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   4020441篇
  免费   284164篇
  国内免费   9064篇
耳鼻咽喉   55861篇
儿科学   131685篇
妇产科学   110607篇
基础医学   573513篇
口腔科学   112006篇
临床医学   370116篇
内科学   775591篇
皮肤病学   92902篇
神经病学   325783篇
特种医学   152083篇
外国民族医学   1141篇
外科学   600532篇
综合类   83649篇
现状与发展   15篇
一般理论   1602篇
预防医学   314653篇
眼科学   93668篇
药学   296158篇
  16篇
中国医学   7855篇
肿瘤学   214233篇
  2019年   32267篇
  2018年   44626篇
  2017年   33826篇
  2016年   38893篇
  2015年   43799篇
  2014年   61175篇
  2013年   92659篇
  2012年   124853篇
  2011年   132580篇
  2010年   79744篇
  2009年   75843篇
  2008年   124109篇
  2007年   131941篇
  2006年   133872篇
  2005年   129190篇
  2004年   124307篇
  2003年   119813篇
  2002年   115876篇
  2001年   183119篇
  2000年   187966篇
  1999年   158924篇
  1998年   47190篇
  1997年   41476篇
  1996年   41628篇
  1995年   40013篇
  1994年   36751篇
  1993年   34576篇
  1992年   124634篇
  1991年   120815篇
  1990年   117507篇
  1989年   113896篇
  1988年   104813篇
  1987年   102721篇
  1986年   96716篇
  1985年   92692篇
  1984年   69296篇
  1983年   59000篇
  1982年   35177篇
  1981年   31677篇
  1979年   62889篇
  1978年   44720篇
  1977年   37761篇
  1976年   35545篇
  1975年   37965篇
  1974年   45282篇
  1973年   43145篇
  1972年   40606篇
  1971年   38140篇
  1970年   35117篇
  1969年   33798篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
131 patients with resectable, node-positive breast cancer were treated at the National Institute for Cancer Research of Genoa, Italy with a systemic adjuvant regimen based on 14 cycles of chemotherapy, immunostimulation with levamisole, and--for postmenopausal patients--hormone therapy with tamoxifen. The present evaluation is performed eleven years after the admission of the first patient: so far, 75 patients (57.3%) have relapsed and 52 (39.7%) have died. An analysis of prognostic factors for relapse and death shows that the number of positive axillary lymph nodes and the dimension of the primary tumor are significantly associated with survival and relapse-free survival, while age and menopausal status are not.  相似文献   
992.
Summary. In this study, we have examined our records for the isolation of Candida tropicalis from clinical specimens of patients with heterogeneous clinical presentations during the past 5 years. We have found that this species ranks third among all yeasts in frequency of isolation from clinical specimens and that the trend of recovery from the specimens is rising over the years. The isolation rate of C. tropicalis was highest from urine specimens (36%) followed by respiratory specimens (22%). The frequency of isolation of C. tropicalis from vaginal specimens was relatively high (14%), however the trend was declining over the years. In general, the high recovery of Candida tropicalis from clinical specimens of patients with variable disease supports the views of this organism being a major pathogen.
Zusammenfassung. Die Studie basiert auf einer Durchsicht der Patientenarchive der letzten fünf Jahre auf die Isolationshäufigkeit von Candida tropicalis aus klinischen Untersuchungsmaterialien von Patienten mit unterschiedlichen klinischen Krankheitsbildern. Diese Hefeart war die dritthäufigste mit steigender Tendenz über die Jahre. Die Isolierungsrate von C. tropicalis war am höchsten aus Urin (36%), gefolgt von Respirationstrakt-Materialien (22%). Die Isolationshäufigkeit aus dem hinteren Scheidengewölbe war relativ hoch (14%), nahm jedoch mit den jahren ab. Allgemein unterstreicht die hohe Isolationsrate von C. tropicalis aus klinischen Untersuchungsmaterialien die ätiologische Bedeutung dieses Erregers.  相似文献   
993.
