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   1107974篇
  免费   82670篇
  国内免费   2710篇
耳鼻咽喉   14871篇
儿科学   38296篇
妇产科学   31128篇
基础医学   162269篇
口腔科学   31568篇
临床医学   99674篇
内科学   213400篇
皮肤病学   26347篇
神经病学   90600篇
特种医学   43268篇
外国民族医学   305篇
外科学   166126篇
综合类   24218篇
一般理论   418篇
预防医学   84083篇
眼科学   25045篇
药学   79811篇
  3篇
中国医学   2207篇
肿瘤学   59717篇
  2019年   8487篇
  2018年   13043篇
  2017年   10321篇
  2016年   12095篇
  2015年   12899篇
  2014年   16978篇
  2013年   26633篇
  2012年   34893篇
  2011年   37565篇
  2010年   22250篇
  2009年   19931篇
  2008年   35574篇
  2007年   37633篇
  2006年   37835篇
  2005年   36400篇
  2004年   35294篇
  2003年   34197篇
  2002年   33103篇
  2001年   50681篇
  2000年   52787篇
  1999年   42938篇
  1998年   12336篇
  1997年   11019篇
  1996年   10910篇
  1995年   10398篇
  1994年   9687篇
  1993年   9029篇
  1992年   32802篇
  1991年   31942篇
  1990年   31470篇
  1989年   30355篇
  1988年   27575篇
  1987年   27796篇
  1986年   25807篇
  1985年   25152篇
  1984年   18919篇
  1983年   15973篇
  1982年   9783篇
  1981年   8846篇
  1979年   17250篇
  1978年   12582篇
  1977年   10726篇
  1976年   10106篇
  1975年   10530篇
  1974年   12655篇
  1973年   12136篇
  1972年   11110篇
  1971年   10371篇
  1970年   9598篇
  1969年   8925篇
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
991.
Zusammenfassung Die posttraumatische Pneumatocele ist eine seltene intrapulmonale Veränderung nach stumpfem Thoraxtrauma. Anhand eines gut dokumentierten Falles wird diese seltene Form der Lungenkontusion dargestellt und die klinisch bedeutsame Differentialdiagnose diskutiert.
Traumatic pneumatocele — a case report
Summary The posttraumatic pneumatocele is a rare intrapulmonary lesion following blunt thoracic injury. By means of a well documented case report this rare form of lung contusion is demonstrated and the clinically important differential diagnosis is discussed.
  相似文献   
992.
The return of fertility following discontinuation of norethisterone oenanthate (NET EN) 200 mg injectable contraceptive after use for a minimum period of six months or more was studied in 69 women who discontinued the method for planning pregnancy. Former users of copper intra-uterine device (CuT 200) were enrolled as a control group. Another 161 women who had discontinued NET EN due to other reasons (e.g. amenorrhoea, excessive bleeding or personal reasons) were also studied for return of fertility after ensuring that they were not using any other method of contraception and were exposed to the risk of pregnancy. The subjects from both groups were followed for a period of one year. The cumulative conception rates at one year were 72.5 and 83.6 per 100 subjects for ex-NET EN and ex-CuT 200 users who had discontinued the method for planning pregnancy and this difference was not statistically significant (P > 0.05). The median time for conception for ex-NET EN users was 7.8 months as compared to 3.7 months in ex-CuT 200 users but the cumulative conception rates at the end of one year show that future return of fertility in NET EN users does not appear to be adversely affected.

In 51 subjects who had discontinued NET EN due to amenorrhoea, the return of fertility was predictably slower and less. The return of fertility in subjects who discontinued NET EN for other reasons (e.g. excessive bleeding and other personal reasons) was similar to ex-NET EN and ex-CuT 200 users.  相似文献   

993.
994.
It is still not known how T cells are activated, which T-cell surface structures transmit activation signals, and if antigen-presenting cells possess activation structures for T cells. We have studied whether the T-cell receptor (TcR) must be engaged for T-cell activation to occur. By using membrane-incorporated monoclonal antibodies, we artificially forced T cells to bind to antigen-presenting cells in a mixed lymphocyte reaction system and thereby bypassed the need for TcR engagement and also made it possible for any surface molecule on antigen-presenting cells to deliver a stimulatory signal to the T cells. Theoretically, T cells would become polyclonally activated by this procedure. However, we found that they did not, even though they were intimately bound to the antigen-presenting cell, thus demonstrating that the TcR must participate in antigen/MHC binding in order for the T cells to become activated. This study does not exclude the possibility that antigen-presenting cells possess structures that can activate T cells.  相似文献   
995.
