全文获取类型
收费全文 | 1726篇 |
免费 | 18篇 |
专业分类
电工技术 | 3篇 |
综合类 | 3篇 |
化学工业 | 52篇 |
金属工艺 | 9篇 |
机械仪表 | 5篇 |
建筑科学 | 2篇 |
能源动力 | 4篇 |
轻工业 | 18篇 |
无线电 | 23篇 |
一般工业技术 | 47篇 |
冶金工业 | 1562篇 |
原子能技术 | 3篇 |
自动化技术 | 13篇 |
出版年
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 9篇 |
2014年 | 5篇 |
2013年 | 16篇 |
2012年 | 8篇 |
2011年 | 14篇 |
2010年 | 6篇 |
2009年 | 11篇 |
2007年 | 4篇 |
2006年 | 3篇 |
2005年 | 3篇 |
2004年 | 5篇 |
2003年 | 6篇 |
2002年 | 2篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 28篇 |
1998年 | 422篇 |
1997年 | 257篇 |
1996年 | 173篇 |
1995年 | 100篇 |
1994年 | 77篇 |
1993年 | 107篇 |
1992年 | 9篇 |
1991年 | 14篇 |
1990年 | 8篇 |
1989年 | 7篇 |
1988年 | 11篇 |
1987年 | 13篇 |
1986年 | 9篇 |
1985年 | 8篇 |
1983年 | 4篇 |
1982年 | 14篇 |
1981年 | 24篇 |
1980年 | 29篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 92篇 |
1976年 | 185篇 |
1975年 | 9篇 |
1966年 | 1篇 |
1955年 | 1篇 |
1954年 | 1篇 |
1939年 | 1篇 |
排序方式: 共有1744条查询结果,搜索用时 31 毫秒
51.
Expansion of DNA trinucleotide repeats (TNRs) is the causative mutation in a growing number of human genetic diseases. Large expansions of a CTG tract were obtained and shown by genetic and physical assays to be length-dependent sites of chromosome breakage in Saccharomyces cerevisiae. Deletion of RAD27, which encodes a nuclease involved in Okazaki fragment processing, caused length-dependent destabilization of CTG tracts and a substantial increase in expansion frequency. The genetic assay described here can be used to evaluate other factors that induce TNR expansion or chromosome fragility in humans. 相似文献
52.
53.
54.
The course of diffuse peritonitis has been followed up in 219 patients, 20 of these with the reactive, 165 with toxic, and 34 with the terminal stages of the condition. Multiple-modality intensive care included, besides routine therapy, local abdominal hypothermia, UV irradiation of autoblood (UVIAB), and, if indicated, hyperbaric oxygenation (HBO) and hemoperfusion. In addition to clinical tests, immunobiochemical monitoring of medium-molecular peptide fractions MM1 and MM2 and index of their distribution, as well as of circulating immune complexes CIC1 and CIC2 and the levels of immunoglobulins IgA, IgM, and IgG were the criteria for assessing the severity of intoxication and efficacy of intensive care and for predicting the course and outcome of the disease. The results indicate that HBO in combination with hemoperfusion, local abdominal hypothermia, and UVIAB have a positive impact on the clinical picture of the disease and on the time course of markers of endogenous intoxication and humoral immunity in patients with the terminal and toxic phases of diffuse peritonitis. 相似文献
55.
KS Makarova IuI Vul'f IA Seledtsov VA Ratner 《Canadian Metallurgical Quarterly》1995,31(12):1614-1629
Transposons of gypsy group are assigned to LTR-containing retrotransposons present in the genomes of invertebrates, fungi, and plants. In this work, a theoretical analysis of the potential products of ORFs of these retrotranposons was conducted. Alignments were obtained and trees of similarity were constructed for domains of the POL region. On the basis of the obtained data, two hypothetically monophyletic subgroups of transposons were distinguished within the framework of the gypsy group, settling the genomes of taxonomically related organisms (the subgroup of "true" gypsy of insects and the subgroup of gypsy-like transposons of plants and fungi). A number of peculiarities of the topology of these trees hypothetically indicate cases of genetic conversion and recombination of domains accompanying the evolution of this group. The amino acid substitution fixation rate was evaluated on the basis of comparison of sequences of the protein products of ORFs. Estimates of the time of divergence of subgroups of gypsy-group transposons are significantly less than estimates of the times of divergence of their host species. One explanation for this discrepancy might be the hypothesis of settlement by transposons of the genomes of isolated host species. 相似文献
56.
High Conductivity in Molecularly p‐Doped Diketopyrrolopyrrole‐Based Polymer: The Impact of a High Dopant Strength and Good Structural Order
下载免费PDF全文
![点击此处可从《Advanced materials (Deerfield Beach, Fla.)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yevhen Karpov Tim Erdmann Ivan Raguzin Mahmoud Al‐Hussein Marcus Binner Uwe Lappan Manfred Stamm Kirill L. Gerasimov Tetyana Beryozkina Vasiliy Bakulev Denis V. Anokhin Dimitri A. Ivanov Florian Günther Sibylle Gemming Gotthard Seifert Brigitte Voit Riccardo Di Pietro Anton Kiriy 《Advanced materials (Deerfield Beach, Fla.)》2016,28(28):6003-6010
57.
