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   214019篇
  免费   13708篇
  国内免费   1250篇
耳鼻咽喉   2336篇
儿科学   6409篇
妇产科学   4303篇
基础医学   28591篇
口腔科学   4267篇
临床医学   19513篇
内科学   45920篇
皮肤病学   3406篇
神经病学   20347篇
特种医学   7372篇
外国民族医学   24篇
外科学   30502篇
综合类   3284篇
现状与发展   1篇
一般理论   200篇
预防医学   15978篇
眼科学   4766篇
药学   16164篇
  4篇
中国医学   782篇
肿瘤学   14808篇
  2023年   979篇
  2022年   1973篇
  2021年   3997篇
  2020年   2477篇
  2019年   3908篇
  2018年   4697篇
  2017年   3497篇
  2016年   3882篇
  2015年   4507篇
  2014年   6264篇
  2013年   8984篇
  2012年   12972篇
  2011年   13764篇
  2010年   8064篇
  2009年   7320篇
  2008年   12180篇
  2007年   12880篇
  2006年   12208篇
  2005年   12085篇
  2004年   11973篇
  2003年   11257篇
  2002年   11068篇
  2001年   4860篇
  2000年   4516篇
  1999年   4147篇
  1998年   2545篇
  1997年   2076篇
  1996年   1737篇
  1995年   1699篇
  1994年   1468篇
  1993年   1439篇
  1992年   2426篇
  1991年   2343篇
  1990年   2017篇
  1989年   1929篇
  1988年   1813篇
  1987年   1653篇
  1986年   1577篇
  1985年   1524篇
  1984年   1315篇
  1983年   1210篇
  1982年   1135篇
  1981年   988篇
  1980年   880篇
  1979年   931篇
  1978年   760篇
  1977年   713篇
  1975年   697篇
  1974年   756篇
  1973年   719篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
1 The present study examined the role of muscarinic receptors in the modulation of noradrenaline (NA) release in the guinea-pig isolated distal colon. The spontaneous endogenous NA overflow assayed by HPLC-ED was taken as an index of NA release from enteric noradrenergic nerve terminals. 2 Physostigmine (10 μm ) significantly enhanced spontaneous endogenous NA overflow. Hyoscine (muscarinic antagonist), (R)-(-)-trihexyphenidyl and telenzepine (M1-selective antagonists), and 11[[2-[(diethylamino)methyl]-1-piperydil]acetyl]-5,11-dihydro-6H-pyrido[2,3-b][1,4]benzodiazepine-6-one (AF-DX 116, M2-selective antagonist) inhibited NA overflow in a concentration dependent manner, with the following EC50 values: 131.74 (18.19–953.96), 101.62 (58.83–175.60), 150 (60–330), 30 (5–170) nm , respectively. 4-diphenylacetoxy-N-methylpiperidine methiodide (4-DAMP, M1- and M3- selective antagonist) had no significant effect up to 100 μm . 3 The muscarinic agonist oxotremorine inhibited NA overflow in a concentration dependent manner, with an EC50 value of 0.67 (0.30–1.51) μm . The response to oxotremorine was inhibited by muscarinic antagonists with the following order of potency: hyoscine = (R)-(-)-trihexyphenidyl = telenzepine > 4-DAMP >> AF-DX 116. 4 In the presence of 3 μm tetrodotoxin (TTX), the effect of oxotremorine and 4-DAMP was unchanged, while hyoscine, (R)-(-)-trihexyphenidyl, telenzepine and AF-DX 116, instead of inhibiting, significantly enhanced NA overflow. 5 The present results indicate that, in the guinea-pig colon, endogenous acetylcholine sustains spontaneous NA release by activating muscarinic receptors possibly located on interneurones. In addition, inhibitory muscarinic receptors may exist on adrenergic terminals.  相似文献   
72.
73.
This study examined the relations betweensociotropy, autonomy, and stress severity ratings forhypothetical life events that were objectivelycategorized as interpersonal or achievement-related infocus. The hypothesis that sociotropy and autonomyserve as vulnerability factors to dysphoria in thepresence of life stress that matches the theme of thevulnerability was also examined in 6-week and 12-week follow-up evaluations. Results provided onlypartial support for the predicted relations amongsociotropy, autonomy, and perceived stress severityratings of interpersonal and achievement-related events. Longitudinal results failed to support thehypothesis that sociotropy and autonomy serve asvulnerability factors for matching interpersonal andachievement-related stress. It was concluded thatobjectively categorizing life events as interpersonal orachievement-related is problematic given that themeaning of life events can vary across individuals, andthat these meanings are likely to vary partly as a function of sociotropy and autonomy.  相似文献   
74.
