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   20474篇
  免费   1104篇
  国内免费   186篇
耳鼻咽喉   292篇
儿科学   354篇
妇产科学   356篇
基础医学   2404篇
口腔科学   515篇
临床医学   1211篇
内科学   5410篇
皮肤病学   488篇
神经病学   1485篇
特种医学   659篇
外科学   3667篇
综合类   122篇
一般理论   1篇
预防医学   589篇
眼科学   206篇
药学   1224篇
中国医学   47篇
肿瘤学   2734篇
  2023年   153篇
  2022年   312篇
  2021年   524篇
  2020年   305篇
  2019年   388篇
  2018年   499篇
  2017年   402篇
  2016年   475篇
  2015年   518篇
  2014年   671篇
  2013年   773篇
  2012年   1190篇
  2011年   1283篇
  2010年   719篇
  2009年   608篇
  2008年   1102篇
  2007年   1228篇
  2006年   1243篇
  2005年   1263篇
  2004年   1183篇
  2003年   1140篇
  2002年   1027篇
  2001年   414篇
  2000年   403篇
  1999年   395篇
  1998年   272篇
  1997年   213篇
  1996年   200篇
  1995年   169篇
  1994年   133篇
  1993年   141篇
  1992年   236篇
  1991年   192篇
  1990年   223篇
  1989年   183篇
  1988年   177篇
  1987年   174篇
  1986年   140篇
  1985年   156篇
  1984年   121篇
  1983年   89篇
  1982年   56篇
  1981年   48篇
  1980年   54篇
  1979年   68篇
  1978年   52篇
  1977年   48篇
  1975年   41篇
  1974年   44篇
  1972年   39篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Extracellular single-unit activity was recorded from 21 median preoptic nucleus (MnPO) neurones, antidromically identified as projecting to the hypothalamic paraventricular nucleus (PVN), in urethane-anaesthetized male rats. Of these identified MnPO neurones, 14 displayed an excitatory response in neuronal excitability following electrical stimulation (5 Hz, 600 microA) of the A1 noradrenergic region of the ventrolateral medulla, while the remaining neurones were unresponsive. The excitatory response of MnPO neurones was blocked by microiontophoretically applied phentolamine, an alpha-adrenoceptor antagonist, but not by timolol, a beta-adrenoceptor antagonist. These results suggest that the A1 region acts to enhance the activity of MnPO neurones projecting to the PVN via an alpha-adrenoceptor mechanism.  相似文献   
32.
Clinical features such as types of diseases, sex ratio, age of onset, sites of initial involvement, the appearance of bulbar signs, and duration of illness were studied in 52 patients with motor neuron disease (MND) with a special reference to immunoglobulin in cerebrospinal fluid (CSF) and serum. Although MND has been thought to be a degenerative disease of unknown cause, our data suggested there are some immunological abnormalities in this disease. The duration of illness and the abnormalities of CSF immunoglobulins appeared to be correlated with the type of disease and the site of initial involvement. However, whether or not these abnormalities in CSF immunoglobulins are directly related to the pathogenesis of MND remains unclear.  相似文献   
33.
34.
The in vitro clonogenic assay has been used to assess the biological effects of estradiol-17 beta (E 2) and an antiestrogen, tamoxifen (TAM) on human breast cancer, and the results were compared with the estrogen receptor status (ER). The sera used were treated with dextran-coated charcoal to avoid the modification effects of the endogenous hormones. There was a significant difference between ER (+) and ER (-) breast cancers in the incidence of cases in which the plating efficiency of cancers increased more than 50% over those of untreated control by adding 10(-8) M of E 2 (40.2% vs. 21.3%). TAM, 10(-6) M revealed a less than 50% colony formation of the control in 30.5% of ER (+) cancers, whereas only 13.0% of ER (-) cancers showed a response to TAM.  相似文献   
35.
36.
