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   562篇
  免费   25篇
  国内免费   1篇
  2023年   1篇
  2022年   5篇
  2021年   6篇
  2020年   5篇
  2019年   4篇
  2018年   9篇
  2017年   9篇
  2016年   14篇
  2015年   28篇
  2014年   26篇
  2013年   39篇
  2012年   41篇
  2011年   28篇
  2010年   24篇
  2009年   12篇
  2008年   43篇
  2007年   30篇
  2006年   31篇
  2005年   32篇
  2004年   21篇
  2003年   34篇
  2002年   35篇
  2001年   7篇
  2000年   8篇
  1999年   12篇
  1998年   8篇
  1997年   3篇
  1996年   3篇
  1995年   3篇
  1994年   5篇
  1993年   5篇
  1992年   10篇
  1991年   8篇
  1990年   6篇
  1989年   13篇
  1988年   6篇
  1987年   2篇
  1986年   2篇
  1985年   2篇
  1984年   3篇
  1983年   3篇
  1979年   1篇
  1959年   1篇
排序方式: 共有588条查询结果,搜索用时 31 毫秒
1.
Inhibin activity in goat seminal plasma was measured by in vitro assay throughout successive 9 months and its relationship with the serum FSH, LH and testosterone concentrations was investigated. Total inhibin activity (TIA) in seminal plasma gradually increased from spring to summer, reduced in autumn (P<0.05) and recovered toward winter (P<0.05). Serum FSH and LH reached a peak in mid-summer (P<0.01) and returned to the low levels in autumn. Serum testosterone also increased in mid-summer and kept the high levels until the early winter (P<0.05). Some positive correlation was found in monthly levels between seminal TIA and serum FSH (r=0.305; P<0.05). Results suggest that the summer increase of inhibin activity in seminal plasma relates with the mid-summer rise of serum FSH levels in the male goat.  相似文献   
2.
We investigated light and electron microscopic localization of ornithine transcarbamylase (OTC) in rat intestinal mucosa. In the immunoblotting assay of OTC-related protein, a single protein band with a molecular weight of about 36,500 is observed in extracts of liver and small intestinal mucosa but is not observed in those of stomach and large intestine. For light microscopy, tissue slices of the digestive system were embedded in Epon and stained by using anti-bovine OTC rabbit IgG and the immunoenzyme technique. For electron microscopy, slices of these and the liver tissues were embedded in Lowicryl K4M and stained by the protein A-gold technique. By light microscopy, the absorptive epithelial cells of duodenum, jejunum, and ileum stained positively for OTC, but stomach, large intestine, rectum, and propria mucosa of small intestine were not stained. Electron microscopy showed that gold particles representing the antigenic sites for OTC were confined to the mitochondrial matrix of hepatocytes and small intestinal epithelial cells. However, the enzyme was detected in mitochondria of neither liver endothelial cells, submucosal cells of small intestine, nor large intestinal epithelial cells. Labeling density of mitochondria in the absorptive epithelial cells of duodenum, jejunum, and ileum was about half of that in liver cells.  相似文献   
3.
To elucidate a possible role of tyrosine supply as a factor modulating catecholamine biosynthesis in the adrenergic cell, the transport of [14C]tyrosine into cultured bovine adrenal chromaffin cells was first examined, and the relationship between [14C]tyrosine transport and [14C]catecholamine formation was then investigated. Under the conditions which were routinely employed to determine the rate of catecholamine biosynthesis, tyrosine was taken up into the cells in a manner independent of extracellular Na+ and Ca2+, and this uptake was also insensitive to ouabain and various metabolic inhibitors. The stimulation of these cells with high K+ and other secretagogues caused no significant alteration in the uptake. While, tyrosine transport was markedly inhibited by tyrosine analogues and other L-aromatic amino acids, and this inhibition was accompanied by the reduction of [14C]catecholamine formation. In contrast, tyrosine transport was markedly enhanced by flavone, and this enhancement was also accompanied by the augmentation of catecholamine production under the same experimental conditions. These results seem to indicate that the transport of tyrosine into the cells may be closely related to catecholamine formation within the cells, thus providing an evidence for a possible role of tyrosine supply as one of the factors affecting catecholamine production in the adrenal chromaffin cell.  相似文献   
4.
