全文获取类型
收费全文 | 484984篇 |
免费 | 5337篇 |
国内免费 | 1185篇 |
专业分类
电工技术 | 8605篇 |
综合类 | 415篇 |
化学工业 | 77260篇 |
金属工艺 | 19459篇 |
机械仪表 | 14656篇 |
建筑科学 | 11533篇 |
矿业工程 | 2980篇 |
能源动力 | 10988篇 |
轻工业 | 45922篇 |
水利工程 | 5283篇 |
石油天然气 | 10808篇 |
武器工业 | 44篇 |
无线电 | 51462篇 |
一般工业技术 | 93104篇 |
冶金工业 | 89697篇 |
原子能技术 | 11864篇 |
自动化技术 | 37426篇 |
出版年
2021年 | 3876篇 |
2019年 | 3638篇 |
2018年 | 6536篇 |
2017年 | 6446篇 |
2016年 | 6926篇 |
2015年 | 4375篇 |
2014年 | 7460篇 |
2013年 | 20655篇 |
2012年 | 11866篇 |
2011年 | 16116篇 |
2010年 | 12964篇 |
2009年 | 14653篇 |
2008年 | 15216篇 |
2007年 | 15173篇 |
2006年 | 13438篇 |
2005年 | 12200篇 |
2004年 | 11476篇 |
2003年 | 11059篇 |
2002年 | 11195篇 |
2001年 | 10913篇 |
2000年 | 10597篇 |
1999年 | 10537篇 |
1998年 | 25157篇 |
1997年 | 18382篇 |
1996年 | 14250篇 |
1995年 | 10861篇 |
1994年 | 9846篇 |
1993年 | 9584篇 |
1992年 | 7481篇 |
1991年 | 7163篇 |
1990年 | 7188篇 |
1989年 | 7105篇 |
1988年 | 6924篇 |
1987年 | 5943篇 |
1986年 | 5999篇 |
1985年 | 6923篇 |
1984年 | 6608篇 |
1983年 | 6012篇 |
1982年 | 5638篇 |
1981年 | 5837篇 |
1980年 | 5645篇 |
1979年 | 5485篇 |
1978年 | 5556篇 |
1977年 | 6308篇 |
1976年 | 8130篇 |
1975年 | 5022篇 |
1974年 | 4784篇 |
1973年 | 4916篇 |
1972年 | 4191篇 |
1971年 | 3875篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
961.
The influence of the duration and spatial extent of a heat-releasing spark discharge on the critical conditions of spark ignition
of a reactive gas is considered. A region insensitive to the effect of these parameters and, thus, suitable for work with
the instantaneous source model is defined.
Tomsk. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 5, pp. 3–7, September–October, 1993. 相似文献
962.
The paper presents a review of results concerning the aspartic proteinase cathepsin D and its role in tumor invasion and metastasis. Special attention was paid to the clinical prognostic value of cathepsin D determination in the breast cancer cytosol. 相似文献
963.
L Struillou M Fiks-Sigaud JH Barrier E Blat G Magadur-Joly 《Canadian Metallurgical Quarterly》1993,60(7-8):524-526
The authors report an exceedingly rare complication of rheumatoid arthritis, i.e. acquired hemophilia due to anti-factor VIII autoantibody production. Treatment with intravenous immune globulin ensured control of hemorrhagic manifestations by inducing a transient rise in factor VIII level. 相似文献
964.
JM Rolland O Bical A Laradi J Robinault R Benzidia A Vanetti G Herreman 《Canadian Metallurgical Quarterly》1993,86(9):1383-1385
A false left ventricular aneurysm and coronary artery aneurysm were discovered in a 29 year old patient with Beh?et's syndrome. The operation under cardiopulmonary bypass consisted of closing the neck of the false aneurysm by an endo-aneurysmal approach with a Gore-Tex patch. The coronary artery aneurysms were respected. There were no postoperative complications. Cardiac involvement is rare in Beh?et's syndrome (6%). The originality of this case is the association of two aneurysmal pathologies: the coronary and ventricular aneurysms due to the angiitis and the myocardial fragility induced by ischaemia. 相似文献
965.
966.
J Karjalainen A Kanervo ML V?is?nen B Forsblom E Sarkiala H Jousimies-Somer 《Canadian Metallurgical Quarterly》1993,6(2-3):207-212
A total of 259 Gram-negative Porphyromonas-like rods isolated from subgingival plaque samples of 16 family-owned dogs with naturally occurring periodontitis were characterized phenotypically by biochemical reactions, metabolic end products and enzymatic activities (API-ZYMTM, RoscoTM). Four distinct groups were found. Group A isolates (63) were asaccharolytic, lipase negative, trypsin positive and produced phenylacetic acid (PAA) from peptone-yeast extract glucose broth. Unlike P. gingivalis strains they were catalase positive. Group B isolates (42) differed from those of group A by a positive lipase reaction and from those of group D by failing to ferment sugars. Group C isolates (88) were asaccharolytic and did not produce PAA. They were alpha-fucosidase, N-acetyl-beta-glucosaminidase (beta-NAG) and trypsin negative, resembling P. endodontalis, but unlike human isolates, they were catalase positive. Subgroup C.1 isolates (6) differed from those of parent group C by producing minor amounts of PAA, and subgroup C.2 isolates (12) were beta-NAG positive. Group D isolates (46) were weakly fermentative, lipase, catalase and trypsin positive, and produced PAA. They resembled the B (P.) salivosus type strain which, in our hands, fermented weakly glucose, lactose and mannose. Two isolates could not be assigned to any of the previous groups. 相似文献
967.
