全文获取类型
收费全文 | 6569篇 |
免费 | 82篇 |
国内免费 | 15篇 |
专业分类
电工技术 | 38篇 |
综合类 | 15篇 |
化学工业 | 456篇 |
金属工艺 | 54篇 |
机械仪表 | 54篇 |
建筑科学 | 116篇 |
矿业工程 | 34篇 |
能源动力 | 114篇 |
轻工业 | 354篇 |
水利工程 | 22篇 |
石油天然气 | 14篇 |
武器工业 | 1篇 |
无线电 | 269篇 |
一般工业技术 | 366篇 |
冶金工业 | 4413篇 |
原子能技术 | 31篇 |
自动化技术 | 315篇 |
出版年
2022年 | 23篇 |
2021年 | 50篇 |
2020年 | 22篇 |
2019年 | 31篇 |
2018年 | 42篇 |
2017年 | 29篇 |
2016年 | 45篇 |
2015年 | 50篇 |
2014年 | 78篇 |
2013年 | 136篇 |
2012年 | 106篇 |
2011年 | 130篇 |
2010年 | 96篇 |
2009年 | 100篇 |
2008年 | 136篇 |
2007年 | 120篇 |
2006年 | 96篇 |
2005年 | 106篇 |
2004年 | 77篇 |
2003年 | 76篇 |
2002年 | 64篇 |
2001年 | 74篇 |
2000年 | 44篇 |
1999年 | 168篇 |
1998年 | 1422篇 |
1997年 | 841篇 |
1996年 | 501篇 |
1995年 | 314篇 |
1994年 | 241篇 |
1993年 | 272篇 |
1992年 | 78篇 |
1991年 | 56篇 |
1990年 | 74篇 |
1989年 | 67篇 |
1988年 | 70篇 |
1987年 | 58篇 |
1986年 | 63篇 |
1985年 | 59篇 |
1984年 | 21篇 |
1983年 | 30篇 |
1982年 | 29篇 |
1981年 | 32篇 |
1980年 | 44篇 |
1978年 | 29篇 |
1977年 | 103篇 |
1976年 | 204篇 |
1975年 | 23篇 |
1973年 | 17篇 |
1972年 | 12篇 |
1969年 | 12篇 |
排序方式: 共有6666条查询结果,搜索用时 0 毫秒
961.
SJ Montain SA Smith RP Mattot GP Zientara FA Jolesz MN Sawka 《Canadian Metallurgical Quarterly》1998,84(6):1889-1894
The purpose of this study was to determine whether hypohydration reduces skeletal muscle endurance and whether increased H+ and Pi might contribute to performance degradation. Ten physically active volunteers (age 21-40 yr) performed supine single-leg, knee-extension exercise to exhaustion in a 1.5-T whole body magnetic resonance spectroscopy (MRS) system when euhydrated and when hypohydrated (4% body wt). 31P spectra were collected at a rate of one per second at rest, exercise, and recovery, and were grouped and averaged to represent 10-s intervals. The desired hydration level was achieved by having the subjects perform 2-3 h of exercise in a warm room (40 degrees C dry bulb, 20% relative humidity) with or without fluid replacement 3-8 h before the experiment. Time to fatigue was reduced (P < 0.05) by 15% when the subjects were hypohydrated [213 +/- 12 vs. 251 +/- 15 (SE) s]. Muscle strength was generally not affected by hypohydration. Muscle pH and Pi/beta-ATP ratio were similar during exercise and at exhaustion, regardless of hydration state. The time constants for phosphocreatine recovery were also similar between trials. In summary, moderate hypohydration reduces muscle endurance, and neither H+ nor Pi concentration appears to be related to these reductions. 相似文献
962.
A Pillay H Liu CY Chen B Holloway AW Sturm B Steiner SA Morse 《Canadian Metallurgical Quarterly》1998,25(8):408-414
PURPOSE: Psychosocial distress and patient attitude towards psychosocial support as well as the correlations with clinical and sociodemographic characteristics should be assessed. METHODS: The stress due to cancer was measured in a consecutive sample of tumor patients at the start of radiotherapy (n = 117) by use of the Hornheide Questionnaire. In addition, the interest of these patients in professional psychosocial support was assessed with the help of the Questionnaire for Psychosocial Support. RESULTS: Patients in the course of radiotherapy and patients with a poor prognosis and advanced disease were more strongly distressed. 32.7% of patients wished professional psychosocial support from the oncologist treating them, 40.6% of the patients wished support from the oncologist and additionally from a psychotherapist or social worker. Interest in professional psychosocial support correlated with the amount of distress, but not with sociodemographic variables. CONCLUSIONS: Results stress the importance of training programs for oncologists in order to improve their ability to detect psychosocial distress in cancer patients and to offer adequate emotional support to them. 相似文献
963.
964.
