首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1840篇
  免费   8篇
  国内免费   2篇
电工技术   8篇
化学工业   86篇
金属工艺   8篇
机械仪表   13篇
建筑科学   35篇
矿业工程   4篇
能源动力   14篇
轻工业   105篇
水利工程   4篇
无线电   57篇
一般工业技术   96篇
冶金工业   1373篇
原子能技术   6篇
自动化技术   41篇
  2021年   7篇
  2020年   14篇
  2019年   12篇
  2018年   6篇
  2017年   10篇
  2016年   10篇
  2015年   6篇
  2014年   11篇
  2013年   35篇
  2012年   16篇
  2011年   16篇
  2010年   11篇
  2009年   11篇
  2008年   26篇
  2007年   15篇
  2006年   8篇
  2005年   9篇
  2004年   16篇
  2003年   15篇
  2002年   11篇
  2001年   21篇
  2000年   14篇
  1999年   54篇
  1998年   391篇
  1997年   258篇
  1996年   148篇
  1995年   95篇
  1994年   75篇
  1993年   89篇
  1992年   15篇
  1991年   22篇
  1990年   25篇
  1989年   22篇
  1988年   19篇
  1987年   17篇
  1986年   24篇
  1985年   21篇
  1984年   10篇
  1983年   10篇
  1982年   16篇
  1981年   19篇
  1980年   12篇
  1979年   14篇
  1978年   7篇
  1977年   46篇
  1976年   82篇
  1975年   6篇
  1973年   5篇
  1970年   5篇
  1967年   5篇
排序方式: 共有1850条查询结果,搜索用时 0 毫秒
51.
52.
OBJECTIVE: To assess the effect of mixing the insulin analog lispro (Humalog) with NPH (Humulin I) before injection on lispro's fast, short action profile. RESEARCH DESIGN AND METHODS: A total of 12 healthy volunteers received subcutaneous abdominal injections of 0.1 U/kg regular insulin and 0.2 U/kg NPH insulin as follows: lispro and NPH injected separately (treatment group A), lispro and NPH mixed in the syringe up to 2 min before single injection (treatment group B), and human regular insulin and NPH mixed and injected as in group B (treatment group C), on separate occasions, in random order. Plasma glucose was maintained for 12 h by intravenous 20% glucose. Pharmacokinetic and pharmacodynamic parameters were compared by analysis of variance for repeated measures. RESULTS: Peak plasma insulin levels (2.6 +/- 0.8 vs. 2.2 +/- 0.6 vs. 1.9 +/- 0.6 ng/ml, P = 0.075), total glucose infused (121.5 +/- 32.8 vs. 135.0 +/- 49.0 vs. 117.3 +/- 39.9 mg.kg-1.min-1, P = 0.53), and maximum glucose infusion rate (GIRmax) (8.3 +/- 0.9 vs. 8.0 +/- 1.7 vs. 7.1 +/- 2.4 mg.kg-1.min-1, P = 0.65) were not significantly different between treatments. The times until peak insulin concentrations were similar in treatment groups A and B, but significantly shorter than in treatment group C (0.9 +/- 0.3 and 1.2 +/- 0.2 vs. 2.0 +/- 0.4 h, respectively, P = 0.042). The times until GIRmax were also not different (113.9 +/- 41 and 122.0 +/- 45 vs. 209.0 +/- 51.3 min, respectively, P = 0.002). The glucose infusion rate (GIR) then fell to 50% GIRmax more quickly in treatment groups A and B than in treatment group C (239.9 +/- 40.5 vs. 292.4 +/- 133.3 vs. 399.5 +/- 78.3, respectively, P = 0.005). CONCLUSIONS: The action profile of lispro is not attenuated by mixing lispro with NPH in the syringe immediately before injection. The advantages are available to those individuals who need to combine types of insulin before injection to achieve optimal diabetes control.  相似文献   
53.
A 1-year-old boy presented with pericardial effusion, pulmonary infiltrates, and disseminated intravascular coagulation; lung biopsy indicated pulmonary lymphangiomatosis. He did not respond to medical therapy and was a poor surgical candidate; therefore, he underwent partial splenic embolization. The procedure resulted in a complete disappearance of the DIC and marked improvement in his cardiorespiratory status. He continues to thrive and is transfusion-independent 2 years after the procedure.  相似文献   
54.
Harringtonine (HT), an anticancer drug with high chemotherapeutic efficiency to human chronic granulocytic/myelomonocytic leukemia, has been reported to rapidly induce apoptosis in HL-60 cells in a wide scope/range of dosage by investigators from our lab and others. In the present studies, by using video enhancement contrast (VEC) microscopy, we dynamically analyzed changes in intracellular calcium distribution in a single HL-60 cell over the period from the initiation of apoptosis to the obvious appearance of chromatin condensation. The results from this paper demonstrated the striking distinction of intracellular calcium distribution at different time points after treatment with HT. Before treatment in normal HL-60 cells the highest [Ca2+]i accumulation was observed in the peri-nuclear area and the lowest was observed in the nucleus; after treatment with 1 microg/ml HT for 30 min intracellular calcium diffused all over the cell compartments, while intranuclear calcium increased comparatively and significantly. The phenomenon of intranuclear calcium accumulation was further confirmed by using laser scanning confocal microscopy (LSCM). In addition, co-localization of the highest calcium region with condensed chromatin in apoptotic HL-60 cells was also observed by LSCM. Our results suggest that two sequential alterations of intracellular calcium distribution occurred in apoptotic HL-60 cells induced by HT, i.e. (a) accumulation of calcium in the nucleus and (b) regionalization in a specific nuclear region.  相似文献   
55.