Summary We have developed a bioreactor system for aerobic fermentation, using a new ceramic carrier APHROCELL which has a suitable shape for liquid and gas passage. In acetic acid fermentation byAcetobacter cells from ethanol, as a typical example of aerobic fermentation, a productivity of 17.25 g/l h was attained at continuous production of 23 g-acetic acid/l; at an acetic acid concentration around 53 g/l, the productivity was 6.4 g/l h. Thus a marketable vinegar can be obtained continuously by this bioreactor system. Because of the simplicity of the APHROCELL reactor, scale up should be relatively easy.  相似文献   
5.
H Narita  M Hamano  F Cho 《Jikken dobutsu》1988,37(4):393-397
This paper describes usefulness of the ultrasonographical device (USD) for the diagnosis of pregnancy and the observation of fetal growth in the squirrel monkeys (Saimiri sciureus) conceived under group breeding conditions. Pregnancy was diagnosed on the basis of the detection of gestational sac (GS) in the uterus. The GS was first detected 127 +/- 10 days before delivery. The heart beat of embryo was detected around 114 days before delivery. It was able to judge conditions of fetal growth by measuring the size of GS and the biparietal diameter. No difference in uterine size between nonpregnant and pregnant animals was observed 135 days before delivery.  相似文献   
6.
7.
Summary In order to examine its clinical efficacy, recombinant human interferon- (rIFN-) was instilled intravesically into 51 patients with superficial bladder cancer. Ten patients, who received intermittent intravesical instillation at a dose of (3–36) × 106 U rIFN- on days 1–3 every week, showed no response. Thirty-two patients received intravesical instillation at a dose of (3–36) × 106 U every day for 10–20 days. Eight patients showed partial response, indicating an efficacy rate of 25%. Nine patients received divided doses of 18 × 106 U twice a day every day for 10–20 days. Six patients showed partial response, indicating an efficacy rate of 67%. This value was significantly higher than that obtained by administering divided doses. The response to intravesical instillation therapy with rIFN- varies with treatment protocol. Frequent and longer exposure to rIFN- may induce better regression of superficial bladder cancer. Six incidences of side-effects were found in five cases (9.8%): pollakiuria in one, pain on micturition in two, fever in two, and eruption in one case. All of these side-effects were slight and reversible after drug withdrawal. Laboratory tests showed only a few changes with low severity. Thus, rIFN- is potentially a new drug for instillation therapy of superficial bladder cancer, in view of the absence of adverse effects.  相似文献   
8.
The long-term changes in the frequencies ofPythium iwayamai andP. paddicum in upland- and flooded paddy-field soils were compared. The frequencies of both species fell in both soils within the first 6 months after they had been buried. After 36 and 48 months,P. iwayamai showed higher frequency thanP. Paddicum in upland-field soil, whileP. paddicum showed higher frequency thanP. iwayamai in paddy-field soil. These findings indicate respectively higher colonization ability to organic matters ofP. iwayamai in upland-field soil andP. paddicum in paddy-field soil.This study was partly supported by a Grant-in-Aid (no. 63560048) from the Ministry of Education, Science and Culture, Japan.  相似文献   
9.
We have studied receptor-mediated calcium signals in antigen-specific B cells (trinitrophenol-specific B cell clone, TP67.21) using a confocal fluorescence microscope with an argon ion laser (488 nm) and a He-Cd laser (325 nm). Confocal fluorescence images of fluo-3 loaded B cells, excited by an argon ion laser, became much brighter and more nonhomogeneous than those before antigen stimulation. Time-dependent fluorescence changes in intensities were abrupt and quite similar to the patterns of the intracellular calcium ion concentration [Ca2+]i observed by a conventional fluorescence microscope using fura-2. From the morphological patterns of the calcium images, the parts of the bright fluorescence seemed to belong to the nucleus in B cells. To confirm the above events we measured the confocal fluorescence images of the nucleus. From the fluorescence images of co-loaded Hoechst 33342 (a DNA-specific fluorescent probe), which excited by a He-Cd laser, the brighter parts of the fluo-3 fluorescence intensities were identified to the nucleus in B cells. This suggested the possibility that the increased intranuclear calcium ions may play a nuclear third messenger in B cells.  相似文献   
10.
Leptocephalus eel larvae will feed in aquaria   总被引:1,自引:0,他引:1  
Synopsis Premetamorphosing larvae of Muraenesox cinereus (Muraenesocidae) and Conger myriaster (Congridae), caught and kept alive in aquaria, repeatedly bit pieces out of a lump of squid paste. By coloring the paste with Brilliant Red, ingestion and defecation were clearly seen through the transparent gut. The paste is not their natural food, but nevertheless a possible food item for rearing eels from eggs; most previous efforts have failed inasmuch as the larvae have starved.  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