全文获取类型
收费全文 | 9563篇 |
免费 | 867篇 |
国内免费 | 14篇 |
专业分类
10444篇 |
出版年
2023年 | 40篇 |
2022年 | 105篇 |
2021年 | 225篇 |
2020年 | 118篇 |
2019年 | 146篇 |
2018年 | 172篇 |
2017年 | 151篇 |
2016年 | 264篇 |
2015年 | 439篇 |
2014年 | 453篇 |
2013年 | 588篇 |
2012年 | 765篇 |
2011年 | 682篇 |
2010年 | 440篇 |
2009年 | 462篇 |
2008年 | 597篇 |
2007年 | 544篇 |
2006年 | 544篇 |
2005年 | 477篇 |
2004年 | 477篇 |
2003年 | 458篇 |
2002年 | 407篇 |
2001年 | 131篇 |
2000年 | 111篇 |
1999年 | 109篇 |
1998年 | 98篇 |
1997年 | 63篇 |
1996年 | 62篇 |
1995年 | 56篇 |
1994年 | 65篇 |
1993年 | 58篇 |
1992年 | 79篇 |
1991年 | 61篇 |
1990年 | 61篇 |
1989年 | 66篇 |
1988年 | 57篇 |
1987年 | 46篇 |
1986年 | 47篇 |
1985年 | 37篇 |
1984年 | 48篇 |
1983年 | 54篇 |
1982年 | 34篇 |
1981年 | 43篇 |
1980年 | 40篇 |
1979年 | 55篇 |
1977年 | 32篇 |
1976年 | 36篇 |
1975年 | 32篇 |
1974年 | 37篇 |
1973年 | 30篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
51.
Levator advancement technique for eyelid ptosis 总被引:1,自引:0,他引:1
There have been many procedures advocated for the treatment of eyelid ptosis. The technique advocated in this paper consists of careful dissection and identification of anatomic landmarks, including preaponeurotic fat, Whitnall's superior transverse ligament, and the vertically oriented blood supply of the levator muscle. The attachment of the levator muscle into the cephalad portion of the levator muscle into the cephalad portion of the levator aponeurosis can be identified and easily dissected in order to perform the procedure of detachment and advancement to the tarsal plate. This procedure for ptosis has been successful in management in moderate to severe ptosis and in some cases has actually increased the muscle function, thereby enhancing the result. In this technique, the full length of levator muscle remains, so maximum excursion is achieved postoperatively. In addition, this surgical approach may be utilized for levator-lengthening procedures in cases of thyroid exophthalmus or overcorrected ptosis simply by performing the reverse procedure of detachment and insertion of a spacer based on the same ratio. Good results have been achieved in over 20 patients, with the exception of two patients who had absent to poor function and in whom undercorrection was present postoperatively. 相似文献
52.
53.
54.
55.
56.
Vincent Marks Denys Fry P. A. L. Chapple Geoffrey Gray 《BMJ (Clinical research ed.)》1969,2(5650):153-155
Experience with urine analysis for morphine using thin-layer chromatography in 310 cases of real or possible heroin abuse showed that it was valuable not only in detecting improper drug use but also in monitoring treatment. The results of this test can be available routinely in 24, and exceptionally in five hours. A negative result implies that the subject has taken less than 10 mg. of heroin in the past 24 hours. 相似文献
57.
P. C. Vincent G. Borner A. D. Chanana E. P. Cronkite M. L. Greenberg D. D. Joel L. M. Schiffer P. A. Stryckmans 《Cell proliferation》1969,2(3):235-247
Some of the time parameters of the cell cycle in bovine thoracic duct lymphocytes have been estimated by analysing labeled mitoses curves, and by double labeling. The two methods gave similar estimates of Ts. Thus, Ts measured directly from labeled mitoses curves varied from 4 to 6 hr, while the estimates from double labeling were 4.8 and 4.5 hr. T G measured directly from labeled mitoses curves was 5 hr, and estimates of TG from the values of Ts ranged from 6.3 to 7.7 hr. The present data confirm the short generative cycle of large thoracic duct lymphocytes. Extracorporeal irradiation of the lymph (ECIL) had no detectable effect on the cell cycle or the fractional production rate of the lymphocytes. However, the calculated absolute production was reduced following ECIL, due to a decrease in the absolute number of cells present. The grain count over mitoses after ECIL was approximately one-half that found before ECIL. 相似文献
58.
59.
Studies of the toxicity of 2,4,5,6-tetrachloroisophthalonitrile (TCIN) to cells of Saccharomyces pastorianus and Neurospora crassa showed that 2 to 4 μg/ml of the toxicant were required to inhibit growth. Several thiol compounds reversed toxicity to growth. Glucose oxidation was severely impaired in treated cells of both test organisms. The toxicant at 2 or 4 μg/ml markedly reduced soluble thiol content of these cells. Bound thiol content was less affected in S. pastorianus cells than soluble thiol content. Uptake of toxicant by yeast cells was accompanied by formation of derivatives, some of which resembled those formed by reaction of glutathione with TCIN in vitro. Coenzyme A, glutathione, and 2-mercaptoethanol readily formed derivatives with TCIN in vitro. The nature of these derivatives was studied using 2-mercaptoethanol products as model substituents. Four derivatives were formed with 2-mercaptoethanol each with similar functional groups but showing dissimilar degrees of mobility during silica gel chromatography. Evidence indicated that these are derivatives of TCIN in which 1 to 4 of the halogens has been substituted by 2-mercaptoethanol. The mechanism of fungicidal action of TCIN is attributed to thiol inactivation. 相似文献
60.
On primary infection with the Bryan strain of Rous sarcoma virus (RSV), the growth curve of the virus in the brain of Japanese quail was similar to that observed in chicks and turkey poults. Infectious virus disappeared from the brain after inoculation. After an eclipse period during which no virus was detectable, infectious virus began to appear at 2 days and reached maximal titers in the brain samples at 7 days after inoculation. When Japanese quail were infected intracerebrally with RSV, relatively high titers of virus were recovered from brain tissue but not from liver, lung, kidney, or blood of moribund birds. Only tumors produced in the wing web of quail infected subcutaneously yielded high titers of virus. Other tissues yielded no virus, even though wing web tumors appeared as early as in chicks similarly infected. RSV could be propagated in the wing web of quail for at least 14 passages without any loss of infectivity. On the other hand, serial passage in quail brain resulted in a progressive loss of infectivity until virus was completely lost. 相似文献