996.
Both abuse and new uses for benzodiazepines are reviewed. The pharmacology of benzodiazepines is summarized and statistics regarding their general use are given. The question of benzodiazepine abuse is reviewed in some detail and the question of rebound, recurrence of symptoms and physiological withdrawal is differentiated. Benzodiazepines are regarded as a very safe class of drugs and the abuse potential is felt to be negligible provided that they are prescribed for appropriate conditions and monitored carefully. The dangers of alternatives to benzodiazepines such as alcohol or barbiturates is emphasized. New uses for benzodiazepines are reviewed including the use of benzodiazepines in panic disorder, as well as an adjunct in the therapy of mania and some psychotic states. Rational prescribing of benzodiazepines is encouraged and the attitude that these are dangerous and addictive drugs is discouraged and put into perspective.  相似文献   
997.
Monoclonal antibody 131I-COC183B2, developed in our laboratory and proved to fit for human treatment was injected intraperitoneally or subcutaneously in 13 patients. In 8 cases with i.p. injection the disease corresponded with the image, i.e. 3 primary ovarian epithelial cancers showed positive images, 1 ovarian Krukenberg tumor was negative and the other 4 negative images included 1 uterine myoma and 3 ovarian teratomas. In the subcutaneous injection group, 4 cases had ovarian carcinoma, surgery and chemotherapy. Two negative images corresponded with the clinical status-in good health, another negative case had metastatic left supraclavicular lymph node due to ovarian mucinous adenocarcinoma. The last negative image in this group was a case of benign ovarian teratoma which was proved after surgery. The 1 positive case was waiting to be proved by a scheduled third operation. The computer scintigram calculation of T/NT was 5.35 to 13.7. The results suggest that this monoclonal antibody can be used for radioimmunoimaging for the localization of ovarian carcinoma, which is not only helpful for clinical staging and differential diagnosis but is also a good follow-up method.
  相似文献   
998.
999.
In a phase I-II study, 21 patients with relapsed or refractory acute leukemia were treated with 4'-deoxydoxorubicin (esorubicin), the 4'-deoxy derivative of doxorubicin. Four of 14 evaluable patients with acute nonlymphocytic leukemia (ANLL) in relapse or refractory to other anthracyclines achieved partial response (28.5%). Pharmacokinetics were similar to those of the parent compound, doxorubicin. Esorubicin has activity in ANLL and has pharmacologic properties comparable to those of other anthracyclines. Dose-limiting toxicity occurs in the form of mucositis, which may limit its use in combination with other antileukemic drugs.  相似文献   
1000.
In this report, we examine the functional significance of the molecular microheterogeneity of alpha-fetoprotein (AFP). In doing so, we have taken the direct approach of purifying the naturally occurring isomeric forms of fetal-derived AFP using a preparative anion exchange column linked to an automated fast protein liquid chromatography (FPLC) system followed by parallel testing of each isolated molecular variant for in vitro immunoregulatory activity. The data obtained demonstrate the presence of seven distinct variants of AFP as defined by their retention volumes on FPLC elution profiles, by their pIs on analytical IEF gels, and by Western blot analysis. Molecular mass determination by SDS-PAGE showed each isomer to be equivalent in size to 69,000-dalton native unfractionated AFP molecules. All the immunosuppressive activity of AFP was localized to a single variant representing only 6% of the total composition of native AFP. The immunoregulating isomer termed AFP-1 was the least acidic of the seven isolated variants with a pI of 5.1 and displayed a sialic acid content of 1 mol/mol of protein. The inhibitory activity of AFP-1 could be readily measured on T cell-dependent antibody synthesis, Con A-induced stimulation of Lyt-1+23- thymocyte DNA synthesis, and lymphokine-activated NK cell activity. All other isomers were without effect in these test systems. The immunosuppressive AFP-1 isomer also displayed the strongest growth-promoting influence on cultured bone marrow lymphocytes. There was no correlation between functional activity and degree of expression of sialic acid residues on the AFP molecules. These findings demonstrate that the immunoregulating function of AFP is confined to a distinct and relatively small subpopulation of native AFP molecules and should therefore contribute to the resolution of outstanding questions regarding the structure/function relationship of this onco-fetal glycoprotein.  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