全文获取类型
收费全文 | 1060篇 |
免费 | 9篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 10篇 |
金属工艺 | 2篇 |
机械仪表 | 6篇 |
建筑科学 | 7篇 |
能源动力 | 1篇 |
轻工业 | 28篇 |
水利工程 | 3篇 |
石油天然气 | 1篇 |
无线电 | 42篇 |
一般工业技术 | 20篇 |
冶金工业 | 922篇 |
原子能技术 | 1篇 |
自动化技术 | 23篇 |
出版年
2022年 | 1篇 |
2021年 | 2篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2017年 | 4篇 |
2016年 | 1篇 |
2015年 | 3篇 |
2014年 | 5篇 |
2013年 | 7篇 |
2012年 | 5篇 |
2011年 | 3篇 |
2010年 | 6篇 |
2009年 | 6篇 |
2008年 | 8篇 |
2007年 | 5篇 |
2006年 | 7篇 |
2005年 | 5篇 |
2004年 | 13篇 |
2003年 | 11篇 |
2002年 | 4篇 |
2001年 | 5篇 |
2000年 | 5篇 |
1999年 | 34篇 |
1998年 | 283篇 |
1997年 | 144篇 |
1996年 | 125篇 |
1995年 | 65篇 |
1994年 | 40篇 |
1993年 | 56篇 |
1992年 | 14篇 |
1991年 | 14篇 |
1990年 | 20篇 |
1989年 | 19篇 |
1988年 | 6篇 |
1987年 | 14篇 |
1986年 | 6篇 |
1985年 | 19篇 |
1984年 | 4篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1977年 | 20篇 |
1976年 | 45篇 |
1975年 | 2篇 |
1974年 | 1篇 |
1973年 | 3篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有1069条查询结果,搜索用时 15 毫秒
121.
PURPOSE: Long-term results of cutting seton in the treatment of anal fistulas were studied. METHODS: Of the 44 patients with anal fistulas, mainly of the high variety, managed with this method, 35 (25 men) attended a clinical and manometric follow-up examination on average 70 (range, 28-184) months after operation. Fistula distribution was high transsphincteric (25), low transsphincteric (5), extrasphincteric (3), and suprasphincteric (2). The seton was tightened at one-week to two-week intervals to achieve gradual sphincter division. RESULTS: Time required to achieve complete fistula healing ranged from 37 to 557 (mean, 151) days. Two (6 percent) of the 35 patients re-examined had recurrence of fistula and 22 (63 percent) reported symptoms of minor impairment in anal control, which in four patients had existed already before operation. Anal resting pressures were similar for defective and normal control, but other manometric variables were inferior in incontinence, although total squeeze pressure only showed statistically significant difference from normal continence (P = 0.0345). Incontinence was likely associated with hard and gutter-shaped operation scars in the anal canal, but the difference from normal continence was not statistically significant. CONCLUSION: Cutting seton yields fairly good results in regard to cure of fistula, but the risk of anal incontinence, despite its minor degree, seems to be too high to recommend its routine use for all high fistulas. The suprasphincteric fistulas and some extrasphincteric fistulas are difficult to treat otherwise, but especially for high transsphincteric fistulas, other methods of treatment (preferably those in which sphincter division can be avoided and the risk of anal canal deformity and incontinence are minimized) are advocated. 相似文献
122.
Early radical cystectomy for a high-grade tumor invading the lamina propria (T1) remains controversial. In 1997, we cannot identify accurately which of these high-risk tumors will progress to muscle-invasive disease and metastases. In the near future, urologists may be able to use the presence of genetic alterations, such as p53 mutations, to help make therapeutic decisions. Previous reports on superficial bladder cancer treated with intravesical bacillus Calmette-Guérin immunotherapy have demonstrated a decrease in recurrence and progression. Unfortunately, there is no reliable method to predict which patients with a high-grade T1 tumor will fail to respond to intravesical therapy. Failure of intravesical therapy to control these aggressive tumors is associated with a significant rate of pathological upstaging and metastases. Radical cystectomy will cure a high percentage of these T1 tumors with acceptable morbidity and low mortality. In an era of nerve-sparing cystectomy and orthotopic neobladder reconstruction, early radical cystectomy is an alternative that should be discussed with the patient before instituting intravesical therapy. 相似文献
123.
