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91.
Induction of diabetes by Streptozotocin in rats 总被引:1,自引:0,他引:1
A. Akbarzadeh D. Norouzian M. R. Mehrabi Sh. Jamshidi A. Farhangi A. Allah Verdi S. M. A. Mofidian B. Lame Rad 《Indian journal of clinical biochemistry : IJCB》2007,22(2):60-64
The objective of this study is to induce experimental diabetes mellitus by Streptozotocin in normal adult Wistar rats via
comparison of changes in body weight, consumption of food and water, volume of urine and levels of glucose, insulin and C-peptide
in serum, between normal and diabetic rats. Intra-venous injection of 60mg/kg dose of Streptozotocin in adult wistar rats,
makes pancreas swell and at last causes degeneration in Langerhans islet beta cells and induces experimental diabetes mellitus
in the 2–4 days. Induction of experimental diabetes mellitus is indeed the first step in the plan of purification of pancreatic
Langerhans islet cells of normal rats for transplanting under the testis subcutaneous of experimentally induced diabetic rats.
Streptozotocin induces one type of diabetes which is similar to diabetes mellitus with non-ketosis hyperglycemia in some animal
species. For induction of experimental diabetes in male adult rats weighted 250–300 grams (75–90 days), 60mg/kg of Streptozotocin
was injected intravenously. Three days after degeneration of beta cells, diabetes was induced in all animals. The diabetic
and normal animals were kept in the metabolic cages separately and their body weight, consumption of food and water, urine
volume, the levels of serum glucose, insulin and C-peptide quantities in all animals were measured and then these quantities
were compared. For a microscopic study of degeneration of Langerhans islet beta cells of diabetic rats, sampling from pancreas
tissue of diabetic and normal rats, staining and comparison between them, were done. Induction of diabetes with Streptozotocin
decreases Nicotinamide-adenine dinucleotide (NAD) in pancreas islet beta cells and causes histopathological effects in beta
cells which probably intermediates induction of diabetes. In this study, we used Streptozotocin for our experiments in induction
of experimental diabetes mellitus. After Induction of diabetes, consumption of food and water, volume of urine and glucose
increased in the diabetic animals in comparison with normal animals, but the weight of body and the volume of insulin and
C-peptide decreased in the diabetic animals. Sampling and staining of pancreas tissue of diabetic and normal rats showed that
the Langerhans islet beta cells of diabetic rats have been clearly degenerated. In three days, Streptozotocin makes pancreas
swell and at last causes degeneration in Langerhans islet beta cells and induces experimental diabetes. It also changes normal
metabolism in diabetic rats in comparison with normal rats. Consumption of water and food, volume of urine, serum glucose
increases in diabetic animals in comparison with normal rats but the levels of serum insulin, C-peptide and body weight decreases. 相似文献
92.
In this paper, we consider theories about processes of visual perception and perception-based knowledge representation (VPR)
in order to explain difficulties encountered in figural processing in junior high school geometry tasks. In order to analyze
such difficulties, we take advantage of the following perspectives of VPR: (1) Perceptual organization: Gestalt principles,
(2) recognition: bottom-up and top-down processing; and (3) representation of perception-based knowledge: verbal vs. pictorial
representation, mental images and hierarchical structure of images. Examples given in the paper were mostly taken from Gal's
study (2005) which aimed at identifying and analyzing Problematic Learning Situations (after Gal & Linchevski, 2000) in junior high school geometry classes. Gal's study (2005) suggests that while this theoretical perspective became part of teachers' pedagogic content knowledge, the teachers were
aware of their students' thinking processes and their ability to analyze and cope with their students’ difficulties in geometry
was improved. 相似文献
93.
Soumela Atmatzidou Stavros Demetriadis Panagiota Nika 《Journal of Science Education and Technology》2018,27(1):70-85
Educational robotics (ER) is an innovative learning tool that offers students opportunities to develop higher-order thinking skills. This study investigates the development of students’ metacognitive (MC) and problem-solving (PS) skills in the context of ER activities, implementing different modes of guidance in two student groups (11–12 years old, N1 = 30, and 15-16 years old, N2 = 22). The students of each age group were involved in an 18-h group-based activity after being randomly distributed in two conditions: “minimal” (with minimal MC and PS guidance) and “strong” (with strong MC and PS guidance). Evaluations were based on the Metacognitive Awareness Inventory measuring students’ metacognitive awareness and on a think-aloud protocol asking students to describe the process they would follow to solve a certain robot-programming task. The results suggest that (a) strong guidance in solving problems can have a positive impact on students’ MC and PS skills and (b) students reach eventually the same level of MC and PS skills development independently of their age and gender. 相似文献
94.
Mansoor Niaz 《Interchange》2004,35(2):155-184
The objective of this study is to provide in-service teachers an opportunity to become familiar with the controversial nature
of progress in science (growth of knowledge) and its implications for research methodology in education. The study is based
on 41 participants who had registered for a nine-week course on Methodology of Investigation in Education, as part of their
Master’s degree program. The course is based on 20 readings drawing upon a history and philosophy of science perspective (positivism,
constructivism, Popper, Kuhn, Lakatos) and its implications for educational research. Course activities included written reports,
class room discussions based on participants’ presentations, and written exams. Based on the results obtained it was concluded
that: (a) participants were able to understand the basic ideas of constructivist philosophy and its pedagogical implications;
(b) the role of behavioural objectives in actual educational practice was questioned; (c) integration of qualitative and quantitative
research methods was considered to be an alternative to the current debate about the replacement of one method by the other;
(d) participants considered the dilemma of evaluating students based on what they have learned or what they should have learned,
within the social constructivist framework and generally favoured the former; and (e) most of the participants were reluctant
to accept constructivism as a form of positivism, a controversial thesis that is gaining support in the research literature.
Given the importance of alternative approaches to growth and meaning of knowledge, it is important that teachers be aware
of conflicting situations in the classroom that refer to: objectivity, scientific method, qualitative-quantitative methods,
relationship between method and problem, evaluation, and a critical appreciation of constructivism. 相似文献
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