全文获取类型
收费全文 | 1673篇 |
免费 | 5篇 |
专业分类
化学工业 | 12篇 |
金属工艺 | 2篇 |
机械仪表 | 1篇 |
建筑科学 | 1篇 |
轻工业 | 20篇 |
无线电 | 4篇 |
一般工业技术 | 16篇 |
冶金工业 | 1613篇 |
原子能技术 | 2篇 |
自动化技术 | 7篇 |
出版年
2017年 | 3篇 |
2016年 | 2篇 |
2014年 | 2篇 |
2013年 | 1篇 |
2012年 | 1篇 |
2011年 | 7篇 |
2010年 | 2篇 |
2009年 | 5篇 |
2008年 | 1篇 |
2007年 | 1篇 |
2006年 | 4篇 |
2005年 | 1篇 |
2004年 | 1篇 |
2003年 | 1篇 |
2002年 | 1篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 34篇 |
1998年 | 443篇 |
1997年 | 257篇 |
1996年 | 183篇 |
1995年 | 117篇 |
1994年 | 95篇 |
1993年 | 96篇 |
1992年 | 13篇 |
1991年 | 18篇 |
1990年 | 19篇 |
1989年 | 28篇 |
1988年 | 25篇 |
1987年 | 29篇 |
1986年 | 20篇 |
1985年 | 21篇 |
1984年 | 1篇 |
1983年 | 7篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 21篇 |
1978年 | 7篇 |
1977年 | 58篇 |
1976年 | 126篇 |
1975年 | 5篇 |
1964年 | 2篇 |
1962年 | 1篇 |
1956年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有1678条查询结果,搜索用时 15 毫秒
991.
Three new titanium alloys with Zr, Nb, Ta, Pd and In as alloying elements were developed and compared with currently used implant metals, namely, pure Ti and Ti-6Al-4V alloy, in terms of mechanical and corrosion properties, and cytotoxicity. New alloys showed comparable mechanical properties with that of the Ti-6Al-4V alloy, but increased corrosion potential, somewhat decreased breakdown potential and increased corrosion rate. There were no significant differences in cell growth on the surface of the various metal specimens, indicating that the cells cannot differentiate between the passivated surfaces of the various Ti metals. 相似文献
992.
TA Ignatowski BK Noble JR Wright JL Gorfien RR Heffner RN Spengler 《Canadian Metallurgical Quarterly》1997,79(1):84-90
Because of its wide variety of symptoms, the neurovascular compression syndrome of the upper thoracic aperture or thoracic outlet syndrome (TOS) has to be distinguished from several differential diagnoses, especially orthopedic ones. It is mainly characterized by pressure lesion of the brachial plexus and secondly, by accompanying vascular damages. An indication for surgery exists in cases of persisting or increasing complaints or function loss of shoulder, arm or hand muscles as well as in cases with occurrence of vascular damage. The treatment of choice consists of transaxillary resection of the first rib. This report presents a record of our results after transaxillary surgery and compares them to the results given in current international literature. During the last few years 3031 cases of transaxillary resections (13-473 cases) were described in international literature. The average follow-up period was 7.8 years (2-22 years). The results were good in 81.4% (50-93%) of the cases. From 02/80 to 03/94, we treated 67 patients with altogether 80 thoracic outlet syndromes (TOS). Each of them was treated similarly with extensive transaxillary resection of the first rib, excision of fibrous bands and, if necessary, of cervical ribs. Our results after surgery (84.5% of complete resolution or improvement of symptoms) compare favorably to those given by other authors. The average follow-up period was 6.6 years (0.5-14 years). Our results confirm, that transaxillary resection of the first rib is the method of choice in the treatment of thoracic outlet syndromes. 相似文献
993.
