全文获取类型
收费全文 | 3909篇 |
免费 | 13篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 14篇 |
化学工业 | 247篇 |
金属工艺 | 26篇 |
机械仪表 | 29篇 |
建筑科学 | 29篇 |
矿业工程 | 5篇 |
能源动力 | 15篇 |
轻工业 | 54篇 |
水利工程 | 3篇 |
石油天然气 | 7篇 |
无线电 | 128篇 |
一般工业技术 | 249篇 |
冶金工业 | 2986篇 |
原子能技术 | 16篇 |
自动化技术 | 115篇 |
出版年
2020年 | 15篇 |
2019年 | 12篇 |
2017年 | 10篇 |
2016年 | 12篇 |
2014年 | 26篇 |
2013年 | 50篇 |
2012年 | 27篇 |
2011年 | 25篇 |
2010年 | 32篇 |
2009年 | 23篇 |
2008年 | 49篇 |
2007年 | 34篇 |
2006年 | 25篇 |
2005年 | 34篇 |
2004年 | 27篇 |
2003年 | 36篇 |
2002年 | 27篇 |
2001年 | 32篇 |
2000年 | 23篇 |
1999年 | 92篇 |
1998年 | 983篇 |
1997年 | 568篇 |
1996年 | 289篇 |
1995年 | 187篇 |
1994年 | 180篇 |
1993年 | 196篇 |
1992年 | 24篇 |
1991年 | 32篇 |
1990年 | 35篇 |
1989年 | 44篇 |
1988年 | 48篇 |
1987年 | 37篇 |
1986年 | 35篇 |
1985年 | 38篇 |
1984年 | 20篇 |
1983年 | 22篇 |
1982年 | 32篇 |
1981年 | 37篇 |
1980年 | 39篇 |
1979年 | 17篇 |
1978年 | 19篇 |
1977年 | 79篇 |
1976年 | 167篇 |
1975年 | 14篇 |
1974年 | 10篇 |
1973年 | 19篇 |
1972年 | 11篇 |
1971年 | 17篇 |
1970年 | 18篇 |
1967年 | 12篇 |
排序方式: 共有3923条查询结果,搜索用时 0 毫秒
41.
Androgen-induced gene activation in the rat prostate 总被引:1,自引:0,他引:1
42.
The lordosis response was regularly elicited from 24 of 31 intact, adult male hamsters, using manual somatosensory stimulation of the dorsal rear body. In these males there was no correlation between measures of male-typical behavior and lordosis. Castration had no effect on male lordosis duration scores even when intromissions were eliminated. Combined treatment with estradiol benzoate and progesterone significantly increased male lordosis duration scores. The body surface was mapped with a standardized brush stimulus. For eliciting lordosis, effectiveness of stimulation increased in an almost identical manner for hormone-primed males and females from the anterior to the posterior part of the body, with the stimulation of flanks, rump, and perineum the most effective. Within each skin zone, absolute effectiveness was greater in females than in males. Various types of somato-sensory stimulation were compared for their effectiveness in eliciting lordosis. Females were more responsive to these stimuli than males, even when males were hormonally primed. These behavioral data have implications for concepts of the neural organization of male- and female-typical mating responses existing within the same individual. 相似文献
43.
There is an early period of puberty in boys at the age of 10 to 13, accompanied by an increase in the level of follicle stimulating hormone and a low secretion of luteinizing hormone and testosterone, with no secondary sexual signs. The beginning of an increase in the luteinizing hormone and testosterone concentration in boys coincides with the development of secondary sexual signs. The stabilization of the level of luteinizing hormone takes place in boys already at the 2nd degree of the sexual development. The secretion of luteinizing hormone at this point corresponds already to the normal level in adult men. The level of testosterone in the blood continues to increase and does not reach its definitive level until after the age of 17, or at the 5th degree of sexual development. Like in boys, the increase of the follicle stimulating hormone in girls precedes the increase of the luteinizing hormone secretion. The beginning of the increase in the follicle stimulating hormone coincides with an increase in the level of estrogens and testosterone in the blood, and with the appearance of secondary signs of sexual maturation. The increase of the luteinizing hormone secretion takes place later in girls than in boys and is accompanied by a new and significant increase in the level of estrogens in the blood. At the 2nd degree of sexual development, the level of testosterone in the blood of girls is substantially higher than at the other stages. 相似文献
44.
Chordomas are uncommon tumors arising from embryonic remnats of the fetal notochord. The spheno-occipital and sacrococcygeal regions account for over 90 per cent of cases, the remaining 10 per cent occurring anywhere along the vertebral axis. A case of chordoma arising from the clivus is presented with a view to discussing management. The ability to obtain reasonable survival times associated with a useful and meaningful quality of life is emphasized. This may be accomplished by repeated, judicious surgical intervention with surprising ease and little morbidity to the patient in spite of its intracranial location. 相似文献
45.
EA Liberman AM Arzumanian MA Vladimirova LM Tsofina 《Canadian Metallurgical Quarterly》1976,21(3):476-481
"Zero-loop" of the molecular potential transformer of submitochondrial particles (SMP) is separated from the remaining electron transfer chain by rotenone, and its e.m.f. ET=0,003+RT/2F in [NADP X H] [NAD+]/[NADP+] [NAD X H] volts is used in the compensative method of measurement of the potential difference across the SMP membrane (delta USMP). The phospholipid membrane, measuring the concentration of the penetrating anions in the solution contained SMP, is used as "zero-indicators". This concentration drops monotonically with increase in delta USMP. Delta USMP is equal to ET when the addition of substrates of transhydrogenase reaction with definite ET does not change the potential across phospholipid membrane. 相似文献
46.
J R?sch CT Dotter AJ Seaman JM Porter HH Common 《Canadian Metallurgical Quarterly》1976,127(4):553-558
Sequential ascending venographic studies were used to assess the healing of deep venous thrombosis in 50 patients randomly assigned to streptokinase or heparin therapy. Various degrees of thrombolysis and/or recanalization were demonstrated by venograms performed on the fourth and tenth days of treatment. Late follow-up studies (mean, 7 months after treatment) showed three basic patterns of resolution: (1) return to normal, (2) complete recanalization, and (3) incomplete recanalization and/or collateralization. Loss of valves or their function was associated with recanalization. The character, speed, and outcome of healing reflected the nature and extent of thrombosis, prior thrombotic disease in the extremity, and the type and timing of treatment. Streptokinase was highly effective and preferable to heparin in patients with deep vein thrombosis when therapy was begun within 4 days of onset of symptoms. In later stages of acute or recurrent deep vein thrombosis, the effectiveness of both drugs was significantly reduced. 相似文献
47.
48.
Only one molecular weight species of DNA polymerase was found in different developmental stages of the eukaryotic microorganism Dictyostelium discoideum. The molecular weight of this DNA polymerase is estimated to be about 127 000 by sucrose gradient centrifugation. The enzyme is present in all stages of growth and development, including dormant spores. All DNA polymerase activity is lost upon incubation of the crude extract with N-ethylmaleimide. The reaction properties, molecular weight and N-ethylmaleimide sensitivity of the D. discoideum DNA polymerase are similar to those of the DNA polymerase-alpha from mammalian sources. 相似文献
49.
A case of transient filling defects in the renal pelves and ureters, secondary to spontaneously occurring acquired anticoagulants, is presented. The relationship of this entity to hemophilia, immunologic disorders, such as systemic lupus erythematosis, and normal post partum patients is discussed. The differential diagnosis for filling defects in the renal pelvis is reviewed. 相似文献
50.