全文获取类型
收费全文 | 3311篇 |
免费 | 20篇 |
专业分类
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 |
出版年
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.
EM Stokely RW Parkey FJ Bonte KD Graham MJ Stone JT Willerson 《Canadian Metallurgical Quarterly》1976,120(2):433-434
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.
AD Cherrington JL Chiasson JE Liljenquist AS Jennings U Keller WW Lacy 《Canadian Metallurgical Quarterly》1976,58(6):1407-1418
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.
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.
CL Gugliucci MJ O''Sullivan W opperman M Gordon ML Stone 《Canadian Metallurgical Quarterly》1976,125(4):435-441
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