DR Senger KP Claffey JE Benes CA Perruzzi AP Sergiou M Detmar 《Canadian Metallurgical Quarterly》1997,94(25):13612-13617
Vascular endothelial growth factor (VEGF), also known as vascular permeability factor, is a cytokine of central importance for the angiogenesis associated with cancers and other pathologies. Because angiogenesis often involves endothelial cell (EC) migration and proliferation within a collagen-rich extracellular matrix, we investigated the possibility that VEGF promotes neovascularization through regulation of collagen receptor expression. VEGF induced a 5- to 7-fold increase in dermal microvascular EC surface protein expression of two collagen receptors-the alpha1beta1 and alpha2beta1 integrins-through induction of mRNAs encoding the alpha1 and alpha2 subunits. In contrast, VEGF did not induce increased expression of the alpha3beta1 integrin, which also has been implicated in collagen binding. Integrin alpha1-blocking and alpha2-blocking antibodies (Ab) each partially inhibited attachment of microvascular EC to collagen I, and alpha1-blocking Ab also inhibited attachment to collagen IV and laminin-1. Induction of alpha1beta1 and alpha2beta1 expression by VEGF promoted cell spreading on collagen I gels which was abolished by a combination of alpha1-blocking and alpha2-blocking Abs. In vivo, a combination of alpha1-blocking and alpha2-blocking Abs markedly inhibited VEGF-driven angiogenesis; average cross-sectional area of individual new blood vessels was reduced 90% and average total new vascular area was reduced 82% without detectable effects on the pre-existing vasculature. These data indicate that induction of alpha1beta1 and alpha2beta1 expression by EC is an important mechanism by which VEGF promotes angiogenesis and that alpha1beta1 and alpha2beta1 antagonists may prove effective in inhibiting VEGF-driven angiogenesis in cancers and other important pathologies. 相似文献
124.
KP Ebmeier N Prentice A Ryman E Halloran JE Rimmington JK Best GM Goodwin 《Canadian Metallurgical Quarterly》1997,63(5):597-604
OBJECTIVES: Perfusion SPECT and MRI were used to test the hypothesis that late onset depression is associated with brain abnormalities. METHODS: Forty depressed patients (DSM-III-R major depressive episode, not demented at two year follow up) were recruited who were either drug free, or on a stable dose of antidepressants for at least three weeks, as well as 22 demented patients (DSM-IIIR and NINCDS/ADRDA criteria for probable Alzheimer's disease). Patients were imaged at rest with a high resolution single slice 12 detector head scanner (SME-Neuro 900) and the cerebral perfusion marker 99mTc-exametazime (HM-PAO). Temporal lobe templates were fitted with brains pitched by 20 degrees-30 degrees. A subgroup of 41 patients (22 depressed) were also scanned using a Siemens Magnetron 1.0 Tesla magnetic resonance imager, using a FLAIR imaging sequence for the assessment of white matter hyperintensities, and a Turbo FLASH sequence for the measurement of medial temporal lobe width. RESULTS: Demented patients showed reduced perfusion, particularly in the left temporoparietal cortex. In these regions of interest, patients with late onset depression tended to have perfusion values intermediate between patients with early onset depression and demented patients. Differences in changes in white matter between demented and early and late onset depressive patients did not reach conventional levels of significance. Temporal lobe width differed between demented and depressed patients, but not between early and late onset depressed patients. Perfusion and temporal lobe width were not associated, but reductions of perfusion were associated with periventricular white matter changes. Mini mental state examination scores were associated with temporal perfusion in demented patients and with changes in deep white matter in depressed patients. Finally, severity of depressive symptoms was associated with decreased perfusion in frontotemporal and basal ganglia regions of interest. CONCLUSION: A cumulative effect of duration of illness on regional cerebral perfusion could not be confirmed. Late onset depression may show more abnormalities of deep white matter and of left temporoparietal perfusion than early onset depression, but the underlying pathology remains to be established. 相似文献
125.
AJ Kalyani D Piper T Mujtaba MT Lucero MS Rao 《Canadian Metallurgical Quarterly》1998,18(19):7856-7868
Neuronal restricted precursors (NRPs) () can generate multiple neurotransmitter phenotypes during maturation in culture. Undifferentiated E-NCAM+ (embryonic neural cell adhesion molecule) immunoreactive NRPs are mitotically active and electrically immature, and they express only a subset of neuronal markers. Fully mature cells are postmitotic, process-bearing cells that are neurofilament-M and synaptophysin immunoreactive, and they synthesize and respond to different subsets of neurotransmitter molecules. Mature neurons that synthesize and respond to glycine, glutamate, GABA, dopamine, and acetylcholine can be identified by immunocytochemistry, RT-PCR, and calcium imaging in mass cultures. Individual NRPs also generate heterogeneous progeny as assessed by neurotransmitter response and synthesis, demonstrating the multipotent nature of the precursor cells. Differentiation can be modulated by sonic hedgehog (Shh) and bone morphogenetic protein (BMP)-2/4 molecules. Shh acts as a mitogen and inhibits differentiation (including cholinergic differentiation). BMP-2 and BMP-4, in contrast, inhibit cell division and promote differentiation (including cholinergic differentiation). Thus, a single neuronal precursor cell can differentiate into multiple classes of neurons, and this differentiation can be modulated by environmental signals. 相似文献
126.
