全文获取类型
收费全文 | 7002篇 |
免费 | 408篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 55篇 |
综合类 | 5篇 |
化学工业 | 1159篇 |
金属工艺 | 73篇 |
机械仪表 | 125篇 |
建筑科学 | 159篇 |
矿业工程 | 14篇 |
能源动力 | 128篇 |
轻工业 | 946篇 |
水利工程 | 53篇 |
石油天然气 | 18篇 |
无线电 | 178篇 |
一般工业技术 | 770篇 |
冶金工业 | 2925篇 |
原子能技术 | 20篇 |
自动化技术 | 788篇 |
出版年
2024年 | 19篇 |
2023年 | 59篇 |
2022年 | 98篇 |
2021年 | 184篇 |
2020年 | 172篇 |
2019年 | 157篇 |
2018年 | 237篇 |
2017年 | 234篇 |
2016年 | 262篇 |
2015年 | 177篇 |
2014年 | 219篇 |
2013年 | 433篇 |
2012年 | 316篇 |
2011年 | 297篇 |
2010年 | 239篇 |
2009年 | 260篇 |
2008年 | 194篇 |
2007年 | 221篇 |
2006年 | 110篇 |
2005年 | 112篇 |
2004年 | 99篇 |
2003年 | 101篇 |
2002年 | 68篇 |
2001年 | 43篇 |
2000年 | 31篇 |
1999年 | 122篇 |
1998年 | 931篇 |
1997年 | 571篇 |
1996年 | 355篇 |
1995年 | 212篇 |
1994年 | 159篇 |
1993年 | 196篇 |
1992年 | 33篇 |
1991年 | 31篇 |
1990年 | 32篇 |
1989年 | 32篇 |
1988年 | 29篇 |
1987年 | 26篇 |
1986年 | 27篇 |
1985年 | 22篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 17篇 |
1981年 | 17篇 |
1980年 | 29篇 |
1978年 | 6篇 |
1977年 | 63篇 |
1976年 | 131篇 |
1973年 | 4篇 |
1955年 | 4篇 |
排序方式: 共有7416条查询结果,搜索用时 961 毫秒
71.
Extended Hyperbolic Model for Sand-to-Concrete Interfaces 总被引:1,自引:0,他引:1
Jesús E. Gómez George M. Filz Robert M. Ebeling 《Canadian Metallurgical Quarterly》2003,129(11):993-1000
A relatively simple, four-parameter extended hyperbolic model for interfaces was developed for use in soil-structure interaction analyses. The model accommodates arbitrary stress path directions and includes three important elements: (1) development of a yield surface during interface shear; (2) a formulation for yield-inducing shear stiffness that is applicable to any stress path orientation; and (3) a formulation for unloading-reloading shear stiffness. The model was evaluated against the results of shear tests performed at the interface between three different types of sand and a concrete surface under a variety of stress paths. Comparisons between measured and calculated interface response indicate that the model provides accurate estimates of the response of sand-to-concrete interfaces. 相似文献
72.
Luciana Juncioni de Arauz Angela Faustino Jozala Gabriel Soares Pinheiro Priscila Gava Mazzola Adalberto Pessoa Júnior Thereza Christina Vessoni Penna 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(3):325-328
BACKGROUND: Nisin is a commercially available bacteriocin produced by Lactococcus lactis ATCC 11454 and used as a natural agent in the biopreservation of food. In the current investigation, milk whey, a byproduct from dairy industries was used as a fermentation substrate for the production of nisin. Lactococcus lactis ATCC 11454 was developed in a rotary shaker (30 °C/36 h/100 rpm) using two different media with milk whey (i) without filtration, pH 6.8, adjusted with NaOH 2 mol L?1 and without pH adjustment, both autoclaved at 121 °C for 30 min, and (ii) filtrated (1.20 µm and 0.22 µm membrane filter). These cultures were transferred five times using 5 mL aliquots of broth culture for every new volume of the respective media. RESULTS: The results showed that culture media composed of milk whey without filtration supplied L. lactis its adaptation needs better than filtrated milk whey. Nisin titers, in milk whey without filtration (pH adjusted), was 11120.13 mg L?1 in the second transfer, and up to 1628‐fold higher than the filtrated milk whey, 6.83 mg.L?1 obtained in the firstt transfer. CONCLUSIONS: Biological processing of milk byproducts (milk whey) can be considered a profitable alternative, generating high‐value bioproducts and contributing to decreasing river disposals by dairy industries. Copyright © 2008 Society of Chemical Industry 相似文献
73.
74.
