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   1182篇
  免费   13篇
化学工业   67篇
金属工艺   1篇
机械仪表   5篇
建筑科学   3篇
能源动力   3篇
轻工业   46篇
水利工程   1篇
石油天然气   1篇
无线电   3篇
一般工业技术   17篇
冶金工业   1032篇
原子能技术   1篇
自动化技术   15篇
  2024年   1篇
  2023年   1篇
  2022年   7篇
  2021年   10篇
  2020年   6篇
  2019年   7篇
  2018年   6篇
  2017年   8篇
  2016年   8篇
  2015年   5篇
  2014年   5篇
  2013年   15篇
  2012年   7篇
  2011年   10篇
  2010年   9篇
  2009年   5篇
  2008年   14篇
  2007年   11篇
  2006年   4篇
  2005年   3篇
  2004年   1篇
  2003年   4篇
  2002年   3篇
  2001年   2篇
  1999年   20篇
  1998年   307篇
  1997年   202篇
  1996年   119篇
  1995年   69篇
  1994年   59篇
  1993年   55篇
  1992年   7篇
  1991年   17篇
  1990年   9篇
  1989年   9篇
  1988年   19篇
  1987年   14篇
  1986年   9篇
  1985年   8篇
  1983年   2篇
  1982年   6篇
  1981年   8篇
  1980年   7篇
  1978年   7篇
  1977年   28篇
  1976年   59篇
  1975年   1篇
  1968年   1篇
  1954年   1篇
排序方式: 共有1195条查询结果,搜索用时 31 毫秒
161.
In this study we characterized the pattern of use of preventive therapies for specific respiratory diseases within a cohort of homosexual men and assessed the impact of targeted feedback on the level of compliance with guidelines for these diseases. All human immunodeficiency virus seronegative (HIV-) (n=169) and acquired immune deficiency syndrome (AIDS)-free human immunodeficiency virus seropositive (HIV+) (n=154) participants in our cohort, who completed four annual visits between October 1989 and December 1993, were identified. Information about the use of purified protein derivative (PPD) (tuberculin) testing, history of pneumococcal vaccinations, influenza vaccinations, use of Pneumocystis carinii pneumonia (PCP) prophylaxis, symptoms and CD4 counts was obtained yearly for each subject. In 1992, participating physicians were provided with feedback regarding the overall levels of compliance with contemporary guidelines for the prevention of respiratory disease. As part of this exercise, the guidelines were distributed and discussed. The percentage of HIV+ patients who underwent PPD testing increased from 43 to 65% during the study (p=0.001). Significantly more HIV+ than HIV- patients underwent PPD testing (p<0.001). A total of 144 (94%) HIV+ men received at least one influenza vaccination compared to 60 (35%) HIV- men (p<0.001). Utilization of influenza vaccination in the HIV+ group significantly increased from 78% in 1992 to 92% in 1993 (p<0.001). A total of 104 (68%) HIV+ men received pneumococcal vaccination compared to 2 (1%) HIV- men (p<0.001). Among HIV+ individuals whose absolute CD4+ count was less than 200 cells x mm(-3), the percentage of men who received primary PCP prophylaxis was 0, 86, 72 and 88 for the years 1990-1993, respectively. Among HIV+ patients whose only eligibility criterion for PCP prophylaxis was a CD4+ percentage <20%, compliance was 55, 30, 37 and 50% for the years 1990-1993, respectively. Among HIV+ subjects, increases in the compliance level were noted for all preventive therapies after targeted feedback was provided during the last quarter of 1992. However, only utilization of influenza vaccine exceeded a 90% compliance in 1993. These data demonstrate that a suboptimal level of compliance with current guidelines for the prevention of respiratory disease among human immunodeficiency virus-infected individuals can be significantly improved using targeted feedback. Although it is likely that similar effects could be achieved in other populations or the community at large, this remains to be demonstrated.  相似文献   
162.
163.