Zusammenfassung  Ein PCR-Nachweis für gentechnisch ver?nderten Mais ?Event 176? der Fa. Ciba-Geigy wurde etabliert. Der Mais enth?lt Gene, die Selbstschutz gegen den Maiszünsler (Delta-Endotoxin-Gen ausBacillus thuringiensis) und Toleranz gegen das Herbizid Basta (Phosphinothricin-Resistenz-Gen ausStreptomyces hygroscopicus) vermitteln. Zudem enth?lt der Mais ein Ampicillin-Resistenz-Gen. Für die Amplifikation von Bereichen aus allen drei Genen wurden PCR-Primer entworfen. Mit Hilfe dieser Primer und mit ?Event 176?-Mais-DNA als Template konnten die entsprechenden Genbereiche in der PCR amplifiziert werden. Die PCR-Produkte wurden sequenziert, um ihre Identit?t zu best?tigen. Mit Hilfe der Delta-Endotoxin-PCR wurden, auch in Gegenwart von 104fachem überschu? nicht gentechnisch ver?nderter Mais-DNA, fünf haploide Genome der ?Event 176?-DNA nachgewiesen.
Identification of genetically modified maize by PCR
Summary  A PCR-test for the genetically modified maize ?Event 176? of Ciba-Geigy was established. The maize contains genes conferring resistance to the European corn borer (delta-endotoxin gene fromBacillus thuringiensis) and tolerance to the herbicide Basta (phosphinothricin resistance gene fromStreptomyces hygroscopicus). The maize contains also an ampicillin resistance gene. Primers were designed and using ?Event 176?-maize-DNA as template internal regions of the three genes were amplified with PCR. The PCR products were sequenced to confirm their identity. Using the deltaendotoxin primers in PCR down to 5 haploid genomes of ?Event 176?-DNA could be detected, even in the presence of a 104fold excess of DNA from non-modified maize.
  相似文献   
994.
The Dundee Memory Clinic was established in 1991. This paper reviews the diagnosis of the first 150 attenders and compares the findings with those of other memory clinics.  相似文献   
995.
996.
997.
There has been a remarkable change in the scenario of therapeutic apheresis in the last 14 years in India. The crude method of manual removal of blood followed by separation of plasma by gravity, keeping it in the bottle for a long time, has now been totally replaced by plasmapheresis, centrifugation, membrane filtration, and immunoadsorption techniques. The indications for use have also changed from a list of limited indications in the beginning to include all immune complex disorders. The clinical beneficiaries have also increased from blood bankers to nephrologists and immunologists in addition to oncologists. Efforts are now underway with the help of the Indian Society for Apheresis (founded in 1985) to popularize the newer methods of cryofiltration, photopheresis and heparin extracorporeal low-density lipoprotein (HELP) and DALI apheresis systems besides the specialized techniques of immunoadsorption using filters, columns, or ligands. This is suggestive of a positive trend for the treatment of immune complex disorders.  相似文献   
998.
999.
Lead poisoning--one approach to a problem that won't go away.   总被引:7,自引:1,他引:6       下载免费PDF全文
A reduction in sources of environmental lead exposure has resulted in substantial declines in mean blood lead concentrations of all age groups in the United States. However, some segments of the population continue to have unacceptable levels of lead exposure and elevated blood lead concentrations. In addition, virtually all residents of industrialized countries have bone lead stores that are several orders of magnitude greater than those of our preindustrial ancestors. Recent studies suggest that these skeletal lead stores adversely affect health and can contribute to reduced birth weights, aggressive behavior in children, and anemia, hypertension, and kidney disease in adults. Evidence is described that demonstrates that an increase in dietary calcium consumption can reduce lead absorption and toxicity from exogenous and endogenous lead exposure. A relatively inexpensive and effective way to reduce the substantial morbidity that will result from widespread lead exposure is by fortification of a variety of foods with low levels of calcium. This approach can complement other efforts to prevent lead exposure and reduce lead toxicity.  相似文献   
1000.
Purpose. To present a model-dependent approach for the assessment of the in vivo drug dissolution profile based on in vitrodata for the multiple unit dosage form, as an alternative to the numerical method proposed in the study by Hayashi et al, Pharm. Res. 12:1333–1337 (1995). Methods. The data for aspirin granules administered to healthy subjects obtained in the above mentioned study were re-evaluated. The subject dissolution system was considered to consist of two subsystems connected in series, i.e. the subsystem describing the gastric-emptying process and the subsystem describing the intestinal dissolution process. The frequency response method was used to model the subject dissolution system. Results. The model in vivodissolution profile of aspirin, assessed as the integral of the model weighting function of the subject dissolution system, was in agreement with the in vivo cumulative absorption profile calculated by the Wagner-Nelson method. Conclusions. Comparison of dynamic properties of the subject dissolution system with the subsystem describing the gastric-emptying process yielded quantitative confirmation of the decisive role of the gastric-emptying process in the in vivodrug dissolution after administration in the multi unit dosage form.  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