Microbial transformation of resveratrol (1), trans-3,4', 5-trihydroxystilbene, was studied. Preparative scale biotransformation of 1 with whole-cell suspensions of Bacillus cereus UI 1477 resulted in the production of metabolite 2 which was identical in all respects to an authentic sample of piceid, resveratrol 3-O-beta-D-glucoside. 相似文献
965.
CJ Jessup MA Pfaller SA Messer J Zhang M Tumberland EK Mbidde MA Ghannoum 《Canadian Metallurgical Quarterly》1998,36(10):2874-2876
We compared the yeast nitrogen base (YNB) broth microdilution method with the National Committee for Clinical Laboratory Standards (NCCLS) M27-A microdilution reference method for measuring the in vitro susceptibility of Cryptococcus neoformans isolates to fluconazole. A total of 149 isolates of C. neoformans var. neoformans from Ugandan AIDS patients was tested by both methods. An overall agreement of 88% between the two microdilution methods was observed. All isolates grew well in both RPMI 1640 and YNB media, and MICs could be read after 48 h of incubation by both methods. The range of fluconazole MICs obtained with the YNB method was broader than that obtained with the NCCLS method. The extended range of MICs provided by the YNB method may be of clinical value, as it appears that the clinical outcome may be better among patients infected with strains inhibited by lower concentrations of fluconazole as determined by the YNB method. The YNB method appears to be a viable option for testing C. neoformans against fluconazole. 相似文献
966.
D Fernandez-Reyes AG Craig SA Kyes N Peshu RW Snow AR Berendt K Marsh CI Newbold 《Canadian Metallurgical Quarterly》1997,6(8):1357-1360
The malarial parasite Plasmodium falciparum has acted as a potent selective force on the human genome. The particular virulence of this organism is thought to be due to the adherence of parasitised red blood cells to small vessel endothelium through several receptors, including CD36, thrombospondin and intercellular adhesion molecule 1 (ICAM-1, CD54), and parasite isolates differ in their ability to bind to each. Immunohistochemical studies have implicated ICAM-1 as of potential importance in the pathogenesis of cerebral malaria, leading us to reason that if any single receptor were involved in the development of cerebral malaria, then in view of the high mortality of that complication, natural selection should have produced variants with reduced binding capacity. We therefore sequenced the N-terminal domain of ICAM-1 from a number of Africans and discovered a single mutation present at high frequency. Genotypes at this locus from samples from a case-control study indicated an association of the polymorphism with the severity of clinical malaria such that individuals homozygous for the mutation have increased susceptibility to cerebral malaria with a relative risk of two. These counterintuitive results have implications for the mechanism of malaria pathogenesis, resistance to other infectious agents and transplantation immunology. 相似文献
967.
RA de Man AI Bartholomeusz HG Niesters PE Zondervan SA Locarnini 《Canadian Metallurgical Quarterly》1998,29(4):669-675
BACKGROUND/AIMS: The purpose of this study was to characterize the clinical, histological and virological events in an orthotopic liver transplant (OLT) recipient with recurrent hepatitis B infection who was initially managed with hepatitis B immune globulin (HBIg) and when viral recurrence occurred, with nucleoside analogue salvage therapy. The aims were to document the mutations occurring in the hepatitis B virus (HBV) polymerase gene as a consequence of HBIg escape, famciclovir non-response and subsequent lamivudine resistance. METHODS: Throughout the follow-up of 796 days, the patient was seen at least at 4-week intervals. Clinical, biochemical and virological data were registered according to protocol. HBV DNA was quantified throughout the treatment period. The viral polymerase gene was sequenced from serum samples collected at representative time intervals. Consecutive liver biopsies were scored according to the modified Knodell classification. RESULTS: Clinically, the patient was in excellent condition until the development of acute hepatitis during the lamivudine therapy period, 765 days post-OLT. Until this terminal event, serum transaminase activity was only 1-2 times the upper limit of normal with serum bilirubin and prothrombin time within the normal range. Subsequent liver biopsies showed chronic active hepatitis with no signs of fibrosis. The post-mortem biopsy showed severe acute hepatitis B with massive necrosis. The HBV polymerase gene was sequenced during HBIg, famciclovir and lamivudine treatment. One mutation I533L was detected during HBIg treatment. No amino acid changes were selected during famciclovir treatment. Three amino acid changes were selected while the patient was on lamivudine treatment, which include L533I, S559T and M550I. CONCLUSIONS: We have documented HBV recurrence in a liver transplant recipient with the emergence of a multidrug resistant HBV which caused graft loss. The primary resistance to famciclovir in spite of therapeutic penciclovir levels may be as a result of a combination of the mutations found in the polymerase region. After 300 days of lamivudine treatment, a drug-resistant population emerged which was associated with a greater than three log increase in HBV DNA and contributed to loss of graft function. This is the first report of such an adverse clinical outcome due to the emergence of a mutant virus as a consequence of immunoprophylactic and antiviral therapy in a liver transplant recipient. 相似文献
968.
