
87.
Data from the past few years have shown that as caffeine metabolizes solely in the liver, caffeine elimination can serve as a liver function test. We have collected data by monitoring 40 persons with liver diseases (11 chronic alcoholic hepatitis, 24 liver cirrhosis, 5 non-cirrhotic liver disease). Eight subjects served as controls. The patients with liver cirrhosis were classified according to the Child--Pugh scoring system. To determine caffeine elimination blood samples were collected before and at 3, 6, 9 and 12 hours after oral administration of 0.2 g caffeine. Fasting serum caffeine concentration and concentration 12 hours after administration, serum clearance, half life, peak concentration and volume of distribution have been compared. The respective values measured in patients with non-cirrhotic liver diseases did not differ significantly from the controls. The disappearance of caffeine was significantly decreased in cirrhotics. Our results demonstrated a good correlation between impairment of caffeine elimination and assessment of severity of liver disease by the Child--Pugh classification. Measuring serum levels in samples taken 12 hours after caffeine administration is a simple and useful method in the diagnosis of liver diseases at cirrhotic stage. 相似文献
88.
Within the framework of the distinction between episodic and semantic memory, it has been argued that these two memory systems are organised in a hierarchical way. The hierarchical hypothesis assumes that episodic memory is a specific subsystem of semantic memory and therefore implies that episodic memory cannot exist without semantic memory. If this hypothesis is correct, it should be expected that patients with impaired semantic memory also have impaired episodic memory. In the present study, two experiments investigated the influence of semantic encoding on recognition memory performance in a population of 20 patients with Alzheimer's disease and 18 normal controls. Both experiments assessed recognition memory for semantically-related items. In Experiment 2, but not in Experiment 1, subjects were explicitly instructed to make a semantic association between the items. Alzheimer's disease patients were impaired, compared to the normal controls, on the recognition memory performance of both experiments. The ability to make a semantic association between two items was significantly and positively correlated with the subjects' performance on the recognition tasks. A further analysis showed that patients who were impaired on the semantic association task did significantly worse on the recognition task of Experiment 2 than normal controls and patients who were unimpaired on the semantic association task. These findings are discussed in the context of memory deficits in Alzheimer's disease, and are interpreted as supporting the view that episodic memory for an item is affected by the level of semantic awareness of that same item. 相似文献
89.
T P?usa P Górski H Frank-Piskorska M Kowalski J Kruszewski P Kuna M Kurek R Kurzawa W Silny E Zawisza 《Canadian Metallurgical Quarterly》1996,1(4):292-293
A review of isolates of Neisseria meningitidis and other laboratory evidence of meningococcal infection was carried out for the period 1990-1995. Thirty-three patients with evidence of meningococcal disease were identified over the six year period. Group B organisms were the most commonly identified, but an increase in Group C has occurred and is almost equal in number. Data from clinical, laboratory and public health sources should be centralized in a National Surveillance Centre. 相似文献
90.
Thanapalan Murugesan G. S. Venkat Rathnam S. Panduranga Rao P. Gangadhar Rao 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,63(3):290-294
In the present study of gas–liquid contactors, mean residence/contact time was calculated from knowledge of superficial velocity and the gas phase hold-up, for various gas rates and impeller geometry and speeds, and compared with values obtained from RTD measurements. A new correlation, involving Flow Number, Froude Number, system geometry and the physical properties, is proposed. This uses the authors data and those available in literature. 相似文献