P450 cytochromes (P450) catalyze many types of oxidative reactions, including the conversion of olefinic substrates to epoxides by oxygen insertion. In some instances epoxidation leads to the formation of products of physiological importance from naturally occurring substrates, such as arachidonic acid, and to the toxicity, carcinogenicity, or teratogenicity of foreign compounds, including drugs. In the present mechanistic study, the rates of oxidation of model olefins were determined with N-terminal-truncated P450s 2B4 and 2E1 and their respective mutants in which the threonine believed to facilitate proton delivery to the active site was replaced by alanine. Styrene epoxidation, cyclohexene epoxidation and hydroxylation to give 1-cyclohexene-3-ol, and cis- or trans-butene epoxidation (without isomerization) and hydroxylation to give 2-butene-1-ol were all significantly decreased by the 2B4 T302A mutation. Reduced proton delivery in this mutant is believed to interfere with the activation of dioxygen to the oxenoid species, as shown earlier by decreased hydroxylation of several substrates and enhanced aldehyde deformylation via a presumed peroxo intermediate. Of particular interest, however, the T303A mutation of P450 2E1 resulted in enhanced epoxidation of all of the model olefins along with decreased allylic hydroxylation of cyclohexene and butene. These results and a comparison of the ratios of the rates of epoxidation and hydroxylation support the concept that two different species with electrophilic properties, hydroperoxo-iron (FeO2H)3+ and oxenoid-iron (FeO)3+, can effect olefin epoxidation. The ability of cytochrome P450 to use several different active oxidants generated from molecular oxygen may help account for the broad reaction specificity and variety of products formed by this versatile catalyst.  相似文献   
56.
The Apteronotidae, a family of weakly electric fish from South America (Gymnotiformes), possess a structure called the dorsal filament with an unknown function and evolutionary origin. This study compared the gross anatomy of the dorsal filament of 13 species of apteronotids and used light microscopy to examine the filaments of Adontosternarchus balaenops, Apteronotus albifrons, and Apteronotus leptorhynchus. The dorsal filament is an unscaled, thin, tapering structure attached to a mid-dorsal groove on the posterior half of the fish's back. The interior of the filament is a gelatinous mucopolysaccharide matrix (connective tissue) containing blood vessels and a bilateral nerve in which nearly all the afferents are large (8-10 mu m) and heavily myelinated. The location of the anterior origin of the filament varies from 0.48 to 0.66 of the body length, posterior to the snout, in 13 species. The filament is covered with hundreds of large-type tuberous electroreceptors and some ampullary receptors, at approximately the same density and ratio as those on the nearby back. The morphology of the large-type tuberous receptors and their afferents suggests that they are phase-coding T-units. A double layer of epithelial cells separates the ventral side of the filament from the groove in the trunk of the fish, except at the anterior origin where the interior of the filament is continuous with the body. This specialized double epithelium could provide a high resistance barrier to electrical current. This study was unable to distinguish between two hypotheses: that the dorsal filament is a modified adipose fin (as suggested previously), retained only in this family of Gymnotiformes; or that it is a uniquely derived character of the Apteronotidae.  相似文献   
57.
There is an increasing interest in demand-side management (DSM) by utilities and regulators throughout the USA. With this interest, there is an increasing need for DSM evaluation. Regulators expect utility engineers to use least cost planning and integrated resource planning approaches to adjust their generation capacity plans to reflect DSM. Increasingly, utilities are considering DSM to affect their T&D capacity plans. However, major utility DSM programs are less than a decade old. This leaves many utility engineers uneasy. How do they know that DSM will be there when they really need it? To verify and improve the contribution of DSM programs, utility analysts have developed a set of methodologies and procedures for evaluating DSM. The purpose of this panel session was to review these state of the art evaluations and the lessons learned from them so far. The authors explore the differences inherent in evaluating DSM at the T&D level versus the generation level, and review DSM's persistence and reliability in the residential, commercial, and industrial sectors  相似文献   
58.
Agranulocytosis and septicaemia developing in a patient with rheumatoid arthritis after 3 years' intermittent treatment with diclofenac, cimetidine and flucloxacillin for staphylococcal osteomyelitis is described. Treatment with recombinant granulocyte-colony-stimulating factor and high-dose methylprednisolone had no effect on the neutropenia which resolved on stopping all drug therapy. Relapse of agranulocytosis followed reintroduction of flucloxacillin and cimetidine 3 months later.  相似文献   
59.
60.
Lateralized changes in tympanic membrane (TM) temperature were assessed in chimpanzees. Subjects were engaged in 1 of 3 different cognitive tasks, including matching-to-sample, visual-spatial discrimination, and a motor task. During execution of each task, TM temperatures were taken from each ear over a 20-min time period. The TM temperatures at each time interval were subtracted from a baseline measure to assess relative change in blood flow. For the matching-to-sample and visual-spatial discrimination tasks, significant lateralized changes in TM temperature were found, with left-ear temperature increasing and right-ear temperature decreasing. No laterality effects were found for the motor or control tasks. These data provide the first evidence of laterality in physiological functioning in chimpanzees and suggest that transient asymmetries in cognitive functions are associated with changes in cerebral blood flow as assessed by TM temperature change. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号