全文获取类型
收费全文 | 1491篇 |
免费 | 0篇 |
专业分类
化学工业 | 4篇 |
轻工业 | 3篇 |
一般工业技术 | 3篇 |
冶金工业 | 1481篇 |
出版年
2015年 | 1篇 |
2013年 | 2篇 |
2012年 | 1篇 |
2010年 | 1篇 |
2006年 | 1篇 |
2003年 | 4篇 |
2000年 | 1篇 |
1999年 | 35篇 |
1998年 | 468篇 |
1997年 | 277篇 |
1996年 | 179篇 |
1995年 | 91篇 |
1994年 | 72篇 |
1993年 | 84篇 |
1992年 | 7篇 |
1991年 | 23篇 |
1990年 | 18篇 |
1989年 | 17篇 |
1988年 | 16篇 |
1987年 | 26篇 |
1986年 | 16篇 |
1985年 | 13篇 |
1982年 | 7篇 |
1981年 | 14篇 |
1980年 | 11篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 24篇 |
1976年 | 75篇 |
1975年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有1491条查询结果,搜索用时 15 毫秒
41.
Bowen's disease has a particular predilection for the lower leg, especially in women. A review of the literature for treating Bowen's disease is presented and the problems associated with treating the lower leg emphasized. Evidence for the various treatment modalities used to treat Bowen's disease largely comes from studies that lack good methodology in terms of standardized techniques, patient controls and adequate follow-up. In particular the widely accepted recommendation for excision is not supported by evidence that this treatment is superior to other modalities. The choice of treatment for Bowen's disease should take into account the patient's general condition, the site and size of the lesion. 相似文献
42.
JW Brufsky D Ross-Degnan D Calabrese X Gao SB Soumerai 《Canadian Metallurgical Quarterly》1998,36(3):321-332
Three receptor tyrosine kinases of the PDGF receptor family (RTKP) that clustered within 1000 Kb of the mouse chromosome 5 constitute an interesting unit that are expressed in three distinct cell lineages essential for constructing hematopoietic tissues. Namely, the c-kit gene that is expressed in hematopoietic stem cells is flanked by pdgfr alpha and flk genes expressed respectively in stromal cells and vascular endothelial cells. In this article, we review our results on their expression in the embryonic hematopoietic tissues. We found that co-expression of Flkl and c-Kit was frequently detected either in vascular endothelial cells or hematopoietic cells in the early hematopoietic tissues. On the other hand, the three RTKPs are expressed in different cell lineages in the fetal liver. On the basis of this finding, we propose two modes of embryonic hematopoiesis; hematogenic angiopoiesis and hematopoiesis. 相似文献
43.
SB Gelvin 《Canadian Metallurgical Quarterly》1998,16(11):1009-1010
44.
Glutamate-mediated excitotoxicity plays an important role in the degeneration of nigrostriatal dopamine (DA) neurons induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), although the role of the N-methyl D-aspartate (NMDA) receptor subtype in this process is still uncertain. We studied glutamate receptor subtype agonist-induced ionic currents in acutely dissociated DAergic neurons from the rat substantia nigra zona compacta (SNc) using the nystatin-perforated patch-clamp whole-cell recording technique. The results fall into four main categories. First, single neurons, freshly isolated from SNc, exhibited a large soma and multipolar morphology, responded to DA, and stained positively for tyrosine hydroxylase (TH). Second, rapid application of L-glutamate (> 10(-5) M) induced an inward current with minimal desensitization at a clamp voltage of -60 mV. Third, kainic acid (KA) or alpha-amino-3-hydroxy-5-methyl-isoxazole (AMPA) induced an inward current that was similar to the glutamate-induced current while, in the same neuron, NMDA (10(-4) M) failed to induce any current response in Mg2+-free solution that contained 10(-5) M glycine at a clamp voltage of -60 mV. Under the same experimental conditions, NMDA induced a clear current response in isolated substantia nigra reticulata (SNr) neurons. Fourth, the specific NMDA receptor antagonist DL-2-amino-5-phosphonovaleric acid (APV, 10(-4) M) failed to block 10(-4) M glutamate-induced inward current, while the specific KA/AMPA receptor antagonist 6-cyano-7-nitroguinoxaline-2, 3-dione (CNQX, 10(-5) M) completely blocked the glutamate-induced current. These results indicate that in single SNc DAergic neurons of 2-week-old rats, L-glutamate-induced inward current is mediated by non-NMDA receptors rather than by NMDA receptors. 相似文献
45.
SB Christensen A Guider CJ Forster JG Gleason PE Bender JM Karpinski WE DeWolf MS Barnette DC Underwood DE Griswold LB Cieslinski M Burman S Bochnowicz RR Osborn CD Manning M Grous LM Hillegas JO Bartus MD Ryan DS Eggleston RC Haltiwanger TJ Torphy 《Canadian Metallurgical Quarterly》1998,41(6):821-835
Evaluation of a variety of PDE4 inhibitors in a series of cellular and in vivo assays suggested a strategy to improve the therapeutic index of PDE4 inhibitors by increasing their selectivity for the ability to inhibit PDE4 catalytic activity versus the ability to compete for high affinity [3H]rolipram-binding sites in the central nervous system. Use of this strategy led ultimately to the identification of cis-4-cyano-4-[3-(cyclopentyloxy)-4-methoxyphenyl]cyclohexane-1-carboxyl ic acid (1, SB 207499, Ariflo), a potent second-generation inhibitor of PDE4 with a decreased potential for side effects versus the archetypic first generation inhibitor, (R)-rolipram. 相似文献
46.
