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   145073篇
  免费   8470篇
  国内免费   3325篇
耳鼻咽喉   903篇
儿科学   3806篇
妇产科学   3025篇
基础医学   12948篇
口腔科学   3368篇
临床医学   14999篇
内科学   23057篇
皮肤病学   1445篇
神经病学   7669篇
特种医学   4174篇
外国民族医学   25篇
外科学   15117篇
综合类   23360篇
现状与发展   12篇
一般理论   8篇
预防医学   12326篇
眼科学   2211篇
药学   11030篇
  215篇
中国医学   10767篇
肿瘤学   6403篇
  2023年   2257篇
  2022年   4063篇
  2021年   5715篇
  2020年   5262篇
  2019年   6563篇
  2018年   5554篇
  2017年   4869篇
  2016年   4270篇
  2015年   3786篇
  2014年   7961篇
  2013年   7616篇
  2012年   7091篇
  2011年   8278篇
  2010年   7014篇
  2009年   5928篇
  2008年   5638篇
  2007年   6007篇
  2006年   5474篇
  2005年   4660篇
  2004年   3930篇
  2003年   3497篇
  2002年   2661篇
  2001年   2369篇
  2000年   1882篇
  1999年   1631篇
  1998年   1351篇
  1997年   1306篇
  1996年   1138篇
  1995年   1102篇
  1994年   1017篇
  1993年   847篇
  1992年   766篇
  1991年   690篇
  1990年   588篇
  1989年   533篇
  1988年   558篇
  1987年   462篇
  1985年   1989篇
  1984年   2907篇
  1983年   2614篇
  1982年   2083篇
  1981年   2166篇
  1980年   1833篇
  1979年   1622篇
  1978年   1386篇
  1977年   879篇
  1976年   1270篇
  1975年   1078篇
  1974年   898篇
  1973年   840篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Temperature-sensitive mutants of reovirus type 3 are capable of interfering with the replication of wild-type reovirus type 3. The interfering activity correlated with the ability of pairs of mutants to complement at 39°: Pairs of noninterfering mutants (tsD × tsE) yielded efficient complementation (indexes of 10–50); pairs of interfering mutants (including members of groups ts A, B, G) did not produce significant complementation (indexes ~ 1). The ability of pairs of mutants to reassort at 39° generally followed a similar pattern. Thus interference is an important property of ts mutants of reovirus and needs to be considered when genetic interactions are being studied at 39°.  相似文献   
992.
To record the hysteresis loop and electromyogram of the diaphragm simultaneously it is recommended that a standard probe of the sort used to record the intraesophageal pressure, on which silver electrodes are mounted, be used. This method provides fuller information on the work of the respiratory muscles.Institute of Obstetrics and Gynecology, Academy of Medical Sciences of the USSR, Leningrad. (Presented by Academician of the Academy of Medical Sciences of the USSR V. G. Baranov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 85, No. 1, pp. 95–96, January, 1978.  相似文献   
993.
Direct correlation was found in intact rats between the kallikrein activity of the urine, on the one hand, and the diuresis, sodium excretion, and ability of the kidneys to concentrate the urine on the other hand. Small doses of indomethacin (2 mg/kg for 5 days) increased the kallikrein activity of the urine four-fold and, at the same time, increased the diuresis; large doses (5 mg/kg for 5 days) lowered the kallikrein activity of the urine and halved the diuresis, reduced the sodium excretion by two-thirds, and depressed the ability of the kidneys to concentrate the urine. Indomethacin may perhaps modify the synthesis not only of prostaglandins, but also of kallikrein, and this is reflected in the state of the kidney function.All-Union Cardiological Scientific Center, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR E. I. Chazor.) Translated from Byulleten' Éxperimental'noi Biologii i Meditsiny, Vol. 83, No. 4, pp. 399–400, April, 1977.  相似文献   
994.
采用放免法检测甲状豚疾病患者抗甲状腺球蛋白抗体(TGAb)和抗甲状腺过氧化物酶抗体(TPOAb)、并对部分Graves病患者停药后随诊一年的结果进行分析。结果显示:(1)自身免疫性甲状腺疾病患者TGAb和TPOAb活性及阳性率明显高于非AITD,尤以桥本甲状腺炎为然。(2)GD治疗前及停药时TGAb和TPOAb均阴性者与均阳性者停药一年内的复发率分别为0.583和0.231。(3)TGAb和TPOAb均阴性,而停药时甲状腺刺激抗体(TSAb)阳性者,停药时GD复发的机率最大(0.909),提示TGAb和TPOAb检测在AITD诊断,鉴别诊断以及GD预后判断中具有重要的临床意义。  相似文献   
995.
Chorionic Villous Biopsy (CVS) for diagnosis of XLP was undertaken at 10 weeks gestation in an obligate carrier. The fetus was found to be male by cytogenetic analysis. XLP (Xq25-q26) is closely linked to the RFLP markers DXS10, DXS37 and DXS42, but only DXS10 (distal to XLP) was informative for prenatal diagnosis in this family. RFLP analysis using this marker gave a 7% risk that the fetus was affected, based on the known recombination frequency between DXS10 and XLP. Further investigation was then undertaken to obtain a rapid and more accurate diagnosis using the three highly polymorphic PCR based markers. These were the AC repeat markers DXS424 (XL5A) and DXS425 (XL90A3) and the tetramer repeat marker within HPRT. DX425 is approximately 10 cM proximal to DXS10 and HPRT but is not known with certainty to map proximal or distal to XLP. DXS424 is proximal to DXS10 and HPRT and was inferred to be proximal to XLP on the basis of map distance from HPRT estimated by linkage analysis of data from CEPH pedigrees. This was confirmed by a recombinant in the XLP family between DXS424 and DXS425, placing DXS424 proximal to XLP. Diagnosis by linkage using DXS424 and DXS425, at least one of which is proximal to XLP, and distal markers DXS10 and HPRT, increased the accuracy of diagnosis using flanking marker analysis to greater than 99% that the fetus was unaffected. HLA DR typing of the CVS showed that the fetus was DR identical to a male sibling with XLP. HLA compatibility was confirmed at delivery by full HLA typing and MLC.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
996.
