首页 | 官方网站   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   768篇
  免费   15篇
  国内免费   1篇
工业技术   784篇
  2023年   4篇
  2022年   2篇
  2021年   10篇
  2020年   10篇
  2019年   9篇
  2018年   16篇
  2017年   8篇
  2016年   17篇
  2015年   10篇
  2014年   14篇
  2013年   31篇
  2012年   26篇
  2011年   26篇
  2010年   17篇
  2009年   39篇
  2008年   30篇
  2007年   30篇
  2006年   23篇
  2005年   24篇
  2004年   16篇
  2003年   17篇
  2002年   17篇
  2001年   14篇
  2000年   18篇
  1999年   19篇
  1998年   90篇
  1997年   39篇
  1996年   26篇
  1995年   28篇
  1994年   20篇
  1993年   23篇
  1992年   6篇
  1991年   10篇
  1990年   9篇
  1989年   12篇
  1988年   3篇
  1987年   8篇
  1986年   7篇
  1985年   6篇
  1984年   9篇
  1983年   4篇
  1982年   6篇
  1981年   7篇
  1980年   2篇
  1979年   3篇
  1978年   2篇
  1977年   4篇
  1976年   10篇
  1975年   1篇
  1973年   2篇
排序方式: 共有784条查询结果,搜索用时 218 毫秒
91.
Compartment syndrome is caused by an increase in intracompartmental pressure above the capillary level, preventing capillary flow. The acute onset of symptoms occurs after events such as fracture, soft tissue trauma, and revascularization and usually necessitates prompt fasciotomy to avoid loss of function or even necrosis of the enclosed muscle. Compartment syndromes in athletes are of a recurrent nature and are usually referred to as chronic. Nonoperative treatment is often successful. Although compartment syndromes can occur in several anatomic regions, the most commonly seen in athletes involve the leg. Chronic compartment syndromes of the upper extremity are rare, and only a few cases have been reported in the literature. The intracompartmental pressures causing chronic symptoms in these cases ranged between 22 mm Hg at rest and 40 mm Hg after 30 minutes of exercise. Under maximal contraction, a pressure of 58 mm Hg has been recorded. The object of this paper is to report a case of a tennis player where much higher flexor-pronator muscle intracompartmental pressures than those noted above were recorded. We compared the intracompartmental pressure data of this patient with intracompartmental pressures measured in six symptom-free volunteers.  相似文献   
92.
Experiments were carried out to investigate the flow pattern, average void fraction, and pressure drop of an upward air‐water two‐phase flow in vertical tubes of 25‐mm inside diameter with wire coils of varying wire diameter, pitch, and number of coils in cross section. Five kinds of flow patterns—bubble, slug, churn, semiannular, and annular flow—were defined based on the observation of flow behavior in the experiments. At higher water flowrates, the bubble‐to‐slug transition occurred at lower air flowrates in tubes with wire coils than in smooth tubes. The average void fraction was found by using the drift flux model. Further, the experimental results of the friction pressure drop were compared with the Lockhart‐Martinelli correlation. As a result, a correlation with the constant C in Chisholm's equation was obtained as a function of the wire coil pitch‐to‐diameter ratio. © 2002 Wiley Periodicals, Inc. Heat Trans Asian Res, 31(8): 639–651, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10066  相似文献   
93.
The polyhydroxylated nortropane alkaloids called calystegines occur in many plants of the Convolvulaceae, Solanaceae, and Moraceae families. Certain of these alkaloids exhibit potent inhibitory activities against glycosidases and the recently demonstrated occurrence of calystegines in the leaves, skins, and sprouts of potatoes (Solanum tuberosum), and in the leaves of the eggplant (S. melongena), has raised concerns regarding the safety of these vegetables in the human diet. We have surveyed the occurrence of calystegines in edible fruits and vegetables of the families Convolvulaceae, Solanaceae, and Moraceae by GC-MS. Calystegines A3, B1, B2, and C1 were detected in all the edible fruits and vegetables tested; sweet and chili peppers, potatoes, eggplants, tomatoes, Physalis fruits, sweet potatoes, and mulberries. Calystegines B1 and C1 were potent competitive inhibitors of the bovine, human, and rat beta-glucosidase activities, with Ki values of 150, 10, and 1.9 microM, respectively for B1 and 15, 1.5, and 1 microM, respectively, for C1. Calystegine B2 was a strong competitive inhibitor of the alpha-galactosidase activity in all the livers. Human beta-xylosidase was inhibited by all four nortropanes, with calystegine C1 having a Ki of 0.13 microM. Calystegines A3 and B2 selectively inhibited the rat liver beta-glucosidase activity. The potent inhibition of mammalian beta-glucosidase and alpha-galactosidase activities in vitro raises the possibility of toxicity in humans consuming large amounts of plants that contain these compounds.  相似文献   
94.
95.
