全文获取类型
收费全文 | 11095篇 |
免费 | 865篇 |
国内免费 | 428篇 |
专业分类
12388篇 |
出版年
2024年 | 23篇 |
2023年 | 91篇 |
2022年 | 253篇 |
2021年 | 438篇 |
2020年 | 299篇 |
2019年 | 322篇 |
2018年 | 358篇 |
2017年 | 296篇 |
2016年 | 442篇 |
2015年 | 655篇 |
2014年 | 719篇 |
2013年 | 850篇 |
2012年 | 971篇 |
2011年 | 872篇 |
2010年 | 569篇 |
2009年 | 441篇 |
2008年 | 581篇 |
2007年 | 509篇 |
2006年 | 480篇 |
2005年 | 412篇 |
2004年 | 348篇 |
2003年 | 294篇 |
2002年 | 294篇 |
2001年 | 186篇 |
2000年 | 198篇 |
1999年 | 151篇 |
1998年 | 98篇 |
1997年 | 89篇 |
1996年 | 85篇 |
1995年 | 66篇 |
1994年 | 68篇 |
1993年 | 53篇 |
1992年 | 92篇 |
1991年 | 78篇 |
1990年 | 80篇 |
1989年 | 66篇 |
1988年 | 50篇 |
1987年 | 74篇 |
1986年 | 48篇 |
1985年 | 39篇 |
1984年 | 37篇 |
1983年 | 24篇 |
1982年 | 25篇 |
1980年 | 24篇 |
1979年 | 27篇 |
1978年 | 24篇 |
1977年 | 24篇 |
1975年 | 19篇 |
1973年 | 21篇 |
1972年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
13.
14.
15.
José A. A. Sant''Ana Pereira Arnold De Haan Andy Wessels Antoon F. M. Moorman Anthony J. Sargeant 《The Histochemical journal》1995,27(9):715-722
Summary In the present study we report a novel histochemical method which, by sequential pre-incubations in alkaline and acidic media,
selectively differentiates muscle fibres expressing myosin heavy chain IIX, on the basis of a specific profile for myofibrillar
actomyosin ATPase (mATPase) activity. The enzyme reactions were tested for specificity by means of anti-myosin heavy chain
monoclonal antibodies, which were characterized on Western blots of muscle homogenates. Enzyme histochemical reactions with
the traditional pH buffers were compared to those of the new method and, in conjunction with the immunoreactions, used to
confirm the relationship between MyHC expression and the distinct profiles for mATPase. Imrnunohistochemical reactions demonstrated
that the new method only differentiates those fibres expressing myosin heavy chain IIX. The method revealed a continuum in
which the intermediate staining intensities corresponded to hybrid fibres expressing myosin heavy chain IIX in combination
with either the IIA or IIB forms. Quantitative histochemistry and immunohistochemistry (by image analysis), used to examine
the relationship between staining intensities for mATPase and amounts of myosin heavy chain IIX expression, revealed that
the new method discriminates well between hybrid fibres expressing variable amounts of the IIX isoform (r2 = 0.93). 相似文献
16.
17.
Lasse Ryhänen Elaine M.L. Tan Sirpa Rantala-Ryhänen Jouni Uitto 《Archives of biochemistry and biophysics》1982,215(1):230-236
Chick embryo sterna, which actively synthesize type II procollagen, were pulse-labeled with radioactive proline; protein synthesis was then inhibited by unlabeled proline and cycloheximide. After the inhibition of protein synthesis, several amino acids, polyamines, or structurally related compounds were added to the incubation medium. The conversion of procollagen, first to two intermediates, pC-collagen and pN-collagen, and then to collagen, was monitored by sodium dodecyl sulfate-polyacrylamide slab gel electrophoresis. The addition of 50 mm β-alanine, arginine, asparagine, glutamine, hydroxylysine, lysine, or ornithine, as well as agmatine, ?-aminocaproic acid, S-2-aminoethylcysteine, cadaverine, canavanine, putrescine, or spermine clearly inhibited the removal of the carboxy-terminal extension and pC-collagen accumulated; the removal of the amino-terminal extension was not affected. The inhibition of the conversion was reversible and unaffected by fetal calf serum. The results suggest that the conversion of type II procollagen to collagen requires at least two separate proteinases for the removal of amino-terminal and carboxy-terminal extensions. The results further suggest that naturally occurring molecules may be used to modulate the rate of conversion of procollagen to collagen, and development of analogs of these compounds may provide the means to interfere with excessive deposition of collagen in diseases with tissue fibrosis. 相似文献
18.
The chemical identity of the immunoreactive LHRH-like peptide biosynthesized in the human placenta 总被引:5,自引:0,他引:5
Freshly obtained human placental trophoblasts were minced and pulselabeled for 30 min at 37°C with tritiated L-Tyrosine. After homogenisation, the crude extract was centrifuged and deproteinized with 10% TCA. The supernatant was defatted and the peptides concentrated through hydrophobic binding on ODS-silica cartridges. The bound, crude peptide extract was eluted and subjected to gradient, reverse-phase High Performance Liquid Chromatography. The fractions corresponding to the absorption peak of reference, synthetic LHRH were collected and extensively purified to radioactive homogeneity by further multiple HPLC. After digestion with pyroglutamate aminopeptidase, the resulting nonapeptide was manually sequenced by dansyl-Edman degradation. All the incorporated radioactivity was found to reside exclusively in residue number 4 of the nonapeptide; thus establishing for the first time the primary sequence of biosynthetic placental LHRH as: pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2, identical to its hypothalamic counterpart. 相似文献
19.
20.