We report the results of administration of danazol after suspension of gonadotrophin-releasing hormone analogue (GnRHa) therapy for uterine myomas. A total of 21 women with uterine myomas was treated with 100 mg danazol for 6 months after GnRHa therapy. Uterine volume and endocrine status were monitored monthly by ultrasound and assay of plasma gonadotrophins, oestradiol and progesterone. The results show a rebound of uterine volume about 30% less than in controls at the end of danazol therapy. Menstrual cyclicity returned after 65 +/- 3 days in 16 subjects and five patients remained amenorrhoeic. Hormone assays confirmed renewed ovarian function in the women whose menstrual periods returned. Bone mineral content was substantially reduced during GnRHa treatment but improved significantly during danazol therapy even in the women who remained amenorrhoeic. These results show the utility of danazol in prolonging the therapeutic effects of GnRHa. The mechanism by which danazol inhibits rebound of uterine volume may be due to its antiprogesterone effects on uterine myomas.   相似文献   
75.
A monoclonal antibody raised by immunization of BALB/c mice with erythrocytic stages of Plasmodium vivax was shown to react with asexual erythrocytic stages of P. chabaudi. The cross-reactivity molecules are antigens of 200 and 148 kDa in P. vivax and of 190 and 70 kDa in P. chabaudi. Immunofluorescence studies of the erythrocytic stages of P. vivax and P. chabaudi indicated that expression of these antigens increased as the parasites' developed from the ring stage to the schizont stage. In the mature trophozoites of P. chabaudi, immunoelectron microscopy revealed clusters of antigen distributed in the cytoplasm of the parasitized erythrocyte. In the schizont, packets of antigen were found associated with the parasitophorous vacuole and the cytoplasm of the infected host cell. Received: 19 March 1996 / Accepted: 28 August 1996  相似文献   
76.
We describe a novel human zinc finger cNDA, C2H2-171. This cDNA represents an mRNA which encodes a protein of 484 amino acids and a calculated molecular weight of 54 kD. Four zinc finger-like domains are found in the C-terminal end of the protein. At the N-terminus, C2H2-171 contains a POZ/tramtrack-like domain similar to that found in the tumor associated zinc finger proteins LAZ-3/BCL-6 and PLZ-F, as well as in non-zinc finger proteins. C2H2-171 RNA is preferentially expressed in the brain, and increases during the course of murine development, with maximal expression in the adult. C2H2-171 RNA is differentially expressed in brain regions, with the highest level of expression in the cerebellum. C2H2-171 RNA was expressed at high levels in primary cerebellar granule cell neurons compared to astrocytes. The gene encoding C2H2-171 is highly conserved in vertebrates, and maps to the terminus of human chromosome 1 (1q44-ter). This chromosomal location is associated with a number of cytogenetic aberrations including those involving brain developmental anomalies and tumorigenesis. These data suggest that C2H2-171 may play an important role in vertebrate brain development and function.  相似文献   
77.
78.
The authors systematically evaluated the frequency patterns of cocaine use in 85 cocaine-dependent outpatients and found four patterns of use: continuous (27%), intermittent patterned (35%), intermittent nonpatterned (25%), and occasional (13%). Few subjects reported consistent cycling between binges and crashes. There were no significant differences in patterns of use associated with gender, race, educational level, route of administration, or recency of heroin use. Continuous users and occasional users were older than intermittent users. Because different contingencies may control patterned vs. nonpatterned cocaine use, pattern of use may have implications for treatment, even in individuals reporting similar amounts of cocaine use.  相似文献   
79.
Although a great deal is known about the nature and severity of the recent financial crisis in agriculture, there has been little systematic study of the social and psychological effects of this crisis upon farm operators and their families. Using data from a statewide sample of Iowa farmers, this study tests some hypotheses about correlates of psychological stress. The findings suggest that many farm operators find their situations to be stressful and that such stress is related to the severity of their financial problems. In addition, the life-events perspective is examined in its utility to explain how adverse economic changes impact psychological well-being.  相似文献   
80.
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