Capsaicin, the vanilloid responsible for the pungent taste of hot peppers, binds to receptors found primarily in polymodal nociceptors. Capsaicin initially stimulates polymodal nociceptors and subsequently inhibits them from responding to a variety of stimuli. This property makes it useful clinically as an analgesic and anti-inflammatory compound. There is mounting, albeit indirect, evidence for the existence of several subtypes of vanilloid receptors. One such piece of evidence comes from studying analogues of capsaicin, such as phorbol 12-phenylacetate 13 acetate 20-homovanillate. This compound binds to (capsaicin) vanilloid receptors on sensory neurons, but unlike capsaicin it is non-pungent and does not produce hypothermia. To determine how sensory neurons respond to phorbol 12-phenylacetate 13 acetate 20-homovanillate, and to compare these responses with those evoked by capsaicin, whole-cell patch-clamp measurements were performed on cultured rat trigeminal ganglion neurons. It was found that 63% of the neurons held at -60 mV were activated by 3 microM, phorbol 12-phenylacetate 13 acetate 20-homovanillate, and 87% of these were also activated by 1 microM capsaicin. In a given neuron, phorbol 12-phenylacetate 13 acetate 20-homovanillate, like capsaicin, could activate kinetically distinct inward currents. The current-voltage curves characterizing phorbol 12-phenylacetate 13 acetate 20-homovanillate responses were asymmetric and had reversal potentials at -5.8 +/- 6.0 mV and 10.4 +/- 4 mV. The averaged dose-response curves for phorbol 12-phenylacetate 13 acetate 20-homovanillate were fit to the Hill equation and had binding constants (K(1/2)s) of 2.73 microM and 0.96 microM and Hill coefficients (ns) of approximately 1 for a rapidly- and slowly-activating current, respectively. These parameters are consistent with those obtained from binding experiments and calcium-influx experiments on sensory nerves. Repeated applications of phorbol 12-phenylacetate 13 acetate 20-homovanillate every 3 min caused a complete reduction in the rapidly-activating currents leaving only a reduced slowly-activating current. This provides strong evidence for the independence of these currents and the existence of subtypes of vanilloid receptors. Additional evidence for the existence of receptor subtypes is that 10 microM capsazepine, a specific and competitive inhibitor of capsaicin-evoked responses, did not inhibit the phorbol 12-phenylacetate 13 acetate 20-homovanillate-induced currents in some neurons and partially inhibited them in other neurons. Thus, there are capsazepine-sensitive and capsazepine-insensitive subtypes of vanilloid receptors. In summary, we have obtained electrophysiological and pharmacological evidence for distinct subtypes of vanilloid receptors. 相似文献
969.
JR Henry KC Rupert JH Dodd IJ Turchi SA Wadsworth DE Cavender PH Schafer JJ Siekierka 《Canadian Metallurgical Quarterly》1998,8(23):3335-3340
The MAP kinase p38 plays a key role in the biosynthesis of the inflammatory cytokines TNF-alpha and IL-1. We have developed a novel series of potent p38 inhibitors that could lead to new methods of treatment for inflammatory diseases such as rheumatoid arthritis and inflammatory bowel disease. 相似文献
970.
SA Brod M Malone S Darcan M Papolla L Nelson 《Canadian Metallurgical Quarterly》1998,41(10):1227-1232
Glutamine is an important gluconeogenic amino acid in postabsorptive humans. To assess the effect of glucagon on renal and hepatic glutamine gluconeogenesis, we infused six normal healthy postabsorptive subjects with glucagon at a rate chosen to produce circulating glucagon concentrations found during hypoglycemia and, using a combination of isotopic and net balance techniques, determined the systemic, renal, and hepatic glucose release and renal and hepatic production of glucose from glutamine. Infusion of glucagon increased systemic and hepatic glucose release (both P < .02), but had no effect on renal glucose release (P = .26). Systemic and hepatic glutamine gluconeogenesis increased from 0.45 +/- 0.3 and 0.11 +/- 0.02 micromol x kg(-1) x min(-1), respectively, to 0.61 +/- 0.04 (P = .002) and 0.31 +/- 0.03 micromol x kg(-1) x min(-1) (P = .001), respectively, whereas renal glutamine gluconeogenesis was unchanged (from 0.33 +/- 0.03 to 0.30 +/- 0.04 micromol x kg(-1) x min(-1), P = .20). The hepatic contribution to systemic glutamine gluconeogenesis increased from 25.2% +/- 6.2% to 51.6% +/- 5.5% (P = .002), while that of the kidney decreased from 74.8% +/- 6.2% to 48.4% +/- 5.5% (P = .003). Glucagon had no effect on the renal net balance, fractional extraction, or uptake and release of either glucose or glutamine. We thus conclude that glucagon stimulates glutamine gluconeogenesis in normal postabsorptive humans, predominantly due to an increase in hepatic glutamine conversion to glucose. Thus, under certain conditions such as counterregulation of hypoglycemia, the liver may be an important site of glutamine gluconeogenesis. 相似文献