全文获取类型
收费全文 | 1235篇 |
免费 | 1篇 |
国内免费 | 3篇 |
专业分类
化学工业 | 9篇 |
金属工艺 | 2篇 |
建筑科学 | 5篇 |
轻工业 | 3篇 |
一般工业技术 | 9篇 |
冶金工业 | 1206篇 |
原子能技术 | 1篇 |
自动化技术 | 4篇 |
出版年
2021年 | 2篇 |
2020年 | 1篇 |
2017年 | 1篇 |
2013年 | 2篇 |
2012年 | 1篇 |
2011年 | 2篇 |
2010年 | 1篇 |
2008年 | 1篇 |
2005年 | 3篇 |
2003年 | 5篇 |
2002年 | 2篇 |
2000年 | 1篇 |
1999年 | 41篇 |
1998年 | 386篇 |
1997年 | 213篇 |
1996年 | 146篇 |
1995年 | 75篇 |
1994年 | 72篇 |
1993年 | 71篇 |
1992年 | 4篇 |
1991年 | 15篇 |
1990年 | 12篇 |
1989年 | 16篇 |
1988年 | 10篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 7篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1978年 | 4篇 |
1977年 | 28篇 |
1976年 | 69篇 |
1975年 | 10篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有1239条查询结果,搜索用时 15 毫秒
81.
CA Awoniyi D Roberts DN Veeramachaneni BS Hurst KE Tucker WD Schlaff 《Canadian Metallurgical Quarterly》1998,70(3):440-447
OBJECTIVE: To determine reproductive sequelae in female rats after in utero and lactational dietary exposure to genistein. DESIGN: Experimental animal study. SETTING: University laboratory. ANIMAL(S): Sprague Dawley rats. INTERVENTION(S): Pregnant rats were fed control rat chow or rat chow incorporated with genistein (approximately 50 microg/d) beginning on day 17 of gestation and continuing until the end of lactation (postpartum day 21). Genistein-exposed female pups were divided into two groups on day 21. One group continued to receive a genistein-added diet (G70); the other group was changed to a control diet (Ex-G). At necropsy (days 21 and 70), blood and reproductive tissues were collected. MAIN OUTCOME MEASURE(S): Serum levels of gonadotropins and gonadal steroids and histopathologic examination of the ovaries. RESULT(S): The weight of the ovaries and uterus and serum levels of E2 and progesterone in genistein-exposed rats on day 21 (G21) were significantly reduced compared with control rats. On day 70, serum levels of E2, progesterone, LH, and FSH were similar in all groups. Atretic follicles and secondary interstitial glands were more common in G70 and Ex-G rats compared with control rats. Cystic rete ovarii was observed in some G70 and Ex-G rats. CONCLUSION(S): Our data indicate that in utero and lactational exposure to dietary genistein adversely affects reproductive processes in the adult female rat. 相似文献
82.
E Lindbladh CH Lyttkens BS Hanson PO Ostergren 《Canadian Metallurgical Quarterly》1998,46(8):1017-1025
The 67-kDa laminin receptor (67LR) is a nonintegrin cell surface receptor that mediates high-affinity interactions between cells and laminin. Overexpression of this protein in tumor cells has been related to tumor invasion and metastasis. Thus far, only a full-length gene encoding a 37-kDa precursor protein (37LRP) has been isolated. The finding that the cDNA for the 37LRP is virtually identical to a cDNA encoding the ribosomal protein p40 has suggested that 37LRP is actually a component of the translational machinery, with no laminin-binding activity. On the other hand, a peptide of 20 amino acids deduced from the sequence of 37LR/p40 was shown to exhibit high laminin-binding activity. The evolutionary relationship between 23 sequences of 37LRP/p40 proteins was analyzed. This phylogenetic analysis indicated that all of the protein sequences derive from orthologous genes and that the 37LRP is indeed a ribosomal protein that acquired the novel function of laminin receptor during evolution. The evolutionary analysis of the sequence identified as the laminin-binding site in the human protein suggested that the acquisition of the laminin-binding capability is linked to the palindromic sequence LMWWML, which appeared during evolution concomitantly with laminin. 相似文献
83.
