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   730篇
  免费   36篇
  国内免费   24篇
儿科学   32篇
妇产科学   4篇
基础医学   58篇
口腔科学   9篇
临床医学   93篇
内科学   135篇
皮肤病学   14篇
神经病学   5篇
特种医学   185篇
外科学   70篇
综合类   3篇
预防医学   76篇
眼科学   9篇
药学   51篇
肿瘤学   46篇
  2023年   2篇
  2021年   8篇
  2020年   3篇
  2019年   3篇
  2018年   11篇
  2017年   5篇
  2016年   8篇
  2015年   8篇
  2014年   19篇
  2013年   27篇
  2012年   12篇
  2011年   18篇
  2010年   22篇
  2009年   10篇
  2008年   20篇
  2007年   37篇
  2006年   23篇
  2005年   28篇
  2004年   22篇
  2003年   13篇
  2002年   12篇
  2001年   13篇
  2000年   19篇
  1999年   10篇
  1998年   34篇
  1997年   48篇
  1996年   28篇
  1995年   27篇
  1994年   20篇
  1993年   12篇
  1992年   8篇
  1991年   13篇
  1990年   16篇
  1989年   26篇
  1988年   28篇
  1987年   18篇
  1986年   21篇
  1985年   26篇
  1984年   13篇
  1983年   8篇
  1982年   16篇
  1981年   7篇
  1980年   16篇
  1979年   7篇
  1978年   9篇
  1977年   8篇
  1976年   15篇
  1975年   4篇
  1894年   1篇
  1893年   1篇
排序方式: 共有790条查询结果,搜索用时 62 毫秒
1.
BACKGROUND: General practice is the focal point of primary care. There are national differences in the structure and organization of practice, the relationship with secondary care is being redefined, and in some countries major changes are taking place. AIM: To describe and examine differences in the service profiles of general practitioners (GPs) in European countries. METHOD: Standardized questionnaires in the national languages were sent to samples of GPs in 1993. Four areas of service provision were measured: the GP's position in the first contact with selected health problems, the involvement in minor surgery and the application of medical procedures, disease management and preventive care. The importance of the gatekeeping role, remuneration system, and geographical region in Europe was examined by comparing scores in appropriate national groupings. RESULTS: Data were received from 7233 GPs in 30 countries. Most national samples were random and the average response rate was 47%. In countries where GPs have a gatekeeping role, they had a relatively stronger position as doctors of first contact. In those countries where GPs were usually self-employed, they had a stronger role in disease management and screening for blood cholesterol. In the examination of the three structural elements of health care, the most striking differences were evident in the comparison between eastern and western Europe. GPs throughout Europe had a comparatively small role in organized health education. CONCLUSION: The position of GPs is weak in eastern Europe and some Mediterranean countries, where service profiles have a limited range. General practice was more comprehensive where the doctors had a gatekeeping role.  相似文献   
2.
Research into the results of resection of hilar bile duct cancer   总被引:31,自引:0,他引:31  
E J Boerma 《Surgery》1990,108(3):572-580
We found mentions of 581 resections of hilar bile duct cancer in the literature to January 1989. Resection in 499 patients, reported or updated since 1980, resulted in an operative mortality of 12% and a 5-year survival rate of 13%. Resections confined to the hepatic duct confluence or extended to the quadrate lobe led to an 8% operative mortality and a 7% 5-year survival rate, although resections combined with major liver resection gave a 15% operative mortality and a 17% 5-year survival rate. Despite the best treatments available, present-day resection modalities are usually still not radical. Extension of resection in the retrohilar and hepatoduodenal direction might further improve the long-term surgical results.  相似文献   
3.
Immortalized cell lines offer significant logistical advantages over primary cells when used for in-vitro studies. Immortalized cells may, however, exhibit important differences relative to their primary cell counterparts. In this study, microarrays were used to make a genome-wide comparison between primary human umbilical vein endothelial cells (HUVECs) and EA.hy926, an immortalized HUVEC cell line, in their baseline properties and in their response to inhibition of the mevalonate pathway with an inhibitor of hydroxy methylglutaryl-coenzyme A reductase (statin). HUVECs and EA.hy926 were incubated with control medium, atorvastatin, mevalonate, or a combination of atorvastatin and mevalonate for 24 h. Gene expression profiles were obtained in duplicates using Affymetrix Human Genome U133A 2.0 arrays (Santa Clara, California, USA). Probe-sets were selected according to the following criteria: a twofold or greater increase/decrease in atorvastatin-treated cells compared with untreated cells; a twofold or greater reversal of the effect of atorvastatin by combined treatment with atorvastatin and mevalonate; no significant change in gene expression in cells treated with mevalonate alone compared with untreated cells. Most genes that were expressed by untreated HUVECs, were also expressed by untreated EA.hy926 cells. EA.hy926 cells, however, constitutively expressed a large number of additional genes, many of which were related to cell cycle control and apoptosis. Atorvastatin induced differential expression (> or = twofold) of 103 genes in HUVECs (10 up, 93 down) and 466 genes in EA.hy926 cells (198 up, 268 down). Applying the above selection criteria, thrombomodulin and tissue plasminogen activator were up-regulated in both cell types, whereas, connective tissue growth factor, thrombospondin-1, and cysteine-rich angiogenic inducer 61 were down-regulated. In conclusion, EA.hy926 cells retain most of the characteristics of endothelial cells under baseline conditions as well as after treatment with atorvastatin. It is necessary, however, to carefully select and validate changes in genes that are the focus of studies when using EA.hy926 cells. While this cell line is highly useful in studies on some genes, including genes encoding molecules involved in regulating thrombohemorrhagic homeostasis, they appear to be less suited for studies focused on other genes, particularly those involved in the regulation of cell proliferation and apoptosis.  相似文献   
4.