The blocking effects of complement-dependent sperm immobilizingantibodies in the sera of infertile women and monoclonal antispermantibodies against humans and mice on fertilization were investigated.The hemizona assay (HZA) and sperm penetration assay (SPA) wereused to study the inhibitory effects of sera from 22 infertilepatients positive for sperm immobilizing antibodies. Use ofthese tests allowed us to differentiate whether the antibodyblocked sperm—zona pellucida tight binding and/or spermpenetration into the ooplasm. The zona pellucida penetrationassay (ZPA) was also used to study the effects of four monoclonalantibodies (mAbs) on human sperm penetration into the zona pellucida.Seven mAbs against murine spermatozoa were tested for theirinhibitory effects on in-vitro fertilization (IVF) and HZA inmice. Of 22 patient sera with sperm immobilizing antibodies,21 (95.5%) inhibited HZA attachment and penetration, whereasthis did not occur in any of 13 patient sera without these antibodies.However, 19 of 22 (86.4%) patient sera with sperm immobilizingantibodies and eight of 13 (61.5%) patient sera without theseantibodies inhibited the SPA. Two (2C6, 1G12) of four mAbs againsthuman spermatozoa showed strong inhibitory effects in all theassays (HZA, ZPA and SPA). One mAb (3B10) did not inhibit HZAbut blocked ZPA and SPA. Another mAb (H6-3C4) seemed to haveno inhibitory effects on fertilization. Two (Vx 5 and Vx 8)of seven mAbs against murine spermatozoa inhibited IVF in micebut did not block mouse HZA. These findings suggest that antispermantibodies block fertilization at specific stages. Some of themmay inhibit sperm capacitation and thus prevent all processesof fertilization that follow. Some other antibodies may notaffect capacitation and sperm binding to zona pellucida butinhibit the acrosome reaction, followed by the blocking of spermpenetration through zona pellucida and ooplasm.  相似文献   
37.
38.
BACKGROUND: Indoor formaldehyde (FA) might worsen allergies and be an underlying factor for the increasing incidence and severity of asthma; the exact mechanism, however, remains unclear. OBJECTIVE: The present study examined the effects of repeated exposure to FA on methacholine- and antigen-induced bronchoconstriction in guinea-pigs in vivo. METHODS: First, non-sensitized guinea-pigs were transnasally treated with 0.1 or 1.0% FA or saline three times a week for 6 weeks, and increasing concentrations of methacholine (50, 100, and 200 microg/mL) were inhaled at 5-min intervals. Second, guinea-pigs pre-treated with transnasal administration of FA or saline using the same protocol were passively sensitized with anti-ovalbumin (OA) serum 7 days before antigen challenge. Third, guinea-pigs were actively sensitized with OA and pre-treated with transnasal administration of FA or saline using the same protocol. The lateral pressure of the tracheal tube (Pao) was measured under anesthesia and artificial ventilation. RESULTS: The antigen-induced increase in Pao in actively sensitized guinea-pigs was significantly potentiated by FA exposure in a dose-dependent manner. The dose-response curve of the methacholine-induced increase in Pao in non-sensitized guinea-pigs or of the antigen-induced increase in Pao in passively sensitized guinea-pigs was not altered by FA exposure. Transnasal administration of FA significantly increased the serum anti-OA homocytotropic antibody titre (IgG) as measured by the passive cutaneous anaphylaxis reaction in actively sensitized guinea-pigs. CONCLUSION: The results suggest that repeated exposure to FA worsens allergic bronchoconstriction through enhancing antigen sensitization.  相似文献   
39.
In vitro reaction to Candida allergen was studied in 100 normal healthy Japanese and related to HLA. A significant association was found between the low responder group (< 7,000 c.p.m.) and HLA-B15 and the high responder group (> 7,000 c.p.m.) and HLA-B7, as well as Dwl. Four HLA-D homozygote cells of types HLA-Dwl and DHO, were tested; these fitted in the high responder group. HLA-DYT and DEn fitted into the low responder group. Responsiveness to Candida allergen corresponded to skin test (r = 0.884, P < 0.01). From these results, in vitro lymphocyte reaction to Candida allergen and skin tests showed close correlation and an association with HLA antigens, HLA-D in particular.  相似文献   
40.
We report here that loss of the Sprouty2 gene (also known as Spry2) in mice resulted in enteric nerve hyperplasia, which led to esophageal achalasia and intestinal pseudo-obstruction. Glial cell line-derived neurotrophic factor (GDNF) induced hyperactivation of ERK and Akt in enteric nerve cells. Anti-GDNF antibody administration corrected nerve hyperplasia in Sprouty2-deficient mice. We show Sprouty2 to be a negative regulator of GDNF for the neonatal development or survival of enteric nerve cells.  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