RE Pecha T Prindiville BS Pecha R Camp M Carroll W Trudeau 《Canadian Metallurgical Quarterly》1996,91(12):2523-2527
OBJECTIVES: Giant gastric and duodenal ulcers (>2-3 cm in greatest dimension) are reported to have higher rates of complication and mortality and to be associated with increasing age, renal failure, and use of nonsteroidal antiinflammatory drugs (NSAIDs). This study investigated the outcome and associations of gastric and duodenal ulcers >2.5 cm compared to ulcers of lesser size. METHODS: Records from all patients with gastric and duodenal ulcers >0.5 cm diagnosed by upper endoscopy between January 1994 and September 1995 were studied for evidence of concurrent use of aspirin, NSAIDs, methamphetamine, and cocaine, as well as for transfusion requirements, length of hospital stay, mortality, surgery, rebleeding, Helicobacter pylori infection, and malignancy. RESULTS: A logistic regression analysis of the 220 patients identified revealed that recent methamphetamine and/or cocaine use was significantly predictive of giant ulcer formation (p = 0.0002) with an odds ratio of 9.66. Also significant was younger age (p = 0.026) and aspirin or NSAID use (p = 0.046). H. pylori infection was significant only for giant gastric ulcers (p = 0.031). Ulcer size did not predict mortality, rate of rebleeding, requirement for surgery, transfusion requirements, or length of hospital stay. However, giant gastric ulcers were significantly more likely to be malignant (p = 0.002). CONCLUSIONS: Giant gastric and duodenal ulcers were strongly associated with stimulant abuse. They were also associated with younger age and use of aspirin or NSAIDs. Additionally, giant gastric ulcers were associated with malignancy and H. pylori infection. Ulcer size did not predict rate of complications or outcome. 相似文献
84.
PURPOSE: To assess the efficacy of excimer laser photorefractive astigmatic keratectomy (PARK) in correcting astigmatism of more than -2.00 diopters (D) in eyes with low, high, and extreme myopia. SETTING: Pusan National University Hospital, Pusan, Korea. METHODS: Eighty-five patients (110 eyes) whose spherical error ranged from -3.00 to -13.00 D and cylinder ranged from -2.00 to -5.50 D had PARK with a VISX Twenty-Twenty excimer laser; follow-up was 6 months. All cases of myopic astigmatism were treated using the elliptical method and multizone ablation technique. Eyes were divided into 3 groups: low myopia, less than 6.00 D (n = 47); high myopia, from 6.25 to 10.00 D (n = 43); extreme myopia, over 10.25 D (n = 20). Alpins vector analysis was used to calculate the astigmatic change. RESULTS: By vector analysis, the success rate of astigmatic correction was more predictable in the low and high myopia groups than in the extreme myopia group (P < .05). There was little improvement in astigmatism in the extreme myopia group. CONCLUSION: Using PARK to correct astigmatism greater than -2.00 D in eyes with myopia less than -10.00 D tended to result in undercorrection; astigmatic correction in eyes with myopia over 10.25 D was minimal. 相似文献
85.
This study was undertaken to determine if acidic or basic fibroblast growth factor (FGF1 or FGF2) or vascular endothelial growth factor (VEGF) alters the radiation response of small bowel after total-body irradiation (TBI). Female C3H mice were treated with various doses of angiogenic growth factor administered intravenously 24 h before or 1 h after TBI. Radiation doses ranged from 7 to 18 Gy. End points measured were the number of crypts in three portions of the small bowel, the frequency of apoptosis of crypt cells at various times after TBI, and the LD50/30 (bone marrow syndrome) and LD50/6 (GI syndrome). Fibroblast growth factors alone, without TBI, decreased the number of crypts per circumference significantly. Among the factors tested, FGF2 caused the greatest decline in baseline crypt number. Despite this decrease in the baseline crypt number, after irradiation the number of surviving crypts was greater in animals treated with growth factor. The greatest radioprotection occurred at intermediate doses of growth factor (6 to 18 pg/mouse). Mice treated with FGF1 and FGF2 had crypt survival curves with a slope that was more shallow than that for saline-treated animals, indicating radiation resistance of crypt stem cells in FGF-treated mice. The LD50/6 was increased by approximately 10% for all treatments with angiogenic growth factors, whether given before or after TBI. Apoptosis of crypt cells was maximum at 4 to 8 h after TBI. The cumulative apoptosis was decreased significantly in animals treated with angiogenic growth factors, and the greatest protection against apoptosis was seen in animals treated with FGF2 prior to TBI. All three angiogenic growth factors tested were radioprotective in small bowel whether given 24 h before or 1 h after irradiation. The mechanism of protection is unlikely to involve proliferation of crypt stem cells, but probably does involve prevention of radiation-induced apoptosis or enhanced repair of DNA damage of crypt cells. 相似文献
86.
EH Uhlenhuth PE Alexander GM Dempsey W Jones BS Coleman AM Swiontek 《Canadian Metallurgical Quarterly》1998,47(1-3):183-190
Heart sounds produce an incessant noise during lung sounds recordings. This noise severely contaminates the breath sounds signal and interferes in the analysis of lung sounds. In this paper, the use of a wavelet transform domain filtering technique as an adaptive de-noising tool, implemented in lung sounds analysis, is presented. The multiresolution representations of the signal, produced by wavelet transform, are used for signal structure extraction. In addition, the use of hard thresholding in the wavelet transform domain results in a separation of the nonstationary part of the input signal (heart sounds) from the stationary one (lung sounds). Thus, the location of the heart sound noise (1st and 2nd heart sound peaks) is automatically detected, without requiring any noise reference signal. Experimental results have shown that the implementation of this wavelet-based filter in lung sound analysis results in an efficient reduction of the superimposed heart sound noise, producing an almost noise-free output signal. Due to its simplicity and its fast implementation the method can easily be used in clinical medicine. 相似文献
87.
