全文获取类型
收费全文 | 73175篇 |
免费 | 2275篇 |
国内免费 | 381篇 |
专业分类
电工技术 | 1104篇 |
综合类 | 893篇 |
化学工业 | 9815篇 |
金属工艺 | 1329篇 |
机械仪表 | 1574篇 |
建筑科学 | 1963篇 |
矿业工程 | 501篇 |
能源动力 | 1388篇 |
轻工业 | 6180篇 |
水利工程 | 899篇 |
石油天然气 | 254篇 |
武器工业 | 63篇 |
无线电 | 4205篇 |
一般工业技术 | 7510篇 |
冶金工业 | 28391篇 |
原子能技术 | 460篇 |
自动化技术 | 9302篇 |
出版年
2024年 | 113篇 |
2023年 | 364篇 |
2022年 | 653篇 |
2021年 | 966篇 |
2020年 | 610篇 |
2019年 | 703篇 |
2018年 | 1131篇 |
2017年 | 1421篇 |
2016年 | 1813篇 |
2015年 | 1368篇 |
2014年 | 1378篇 |
2013年 | 1953篇 |
2012年 | 3462篇 |
2011年 | 4140篇 |
2010年 | 1976篇 |
2009年 | 2078篇 |
2008年 | 1844篇 |
2007年 | 1740篇 |
2006年 | 1479篇 |
2005年 | 4160篇 |
2004年 | 3420篇 |
2003年 | 2819篇 |
2002年 | 1672篇 |
2001年 | 1470篇 |
2000年 | 842篇 |
1999年 | 1170篇 |
1998年 | 8357篇 |
1997年 | 5233篇 |
1996年 | 3504篇 |
1995年 | 2084篇 |
1994年 | 1581篇 |
1993年 | 1699篇 |
1992年 | 478篇 |
1991年 | 599篇 |
1990年 | 534篇 |
1989年 | 469篇 |
1988年 | 505篇 |
1987年 | 398篇 |
1986年 | 367篇 |
1985年 | 362篇 |
1984年 | 200篇 |
1983年 | 169篇 |
1982年 | 248篇 |
1981年 | 302篇 |
1980年 | 321篇 |
1979年 | 152篇 |
1978年 | 173篇 |
1977年 | 767篇 |
1976年 | 1626篇 |
1975年 | 184篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Recurrent erosion of the corneal epithelium has been treated successfully by phototherapeutic keratectomy when convention therapy has failed. We present a case of recurrent corneal erosion occurring 1 year after photorefractive keratectomy in a 55-year-old myopic woman. No corneal abnormalities were previously identified in either the affected or the fellow eye. This case demonstrates the potential for ineffective healing of the corneal epithelial basement membrane complex after excimer laser photorefractive keratectomy. 相似文献
32.
GN Mozhokina GB Sokolova OV Makarova LP Mikha?lova 《Canadian Metallurgical Quarterly》1996,41(7-8):31-33
The effect of lomefloxacin was studied on mice with experimental infection due to Mycobacterium tuberculosis. The antibiotic was administered in doses of 100 and 200 mg/kg. It was shown that the use of lomefloxacin for a month provided a lower death rate of the animals with progressing acute generalized tuberculosis, a lower level of the lesions in the internal organs and a lower number of the Mycobacterium isolates from them. The efficacy of the treatment depended on the drug dose. When lomefloxacin was used in a dose of 200 mg/kg, the survival rate was much higher and the number of the epithelial unicellular granulomas in the tissue of the lung and spleen was markedly decreased while with the lower dose the indices did not differ from those in the control. 相似文献
33.
34.
In the last 2 years (1994-95), two symposium volumes and three reviews have been published that were fully devoted to peptide antibiotics (antibacterial peptides or antimicrobial peptides). Since the field has been growing rapidly, this review is largely a follow-up of new results published in the last 2 years. Sequencing of the 16S RNA of the small ribosomal subunit indicate that the microbial world is much larger than generally appreciated. The importance of the natural flora is stressed and its effect on the evolution of peptide antibiotics and immunity in general is discussed. 相似文献
35.
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
36.
Daniela M. Nevskaia Maria Luisa Rojas Cervantes Antonio Guerrero Ruíz Juan de Dios Lpez Gonzlez 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1995,63(3):249-256
Adsorption of Triton X-100 on various silica substrates has been investigated. A number of solids, including a natural quartz, this quartz washed with HCl acid and subsequently heated at 1273 K; two aerosils and one Kieselgel silicas were studied. These solids exhibit surface areas in the range of 5 to 430 m2 g?1. All the Triton adsorption isotherms display an S-shape at the adsorption temperatures studied (298 and 308 K). It has been found that the pretreatments of natural quartz (by water washing, impurities removed by acid and/or high temperature calcination) affect considerably the amounts of TX-100 adsorbed. Measurements of surface composition have been made by X-ray photoelectron spectroscopy (XPS) with particular emphasis on the presence of impurities and on the number of OH groups at the surface of the samples. The nature of the surface hydroxyl has also been studied by infrared spectroscopy. Furthermore, the specific number of hydroxyl groups on the surface of the silica samples has been determined by thermogravimetric analysis. Finally an attempt to correlate solid surface characteristics with adsorption isotherms has been developed. 相似文献
37.
Purified cell-envelope polyphosphatase as well as polyphoshatase activities of cytosol and isolated vacuoles, of nuclei and mitochondria of the yeast Saccharomyces cerevisiae were compared. The polyphosphatases of cell envelope and cytosol are similar, the polyphosphatases of nuclei, vacuoles and mitochondria differ in their kinetic properties, substrate specificity, requirements in divalent cations and in some effector actions both from these and from each other. 相似文献
38.
1. A total of 360 Japanese quail of 4 commercial meat-type lines and two diet treatments (260 and 216 g/kg or 238 and 195 g/kg of crude protein (CP) in the starter and grower diet, respectively) were used. 2. The positive effect of a high CP diet on body weight was significant only for the first 4 weeks after hatching. 3. The mean age at inflection point of the growth curve (t+) across lines and sexes was 1.4 d (0.6 to 2.8 d within line/sex groups) earlier for quail fed on a high CP diet than in quail receiving a low CP diet. The inflection (y+) and asymptotic (A) weights were similar under both dietary protein concentrations. Nevertheless, the shape of the growth curve, characterised by the ratio y+/A and parameter of the maturing rate k, was significantly influenced by diet. 4. A higher food intake and less efficient food conversion were found for quail fed on a high CP diet in the period from 15 to 28 d of age. 5. The fattening traits such as body weight, cumulative food intake and food conversion, were not affected by dietary CP content at the age of 5 weeks. 6. The effects of line on body weight, food intake and food conversion are discussed. 相似文献
39.
K Giesen T Hummel A Stollewerk S Harrison A Travers C Kl?mbt 《Canadian Metallurgical Quarterly》1997,124(12):2307-2316
Two classes of glial cells are found in the embryonic Drosophila CNS, midline glial cells and lateral glial cells. Midline glial development is triggered by EGF-receptor signalling, whereas lateral glial development is controlled by the gcm gene. Subsequent glial cell differentiation depends partly on the pointed gene. Here we describe a novel component required for all CNS glia development. The tramtrack gene encodes two zinc-finger proteins, one of which, ttkp69, is expressed in all non-neuronal CNS cells. We show that ttkp69 is downstream of gcm and can repress neuronal differentiation. Double mutant analysis and coexpression experiments indicate that glial cell differentiation may depend on a dual process, requiring the activation of glial differentiation by pointed and the concomitant repression of neuronal development by tramtrack. 相似文献
40.