AM Jackson AV Ivshina O Senko A Kuznetsova A Sundan MA O'Donnell S Clinton AB Alexandroff PJ Selby K James VA Kuznetsov 《Canadian Metallurgical Quarterly》1998,159(3):1054-1063
PURPOSE: The goal of this research was to discover new biological indicators in urine which could be used for short-term prognosis of local Bacillus Calmette-Guerin (BCG) therapy outcome in patients with superficial bladder cancer. PATIENTS AND METHODS: We measured and statistically evaluated soluble immunological molecules in urine from bladder cancer patients (n = 34) receiving BCG intravesically. Urine was collected following each of 6 weekly treatments, processed and assayed. The data base included measurements of interleukin-1 (IL-2, IL-4, IL-6, IL-10, IL-12, soluble intercellular adhesion molecule-1 (sICAM-1), tumour necrosis factor-alpha (TNF alpha), soluble CD14 (sCD14), interferon-gamma (IFN gamma), GM-CSF, volume of urine and its pH. The clinical response was evaluated by urine histology and random quadrant biopsy 3 months after the start of therapy. Patients were divided into 2 groups, with good and poor therapeutic effect. The initial complete response rate was 62% (21/34). The data base was analyzed using traditional multivariate statistical methods and a pattern recognition method which deals with combinatorial-statistical analysis (statistically weighted syndromes (SWS) method) of the gradated features. The SWS method is capable of identifying robust patterns in small "fuzzy" sets with high dimensional objects and some missing values. RESULTS: Only one parameter gave significant differences at p < 0.05, GM-CSF at instillation 6. Repeated measurement analysis of variance, backward stepwise multiple logistic regression and linear discriminant analysis failed to show any significance. However, significant differences in the structure of correlation between features in the groups with and without therapeutic effect were observed and four highly informative variables (the masses of sICAM-1, TNF alpha, sCD14 and pH) relating to 5th-6th installations were selected by SWS. These features provided accurate individual prediction of therapeutic outcome for all our patients. Cross-validation analysis and computer simulation showed the statistically significant stability of the prediction. CONCLUSION: We have selected a set of urinary variables that could be considered as a perspective combination of indicators (syndromes) of outcome of pre-operation BCG therapy of patients with superficial bladder cancer. A larger patient database will provide testing and evaluation of the biological and clinical significance of selected features. The computational syndrome-disease approach should be applicable for the solution of decision-making problems for management of cancer. 相似文献
58.
JM Warnecke JP Fürste WD Hardt VA Erdmann RK Hartmann 《Canadian Metallurgical Quarterly》1996,93(17):8924-8928
To study the cleavage mechanism of bacterial Nase P RNA, we have synthesized precursor tRNA substrates carrying a single Rp- or Sp-phosphorothioate modification at the RNase P cleavage site. Both the Sp- and the Rp-diastereomer reduced the rate of processing by Escherichia coli RNase P RNA at least 1000-fold under conditions where the chemical step is rate-limiting. The Rp-modification had no effect and the Sp-modification had a moderate effect on precursor tRNA ground state binding to RNase P RNA. Processing of the Rp-diastereomeric substrate was largely restored in the presence of the "thiophilic" Cd2+ as the only divalent metal ion, demonstrating direct metal ion coordination to the (pro)-Rp substituent at the cleavage site and arguing against a specific role for Mg(2+)-ions at the pro-Sp oxygen. For the Rp-diastereomeric substrate, Hill plot analysis revealed a cooperative dependence upon [Cd2+] of nH = 1.8, consistent with a two-metal ion mechanism. In the presence of the Sp-modification, neither Mn2+ nor Cd2+ was able to restore detectable cleavage at the canonical site. Instead, the ribozyme promotes cleavage at the neighboring unmodified phosphodiester with low efficiency. Dramatic inhibition of the chemical step by both the Rp- and Sp-phosphorothioate modification is unprecedented among known ribozymes and points to unique features of transition state geometry in the RNase P RNA-catalyzed reaction. 相似文献
59.
BM Mytskan BV Shchutka VA Shakhlamov MA Mytskan 《Canadian Metallurgical Quarterly》1993,116(8):208-210
Under increased muscular activity in some muscular fibers disintegration areas of myofibrillar apparatus has been revealed. Migration of myonuclei into these microregions starts the mechanism of their segregation due to plasmolemma produced from the reticulum sarcoplasmaticum and triad systems surface. After plasmolemma production in "sarcocytes" intensive development and differentiation of organellae occur. As a result of differentiation "sarcocytes" transform in to myosatellitocytes of type-2 and migrate under lamina externa muscular fibers. So, a hypothesis about formation of myogenic tissue's cellular phase from the myosymplastic one has been confirmed. 相似文献
60.
GM Roshchina EB Lishnevskaia IA Sizova VA Orlova IM Tereshin 《Canadian Metallurgical Quarterly》1980,25(11):850-854
The technique of accumulating preparation of the mucosa and "turned out sac" was used to show that levorin, a polyenic antibiotic in a concentration of 10(-6) M, lowered the transport rate and accumulation of glucose by the epithelial cells of the rat thin intestine under conditions of oxygenation. Suppression of the glucose transport in the first stages resulted in partial inhibition of the transmembrane transfer. It is suggested that levorin suppression of the glucose transport through the erythrocyte apical membrane in the thin intestine is associated with a decrease in the electrochemical gradient of Na+. 相似文献