AR Gould AD Hyatt R Lunt JA Kattenbelt S Hengstberger SD Blacksell 《Canadian Metallurgical Quarterly》1998,54(2):165-187
A novel lyssavirus isolated from Pteropid bats in Australia (Australian Bat Lyssavirus, ABLV) has been characterised using gene sequence analyses, electron microscopy and a panel of monoclonal antibodies. Electron microscopic examination of Pteropid bat and mouse brain material as well as virus isolated from tissue culture medium, showed the presence of bullet-shaped rhabdovirus particles and structures characteristic of lyssavirus. Analysis using nucleocapsid (N) specific monoclonal antibodies, showed a strong relationship between this new lyssavirus and serotype 1 rabies. The nucleotide sequence of the prototype strain of ABLV was determined from the initiator methionine codon for the nucleocapsid protein (N protein) to the amino terminus of the polymerase gene (L protein), a distance of 5344 nucleotides. Comparisons of the deduced N, phosphoprotein (P), matrix protein (M), and glycoprotein (G) proteins showed that ABLV was more closely related to serotype 1 classic rabies viruses than to other members of the Lyssavirus genus. The percent relatedness of the ABLV proteins when compared to the cognate proteins of PV (Pasteur vaccine strain) rabies was 92, 75, 87 and 75% for the N, P, M and G proteins, respectively. Phylogenetic studies of N protein sequences showed clearly that ABLV is an unrecognised member of the Lyssavirus genus and represents a new genotype, genotype 7. 相似文献
994.
KL Jang RR McCrae A Angleitner R Riemann WJ Livesley 《Canadian Metallurgical Quarterly》1998,74(6):1556-1565
The common variance among personality traits can be summarized in the factors of the five-factor model, which are known to be heritable. This study examined heritability of the residual specific variance in facet-level traits from the Revised NEO Personality Inventory. Analyses of raw and residual facet scales across Canadian (183 monozygotic [MZ] and 175 dizogotic [DZ] pairs) and German (435 MZ and 205 DZ pairs) twin samples showed genetic and environmental influences of the same type and magnitude across the 2 samples for most facets. Additive genetic effects accounted for 25% to 65% of the reliable specific variance. Results provide strong support for hierarchical models of personality that posit a large number of narrow traits in addition to a few broader trait factors or domains. Facet-level traits are not simply exemplars of the broad factors they define; they are discrete constructs with their own heritable and thus biological basis. 相似文献
995.
PURPOSE: We examine the clinical prognostic value of the currently available simple and inexpensive immunoenzymatic prostatic acid phosphatase (PAP) assay for the staging and prognosis of radical prostatectomy cases. MATERIALS AND METHODS: Between February 1, 1990 and May 3, 1996 pretreatment PAP was measured in 295 patients who underwent radical prostatectomy. From February 1, 1990 to May 17, 1992 the Hybritech Tandem-E assay was used in 75 cases, from May 18, 1992 to February 28, 1993 the Abbott EIA assay was used in 49 and from March 1, 1993 to May 3, 1996 the Abbott IMx assay was used in 171. PAP assays were analyzed individually and the results were combined with pretreatment prostate specific antigen (PSA) values to assess the ability to predict organ confined prostate cancer and serological recurrence after radical prostatectomy. RESULTS: PAP testing was not of value for predicting organ confined disease or positive margins. However, this test was useful for predicting the first serological PSA recurrence in the 3 periods (77 to 85% correct) and overall (82% correct, p < 0.001, odds ratio 6.06). The Kaplan-Meier disease-free survival rate at 4 years was 78.8% for men with PAP less than 3 ng./ml. and 38.8% for those with PAP 3 ng./ml. or greater, which was significant when pretreatment PSA was less than 10 ng./ml. (p = 0.047), 10 ng./ml. or greater (p = 0.012) and overall (p < 0.001). PAP testing added prognostic information to pretreatment PSA values and it was an independent predictor of recurrence. CONCLUSIONS: The widely available and inexpensive PAP assays of the 1990s are predictors of recurrence after radical prostatectomy. They should be included in future studies of prostate cancer recurrence modeling. However, they do not predict pathological stage or margin status. 相似文献
996.
