全文获取类型
收费全文 | 1780篇 |
免费 | 8篇 |
专业分类
电工技术 | 5篇 |
综合类 | 1篇 |
化学工业 | 80篇 |
金属工艺 | 3篇 |
机械仪表 | 2篇 |
建筑科学 | 5篇 |
能源动力 | 2篇 |
轻工业 | 43篇 |
无线电 | 35篇 |
一般工业技术 | 50篇 |
冶金工业 | 1499篇 |
自动化技术 | 63篇 |
出版年
2021年 | 4篇 |
2018年 | 4篇 |
2016年 | 9篇 |
2015年 | 6篇 |
2014年 | 5篇 |
2013年 | 12篇 |
2012年 | 17篇 |
2011年 | 11篇 |
2010年 | 13篇 |
2009年 | 12篇 |
2008年 | 11篇 |
2007年 | 13篇 |
2006年 | 8篇 |
2005年 | 5篇 |
2004年 | 11篇 |
2003年 | 16篇 |
2002年 | 9篇 |
2001年 | 7篇 |
2000年 | 7篇 |
1999年 | 60篇 |
1998年 | 490篇 |
1997年 | 235篇 |
1996年 | 166篇 |
1995年 | 102篇 |
1994年 | 68篇 |
1993年 | 76篇 |
1992年 | 28篇 |
1991年 | 21篇 |
1990年 | 19篇 |
1989年 | 21篇 |
1988年 | 19篇 |
1987年 | 16篇 |
1986年 | 29篇 |
1985年 | 22篇 |
1984年 | 11篇 |
1983年 | 13篇 |
1982年 | 15篇 |
1981年 | 14篇 |
1980年 | 11篇 |
1979年 | 6篇 |
1978年 | 9篇 |
1977年 | 35篇 |
1976年 | 65篇 |
1975年 | 6篇 |
1974年 | 7篇 |
1972年 | 4篇 |
1971年 | 3篇 |
1969年 | 6篇 |
1964年 | 3篇 |
1963年 | 3篇 |
排序方式: 共有1788条查询结果,搜索用时 0 毫秒
51.
52.
A dental student developed swelling of the lips and peri-oral urticaria, immediately after placement of a dental rubber dam during a chairside demonstration of clinical dentistry. A provisional diagnosis of a Type I hypersensitivity reaction to natural rubber latex was made and an appointment organised for specialist investigations. The student reported an atopic history and allergy to peanuts. A Radioallergosorbent Test (RAST), to measure Ig-E antibodies to latex, was positive. The dental student was given advice concerning the avoidance of natural rubber latex. Dental staff must be aware of potentially serious reactions to natural rubber latex in the dental surgery. 相似文献
53.
Interleukin-2 (IL-2) therapy often causes gastrointestinal side effects and at least 8 cases of bowel perforation have been reported. The patient reported here developed a colosplenic fistula, diagnosed by CT, with no neoplastic involvement of these organs. Awareness of these complications of IL-2 can help lead to earlier diagnosis. 相似文献
54.
FR Lima AG Trentin D Rosenthal C Chagas V Moura Neto 《Canadian Metallurgical Quarterly》1997,154(1):167-175
Degradation and utilization of protein by Prevotella ruminicola B1(4), a proteolytic bacterium that is prominent in the rumen, was examined. In preliminary experiments, proteinaceous N sources produced faster growth rates than did NH4Cl, based on changes in optical density over time. However, ammonium chloride produced a greater maximum cell density than did proteinaceous N sources. Of the proteinaceous N sources, an enzymatic hydrolysate of soybean protein with a relative peptide size of 3 AA residues produced a greater growth rate and maximum cell density compared with the other proteinaceous N sources. Further experiments revealed that P. ruminicola B1(4) grew faster and to a greater final dry weight with soybean protein than with casein. Degradation of both proteins was low as was indicated by the slow disappearance of soluble protein, low concentrations of free AA and peptides, and the decrease in ammonia concentrations over time. Patterns of degradation did differ between the two proteins, however. Accumulation of peptides and free AA from soybean protein peaked 2 h earlier than those from casein, and concentrations of free AA and peptides from soybean protein were lower on average than those from casein. Prevotella ruminicola B1(4) preferentially utilized Asp, Ile, Leu, Lys, and Arg from soybean protein compared with casein. The relative size of peptides that accumulated from both proteins, as determined by the ratio of ninhydrin reaction after HCl hydrolysis to ninhydrin reaction before HCl hydrolysis, suggested that part of the proteolytic activity of P. ruminicola B1(4) is a dipeptidase. Our findings suggest that P. ruminicola may have a greater impact on peptide degradation than on protein degradation in the rumen. 相似文献
55.