BACKGROUND/AIM: A herbal medicine, Sho-saiko-to (TJ-9), has recently been orally administered to patients with chronic liver disease in Japan and has been reported to inhibit the development of hepatocellular carcinoma. The aim of this study was to investigate whether TJ-9 has an inhibitory effect on the development of preneoplastic lesions and liver fibrosis in rats. METHODS: The effects of the TJ-9 were examined using the choline-deficient L-amino acid-defined (CDAA) diet-induced liver fibrosis model in 16-week-old male Wistar rats. RESULTS: TJ-9 (1% w/w) prevented fibrosis, as indicated by reduced hydroxyproline content in the liver and inhibition of the increase in a serum marker of fibrosis (hyaluronic acid), without reducing the increase in serum alanine aminotransferase and aspartate aminotransferase. TJ-9 also reduced the expression of type III procollagen alpha 1 mRNA in the liver, as well as the proliferation of myofibroblast-like cells (activated stellate cells, activated Ito cells). Furthermore, TJ-9 reduced the number of preneoplastic lesions, detected as enzyme-altered (glutathione S-transferase placental form-positive) lesions, in the liver. CONCLUSIONS: These results indicate that the herbal medicine Sho-saiko-to (TJ-9) prevents fibrosis as well as preneoplastic lesions, not by inhibiting hepatocyte cell death but by inhibiting the activation of stellate cells, which are considered to be the main collagen-producing cells, leading to a reduction in the development of preneoplastic lesions.  相似文献   
164.
G-banding and C-banding of chromosomes were studied in populations of the red-backed mouse Clethrionomys rufocanus from 11 localities of eastern Russia. Intrapopulation polymorphism of autosome 3 caused by the deletion-duplication of the short-arm heterochromatin (2n = 56; NFa = 56-58) was demonstrated. The karyotype of Cl. rufocanus from continental populations and Sakhalin Island was shown to have a large subtelocentric chromosome of pair 3 (NFa = 58), whereas in the population from Kunashir Island, chromosomes of this pair were acrocentric (NFa = 56). One animal from the population of the Kedrovaya Pad' Reserve (Primorsk krai) had a pericentric inversion (acrocentric morphology) of the Y chromosome. In two animals, a female from the Ussuriiskii Reserve (Primorsk krai) and a male captured near the Tomari Settlement (Sakhalin Island), a pericentric inversion of one chromosome of pair 6 was found (NFa = 59). The inversion detected in the animal from the Sakhalin population was accompanied by the loss of the centromeric heterochromatin. In contrast, the inversion of the chromosome pair 6, which was found in the mouse from the Primorsk krai population, did not involve the loss of centromeric heterochromatin. Analysis of our results and data from the literature showed that the karyotype of Cl. rufocanus is not constant, as was thought earlier. The percentage of animals with abnormal karyotype (1.6%) was higher than in other groups of red-backed mice studied (0.12-0.7%).  相似文献   
165.
Pancreatic islets prelabelled with either 86Rb or 45Ca were exposed to a rise in D-glucose concentration from 2.8 to 16.7 mM whilst perifused in the presence of 2 microM glibenclamide, 30 mM extracellular K+ and both 30 mM K+ and 250 microM diazoxide. In all three situations, the rise in glucose concentration provoked a dramatic increase in insulin output, despite unchanged or even increased efflux of 86Rb from the prelabelled islets. Also in all three situations, glucose sharply decreased effluent radioactivity from islets prelabelled with 45Ca but perifused in the absence of extracellular Ca2+, while augmenting 45Ca efflux, to a variable extent, from islets perifused at normal extracellular Ca2+ concentration (1.0 mM). It is proposed, therefore, that the insulinotropic action of D-glucose in depolarized islets, and presumably also under normal conditions, may involve the gating of voltage-insensitive Ca2+ channels.  相似文献   
166.
167.
The influence of specific factors on in situ methanolic esterification of rice bran oil (RBO) using sulfuric acid catalyst was investigated. using high-FFA rice bran was found to be the most effective means to increase methyl ester yields. The ester content of the extract increased about 67% when the FFA content of oil was increased from 16.6 to 84.5%. Increasing the reaction time beyond 30 min did not affect yields. Increasing the temperature from 20 to 65°C elevated the FAME yield by about 30%, but increasing the amount of acid catalyst above 5 mL did not enhance yield, and increasing the methanol dose from 200 to 250 mL had a negligible effect.  相似文献   
168.
169.
Fingerprints were obtained from 100 patients with mitral valve prolapse and compared with those of 100 control subjects matched for sex and race. Arches were found in 16.8 percent of all digital patterns in patients with mitral valve prolapse but in only 2.5 percent of all digits in the control group. Whereas no patient in the control group had four or more arches, 19 percent of patients with mitral valve prolapse had this finding. In addition, arches were found on 16 and 9 percent, respectively, of digits IV and V in patients with mitral valve prolapse but were not found on these digits in the control group. The finding of four or more arches or arches on digits IV or V may be important supportive evidence of mitral valve prolapse when evaluating patients with atypical chest pain and palpitations. Antenatal factors may be involved in the pathogenesis of mitral valve prolapse since it is possible that a genetic or environmental factor that interferes with the development of the mitral valve may also influence epidermal ridge patterns.  相似文献   
170.
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