Phenotypic analysis of antigen-specific T lymphocytes 总被引:4,自引:0,他引:4
JD Altman PA Moss PJ Goulder DH Barouch MG McHeyzer-Williams JI Bell AJ McMichael MM Davis 《Canadian Metallurgical Quarterly》1996,274(5284):94-96
Identification and characterization of antigen-specific T lymphocytes during the course of an immune response is tedious and indirect. To address this problem, the peptide-major histocompatability complex (MHC) ligand for a given population of T cells was multimerized to make soluble peptide-MHC tetramers. Tetramers of human lymphocyte antigen A2 that were complexed with two different human immunodeficiency virus (HIV)-derived peptides or with a peptide derived from influenza A matrix protein bound to peptide-specific cytotoxic T cells in vitro and to T cells from the blood of HIV-infected individuals. In general, tetramer binding correlated well with cytotoxicity assays. This approach should be useful in the analysis of T cells specific for infectious agents, tumors, and autoantigens. 相似文献
75.
P Uribe-Zú?iga G Hernández-Tepichín C del Río-Chiriboga V Ortiz 《Canadian Metallurgical Quarterly》1995,37(6):592-601
Since 1987 The National AIDS Council in Mexico (CONASIDA), has conducted research projects among female commercial sex workers (CSW), who are seen at the AIDS Information Centers. Through these studies, we have been able to find out how different issues influence commercial sex work in Mexico City. Since the beginning of our own studies in 1989, HIV prevalence in this particular group has remained low (0.04%-0.2%). Factors found to be associated with condom use were: educational level, not having children, more experience in sex work and younger age. Condom use was reported by 88% of the women; however, qualitative information and high STD prevalence rates suggest a much lower condom use. Mandatory HIV testing is not useful as a preventive measure among sex workers. Persuasive and structural interventions must be implemented in accordance with local and legal situations. 相似文献
76.
Gastric lesions induced by indomethacin (20 mg.kg-1 i.p.) and ethanol (1 ml 95% intragastrically) were studied in rats after a 24 hour fast. The size of gastric lesions was correlated with gastric HCl secretion and with gastric vascular permeability (determined from the Evan's blue concentration in the gastric tissue after its i.v. administration). These parameters were also studied in rats pretreated with either PGI2 (5 micrograms.kg-1) or dopamine (0.5 mg.kg-1). It was found that in 12-months old rats the gastric lesions were significantly higher compared with the 3-month old group. PGI2 and dopamine significantly decreased gastric lesions in the 3-month rats but not in 12-month old rats. Both indomethacin and ethanol increased gastric vascular permeability in both age groups. It was observed that the decrease of gastric lesions after pretreatment with PGI2 and dopamine in the 3-month old rats was followed with decreased gastric vascular permeability and HCl secretion. On the other hand the increased susceptibility of the gastric mucosa due to indomethacin in the 12-month old rats was followed by a decrease of HCl secretion. PGI2 or dopamine had any effect on the 12-month old rats. These results show that susceptibility of gastric mucosa to PGI2 and dopamine is dependent on age. (Fig. 3, Ref. 31.) 相似文献
77.
MG Niemia?towski FN Toka E Malicka Gieryńska I Spohr de Faundez A Schollenberger 《Canadian Metallurgical Quarterly》1996,44(5-6):373-378
An 11-year global WHO campaign for eradication of smallpox finished in October 1977 as the result of Edward Jenner's primary success in 1796, who for the first time applied human vaccination against variola virus (VARV). The 200th anniversary of this happening is a good occasion to summarize the current status of the knowledge about the role of B and T lymphocytes in the control of orthopoxvirus infections. This short review concentrates on general characteristics of orthopoxviruses and the immune response to infection, mainly by vaccinia virus (VV) and ectromelia virus (EV). 相似文献
78.
Presentation of our experience in three cases of urocolpos (acquired pudendal lip fusion), a series numerically equivalent to the total number of cases published until now. All patients in our series were older women and presented complete fusion of the small pudendal lips, with only a small pointed puncture in the lower part of the vulva. The main clinical signs and symptoms in our series were: urinary infection in 100%, false incontinence in 66% due to output of urine retained in the vagina, a symptom that has not been described earlier, and acute urine retention in 33%. All patients were successfully treated by means of surgical loosening of the fusioned lips and application of topical estrogens. An analysis is made of clinical and pathoanatomical features which differentiate this entity from the sclerotic and atrophic lichen. Finally, an etiopathogenic hypothesis is raised to explain the fusion acquired by the small pudendal lips in the urocolpos. 相似文献
79.
80.
NV Tat'ianko LL Gromashevskaia AD Vovk MG Kasatkina OV Liashok VI Matiash SP Iasinovy? IaN Kovgan 《Canadian Metallurgical Quarterly》1996,(5-6):119-122
In this paper, characterization is given of clinical and biochemical features of VH B course against the background of narcomania. Recordable in such patient populations are high percentage of delta hepatitis (14.2%), unusual severity of the intoxication syndrome, protracted course with exacerbations (12.2%) and recurrences (8%), outcome being a chronic hepatitis (14.2%), slower normalization of biochemical indicators, persistently low ratio of AIAT activity in diluted and whole blood sera. The persistence of viral markers in drug addicts discharged from the hospital (68%) is fraught with danger of spreading viral hepatitis of prophylactic measures are not strictly observed. 相似文献