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   516篇
  免费   30篇
  国内免费   3篇
耳鼻咽喉   3篇
儿科学   18篇
妇产科学   65篇
基础医学   79篇
口腔科学   6篇
临床医学   28篇
内科学   101篇
皮肤病学   17篇
神经病学   41篇
特种医学   2篇
外科学   48篇
综合类   2篇
预防医学   66篇
眼科学   6篇
药学   32篇
中国医学   2篇
肿瘤学   33篇
  2023年   11篇
  2022年   17篇
  2021年   21篇
  2020年   18篇
  2019年   22篇
  2018年   23篇
  2017年   14篇
  2016年   13篇
  2015年   16篇
  2014年   23篇
  2013年   22篇
  2012年   42篇
  2011年   37篇
  2010年   21篇
  2009年   13篇
  2008年   21篇
  2007年   18篇
  2006年   14篇
  2005年   10篇
  2004年   14篇
  2003年   13篇
  2002年   8篇
  2001年   7篇
  2000年   6篇
  1999年   5篇
  1998年   3篇
  1995年   1篇
  1994年   3篇
  1993年   4篇
  1992年   9篇
  1991年   2篇
  1990年   8篇
  1989年   6篇
  1988年   5篇
  1987年   6篇
  1986年   7篇
  1985年   8篇
  1984年   9篇
  1983年   10篇
  1982年   5篇
  1981年   10篇
  1980年   3篇
  1979年   6篇
  1978年   3篇
  1977年   2篇
  1976年   2篇
  1975年   1篇
  1974年   2篇
  1973年   2篇
  1968年   1篇
排序方式: 共有549条查询结果,搜索用时 15 毫秒
61.
62.
Ten ovarian and 2 cervical tumour cell lines were analysed for the production of pregnancy-associated proteins. Pregnancy-associated plasma protein-A (PAPP-A) was detected by radioimmunoassay in culture media of 2 out of 4 (50%) tumour granulosa cell lines (mean = 104 microIU/10(5) cells/24 h) but not in any ovarian (n = 6) or cervical (n = 2) tumour cell lines. By contrast, human chorionic gonadotrophin (hCG), pregnancy specific beta 1-glycoprotein and alpha-fetoprotein (AFP) were not detected in any of the PAPP-A positive media. Only two cell lines produced hCG (58.5 and 25.5 mIU/10(5) cells/24 h). No AFP was produced by any of these 12 cell lines, whereas placental protein 5 was positive in 7. None of these proteins were detected in the culture media of 4 cell lines. In vitro derived PAPP-A was immunologically indistinguishable from either pregnancy or ovarian follicular PAPP-A. All PAPP-A species interacted reversibly with immobilised heparin and were determined by molecular sieve chromatography to have an apparent molecular weight of 820,000 daltons. Cultured tumour granulosa cells specifically synthesised and secreted a large protein which was immunologically and physicochemically indistinguishable from in vivo (pregnancy and ovarian follicular) derived PAPP-A.  相似文献   
63.
In vitro studies have suggested that the cyclic AMP system may be the mediator of bile acid-induced colonic secretion. The aims of our experiments were to quantify thein vivo effect of various doses of deoxycholic acid (DCA) on adenylate cyclase activity (AC) and net secretion in the rabbit colon. AC increased significantly (P<0.01) with each increasing concentration of DCA; at 8 mM the activity was 126±6 pmoles cAMP/mg protein/min, or 4 times the control. Phosphodiesterase activity (PDE) was affected and significantly decreased (P<0.01) only by 8 mM DCA. The volume of luminal fluid increased significantly (P<0.01) as a bicarbonate-rich solution with 4, 6, and 8 mM DCA in graded fashion. In conclusion, stimulation of a colonic mucosal cAMP system is strongly implicated as mediating DCA-induced colonic secretion.Supported in part by NIH grant AM 15631.  相似文献   
64.
Summary In mice infected intraperitoneally with 103 intracerebral suckling mice LD50 of Semliki Forest virus an additive reduction in mortality was found when the protective effect of hyperthermia and synthetic polyriboinosinic and polycytidylic acids (Poly I:C) was combined.The effects of the two treatments seem to be independent of each other as Poly I:C was found to have no influence on the body temperature of mice, nor did hyperthermia increase the amount of interferon induced by Poly I:C.With 3 Figures  相似文献   
65.
