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   12207篇
  免费   740篇
  国内免费   7篇
  12954篇
  2023年   106篇
  2022年   114篇
  2021年   224篇
  2020年   204篇
  2019年   208篇
  2018年   420篇
  2017年   379篇
  2016年   511篇
  2015年   760篇
  2014年   758篇
  2013年   915篇
  2012年   1096篇
  2011年   947篇
  2010年   618篇
  2009年   419篇
  2008年   740篇
  2007年   662篇
  2006年   611篇
  2005年   529篇
  2004年   459篇
  2003年   412篇
  2002年   385篇
  2001年   175篇
  2000年   159篇
  1999年   113篇
  1998年   84篇
  1997年   42篇
  1996年   60篇
  1995年   58篇
  1994年   33篇
  1993年   42篇
  1992年   74篇
  1991年   59篇
  1990年   53篇
  1989年   38篇
  1988年   41篇
  1987年   41篇
  1986年   29篇
  1985年   50篇
  1984年   38篇
  1983年   19篇
  1982年   24篇
  1981年   23篇
  1980年   22篇
  1979年   22篇
  1978年   22篇
  1977年   22篇
  1975年   16篇
  1974年   15篇
  1973年   15篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Summary Four siblings with the autosomal recessive Roberts syndrome are reported, and we discuss the phenotypic overlap of this syndrome with other similar radial, aplasia syndromes.  相似文献   
62.
A quantitative in situ assay of yeast α-glucosidase involving permeabilization of the cells by freezing and thawing is described. The assay was applied to different strains in different physiological states and was shown to give results comparable to those obtained with total cell homogenates. The primary advantage of the in situ assay was the possibility of analyzing a large number of samples from the same culture during a growth curve using a very reduced cell mass.  相似文献   
63.
Summary Two 46,XY brothers were found to have a previously undescribed syndrome characterized by severe mental deficiency, proportionate dwarfism, and delayed sexual development. A recessive mode of inheritance, either autosomal or X-linked, is assumed.  相似文献   
64.
Tethered walking imagines of the mealworm beetle Tenebrio molitor wave their heads in random fashion. If a periodic pattern of vertical black and white stripes is rotated around the animal a regular nystagmic head movement is superimposed upon the random waving, the frequency of the latter equals the contrast frequency within large ranges of the angular velocity of the pattern. The nystagmus is inverted: After a short period of tracking, during which the angular velocity of the head is the same as that of the panorama, the head returns slowly toward its normal position according to an exponential-like function. Resting animals do not wave their heads. However, if the above panorama is rotated, the beetle turns its head in the direction of the movement of the panorama and holds it in a side-way position, as long as the rotation is maintained. The angular position reached depends in the same manner on the angular velocity of the panorama as the turning tendency of walking animals established in open loop experiments using the spherical Y-maze method.  相似文献   
65.
66.
Ammonia overloading was investigated during glucose and fructose metabolism in isolated hepatocytes under a variety of metabolic conditions. In all assay conditions, the glycolytic flux and oxygen uptake was not modified by 10 mM ammonia. In hepatocytes isolated from rats fed as libitum, the presence of ammonia caused a decrease in the production of lactate (pyruvate); this effect was not observed in anaerobic incubations, in hepatocytes isolated from starved animals, or in fetal hepatocytes. In spite of an overproduction of urea, ammonia detoxification also takes place by the synthesis of alanine, glutamate and aspartate. Addition of 1 mM aminooxyacetate, an inhibitor of aminotransferases, to the incubation medium prevents the formation of these amino acids, and also prevents the decrease of lactate in hepatocytes isolated from fed animals.  相似文献   
67.
A controlled cross betweenCannabis sativa L. andC. ruderalis Janisch. gave progeny intermediate in both cannabinoid content and morphology. The progeny fell into two distinct populations, those whose tetrahydrocannabinol (THC) content was closer to theC. sativa parent (greater than 60% of total cannabinoids) and those whose THC content was closer to theC. ruderalis parent (less than 40% of total cannabinoids). The lower THC group was twice as frequent as the other group. Earliness of flowering, number of flowers, and height characteristics were intermediate between the parents.  相似文献   
68.
69.
Three affected siblings with the hermaphrodism are described. The propositi showed the following characteristics: male phenotype and gender role, hypospadias, bilateral scrotal ovotestes with palpable nodules, and absence of müllerian structures. The X chromatin was positive and the Y chromatin was negative in the 3 affected subjects. Their karyotype in peripheral blood lymphocytes and in gonadal fibroblasts was 46,XX and no Y chromosome fluorescence was observed. Plasma FSH was elevated in the 2 older patients and plasma LH was elevated only in the oldest. Plasma testosterone was low and plasma estradiol high in the 3 siblings; plasma progesterone was elevated in 2, but normal in 1 sibling. Since some of the clinical characteristics of these 3 affected siblings are not the most common features in the majority of sporadic cases of true hermaphrodism, it is suggested that the presence of all of them may be the first clue for the clinical suspicion of the familial type of true hermaphrodism.  相似文献   
70.
Since the regulation of the vascular permeability in the CNS is dependent partly on the enzymes associated with the wall of brain capillaries, the histochemical demonstration of these enzymes may furnish further data on the function of the blood brain barrier (BBB), a new methodological approach, using brain smears was developed for the histochemical demonstration of several enzymes participating in the function of the BBB. The method presented renders possible also the subsequent demonstration of monoamines and the activity of different enzymes in the same tissue preparation. The usefulness of this simple technique in the study of brain capillary functions is discussed.  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