MF Chen YY Jan CS Wang TL Hwang LB Jeng SC Chen TC Chao 《Canadian Metallurgical Quarterly》1997,84(9):1229-1232
The effect of phenylephrine-induced reflex parasympathetic stimulation on QT interval and its dispersion was studied in 16 healthy subjects with a history of paroxysmal supraventricular tachycardia, both during sinus rhythm and during atrial pacing. Results demonstrate that rapid reflex parasympathetic stimulation does not influence QT interval duration or QT dispersion, and also emphasize the inappropriateness of Bazett's formula, the need for comparison of QT intervals during identical heart rates, and the importance of analyzing all 12 leads of a standard electrocardiogram when assessing the effects of various interventions on the QT interval. 相似文献
56.
The microstructure and mechanical properties of melt-spun isotactic polypropylene (iPP) fibers were studied for different take-up velocities and throughputs with a combination of small- and wide-angle X-ray scattering, calorimetry and tensile tests. With the increase of take-up velocity the mesomorphic fraction of the fibers steadily decreases while the crystalline fraction increases. The addition of an alpha-nucleating agent led to an increase of crystallinity and a slight decrease of the orientation factor. By contrast, a beta-nucleator resulted in a complete suppression of the fiber crystallinity. The orientation factor of the mesophase and/or crystalline phase is found to have a one-to-one correlation with the fiber tenacity and deformation at break. At the same time, the absolute values of crystallinity and/or mesomorphicity are fully uncorrelated with these mechanical characteristics. The observed correlations can be used for example to design and control the fiber mechanical properties by tuning the processing conditions such as take-up velocity, throughput and addition of nucleating agents. 相似文献
57.
Niels J. Sijbrandi Ad J. Kimenai Edwin P.C. Mes René Broos Georg Bar Martin Rosenthal Yaroslav I. Odarchenko Dimitri A. Ivanov Jan Feijen Pieter J. Dijkstra 《Polymer》2012,53(19):4033-4044
Segmented poly(ether ester amide)s comprising glycine or β-alanine extended bisoxalamide hard segments are highly phase separated thermoplastic elastomers with a broad temperature independent rubber plateau. These materials with molecular weights, Mn, exceeding 30 × 103 g mol?1 are conveniently prepared by polycondensation of preformed bisester–bisoxalamides and commercially available PTHF diols. FT-IR revealed strongly hydrogen bonded and highly ordered bisoxalamide hard segments with degrees of ordering between 73 and 99%. The morphology consists of fiber-like nano-crystals randomly dispersed in the soft polymer matrix. The micro-structural parameters of the copolymers were addressed by simultaneous small- and wide-angle X-ray scattering. It is shown that the crystals have strictly identical thickness, which is close to the contour length of the hard segment. The long dimension of the crystals is identified with the direction of the hydrogen bonds. The melting transitions of the hard segments are sharp, with temperatures up to 170 °C. The studied polymers have an elastic modulus in the range of 139–170 MPa, a stress at break in the range of 19–31 MPa combined with strains at break of higher than 800%. The segmented copolymer comprising the β-alanine based bisoxalamide hard segment with a spacer of 6 methylene groups has a melting transition of 141 °C which is higher than the melting transition of its glycine analogue of 119 °C. Likewise, the fracture stress increased from 22 to 31 MPa when the glycine ester group in the hard segment was replaced with β-alanine. The improved thermal and mechanical properties of the latter polymers is related to the crystal packing of the β-alanine based hard segments in the copolymer compared to the packing of the hard segments comprising glycine ester groups. 相似文献
58.
We employ molecular dynamics simulations to investigate the self-assembly of amphiphilic Janus particles in a slit-pore consisting of two plane-parallel, soft walls. The Janus particles are modeled as soft spheres with an embedded unit vector pointing from the hydrophobic to the hydrophilic hemisphere. The structure formation is analyzed via cluster size distributions, density and polarization profiles, and in-plane correlation functions. At low temperatures and densities, the dominating structures are spherical micelles, whereas at higher densities we also observe wall-induced bilayer formation. Finally, we compare the MD results with those from a previous density functional study. 相似文献
59.
60.
We have previously described a model of outpatient integrated treatment for patients with comorbid psychoactive substance use disorders and schizophrenia (PSUD/S)(1). Here we review relevant literature on comorbidity and outline the rationale for integrated services. Further, we describe results from 3 related studies: First, we document the approximate incidence of PSUD among a heterogeneous group of 602 schizophrenic inpatient admissions to our hospital. Second, we describe in greater detail the psychiatric symptoms and patterns of substance abuse among a subsample of 106 inpatients with PSUD/S, contrasting them with 112 patients with PSUD and mixed psychotic disorders, but who are not schizophrenic. Third, we present a prospective research project and describe a sample of 30 patients with PSUD/S, detailing demographic characteristics, psychiatric symptoms and substance abuse history. Attention is given to current issues in the differential diagnosis of patients with PSUD/S using standardized instruments. 相似文献