This study compared preoperative and postoperative results for selected radiographic measurements of 30 patients undergoing the modified Austin bunionectomy procedure for the correction of hallux abducto valgus. Significant reductions in all postoperative radiographic values were demonstrated, including hallux abductus angle, metatarsus primus adductus angle, tibial sesamoid position, and first metatarsal protrusion distance. 相似文献
127.
KP Keenan P Laroque GC Ballam KA Soper R Dixit BA Mattson SP Adams JB Coleman 《Canadian Metallurgical Quarterly》1996,24(6):757-768
Ad libitum (AL) overfeeding is the most significant, uncontrolled variable affecting the outcome of the current rodent bioassay. There is a highly significant correlation between AL food consumption, the resultant obesity and body weight, and low 2-yr survival in rodents. AL feeding of diets with lowered protein, metabolizable energy (ME), and increased fiber does not improve survival. Only dietary restriction (DR) of all diets tested significantly improves survival and delays the onset of spontaneous degenerative disease (i.e., nephropathy and cardiomyopathy) and diet-related tumors. Moderate DR results in an incidence of spontaneous tumors similar to AL-fed rats, but the tumors are found incidentally and do not cause early mortality. There is a decreased age-adjusted incidence of pituitary and mammary gland tumors in moderate DR-fed rats, but tumor growth time is similar between AL and DR rats with only a delay in tumor onset time seen in DR-fed groups. Moderate DR does not significantly alter drug-metabolizing enzyme activities nor the toxicologic response to 5 pharmaceuticals tested at maximum tolerated doses (MTDs). However, moderate DR-fed rats did require much higher doses of 4 additional pharmaceutical compounds before classical MTDs were produced. Toxicokinetic studies of 2 of these compounds demonstrated equal or higher steady-state systemic exposures to parent drug and metabolites in moderate DR-fed rats. Markers of oxidative stress (lipid peroxidation, protein oxidation) are decreased and cytoprotective anti-oxidant markers are preserved in moderate DR-fed rats. But moderate DR does not delay reproductive senescence in female rats. Only marked DR delays reproductive senescence compared to AL and moderate DR-fed female rats. These and other data indicate that moderate DR is the most appropriate method of dietary control for the rodent bioassay when used to assess pharmaceuticals for human safety and compounds for risk assessment. 相似文献
128.
129.
AG Kamel N Maning S Arulmainathan S Murad A Nasuruddin KP Lai 《Canadian Metallurgical Quarterly》1994,25(4):650-653
A study conducted at the Tampin Drug Rehabilitation Center in Malaysia established a high prevalence (23%) of asymptomatic carriers of Cryptosporidium among exposed HIV positive intravenous drug users (IVDUs). A majority of them were young adults and among the ethnic groups, the Malay HIV positive inmates had the highest prevalence of Cryptosporidium infection. 相似文献
130.
RJ O'Hara J Greenman AW MacDonald KM Gaskell KP Topping GS Duthie MJ Kerin PW Lee JR Monson 《Canadian Metallurgical Quarterly》1998,4(8):1943-1948
Interleukin 12 (IL-12) is a heterodimeric cytokine that has been demonstrated to have a major role in stimulating a cell-mediated antitumor response. IL-10, a product of T helper 2 lymphocytes, is its most potent inhibitor. The aim of this study was to investigate whether patients with colorectal cancer had an imbalance in production of IL-12 and IL-10 preoperatively, and whether this was associated with advanced disease at surgery. Blood was obtained before surgery from 60 patients with colorectal cancer and from 30 controls. Peripheral blood mononuclear cells were incubated with Staphylococcus aureus Cowan's strain 1 in vitro for 24 h to assess IL-12 expression after stimulation, and serum was used for IL-10 measurement. IL-12 and IL-10 levels were assessed by ELISA. A single pathologist staged the tumors according to the tumor-node-metastasis (TNM) and Dukes' classifications. Patients with colorectal cancer had significantly lower levels of IL-12 (P <0.001) and higher levels of IL-10(P = 0.004) compared to controls. In addition, lower levels of IL-12 were detected in those patients who were node positive (P<0.05), had Dukes' C lesions (P < or = 0.001), and T3 or T4 lesions (P<0.033) when compared to controls. Patients with Dukes' B and C lesions (P<0.01) and T3 and T4 lesions (P<0.05) also had higher levels of IL-10 compared to controls. This study is the first to demonstrate that patients with colorectal cancer have decreased IL-12 production and increased serum IL-10. This suggests an impaired T helper 1 cell-mediated antitumor response and provides some justification for exogenous IL-12 therapy or anti-IL-10 therapy in these patients. 相似文献