Beta-COP is essential for biosynthetic membrane transport from the endoplasmic reticulum to the Golgi complex in vivo 总被引:2,自引:0,他引:2
R Pepperkok J Scheel H Horstmann HP Hauri G Griffiths TE Kreis 《Canadian Metallurgical Quarterly》1993,74(1):71-82
Experimental glomerulonephritis was induced in rats to investigate the consequence of the antigen-antibody interaction on the surface of glomerular endothelial cells (GENs). A lectin, Lens culinaris hemoagglutinin (LCH), was first planted in the left kidney by isolated perfusion of a left kidney, and then the circulation was reestablished. Rabbit anti-LCH antibodies were injected from the tail vein 3 minutes after the recirculation of the left kidney, and acute glomerulonephritis ensued. Fifteen minutes after the injection, rabbit immunoglobulin G (IgG), rat C3, and LCH were observed exclusively on the surface of GENs. Accumulation of platelets was prominent. Three hours later, the immune deposits were seen in the subendothelial space, and the polymorphonuclear cells were the dominant infiltrate in the glomeruli. Up to the seventh day, immune deposits were seen in the subendothelial space, and the widening of this area was increasingly observed. Fourteen days later, immune deposits containing rat IgG were observed in the subepithelial area, but they were only occasionally seen in the subendothelial space and in the mesangial area. No crescent formation was seen at day 14, but the mesangial area was expanded, with an increased number of cells. The number of nuclei in the cross-section of a glomerulus increased after the induction of glomerulonephritis, but the number of leukocyte common antigen-positive cells (infiltrating cells) decreased gradually from day 4 to day 14. The staining of Thy-1.1, a marker of mesangial cell, was markedly enlarged in the glomerulus at day 14. These data suggest that mesangial proliferative glomerulonephritis can be induced by the antigen-antibody interaction on the surface of GENs. 相似文献
968.
969.
G Giordano 《Canadian Metallurgical Quarterly》1996,67(3):327-334
Thyroid nodules are among the most common clinical problems in endocrinology. Among several factors responsible for the development of goiter, circulating TSH plays a major role because of its direct growth-promoting effects on the thyroid cells; moreover TSH may enhance the effects of other local growth factors which act in a paracrine mode in the thyroid gland. In addition, autoimmune thyroiditis can clinically appear as thyroid nodules frequently with the functional aspect of a subclinical hypothyroidism. For these reasons a therapeutical approach based on the thyroxine suppression of TSH secretion has become largely used by 1970s and is correctly employed in 75% of the patients with thyroid nodules whose biopsies result benign. 相似文献
970.
W Dobrowsky J Naudé J Widder E Dobrowsky W Millesi R Pavelka C Grasl M Reichel 《Canadian Metallurgical Quarterly》1998,42(4):803-806
PURPOSE: To evaluate the effect of mitomycin C to an accelerated hyperfractionated radiation therapy. The aim was to test a very short schedule with/without mitomycin C (MMC) with conventional fractionation in histologically verified squamous cell carcinoma of the head and neck region. METHODS AND MATERIALS: From October 1990 to December 1996, 188 patients entered the trial. Tumors originated in the oral cavity in 54, oropharynx in 82, larynx in 20, and hypopharynx in 32 cases, respectively. Patients' stages were predominantly T3 and T4 (158/188, 84%) and most patients had lymph node metastases (144/188, 77%) at diagnosis. Only 22 patients were female, 166 were male, the median age of patients was 57 years (range 34 to 76 years). Patients were randomized to one of the following three treatment options: conventional fractionation (CF) consisting of 70 Gy in 35 fractions over 7 weeks (65 patients) or continuous hyperfractionated accelerated radiation therapy (V-CHART; 62 patients) or continuous hyperfractionated accelerated radiation therapy with 20 mg/sqm MMC on day 5 (V-CHART + MMC; 61 patients). By the accelerated regimens, the total dose of 55.3 Gy was delivered within 17 consecutive days, by 33 fractions. On day 1, a single dose of 2.5 Gy was given, from day 2 to 17 a dose of 1.65 Gy was delivered twice: the interfraction interval was 6 hours or more. RESULTS: Mucositis was very intense after accelerated therapy, most patients experiencing a grade III/IV reaction. The mucosal reaction did not differ whether MMC was administered or not. Patients treated by accelerated fractionation experienced a confluent mucosal reaction 12-14 days following start of therapy and recovered (no reaction) within 6 weeks. The skin reaction was not considered different in the three treatment groups. Those patients treated with additional chemotherapy experienced a grade III/IV hematologic toxicity in 12/61 patients. Initial complete response (CR) was recorded in 43% following CF, 58% after V-CHART, and 67% after V-CHART + MMC, respectively (p < 0.05). Actuarial survival (Kaplan-Meier) was significantly improved in the combined treated patients. Local tumor control was 28%, 32%, and 56% following CF, V-CHART, and V-CHART + MMC, respectively (p < 0.05). CONCLUSION: We conclude that our continuous hyperfractionated accelerated radiation therapy regimen is equal to conventional fractionation, suggesting that by shortening the overall treatment time from 7 weeks to 17 days a reduction in dose from 70 Gy to 55.3 Gy is possible, with maintenance of local tumor control rates. The administration of MMC to the accelerated regimen is tolerable and improves the outcome for patients significantly. 相似文献