MS Kellermayer SB Smith C Bustamante HL Granzier 《Canadian Metallurgical Quarterly》1998,122(1-2):197-205
Titin (also known as connectin) is a giant filamentous protein that spans the distance between the Z- and M-lines of the vertebrate muscle sarcomere. Several earlier studies have implicated titin as playing a fundamental role in maintaining sarcomeric structural integrity and generating the passive force of muscle. The elastic properties of titin were characterized in recent single-molecule mechanical works that described the molecule as an entropic spring in which partial unfolding may take place at high forces during stretch and refolding at low forces during release. In the present work titin molecules were stretched using a laser tweezer with forces above 400 pN. The high external forces resulted in complete mechanical unfolding of the molecule, characterized by the disappearance of force hysteresis at high forces. Titin refolded following complete denaturation, as the hysteresis at low forces reappeared in subsequent stretch-release cycles. The broad force range throughout which unfolding occurred indicates that the various globular domains in titin require different unfolding forces due to differences in the activation energies for their unfolding. 相似文献
47.
48.
SB Guze 《Canadian Metallurgical Quarterly》1997,52(5):398-403
The relationship between trunk muscle morphology as measured on transverse magnetic resonance images and isokinetic lifting, psychophysical lifting, and static back muscle endurance testing was examined in 110 men, ages 35-67 years (mean, 48 years), who had been chosen based on their exposure to a wide variety of occupational and leisure-time physical activities. The computed T2-relaxation times and the T2-weighted and proton density-weighted signal intensities of the erector spinae, quadratus lumborum, and psoas major muscles had almost no association with any of the strength tests. The cross-sectional areas of the muscles had good correlations with isokinetic lifting strength (r = 0.46-0.53). They did not correlate well with psychophysical lifting and static back muscle endurance. Other characteristics or neurological or psychological factors may have more influence on those tests. 相似文献
49.
V Deroche SB Caine CJ Heyser I Polis GF Koob LH Gold 《Canadian Metallurgical Quarterly》1997,57(3):429-440
Application of animal models of psychostimulant abuse for experimentation in mice is becoming increasingly important for studying the contribution of genetic differences, as well as the roles of selected (targeted) genes, in specific behaviors. The purpose of this study was to investigate strain differences in cocaine self-administration behavior between C57BL/6 x SJL hybrid mice and BALB/cByJ mice. These two strains were chosen because BALB/cByJ mice have a well-developed behavioral pharmacological profile, and hybrid strains on a C57BL/6 background are commonly used for generating transgenic expressing and knockout mutant mice. C57BL/6 x SJL mice dose-dependently acquired cocaine self-administration (1.0 mg/kg/injection but not 0.25 mg/kg/injection) by responding selectively in the active nose-poke hole and maintaining stable levels of daily drug intake; they also exhibited a characteristic inverted-U-shaped cocaine dose-effect function. BALB/cByJ mice failed to acquire cocaine self-administration at either dose under the same test conditions. The strain differences observed in self-administration did not seem to be attributed to other behavioral differences because the two strains exhibited similar amounts of spontaneous nose-poking in the absence of reinforcers, and BALB/cByJ mice responded more than C57BL/6 x SJL mice in a food-reinforced nose-poke operant task. Importantly, the dose-effect function for the motor stimulating effects of cocaine (3.8-30 mg/kg intraperitoneally) suggests enhanced sensitivity but reduced efficacy of cocaine in stimulating motor activity in BALB/cByJ mice relative to the C57BL/6 x SJL hybrid mice. These results indicate that the decreased liability of BALB/cByJ mice to acquire cocaine self-administration is not the result of differences in spontaneous activity or performance, but may reflect different sensitivities to the reinforcing, or rate-disrupting, properties of cocaine. The data support an influence of genetic background in the liability to self-administer cocaine. Thus, a hypothesis is proposed that the decreased liability of BALB/cByJ mice to acquire cocaine self-administration is related to differences in brain monoamine systems linked to the high "emotionality" profile of BALB/c mice in novel or fearful situations, including perhaps cocaine administration. 相似文献
50.
UA Temann B Prasad MW Gallup C Basbaum SB Ho RA Flavell JA Rankin 《Canadian Metallurgical Quarterly》1997,16(4):471-478
Mucus hypersecretion and plugging of lower respiratory tract airways contributes to the morbidity and mortality associated with asthma. Interleukin (IL)-4 plays a putative role in some forms of asthma. Thus, transgenic mice that overexpress murine IL-4 selectively within the lung were used to study the effect of IL-4 on mucus glycoprotein gene expression and mucin release. Histologic examination of lung sections from IL-4 mice revealed that nonciliated epithelial cells from conducting airways were hypertrophic, due at least in part to the accumulation of mucus glycoprotein. The cytoplasm of these cells stained positively for glycoproteins using mucicarmine, alcian blue (AB), and periodic acid-Schiff (PAS). Ciliated cells were also enlarged but did not show any mucin-specific staining. Inclusion granules typically found in nonciliated (Clara) cells of control mice were absent in the IL-4 transgenic mice. Northern blot analysis of total RNA from lung tissue revealed that the expression of the MUC5AC, but not MUC2, mucin gene was distinctly upgraded in IL-4 transgenic mice compared to transgene-negative controls. In addition, a 5- to 10-fold increase in AB- and PAS-positive material was found in lavage fluid from IL-4 overexpressing mice compared to transgene-negative controls. Thus, the overexpression of IL-4 locally within the lung enhances mucus glycoprotein synthesis by altering gene expression, results in the accumulation of mucus glycoprotein in nonciliated epithelial cells, and induces the release of mucus into the airway lumen. We therefore hypothesize that the overproduction of mucus seen in some patients with asthma may be a direct result of the action of IL-4 within the inflamed lung. 相似文献