The present study was conducted to examine the effect of activin A on growth of rat hepatocytes. EGF induced a 10-fold increase in DNA synthesis as assessed by [3H]thymidine incorporation in cultured hepatocytes. When activin A was added together with EGF, DNA synthesis induced by EGF was markedly inhibited. Inhibition was detected at a concentration of 10(-10) M, and 5 x 10(-9) M activin A almost completely blocked EGF-mediated DNA synthesis. Similarly, activin A completely blocked DNA synthesis induced by hepatocyte growth factor/scatter factor. Activin A was capable of inhibiting EGF-mediated DNA synthesis, even when added 36 h after the addition of EGF. With the same time interval, TGF-beta also blocked EGF-induced DNA synthesis. Although both activin A and TGF-beta inhibited growth of hepatocytes in a similar manner, either activin A or TGF-beta did not compete with each other in their binding when assessed by competitive binding using an iodinated ligand. When hepatocytes were incubated with EGF, release of bioactivity of activin A into culture medium was detected after 48 h or later. Activity of activin A was released from parenchymal cells but not from nonparenchymal cells. mRNA for beta A subunit of activin was detected only slightly in unstimulated hepatocytes, but markedly increased at 48 h after the addition of EGF. To determine whether endogenously produced activin A affects DNA synthesis, we examined the effect of follistatin, an activin-binding protein that blocks the action of activin A. An addition of follistatin significantly enhanced EGF-induced DNA synthesis. Finally, in partial hepatectomized rat, expression of mRNA for beta A subunit in liver was markedly increased 24 h after the partial hepatectomy. These results indicate that activin A inhibits initiation of DNA synthesis in hepatocytes by acting on its own receptor and that activin A acts as an autocrine inhibitor of DNA synthesis in rat hepatocytes.  相似文献   
96.
97.
This paper describes the priority of propagation among three parallel cracks. The treated object is an infinite elastic body with three parallel cracks subjected to uniform tension or antiplane shear at infinity. The results make it clear that the longest crack does not always have the biggest value relating to fracture, e.g. the biggest tangential stress at crack tip or the biggest stress intensity factor, because of the interaction among the cracks.  相似文献   
98.
Determination of the cell proliferation activity of neoplasm is useful in making a prognosis. Immunohistochemical detection using MIB-1 monoclonal antibody has recently allowed us to assess tumor cell proliferation easily, because it can be performed on paraffin-embedded specimens and the results have been demonstrated to be positively correlated with the results of PCNA staining. In this study, surgical specimens of 63 pituitary adenomas were examined by immunohistochemical staining with MIB-1 monoclonal antibody. Twenty-nine cases were non-functioning pituitary adenomas, 20 were prolactin (PRL)-producing pituitary adenomas, and 14 were growth hormone (GH)-producing pituitary adenomas. The MIB-1 positive rates of the pituitary adenomas ranged from 0% to 6.46%. In the non-functioning pituitary adenomas, the MIB-1 positive rates ranged from 0% to 4.55% (mean : 0.76%), in the PRL-producing pituitary adenomas the MIB-1 positive rates ranged 0% to 6.46% (mean : 0.91%), and in the GH-producing pituitary adenomas the MIB-1 positive rates ranged 0% to 1.28% (mean: 0.58%). There were no significant differences between these values according to the results of the Wilcoxon signed-rank test. Although the size of the non-functioning pituitary adenomas was not correlated with their MIB-1 positive rate, tumor size was closely correlated with the interval between the onset of the initial symptoms and the date of surgery. In the PRL-producing pituitary adenomas, the MIB-1 positive rate was not correlated with serum PRL levels as an index of secretory activity, but was correlated with the PRL staining positive rate. Preoperative bromocriptine therapy proved effective in reducing tumor size and serum PRL levels, but had no effect on the MIB-1 positive rate. In the GH-producing pituitary adenomas, the MIB-1 positive rate was not correlated with serum GH levels as an index of secretory activity, but was closely correlated with the GH staining positive rate. All three groups included both invasive and noninvasive tumor types, but there were no close statistical correlations between the three tumor types.  相似文献   
99.
100.
A 64-year-old male consulted our hospital with a 6-day history of malaise, body temperature to 38 degrees C, anorexia, and light headedness. The chest radiograph showed consolidation in the left lower lung area. Chest CT and ultrasonography revealed left pleural fluid. The pleural fluid was exudative (yellowish in color, protein 3.0 g/dl, Rivalta reaction positive, adenosine deaminase 19.4 U/L), and had a total cell count of 4.7 x 10(6)/ml with 45% lymphocytes, 40% histiocytes, and 15% polymorphonuclear leukocytes. He had kept a budgerigar, but we could not isolate Chlamydia from the pleural fluid or the pet bird. Transbronchial lung biopsy from left S10 revealed an increase of mononuclear leukocytes within the interstitial spaces, and the alveolar spaces contained polymorphonuclear leukocytes, fibrin, and organized alveolar exudate. Bronchoalveolar lavage cellular constituents were 50% lymphocytes, 27% neutrophils, and 23% macrophages. Serologic studies demonstrated C. trachomatis specific IgM antibody titers at 1:20 in a serum sample and at 1:10 in pleural fluid. We report a case of community-acquired pneumonia caused by C. trachomatis diagnosed by serologic studies.  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-23

京公网安备 11010802026262号