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   1275篇
  免费   24篇
  国内免费   11篇
工业技术   1310篇
  2022年   5篇
  2021年   8篇
  2020年   4篇
  2019年   4篇
  2018年   5篇
  2017年   6篇
  2016年   18篇
  2015年   5篇
  2014年   14篇
  2013年   22篇
  2012年   20篇
  2011年   23篇
  2010年   15篇
  2009年   25篇
  2008年   21篇
  2007年   30篇
  2006年   27篇
  2005年   17篇
  2004年   26篇
  2003年   14篇
  2002年   36篇
  2001年   32篇
  2000年   30篇
  1999年   44篇
  1998年   244篇
  1997年   153篇
  1996年   107篇
  1995年   67篇
  1994年   48篇
  1993年   47篇
  1992年   18篇
  1991年   32篇
  1990年   23篇
  1989年   19篇
  1988年   21篇
  1987年   12篇
  1986年   14篇
  1985年   15篇
  1983年   4篇
  1981年   3篇
  1980年   2篇
  1979年   1篇
  1978年   1篇
  1977年   5篇
  1976年   14篇
  1975年   2篇
  1974年   1篇
  1971年   1篇
  1970年   2篇
  1967年   1篇
排序方式: 共有1310条查询结果,搜索用时 15 毫秒
1.
Attacks by adult stages of the soft tick Argas (Argas) neghmei (Acari: Argasidae) on inhabitants of the High Andean plateau of Argentina are reported. This is the first local report of this species, which was previously found in the north of Chile. Taxonomic differences between A. (A.) neghmei and other neotropical and exotic species of the genus are underlined. The status of the knowledge about the Argentine argasid fauna is briefly described.  相似文献   
2.
Frequency notched printed slot antenna with parasitic open-circuit stub   总被引:2,自引:0,他引:2  
Lui  W.J. Cheng  C.H. Zhu  H.B. 《Electronics letters》2005,41(20):1094-1095
A new frequency notched ultra-wideband microstrip slot antenna with a parasitic tuning stub is proposed. The antenna is similar in configuration to a conventional microstrip slot antenna; by introducing a parasitic open-circuit tuning stub, flexible frequency notched function is achieved. Several properties of the antenna, such as frequency notched function, antenna transfer function and gain, have been investigated. As is reported, the operation bandwidth of the antenna is 2.91-11.16 GHz, in which a frequency notched band of 5.10-5.85 GHz has been achieved. Furthermore, good ultra-wideband linear transmission performance over the entire operation frequency range has also been achieved.  相似文献   
3.
Amines such as dopamine, norepinephrine and epinephrine were analysed in the brain regions of O.mossambicus exposed to quinalphos, phenthoate and their combination for 96 hr. The three types of treatments significantly (P < 0.05) altered the amines level at various intervals in the brain regions.  相似文献   
4.
5.
The incidence of stress fractures is increasing among competitive and recreational athletes as well as among children and the elderly. By understanding the continuum of bone's response to stress and maintaining an appropriate index of suspicion, the health care provider can diagnose these injuries appropriately. An accurate history and examination is essential and will differentiate stress fractures from other stress reactions. The more common stress fractures are discussed.  相似文献   
6.
In multiple pregnancies, survival of remaining fetuses after premature death and delivery of one fetus is uncommon. We report a case of a triplet pregnancy that was reduced to twins at the 14th gestational week and then had preterm premature rupture of membranes and intrauterine fetal death of one twin at the 17th gestational week. To save the surviving fetus, delivery of the dead fetus and ligation of the umbilical cord at the cervical level were performed. We also performed McDonald cervical cerclage to keep the placenta of the dead fetus as well as that of the surviving one in the uterine cavity. After a series of aggressive procedures, including immediate administration of tocolytic agents, and antibiotic prophylaxis to prevent infection and preterm labor, the surviving fetus was delivered vaginally 73 days later due to intractable uterine contractions. After a 10-week hospital stay, the infant boy, weighing 2,500 g, was discharged without any sequelae. To our knowledge, this was the longest interval between deliveries in a triplet pregnancy reported in Taiwan. With adequate intensive management, a satisfactory outcome of the fetus and mother in such cases is possible.  相似文献   
7.
8.
A chimeric dopamine transporter (DAT) cDNA encoding mutant human DAT (hDAT) protein in which the intracellular carboxyl-terminal tail is replaced by that of the bovine dopamine transporter (bDAT) was constructed. The chimeric hDAT cDNA was expressed in COS-7 cells, and [3H]dopamine and [3H]MPP+ uptake and [3H]CFT binding capacities were assessed. Substrate transport and ligand binding of bDAT were reduced by 32-43% as a result of substitution of the carboxyl tail in hDAT, suggesting that the functional characteristics of bDAT arise from differences in the carboxyl tail between human and bovine DAT. Thus, it appears that the sequences encoded within the carboxyl terminal of DAT would be one of the important determinants for its functions.  相似文献   
9.
The purpose of this study was to evaluate the relationship between the number of yolk sacs and amnionicity in monochorionic twin pregnancies scanned early in the first trimester. We retrospectively reviewed images of all monochorionic twins scanned between 6 and 9.5 weeks' gestation and with pathologic or sonographic confirmation of chorionicity-amnionicity. Each film was reviewed for the number of yolk sacs present, as well as for the gestational age at which the amniotic membrane was first visualized. Twenty monochorionic-diamniotic pregnancies and two monochorionic-monoamniotic pregnancies met the criteria for inclusion in the study. In diamniotic pregnancies scanned at less than 8 weeks' gestation, only the yolk sacs were identified; none of the dividing amniotic membranes were detected. Two yolk sacs were identified in all but one case. In this case, although one yolk sac was seen at 6 weeks, follow-up scanning at 8 weeks revealed two yolk sacs. In each of the monochorionic-monoamniotic twin pregnancies, one yolk sac was seen at 9 weeks and a single amnion encircled both embryos. We conclude that the sonographic identification of two yolk scas in monochorionic twins enables us to make the diagnosis of diamniotic twins early in the first trimester, before the amniotic membrane can be imaged. The presence of one yolk sac should prompt a follow-up ultrasonogram to assign amnionicity definitively.  相似文献   
10.
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