Semen quality and exposure to persistent organochlorine pollutants   总被引:2,自引:0,他引:2  
BACKGROUND: Inconsistent results have been found in previous human studies on male reproductive toxicity of persistent organochlorine pollutants. The majority of studies have been conducted among selected populations of infertility clients or among occupational cohorts including a limited number of participants. METHODS: We conducted a cross-sectional study of semen quality and serum concentration of 2,2',4,4',5,5'-hexachlorobiphenyl (CB-153) and 1,1-dichloro-2,2-bis (p-chlorophenyl)-ethylene (p,p'-DDE) among 763 men. We included men from all regions in Greenland (n = 194), fishermen from Sweden (n = 185), inhabitants of the city of Kharkiv, Ukraine (n = 195), and inhabitants of the city of Warsaw, Poland (n = 189). Blood samples were analyzed for CB-153 and p,p'-DDE using gas chromatography-mass spectrometry and adjusted for serum lipids. RESULTS: Sperm concentration was not impaired with increasing serum CB-153 or p,p'-DDE levels in any of the separate groups or overall. Similarly, the proportion of morphologically normal sperm was not associated with either CB-153 or p,p'-DDE blood concentration. However, sperm motility was inversely related to CB-153 concentration in Greenland and the Swedish fishermen population. Across all 4 regions, the sperm motility decreased on average by 3.6% (95% confidence interval = 1.7% to 5.6%) per one-unit increase in the log of blood CB-153 (ng/g lipid). The concentration of p,p'-DDE was negatively associated with sperm motility in the Greenlandic population and in the compiled dataset. CONCLUSION: Adult exposure to persistent organochlorine pollutants within the ranges observed in the present study is not likely to cause reduction in sperm concentration or morphology. However, higher exposure may be associated with impaired sperm motility.  相似文献   
66.
The immunoperoxidase technique was used to study the occurrence of placenta-associated plasma protein A (PAPP-A, SP4) in formalin-fixed paraffin-embedded tissue specimens from 15 hydatidiform moles, 6 invasive moles and 7 choriocarcinomas. PAPP-A was found in the syncytiotrophoblast of all hydatidiform moles, in 5 of the 6 invasive moles and in 6 of the 7 choriocarcinomata. No clinical difference was observed between PAPP-A positive and negative cases of invasive disease.  相似文献   
67.
Summary The influence of temperature on mortality, virus multiplication and interferon production in adult mice infected with Coxsackie B1 virus was investigated. Mice kept at +4° C had a rectal temperature which was 1.5° C lower than that of mice kept at +25° C. The animals with the lowest temperature had a higher and persistent virus content in the serum, liver and brain. All these mice succumbed, whereas the animals kept at +25° C survived. Interferon was found in connection with the high virus multiplication in mice at +4° C, but no interferon was demonstrated in mice at +25° C.It is presumed that factors other than interferon played a decisive role in the survival from infection with this strain of Coxsackie B1 virus in the strain of mice studied.  相似文献   
68.
Serum levels of pregnancy zone protein (PZP) were measured in 506 apparently normal males and 329 normal non-pregnant females, the age range being 18 to 70 years. The estimations of PZP were performed by sensitive radiorocket-line immunoelectrophoresis. The distribution of the data had a marked positive skew in both sexes which was reduced following logarithmic transformation. Serum concentrations in both men and women were found to increase significantly with advancing age. This increase and the mean concentrations were significantly higher in females.  相似文献   
69.
In order to maximise compliance, the future antimalarial treatment should ideally require just a single-dose administration. This, in turn, demands new fast-acting effective drugs. Currently, methods to measure the in vitro killing rate of antimalarials are based on parasite growth. We have developed and validated a method to determine and classify antimalarial agents based on their cidal or static activity following quantitative Real Time PCR (RT-PCR) analysis. The method described here is a fast, reliable and user-friendly technique with a medium throughput. Metabolic activity of the parasite is followed by measuring mRNA expression levels of several genes during 5 parasite life cycles. mRNA from the parasite culture is then retrotranscribed to cDNA and quantified by RT-PCR. This new method provides a rapid and reproducible way to accurately measure the antimalarial activity of new compounds in vitro against Plasmodium falciparum.  相似文献   
70.
PURPOSE: To evaluate the characteristics and quality of adverse drug reaction (ADR) reports submitted by pharmacists, and thereby assess the possible contribution of pharmacists to the spontaneous reporting system for ADRs in Norway. METHODS: An open, prospective study was conducted where dispensing pharmacists from 39 pharmacies were encouraged to report ADRs over a 3-month period. The submitted ADR reports were compared to reports by physicians from the same time period. All reports were evaluated for selected characteristics, that is distribution of Anatomical Therapeutic Chemical (ATC) classification codes of suspected drugs, distribution of ADRs according to system-organ classes and the quality of the reports. RESULTS: A total of 118 reports covering 274 ADRs received from the pharmacists were compared to 109 ADR reports with 304 ADRs submitted by physicians. Pharmacists more often reported ADRs related to cardiovascular drugs, alimentary tract and metabolism drugs and respiratory drugs, whereas physicians more frequently reported ADRs related to musculoskeletal drugs and antineoplastic and immunomodulating agents. ADRs reported by pharmacists more frequently described gastrointestinal reactions while physicians reported more ADRs in relation to the cardiovascular and blood system. Whereas 68% of the physicians' reports were classified as serious, only 5% of the pharmacists' reports were serious. More than 50% of the reports submitted by pharmacists concerned ADRs following a generic substitution, in contrast to only 2% of the physicians' reports. The pharmacists' reports were found to be of a lower documentation grade. However, there was no substantial difference in a subjective assessment of the quality of information in the reports submitted by the two categories of health professionals. CONCLUSIONS: Pharmacists submit valuable ADR reports which provide information complimentary to physicians' reports. This emphasises that pharmacist ADR reporting might constitute an important addition to the spontaneous reporting system.  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