Nagy E  Dobos P 《Virology》1984,137(1):58-66
Both dsRNA genome segments of Drosophila X virus (DXV) were denatured and translated in vitro using nuclease-treated rabbit reticulocyte lysates. The synthesis of all four primary gene products was detected by polyacrylamide gel electrophoresis and autoradiography. Genome segment A (mol wt 2.3 X 10(6)) encoded polypeptides with molecular weights of 67,000 (67K), 34K, and 27K, whereas segment B (mol wt 22 X 10(6)) encoded the 110K polypeptide. The proteolytic processing of 67K which generates a 49K polypeptide in infected cells was also observed in vitro. Pulse-chase experiments indicated that synthesis of the three polypeptides encoded by genome segment A initiated independently and simultaneously, suggesting that segment A is polycistronic. Native (undenatured) DXV dsRNA could also be translated with high fidelity (vitro). The messenger activity of native dsRNA was abolished by S1 nuclease treatment but completely restored on subsequent denaturation. In vitro "pulse-chase" experiments using native dsRNA as messenger, indicated that the order of translation of polypeptides on genome segment A was 5'-67K-27K-34K-3'.  相似文献   
997.
为建立早期胚胎活检的动物模型,以安全高效地开展人类的植入前遗传学诊断,应用显微操作技术,对发育到8细胞期的小鼠胚胎进行了透明带溶洞吸取单个卵裂球的研究。结果表明:简化组的胚胎活检时间显著缩短,而胚胎完整率及单个卵裂球的完整率与传统组无明显差别。对照和两实验组胚胎在体外培养过程中均出现不同程度的胚胎发育延迟现象。活检后胚胎桑椹胚的发育率较对照组显著降低,但三组胚胎的出生率和生后三周仔鼠的体重无显著性差别,提示简化组的胚胎活检是安全而高效的,因而为开展人类的早期胚胎活检提供了方法学的参考。  相似文献   
998.
Complete nucleotide sequence of the M RNA segment of Rift Valley fever virus   总被引:12,自引:0,他引:12  
The entire M RNA segment of the phlebovirus Rift Valley fever virus (RVFV) has been molecularly cloned and the complete nucleotide sequence determined. The RNA is 3884 nucleotides in length, corresponding to a molecular weight of 1.38 X 10(6), having a base composition of 27.3% A, 25.4% G, 27.2% U, and 20.1% C. Sequences present at the 3' and 5' termini of the molecule are largely complementary for some 51 residues and can form a stable duplex structure when the potential secondary structure of the entire molecule is considered. A single major open reading frame, capable of encoding 1206 amino acids (131,845 Da), was found in the viral-complementary sequence ("positive" polarity). Amino-terminal amino acid sequencing of the purified viral glycoproteins G1 and G2 allowed for the positioning of the coding sequences for these polypeptides within this major open reading frame in the following orientation with respect to the genomic M RNA: 3'-G2-G1-5'. From the predicted amino acid composition of the two mature viral glycoproteins, both were found to have a high cysteine content (G2, 6%; G1, 5%). Sequences within the open reading frame capable of encoding up to 23,000 Da of polypeptide were found in addition to those required for the viral glycoproteins. The potential contribution of these sequences to the coding capacity of the M RNA, viral protein processing, and intracellular protein distribution is discussed.  相似文献   
999.
The karyotypic evolution of three chemically induced cell lines of Syrian hamster embryo in culture are described. The only karyotypic alteration of one clone was a trisomy of chromosome #11, which presumably arose by nondisjunction after carcinogen treatment. A pure population of cells with the trisomy was observed repeatedly upon karyotyping of cells at the first three passages after cloning. However, at a late passage, apparently normal diploid cells appeared in the culture, which we propose resulted from a second nondisjunction of one chromosome #11, reverting the cells from trisomy 11 to disomy 11. The karyotypic evolution of two other cell lines also involved double nondisjunction, which resulted in duplication of a translocated chromosome and concurrent loss of the normal nonrearranged chromosome. Taken together with the reported findings of others, the results indicate that double nondisjunction is a mechanism in karyotypic progression during neoplastic development.  相似文献   
1000.
Renal carcinoma developed in two or more members of nine families. Multiple generations were affected in five kindreds, and siblings in four. The median age at cancer diagnosis was a decade earlier than usual, and individual patients had bilateral or multifocal lesions; these are features of hereditary forms of diverse cancers. No patient had von Hippel-Lindau disease or other predisposing genetic syndromes. Karyotypes of the peripheral blood of nine persons showed no instance of a 3;8 chromosome translocation as recently reported in association with renal carcinoma in ten members of one family. The findings show that familial renal cancer is more common than previously reported in the literature.  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