5.
About two decades ago, changes in the demand for primary care in the Netherlands resulted in a need for more interprofessional collaboration. Health centres developed as a new supply of integrated care. The government was aware of the importance of this phenomenon in its policy to strengthen primary care. The encouragement of health centres was a crucial part of it. The development of this policy and the resulting growth in the number of health centres will be reviewed here. In general, this growth is lagging behind initial policy expectations, partly because of a lack of instruments to implement PHC policy. Examination of geographical distribution of health centres, however, shows a variation suggesting that local factors also affect the development of health centres. Empirical findings show that the number of newly built houses in an area and the political 'colour' of the alderman for public health play a role in the development of health centres and thus co-determine the results of a central promotion policy to a certain extent.  相似文献   
6.
7.
Summary— In the present study we have compared the steady state biopharmaceutic characteristics of four diltiazem once daily controlled release capsules: Mono-Tildiem LP 300® (300 mg), Adizem® XL (300 mg)1, Cardizem® (300 mg) and Dilacor® (240 mg). Sixteen healthy male volunteers (aged 22.9 ± 3.3 years, range 19–31 years) completed an open label, multiple oral dose, randomized, four-period crossover study without a washout period in between. The volunteers received each diltiazem formulation once daily for four days. Trough diltiazem and metabolites plasma concentrations were determined on days 3 and 4. The 24-h plasma concentration-time profiles were assessed after the dose on day 4 of each period. The following steady state pharmacokinetic parameters for diltiazem were calculated: the minimum plasma concentration (cmin), the maximum plasma concentration (cmax), the time to reach that concentration (tmax), the time interval during which the plasma concentration exceeds 50% of cmax (t50), the area under the plasma concentration-time curve (AUC72–96) and the peak-to-trough fluctuation (PTF). For the metabolites of diltiazem, N-mono-desmethyl-diltiazem (NDM) and desacetyldiltiazem (DAD), AUC72–96 (AUCNDM and AUCDAD) and the ratio metabolite/parent compound were calculated. Steady state was achieved on day 3. Except one, all controlled release formulations have satisfactory controlled release properties allowing once daily administration. However, significant (P < 0.05) differences were found between the pharmacokinetic characteristics which do not allow exchange of the various formulations. Concentrations well below 50 ng·mL-1 in the morning hours were observed for Dilacor® (240 mg) and Adizem® XL (300 mg), which could be a disadvantage of these formulations as it is well-known that ischaemic events occur at a higher rate during that part of the day. The plasma concentration profiles of NDM and DAD, the major circulating metabolites, parallel the plasma concentration profiles for the parent compound. From a clinical point of view, all treatments were well tolerated.  相似文献   
8.
Intestinal obstruction proximal to a transition zone without an interposed physical barrier usually indicates Hirschsprung disease. The authors report one case of focal small bowel muscular thinning just distal to a transition zone that produced clinical and radiographic findings that simulated long-segment Hirschsprung disease in a 2-day-old infant.  相似文献   
9.
Recently, in-vitro maturation (IVM) of immature human oocytes recovered from non-stimulated follicles has been applied in the treatment of infertility. However, in previous reports, very few embryos cultured in conventional medium have reached the expanded blastocyst stage following in-vitro maturation and fertilization (IVM/IVF). The objective of this study was to investigate whether the developmental competence of human embryos following IVM/IVF could be enhanced by the use of a human ampullary cell co-culture system. Immature human oocytes were aspirated from small follicles at Caesarean section and then cultured in medium containing human menopausal gonadotrophin for 36 to 48 h, followed by insemination. Zygotes were randomly cultured either in conventional culture medium alone or in the co-culture system. Of 48 embryos cultured in conventional medium alone, all arrested at the 2-16- cell stage on day 3 after insemination. Of 46 embryos cultured in the co-culture system, 26 embryos (56.5%) arrested at the 2-16-cell stage. Six embryos (13%) developed to the morula stage. Fourteen embryos (30.4%) developed to expanded blastocysts and two blastocysts were hatching on day 7 after insemination. We conclude that co-culture significantly enhances the development of blastocysts in embryos resulting from IVM/IVF.   相似文献   
10.
The differentiation of the urinogenital system and the appendicular skeleton in vertebrates is under the control of Hox genes. The common control of digit and gonad differentiation raises the possibility that patterns of digit formation may relate to spermatogenesis and hormonal concentrations. This work was concerned with the ratio between the length of the 2nd and 4th digit (2D:4D) in humans. We showed that (i) 2D:4D in right and left hands has a sexually dimorphic pattern; in males mean 2D:4D = 0.98, i.e. the 4th digit tended to be longer than the 2nd and in females mean 2D:4D = 1.00, i.e. the 2nd and 4th digits tended to be of equal length. The dimorphism is present from at least age 2 years and 2D:4D is probably established in utero; (ii) high 2D:4D ratio in right hands was associated with germ cell failure in men (P = 0.04); (iii) sperm number was negatively related to 2D:4D in the right hand (P = 0.004); (iv) in men testosterone concentrations were negatively related to right hand 2D:4D and in women and men LH (right hand), oestrogen (right and left hands) and prolactin (right hand) concentrations were positively correlated with 2D:4D ratio and (v) 2D:4D ratio in right hands remained positively related to luteinizing hormone and oestrogen after controlling for sex, age, height and weight.   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