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   3311篇
  免费   20篇
电工技术   33篇
化学工业   102篇
金属工艺   42篇
机械仪表   37篇
建筑科学   51篇
矿业工程   3篇
能源动力   31篇
轻工业   79篇
水利工程   3篇
石油天然气   2篇
无线电   133篇
一般工业技术   219篇
冶金工业   2422篇
原子能技术   8篇
自动化技术   166篇
  2023年   5篇
  2021年   9篇
  2020年   9篇
  2019年   11篇
  2018年   14篇
  2017年   16篇
  2016年   12篇
  2015年   8篇
  2014年   20篇
  2013年   45篇
  2012年   24篇
  2011年   54篇
  2010年   51篇
  2009年   27篇
  2008年   43篇
  2007年   30篇
  2006年   39篇
  2005年   32篇
  2004年   28篇
  2003年   33篇
  2002年   26篇
  2001年   33篇
  2000年   36篇
  1999年   91篇
  1998年   737篇
  1997年   374篇
  1996年   248篇
  1995年   183篇
  1994年   154篇
  1993年   167篇
  1992年   36篇
  1991年   45篇
  1990年   38篇
  1989年   45篇
  1988年   41篇
  1987年   42篇
  1986年   39篇
  1985年   41篇
  1984年   26篇
  1983年   19篇
  1982年   29篇
  1981年   22篇
  1980年   40篇
  1979年   13篇
  1978年   18篇
  1977年   64篇
  1976年   141篇
  1975年   19篇
  1974年   5篇
  1972年   9篇
排序方式: 共有3331条查询结果,搜索用时 15 毫秒
41.
Fourteen women with amenorrhea-galactorrhea were treated with bromo-ergocryptine. Serum prolactin hPRL, hLH, hFSH, estradiol 17-beta (E2), and progesterone values were determined before and during treatment. No consistent pretreatment hormonal pattern was found. During treatment hPRL levels fell in 13 of 14 patients, and E2 rose in 12 of 14 patients. Levels of hLH became normal, and amounts of hFSH did not change. Galactorrhea lessened in all cases and ceased in 11. Menses resumed in 11 patients and 3 women became pregnant. Cessation of galactorrhea and resumption of menses occurred irrespective of initial hPRL or hLH levels. It is suggested that improvement of galactorrhea and resumption of menses in some patients with normal hPRL values are the result of increased serum E2 levels and may be due to a direct action of bromo-ergocryptine on the ovary. Bromo-ergocryptine may also be effective in treatment of amenorrhea, unassociated with galactorrhea or elevated hPRL levels.  相似文献   
42.
Cardiac patients who have undergone 99mTc-stannous pyrophosphate (99mTc-PYP) myocardial imaging can be injected 24 hours later with 99mTc-pertechnetate (99mTc04) to assess left ventricular function. Reduction of 99mTc04 by tin remaining in the blood following the stannous pyrophosphate injection causes labeling of the red cells by 99mTc04 and the creation of a vascular tracer suitable for electrocardiographically gated imaging.  相似文献   
43.
44.
45.
Rancinamycins are secondary metabolites produced by Streptomyces lincolnensis in a sulfur-depleted culture medium. The structures (except stereochemistry) of the main components of the rancinamycin-complex were determined by the use of IR, UV, PMR, and CMR spectra.  相似文献   
46.
The aim of the present experiments was to determine the role of insulin and glucagon in the regulation of basal glucose production in dogs fasted overnight. A deficiency of either or both pancreatic hormones was achieved by infusin somatostatin (1 mug/kg per min), a potent inhibitor of both insulin and glucagon secretion, alone or in combination with intraportal replacement infusions of either pancreatic hormone. Infusion of somatostatin alone caused the arterial levels of insulin and glucagon to drop rapidly by 72+/-6 and 81+/-8%, respectively. Intraportal infusion of insulin and glucagon at rates of 400 muU/kg per min and 1 ng/kg per min, respectively, resulted in the maintenance of the basal levels of each hormone. Glucose production was measured using tracer (primed constant infusion of [3-3H]glucose) and arteriovenous difference techniques. Isolated glucagon deficiency resulted in a 35+/-5% (P less than 0.05) rapid and sustained decrease in glucose production which was abolished upon restoration of the plasma glucagon level. Isolated insulin deficiency resulted in a 52+/-16% (P less than 0.01) increase in the rate of glucose production which was abolished when the insulin level was restored. Somatostatin had no effect on glucose production when the changes in the pancreatic hormone levels which it normally induces were prevented by simultaneous intraportal infusion of both insulin and glucagon. In conclusion, in the anesthetized dog fasted overnight; (a) basal glucagon is responsible for at least one-third of basal glucose production, (b) basal insulin prevents the increased glucose production which would result from the unrestrained action of glucagon, and (c) somatostatin has no acute effects on glucose turnover other than those it induces through perturbation of pancreatic hormone secretion. This study indicates that the opposing actions of the two pancreatic hormones are important in the regulation of basal glucose production in the postabsorptive state.  相似文献   
47.
The mitotic index of mouse corneal epithelium was studied during and after 0.5-- 24 hours exposures to 9.9-39.4 kilooersteds constant magnetic fields. It was shown that 0.5, 1 and 3 hours exposures to a 39.4 kilooersteds constant magnetic field inhibited the mitotic activity whereas 8 and 24 hours exposures caused its stimulation. The value and rate of mitotic index alterations decrease with a decrease of field strength. No changes were found in the frequency of aberrant mitoses or in the number of cells per one field of microscopic vison.  相似文献   
48.
49.
On the question of an electrokinetic requirement for phospholipase C action   总被引:1,自引:0,他引:1  
The phospholipase C of clostridium welchii (alpha toxin) has an absolute requirement for trace quantities of Ca2+. It attacks pure phosphatidylcholine particles (smectic mesophases) having a close-packed bilayer structure only when their surface zeta potential is made positive by the addition of certain divalent ions (e.g., Ca2+) to the aqueous phase or by the presence of low concentrations of long chain cations to the lipid. Alternatively, if the rotational freedom of individual phospholipid molecules is increased by the insertion of short n-alkanols (e.g., hexanol) into the bilayer or when a monolayer of the substrate at an air/water interface is expended, enzymic hydrolysis can occur without any requirement for a net postive charge on the surface.  相似文献   
50.
Over the last 2 years at Metropolitan Hospital Medical Center 245 diabetic women have been seen on the obstetric service. This complication of pregnancy comprises 7.9 per cent of 3,076 deliveries, resulting in an over-all uncorrected perinatal mortality rate of 2.9 per cent. We believe that early detection and strict rigid control of diabetes is the key to improved perinatal outcome. This article presents the classification, diagnosis, and management which have led to these results.  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