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   1944篇
  免费   0篇
化学工业   10篇
轻工业   1篇
石油天然气   1篇
无线电   2篇
一般工业技术   1篇
冶金工业   1927篇
自动化技术   2篇
  2017年   1篇
  2010年   2篇
  2007年   1篇
  2005年   1篇
  2003年   2篇
  2000年   1篇
  1999年   57篇
  1998年   570篇
  1997年   320篇
  1996年   195篇
  1995年   116篇
  1994年   113篇
  1993年   111篇
  1992年   24篇
  1991年   39篇
  1990年   27篇
  1989年   43篇
  1988年   37篇
  1987年   25篇
  1986年   26篇
  1985年   18篇
  1984年   1篇
  1983年   7篇
  1982年   13篇
  1981年   7篇
  1980年   12篇
  1979年   1篇
  1978年   2篇
  1977年   51篇
  1976年   119篇
  1975年   2篇
排序方式: 共有1944条查询结果,搜索用时 406 毫秒
121.
In this paper the Authors reviewed the recent literature for a more comprehensive and clear vision of the epidemiological and pathological aspects of retroperitoneal sarcomas. The most effective procedures for a an early and accurate diagnosis were identified. Moreover, the different therapeutic choices were taken into account focusing on those provided of the major potential in terms of oncologically valid treatment.  相似文献   
122.
In sensory hair cells of the cochlea, deflection of the stereociliary bundle results in direct mechanical gating of mechanoelectrical transduction channels, a function generally attributed to the tip link running between the tips of short stereocilia and the sides of adjacent taller ones. However, immunocytochemical experiments indicate that the channels may not be associated with the tip link but occur just below it in a region of contact between the stereocilia. To determine whether transduction channels in this location could be operated during physiologically appropriate deflections as effectively by shear displacement as if they were associated with the tip link, a two dimensional kinematic analysis of relative motion between stereocilia has been performed assuming contact between stereocilia is maintained during deflection. Bundle geometry and dimensions were determined from transmission electron micrographs of hair cells from several frequency locations between 0.27 and 13.00 kHz in the guinea-pig cochlea. The analysis indicates that for a 10 nm deflection of the tallest stereocilia of both inner and outer hair cells, i.e. within the range of the maximum sensitivity of mammalian hair bundles, the average shear displacement in the contact region would be 1.6 nm, but that it increases systematically towards higher frequency regions for outer hair cells. This displacement is comparable in magnitude to tip-link elongation for individual stereociliary pairs.  相似文献   
123.
To investigate the effects of morphine on neutrophil and endothelial activation, we measured serum levels of intercellular adhesion molecule-1 (ICAM-1), L-selectin, and neutrophil endopeptidase 24.11 (NEP) in 38 patients with acute myocardial infarction (group 1) and 16 control subjects (group 2). In group 1, all the patients underwent blood sampling at initial presentation and 10 minutes later. Twenty of them had 3 mg of morphine administered intravenously immediately after the first sampling (group 1A) and the other 18 after a second sampling (group 1B). The serum levels of ICAM-1 and L-selectin were both significantly higher in groups 1A and 1B than in group 2. In group 1A, the ICAM-1 decreased significantly at second blood samplings (310 +/- 28 vs 368 +/- 30 ng/ml; p <0.001), whereas in group 1B there was no significant change in ICAM-1 (357 +/- 33 vs 359 +/- 26 ng/ml; p = NS). In group 1A, the L-selectin decreased significantly at second blood samplings (2.3 +/- 1.2 mg/L, p <0.001 vs baseline), whereas in group 1B there was no significant change in L-selectin (3.9 +/- 1.0 mg/L, p = NS vs baseline). There was no significant difference in baseline NEP activities between groups 1A and 1B (4.89 +/- 1.22 vs 5.14 +/- 1.57 nmol/mg protein; p = NS). However, the NEP activities at second blood samplings decreased significantly in group 1A (9.88 +/- 1.86 nmol/mg protein, p <0.001 vs baseline), whereas no significant changes were observed in group 1B (5.09 +/- 1.62 nmol/mg protein, p = NS vs baseline). In conclusion, morphine increased NEP activities and thus attenuated shedding of L-selectin and ICAM-1.  相似文献   
124.
125.
The discovery of neuroendocrine differentiation in hormone-refractory prostatic adenocarcinoma has opened a potentially new therapeutic approach in this group of patients with a poor prognosis and few effective therapy modalities. Based on previous findings of increased uptake of 11C-5-hydroxytryptophan (11C-5-HTP) in neuroendocrine tumours using the PET technique, this tracer was applied in the study of 10 patients with metastatic hormone-refractory prostatic adenocarcinoma. In three patients, the study was repeated after treatment. An increased uptake of 11C-5-HTP was observed in all investigated skeletal lesions, although the magnitude of the uptake was moderate. The difference between the standard uptake values (SUV) in normal bone and metastatic lesions was significant (p < 0.001). A kinetic analysis of the uptake of 11C-5-HTP demonstrates an increase during the first minutes followed by a wash-out and a stabilization of the tissue/blood ratio at about 2. The Patlak plots demonstrated a gradual increase in the transport rate during the first 20 to 30 min, after which a constant level was observed. The SUV varied between patients and between lesions over time and treatment. The uptake of 11C-5-HTP discriminates metastatic lesions from normal bone and may thus aid in the diagnosis and, potentially, in treatment monitoring of metastatic hormone-refractory prostatic adenocarcinoma. Uptake kinetics are characterized by a wash-out and cannot alone be used as proof of neuroendocrine differentiation in hormone-refractory prostatic adenocarcinoma.  相似文献   
126.
Normal wound healing in skin embraces several reparative processes, many of which directly involve components of the extracellular matrix and the cutaneous basement membrane zone. Proteoglycans are a group of extracellular matrix macromolecules that have both structural and regulatory properties. In wound healing, certain proteoglycans fulfill a mechanical function of absorbing water and preventing tissue compression. However, proteoglycans may also have other roles in wound healing including a direct influence on inflammation, cell attachment and migration, and growth factor binding. Furthermore, proteoglycans may help to determine other aspects of the long-term quality of wound healing in skin through regulation of basement membrane permeability, epidermal hyperproliferation, and dermal fibrosis.  相似文献   
127.
128.
129.
130.
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