M Montagna O Serova BS Sylla MG Mattei GM Lenoir 《Canadian Metallurgical Quarterly》1996,98(6):738-740
The h-PRL-1 gene codes for a new phosphotyrosine phosphatase that may play an important role in the control of basic cellular processes such as cell growth and proliferation. Using the cDNA of the h-PRL-1 gene as a probe, we examined a somatic mouse and hamster x human hybrid panel and found that chromosomes 1, 17 and 11 harbor sequences homologous to h-PRL-1. By in situ hybridization of metaphase spreads, subchromosomal localizations were determined at bands 1p35-p34, 17q12-q21 and 11q24-q25; in addition, a faint signal was detected at 12q24. The chromosomal assignment of the genes homologous to h-PRL-1 will help the investigation of its possible involvement in human diseases involving genetic alteration at these chromosomal regions. 相似文献
88.
Using light and electron microscopic immunocytochemistry, we examined the expression of the Ca2+-binding protein S100B in the dentate gyrus of adult rats during lesion-induced sprouting and reactive synaptogenesis. Nine days following unilateral lesioning of the entorhinal cortex, S100B was upregulated in cells primarily in the outer part of the molecular layer of the ipsilateral dentate gyrus. When examined with electron microscopy, numerous astrocytes and synapses containing S100B were identified. These data show that during lesion-induced sprouting and reactive synaptogenesis, S100B is upregulated in astrocytes and can be found in pre- and post-synaptic compartments where it might influence neuronal protein phosphorylation. 相似文献
89.
90.
T Croci M Landi D Gully JP Maffrand G Le Fur L Manara 《Canadian Metallurgical Quarterly》1997,120(7):1312-1318
1. We investigated the effect of the non-peptide neurotensin (NT) antagonist SR 48692 on renal function in rats and the involvement of nitric oxide (NO) in the diuretic action of this compound. 2. In fed animals, SR 48692 dose-dependently (0.5 to 12.5 mg kg-1, p.o., 0.03 to 1 mg kg-1, i.p. and 0.1 to 1 microgram/rat, i.c.v.) increased urine output and urinary excretion of Na+, K+ and Cl- and reduced urine osmolality. The diuretic activity was also evident in water-deprived, fasted animals and in fasted, water-loaded rats. 3. NT (0.1 microgram/rat, i.c.v.) had no effect on urine output in fed rats, but reduced the diuretic action of SR 48692 (1 microgram/rat, i.c.v.). The opposite result was obtained in fasted, water-loaded animals: NT dose-dependently (0.01 and 0.1 microgram/rat, i.c.v.) inhibited diuresis and this effect was significantly inhibited by i.c.v. SR 48692. In this experimental condition, SR 48692 did not further increase the on-going diuresis. 4. The NO synthesis inhibitor N(1)-nitro-L-arginine methyl ester (L-NAME; 30 mg kg-1, i.p.) alone had no effect on urine output in fed rats but prevented the diuretic action of i.c.v. or i.p. SR 48692; L-arginine (1 g kg-1, i.p.) but not D-arginine (1 g kg-1, i.p.) restored the SR 48692-dependent increase in diuresis, L-NAME had no effect on furosemide-stimulated diuresis. 5. Systemically administered L-NAME or i.c.v. NT in fasted, water-loaded rats significantly reduced water diuresis but this effect was no longer seen in animals given i.p. L-arginine. Rats receiving i.c.v. NT, whose diuresis was significantly reduced, also excreted less nitrates and nitrites in urine. 6. Increased diuresis after central or systemic administration of SR 48692 to fed rats was paralleled by increased urinary excretion of nitrates and nitrites, this being consistent with peripheral enhancement of NO production after NT-receptor blockade by SR 48692. The increase in diuresis after furosemide also involved an increase of nitrates and nitrites in urine, but this effect was about half that attained with an equipotent diuretic dose of SR 48692. 7. In fed rats, the NO donor isosorbide-dinitrate, reduced systolic blood pressure (unlike SR 48692 which did not affect blood pressure) but also dose-dependently (1 and 5 mg kg-1, i.p.) stimulated urine output. 8. The overall effects of SR 48692 strongly support a link between the actions of endogenous NT, AVP and peripheral NO production in the modulation of renal excretion of water, Na+, K+ and Cl-. 相似文献