RR Russell GW Cline PH Guthrie GW Goodwin GI Shulman H Taegtmeyer 《Canadian Metallurgical Quarterly》1997,100(11):2892-2899
Myocardial glucose use is regulated by competing substrates and hormonal influences. However, the interactions of these effectors on the metabolism of exogenous glucose and glucose derived from endogenous glycogen are not completely understood. In order to determine changes in exogenous glucose uptake, glucose oxidation, and glycogen enrichment, hearts were perfused with glucose (5 mM) either alone, or glucose plus insulin (40 microU/ml), glucose plus acetoacetate (5 mM), or glucose plus insulin and acetoacetate, using a three tracer (3H, 14C, and 13C) technique. Insulin-stimulated glucose uptake and lactate production in the absence of acetoacetate, while acetoacetate inhibited the uptake of glucose and the oxidation of both exogenous glucose and endogenous carbohydrate. Depending on the metabolic conditions, the contribution of glycogen to carbohydrate metabolism varied from 20-60%. The addition of acetoacetate or insulin increased the incorporation of exogenous glucose into glycogen twofold, and the combination of the two had additive effects on the incorporation of glucose into glycogen. In contrast, the glycogen content was similar for the three groups. The increased incorporation of glucose in glycogen without a significant change in the glycogen content in hearts perfused with glucose, acetoacetate, and insulin suggests increased glycogen turnover. We conclude that insulin and acetoacetate regulate the incorporation of glucose into glycogen as well as the relative contributions of exogenous glucose and endogenous carbohydrate to myocardial energy metabolism by different mechanisms. 相似文献
997.
Triose phosphate isomerase (TIM) is a diffusion-controlled enzyme whose rate is limited by the diffusional encounter of the negatively charged substrate glyceraldehyde 3-phosphate (GAP) with the homodimeric enzyme's active sites. Translational and orientational steering of GAP toward the active sites by the electrostatic field of chicken muscle TIM has been observed in previous Brownian dynamics (BD) simulations. Here we report simulations of the association of GAP with TIMs from four species with net charges at pH 7 varying from -12e to +12e. Computed second-order rate constants are in good agreement with experimental data. The BD simulations and computation of average Boltzmann factors of substrate-protein interaction energies show that the protein electrostatic potential enhances the rates for all the enzymes. There is much less variation in the computed rates than might be expected on the basis of the net charges. Comparison of the electrostatic potentials by means of similarity indices shows that this is due to conservation of the local electrostatic potentials around the active sites which are the primary determinants of electrostatic steering of the substrate. 相似文献
998.
999.
We sought to examine the diagnosis and treatment experiences of women in the United States who reported having been diagnosed with premenstrual syndrome (PMS) by a physician. A survey of 220 women, randomly selected, ages 26-56, who subscribed to a woman's health newsletter and reported being given a diagnosis of PMS by a physician was conducted. Subjects reported (1) they sought medical help for 5.33 +/- 6.23 years before receiving a diagnosis, (2) they sought help from 3.75 +/- 3.22 physicians for PMS symptoms, (3) they thought the majority (71%) of physicians they used were not adequately informed to diagnose and treat them, (4) only a minority (23%) of physicians used a symptom chart, currently the only way to confirm a PMS diagnosis, when determining their diagnosis, and (5) only approximately 1 in 4 (26%) physicians provided them with a helpful treatment. Seventy-six percent of subjects reported that a PMS diagnosis resulted from their own suggestion, with an agreement by the physician. Eighty-one percent reported that the initial suggestion of PMS came from a non-medical source. The most commonly recommended and used treatments were vitamins, exercise, and diet modification. Current treatment satisfaction was 15.6% not very satisfied, 48.8% somewhat satisfied, and 35% very satisfied. Satisfaction was higher if natural progesterone or hysterectomy with oophorectomy was included as a treatment, although a high percentage of satisfaction was seen with several treatments. Data indicate that physicians from whom most of the women sought care between 1974 and 1994 failed to recognize, diagnose, or treat their PMS using the standards and protocols published in the medical literature. 相似文献
1000.